Kinetic study of dry anaerobic co-digestion of food waste and cardboard for methane production.

PubMed

Capson-Tojo, Gabriel; Rouez, Maxime; Crest, Marion; Trably, Eric; Steyer, Jean-Philippe; Bernet, Nicolas; Delgenès, Jean-Philippe; Escudié, Renaud

2017-11-01

Dry anaerobic digestion is a promising option for food waste treatment and valorization. However, accumulation of ammonia and volatile fatty acids often occurs, leading to inefficient processes and digestion failure. Co-digestion with cardboard may be a solution to overcome this problem. The effect of the initial substrate to inoculum ratio (0.25 to 1gVS·gVS -1 ) and the initial total solids contents (20-30%) on the kinetics and performance of dry food waste mono-digestion and co-digestion with cardboard was investigated in batch tests. All the conditions produced methane efficiently (71-93% of the biochemical methane potential). However, due to lack of methanogenic activity, volatile fatty acids accumulated at the beginning of the digestion and lag phases in the methane production were observed. At increasing substrate to inoculum ratios, the initial acid accumulation was more pronounced and lower cumulative methane yields were obtained. Higher amounts of soluble organic matter remained undegraded at higher substrate loads. Although causing slightly longer lag phases, high initial total solids contents did not jeopardize the methane yields. Cardboard addition reduced acid accumulation and the decline in the yields at increasing substrate loads. However, cardboard addition also caused higher concentrations of propionic acid, which appeared as the most last acid to be degraded. Nevertheless, dry co-digestion of food waste and cardboard in urban areas is demonstrated asan interesting feasible valorization option. Copyright © 2017 Elsevier Ltd. All rights reserved.

Methanosarcina plays a main role during methanogenesis of high-solids food waste and cardboard.

PubMed

Capson-Tojo, Gabriel; Trably, Eric; Rouez, Maxime; Crest, Marion; Bernet, Nicolas; Steyer, Jean-Philippe; Delgenès, Jean-Philippe; Escudié, Renaud

2018-04-07

Anaerobic digestion of food waste is a complex process often hindered by high concentrations of volatile fatty acids and ammonia. Methanogenic archaea are more sensitive to these inhibitors than bacteria and thus the structure of their community is critical to avoid reactor acidification. In this study, the performances of three different inocula were compared using batch digestion tests of food waste and cardboard mixtures. Particular attention was paid to the archaeal communities in the inocula and after digestion. While the tests started with inocula rich in Methanosarcina led to efficient methane production, VFAs accumulated in the reactors where inocula initially were poor in this archaea and no methane was produced. In addition, higher substrate loads were tolerated when greater proportions of Methanosarcina were initially present in the inoculum. Independently of the inoculum origin, Methanosarcina were the dominant methanogens in the digestates from the experiments that efficiently produced methane. These results suggest that the initial archaeal composition of the inoculum is crucial during reactor start-up to achieve stable anaerobic digestion at high concentrations of ammonia and organic acids. Copyright © 2018 Elsevier Ltd. All rights reserved.

High-resolution chemical and hydrologic records identify environmental factors that control coastal anchialine cave ecosystem function

NASA Astrophysics Data System (ADS)

Brankovits, D.; Pohlman, J.; Lapham, L.; Casso, M.; Roth, E.; Lowell, N. S.; Iliffe, T. M.

2015-12-01

Anchialine caves host a coastal aquifer ecosystem occupied by cave-adapted crustaceans that reside within distinct fresh, brackish and marine waters. Our initial investigation of this subsurface ecotone in the Yucatan Peninsula (Mexico) provides stable isotope-based evidence that methane and dissolved organic carbon (DOC) are the primary sources of energy and carbon for the food web. However, the frequency of observations is sparse, leaving us 'in the dark' with respect to the temporal dynamics of the ecosystem function. In this study, we obtained undisturbed vertical profiles of methane, DOC and DIC concentration and isotopic composition with the 'Octopipi' water sampler from an anchialine cave located ~8 km from the coastline. To document the temporal variability of methane availability in the cave, we deployed an osmotically-driven pump (OsmoSampler). Data loggers recorded dissolved oxygen (DO), salinity, temperature and current velocities, and a rain gauge recorded precipitation. A high-methane water mass near the ceiling (up to 7795 nM) contained elevated concentration (900 µM), 13C-depleted (-27.8 to -28.2 ‰) DOC, suggesting terrestrial organic matter input from the overlying soils. Low-methane saline water (36 to 84 nM) had lower concentration DOC (15 to 97 µM) with a similar δ13C (-25.9 to -27.2 ‰), suggesting significant terrestrial organic matter consumption or removal with increasing depth, from fresh to saline water, within the water column. Our 6-month water chemistry record reveals high concentrations of methane in the wet season, especially following rainfall events, and relatively lower methane concentrations in the dry season. These observations suggest rain flushes methane generated in overlying anoxic soils into the cave. DO, water level, and groundwater flow patterns were also linked to the precipitation record. These data provide novel insight into the interconnections between external climate forcing and subterranean anchialine ecosystems within coastal aquifers.

Factors that control the stable carbon isotopic composition of methane produced in an anoxic marine sediment

NASA Technical Reports Server (NTRS)

Alperin, M. J.; Blair, Neal E.; Albert, D. B.; Hoehler, T. M.; Martens, C. S.

1993-01-01

The carbon isotopic composition of methane produced in anoxic marine sediment is controlled by four factors: (1) the pathway of methane formation, (2) the isotopic composition of the methanogenic precursors, (3) the isotope fractionation factors for methane production, and (4) the isotope fractionation associated with methane oxidation. The importance of each factor was evaluated by monitoring stable carbon isotope ratios in methane produced by a sediment microcosm. Methane did not accumulate during the initial 42-day period when sediment contained sulfate, indicating little methane production from 'noncompetitive' substrates. Following sulfate depletion, methane accumulation proceeded in three distinct phases. First, CO2 reduction was the dominant methanogenic pathway and the isotopic composition of the methane produced ranged from -80 to -94 per thousand. The acetate concentration increased during this phase, suggesting that acetoclastic methanogenic bacteria were unable to keep pace with acetate production. Second, acetate fermentation became the dominant methanogenic pathway as bacteria responded to elevated acetate concentrations. The methane produced during this phase was progressively enriched in C-13, reaching a maximum delta(C-13) value of -42 per thousand. Third, the acetate pool experienced a precipitous decline from greater than 5 mM to less than 20 micro-M and methane production was again dominated by CO2 reduction. The delta(C-13) of methane produced during this final phase ranged from -46 to -58 per thousand. Methane oxidation concurrent with methane production was detected throughout the period of methane accumulation, at rates equivalent to 1 to 8 percent of the gross methane production rate. Thus methane oxidation was too slow to have significantly modified the isotopic signature of methane. A comparison of microcosm and field data suggests that similar microbial interactions may control seasonal variability in the isotopic composition of methane emitted from undisturbed Cape Lookout Bight sediment.

Coal-Packed Methane Biofilter for Mitigation of Green House Gas Emissions from Coal Mine Ventilation Air

PubMed Central

Limbri, Hendy; Gunawan, Cindy; Thomas, Torsten; Smith, Andrew; Scott, Jason; Rosche, Bettina

2014-01-01

Methane emitted by coal mine ventilation air (MVA) is a significant greenhouse gas. A mitigation strategy is the oxidation of methane to carbon dioxide, which is approximately twenty-one times less effective at global warming than methane on a mass-basis. The low non-combustible methane concentrations at high MVA flow rates call for a catalytic strategy of oxidation. A laboratory-scale coal-packed biofilter was designed and partially removed methane from humidified air at flow rates between 0.2 and 2.4 L min−1 at 30°C with nutrient solution added every three days. Methane oxidation was catalysed by a complex community of naturally-occurring microorganisms, with the most abundant member being identified by 16S rRNA gene sequence as belonging to the methanotrophic genus Methylocystis. Additional inoculation with a laboratory-grown culture of Methylosinus sporium, as investigated in a parallel run, only enhanced methane consumption during the initial 12 weeks. The greatest level of methane removal of 27.2±0.66 g methane m−3 empty bed h−1 was attained for the non-inoculated system, which was equivalent to removing 19.7±2.9% methane from an inlet concentration of 1% v/v at an inlet gas flow rate of 1.6 L min−1 (2.4 min empty bed residence time). These results show that low-cost coal packing holds promising potential as a suitable growth surface and contains methanotrophic microorganisms for the catalytic oxidative removal of methane. PMID:24743729

Methane excess production in oxygen-rich polar water and a model of cellular conditions for this paradox

NASA Astrophysics Data System (ADS)

Damm, E.; Thoms, S.; Beszczynska-Möller, A.; Nöthig, E. M.; Kattner, G.

2015-09-01

Summer sea ice cover in the Arctic Ocean has undergone a reduction in the last decade exposing the sea surface to unforeseen environmental changes. Melting sea ice increases water stratification and induces nutrient limitation, which is also known to play a crucial role in methane formation in oxygenated surface water. We report on an excess of methane in the marginal ice zone in the western Fram Strait. Our study is based on measurements of oxygen, methane, DMSP, nitrate and phosphate concentrations as well as on phytoplankton composition and light transmission, conducted along the 79°N oceanographic transect, in the western part of the Fram Strait and in Northeast Water Polynya region off Greenland. Between the eastern Fram Strait, where Atlantic water enters from the south and the western Fram Strait, where Polar water enters from the north, different nutrient limitations occurred and consequently different bloom conditions were established. Ongoing sea ice melting enhances the environmental differences between both water masses and initiates regenerated production in the western Fram Strait. We show that in this region methane is in situ produced while DMSP (dimethylsulfoniopropionate) released from sea ice may serve as a precursor for the methane formation. The methane production occured despite high oxygen concentrations in this water masses. As the metabolic activity (respiration) of unicellular organisms explains the presence of anaerobic conditions in the cellular environment we present a theoretical model which explains the maintenance of anaerobic conditions for methane formation inside bacterial cells, despite enhanced oxygen concentrations in the environment.

Methane Sources and Migration Mechanisms in Shallow Groundwaters in Parker and Hood Counties, Texas-A Heavy Noble Gas Analysis.

PubMed

Wen, Tao; Castro, M Clara; Nicot, Jean-Philippe; Hall, Chris M; Larson, Toti; Mickler, Patrick; Darvari, Roxana

2016-11-01

This study places constraints on the source and transport mechanisms of methane found in groundwater within the Barnett Shale footprint in Texas using dissolved noble gases, with particular emphasis on 84 Kr and 132 Xe. Dissolved methane concentrations are positively correlated with crustal 4 He, 21 Ne, and 40 Ar and suggest that noble gases and methane originate from common sedimentary strata, likely the Strawn Group. In contrast to most samples, four water wells with the highest dissolved methane concentrations unequivocally show strong depletion of all atmospheric noble gases ( 20 Ne, 36 Ar, 84 Kr, 132 Xe) with respect to air-saturated water (ASW). This is consistent with predicted noble gas concentrations in a water phase in contact with a gas phase with initial ASW composition at 18 °C-25 °C and it suggests an in situ, highly localized gas source. All of these four water wells tap into the Strawn Group and it is likely that small gas accumulations known to be present in the shallow subsurface were reached. Additionally, lack of correlation of 84 Kr/ 36 Ar and 132 Xe/ 36 Ar fractionation levels along with 4 He/ 20 Ne with distance to the nearest gas production wells does not support the notion that methane present in these groundwaters migrated from nearby production wells either conventional or using hydraulic fracturing techniques.

Heterogeneous Nucleation of Methane Hydrate in a Water-Decane-Methane Emulsion

NASA Astrophysics Data System (ADS)

Shestakov, V. A.; Kosyakov, V. I.; Manakov, A. Yu.; Stoporev, A. S.; Grachev, E. V.

2018-07-01

Heterogeneous nucleation in disperse systems with metastable disperse phases plays an important role in the mechanisms of environmental and technological processes. The effect the concentration and activity of particles that initiate the formation of a new phase have on nucleation processes in such systems is considered. An approach is proposed that allows construction of a spectrum of particle activity characterizing the features of nucleation in a sample, based on the fraction of crystallized droplets depending on the level of supercooling and the use of Weibull's distribution. The proposed method is used to describe experimental data on the heterogeneous nucleation of methane hydrate in an emulsion in a water-decane-methane system.

Comparison of anaerobic digestion characteristics and kinetics of four livestock manures with different substrate concentrations.

PubMed

Li, Kun; Liu, Ronghou; Sun, Chen

2015-12-01

Anaerobic digestions of pig manure (PM), dairy manure (DM), chicken manure (CM) and rabbit manure (RM) at initial volatile solid loading (VSL) of 8 g VS/L, 16 g VS/L, 32 g VS/L, 64 g VS/L were investigated under mesophilic conditions. The maximum methane yields of 410, 270, 377 and 323 mL CH4/g VSadded for PM, DM, CM and RM were all obtained at initial VSL of 8 g VS/L, respectively. The improvement of substrate concentration to 64 g VS/L not only decreased the methane yield and biodegradability both by 22.4%, 37.3%, 49.1% and 34.6% for PM, DM, CM and RM respectively, but also reduced the methane content in final biogas production. The Cone model (R(2): 0.9910-0.9974) showed a better fit to the experiment data and the calculated parameters indicated that anaerobic digestion of manures at higher loading has longer lag phase and lower hydrolysis rate. Copyright © 2015 Elsevier Ltd. All rights reserved.

Occurrence of methane in groundwater of south-central New York State, 2012-systematic evaluation of a glaciated region by hydrogeologic setting

USGS Publications Warehouse

Heisig, Paul M.; Scott, Tia-Marie

2013-01-01

A survey of methane in groundwater was undertaken to document methane occurrence on the basis hydrogeologic setting within a glaciated 1,810-square-mile area of south-central New York along the Pennsylvania border. Sixty-six wells were sampled during the summer of 2012. All wells were at least 1 mile from any known gas well (active, exploratory, or abandoned). Results indicate strong positive and negative associations between hydrogeologic settings and methane occurrence. The hydrogeologic setting classes are based on topographic position (valley and upland), confinement or non-confinement of groundwater by glacial deposits, well completion in fractured bedrock or sand and gravel, and hydrogeologic subcategories. Only domestic wells and similar purposed supply wells with well-construction and log information were selected for classification. Field water-quality characteristics (pH, specific conductance, dissolved oxygen, and temperature) were measured at each well, and samples were collected and analyzed for dissolved gases, including methane and short-chain hydrocarbons. Carbon and hydrogen isotopic ratios of methane were measured in 21 samples that had at least 0.3 milligram per liter (mg/L) of methane. Results of sampling indicate that occurrence of methane in groundwater of the region is common—greater than or equal to 0.001 mg/L in 78 percent of the groundwater samples. Concentrations of methane ranged over five orders of magnitude. Methane concentrations at which monitoring or mitigation are indicated (greater than or equal to 10 mg/L) were measured in 15 percent of the samples. Methane concentrations greater than 0.1 mg/L were associated with specific hydrogeologic settings. Wells completed in bedrock within valleys and under confined groundwater conditions were most closely associated with the highest methane concentrations. Fifty-seven percent of valley wells had greater than or equal to 0.1 mg/L of methane, whereas only 10 percent of upland wells equaled or exceeded that concentration. Isotopic signatures differed between these groups as well. Methane in valley wells was predominantly thermogenic in origin, likely as a result of close vertical proximity to underlying methane-bearing saline groundwater and brine and possibly as a result of enhanced bedrock fracture permeability beneath valleys that provides an avenue for upward gas migration. Isotopic signatures of methane from four upland well samples indicated a microbial origin (carbon-dioxide reduction) with one sample possibly altered by microbial methane oxidation. Water samples from wells in a valley setting that indicate a mix of thermogenic and microbial methane reflect the close proximity of regional groundwater flow and underlying saline water and brine in valley areas. The microbial methane is likely produced by bacteria that utilize carbon dioxide or formational organic matter in highly reducing environments within the subregional groundwater flow system. This characterization of groundwater methane shows the importance of subsurface information (hydrogeology, well construction) in understanding methane occurrence and provides an initial conceptual framework that can be utilized in investigation of stray gas in south-central New York.

Distribution and origin of groundwater methane in the Wattenberg oil and gas field of northern Colorado.

PubMed

Li, Huishu; Carlson, Kenneth H

2014-01-01

Public concerns over potential environmental contamination associated with oil and gas well drilling and fracturing in the Wattenberg field in northeast Colorado are increasing. One of the issues of concern is the migration of oil, gas, or produced water to a groundwater aquifer resulting in contamination of drinking water. Since methane is the major component of natural gas and it can be dissolved and transported with groundwater, stray gas in aquifers has elicited attention. The initial step toward understanding the environmental impacts of oil and gas activities, such as well drilling and fracturing, is to determine the occurrence, where it is and where it came from. In this study, groundwater methane data that has been collected in response to a relatively new regulation in Colorado is analyzed. Dissolved methane was detected in 78% of groundwater wells with an average concentration of 4.0 mg/L and a range of 0-37.1 mg/L. Greater than 95% of the methane found in groundwater wells was classified as having a microbial origin, and there was minimal overlap between the C and H isotopic characterization of the produced gas and dissolved methane measured in the aquifer. Neither density of oil/gas wells nor distance to oil/gas wells had a significant impact on methane concentration suggesting other important factors were influencing methane generation and distribution. Thermogenic methane was detected in two aquifer wells indicating a potential contamination pathway from the producing formation, but microbial-origin gas was by far the predominant source of dissolved methane in the Wattenberg field.

Identifying Methane Sources with an Airborne Pulsed IPDA Lidar System Operating near 1.65 µm

NASA Astrophysics Data System (ADS)

Yerasi, A.; Bartholomew, J.; Tandy, W., Jr.; Emery, W. J.

2016-12-01

Methane is a powerful greenhouse gas that is predicted to play an important role in future global climate trends. It would therefore be beneficial to locate areas that produce methane in significant amounts so that these trends can be better understood. In this investigation, some initial performance test results of a lidar system called the Advanced Leak Detector Lidar - Natural Gas (ALDL-NG) are discussed. The feasibility of applying its fundamental principle of operation to methane source identification is also explored. The ALDL-NG was originally created by the Ball Aerospace & Technologies Corp. to reveal leaks emanating from pipelines that transport natural gas, which is primarily composed of methane. It operates in a pulsed integrated path differential absorption (IPDA) configuration and it is carried by a piloted, single-engine aircraft. In order to detect the presence of natural gas leaks, the laser wavelengths of its online and offline channels operate in the 1.65 µm region. The functionality of the ALDL-NG was tested during a recent field campaign in Colorado. It was determined that the ambient concentration of methane in the troposphere ( 1.8 ppm) could indeed be retrieved from ALDL-NG data with a lower-than-expected uncertainty ( 0.2 ppm). Furthermore, when the ALDL-NG scanned over areas that were presumed to be methane sources (feedlots, landfills, etc.), significantly higher concentrations of methane were retrieved. These results are intriguing because the ALDL-NG was not specifically designed to observe anything beyond natural gas pipelines. Nevertheless, they strongly indicate that utilizing an airborne pulsed IPDA lidar system operating near 1.65 µm may very well be a viable technique for identifying methane sources. Perhaps future lidar systems could build upon the heritage of the ALDL-NG and measure methane concentration with even better precision for a variety of scientific applications.

Effect of acetic acid on citric acid fermentation in an integrated citric acid-methane fermentation process.

PubMed

Xu, Jian; Chen, Yang-Qiu; Zhang, Hong-Jian; Tang, Lei; Wang, Ke; Zhang, Jian-Hua; Chen, Xu-Sheng; Mao, Zhong-Gui

2014-09-01

An integrated citric acid-methane fermentation process was proposed to solve the problem of extraction wastewater in citric acid fermentation process. Extraction wastewater was treated by anaerobic digestion and then recycled for the next batch of citric acid fermentation to eliminate wastewater discharge and reduce water resource consumption. Acetic acid as an intermediate product of methane fermentation was present in anaerobic digestion effluent. In this study, the effect of acetic acid on citric acid fermentation was investigated and results showed that lower concentration of acetic acid could promote Aspergillus niger growth and citric acid production. 5-Cyano-2,3-ditolyl tetrazolium chloride (CTC) staining was used to quantify the activity of A. niger cells, and the results suggested that when acetic acid concentration was above 8 mM at initial pH 4.5, the morphology of A. niger became uneven and the part of the cells' activity was significantly reduced, thereby resulting in deceasing of citric acid production. Effects of acetic acid on citric acid fermentation, as influenced by initial pH and cell number in inocula, were also examined. The result indicated that inhibition by acetic acid increased as initial pH declined and was rarely influenced by cell number in inocula.

Methane and Methanol Oxidation in Supercritical Water: Chemical Kinetics and Hydrothermal Flame Studies

DTIC Science & Technology

1996-01-01

water at 270 bar and at temperatures from 390 to 442 ’C. The initial methane concentration was nominally 0.15 gmol/L, a level representa- tive of...compounds appropriate for treatment with SCWO technology (Modell, 1989). Since then, the need to understand reaction chemistry has motivated extensive...understand the physics and chemistry controlling oxidation in supercritical water; to contribute to combustion science by performing fundamental studies in a

Effects of Nickel and Cobalt on Kinetics of Methanol Conversion by Methanogenic Sludge as Assessed by On-Line CH4 Monitoring

PubMed Central

Gonzalez-Gil, Graciela; Kleerebezem, Robbert; Lettinga, Gatze

1999-01-01

When metals were added in a pulse mode to methylotrophic-methanogenic biomass, three methane production rate phases were recognized. Increased concentrations of Ni and Co accelerated the initial exponential and final arithmetic increases in the methane production rate and reduced the temporary decrease in the rate. When Ni and Co were added continuously, the temporary decrease phase was eliminated and the exponential production rate increased. We hypothesize that the temporary decrease in the methane production rate and the final arithmetic increase in the methane production rate were due to micronutrient limitations and that the precipitation-dissolution kinetics of metal sulfides may play a key role in the biovailability of these compounds. PMID:10103284

Effects of nickel and cobalt on kinetics of methanol conversion by methanogenic sludge as assessed by on-line CH4 monitoring.

PubMed

Gonzalez-Gil, G; Kleerebezem, R; Lettinga, G

1999-04-01

When metals were added in a pulse mode to methylotrophic-methanogenic biomass, three methane production rate phases were recognized. Increased concentrations of Ni and Co accelerated the initial exponential and final arithmetic increases in the methane production rate and reduced the temporary decrease in the rate. When Ni and Co were added continuously, the temporary decrease phase was eliminated and the exponential production rate increased. We hypothesize that the temporary decrease in the methane production rate and the final arithmetic increase in the methane production rate were due to micronutrient limitations and that the precipitation-dissolution kinetics of metal sulfides may play a key role in the biovailability of these compounds.

Distribution and metabolism of quaternary amines in salt marshes

NASA Technical Reports Server (NTRS)

King, Gary M.

1985-01-01

Quaternary amines such as glycine betaine (GBT) are common osmotically active solutes in much of the marine biota. GBT is accumulated by various bacteria, algae, higher plants, invertebrates, and vertebrates in response to salinity or water stresses; in some species, GBT occurs at tens to hundreds of millimolar concentrations and can account for a significant fraction of total nitrogen. Initial studies suggest that GBT is readily converted to two potential methane precursors, trimethylamine (TMA) and acetate, in anoxic sediments. TMA is apparently the most important methane precursor in surface sediments containing sulfate reducing bacteria. In salt marshes, the bulk of the methane formed may be due to the metabolism of TMA rather than other substrates. Current research is focussed on testing this hypothesis and on determining the role of quaternary amino osmoregulatory solutes in methane fluxes from marine environments. Preliminary studies have dealt with several problems: (1) determination of GBT concentrations in the dominant flora and fauna of salt marshes; (2) synthesis of radiolabelled GBT for metabolic studies; and (3) determination of fates of BGT in marine sediments using radiotracers. Both GC and HPLC techniques have been used to assay GBT concentrations in plant and animal tissues. S. alterniflora is probably the only significant source of GBT (and indirectly of methane) since the biomass and distribution of most other species is limited. Current estimates suggest that S. alterniflora GBT could account for most of the methane efflux from salt marshes.

Analysis of methane biodegradation by Methylosinus trichosporium OB3b

PubMed Central

Rodrigues, Andréa dos Santos; Salgado, Belkis Valdman e Andréa Medeiros

2009-01-01

The microbial oxidation of methane in the atmosphere is performed by methanotrophic bacteria that use methane as a unique source of carbon and energy. The objective of this work consisted of the investigation of the best conditions of methane biodegradation by methanotrophic bacteria Methylosinus trichosporium OB3b that oxidize it to carbon dioxide, and the use of these microorganisms in monitoring methods for methane. The results showed that M. trichosporium OB3b was capable to degrade methane in a more effective way with an initial microorganism concentration of 0.0700 g.L-1, temperature of 30ºC, pH 6.5 and using 1.79 mmol of methane. In these same conditions, there was no bacterial growth when 2.69 mmol of methane was used. The specific rate of microorganism growth, the conversion factor, the efficiency and the volumetric productivity, for the optimized conditions of biodegradation were, respectively, 0.0324 h-1, 0.6830 gcells/gCH4, 73.73% and 2.7732.10-3 gcells/L.h. The final product of methane microbiological degradation, carbon dioxide, was quantified through the use of a commercial electrode, and, through this, the grade of methane conversion in carbon dioxide was calculated. PMID:24031362

Simplified Two-Time Step Method for Calculating Combustion and Emission Rates of Jet-A and Methane Fuel With and Without Water Injection

NASA Technical Reports Server (NTRS)

Molnar, Melissa; Marek, C. John

2005-01-01

A simplified kinetic scheme for Jet-A, and methane fuels with water injection was developed to be used in numerical combustion codes, such as the National Combustor Code (NCC) or even simple FORTRAN codes. The two time step method is either an initial time averaged value (step one) or an instantaneous value (step two). The switch is based on the water concentration in moles/cc of 1x10(exp -20). The results presented here results in a correlation that gives the chemical kinetic time as two separate functions. This two time step method is used as opposed to a one step time averaged method previously developed to determine the chemical kinetic time with increased accuracy. The first time averaged step is used at the initial times for smaller water concentrations. This gives the average chemical kinetic time as a function of initial overall fuel air ratio, initial water to fuel mass ratio, temperature, and pressure. The second instantaneous step, to be used with higher water concentrations, gives the chemical kinetic time as a function of instantaneous fuel and water mole concentration, pressure and temperature (T4). The simple correlations would then be compared to the turbulent mixing times to determine the limiting rates of the reaction. The NASA Glenn GLSENS kinetics code calculates the reaction rates and rate constants for each species in a kinetic scheme for finite kinetic rates. These reaction rates are used to calculate the necessary chemical kinetic times. Chemical kinetic time equations for fuel, carbon monoxide and NOx are obtained for Jet-A fuel and methane with and without water injection to water mass loadings of 2/1 water to fuel. A similar correlation was also developed using data from NASA's Chemical Equilibrium Applications (CEA) code to determine the equilibrium concentrations of carbon monoxide and nitrogen oxide as functions of overall equivalence ratio, water to fuel mass ratio, pressure and temperature (T3). The temperature of the gas entering the turbine (T4) was also correlated as a function of the initial combustor temperature (T3), equivalence ratio, water to fuel mass ratio, and pressure.

Ancient dissolved methane in inland waters at low concentrations revealed by a new collection method for radiocarbon (^{14}C) analysis

NASA Astrophysics Data System (ADS)

Dean, Joshua F.; Billett, Michael F.; Murray, Callum; Garnett, Mark H.

2017-04-01

Methane (CH4) is a powerful greenhouse gas and is released to the atmosphere from freshwater systems in numerous biomes globally. Radiocarbon (14C) analysis of methane can provide unique information about its age, source and rate of cycling in natural environments. Methane is often released from aquatic sediments in bubbles (ebullition), but dissolved methane is also present in lakes and streams at lower concentrations, and may not be of the same age or source. Obtaining sufficient non-ebullitive aquatic methane for 14C analysis remains a major technical challenge. Previous studies have shown that freshwater methane, in both dissolved and ebullitive form, can be significantly older than other forms of aquatic carbon (C), and it is therefore important to characterise this part of the terrestrial C balance. We present a novel method to capture sufficient amounts of dissolved methane from freshwater environments for 14C analysis by circulating water across a hydrophobic, gas-permeable membrane and collecting the methane in a large collapsible vessel. The results of laboratory and field tests show that reliable dissolved δ13CH4 and 14CH4 samples can be readily collected over short time periods (˜4 to 24 hours), at relatively low cost and from a variety of surface water types. The initial results further support previous findings that dissolved methane can be significantly older than other forms of aquatic C, especially in organic-rich catchments, and is currently unaccounted for in many terrestrial C balances and models. This method is suitable for use in remote locations, and could potentially be used to detect the leakage of unique 14CH4 signatures from point sources into waterways, e.g. coal seam gas and landfill gas.

Seeding hydrate formation in water-saturated sand with dissolved-phase methane obtained from hydrate dissolution: A progress report

USGS Publications Warehouse

Waite, William F.; Osegovic, J.P.; Winters, William J.; Max, M.D.; Mason, David H.

2008-01-01

An isobaric flow loop added to the Gas Hydrate And Sediment Test Laboratory Instrument (GHASTLI) is being investigated as a means of rapidly forming methane hydrate in watersaturated sand from methane dissolved in water. Water circulates through a relatively warm source chamber, dissolving granular methane hydrate that was pre-made from seed ice, then enters a colder hydrate growth chamber where hydrate can precipitate in a water-saturated sand pack. Hydrate dissolution in the source chamber imparts a known methane concentration to the circulating water, and hydrate particles from the source chamber entrained in the circulating water can become nucleation sites to hasten the onset of hydrate formation in the growth chamber. Initial results suggest hydrate grows rapidly near the growth chamber inlet. Techniques for establishing homogeneous hydrate formation throughout the sand pack are being developed.

30 CFR 75.1324 - Methane concentration and tests.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Methane concentration and tests. 75.1324... Methane concentration and tests. (a) No shot shall be fired in an area that contains 1.0 volume percent or more of methane. (b) Immediately before shots are fired, the methane concentration in a working place...

30 CFR 75.1324 - Methane concentration and tests.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Methane concentration and tests. 75.1324... Methane concentration and tests. (a) No shot shall be fired in an area that contains 1.0 volume percent or more of methane. (b) Immediately before shots are fired, the methane concentration in a working place...

Effect of total solids content on methane and volatile fatty acid production in anaerobic digestion of food waste.

PubMed

Liotta, Flavia; d'Antonio, Giuseppe; Esposito, Giovanni; Fabbricino, Massimiliano; van Hullebusch, Eric D; Lens, Piet N L; Pirozzi, Francesco; Pontoni, Ludovico

2014-10-01

This work investigates the role of the moisture content on anaerobic digestion of food waste, as representative of rapidly biodegradable substrates, analysing the role of volatile fatty acid production on process kinetics. A range of total solids from 4.5% to 19.2% is considered in order to compare methane yields and kinetics of reactors operated under wet to dry conditions. The experimental results show a reduction of the specific final methane yield of 4.3% and 40.8% in semi-dry and dry conditions compared with wet conditions. A decreasing trend of the specific initial methane production rate is observed when increasing the total solids concentration. Because of lack of water, volatile fatty acids accumulation occurs during the first step of the process at semi-dry and dry conditions, which is considered to be responsible for the reduction of process kinetic rates. The total volatile fatty acids concentration and speciation are proposed as indicators of process development at different total solids content. © The Author(s) 2014.

Biogenic coal-to-methane conversion efficiency decreases after repeated organic amendment

USGS Publications Warehouse

Davis, Katherine J.; Barnhart, Elliott P.; Fields, Matthew W.; Gerlach, Robin

2018-01-01

Addition of organic amendments to coal-containing systems can increase the rate and extent of biogenic methane production for 60–80 days before production slows or stops. Understanding the effect of repeated amendment additions on the rate and extent of enhanced coal-dependent methane production is important if biological coal-to-methane conversion is to be enhanced on a commercial scale. Microalgal biomass was added at a concentration of 0.1 g/L to microcosms with and without coal on days 0, 76, and 117. Rates of methane production were enhanced after the initial amendment but coal-containing treatments produced successively decreasing amounts of methane with each amendment. During the first amendment period, 113% of carbon added as amendment was recovered as methane, whereas in the second and third amendment periods, 39% and 32% of carbon added as amendment was recovered as methane, respectively. Additionally, algae-amended coal treatments produced ∼38% more methane than unamended coal treatments and ∼180% more methane than amended coal-free treatments after one amendment. However, a second amendment addition resulted in only an ∼25% increase in methane production for coal versus noncoal treatments and a third amendment addition resulted in similar methane production in both coal and noncoal treatments. Successive amendment additions appeared to result in a shift from coal-to-methane conversion to amendment-to-methane conversion. The reported results indicate that a better understanding is needed of the potential impacts and efficiencies of repeated stimulation for enhanced coal-to-methane conversion.

Carbon nanotubes accelerate methane production in pure cultures of methanogens and in a syntrophic coculture.

PubMed

Salvador, Andreia F; Martins, Gilberto; Melle-Franco, Manuel; Serpa, Ricardo; Stams, Alfons J M; Cavaleiro, Ana J; Pereira, M Alcina; Alves, M Madalena

2017-07-01

Carbon materials have been reported to facilitate direct interspecies electron transfer (DIET) between bacteria and methanogens improving methane production in anaerobic processes. In this work, the effect of increasing concentrations of carbon nanotubes (CNT) on the activity of pure cultures of methanogens and on typical fatty acid-degrading syntrophic methanogenic coculture was evaluated. CNT affected methane production by methanogenic cultures, although acceleration was higher for hydrogenotrophic methanogens than for acetoclastic methanogens or syntrophic coculture. Interestingly, the initial methane production rate (IMPR) by Methanobacterium formicicum cultures increased 17 times with 5 g·L -1 CNT. Butyrate conversion to methane by Syntrophomonas wolfei and Methanospirillum hungatei was enhanced (∼1.5 times) in the presence of CNT (5 g·L -1 ), but indications of DIET were not obtained. Increasing CNT concentrations resulted in more negative redox potentials in the anaerobic microcosms. Remarkably, without a reducing agent but in the presence of CNT, the IMPR was higher than in incubations with reducing agent. No growth was observed without reducing agent and without CNT. This finding is important to re-frame discussions and re-interpret data on the role of conductive materials as mediators of DIET in anaerobic communities. It also opens new challenges to improve methane production in engineered methanogenic processes. © 2017 The Authors. Environmental Microbiology published by Society for Applied Microbiology and John Wiley & Sons Ltd.

Inhibition of microbial metabolism in anaerobic lagoons by selected sulfonamides, tetracyclines, lincomycin, and tylosin tartrate

USGS Publications Warehouse

Loftin, Keith A.; Henny, Cynthia; Adams, Craig D.; Surampali, Rao; Mormile, Melanie R.

2005-01-01

Antibiotics are used to maintain healthy livestock and to promote weight gain in concentrated animal feed operations. Antibiotics rarely are metabolized completely by livestock and, thus, are often present in livestock waste and in waste-treatment lagoons. The introduction of antibiotics into anaerobic lagoons commonly used for swine waste treatment has the potential for negative impacts on lagoon performance, which relies on a consortium of microbes ranging from fermentative microorganisms to methanogens. To address this concern, the effects of eight common veterinary antibiotics on anaerobic activity were studied. Anaerobic microcosms, prepared from freshly collected lagoon slurries, were amended with individual antibiotics at 10 mg/L for the initial screening study and at 1, 5, and 25 mg/L for the dose-response study. Monitored metabolic indicators included hydrogen, methane, and volatile fatty acid concentrations as well as chemical oxygen demand. The selected antibiotics significantly inhibited methane production relative to unamended controls, thus indicating that antibiotics at concentrations commonly found in swine lagoons can negatively impact anaerobic metabolism. Additionally, historical antibiotic usage seems to be a potential factor in affecting methane production. Specifically, less inhibition of methane production was noted in samples taken from the lagoon with a history of multiple-antibiotic use.

Inhibition of microbial metabolism in anaerobic lagoons by selected sulfonamides, tetracyclines, lincomycin, and tylosin tartrate.

PubMed

Loftin, Keith A; Henny, Cynthia; Adams, Craig D; Surampali, Rao; Mormile, Melanie R

2005-04-01

Antibiotics are used to maintain healthy livestock and to promote weight gain in concentrated animal feed operations. Antibiotics rarely are metabolized completely by livestock and, thus, are often present in livestock waste and in waste-treatment lagoons. The introduction of antibiotics into anaerobic lagoons commonly used for swine waste treatment has the potential for negative impacts on lagoon performance, which relies on a consortium of microbes ranging from fermentative microorganisms to methanogens. To address this concern, the effects of eight common veterinary antibiotics on anaerobic activity were studied. Anaerobic microcosms, prepared from freshly collected lagoon slurries, were amended with individual antibiotics at 10 mg/L for the initial screening study and at 1, 5, and 25 mg/L for the dose-response study. Monitored metabolic indicators included hydrogen, methane, and volatile fatty acid concentrations as well as chemical oxygen demand. The selected antibiotics significantly inhibited methane production relative to unamended controls, thus indicating that antibiotics at concentrations commonly found in swine lagoons can negatively impact anaerobic metabolism. Additionally, historical antibiotic usage seems to be a potential factor in affecting methane production. Specifically, less inhibition of methane production was noted in samples taken from the lagoon with a history of multiple-antibiotic use.

Identification, Attribution, and Quantification of Highly Heterogeneous Methane Sources Using a Mobile Stable Isotope Analyzer

NASA Astrophysics Data System (ADS)

Crosson, E.; Rella, C.; Cunningham, K.

2012-04-01

Despite methane's importance as a potent greenhouse gas second only to carbon dioxide in the magnitude of its contribution to global warming, natural contributions to the overall methane budget are only poorly understood. A big contributor to this gap in knowledge is the highly spatially and temporally heterogeneous nature of most natural (and for that matter anthropogenic) methane sources. This high degree of heterogeneity, where the methane emission rates can vary over many orders of magnitude on a spatial scale of meters or even centimeters, and over a temporal scale of minutes or even seconds, means that traditional methods of emissions flux estimation, such as flux chambers or eddy-covariance, are difficult or impossible to apply. In this paper we present new measurement methods that are capable of detecting, attributing, and quantifying emissions from highly heterogeneous sources. These methods take full advantage of the new class of methane concentration and stable isotope analyzers that are capable of laboratory-quality analysis from a mobile field platform in real time. In this paper we present field measurements demonstrating the real-time detection of methane 'hot spots,' attribution of the methane to a source process via real-time stable isotope analysis, and quantification of the emissions flux using mobile concentration measurements of the horizontal and vertical atmospheric dispersion, combined with atmospheric transport calculations. Although these techniques are applicable to both anthropogenic and natural methane sources, in this initial work we focus primarily on landfills and fugitive emissions from natural gas distribution, as these sources are better characterized, and because they provide a more reliable and stable source of methane for quantifying the measurement uncertainty inherent in the different methods. Implications of these new technologies and techniques are explored for the quantification of natural methane sources in a variety of environments, including wetlands, peatlands, and the arctic.

Annual variability and regulation of methane and sulfate fluxes in Baltic Sea estuarine sediments

NASA Astrophysics Data System (ADS)

Sawicka, Joanna E.; Brüchert, Volker

2017-01-01

Marine methane emissions originate largely from near-shore coastal systems, but emission estimates are often not based on temporally well-resolved data or sufficient understanding of the variability of methane consumption and production processes in the underlying sediment. The objectives of our investigation were to explore the effects of seasonal temperature, changes in benthic oxygen concentration, and historical eutrophication on sediment methane concentrations and benthic fluxes at two type localities for open-water coastal versus eutrophic, estuarine sediment in the Baltic Sea. Benthic fluxes of methane and oxygen and sediment pore-water concentrations of dissolved sulfate, methane, and 35S-sulfate reduction rates were obtained over a 12-month period from April 2012 to April 2013. Benthic methane fluxes varied by factors of 5 and 12 at the offshore coastal site and the eutrophic estuarine station, respectively, ranging from 0.1 mmol m-2 d-1 in winter at an open coastal site to 2.6 mmol m-2 d-1 in late summer in the inner eutrophic estuary. Total oxygen uptake (TOU) and 35S-sulfate reduction rates (SRRs) correlated with methane fluxes showing low rates in the winter and high rates in the summer. The highest pore-water methane concentrations also varied by factors of 6 and 10 over the sampling period with the lowest values in the winter and highest values in late summer-early autumn. The highest pore-water methane concentrations were 5.7 mM a few centimeters below the sediment surface, but they never exceeded the in situ saturation concentration. Of the total sulfate reduction, 21-24 % was coupled to anaerobic methane oxidation, lowering methane concentrations below the sediment surface far below the saturation concentration. The data imply that bubble emission likely plays no or only a minor role in methane emissions in these sediments. The changes in pore-water methane concentrations over the observation period were too large to be explained by temporal changes in methane formation and methane oxidation rates due to temperature alone. Additional factors such as regional and local hydrostatic pressure changes and coastal submarine groundwater flow may also affect the vertical and lateral transport of methane.

Methane Recycling During Burial of Methane Hydrate-Bearing Sediments

NASA Astrophysics Data System (ADS)

You, K.; Flemings, P. B.

2017-12-01

We quantitatively investigate the integral processes of methane hydrate formation from local microbial methane generation, burial of methane hydrate with sedimentation, and methane recycling at the base of the hydrate stability zone (BHSZ) with a multiphase multicomponent numerical model. Methane recycling happens in cycles, and there is not a steady state. Each cycle starts with free gas accumulation from hydrate dissociation below the BHSZ. This free gas flows upward under buoyancy, elevates the hydrate saturation and capillary entry pressure at the BHSZ, and this prevents more free gas flowing in. Later as this layer with elevated hydrate saturation is buried and dissociated, the large amount of free gas newly released and accumulated below rapidly intrudes into the hydrate stability zone, drives rapid hydrate formation and creates three-phase (gas, liquid and hydrate) equilibrium above the BHSZ. The gas front retreats to below the BHSZ until all the free gas is depleted. The shallowest depth that the free gas reaches in one cycle moves toward seafloor as more and more methane is accumulated to the BHSZ with time. More methane is stored above the BHSZ in the form of concentrated hydrate in sediments with relatively uniform pore throat, and/or with greater compressibility. It is more difficult to initiate methane recycling in passive continental margins where the sedimentation rate is low, and in sediments with low organic matter content and/or methanogenesis reaction rate. The presence of a permeable layer can store methane for significant periods of time without recycling. In a 2D system where the seafloor dips rapidly, the updip gas flow along the BHSZ transports more methane toward topographic highs where methane gas and elevated hydrate saturation intrude deeper into the hydrate stability zone within one cycle. This could lead to intermittent gas venting at seafloor at the topographic highs. This study provides insights on many phenomenon associated with methane recycling, such as the formation of free gas zone, concentrated hydrate zone, bottom simulating reflector, and overpressured zone around the BHSZ, and gas venting at seafloor.

Carbon dioxide induced bubble formation in a CH4-CO2-H2O ternary system: a molecular dynamics simulation study.

PubMed

Sujith, K S; Ramachandran, C N

2016-02-07

The extraction of methane from its hydrates using carbon dioxide involves the decomposition of the hydrate resulting in a CH4-CO2-H2O ternary solution. Using classical molecular dynamics simulations, we investigate the evolution of dissolved gas molecules in the ternary system at different concentrations of CO2. Various compositions considered in the present study resemble the solution formed during the decomposition of methane hydrates at the initial stages of the extraction process. We find that the presence of CO2 aids the formation of CH4 bubbles by causing its early nucleation. Elucidation of the composition of the bubble revealed that in ternary solutions with high concentration of CO2, mixed gas bubbles composed of CO2 and CH4 are formed. To understand the role of CO2 in the nucleation of CH4 bubbles, the structure of the bubble formed was analyzed, which revealed that there is an accumulation of CO2 at the interface of the bubble and the surrounding water. The aggregation of CO2 at the bubble-water interface occurs predominantly when the concentration of CO2 is high. Radial distribution function for the CH4-CO2 pair indicates that there is an increasingly favorable direct contact between dissolved CH4 and CO2 molecules in the bubble-water interface. It is also observed that the presence of CO2 at the interface results in the decrease in surface tension. Thus, CO2 leads to greater stability of the bubble-water interface thereby bringing down the critical size of the bubble nuclei. The results suggest that a rise in concentration of CO2 helps in the removal of dissolved CH4 thereby preventing the accumulation of methane in the liquid phase. Thus, the presence of CO2 is predicted to assist the decomposition of methane hydrates in the initial stages of the replacement process.

Dissolved gasesous hydrocarbons in shallow groundwater of Lower Saxony, Germany - Revisited 2016

NASA Astrophysics Data System (ADS)

Schloemer, Stefan; Illing, Christian J.; Blumenberg, Martin; Oest, Johanna; Elbracht, Jörg

2017-04-01

Many concerns arise within the public and government/political institutions over potential groundwater contamination from deep drilling operations. For this reason we initiated a baseline study in 2014 on the distribution of dissolved methane, ethane and propane in shallow groundwater ( 1000 groundwater wells, Schloemer et al., 2016) of Lower Saxony, which includes the major petroleum and natural gas provinces in Germany. We observed a variation of dissolved methane concentration over 7 orders of magnitude (20 nl/l to 60 ml/l [v/v]). Methane delta13C compositions ranged from -110‰ to +25‰ vs VPDB, narrowly clustering around -70‰ at high concentrations but being increasingly more variable at lower concentrations (-40‰ to -80‰)). Most of the data are clearly indicative for methanogenic processes, samples unusually enriched in delta13C can best be explained by secondary methane oxidation. Although some general regional trend can be observed, results are highly variable within short lateral distances or within different aquifers/filter depths. Frequently ethane (27% of samples, median 50nl/l) and occasionally propane (8%, median 23nl/l) has been detected. Lacking the carbon isotope composition of these homologues and thus solely based on the extremely low concentrations and atypical ethane/propane ratios, these have been tentatively interpreted as ubiquitous microbial background. From the original 2014 sample set around 100 wells have been selected for consecutive testing through 2015. In spring 2016 a total number of 1100 wells have been sampled, 700 of which had already been part of the initial study, providing us with the unique opportunity to assess long term variations. The overall comparison of these 700 samples revealed only small relative variations in methane concentrations (mostly < ± 25%), although higher variations are common at concentrations less than 1 µl/l. Correspondingly the carbon isotopic composition of paired samples is quite stable (± 2‰)) for most of the samples ( 60%) but large discrepancies can be observed at low absolute concentrations (> ± 5‰ in 25% of samples). Minor variations could be related to uncertainties in laboratory analysis (± 10% in concentration, ± 0.5‰ delta13C). To which extent the small number of sampled groundwater with unusually high variations are indeed a result of a naturally occurring process (rapidly changing conditions or anthropogenic influence) is currently under investigation. However, applying different sampling conditions/procedures (i.e. different pumps, flow rates) had to be accepted during the course of the project and might be a reason as well. In any case our preliminary results point toward the necessity of repeated sampling (particularly in shallow unconfined aquifers) to account for possible natural variations and of strictly consistent sampling protocols when analyzing "non-conservative" dissolved gases. Reference Schloemer, S., Elbracht, J., Blumenberg, M. and Illing, C.J., 2016. Distribution and origin of dissolved methane, ethane and propane in shallow groundwater of Lower Saxony, Germany. Applied Geochemistry, 67: 118-132.

Long open-path TDL based system for monitoring background concentration for deployment at Jungfraujoch High Altitude Research Station- Switzerland

NASA Astrophysics Data System (ADS)

Simeonov, Valentin; van den Bergh, Hubert; Parlange, Marc

2010-05-01

A new, long open-path instrument for monitoring of path-averaged methane and water vapor concentrations will be presented. The instrument is built on the monostatic scheme (transceiver - distant retroreflector). A VCSEL tunable diode laser (TDL) with a central wavelength of 1654 nm is used as a light source. A specially designed, single-cell, hollow-cube retroreflector with 150 mm aperture will be installed at 1200 m from the transceiver in the final deployment at Jungfraujjoch and 100 mm retroreflectors will be used in the other applications. The receiver is built around a 20 cm Newtonian telescope. To avoid distortions in the shape of a methane line, caused by atmospheric turbulences, the line is scanned within 1 µs. Fast InGaAs photodiodes and 200 MHz are used to achieve this scanning rate. The expected concentration resolution for the above mentioned path lengths is of the order of 2 ppb. The instrument is developed at the Swiss Federal Institute of Technology - Lausanne (EPFL) Switzerland and will be used within the GAW+ CH program for long-term monitoring of background methane concentration in the Swiss Alps. After completing the initial tests at EPFL the instrument will be installed in 2012 at the High Altitude Research Station Jungfraujoch (HARSJ) located at 3580 m ASL. The HARSJ is one of the 24 global GAW stations and carries on continuous observations of a number of trace gasses, including methane. One of the goals of the project is to compare path-averaged to ongoing point measurements of methane in order to identify possible influence of the station. Future deployments of a copy of the instrument include the Colombian part of Amazonia and Siberian wetlands.

Effect of Elevated CO2 Concentration, Elevated Temperature and No Nitrogen Fertilization on Methanogenic Archaeal and Methane-Oxidizing Bacterial Community Structures in Paddy Soil

PubMed Central

Liu, Dongyan; Tago, Kanako; Hayatsu, Masahito; Tokida, Takeshi; Sakai, Hidemitsu; Nakamura, Hirofumi; Usui, Yasuhiro; Hasegawa, Toshihiro; Asakawa, Susumu

2016-01-01

Elevated concentrations of atmospheric CO2 ([CO2]) enhance the production and emission of methane in paddy fields. In the present study, the effects of elevated [CO2], elevated temperature (ET), and no nitrogen fertilization (LN) on methanogenic archaeal and methane-oxidizing bacterial community structures in a free-air CO2 enrichment (FACE) experimental paddy field were investigated by PCR-DGGE and real-time quantitative PCR. Soil samples were collected from the upper and lower soil layers at the rice panicle initiation (PI) and mid-ripening (MR) stages. The composition of the methanogenic archaeal community in the upper and lower soil layers was not markedly affected by the elevated [CO2], ET, or LN condition. The abundance of the methanogenic archaeal community in the upper and lower soil layers was also not affected by elevated [CO2] or ET, but was significantly increased at the rice PI stage and significantly decreased by LN in the lower soil layer. In contrast, the composition of the methane-oxidizing bacterial community was affected by rice-growing stages in the upper soil layer. The abundance of methane-oxidizing bacteria was significantly decreased by elevated [CO2] and LN in both soil layers at the rice MR stage and by ET in the upper soil layer. The ratio of mcrA/pmoA genes correlated with methane emission from ambient and FACE paddy plots at the PI stage. These results indicate that the decrease observed in the abundance of methane-oxidizing bacteria was related to increased methane emission from the paddy field under the elevated [CO2], ET, and LN conditions. PMID:27600710

Effect of Elevated CO2 Concentration, Elevated Temperature and No Nitrogen Fertilization on Methanogenic Archaeal and Methane-Oxidizing Bacterial Community Structures in Paddy Soil.

PubMed

Liu, Dongyan; Tago, Kanako; Hayatsu, Masahito; Tokida, Takeshi; Sakai, Hidemitsu; Nakamura, Hirofumi; Usui, Yasuhiro; Hasegawa, Toshihiro; Asakawa, Susumu

2016-09-29

Elevated concentrations of atmospheric CO2 ([CO2]) enhance the production and emission of methane in paddy fields. In the present study, the effects of elevated [CO2], elevated temperature (ET), and no nitrogen fertilization (LN) on methanogenic archaeal and methane-oxidizing bacterial community structures in a free-air CO2 enrichment (FACE) experimental paddy field were investigated by PCR-DGGE and real-time quantitative PCR. Soil samples were collected from the upper and lower soil layers at the rice panicle initiation (PI) and mid-ripening (MR) stages. The composition of the methanogenic archaeal community in the upper and lower soil layers was not markedly affected by the elevated [CO2], ET, or LN condition. The abundance of the methanogenic archaeal community in the upper and lower soil layers was also not affected by elevated [CO2] or ET, but was significantly increased at the rice PI stage and significantly decreased by LN in the lower soil layer. In contrast, the composition of the methane-oxidizing bacterial community was affected by rice-growing stages in the upper soil layer. The abundance of methane-oxidizing bacteria was significantly decreased by elevated [CO2] and LN in both soil layers at the rice MR stage and by ET in the upper soil layer. The ratio of mcrA/pmoA genes correlated with methane emission from ambient and FACE paddy plots at the PI stage. These results indicate that the decrease observed in the abundance of methane-oxidizing bacteria was related to increased methane emission from the paddy field under the elevated [CO2], ET, and LN conditions.

Demonstration of the enrichment of medium quality gas from gob wells through interactive well operating practices. Final report, June--December, 1995

DOE Office of Scientific and Technical Information (OSTI.GOV)

Blackburn, S.T.; Sanders, R.G.; Boyer, C.M. II

1995-12-01

Methane released to the atmosphere during coal mining operations is believed to contribute to global warming and represents a waste of a valuable energy resource. Commercial production of pipeline-quality gob well methane through wells drilled from the surface into the area above the gob can, if properly implemented, be the most effective means of reducing mine methane emissions. However, much of the gas produced from gob wells is vented because the quality of the gas is highly variable and is often below current natural gas pipeline specifications. Prior to the initiation of field-testing required to further understand the operational criteriamore » for upgrading gob well gas, a preliminary evaluation and assessment was performed. An assessment of the methane gas in-place and producible methane resource at the Jim Walter Resources, Inc. No. 4 and No. 5 Mines established a potential 15-year supply of 60 billion cubic feet of mien methane from gob wells, satisfying the resource criteria for the test site. To understand the effect of operating conditions on gob gas quality, gob wells producing pipeline quality (i.e., < 96% hydrocarbons) gas at this site will be operated over a wide range of suction pressures. Parameters to be determined will include absolute methane quantity and methane concentration produced through the gob wells; working face, tailgate and bleeder entry methane levels in the mine; and the effect on the economics of production of gob wells at various levels of methane quality. Following this, a field demonstration will be initiated at a mine where commercial gob gas production has not been attempted. The guidelines established during the first phase of the project will be used to design the production program. The economic feasibility of various utilization options will also be tested based upon the information gathered during the first phase. 41 refs., 41 figs., 12 tabs.« less

Methane in Sediments From Three Tropical, Coastal Lagoons on the Yucatan Peninsula, Mexico

NASA Astrophysics Data System (ADS)

Young, B.; Paytan, A.; Miller, L.; Herrera-Silveira, J.

2002-12-01

Tropical wetlands are significant sources of methane (CH4) to the atmosphere, and the majority of research on methane flux and cycling in the tropics has been conducted in fresh-water wetlands and lakes. However, several previous studies have shown that tropical coastal ecosystems can produce significant methane flux to the atmosphere despite the presence of moderate to marine salinities. Information regarding methane cycling within the sediments is crucial to understanding how natural and anthropogenic changes may influence these systems. We measured methane concentrations in sediments from two tropical coastal lagoons during different seasons, as well as in a third, heavily polluted, lagoon (Terminos) during the rainy season. These three lagoons, Celestun, Chelem, and Terminos, have similar vegetation, seasonal temperature and rainfall patterns, and substrate geology, but very different levels of ground water discharge and pollution. Methane concentrations in Celestun and Terminos lagoon showed high spatial variability(> 0.001 to 5 mmol kg-1 wet sediment), while sediments in Chelem Lagoon, which has near marine salinities and little sewage discharge, showed much lower variability of methane concentrations. Methane concentrations in Celestun sediments displayed two predominant patterns: some profiles contained a peak in methane concentration (1 to 2 mmole methane kg-1 wet sediment) between 5 and 15 cm below the surface while the other sediment profiles instead displayed a steady or monotonic increase in methane concentration with depth to approximately 0.025-0.080 mmol kg-1 at 10-15cm below surface followed by stable methane concentrations to the bottom of the cores (20-45 cm below the surface). A subsurface peak in methane concentrations was also found in some locations in Chelem, however, the concentrations were much lower than those measured in Celestun. Previous studies have shown that sewage pollution may drastically increase methane production in tropical coastal ecosystems. Laboratory experiments using sediment from the upper 20 cm in Celestun lagoon resulted in high rates of biogenic production of methane from the addition of trimethylamine, hydrogen, and, while additions of formate and acetate stimulated methane production to a lesser extent. This indicates that methane production in these sediments may be highly responsive to natural or anthropogenic changes in substrate availability. By synthesizing laboratory data and extensive field measurements from the lagoons, we hope to shed light on the factors controlling methane cycling in these sediments, and to better estimate methane flux to the atmosphere from these ecosystems.

Oceanic Methane Concentrations in Three Mexican Regions

EPA Science Inventory

The atmospheric concentration of methane has increased significantly over the last several decades. Methane is an important greenhouse gas, and it is important to better quantify methane sources and sinks. Dissolved methane in the ocean is produced by biological and hydrothermal ...

New Reduced Two-Time Step Method for Calculating Combustion and Emission Rates of Jet-A and Methane Fuel With and Without Water Injection

NASA Technical Reports Server (NTRS)

Molnar, Melissa; Marek, C. John

2004-01-01

A simplified kinetic scheme for Jet-A, and methane fuels with water injection was developed to be used in numerical combustion codes, such as the National Combustor Code (NCC) or even simple FORTRAN codes that are being developed at Glenn. The two time step method is either an initial time averaged value (step one) or an instantaneous value (step two). The switch is based on the water concentration in moles/cc of 1x10(exp -20). The results presented here results in a correlation that gives the chemical kinetic time as two separate functions. This two step method is used as opposed to a one step time averaged method previously developed to determine the chemical kinetic time with increased accuracy. The first time averaged step is used at the initial times for smaller water concentrations. This gives the average chemical kinetic time as a function of initial overall fuel air ratio, initial water to fuel mass ratio, temperature, and pressure. The second instantaneous step, to be used with higher water concentrations, gives the chemical kinetic time as a function of instantaneous fuel and water mole concentration, pressure and temperature (T4). The simple correlations would then be compared to the turbulent mixing times to determine the limiting properties of the reaction. The NASA Glenn GLSENS kinetics code calculates the reaction rates and rate constants for each species in a kinetic scheme for finite kinetic rates. These reaction rates were then used to calculate the necessary chemical kinetic times. Chemical kinetic time equations for fuel, carbon monoxide and NOx were obtained for Jet-A fuel and methane with and without water injection to water mass loadings of 2/1 water to fuel. A similar correlation was also developed using data from NASA's Chemical Equilibrium Applications (CEA) code to determine the equilibrium concentrations of carbon monoxide and nitrogen oxide as functions of overall equivalence ratio, water to fuel mass ratio, pressure and temperature (T3). The temperature of the gas entering the turbine (T4) was also correlated as a function of the initial combustor temperature (T3), equivalence ratio, water to fuel mass ratio, and pressure.

Simultaneous Cr(VI) bio-reduction and methane production by anaerobic granular sludge.

PubMed

Hu, Qian; Sun, Jiaji; Sun, Dezhi; Tian, Lan; Ji, Yanan; Qiu, Bin

2018-08-01

Wastewater containing toxic hexavalent chromium (Cr(VI)) were treated with well-organized anaerobic granular sludge in this study. Results showed that the anaerobic granular sludge rapidly removed Cr(VI), and 2000 µg·L -1 Cr(VI) was completely eliminated within 6 min, which was much faster than the reported duration of removal by reported artificial materials. Sucrose added as a carbon source acted as an initial electron donor to reduce Cr(VI) to Cr(III). This process was considered as the main mechanism of Cr(VI) removal. Methane production by anaerobic granular sludge was improved by the addition of Cr(VI) at a concentration lower than 500 µg·L -1 . Anaerobic granular sludge had a well-organized structure, which presented good resistance against toxic Cr(VI). Trichoccus accelerated the degradation of organic substances to generate acetates with a low Cr(VI) concentration, thereby enhancing methane production by acetotrophic methanogens. Copyright © 2018 Elsevier Ltd. All rights reserved.

Sensitive detection of methane at 3.3 μm using an integrating sphere and interband cascade laser

NASA Astrophysics Data System (ADS)

Davis, N. M.; Hodgkinson, J.; Francis, D.; Tatam, R. P.

2016-04-01

Detection of methane at 3.3μm using a DFB Interband Cascade Laser and gold coated integrating sphere is performed. A 10cm diameter sphere with effective path length of 54.5cm was adapted for use as a gas cell. A comparison between this system and one using a 25cm path length single-pass gas cell is made using direct TDLS and methane concentrations between 0 and 1000 ppm. Initial investigations suggest a limit of detection of 1.0ppm for the integrating sphere and 2.2ppm for the single pass gas cell. The system has potential applications in challenging or industrial environments subject to high levels of vibration.

Distribution and Emission of Methane in Nakdong Estuary

NASA Astrophysics Data System (ADS)

Ryu, J.; An, S.

2014-12-01

Despite a small area, coastal areas contribute most to the oceanic methane flux. A wide range of methane fluxes have been reported in the coastal areas, but limited data were presented for Korean coastal areas. The air and surface water was sampled in Nakdong Estuary where the barrage had been constructed, and methane concentrations were measured using Gas Chromatography. To see the influence of the barrage, surface water was sampled outside and inside the barrage respectively. In the expectation that methane distribution would be different depending on the tides, surface water outside the barrage was collected at high and low tide respectively. Headspace technique and Membrane Inlet Mass Spectrometry were also used. The average atmospheric concentration (1.82ppm) was lower than the global average concentration expected from the IPCC scenario. The concentrations of water inside the barrage (average 173nM) were similar to those measured in other rivers but in the lower side. The average concentrations outside the barrage (52nM at high tide, 85nM at low tide) were lower than those measured in other coastal areas, but of the same order of magnitude as the European tidal estuaries. Methane concentrations in Nakdong estuary were higher than the methane concentration equilibrated with the atmosphere. The spatial variability of methane concentration in Nakdong estuary seems to be the result of the fresh (high methane) and sea (low methane) water mixing. Meanwhile large tidal flat area in Nakdong estuary should play a major role in methane dynamics and methane flux measurements during sediment incubation were conducted to evaluate the immersion/emersion cycle and photosynthesis by MPB (micro phyto benthos) effect.

Methane in aquifers used for public supply in the United States

USGS Publications Warehouse

McMahon, Peter B.; Belitz, Kenneth; Barlow, Jeannie R.; Jurgens, Bryant

2017-01-01

In 2013 to 2015, 833 public supply wells in 15 Principal aquifers in the U.S. were sampled to identify which aquifers contained high methane concentrations (>1 mg/L) and determine the geologic, hydrologic, and geochemical conditions associated with high concentrations. This study represents the first national assessment of methane in aquifers used for public supply in the U.S. and, as such, advances the understanding of the occurrence and distribution of methane in groundwater nationally. Methane concentrations >1 and > 10 mg/L occurred in 6.7 and 1.1% of the samples, respectively. Most high concentrations occurred in aquifers in the Atlantic and Gulf Coastal Plain regions and upper Midwest. High methane concentrations were most commonly associated with Tertiary and younger aquifer sediments, old groundwater (>60 years), and concentrations of oxygen, nitrate-N, and sulfate <0.5 mg/L. Concentrations of methane were also positively correlated (p < 0.05) with dissolved organic carbon and ammonium. Case studies in Florida, Texas, and Iowa were used to explore how regional context from this data set could aid our understanding of local occurrences of methane in groundwater. Regional data for methane, Br/Cl ratios, sulfate, and other parameters helped identify mixing processes involving end members such as wastewater effluent-impacted groundwater, saline formation water, and pore water in glacial till that contributed methane to groundwater in some cases and supported methane oxidation in others.

Methane excess in Arctic surface water-triggered by sea ice formation and melting.

PubMed

Damm, E; Rudels, B; Schauer, U; Mau, S; Dieckmann, G

2015-11-10

Arctic amplification of global warming has led to increased summer sea ice retreat, which influences gas exchange between the Arctic Ocean and the atmosphere where sea ice previously acted as a physical barrier. Indeed, recently observed enhanced atmospheric methane concentrations in Arctic regions with fractional sea-ice cover point to unexpected feedbacks in cycling of methane. We report on methane excess in sea ice-influenced water masses in the interior Arctic Ocean and provide evidence that sea ice is a potential source. We show that methane release from sea ice into the ocean occurs via brine drainage during freezing and melting i.e. in winter and spring. In summer under a fractional sea ice cover, reduced turbulence restricts gas transfer, then seawater acts as buffer in which methane remains entrained. However, in autumn and winter surface convection initiates pronounced efflux of methane from the ice covered ocean to the atmosphere. Our results demonstrate that sea ice-sourced methane cycles seasonally between sea ice, sea-ice-influenced seawater and the atmosphere, while the deeper ocean remains decoupled. Freshening due to summer sea ice retreat will enhance this decoupling, which restricts the capacity of the deeper Arctic Ocean to act as a sink for this greenhouse gas.

Long open-path instrument for simultaneously monitoring of methane, CO2 and water vapor

NASA Astrophysics Data System (ADS)

Simeonov, Valentin; Parlange, Marc

2013-04-01

A new, long open-path instrument for monitoring of path-averaged methane, CO2 and water vapor concentrations will be presented. The instrument is built on the monostatic scheme (transceiver -distant retroreflector). A VCSEL with a central wavelength of 1654 nm is used as a light source. The receiver is built around a 20 cm Newtonian telescope. The design optical path length is 2000 m but can be further extended. To avoid distortions in the shape of the spectral lines caused by atmospheric turbulences they are scanned within 1 µs. The expected concentration resolution for the above mentioned path length is of the order of 2 ppb for methane, 100 ppb for CO2 and 100 ppm for water vapor. The instrument is developed at the Swiss Federal Institute of Technology - Lausanne (EPFL) Switzerland and will be used within the GAW+ CH program for long-term monitoring of background methane and CO2 concentrations in the Swiss Alps. The initial calibration validation tests at EPFL were completed in December 2012 and the instrument will be installed at the beginning of 2013 at the High Altitude Research Station Jungfraujoch (HARSJ). The HARSJ is located at 3580 m ASL and is one of the 24 global GAW stations. One of the goals of the project is to compare path-averaged to the ongoing point measurements of methane in order to identify possible influence of the station. Future deployments of a copy of the instrument include the Canadian arctic and Siberian wetlands. The instrument can be used for ground truthing of satellite observation as well.

Methane fluxes from tropical coastal lagoons surrounded bymangroves, Yucatán, Mexico

USGS Publications Warehouse

Chuang, Pei-Chuan; Young, Megan B.; Dale, Andrew W.; Miller, Laurence G.; Herrera-Silveira, Jorge A; Paytan, Adina

2017-01-01

Methane concentrations in the water column and emissions to the atmosphere were determined for three tropical coastal lagoons surrounded by mangrove forests on the Yucatán Peninsula, Mexico. Surface water dissolved methane was sampled at different seasons over a period of 2 years in areas representing a wide range of salinities and anthropogenic impacts. The highest surface water methane concentrations (up to 8378 nM) were measured in a polluted canal associated with Terminos Lagoon. In Chelem Lagoon, methane concentrations were typically lower, except in the polluted harbor area (1796 nM). In the relatively pristine Celestún Lagoon, surface water methane concentrations ranged from 41 to 2551 nM. Methane concentrations were negatively correlated with salinity in Celestún, while in Chelem and Terminos high methane concentrations were associated with areas of known pollution inputs, irrespective of salinity. The diffusive methane flux from surface lagoon water to the atmosphere ranged from 0.0023 to 15 mmol CH4 m−2 d−1. Flux chamber measurements revealed that direct methane release as ebullition was up to 3 orders of magnitude greater than measured diffusive flux. Coastal mangrove lagoons may therefore be an important natural source of methane to the atmosphere despite their relatively high salinity. Pollution inputs are likely to substantially enhance this flux. Additional statistically rigorous data collected globally are needed to better consider methane fluxes from mangrove-surrounded coastal areas in response to sea level changes and anthropogenic pollution in order to refine projections of future atmospheric methane budgets.

Methane fluxes from tropical coastal lagoons surrounded by mangroves, Yucatán, Mexico

NASA Astrophysics Data System (ADS)

Chuang, P.-C.; Young, M. B.; Dale, A. W.; Miller, L. G.; Herrera-Silveira, J. A.; Paytan, A.

2017-05-01

Methane concentrations in the water column and emissions to the atmosphere were determined for three tropical coastal lagoons surrounded by mangrove forests on the Yucatán Peninsula, Mexico. Surface water dissolved methane was sampled at different seasons over a period of 2 years in areas representing a wide range of salinities and anthropogenic impacts. The highest surface water methane concentrations (up to 8378 nM) were measured in a polluted canal associated with Terminos Lagoon. In Chelem Lagoon, methane concentrations were typically lower, except in the polluted harbor area (1796 nM). In the relatively pristine Celestún Lagoon, surface water methane concentrations ranged from 41 to 2551 nM. Methane concentrations were negatively correlated with salinity in Celestún, while in Chelem and Terminos high methane concentrations were associated with areas of known pollution inputs, irrespective of salinity. The diffusive methane flux from surface lagoon water to the atmosphere ranged from 0.0023 to 15 mmol CH4 m-2 d-1. Flux chamber measurements revealed that direct methane release as ebullition was up to 3 orders of magnitude greater than measured diffusive flux. Coastal mangrove lagoons may therefore be an important natural source of methane to the atmosphere despite their relatively high salinity. Pollution inputs are likely to substantially enhance this flux. Additional statistically rigorous data collected globally are needed to better consider methane fluxes from mangrove-surrounded coastal areas in response to sea level changes and anthropogenic pollution in order to refine projections of future atmospheric methane budgets.

Methane-oxidizing seawater microbial communities from an Arctic shelf

NASA Astrophysics Data System (ADS)

Uhlig, Christiane; Kirkpatrick, John B.; D'Hondt, Steven; Loose, Brice

2018-06-01

Marine microbial communities can consume dissolved methane before it can escape to the atmosphere and contribute to global warming. Seawater over the shallow Arctic shelf is characterized by excess methane compared to atmospheric equilibrium. This methane originates in sediment, permafrost, and hydrate. Particularly high concentrations are found beneath sea ice. We studied the structure and methane oxidation potential of the microbial communities from seawater collected close to Utqiagvik, Alaska, in April 2016. The in situ methane concentrations were 16.3 ± 7.2 nmol L-1, approximately 4.8 times oversaturated relative to atmospheric equilibrium. The group of methane-oxidizing bacteria (MOB) in the natural seawater and incubated seawater was > 97 % dominated by Methylococcales (γ-Proteobacteria). Incubations of seawater under a range of methane concentrations led to loss of diversity in the bacterial community. The abundance of MOB was low with maximal fractions of 2.5 % at 200 times elevated methane concentration, while sequence reads of non-MOB methylotrophs were 4 times more abundant than MOB in most incubations. The abundances of MOB as well as non-MOB methylotroph sequences correlated tightly with the rate constant (kox) for methane oxidation, indicating that non-MOB methylotrophs might be coupled to MOB and involved in community methane oxidation. In sea ice, where methane concentrations of 82 ± 35.8 nmol kg-1 were found, Methylobacterium (α-Proteobacteria) was the dominant MOB with a relative abundance of 80 %. Total MOB abundances were very low in sea ice, with maximal fractions found at the ice-snow interface (0.1 %), while non-MOB methylotrophs were present in abundances similar to natural seawater communities. The dissimilarities in MOB taxa, methane concentrations, and stable isotope ratios between the sea ice and water column point toward different methane dynamics in the two environments.

Consumption of methane by soils.

PubMed

Dueñas, C; Fernández, M C; Carretero, J; Pérez, M; Liger, E

1994-05-01

Measurements of the methane flux and methane concentration profiles in soil air are presented. The flux of methane from the soil is calculated by two methods: a) Direct by placing a static open chamber at the soil surface. b) Indirect, using the (222)Rn concentrations profile and the (222)Rn flux in the soil surface in parallel with the methane concentration ((222)Rn calibrated fluxes). The methane flux has been determined in two kinds of soils (sandy and loamy) in the surroundings of Málaga (SPAIN). The directly measured methane fluxes at all investigated sites is higher than methane fluxes derived from "Rn calibrated fluxes". Atmospheric methane is consumed by soils, mean direct flux to the atmosphere were - 0.33 g m(-2)yr-1. The direct methane flux is the same within the measuring error in sandy and loamy soils. The influence of the soil parameters on the methane flux indicates that microbial decomposition of methane is primarily controlled by the transport of methane.

Feasibility of atmospheric methane removal using methanotrophic biotrickling filters.

PubMed

Yoon, Sukhwan; Carey, Jeffrey N; Semrau, Jeremy D

2009-07-01

Methane is a potent greenhouse gas with a global warming potential ~23 times that of carbon dioxide. Here, we describe the modeling of a biotrickling filtration system composed of methane-consuming bacteria, i.e., methanotrophs, to assess the utility of these systems in removing methane from the atmosphere. Model results indicate that assuming the global average atmospheric concentration of methane, 1.7 ppmv, methane removal is ineffective using these methanotrophic biofilters as the methane concentration is too low to enable cell survival. If the concentration is increased to 500-6,000 ppmv, however, similar to that found above landfills and in concentrated animal feeding operations (factory farms), 4.98-35.7 tons of methane can be removed per biofilter per year assuming biotrickling filters of typical size (3.66 m in diameter and 11.5 m in height). Using reported ranges of capital, operational, and maintenance costs, the cost of the equivalent ton of CO(2) removal using these systems is $90-$910 ($2,070-$20,900 per ton of methane), depending on the influent concentration of methane and if heating is required. The use of methanotrophic biofilters for controlling methane emissions is technically feasible and, provided that either the costs of biofilter construction and operation are reduced or the value of CO(2) credits is increased, can also be economically attractive.

Global Methane Initiative

EPA Pesticide Factsheets

The Global Methane Initiative promotes cost-effective, near-term methane recovery through partnerships between developed and developing countries, with participation from the private sector, development banks, and nongovernmental organizations.

Quantification of methane fluxes from industrial sites using a combination of a tracer release method and a Gaussian model

NASA Astrophysics Data System (ADS)

Ars, S.; Broquet, G.; Yver-Kwok, C.; Wu, L.; Bousquet, P.; Roustan, Y.

2015-12-01

Greenhouse gas (GHG) concentrations keep on increasing in the atmosphere since industrial revolution. Methane (CH4) is the second most important anthropogenic GHG after carbon dioxide (CO2). Its sources and sinks are nowadays well identified however their relative contributions remain uncertain. The industries and the waste treatment emit an important part of the anthropogenic methane that is difficult to quantify because the sources are fugitive and discontinuous. A better estimation of methane emissions could help industries to adapt their mitigation's politic and encourage them to install methane recovery systems in order to reduce their emissions while saving money. Different methods exist to quantify methane emissions. Among them is the tracer release method consisting in releasing a tracer gas near the methane source at a well-known rate and measuring both their concentrations in the emission plume. The methane rate is calculated using the ratio of methane and tracer concentrations and the emission rate of the tracer. A good estimation of the methane emissions requires a good differentiation between the methane actually emitted by the site and the methane from the background concentration level, but also a good knowledge of the sources distribution over the site. For this purpose, a Gaussian plume model is used in addition to the tracer release method to assess the emission rates calculated. In a first step, the data obtained for the tracer during a field campaign are used to tune the model. Different model's parameterizations have been tested to find the best representation of the atmospheric dispersion conditions. Once these parameters are set, methane emissions are estimated thanks to the methane concentrations measured and a Bayesian inversion. This enables to adjust the position and the emission rate of the different methane sources of the site and remove the methane background concentration.

Methane source identification in Boston, Massachusetts using isotopic and ethane measurements

NASA Astrophysics Data System (ADS)

Down, A.; Jackson, R. B.; Plata, D.; McKain, K.; Wofsy, S. C.; Rella, C.; Crosson, E.; Phillips, N. G.

2012-12-01

Methane has substantial greenhouse warming potential and is the principle component of natural gas. Fugitive natural gas emissions could be a significant source of methane to the atmosphere. However, the cumulative magnitude of natural gas leaks is not yet well constrained. We used a combination of point source measurements and ambient monitoring to characterize the methane sources in the Boston urban area. We developed distinct fingerprints for natural gas and multiple biogenic methane sources based on hydrocarbon concentration and isotopic composition. We combine these data with periodic measurements of atmospheric methane and ethane concentration to estimate the fractional contribution of natural gas and biogenic methane sources to the cumulative urban methane flux in Boston. These results are used to inform an inverse model of urban methane concentration and emissions.

Estimation of methane concentrations and loads in groundwater discharge to Sugar Run, Lycoming County, Pennsylvania

USGS Publications Warehouse

Heilweil, Victor M.; Risser, Dennis W.; Conger, Randall W.; Grieve, Paul L.; Hynek, Scott A.

2014-01-01

A stream-sampling study was conducted to estimate methane concentrations and loads in groundwater discharge to a small stream in an active shale-gas development area of northeastern Pennsylvania. Grab samples collected from 15 streams in Bradford, Lycoming, Susquehanna, and Tioga Counties, Pa., during a reconnaissance survey in May and June 2013 contained dissolved methane concentrations ranging from less than the minimum reporting limit (1.0) to 68.5 micrograms per liter (µg/L). The stream-reach mass-balance method of estimating concentrations and loads of methane in groundwater discharge was applied to a 4-kilometer (km) reach of Sugar Run in Lycoming County, one of the four streams with methane concentrations greater than or equal to 5 µg/L. Three synoptic surveys of stream discharge and methane concentrations were conducted during base-flow periods in May, June, and November 2013. Stream discharge at the lower end of the reach was about 0.10, 0.04, and 0.02 cubic meters per second, respectively, and peak stream methane concentrations were about 20, 67, and 29 µg/L. In order to refine estimated amounts of groundwater discharge and locations where groundwater with methane discharges to the stream, the lower part of the study reach was targeted more precisely during the successive studies, with approximate spacing between stream sampling sites of 800 meters (m), 400 m, and 200 m, in May, June, and November, respectively. Samples collected from shallow piezometers and a seep near the location of the peak methane concentration measured in streamwater had groundwater methane concentrations of 2,300 to 4,600 µg/L. These field data, combined with one-dimensional stream-methane transport modeling, indicate groundwater methane loads of 1.8 ±0.8, 0.7 ±0.3, and 0.7 ±0.2 kilograms per day, respectively, discharging to Sugar Run. Estimated groundwater methane concentrations, based on the transport modeling, ranged from 100 to 3,200 µg/L. Although total methane load and the uncertainty in calculated loads both decreased with lower streamflow conditions and finer-resolution sampling in June and November, the higher loads during May could indicate seasonal variability in base flow. This is consistent with flowmeter measurements indicating that there was less inflow occurring at lower streamflow conditions during June and November.

Polarized electrode enhances biological direct interspecies electron transfer for methane production in upflow anaerobic bioelectrochemical reactor.

PubMed

Feng, Qing; Song, Young-Chae; Yoo, Kyuseon; Kuppanan, Nanthakumar; Subudhi, Sanjukta; Lal, Banwari

2018-08-01

The influence of polarized electrodes on the methane production, which depends on the sludge concentration, was investigated in upflow anaerobic bioelectrochemical (UABE) reactor. When the polarized electrode was placed in the bottom zone with a high sludge concentration, the methane production was 5.34 L/L.d, which was 53% higher than upflow anaerobic sludge blanket (UASB) reactor. However, the methane production was reduced to 4.34 L/L.d by placing the electrode in the upper zone of the UABE reactor with lower sludge concentration. In the UABE reactor, the methane production was mainly improved by the enhanced biological direct interspecies electron transfer (bDIET) pathway, and the methane production via the electrode was a minor fraction of less than 4% of total methane production. The polarized electrodes that placed in the bottom zone with a high sludge concentration enhance the bDIET for methane production in the UABE reactor and greatly improve the methane production. Copyright © 2018. Published by Elsevier Ltd.

Seasonal and interannual variability in wetland methane emissions simulated by CLM4Me' and CAM-chem and comparisons to observations of concentrations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meng, L.; Paudel, R.; Hess, P. G. M.

Understanding the temporal and spatial variation of wetland methane emissions is essential to the estimation of the global methane budget. Our goal for this study is three-fold: (i) to evaluate the wetland methane fluxes simulated in two versions of the Community Land Model, the Carbon-Nitrogen (CN; i.e., CLM4.0) and the Biogeochemistry (BGC; i.e., CLM4.5) versions using the methane emission model CLM4Me' so as to determine the sensitivity of the emissions to the underlying carbon model; (ii) to compare the simulated atmospheric methane concentrations to observations, including latitudinal gradients and interannual variability so as to determine the extent to which themore » atmospheric observations constrain the emissions; (iii) to understand the drivers of seasonal and interannual variability in atmospheric methane concentrations. Simulations of the transport and removal of methane use the Community Atmosphere Model with chemistry (CAM-chem) model in conjunction with CLM4Me' methane emissions from both CN and BGC simulations and other methane emission sources from literature. In each case we compare model-simulated atmospheric methane concentration with observations. In addition, we simulate the atmospheric concentrations based on the TransCom wetland and rice paddy emissions derived from a different terrestrial ecosystem model, Vegetation Integrative Simulator for Trace gases (VISIT). Our analysis indicates CN wetland methane emissions are higher in the tropics and lower at high latitudes than emissions from BGC. In CN, methane emissions decrease from 1993 to 2004 while this trend does not appear in the BGC version. In the CN version, methane emission variations follow satellite-derived inundation wetlands closely. However, they are dissimilar in BGC due to its different carbon cycle. CAM-chem simulations with CLM4Me' methane emissions suggest that both prescribed anthropogenic and predicted wetlands methane emissions contribute substantially to seasonal and interannual variability in atmospheric methane concentration. Simulated atmospheric CH 4 concentrations in CAM-chem are highly correlated with observations at most of the 14 measurement stations evaluated with an average correlation between 0.71 and 0.80 depending on the simulation (for the period of 1993–2004 for most stations based on data availability). Our results suggest that different spatial patterns of wetland emissions can have significant impacts on Northern and Southern hemisphere (N–S) atmospheric CH 4 concentration gradients and growth rates. In conclusion, this study suggests that both anthropogenic and wetland emissions have significant contributions to seasonal and interannual variations in atmospheric CH 4 concentrations. However, our analysis also indicates the existence of large uncertainties in terms of spatial patterns and magnitude of global wetland methane budgets, and that substantial uncertainty comes from the carbon model underlying the methane flux modules.« less

Seasonal and interannual variability in wetland methane emissions simulated by CLM4Me' and CAM-chem and comparisons to observations of concentrations

DOE PAGES

Meng, L.; Paudel, R.; Hess, P. G. M.; ...

2015-07-03

Understanding the temporal and spatial variation of wetland methane emissions is essential to the estimation of the global methane budget. Our goal for this study is three-fold: (i) to evaluate the wetland methane fluxes simulated in two versions of the Community Land Model, the Carbon-Nitrogen (CN; i.e., CLM4.0) and the Biogeochemistry (BGC; i.e., CLM4.5) versions using the methane emission model CLM4Me' so as to determine the sensitivity of the emissions to the underlying carbon model; (ii) to compare the simulated atmospheric methane concentrations to observations, including latitudinal gradients and interannual variability so as to determine the extent to which themore » atmospheric observations constrain the emissions; (iii) to understand the drivers of seasonal and interannual variability in atmospheric methane concentrations. Simulations of the transport and removal of methane use the Community Atmosphere Model with chemistry (CAM-chem) model in conjunction with CLM4Me' methane emissions from both CN and BGC simulations and other methane emission sources from literature. In each case we compare model-simulated atmospheric methane concentration with observations. In addition, we simulate the atmospheric concentrations based on the TransCom wetland and rice paddy emissions derived from a different terrestrial ecosystem model, Vegetation Integrative Simulator for Trace gases (VISIT). Our analysis indicates CN wetland methane emissions are higher in the tropics and lower at high latitudes than emissions from BGC. In CN, methane emissions decrease from 1993 to 2004 while this trend does not appear in the BGC version. In the CN version, methane emission variations follow satellite-derived inundation wetlands closely. However, they are dissimilar in BGC due to its different carbon cycle. CAM-chem simulations with CLM4Me' methane emissions suggest that both prescribed anthropogenic and predicted wetlands methane emissions contribute substantially to seasonal and interannual variability in atmospheric methane concentration. Simulated atmospheric CH 4 concentrations in CAM-chem are highly correlated with observations at most of the 14 measurement stations evaluated with an average correlation between 0.71 and 0.80 depending on the simulation (for the period of 1993–2004 for most stations based on data availability). Our results suggest that different spatial patterns of wetland emissions can have significant impacts on Northern and Southern hemisphere (N–S) atmospheric CH 4 concentration gradients and growth rates. In conclusion, this study suggests that both anthropogenic and wetland emissions have significant contributions to seasonal and interannual variations in atmospheric CH 4 concentrations. However, our analysis also indicates the existence of large uncertainties in terms of spatial patterns and magnitude of global wetland methane budgets, and that substantial uncertainty comes from the carbon model underlying the methane flux modules.« less

Experimental co-digestion of corn stalk and vermicompost to improve biogas production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen Guangyin; Zheng Zheng, E-mail: zzhenghj@fudan.edu.c; Department of Environmental Science and Engineering, Fudan University, Shanghai 200433

2010-10-15

Anaerobic co-digestion of corn stalk and vermicompost (VC) as well as mono-digestion of corn stalk were investigated. Batch mono-digestion experiments were performed at 35 {+-} 1 {sup o}C and initial total solid loading (TSL) ranged from 1.2% to 6.0%. Batch co-digestion experiments were performed at 35 {+-} 1 {sup o}C and initial TSL of 6% with VC proportions ranged from 20% to 80% of total solid (TS). For mono-digestion of corn stalk, a maximum methane yield of 217.60 {+-} 13.87 mL/g TS{sub added} was obtained at initial TSL of 4.8%, and acidification was found at initial TSL of 6.0% withmore » the lowest pH value of 5.10 on day 4. Co-digestion improved the methane yields by 4.42-58.61% via enhancing volatile fatty acids (VFAs) concentration and pH value compared with mono-digestion of corn stalk. The maximum biogas yield of 410.30 {+-} 11.01 mL/g TS{sub added} and methane yield of 259.35 {+-} 13.85 mL/g TS{sub added} were obtained for 40% VC addition. Structure analysis by X-ray diffractometry (XRD) showed that the lowest crystallinity of 35.04 of digested corn stalk was obtained from co-digestion with 40% VC, which decreased 29.4% compared to 49.6 obtained from un-treated corn stalk. It is concluded that co-digestion with VC is beneficial for improving biodigestibility and methane yield from corn stalk.« less

Exhaled methane concentration profiles during exercise on an ergometer

PubMed Central

Szabó, A; Ruzsanyi, V; Unterkofler, K; Mohácsi, Á; Tuboly, E; Boros, M; Szabó, G; Hinterhuber, H; Amann, A

2016-01-01

Exhaled methane concentration measurements are extensively used in medical investigation of certain gastrointestinal conditions. However, the dynamics of endogenous methane release is largely unknown. Breath methane profiles during ergometer tests were measured by means of a photoacoustic spectroscopy based sensor. Five methane-producing volunteers (with exhaled methane level being at least 1 ppm higher than room air) were measured. The experimental protocol consisted of 5 min rest—15 min pedalling (at a workload of 75 W)—5 min rest. In addition, hemodynamic and respiratory parameters were determined and compared to the estimated alveolar methane concentration. The alveolar breath methane level decreased considerably, by a factor of 3–4 within 1.5 min, while the estimated ventilation-perfusion ratio increased by a factor of 2–3. Mean pre-exercise and exercise methane concentrations were 11.4 ppm (SD:7.3) and 2.8 ppm (SD:1.9), respectively. The changes can be described by the high sensitivity of exhaled methane to ventilationperfusion ratio and are in line with the Farhi equation. PMID:25749807

Some seasonal characteristics in atmospheric methane concentration in the beginning of the XXI century

NASA Astrophysics Data System (ADS)

Vinogradova, Anna; Ginzburg, Alexander; Fedorova, Evgeniya

2010-05-01

Global average value of atmospheric methane concentrations have been increasing during the XX century, but this growth nearly stopped with the beginning of the 2000th. Such "stable" situation is the proper time for studying the seasonal cycle and extreme changes of air methane concentration. One of the most interesting periods for such investigations is autumn and winter 2006/07 [1] when a number of weather abnormalities (warm air temperature up to above 0°C, almost permanent cloudiness and absence of snow cover, and so on) in Moscow region created very specific conditions for air methane existence. Temporal variations in air methane concentration within the Moscow city have been studied using the data of observations at 12 stations of Moscow municipal environmental monitoring agency "Mosecomonitoring" in 2004-2008 [2]. It was found that near-surface air concentration of methane was much higher this time than few years before and after. The values of cold season methane concentrations in Moscow region have been compared with similar data measured in the North of Kola Peninsula (at WMO GAW station "Teriberka"), in the Sankt Petersburg region (the two stations of Roshydromet), in Finland and Hungary (the stations of NOAA GMD Carbon Cycle Sampling Network). Winter maxima (more or less) of methane concentrations were revealed almost each year at all these stations, but not everywhere they were simultaneous and as high as those had been found in Moscow. The reasons of winter 2006/07 high methane concentrations in Moscow and other regions of Northern Eurasia may be special weather conditions which could cause both decrease of air methane sinks and increase of methane emissions from natural and anthropogenic sources. Perhaps, the late growth of global atmospheric methane concentration after 2007 [3] was partly produced by those seasonal anomalies in the Northern Hemisphere. References: 1. E. Fedorova, A. Ginzburg, A. Vinogradova. Seasonal variations of atmospheric methane and hot winter 2006-2007 // Geophys. Res. Abstracts, 2007, Vol. 9, SRef-ID: 1607-7962/gra/EDU2007-A-06049. 2. A.A. Vinogradova, E.I. Fedorova, I.B. Belikov, et al. Temporal variations in carbon dioxide and methane concentrations under urban conditions // Izv., Atmospheric and Oceanic Physics, 2007, Vol. 43, No. 5, pp. 599-611. 3. Rigby M., Prinn R.G., Fraser P.J., et al. Renewed growth of atmospheric methane // Geophys. Res. Lett., 2008, Vol. 35. doi: 10,1029/2008GL036037

Modeling of breath methane concentration profiles during exercise on an ergometer*

PubMed Central

Szabó, Anna; Unterkofler, Karl; Mochalski, Pawel; Jandacka, Martin; Ruzsanyi, Vera; Szabó, Gábor; Mohácsi, Árpád; Teschl, Susanne; Teschl, Gerald; King, Julian

2016-01-01

We develop a simple three compartment model based on mass balance equations which quantitatively describes the dynamics of breath methane concentration profiles during exercise on an ergometer. With the help of this model it is possible to estimate the endogenous production rate of methane in the large intestine by measuring breath gas concentrations of methane. PMID:26828421

Monitoring fossil fuel sources of methane in Australia

NASA Astrophysics Data System (ADS)

Loh, Zoe; Etheridge, David; Luhar, Ashok; Hibberd, Mark; Thatcher, Marcus; Noonan, Julie; Thornton, David; Spencer, Darren; Gregory, Rebecca; Jenkins, Charles; Zegelin, Steve; Leuning, Ray; Day, Stuart; Barrett, Damian

2017-04-01

CSIRO has been active in identifying and quantifying methane emissions from a range of fossil fuel sources in Australia over the past decade. We present here a history of the development of our work in this domain. While we have principally focused on optimising the use of long term, fixed location, high precision monitoring, paired with both forward and inverse modelling techniques suitable either local or regional scales, we have also incorporated mobile ground surveys and flux calculations from plumes in some contexts. We initially developed leak detection methodologies for geological carbon storage at a local scale using a Bayesian probabilistic approach coupled to a backward Lagrangian particle dispersion model (Luhar et al. JGR, 2014), and single point monitoring with sector analysis (Etheridge et al. In prep.) We have since expanded our modelling techniques to regional scales using both forward and inverse approaches to constrain methane emissions from coal mining and coal seam gas (CSG) production. The Surat Basin (Queensland, Australia) is a region of rapidly expanding CSG production, in which we have established a pair of carefully located, well-intercalibrated monitoring stations. These data sets provide an almost continuous record of (i) background air arriving at the Surat Basin, and (ii) the signal resulting from methane emissions within the Basin, i.e. total downwind methane concentration (comprising emissions including natural geological seeps, agricultural and biogenic sources and fugitive emissions from CSG production) minus background or upwind concentration. We will present our latest results on monitoring from the Surat Basin and their application to estimating methane emissions.

Optimizing feeding composition and carbon-nitrogen ratios for improved methane yield during anaerobic co-digestion of dairy, chicken manure and wheat straw.

PubMed

Wang, Xiaojiao; Yang, Gaihe; Feng, Yongzhong; Ren, Guangxin; Han, Xinhui

2012-09-01

This study investigated the possibilities of improving methane yield from anaerobic digestion of multi-component substrates, using a mixture of dairy manure (DM), chicken manure (CM) and wheat straw (WS), based on optimized feeding composition and the C/N ratio. Co-digestion of DM, CM and WS performed better in methane potential than individual digestion. A larger synergetic effect in co-digestion of DM, CM and WS was found than in mixtures of single manures with WS. As the C/N ratio increased, methane potential initially increased and then declined. C/N ratios of 25:1 and 30:1 had better digestion performance with stable pH and low concentrations of total ammonium nitrogen and free NH(3). Maximum methane potential was achieved with DM/CM of 40.3:59.7 and a C/N ratio of 27.2:1 after optimization using response surface methodology. The results suggested that better performance of anaerobic co-digestion can be fulfilled by optimizing feeding composition and the C/N ratio. Copyright © 2012 Elsevier Ltd. All rights reserved.

Analysis of Influence of Goaf Sealing from Tailgate On the Methane Concentration at the Outlet from the Longwall

NASA Astrophysics Data System (ADS)

Tutak, Magdalena; Brodny, Jaroslaw

2017-12-01

One of the most common and most dangerous gas hazards in underground coal mine is methane hazard. Formation of dangerous, explosive concentrations of methane occurs the most often in the region of crossing of longwall with the ventilation gallery. Particularly it applies to longwalls ventilated in „U from bounds” system. Outflow of gases from the goaf to the tailgate takes place through the boundary surfaces of this sidewalk with goaf. Main cause of this process is a phenomenon of air filtration through the goaf with caving. This filtration is a result of migration of the part of ventilation air stream supplied to the longwall. This air is released into the goaf on the entire longwall length; however, its greater amount gets to the goaf with caving space at the crossing of maingate with exploitation longwall. Albeit, the biggest outflow of air mixture and gases from the goaf occurs in top gate in upper corner of the longwall. This is a result of pressure difference in this region. This phenomenon causes that to the space of heading besides the air also other gases present in the goaf, mainly methane, are released. Methane is an explosive gas. Most often boundaries of explosive mixtures of methane, air and inert gases are described by the so-called Coward triangle explosion. Within the limits of the occurrence of the concentration of explosive methane explosion initials may be endogenous fire, blasting or sparks arising from friction of moving lumps of rock. Therefore, in order to decrease its concertation in this region, by limiting its outflow from the goaf with caving different actions are taken. One of such action is sealing of goaf from top gate side. Analysis of impact of sealing of these goaf on the methane concentration at the outlet of longwall is main aim of studies researches. Model of tested region, together with boundary conditions (including parameters of flowing air and the methane content) was developed on the base of real data from one of the exploitation longwalls. In the studies it was assumed that measurement of sealing of goaf (their isolation) will be permeability coefficient of sealing layer. Based on this impact of this coefficient value on methane concertation at outlet from the longwall was determined. As a result of performed analysis also other physical parameters of air stream flowing through the tested region were determined, also dependent on the degree of sealing of goaf. Simulation tests were carried out with use of finite volume method. Obtained results clearly indicate, that by a proper selection of degree of sealing of goaf with caving, one can have significant influence on the air stream parameters in the region of upper corner of longwall.

Factors Controlling Methane in Arctic Lakes of Southwest Greenland.

PubMed

Northington, Robert M; Saros, Jasmine E

2016-01-01

We surveyed 15 lakes during the growing season of 2014 in Arctic lakes of southwest Greenland to determine which factors influence methane concentrations in these systems. Methane averaged 2.5 μmol L-1 in lakes, but varied a great deal across the landscape with lakes on older landscapes farther from the ice sheet margin having some of the highest values of methane reported in lakes in the northern hemisphere (125 μmol L-1). The most important factors influencing methane in Greenland lakes included ionic composition (SO4, Na, Cl) and chlorophyll a in the water column. DOC concentrations were also related to methane, but the short length of the study likely underestimated the influence and timing of DOC on methane concentrations in the region. Atmospheric methane concentrations are increasing globally, with freshwater ecosystems in northern latitudes continuing to serve as potentially large sources in the future. Much less is known about how freshwater lakes in Greenland fit in the global methane budget compared to other, more well-studied areas of the Arctic, hence our work provides essential data for a more complete view of this rapidly changing region.

Thermodynamic properties and diffusion of water + methane binary mixtures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shvab, I.; Sadus, Richard J., E-mail: rsadus@swin.edu.au

2014-03-14

Thermodynamic and diffusion properties of water + methane mixtures in a single liquid phase are studied using NVT molecular dynamics. An extensive comparison is reported for the thermal pressure coefficient, compressibilities, expansion coefficients, heat capacities, Joule-Thomson coefficient, zero frequency speed of sound, and diffusion coefficient at methane concentrations up to 15% in the temperature range of 298–650 K. The simulations reveal a complex concentration dependence of the thermodynamic properties of water + methane mixtures. The compressibilities, heat capacities, and diffusion coefficients decrease with increasing methane concentration, whereas values of the thermal expansion coefficients and speed of sound increase. Increasing methanemore » concentration considerably retards the self-diffusion of both water and methane in the mixture. These effects are caused by changes in hydrogen bond network, solvation shell structure, and dynamics of water molecules induced by the solvation of methane at constant volume conditions.« less

Monitoring Production of Methane from Spills of Gasoline at UST Release Sites (Boston, MA)

EPA Science Inventory

Anaerobic biodegradation of the BTEX compounds can produce substantial concentrations of methane in ground water at gasoline spill sites. This methane can escape the ground water, move through the unsaturated zone and potentially produce explosive concentrations of methane in c...

Optimization of hydrolysis and volatile fatty acids production from sugarcane filter cake: Effects of urea supplementation and sodium hydroxide pretreatment.

PubMed

Janke, Leandro; Leite, Athaydes; Batista, Karla; Weinrich, Sören; Sträuber, Heike; Nikolausz, Marcell; Nelles, Michael; Stinner, Walter

2016-01-01

Different methods for optimization the anaerobic digestion (AD) of sugarcane filter cake (FC) with a special focus on volatile fatty acids (VFA) production were studied. Sodium hydroxide (NaOH) pretreatment at different concentrations was investigated in batch experiments and the cumulative methane yields fitted to a dual-pool two-step model to provide an initial assessment on AD. The effects of nitrogen supplementation in form of urea and NaOH pretreatment for improved VFA production were evaluated in a semi-continuously operated reactor as well. The results indicated that higher NaOH concentrations during pretreatment accelerated the AD process and increased methane production in batch experiments. Nitrogen supplementation resulted in a VFA loss due to methane formation by buffering the pH value at nearly neutral conditions (∼ 6.7). However, the alkaline pretreatment with 6g NaOH/100g FCFM improved both the COD solubilization and the VFA yield by 37%, mainly consisted by n-butyric and acetic acids. Copyright © 2015 Elsevier Ltd. All rights reserved.

Anaerobic digestion characteristics of pig manures depending on various growth stages and initial substrate concentrations in a scaled pig farm in Southern China.

PubMed

Zhang, Wanqin; Lang, Qianqian; Wu, Shubiao; Li, Wei; Bah, Hamidou; Dong, Renjie

2014-03-01

The characteristics of anaerobic digestion of pig manure from different growth stages were investigated. According to growth stage, batch experiments were performed using gestating sow manure (GSM), swine nursery with post-weaned piglet manure (SNM), growing fattening manure (GFM) and mixed manure (MM) as substrates at four substrate concentrations (40, 50, 65 and 80gVS/L) under mesophilic conditions. The maximum methane yields of MM, SNM, GSM and GFM were 354.7, 328.7, 282.4 and 263.5mLCH4/gVSadded, respectively. Volatile fatty acids/total inorganic carbon (VFA/TIC) ratio increased from 0.10 to 0.89 when loading increased from 40 to 80gVS/L for GFM. The modified Gompertz model shows a better fit to the experimental results than the first order model with a lower difference between measured and predicted methane yields. The kinetic parameters indicated that the methane production curve on the basis of differences in biodegradability of the pig manure at different growth stages. Copyright © 2014 Elsevier Ltd. All rights reserved.

Origin of methane and sources of high concentrations in Los Angeles groundwater

USGS Publications Warehouse

Kulongoski, Justin; McMahon, Peter B.; Land, Michael; Wright, Michael; Johnson, Theodore; Landon, Matthew K.

2018-01-01

In 2014, samples from 37 monitoring wells at 17 locations, within or near oil fields, and one site >5 km from oil fields, in the Los Angeles Basin, California, were analyzed for dissolved hydrocarbon gas isotopes and abundances. The wells sample a variety of depths of an aquifer system composed of unconsolidated and semiconsolidated sediments under various conditions of confinement. Concentrations of methane in groundwater samples ranged from 0.002 to 150 mg/L—some of the highest concentrations reported in a densely populated urban area. The δ13C and δ2H of the methane ranged from −80.8 to −45.5 per mil (‰) and −249.8 to −134.9‰, respectively, and, along with oxidation‐reduction processes, helped to identify the origin of methane as microbial methanogenesis and CO2 reduction as its main formation pathway. The distribution of methane concentrations and isotopes is consistent with the high concentrations of methane in Los Angeles Basin groundwater originating from relatively shallow microbial production in anoxic or suboxic conditions. Source of the methane is the aquifer sediments rather than the upward migration or leakage of thermogenic methane associated with oil fields in the basin.

Origin of Methane and Sources of High Concentrations in Los Angeles Groundwater

NASA Astrophysics Data System (ADS)

Kulongoski, J. T.; McMahon, P. B.; Land, M.; Wright, M. T.; Johnson, T. A.; Landon, M. K.

2018-03-01

In 2014, samples from 37 monitoring wells at 17 locations, within or near oil fields, and one site >5 km from oil fields, in the Los Angeles Basin, California, were analyzed for dissolved hydrocarbon gas isotopes and abundances. The wells sample a variety of depths of an aquifer system composed of unconsolidated and semiconsolidated sediments under various conditions of confinement. Concentrations of methane in groundwater samples ranged from 0.002 to 150 mg/L—some of the highest concentrations reported in a densely populated urban area. The δ13C and δ2H of the methane ranged from -80.8 to -45.5 per mil (‰) and -249.8 to -134.9‰, respectively, and, along with oxidation-reduction processes, helped to identify the origin of methane as microbial methanogenesis and CO2 reduction as its main formation pathway. The distribution of methane concentrations and isotopes is consistent with the high concentrations of methane in Los Angeles Basin groundwater originating from relatively shallow microbial production in anoxic or suboxic conditions. Source of the methane is the aquifer sediments rather than the upward migration or leakage of thermogenic methane associated with oil fields in the basin.

A Non-Steady-State Condition in Sediments at the Gashydrate Stability Boundary off West Spitsbergen: Evidence for Gashydrate Dissociation or Just Dynamic Methane Transport?

NASA Astrophysics Data System (ADS)

Treude, T.; Krause, S.; Bertics, V. J.; Steinle, L.; Niemann, H.; Liebetrau, V.; Feseker, T.; Burwicz, E.; Krastel, S.; Berndt, C.

2014-12-01

In 2008, a large area with several hundred methane plumes was discovered along the West Spitsbergen continental margin at water depths between 150 and 400 m (Westbrook et al. 2009, GRL 36, doi:10.1029/2009GL039191). Many of the observed plumes were located at the boundary of gas hydrate stability (~400 m water depth). It was speculated that the methane escape at this depth was correlated with gas hydrate destabilization caused by recent increases in water temperatures recorded in this region. In a later study, geochemical analyses of authigenic carbonates and modeling of heat flow data combined with seasonal changes in water temperature demonstrated that the methane seeps were active already prior to industrial warming but that the gas hydrate system nevertheless reacts very sensitive to even seasonal temperature changes (Berndt et al. 2014, Science 343: 284-287). Here, we report about a methane seep site at the gas hydrate stability boundary (394 m water depth) that features unusual geochemical profiles indicative for non-steady state conditions. Sediment was recovered with a gravity corer (core length 210 cm) and samples were analyzed to study porewater geochemistry, methane concentration, authigenic carbonates, and microbial activity. Porewater profiles revealed two zones of sulfate-methane transition at 50 and 200 cm sediment depth. The twin zones were confirmed by a double peaking in sulfide, total alkalinity, anaerobic oxidation of methane, and sulfate reduction. δ18O values sharply increased from around -2.8 ‰ between 0 and 126 cm to -1.2 ‰ below 126 cm sediment depth. While U/Th isotope measurements of authigenic seep carbonates that were collected from different depths of the core illustrated that methane seepage must be occurring at this site since at least 3000 years, the biogeochemical profiles suggest that methane flux must have been altered recently. By applying a multi-phase reaction-transport model using known initial parameters from the study site (e.g. water depth, temperature profile, salinity, and sediment surface concentrations of CH4, SO4, DIC, and POC) were able to show that the observed twin sulfate-methane transition zones are an ephemeral phenomenon occurring during increase of methane production in the sediment, which can be introduced by, e.g., gas hydrate dissociation.

Nonequilibrium Thermodynamics of Hydrate Growth on a Gas-Liquid Interface

NASA Astrophysics Data System (ADS)

Fu, Xiaojing; Cueto-Felgueroso, Luis; Juanes, Ruben

2018-04-01

We develop a continuum-scale phase-field model to study gas-liquid-hydrate systems far from thermodynamic equilibrium. We design a Gibbs free energy functional for methane-water mixtures that recovers the isobaric temperature-composition phase diagram under thermodynamic equilibrium conditions. The proposed free energy is incorporated into a phase-field model to study the dynamics of hydrate formation on a gas-liquid interface. We elucidate the role of initial aqueous concentration in determining the direction of hydrate growth at the interface, in agreement with experimental observations. Our model also reveals two stages of hydrate growth at an interface—controlled by a crossover in how methane is supplied from the gas and liquid phases—which could explain the persistence of gas conduits in hydrate-bearing sediments and other nonequilibrium phenomena commonly observed in natural methane hydrate systems.

Nonequilibrium Thermodynamics of Hydrate Growth on a Gas-Liquid Interface.

PubMed

Fu, Xiaojing; Cueto-Felgueroso, Luis; Juanes, Ruben

2018-04-06

We develop a continuum-scale phase-field model to study gas-liquid-hydrate systems far from thermodynamic equilibrium. We design a Gibbs free energy functional for methane-water mixtures that recovers the isobaric temperature-composition phase diagram under thermodynamic equilibrium conditions. The proposed free energy is incorporated into a phase-field model to study the dynamics of hydrate formation on a gas-liquid interface. We elucidate the role of initial aqueous concentration in determining the direction of hydrate growth at the interface, in agreement with experimental observations. Our model also reveals two stages of hydrate growth at an interface-controlled by a crossover in how methane is supplied from the gas and liquid phases-which could explain the persistence of gas conduits in hydrate-bearing sediments and other nonequilibrium phenomena commonly observed in natural methane hydrate systems.

Temporal variations of methane concentration and isotopic composition in groundwater of the St. Lawrence Lowlands, eastern Canada

NASA Astrophysics Data System (ADS)

Rivard, Christine; Bordeleau, Geneviève; Lavoie, Denis; Lefebvre, René; Malet, Xavier

2018-03-01

Dissolved methane concentrations in shallow groundwater are known to vary both spatially and temporally. The extent of these variations is poorly documented although this knowledge is critical for distinguishing natural fluctuations from anthropogenic impacts stemming from oil and gas activities. This issue was addressed as part of a groundwater research project aiming to assess the risk of shale gas development for groundwater quality over a 500-km2 area in the St. Lawrence Lowlands (Quebec, Canada). A specific study was carried out to define the natural variability of methane concentrations and carbon and hydrogen isotope ratios in groundwater, as dissolved methane is naturally ubiquitous in aquifers of this area. Monitoring was carried out over a period of up to 2.5 years in seven monitoring wells. Results showed that for a given well, using the same sampling depth and technique, methane concentrations can vary over time from 2.5 to 6 times relative to the lowest recorded value. Methane isotopic composition, which is a useful tool to distinguish gas origin, was found to be stable for most wells, but varied significantly over time in the two wells where methane concentrations are the lowest. The use of concentration ratios, as well as isotopic composition of methane and dissolved inorganic carbon (DIC), helped unravel the processes responsible for these variations. This study indicates that both methane concentrations and isotopic composition, as well as DIC isotopes, should be regularly monitored over at least 1 year to establish their potential natural variations prior to hydrocarbon development.

30 CFR 75.351 - Atmospheric monitoring systems.

Code of Federal Regulations, 2013 CFR

2013-07-01

... methane concentration at any sensor reaches the alert level as specified in § 75.351(i). These signals... carbon monoxide, smoke, or methane concentration at any sensor reaches the alarm level as specified in... methane concentration at any sensor reaches the alarm level as specified in § 75.351(i). These signals...

30 CFR 75.351 - Atmospheric monitoring systems.

Code of Federal Regulations, 2014 CFR

2014-07-01

... methane concentration at any sensor reaches the alert level as specified in § 75.351(i). These signals... carbon monoxide, smoke, or methane concentration at any sensor reaches the alarm level as specified in... methane concentration at any sensor reaches the alarm level as specified in § 75.351(i). These signals...

30 CFR 75.351 - Atmospheric monitoring systems.

Code of Federal Regulations, 2012 CFR

2012-07-01

... methane concentration at any sensor reaches the alert level as specified in § 75.351(i). These signals... carbon monoxide, smoke, or methane concentration at any sensor reaches the alarm level as specified in... methane concentration at any sensor reaches the alarm level as specified in § 75.351(i). These signals...

The design of a PC-based real-time system for monitoring Methane and Oxygen concentration in biogas production

NASA Astrophysics Data System (ADS)

Yantidewi, M.; Muntini, M. S.; Deta, U. A.; Lestari, N. A.

2018-03-01

Limited fossil fuels nowadays trigger the development of alternative energy, one of which is biogas. Biogas is one type of bioenergy in the form of fermented gases of organic materials such as animal waste. The components of gases present in biogas and affect the biogas production are various, such as methane and oxygen. The biogas utilization will be more optimal if both gases concentration (in this case is methane and oxygen concentration) can be monitored. Therefore, this research focused on designing the monitoring system of methane and oxygen concentration in biogas production in real-time. The results showed that the instrument system was capable of monitoring and recording the data of gases (methane and oxygen) concentration in biogas production in every second.

Factors Controlling Methane in Arctic Lakes of Southwest Greenland

PubMed Central

2016-01-01

We surveyed 15 lakes during the growing season of 2014 in Arctic lakes of southwest Greenland to determine which factors influence methane concentrations in these systems. Methane averaged 2.5 μmol L-1 in lakes, but varied a great deal across the landscape with lakes on older landscapes farther from the ice sheet margin having some of the highest values of methane reported in lakes in the northern hemisphere (125 μmol L-1). The most important factors influencing methane in Greenland lakes included ionic composition (SO4, Na, Cl) and chlorophyll a in the water column. DOC concentrations were also related to methane, but the short length of the study likely underestimated the influence and timing of DOC on methane concentrations in the region. Atmospheric methane concentrations are increasing globally, with freshwater ecosystems in northern latitudes continuing to serve as potentially large sources in the future. Much less is known about how freshwater lakes in Greenland fit in the global methane budget compared to other, more well-studied areas of the Arctic, hence our work provides essential data for a more complete view of this rapidly changing region. PMID:27454863

Study of methanogenesis during bioutilization of plant residuals

NASA Astrophysics Data System (ADS)

Ilyin, V. K.; Korniushenkova, I. N.; Starkova, L. V.; Lauriniavichius, K. S.

2005-02-01

The waste management strategy for the future should meet the benefits of human safety, respect principles of planet ecology, and compatibility with other habitability systems. For these purposes waste management technologies relevant to application of the biodegradation properties of bacteria are of great value. Biological treatment method is based on the biodegradation of organic substances by various microorganisms. The objectives of our study were: to evaluate the effectiveness of microbial biodegradation of vegetable non-edible residual, using artificial inoculum, and to study the peculiarities of biogas, and possibilities of optimizing or reducing the share of methane. The diminution rate of organic gained 76% from initial mass within 9 days of fermentation. The biogas production achieved 46 l/kg of substrate. The microbial studies of biodegradation process revealed the following peculiarities: (i) gradual quantitative increase of Lactobacillus sp. (from 103 to 105 colony-forming units (CFU) per ml); (ii) activation of Clostridia sp. (from 102 to 10 4 CFU/ml); and (iii) elimination of aerobic conventional pathogens (Enterobacteriaceae, Protea sp., Staphylococci). Chromatography analysis revealed the constant presence of carbon dioxide (up to 90.9%). The methane content measures revealed traces 0.1-0.4%. However, when we optimized the methane production in "boiling layer" using methanogenic granules, the amount of methane in biogas reached 80-90%. Based on the results obtained the artificial inoculum was created which was capable of initiating biodegradation of vegetable wastes. This inoculum consisted of active sludge adapted to wastes mixed with excretea of insects which consume plant wastes. Using this inoculum the biodegradation process takes less time than that using active sludge. Regulation of methane concentration from traces to 90% may be achieved by adding methane reactor to the plant digester.

Distribution and Rate of Methane Oxidation in Sediments of the Florida Everglades †

PubMed Central

King, Gary M.; Roslev, Peter; Skovgaard, Henrik

1990-01-01

Rates of methane emission from intact cores were measured during anoxic dark and oxic light and dark incubations. Rates of methane oxidation were calculated on the basis of oxic incubations by using the anoxic emissions as an estimate of the maximum potential flux. This technique indicated that methane oxidation consumed up to 91% of the maximum potential flux in peat sediments but that oxidation was negligible in marl sediments. Oxygen microprofiles determined for intact cores were comparable to profiles measured in situ. Thus, the laboratory incubations appeared to provide a reasonable approximation of in situ activities. This was further supported by the agreement between measured methane fluxes and fluxes predicted on the basis of methane profiles determined by in situ sampling of pore water. Methane emissions from peat sediments, oxygen concentrations and penetration depths, and methane concentration profiles were all sensitive to light-dark shifts as determined by a combination of field and laboratory analyses. Methane emissions were lower and oxygen concentrations and penetration depths were higher under illuminated than under dark conditions; the profiles of methane concentration changed in correspondence to the changes in oxygen profiles, but the estimated flux of methane into the oxic zone changed negligibly. Sediment-free, root-associated methane oxidation showed a pattern similar to that for methane oxidation in the core analyses: no oxidation was detected for roots growing in marl sediment, even for roots of Cladium jamaicense, which had the highest activity for samples from peat sediments. The magnitude of the root-associated oxidation rates indicated that belowground plant surfaces may not markedly increase the total capacity for methane consumption. However, the data collectively support the notion that the distribution and activity of methane oxidation have a major impact on the magnitude of atmospheric fluxes from the Everglades. PMID:16348299

Methane distributions and transports in the nocturnal boundary layer at a rural station

NASA Astrophysics Data System (ADS)

Schäfer, Klaus; Zeeman, Matthias; Brosy, Caroline; Münkel, Christoph; Fersch, Benjamin; Mauder, Matthias; Emeis, Stefan

2016-10-01

To investigate the methane distributions and transports, the role of related atmospheric processes by determination of vertical profiles of wind, turbulence, temperature and humidity as well as nocturnal boundary layer (NBL) height and the quantification of methane emissions at local and plot scale the so-called ScaleX-campaign was performed in a pre-alpine observatory in Southern Germany from 01 June until 31 July 2015. The following measurements from the ground up to the free troposphere were performed: layering of the atmosphere by a ceilometer (Vaisala CL51); temperature, wind, turbulence profiles from 50 m up to 500 m by a Radio-Acoustic Sounding System (RASS, Metek GmbH); temperature, humidity profiles in situ by a hexacopter; methane farm emissions by two open-path laser spectrometers (Boreal GasFinder2); methane concentrations in situ (Los Gatos DLT-100) with tubes in 0.3 m agl and 5 sampling heads; and methane soil emissions by a big chamber (10 m length, 2.60 m width, up to 0.61 m height) with a plastic cover. The methane concentrations near the surface show a daily variation with a maximum and a frequent double-peak structure during night-time. Analysis of the variation of the nocturnal methane concentration together with the hexacopter and RASS data indicates that the first peak in the nocturnal methane concentration is probably due to local cooling and stabilization which keeps the methane emissions from the soil near the ground. The second peak seems to be due to advection of methane-enriched air which had formed in the environment of the nearby farm yards. These dairy farm emissions were determined by up-wind and down-wind open-path concentration measurements, turbulence data from an EC station nearby and Backward Lagrangian Simulation (WindTrax software). The methane fluxes at plot scale (big chamber) are characterized by emissions at water saturated grassland patches, by an exponential decrease of these emissions during grassland drying, and by an uptake of methane at dry grassland. Highest methane concentrations are found with lowest NBL heights which were determined from the ceilometer monitoring (correlation coefficient 0.56).

Temporal variation of aerobic methane oxidation over a tidal cycle in a wetland of northern Taiwan.

NASA Astrophysics Data System (ADS)

Lee, T. Y.; Wang, P. L.; Lin, L. H.

2017-12-01

Aerobic methanotrophy plays an important role in controlling methane emitted from wetlands. However, the activity of aerobic methanotrophy regulated by temporal fluctuation of oxygen and methane supply in tidal wetlands is not well known. This study aims to examine the dynamics of methane fluxes and potential aerobic methane consumption rates in a tidal wetland of northern Taiwan, where the variation of environmental characteristics, such as sulfate and methane concentration in pore water has been demonstrated during a tidal cycle. Two field campaigns were carried out in December of 2016 and March of 2017. Fluxes of methane emission, methane concentrations in surface sediments and oxygen profiles were measured at different tidal phases. Besides, batch incubations were conducted on surface sediments in order to quantify potential microbial methane consumption rates and to derive the kinetic parameters for aerobic methanotrophy. Our results demonstrated temporal changes of the surface methane concentration and the methane emission flux during a tidal cycle, while the oxygen flux into the sediment was kept at a similar magnitude. The methane flux was low when the surface was exposed for both shortest and longest periods of time. The potential aerobic methane oxidation rate was high for sample collected from the surface sediments exposed the longest. No correlation could be found between the potential aerobic methane oxidation rate and either the oxygen downward flux or methane emission flux. The decoupled relationships between these observed rates and fluxes suggest that, rather than aerobic methanotrophy, heterotrophic respirations exert a profound control on oxygen flux, and the methane emission is not only been affected by methane consumption but also methane production at depths. The maximum potential rate and the half saturation concentration determined from the batch incubations were high for the surface sediments collected in low tide, suggesting that aerobic methanotrophy could be modulated to reach peak activity once the influence of saline water is reduced to a low level.

Late Holocene methane rise caused by orbitally controlled increase in tropical sources.

PubMed

Singarayer, Joy S; Valdes, Paul J; Friedlingstein, Pierre; Nelson, Sarah; Beerling, David J

2011-02-03

Considerable debate surrounds the source of the apparently 'anomalous' increase of atmospheric methane concentrations since the mid-Holocene (5,000 years ago) compared to previous interglacial periods as recorded in polar ice core records. Proposed mechanisms for the rise in methane concentrations relate either to methane emissions from anthropogenic early rice cultivation or an increase in natural wetland emissions from tropical or boreal sources. Here we show that our climate and wetland simulations of the global methane cycle over the last glacial cycle (the past 130,000 years) recreate the ice core record and capture the late Holocene increase in methane concentrations. Our analyses indicate that the late Holocene increase results from natural changes in the Earth's orbital configuration, with enhanced emissions in the Southern Hemisphere tropics linked to precession-induced modification of seasonal precipitation. Critically, our simulations capture the declining trend in methane concentrations at the end of the last interglacial period (115,000-130,000 years ago) that was used to diagnose the Holocene methane rise as unique. The difference between the two time periods results from differences in the size and rate of regional insolation changes and the lack of glacial inception in the Holocene. Our findings also suggest that no early agricultural sources are required to account for the increase in methane concentrations in the 5,000 years before the industrial era.

Methane oxidation in Saanich Inlet during summer stratification

NASA Technical Reports Server (NTRS)

Ward, B. B.; Kilpatrick, K. A.; Wopat, A. E.; Minnich, E. C.; Lidstrom, M. E.

1989-01-01

Saanich Inlet, British Columbia, an fjord on the southeast coast of Vancouver Island, typically stratifies in summer, leading to the formation of an oxic-anoxic interface in the water column and accumulation of methane in the deep water. The results of methane concentration measurements in the water column of the inlet at various times throughout the summer months in 1983 are presented. Methane gradients and calculated diffusive fluxes across the oxic-anoxic interface increased as the summer progressed. Methane distribution and consumption in Saanich Inlet were studied in more detail during August 1986. At this time, a typical summer stratification with an oxic-anoxic interface around 140 m was present. At the interface, steep gradients in nutrient concentrations, bacterial abundance and methane concentration were observed. Methane oxidation was detected in the aerobic surface waters and in the anaerobic deep layer, but highest rates occurred in a narrow layer at the oxic-anoxic interface. Estimated methane oxidation rates were suffcient to consume 100 percent of the methane provided by diffusive flux from the anoxic layer. Methane oxidation is thus a mechanism whereby atmospheric flux from anoxic waters is minimized.

Methane Sources and Migration Mechanisms in the Shallow Trinity Aquifer in Parker and Hood Counties, Texas - a Noble Gas Analysis

NASA Astrophysics Data System (ADS)

Wen, T.; Castro, C.; Nicot, J. P.; Hall, C. M.; Mickler, P. J.; Darvari, R.

2016-12-01

The presence of elevated methane in groundwaters within the Barnett Shale footprint in Parker and Hood counties, Texas has caused public concern that hydrocarbon production may facilitate migration of natural gas into a critical groundwater resource. This study places constraints on the source of methane in these groundwaters by analyzing water and stray gas data from groundwater wells and gas production wells from both the Barnett Shale and Strawn Group for methane content and noble gases, both of crustal and atmospheric origin. Particular emphasis is given to the atmospheric heavier noble gases 84Kr and 132Xe, which are significantly less affected by the presence of excess air, commonly present in modern Texas groundwaters (e.g., [1]). Dissolved methane concentrations are positively correlated with crustal 4He, 21Ne and 40Ar and suggest that noble gases and methane in these groundwaters originate from a common source, likely the Strawn Group, which the sampled aquifer overlies unconformably. This finding is further supported by the noble gas isotopic signature of stray gas when compared to the gas isotopic signatures of both Barnett Shale and the Strawn Group. In contrast to most samples, four groundwater wells with the highest methane concentrations unequivocally show heavy depletion of the atmospheric noble gases 20Ne, 36Ar, 84Kr and 132Xe with respect to freshwater recharge equilibrated with the atmosphere (ASW). This is consistent with predicted noble gas concentrations in a residual water phase in contact with a gas phase with initial ASW composition at 18°C-25°C, assuming a closed-system and suggest a highly localized gas source. All these four wells, without exception, tap into the Strawn Group and it is likely that shallow gas accumulations, as they are known to exist, were reached. Additionally, lack of correlation between 84Kr/36Ar and 132Xe/36Ar fractionation levels and distance to the nearest production wells does not support the notion that methane present in these groundwater wells migrated from nearby production wells, either conventional or using hydraulic fracturing techniques. Lack of correlation between the latter and 4He/20Ne further supports these findings. [1] Castro et al. (2007) EPSL 257, 170-187.

Evaluating the Effects of Surface Properties on Methane Detection with the Airborne Visible/Infrared Imaging Spectrometer Next Generation (AVIRIS-NG)

NASA Astrophysics Data System (ADS)

Ayasse, A.; Thorpe, A. K.; Roberts, D. A.; Aubrey, A. D.; Dennison, P. E.; Thompson, D. R.; Frankenberg, C.

2016-12-01

Atmospheric methane has been increasing since the industrial revolution and is thought to be responsible for about 25% of global radiative forcing (Hofman et al., 2006; Montzka et al., 2011). Given the importance of methane to global climate, it is essential that we identify methane sources to better understand the proportion of emissions coming from various sectors. Recently the Airborne Visible-Infrared Imaging Spectrometer Next Generation (AVIRIS-NG) has proven to be a valuable instrument for mapping methane plumes (Frankenberg et al., 2016; Thorpe et al., 2016; Thompson et al., 2015). However, it is important to determine how land cover and albedo affect the ability of AVIRIS-NG to detect methane. This study aims to quantify the effect these surface properties have on detection. To do so we are using a synthetic AVIRIS-NG image that has multiple land cover types, albedos, and methane concentrations and applying the Cluster Tunes Matched Filter (CTMF) algorithm (Funk et al. 2001, Thorpe et al., 2013) to detect methane enhancements within the image. CTMF results are compared to the surface properties to characterize how different surface properties affect detection. We will also evaluate the effect of surface properties with examples of methane plumes observed from oil fields and manure ponds in the San Joaquin Valley of California, two important methane sources (Figure 1). Initial results suggest that darker surfaces, such as water absent sun glint, will make detecting the methane signal challenging, while bright surfaces such as dry soils produce a much clearer signal. Characterizing the effect of surface properties on methane detection is of increasing importance given the application of this technology will likely expand to map methane across a diverse range of emission sources. Figure 1. AVIRIS-NG image acquired Apr. 29, 2015. True color image with a superimposed methane plume from a manure pond. Bright surfaces, such as the dirt road, provide a better surface for retrievals than dark surfaces, such as the vegetation.

World-wide increase in tropospheric methane, 1978-1983

NASA Technical Reports Server (NTRS)

Blake, D. R.; Rowland, F. S.

1986-01-01

Techniques used to assess methane concentration in the troposphere are described, and data obtained during the period from 1978 to 1983 are presented in detail. Tropospheric methane concentrations in remote locations averaged a yearly world-wide increase of 0.018 + or - 0.002 parts per million by volume (ppmv). Average world-wide tropospheric concentration of methane in dry air was 1.625 ppmv at the end of 1983 measured against an NBS standard certified as 0.97 ppmv. Contributing to this steady increase in methane concentration are increases in the source strengths from cattle and rice fields, which in turn result from CO, CH4 and HO coupling. Among the physical and chemical effects is an increase in greenhouse warming of about 0.04 C per decade.

Influence of rumen protozoa on methane emission in ruminants: a meta-analysis approach.

PubMed

Guyader, J; Eugène, M; Nozière, P; Morgavi, D P; Doreau, M; Martin, C

2014-11-01

A meta-analysis was conducted to evaluate the effects of protozoa concentration on methane emission from ruminants. A database was built from 59 publications reporting data from 76 in vivo experiments. The experiments included in the database recorded methane production and rumen protozoa concentration measured on the same groups of animals. Quantitative data such as diet chemical composition, rumen fermentation and microbial parameters, and qualitative information such as methane mitigation strategies were also collected. In the database, 31% of the experiments reported a concomitant reduction of both protozoa concentration and methane emission (g/kg dry matter intake). Nearly all of these experiments tested lipids as methane mitigation strategies. By contrast, 21% of the experiments reported a variation in methane emission without changes in protozoa numbers, indicating that methanogenesis is also regulated by other mechanisms not involving protozoa. Experiments that used chemical compounds as an antimethanogenic treatment belonged to this group. The relationship between methane emission and protozoa concentration was studied with a variance-covariance model, with experiment as a fixed effect. The experiments included in the analysis had a within-experiment variation of protozoa concentration higher than 5.3 log10 cells/ml corresponding to the average s.e.m. of the database for this variable. To detect potential interfering factors for the relationship, the influence of several qualitative and quantitative secondary factors was tested. This meta-analysis showed a significant linear relationship between methane emission and protozoa concentration: methane (g/kg dry matter intake)=-30.7+8.14×protozoa (log10 cells/ml) with 28 experiments (91 treatments), residual mean square error=1.94 and adjusted R 2=0.90. The proportion of butyrate in the rumen positively influenced the least square means of this relationship.

Tracking Dissolved Methane Concentrations near Active Seeps and Gas Hydrates: Sea of Japan.

NASA Astrophysics Data System (ADS)

Snyder, G. T.; Aoki, S.; Matsumoto, R.; Tomaru, H.; Owari, S.; Nakajima, R.; Doolittle, D. F.; Brant, B.

2015-12-01

A number of regions in the Sea of Japan are known for active gas venting and for gas hydrate exposures on the sea floor. In this investigation we employed several gas sensors mounted on a ROV in order to determine the concentrations of dissolved methane in the water near these sites. Methane concentrations were determined during two-second intervals throughout each ROV deployment during the cruise. The methane sensor deployments were coupled with seawater sampling using Niskin bottles. Dissolved gas concentrations were later measured using gas chromatography in order to compare with the sensor results taken at the same time. The observed maximum dissolved methane concentrations were much lower than saturation values, even when the ROV manipulators were in contact with gas hydrate. Nonetheless, dissolved concentrations did reach several thousands of nmol/L near gas hydrate exposures and gas bubbles, more than two orders of magnitude over the instrumental detection limits. Most of the sensors tested were able to detect dissolved methane concentrations as low as 10 nmol/L which permitted detection when the ROV approached methane plume sites, even from several tens of meters above the sea floor. Despite the low detection limits, the methane sensors showed variable response times when returning to low-background seawater (~5nM). For some of the sensors, the response time necessary to return to background values occurred in a matter of minutes, while for others it took several hours. Response time, as well as detection limit, should be an important consideration when selecting methane sensors for ROV or AUV investigations. This research was made possible, in part, through funding provided by the Japanese Ministry of Economy, Trade and Industry (METI).

Bedrock, Borehole, and Water-Quality Characterization of a Methane-Producing Water Well in Wolfeboro, New Hampshire

USGS Publications Warehouse

Degnan, James R.; Walsh, Gregory J.; Flanagan, Sarah M.; Burruss, Robert A.

2008-01-01

In August 2004, a commercial drill rig was destroyed by ignition of an explosive gas released during the drilling of a domestic well in granitic bedrock in Tyngsborough, MA. This accident prompted the Massachusetts Department of Environmental Protection (MassDEP) to sample the well water for dissolved methane - a possible explosive fuel. Water samples collected from the Tyngsborough domestic well in 2004 by the MassDEP contained low levels of methane gas (Pierce and others, 2007). When the U.S. Geological Survey (USGS) sampled this well in 2006, there was no measurable amount of methane remaining in the well water (Pierce and others, 2007). Other deep water wells in nearby south-central New Hampshire have been determined to have high concentrations of naturally occurring methane (David Wunsch, New Hampshire State Geologist, 2004, written commun.). Studying additional wells in New England crystalline bedrock aquifers that produce methane may help to understand the origin of methane in crystalline bedrock. Domestic well NH-WRW-37 was chosen for this study because it is a relatively deep well completed in crystalline bedrock, it is not affected by known anthropogenic sources of methane, and it had the highest known natural methane concentration (15.5 mg/L, U.S. Geological Survey, 2007) measured in a study described by Robinson and others (2004). This well has been in use since it was drilled in 1997, and it was originally selected for study in 2000 as part of a 30 well network, major-aquifer study by the USGS' New England Coastal Basins (NECB) study unit of the National Water-Quality Assessment (NAWQA) Program. Dissolved methane in drinking water is not considered an ingestion health hazard, although the occurrence in ground water is a concern because, as a gas, its buildup in confined spaces can cause asphyxiation, fire, or explosion hazards (Mathes and White, 2006). Methane occurrence in the fractured crystalline bedrock is not widely reported or well understood. Borehole-geophysical surveys, bedrock outcrop observations, and water-quality analyses were used to define the geologic and hydrologic characteristics of NH-WRW-37. Collection of additional information on the hydraulic and geologic characteristics of the fractured bedrock and on water quality was initiated in an attempt to understand the setting where methane gas occurs in the bedrock ground water. The origin of dissolved methane in this and other wells in New Hampshire is the subject of ongoing investigations by the State of New Hampshire, the New Hampshire Geological Survey and the USGS.

Use of diverse geochemical data sets to determine sources and sinks of nitrate and methane in groundwater, Garfield County, Colorado, 2009

USGS Publications Warehouse

McMahon, P.B.; Thomas, J.C.; Hunt, A.G.

2011-01-01

Previous water-quality assessments reported elevated concentrations of nitrate and methane in water from domestic wells screened in shallow zones of the Wasatch Formation, Garfield County, Colorado. In 2009, the U.S. Geological Survey, in cooperation with the Colorado Department of Public Health and Environment, analyzed samples collected from 26 domestic wells for a diverse set of geochemical tracers for the purpose of determining sources and sinks of nitrate and methane in groundwater from the Wasatch Formation. Nitrate concentrations ranged from less than 0.04 to 6.74 milligrams per liter as nitrogen (mg/L as N) and were significantly lower in water samples with dissolved-oxygen concentrations less than 0.5 mg/L than in samples with dissolved-oxygen concentrations greater than or equal to 0.5 mg/L. Chloride/bromide mass ratios and tracers of groundwater age (tritium, chlorofluorocarbons, and sulfur hexafluoride) indicate that septic-system effluent or animal waste was a source of nitrate in some young groundwater (less than 50 years), although other sources such as fertilizer also may have contributed nitrate to the groundwater. Nitrate and nitrogen gas (N2) concentrations indicate that denitrification was the primary sink for nitrate in anoxic groundwater, removing 99 percent of the original nitrate content in some samples that had nitrate concentrations greater than 10 mg/L as N at the time of recharge. Methane concentrations ranged from less than 0.0005 to 32.5 mg/L and were significantly higher in water samples with dissolved-oxygen concentrations less than 0.5 mg/L than in samples with dissolved-oxygen concentrations greater than or equal to 0.5 mg/L. High methane concentrations (greater than 1 mg/L) in some samples were biogenic in origin and appeared to be derived from a relatively deep source on the basis of helium concentrations and isotopic data. One such sample had water-isotopic and major-ion compositions similar to that of produced water from the underlying Mesaverde Group, which was the primary natural-gas producing interval in the study area. Methane in the Mesaverde Group was largely thermogenic in origin so biogenic methane in the sample probably was derived from deeper zones in the Wasatch Formation. The primary methane sink in the aquifer appeared to be methane oxidation on the basis of dissolved-oxygen and methane concentrations and methane isotopic data. The diverse data sets used in this study enhance previous water-quality assessments by providing new and more complete insights into the sources and sinks of nitrate and methane in groundwater. Field measurements of dissolved oxygen in groundwater were useful indicators of the Wasatch Formation's vulnerability to nitrate and methane contamination or enrichment. Results from this study also provide new evidence for the movement of water, ions, and gases into the shallow Wasatch Formation from sources such as the Mesaverde Group and deeper Wasatch Formation.

Methanosarcina as the dominant aceticlastic methanogens during mesophilic anaerobic digestion of putrescible waste.

PubMed

Vavilin, Vasily A; Qu, Xian; Mazéas, Laurent; Lemunier, Melanie; Duquennoi, Christian; He, Pinjing; Bouchez, Theodore

2008-11-01

Taking into account isotope (13)C value a mathematical model was developed to describe the dynamics of methanogenic population during mesophilic anaerobic digestion of putrescible solid waste and waste imitating Chinese municipal solid waste. Three groups of methanogens were considered in the model including unified hydrogenotrophic methanogens and two aceticlastic methanogens Methanosaeta sp. and Methanosarcina sp. It was assumed that Methanosaeta sp. and Methanosarcina sp. are inhibited by high volatile fatty acids concentration. The total organic and inorganic carbon concentrations, methane production, methane and carbon dioxide partial pressures as well as the isotope (13)C incorporation in PSW and CMSW were used for the model calibration and validation. The model showed that in spite of the high initial biomass concentration of Methanosaeta sp. Methanosarcina sp. became the dominant aceticlastic methanogens in the system. This prediction was confirmed by FISH. It is concluded that Methanosarcina sp. forming multicellular aggregates may resist to inhibition by volatile fatty acids (VFAs) because a slow diffusion rate of the acids limits the VFA concentrations inside the Methanosarcina sp. aggregates.

Geochemical and geological factors controlling the spatial distribution of sulfate-methane transition zone in the Ría de Vigo (NW Spain)

NASA Astrophysics Data System (ADS)

Martínez-Carreño, N.; García-Gil, S.; Cartelle, V.; de Blas, E.; Ramírez-Pérez, A. M.; Insua, T. L.

2017-05-01

High-resolution seismic profiles, gravity core analysis and radiocarbon data have been used to identify the factors behind the methane production and free gas accumulation in the Ría de Vigo. Lithological and geochemical parameters (sulfate and methane concentration) from seventeen gravity cores were analyzed to characterize the sediment of the ria. The distribution of methane-charged sediments is mainly controlled by the quantity and quality of organic matter. Geochemical analyses reveal minimum methane concentrations ranging between 1 μM and 1 mM in sediments located outside the acoustic gas field, while gas-bearing sediments, show methane concentrations up to 5 mM. A shallowing of the sulfate-methane transition zone (SMTZ) is observed from the outer to the inner area of the ria. The presence of methane in the sulfate reduction zone (SRZ) likely to reflect the existence of methylotropic methanogenesis and/or migration processes of deeper methane gas in the sediments of the Ría de Vigo. The presence of an 'anomalous' high-sulfate concentration layer below the SMTZ in the inner and middle area of the ria, is attributed to the intrusion of sulfate-rich waters from adjacent areas that could be transported laterally through more porous layers.

Formate oxidation-driven calcium carbonate precipitation by Methylocystis parvus OBBP.

PubMed

Ganendra, Giovanni; De Muynck, Willem; Ho, Adrian; Arvaniti, Eleni Charalampous; Hosseinkhani, Baharak; Ramos, Jose Angel; Rahier, Hubert; Boon, Nico

2014-08-01

Microbially induced carbonate precipitation (MICP) applied in the construction industry poses several disadvantages such asammonia release to the air and nitric acid production. An alternative MICP from calcium formate by Methylocystis parvus OBBP is presented here to overcome these disadvantages. To induce calcium carbonate precipitation, M. parvus was incubated at different calcium formate concentrations and starting culture densities. Up to 91.4% ± 1.6% of the initial calcium was precipitated in the methane-amended cultures compared to 35.1% ± 11.9% when methane was not added. Because the bacteria could only utilize methane for growth, higher culture densities and subsequently calcium removals were exhibited in the cultures when methane was added. A higher calcium carbonate precipitate yield was obtained when higher culture densities were used but not necessarily when more calcium formate was added. This was mainly due to salt inhibition of the bacterial activity at a high calcium formate concentration. A maximum 0.67 ± 0.03 g of CaCO3 g of Ca(CHOOH)2(-1) calcium carbonate precipitate yield was obtained when a culture of 10(9) cells ml(-1) and 5 g of calcium formate liter(-)1 were used. Compared to the current strategy employing biogenic urea degradation as the basis for MICP, our approach presents significant improvements in the environmental sustainability of the application in the construction industry.

Formate Oxidation-Driven Calcium Carbonate Precipitation by Methylocystis parvus OBBP

PubMed Central

Ganendra, Giovanni; De Muynck, Willem; Ho, Adrian; Arvaniti, Eleni Charalampous; Hosseinkhani, Baharak; Ramos, Jose Angel; Rahier, Hubert

2014-01-01

Microbially induced carbonate precipitation (MICP) applied in the construction industry poses several disadvantages such as ammonia release to the air and nitric acid production. An alternative MICP from calcium formate by Methylocystis parvus OBBP is presented here to overcome these disadvantages. To induce calcium carbonate precipitation, M. parvus was incubated at different calcium formate concentrations and starting culture densities. Up to 91.4% ± 1.6% of the initial calcium was precipitated in the methane-amended cultures compared to 35.1% ± 11.9% when methane was not added. Because the bacteria could only utilize methane for growth, higher culture densities and subsequently calcium removals were exhibited in the cultures when methane was added. A higher calcium carbonate precipitate yield was obtained when higher culture densities were used but not necessarily when more calcium formate was added. This was mainly due to salt inhibition of the bacterial activity at a high calcium formate concentration. A maximum 0.67 ± 0.03 g of CaCO3 g of Ca(CHOOH)2−1 calcium carbonate precipitate yield was obtained when a culture of 109 cells ml−1 and 5 g of calcium formate liter−1 were used. Compared to the current strategy employing biogenic urea degradation as the basis for MICP, our approach presents significant improvements in the environmental sustainability of the application in the construction industry. PMID:24837386

Age of Sulfate Methane Transition Zone Determined by Modelling Barium Sulfate Growth

NASA Astrophysics Data System (ADS)

Lin, S.; Wang, W. C.; Lien, K. L.; Liu, C. C.; Fan, L. F.

2017-12-01

Methane seep to the sediment/water interface could initiate anaerobic methane oxidation (AOM) with subsequent build up of chemosynthetic community, carbonate, pyrite and a number of other authigenic mineral formation. Determination the duration, sequence and time of methane seeps are keys to understand how methane seep to the environment and degree of alteration to the vicinity area. However, limited method existed in defining time of methane seep since there are some known problems involving typical dating methods, i.e. old carbon on C14 of fossil test or authigenic carbonate, thorium from surrounding matrix on U/Th authigenic carbonate dating. In this study, we have employed barium determination method (Dickens, 2001) to model timing of methane seep at two locations in the South China Sea. Our objective is to compare timing of the barium accumulation near the sulfate methane transition zone (SMTZ) on these two different locations and to seek if a similar mechanism driving the methane seep at two locations far apart. Dissolved barium, total sediment barium and aluminum were measured as well as pore water sulfate, and sediment pyrite concentrations. Time for the barium sulfate accumulation is calculated by: T = C/F, C= ∫ I x p x (1-Ø) Our results show that SMTZ is stabilized at each site for a duration of about 4000-5000 years. AOM process have been active at both sites at about the same time. In conjunction, pyrite also accumulated at a depth near the SMTZ as a result of methane oxidation. This result show that AOM could stay at the SMTZ for a relatively long period of time, on a scale of thousands of years.

Biogeochemical Carbon Cycling in Ultrabasic Reducing Springs in Sonoma County, CA

NASA Astrophysics Data System (ADS)

Cotton, J. M.; Morrill, P.; Johnson, O.; Nealson, K. H.; Sherwood Lollar, B.; Eigenbrode, J.; Fogel, M.

2006-12-01

Dissolved gases in the ultrabasic spring waters from The Cedars in Sonoma County, CA were analyzed for concentrations and carbon and hydrogen isotopic ratios in order to determine the geobiological processes occurring in this extreme environment of unknown biological activity. The ultrabasic, highly reducing conditions unique to these springs result from local serpentinization. Gases bubbling from the springs are mainly composed of methane, hydrogen, and nitrogen. Serpentinization is a process characteristic of early Earth, Mars and Titan that is thought to produce abiogenic hydrocarbons as well as provide geochemical energy for chemolithotrophic life. Methane, CO2, hydrogen and nitrogen were detected in the aqueous phases. Earlier work indicated that the primary source of the methane in the free gases bubbling from the springs was associated with microbial fermentation a suspected source of the dissolved methane. Here we report, a negative, linear correlation between concentrations of CO2 and methane that is an indicator of microbial anaerobic methane oxidation taking place in the ultrabasic waters. Furthermore, as the concentrations of methane decrease, the concentration of CO2 increases and both reactant and product become 13C-enriched. These observations are consistent with microbial oxidation of methane, suggesting a biogeochemical carbon cycle exists in these springs. We hypothesize that one group of microbes is breaking down organic matter by a process of fermentation to produce methane and CO2. The CO2 dissolves in the basic springs, while most of the methane escapes solution. The residual dissolved methane undergoes a conversion to CO2 by anaerobic methane oxidation.

Quantifying the loss of methane through secondary gas mass transport (or 'slip') from a micro-porous membrane contactor applied to biogas upgrading.

PubMed

McLeod, Andrew; Jefferson, Bruce; McAdam, Ewan J

2013-07-01

Secondary gas transport during the separation of a binary gas with a micro-porous hollow fibre membrane contactor (HMFC) has been studied for biogas upgrading. In this application, the loss or 'slip' of the secondary gas (methane) during separation is a known concern, specifically since methane possesses the intrinsic calorific value. Deionised (DI) water was initially used as the physical solvent. Under these conditions, carbon dioxide (CO2) and methane (CH4) absorption were dependent upon liquid velocity (V(L)). Whilst the highest CO2 flux was recorded at high V(L), selectivity towards CO2 declined due to low residence times and a diminished gas-side partial pressure, and resulted in slip of approximately 5.2% of the inlet methane. Sodium hydroxide was subsequently used as a comparative chemical absorption solvent. Under these conditions, CO2 mass transfer increased by increasing gas velocity (VG) which is attributed to the excess of reactive hydroxide ions present in the solvent, and the fast conversion of dissolved CO2 to carbonate species reinitiating the concentration gradient at the gas-liquid interface. At high gas velocities, CH4 slip was reduced to 0.1% under chemical conditions. Methane slip is therefore dependent upon whether the process is gas phase or liquid phase controlled, since methane mass transport can be adequately described by Henry's law within both physical and chemical solvents. The addition of an electrolyte was found to further retard CH4 absorption via the salting out effect. However, their applicability to physical solvents is limited since electrolytic concentration similarly impinges upon the solvents' capacity for CO2. This study illustrates the significance of secondary gas mass transport, and furthermore demonstrates that gas-phase controlled systems are recommended where greater selectivity is required. Copyright © 2013 Elsevier Ltd. All rights reserved.

Methane Exchange in a Coastal Fen in the First Year after Flooding - A Systems Shift

PubMed Central

Hahn, Juliane; Köhler, Stefan; Glatzel, Stephan; Jurasinski, Gerald

2015-01-01

Background Peatland restoration can have several objectives, for example re-establishing the natural habitat, supporting unique biodiversity attributes or re-initiating key biogeochemical processes, which can ultimately lead to a reduction in greenhouse gas (GHG) emissions. Every restoration measure, however, is itself a disturbance to the ecosystem. Methods Here, we examine an ecosystem shift in a coastal fen at the southern Baltic Sea which was rewetted by flooding. The analyses are based on one year of bi-weekly closed chamber measurements of methane fluxes gathered at spots located in different vegetation stands. During measurement campaigns, we recorded data on water levels, peat temperatures, and chemical properties of peat water. In addition we analyzed the first 20 cm of peat before and after flooding for dry bulk density (DBD), content of organic matter and total amounts of carbon (C), nitrogen (N), sulfur (S), and other nutrients. Results Rewetting turned the site from a summer dry fen into a shallow lake with water levels up to 0.60 m. We observed a substantial die-back of vegetation, especially in stands of sedges (Carex acutiformis Ehrh). Concentrations of total organic carbon and nitrogen in the peat water, as well as dry bulk density and concentrations of C, N and S in the peat increased. In the first year after rewetting, the average annual exchange of methane amounted to 0.26 ± 0.06 kg m-2. This is equivalent to a 190-times increase in methane compared to pre-flooding conditions. Highest methane fluxes occurred in sedge stands which suffered from the heaviest die-back. None of the recorded environmental variables showed consistent relationships with the amounts of methane exchanged. Conclusions Our results suggest that rewetting projects should be monitored not only with regard to vegetation development but also with respect to biogeochemical conditions. Further, high methane emissions that likely occur directly after rewetting by flooding should be considered when forecasting the overall effect of rewetting on GHG exchange. PMID:26461916

Methane Exchange in a Coastal Fen in the First Year after Flooding--A Systems Shift.

PubMed

Hahn, Juliane; Köhler, Stefan; Glatzel, Stephan; Jurasinski, Gerald

2015-01-01

Peatland restoration can have several objectives, for example re-establishing the natural habitat, supporting unique biodiversity attributes or re-initiating key biogeochemical processes, which can ultimately lead to a reduction in greenhouse gas (GHG) emissions. Every restoration measure, however, is itself a disturbance to the ecosystem. Here, we examine an ecosystem shift in a coastal fen at the southern Baltic Sea which was rewetted by flooding. The analyses are based on one year of bi-weekly closed chamber measurements of methane fluxes gathered at spots located in different vegetation stands. During measurement campaigns, we recorded data on water levels, peat temperatures, and chemical properties of peat water. In addition we analyzed the first 20 cm of peat before and after flooding for dry bulk density (DBD), content of organic matter and total amounts of carbon (C), nitrogen (N), sulfur (S), and other nutrients. Rewetting turned the site from a summer dry fen into a shallow lake with water levels up to 0.60 m. We observed a substantial die-back of vegetation, especially in stands of sedges (Carex acutiformis Ehrh). Concentrations of total organic carbon and nitrogen in the peat water, as well as dry bulk density and concentrations of C, N and S in the peat increased. In the first year after rewetting, the average annual exchange of methane amounted to 0.26 ± 0.06 kg m-2. This is equivalent to a 190-times increase in methane compared to pre-flooding conditions. Highest methane fluxes occurred in sedge stands which suffered from the heaviest die-back. None of the recorded environmental variables showed consistent relationships with the amounts of methane exchanged. Our results suggest that rewetting projects should be monitored not only with regard to vegetation development but also with respect to biogeochemical conditions. Further, high methane emissions that likely occur directly after rewetting by flooding should be considered when forecasting the overall effect of rewetting on GHG exchange.

Quantification of the methane concentration using anaerobic oxidation of methane coupled to extracellular electron transfer.

PubMed

Gao, Yaohuan; Ryu, Hodon; Rittmann, Bruce E; Hussain, Abid; Lee, Hyung-Sool

2017-10-01

A biofilm anode acclimated with growth media containing acetate, then acetate+methane, and finally methane alone produced electrical current in a microbial electrochemical cell (MxC) fed with methane as the sole electron donor. Geobacter was the dominant genus for the bacterial domain (93%) in the biofilm anode, while methanogens (Methanocorpusculum labreanum and Methanosaeta concilii) accounted for 82% of the total archaeal clones in the biofilm. Fluorescence in situ hybridization (FISH) imaging clearly showed a biofilm of mixed bacteria and archaea, suggesting a syntrophic interaction between them for performing anaerobic oxidation of methane (AOM) in the biofilm anode. Measured cumulative coulombs were linearly correlated to the methane-gas concentration in the range of 10-99.97% (R 2 ≥0.99) when the measurement was sustained for at least 50min Thus, cumulative coulombs over 50min could be used to quantify the methane concentration in gas samples. Copyright © 2017 Elsevier Ltd. All rights reserved.

Baseline groundwater quality from 20 domestic wells in Sullivan County, Pennsylvania, 2012

USGS Publications Warehouse

Sloto, Ronald A.

2013-01-01

Concentrations of dissolved methane ranged from less than 0.001 to 51.1 mg/L. Methane was not detected in water samples from 13 wells, and the methane concentration was less than 0.07 mg/L in samples from five wells. The highest dissolved methane concentrations were 4.1 and 51.1 mg/L, and the pH of the water from both wells was greater than 8. Water samples from these wells were analyzed for isotopes of carbon and hydrogen in the methane. The isotopic ratio values fell in the range for a thermogenic (natural gas) source. The water samples from these two wells had the highest concentrations of arsenic, boron, bromide, chloride, fluoride, lithium, molybdenum, and sodium of the 20 wells sampled.

Fugitive methane emissions from natural, urban, agricultural, and energy-production landscapes of eastern Australia

NASA Astrophysics Data System (ADS)

Kelly, Bryce F. J.; Iverach, Charlotte P.; Lowry, Dave; Fisher, Rebecca E.; France, James L.; Nisbet, Euan G.

2015-04-01

Modern cavity ringdown spectroscopy systems (CRDS) enable the continuous measurement of methane concentration. This allows for improved quantification of greenhouse gas emissions associated with various natural and human landscapes. We present a subset of over 4000 km of continuous methane surveying along the east coast of Australia, made using a Picarro G2301 CRDS, deployed in a utility vehicle with an air inlet above the roof at 2.2 mAGL. Measurements were made every 5 seconds to a precision of <0.5 ppb for CH4. These surveys were undertaken during dry daytime hours and all measurements were moisture corrected. We compare the concentration of methane in the near surface atmosphere adjacent to open-cut coal mines, unconventional gas developments (coal seam gas; CSG), and leaks detected in cities and country towns. In areas of dryland crops the median methane concentration was 1.78 ppm, while in the irrigation districts located on vertisol soils the concentration was as low as 1.76 ppm, which may indicate that these soils are a sink for methane. In the Hunter Valley, New South Wales, open-cut coal mining district we mapped a continuous 50 km interval where the concentration of methane exceeded 1.80 ppm. The median concentration in this interval was 2.02 ppm. Peak readings were beyond the range of the reliable measurement (in excess of 3.00 ppm). This extended plume is an amalgamation of plumes from 17 major pits 1 to 10 km in length. Adjacent to CSG developments in the Surat Basin, southeast Queensland, only small anomalies were detected near the well-heads. Throughout the vast majority of the gas fields the concentration of methane was below 1.80 ppm. The largest source of fugitive methane associated with CSG was off-gassing methane from the co-produced water holding ponds. At one location the down wind plume had a cross section of approximately 1 km where the concentration of methane was above 1.80 ppm. The median concentration within this section was 1.82 ppm, with a peak reading of 2.11 ppm. The ambient air methane concentration was always higher in urban environments compared to the surrounding countryside. Along one major road in Sydney we mapped an interval that extended for 6 km where the concentration was greater than 1.80 ppm. The median concentration in this interval was 1.90 ppm, with a peak reading of 1.97 ppm. This high reading in an urban setting is most likely due to leaks from the domestic gas distribution system. Methane leaks were detected in all country towns. Our measurements show that at the point of resource extraction the methane emission footprint of CSG is smaller than that of open-cut coal mining. However, leaking gas from urban centers must be added to the fugitive emissions of CSG to calculate the total fugitive emission footprint of CSG, which may therefore not be as low as claimed in the national greenhouse gas accounts. Our results highlight the need for additional continuous monitoring of methane emissions from all sectors, and for the full life-cycle of energy resources to be considered.

Rapid, Real-time Methane Detection in Ground Water Using a New Gas-Water Equilibrator Design

NASA Astrophysics Data System (ADS)

Ruybal, C. J.; DiGiulio, D. C.; Wilkin, R. T.; Hargrove, K. D.; McCray, J. E.

2014-12-01

Recent increases in unconventional gas development have been accompanied by public concern for methane contamination in drinking water wells near production areas. Although not a regulated pollutant, methane may be a marker contaminant for others that are less mobile in groundwater and thus may be detected later, or at a location closer to the source. In addition, methane poses an explosion hazard if exsolved concentrations reach 5 - 15% volume in air. Methods for determining dissolved gases, such as methane, have evolved over 60 years. However, the response time of these methods is insufficient to monitor trends in methane concentration in real-time. To enable rapid, real-time monitoring of aqueous methane concentrations during ground water purging, a new gas-water equilibrator (GWE) was designed that increases gas-water mass exchange rates of methane for measurement. Monitoring of concentration trends allows a comparison of temporal trends between sampling events and comparison of baseline conditions with potential post-impact conditions. These trends may be a result of removal of stored casing water, pre-purge ambient borehole flow, formation physical and chemical heterogeneity, or flow outside of well casing due to inadequate seals. Real-time information in the field can help focus an investigation, aid in determining when to collect a sample, save money by limiting costs (e.g. analytical, sample transport and storage), and provide an immediate assessment of local methane concentrations. Four domestic water wells, one municipal water well, and one agricultural water well were sampled for traditional laboratory analysis and compared to the field GWE results. Aqueous concentrations measured on the GWE ranged from non-detect to 1,470 μg/L methane. Some trends in aqueous methane concentrations measured on the GWE were observed during purging. Applying a paired t-test comparing the new GWE method and traditional laboratory analysis yielded a p-value 0.383, suggesting no significant difference between the two methods for the current study. Additional field and laboratory experimentation are necessary to justify use beyond screening. However, early GWE use suggests promising results and applications.

In search of thermogenic methane in groundwater in the Netherlands, with emphasis on the location of a historic gas well blowout

NASA Astrophysics Data System (ADS)

Schout, G.; Griffioen, J.; Hassanizadeh, S. M.; Hartog, N.

2017-12-01

Similar to the US, the Netherlands has a long history of oil & gas production, with around 2500 onshore hydrocarbon wells drilled since the late 1930s. While conventional reserves are diminishing, a governmental moratorium was put in place on shale gas exploration and production until 2023, in part due to concerns about its effects on groundwater quality. To investigate the industry's historic and potential future impact on groundwater quality in the country, a study was carried out to assess i) baseline methane concentrations and origin ii) the natural connectivity of deeper gas-bearing layers with the shallower groundwater systems. Through datamining, a dataset consisting of 12,200 groundwater analyses with methane concentrations was assembled. Furthermore, 25 additional samples were collected at targeted locations and analysed for dissolved gas molecular and isotopic composition. Methane concentrations are positively skewed with median, mean and maximum concentrations of 0.28, 2.17 and 120 mg/L, respectively. No correlation between methane concentrations and distance to hydrocarbon wells or faults is observed. In general, concentrations cannot be readily explained by factors such as the depth, geographic location, host formation and depositional environment. Thermogenic methane was first encountered at several hundred meters depth, below thick successions of marine Paleogene and Neogene clays that are present throughout the country and impede vertical flow. All methane encountered above these formations was found to be biogenic in origin, with one notable exception - a sample taken at the site of a catastrophic gas well blowout that occurred in 1965 near the village of Sleen. Combined, these findings suggest that thermogenic methane does not naturally occur in Dutch shallow groundwater and its presence can be used as an indicator of anthropogenic gas leakage. The unique Sleen blowout site was selected for a detailed investigation of the long-term effects of uncontrolled gas leakage on groundwater chemistry. Methane concentrations up to 45 mg/L were observed and the distribution pattern suggests on-going leakage, 50 years after the events. Results also show that anaerobic oxidation of methane plays a major role in controlling the spread of dissolved methane.

Significance of dissolved methane in effluents of anaerobically treated low strength wastewater and potential for recovery as an energy product: A review.

PubMed

Crone, Brian C; Garland, Jay L; Sorial, George A; Vane, Leland M

2016-11-01

The need for energy efficient Domestic Wastewater (DWW) treatment is increasing annually with population growth and expanding global energy demand. Anaerobic treatment of low strength DWW produces methane which can be used to as an energy product. Temperature sensitivity, low removal efficiencies (Chemical Oxygen Demand (COD), Suspended Solids (SS), and Nutrients), alkalinity demand, and potential greenhouse gas (GHG) emissions have limited its application to warmer climates. Although well designed anaerobic Membrane Bioreactors (AnMBRs) are able to effectively treat DWW at psychrophilic temperatures (10-30 °C), lower temperatures increase methane solubility leading to increased energy losses in the form of dissolved methane in the effluent. Estimates of dissolved methane losses are typically based on concentrations calculated using Henry's Law but advection limitations can lead to supersaturation of methane between 1.34 and 6.9 times equilibrium concentrations and 11-100% of generated methane being lost in the effluent. In well mixed systems such as AnMBRs which use biogas sparging to control membrane fouling, actual concentrations approach equilibrium values. Non-porous membranes have been used to recover up to 92.6% of dissolved methane and well suited for degassing effluents of Upflow Anaerobic Sludge Blanket (UASB) reactors which have considerable solids and organic contents and can cause pore wetting and clogging in microporous membrane modules. Microporous membranes can recover up to 98.9% of dissolved methane in AnMBR effluents which have low COD and SS concentrations. Sequential Down-flow Hanging Sponge (DHS) reactors have been used to recover between 57 and 88% of dissolved methane from Upflow Anaerobic Sludge Blanket (UASB) reactor effluent at concentrations of greater than 30% and oxidize the rest for a 99% removal of total dissolved methane. They can also remove 90% of suspended solids and COD in UASB effluents and produce a high quality effluent. In situ degassing can increase process stability, COD removal, biomass retention, and headspace methane concentrations. A model for estimating energy consumption associated with membrane-based dissolved methane recovery predicts that recovered dissolved and headspace methane may provide all the energy required for operation of an anaerobic system treating DWW at psychrophilic temperatures. Copyright © 2016 Elsevier Ltd. All rights reserved.

Online dissolved methane and total dissolved sulfide measurement in sewers.

PubMed

Liu, Yiwen; Sharma, Keshab R; Fluggen, Markus; O'Halloran, Kelly; Murthy, Sudhir; Yuan, Zhiguo

2015-01-01

Recent studies using short-term manual sampling of sewage followed by off-line laboratory gas chromatography (GC) measurement have shown that a substantial amount of dissolved methane is produced in sewer systems. However, only limited data has been acquired to date due to the low frequency and short span of this method, which cannot capture the dynamic variations of in-sewer dissolved methane concentrations. In this study, a newly developed online measuring device was used to monitor dissolved methane concentrations at the end of a rising main sewer network, over two periods of three weeks each, in summer and early winter, respectively. This device uses an online gas-phase methane sensor to measure methane under equilibrium conditions after being stripped from the sewage. The data are then converted to liquid-phase methane concentrations according to Henry's Law. The detection limit and range are suitable for sewer application and can be adjusted by varying the ratio of liquid-to-gas phase volume settings. The measurement presented good linearity (R² > 0.95) during field application, when compared to off-line measurements. The overall data set showed a wide variation in dissolved methane concentration of 5-15 mg/L in summer and 3.5-12 mg/L in winter, resulting in a significant average daily production of 24.6 and 19.0 kg-CH₄/d, respectively, from the network with a daily average sewage flow of 2840 m³/day. The dissolved methane concentration demonstrated a clear diurnal pattern coinciding with flow and sulfide fluctuation, implying a relationship with the wastewater hydraulic retention time (HRT). The total dissolved sulfide (TDS) concentration in sewers can be determined simultaneously with the same principle.

Carbon isotope equilibration during sulphate-limited anaerobic oxidation of methane

NASA Astrophysics Data System (ADS)

Yoshinaga, Marcos Y.; Holler, Thomas; Goldhammer, Tobias; Wegener, Gunter; Pohlman, John W.; Brunner, Benjamin; Kuypers, Marcel M. M.; Hinrichs, Kai-Uwe; Elvert, Marcus

2014-03-01

Collectively, marine sediments comprise the largest reservoir of methane on Earth. The flux of methane from the sea bed to the overlying water column is mitigated by the sulphate-dependent anaerobic oxidation of methane by marine microbes within a discrete sedimentary horizon termed the sulphate-methane transition zone. According to conventional isotope systematics, the biological consumption of methane leaves a residue of methane enriched in 13C (refs , , ). However, in many instances the methane within sulphate-methane transition zones is depleted in 13C, consistent with the production of methane, and interpreted as evidence for the intertwined anaerobic oxidation and production of methane. Here, we report results from experiments in which we incubated cultures of microbial methane consumers with methane and low levels of sulphate, and monitored the stable isotope composition of the methane and dissolved inorganic carbon pools over time. Residual methane became progressively enriched in 13C at sulphate concentrations above 0.5 mM, and progressively depleted in 13C below this threshold. We attribute the shift to 13C depletion during the anaerobic oxidation of methane at low sulphate concentrations to the microbially mediated carbon isotope equilibration between methane and carbon dioxide. We suggest that this isotopic effect could help to explain the 13C-depletion of methane in subseafloor sulphate-methane transition zones.

High Concentration of Methane and Magnificent gas Plumes Over gas Hydrate Field in the Eastern Margin of Japan Sea

NASA Astrophysics Data System (ADS)

Ishida, Y.; Matsumoto, R.; Hiruta, A.; Aoyama, C.; Tomaru, H.; Hiromatsu, M.

2005-12-01

Gas hydrates and prominent pockmarks have been observed on the Umitaka Spur in the eastern margin of Japan Sea, at the depth of about 900 m.Magnificent methane plumes, 550 to 600 m high, were detected by echo sounder for fish school, and massive gas hydrates were recovered by piston coring during the UT04 cruise of R/V Umitaka-maru (2004). The seawater over this area was collected by CTD and the samples of interstitial waters were extracted from sediment cores by hydraulic squeezer. The ratio of methane to ethane concentration (C1/C2) and the isotopic (δ 13C) composition of methane in the plume sites are less than 103 and from -40 to -50 (‰ PDB) respectively, suggesting that the origin of such gases are mostly thermogenic, whereas the gases in the sediments away from plumes are mostly microbial. The seawater samples demonstrated anomalously high concentration of methane over the plume sites. Maximum concentration is 160nmol/L above the methane plume site. The methane concentration values of most samples ranged from 4 to 6nmol/L. When it compared with the Nankai Trough (1 to 4nmol/L), even the base level methane is quite high. Seawater samples collected at the depth of 200 m exhibit sharp anomalies of 16 to 34nmol/L. With the intension to check the possibility of the inflow from the shelf and river waters, we collected surface waters far away from the Umitaka spur. Methane concentration was only 7nmol/L. Therefore, we conclude that anomalously high concentration at 200 m level over the spur is not likely to be explained by inflow of shelf waters, but also by methane seeps. The temperature of waters are extremely low from 0.25°C to 1.0°C below 300 m, then abruptly increases in shallow waters to about 25°C at surface water. Thus, bottom and intermediate waters are within the stability condition of methane hydrate. Under these conditions, gases from the sea floor would form gas hydrate within bottom water mass. Gas hydrate crystals would float up shallow to the water mass where they dissociate to supply methane at around 300 m due to abrupt temperature increase.

Effects of gas composition in headspace and bicarbonate concentrations in media on gas and methane production, degradability, and rumen fermentation using in vitro gas production techniques.

PubMed

Patra, Amlan Kumar; Yu, Zhongtang

2013-07-01

Headspace gas composition and bicarbonate concentrations in media can affect methane production and other characteristics of rumen fermentation in in vitro gas production systems, but these 2 important factors have not been evaluated systematically. In this study, these 2 factors were investigated with respect to gas and methane production, in vitro digestibility of feed substrate, and volatile fatty acid (VFA) profile using in vitro gas production techniques. Three headspace gas compositions (N2+ CO2+ H2 in the ratio of 90:5:5, CO2, and N2) with 2 substrate types (alfalfa hay only, and alfalfa hay and a concentrate mixture in a 50:50 ratio) in a 3×2 factorial design (experiment 1) and 3 headspace compositions (N2, N2 + CO2 in a 50:50 ratio, and CO2) with 3 bicarbonate concentrations (80, 100, and 120 mM) in a 3×3 factorial design (experiment 2) were evaluated. In experiment 1, total gas production (TGP) and net gas production (NGP) was the lowest for CO2, followed by N2, and then the gas mixture. Methane concentration in headspace gas after fermentation was greater for CO2 than for N2 and the gas mixture, whereas total methane production (TMP) and net methane production (NMP) were the greatest for CO2, followed by the gas mixture, and then N2. Headspace composition did not affect in vitro digestibility or the VFA profile, except molar percentages of propionate, which were greater for CO2 and N2 than for the gas mixture. Methane concentration in headspace gas, TGP, and NGP were affected by the interaction of headspace gas composition and substrate type. In experiment 2, increasing concentrations of CO2 in the headspace decreased TGP and NGP quadratically, but increased the concentrations of methane, NMP, and in vitro fiber digestibility linearly, and TMP quadratically. Fiber digestibility, TGP, and NGP increased linearly with increasing bicarbonate concentrations in the medium. Concentrations of methane and NMP were unaffected by bicarbonate concentration, but TMP tended to increase due to increasing bicarbonate concentration. Although total VFA concentration and molar percentage of butyrate were unchanged, the molar percentage of acetate, and acetate-to-propionate ratio decreased, whereas the molar percentage of propionate increased quadratically with increasing bicarbonate concentration. This study demonstrated for the first time that headspace composition, especially CO2 content, and bicarbonate concentration in media could significantly influence gas and methane production, and rumen fermentation in gas production techniques. Copyright © 2013 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Effects of household detergent on anaerobic fermentation of kitchen wastewater from food waste disposer.

PubMed

Lee, K H; Park, K Y; Khanal, S K; Lee, J W

2013-01-15

This study examines the effects of household detergent on anaerobic methane fermentation of wastewater from food waste disposers (FWDs). Anaerobic toxicity assay (ATA) demonstrated that methane production substantially decreased at a higher detergent concentration. The Gompertz three-parameter model fitted well with the ATA results, and both the extent of methane production (M) and methane production rate (R(m)) obtained from the model were strongly affected by the concentration of the detergent. The 50% inhibitory concentration (IC(50)) of the detergent was 603 mg/L based on R(m). Results from fatty acid methyl esters (FAMEs) analysis of microbial culture revealed that deterioration of methane fermentation was attributed to impaired structure of anaerobic microbial membrane due to detergent. This study suggests that wastewater from FWD could be used for methane production, but it is necessary to reduce the concentration of detergent prior to anaerobic fermentation. Copyright © 2012 Elsevier B.V. All rights reserved.

Root-Associated Methane Oxidation and Methanogenesis: Key Determinants of Wetland Methane Emissions

NASA Technical Reports Server (NTRS)

King, G. M.

1997-01-01

During the award period, we have assessed the extent and controls of methane oxidation in north temperate wetlands. It is evident that wetlands have been a major global source of atmospheric methane in the past, and are so at present. It is also evident that microbial methane oxidation consumes a variable fraction of total wetland methane production, perhaps 10%-90%. Methane oxidation is thus a potentially important control of wetland methane emission. Our efforts have been designed to determine the extent of the process, its controls, and possible relationships to changes that might be expected in wetlands as a consequence of anthropogenic or climate-related disturbances. Current work, has emphasized controls of methane oxidation associated with rooted aquatic plants. As for the sediment-water interface, we have observed that oxygen availability is a primary limiting factor. Our conclusion is based on several different lines of evidence obtained from in vitro and in situ analyses. First, we have measured the kinetics of methane oxidation by intact plant roots harboring methane-oxidizing bacteria, as well as the kinetics of the methanotrophs themselves. Values for the half-saturation constant (apparent K(sub m)) are approximately 5 microns. These values are roughly equivalent to, or much less than porewater methane concentrations, indicating that uptake is likely saturated with respect to methane, and that some other parameter must limit activity. Methane concentrations in the lacunar spaces at the base of plant stems are also comparable to the half-saturation constants (when expressed as equivalent dissolved concentrations), providing further support for limitation of uptake by parameters other than methane.

Effects of encapsulated nitrate on growth performance, carcass characteristics, nitrate residues in tissues, and enteric methane emissions in beef steers: Finishing phase.

PubMed

Lee, C; Araujo, R C; Koenig, K M; Beauchemin, K A

2017-08-01

A finishing feedlot study was conducted with beef steers to determine effects of encapsulated nitrate (EN) on growth performance, carcass characteristics, methane production, and nitrate (NO) residues in tissues. The 132 crossbred steers were backgrounded in a feedlot for 91 d and transitioned for 28 days to the high-concentrate diets evaluated in the present study, maintaining the treatment and pen assignments designated at the start of the backgrounding period. The steers were initially assigned to 22 pens (6 animals per pen) in a randomized complete block design with BW (18 pens) and animals designated for methane measurement (4 pens) as blocking factors. Five animals in each pen designated for methane measurement (total of 20 animals) were monitored for methane emissions in respiratory chambers twice during the experiment. Pens received 3 dietary treatments (7 pens each): Control, a finishing diet supplemented with urea; 1.25% EN, control diet supplemented with 1.25% encapsulated NO in dietary DM that partially replaced urea; and 2.5% EN, control diet supplemented with 2.5% EN (DM basis) fully replacing urea. The final pen designated only for methane measurement received a fourth dietary treatment, 2.3% UEN, the control diet supplemented with unencapsulated NO (UEN) fully replacing urea. The cattle weighed 449 ± SD 32 kg at the start of the 150-d finishing period. The 2.5% EN diet decreased ( < 0.01) DMI compared with Control and 1.25% EN diets. Feeding EN tended to increase ( = 0.092) ADG compared with Control, and G:F was improved ( < 0.01) for EN compared with Control. No differences in methane production (g/d) and yield (g/kg DMI) were observed among treatments. Inclusion of EN in the diets increased ( ≤ 0.03) sorting in favor of large and medium particles and against small and fine particles. Plasma NO and NO concentrations were elevated ( < 0.01) with EN in a dose-response manner, but total blood methemoglobin levels for all treatments were low, below the detection limit. Feeding EN increased ( < 0.01) NO concentrations of samples from muscle, fat, liver, and kidney; NO concentrations of these tissues were similar between 1.25% EN and 2.3% UEN. In conclusion, inclusion of 2.5% EN in a finishing diet (DM basis; about 2% NO) did not cause NO toxicity or any health problems in the long term. In comparison with supplemental urea, feeding EN improved feed efficiency despite increases in sorting against dietary EN.

Methane distribution and oxidation around the Lena Delta in summer 2013

NASA Astrophysics Data System (ADS)

Bussmann, Ingeborg; Hackbusch, Steffen; Schaal, Patrick; Wichels, Antje

2017-11-01

The Lena River is one of the largest Russian rivers draining into the Laptev Sea. The predicted increases in global temperatures are expected to cause the permafrost areas surrounding the Lena Delta to melt at increasing rates. This melting will result in high amounts of methane reaching the waters of the Lena and the adjacent Laptev Sea. The only biological sink that can lower methane concentrations within this system is methane oxidation by methanotrophic bacteria. However, the polar estuary of the Lena River, due to its strong fluctuations in salinity and temperature, is a challenging environment for bacteria. We determined the activity and abundance of aerobic methanotrophic bacteria by a tracer method and by the quantitative polymerase chain reaction. We described the methanotrophic population with a molecular fingerprinting method (monooxygenase intergenic spacer analysis), as well as the methane distribution (via a headspace method) and other abiotic parameters, in the Lena Delta in September 2013. The median methane concentrations were 22 nmol L-1 for riverine water (salinity (S) < 5), 19 nmol L-1 for mixed water (5 < S < 20) and 28 nmol L-1 for polar water (S > 20). The Lena River was not the source of methane in surface water, and the methane concentrations of the bottom water were mainly influenced by the methane concentration in surface sediments. However, the bacterial populations of the riverine and polar waters showed similar methane oxidation rates (0.419 and 0.400 nmol L-1 d-1), despite a higher relative abundance of methanotrophs and a higher estimated diversity in the riverine water than in the polar water. The methane turnover times ranged from 167 days in mixed water and 91 days in riverine water to only 36 days in polar water. The environmental parameters influencing the methane oxidation rate and the methanotrophic population also differed between the water masses. We postulate the presence of a riverine methanotrophic population that is limited by sub-optimal temperatures and substrate concentrations and a polar methanotrophic population that is well adapted to the cold and methane-poor polar environment but limited by a lack of nitrogen. The diffusive methane flux into the atmosphere ranged from 4 to 163 µmol m2 d-1 (median 24). The diffusive methane flux accounted for a loss of 8 % of the total methane inventory of the investigated area, whereas the methanotrophic bacteria consumed only 1 % of this methane inventory. Our results underscore the importance of measuring the methane oxidation activities in polar estuaries, and they indicate a population-level differentiation between riverine and polar water methanotrophs.

Improved methane removal in exhaust gas from biogas upgrading process using immobilized methane-oxidizing bacteria.

PubMed

Sun, Meng-Ting; Yang, Zhi-Man; Fu, Shan-Fei; Fan, Xiao-Lei; Guo, Rong-Bo

2018-05-01

Methane in exhaust gas from biogas upgrading process, which is a greenhouse gas, could cause global warming. The biofilter with immobilized methane-oxidizing bacteria (MOB) is a promising approach for methane removal, and the selections of inoculated MOB culture and support material are vital for the biofilter. In this work, five MOB consortia were enriched at different methane concentrations. The MOB-20 consortium enriched at the methane concentration of 20.0% (v/v) was then immobilized on sponge and two particle sizes of volcanic rock in biofilters to remove methane in exhaust gas from biogas upgrading process. Results showed that the immobilized MOB performed more admirable methane removal capacity than suspended cells. The immobilized MOB on sponge reached the highest methane removal efficiency (RE) of 35%. The rough surface, preferable hydroscopicity, appropriate pore size and particle size of support material might favor the MOB immobilization and accordingly methane removal. Copyright © 2018 Elsevier Ltd. All rights reserved.

Dissolved methane in the Beaufort Sea and the Arctic Ocean, 1992-2009; sources and atmospheric flux

USGS Publications Warehouse

Lorenson, Thomas D.; Greinert, Jens; Coffin, Richard B.

2016-01-01

Methane concentration and isotopic composition was measured in ice-covered and ice-free waters of the Arctic Ocean during eleven surveys spanning the years of 1992-1995 and 2009. During ice-free periods, methane flux from the Beaufort shelf varies from 0.14 to 0.43 mg CH4 m-2 day-1. Maximum fluxes from localized areas of high methane concentration are up to 1.52 mg CH4 m-2 day-1. Seasonal buildup of methane under ice can produce short-term fluxes of methane from the Beaufort shelf that varies from 0.28 to 1.01 to mg CH4 m-2 day-1. Scaled-up estimates of minimum methane flux from the Beaufort Sea and pan-Arctic shelf for both ice-free and ice-covered periods range from 0.02 Tg CH4 yr-1 and 0.30 Tg CH4 yr-1 respectively to maximum fluxes of 0.18 Tg CH4 yr-1 and 2.2 Tg CH4 yr-1 respectively. A methane flux of 0.36 Tg CH4 yr-1from the deep Arctic Ocean was estimated using data from 1993-94. The flux can be as much as 2.35 Tg CH4 yr-1 estimated from maximum methane concentrations and wind speeds of 12 m/s, representing only 0.42% of the annual atmospheric methane budget of ~560 Tg CH4 yr-1. There were no significant changes in methane fluxes during the time period of this study. Microbial methane sources predominate with minor influxes from thermogenic methane offshore Prudhoe Bay and the Mackenzie River delta and may include methane from gas hydrate. Methane oxidation is locally important on the shelf and is a methane sink in the deep Arctic Ocean.

Carbon and hydrogen isotope composition and C-14 concentration in methane from sources and from the atmosphere: Implications for a global methane budget

NASA Technical Reports Server (NTRS)

Wahlen, Martin

1994-01-01

The topics covered include the following: biogenic methane studies; forest soil methane uptake; rice field methane sources; atmospheric measurements; stratospheric samples; Antarctica; California; and Germany.

Methane anomalies in the oxygenated upper waters of the central Baltic Sea associated with zooplankton abundance

NASA Astrophysics Data System (ADS)

Schmale, Oliver; Wäge, Janine; Morholz, Volker; Rehder, Gregor; Wasmund, Norbert; Gräwe, Ulf; Labrenz, Matthias; Loick-Wilde, Natalie

2017-04-01

Apart from the sediment as the dominant source of methane in the aquatic realm the process of methane production in well-oxygenated waters has received considerable attention during the last years. The paradox of methane accumulation in these relatively shallow waters, commonly termed as "oceanic methane paradox", has been sporadically observed in lakes as well as in marine ecosystems like the Gulf of Mexico, the Black Sea, the Baltic Sea, Arctic waters or above the continental shelf off the coast of Spain and Africa. Even if this phenomenon has been described in the literature over the last decades, the potential sources of shallow methane accumulation are still controversially discussed. We report on methane enrichments that were observed during summer in the upper water column of the Gotland Basin, central Baltic Sea. In the eastern part of the basin methane concentrations just below the thermocline (in about 30 m water depth) varied between 15 and 77 nM, in contrast to the western part of the basin where no methane enrichments could be detected. Stable carbon isotope ratios of methane (delta 13C-CH4 of -67.6‰) clearly indicated its in situ biogenic origin. This is supported by clonal sequences from the depth with high methane concentrations in the eastern Gotland Basin, which cluster with the clade Methanomicrobiacea, a family of methanogenic Archaea. Hydroacoustic observation in combination with plankton net tows displayed a seston enrichment (size >100 micro meter) in a layer between 30-50 m depth. The dominant species in the phytoplankton, Dinophysis norvegica, was concentrated at 10-20 m depth, and showed higher concentrations in the eastern Gotland Basin in comparison with the western part of the basin. In contrast to the western Gotland Basin, the zooplankton community in the eastern part was dominated by the copepod species Temora longicornis. Laboratory incubations of a T. longicornis dominated seston fraction (>100 micro meter) sampled in the depth of the subthermocline methane anomaly showed a clear correlation between seston concentration (i.e. abundance of copepods) and methane production rates.

Gas-geochemical condition and ecological functions of urban soils in areas with gas generating grounds

NASA Astrophysics Data System (ADS)

Mozharova, Nadezhda; Lebed-Sharlevich, Iana; Kulachkova, Svetlana

2014-05-01

Rapid urbanization and expansion of city borders lead to development of new areas, often following with relief changes, covering of gully-ravine systems and river beds with technogenic grounds containing construction and municipal waste. Decomposition of organic matter in these grounds is a source of methane and carbon dioxide. Intensive generation and accumulation of CO2 and CH4 into grounds may cause a fire and explosion risk for constructed objects. Gases emission to the atmosphere changes the global balance of GHGs and negatively influences on human health. The aim of this investigation is to study gas-geochemical condition and ecological functions of urban soils in areas with gas generating grounds. Studied areas are the gully-ravine systems or river beds, covered with technogenic grounds during land development. Stratigraphic columns of these grounds are 5-17 meters of man-made loamy material with inclusion of construction waste. Gas generating layer with increased content of organic matter, reductive conditions and high methanogenic activity (up to 1.0 ng*g-1*h-1) is situated at the certain depth. Maximum CH4 and CO2 concentrations in this layer reach dangerous values (2-10% and 11%, respectively) in the current standards. In case of disturbance of ground layer (e.g. well-drilling) methane is rapidly transferred by convective flux to atmosphere. The rate of CH4 emission reaches 100 mg*m-2*h-1 resulting in its atmospheric concentration growth by an order of magnitude compared with background. In normal occurrence of grounds methane gradually diffuses into the upper layers by pore space, consuming on different processes (e.g. formation of organic matter, nitrogen compounds or specific particles of magnetite), and emits to atmosphere. CH4 emission rate varies from 1 to 40 mg*m-2*h-1 increasing with depth of grounds. Carbon dioxide emission is about 100 mg*m-2*h-1. During soil formation on gas generating grounds bacterial oxidation of methane, one of the most important ecological functions of such soils, is initiated. Due to high rate of this process (25-30 ng*g-1*h-1) accumulation of methane in the profile does not observed, its content in soil averages 2-5 ppm. Methane emission from soils is low (0.01-0.03 mg*m-2*h-1) or there is a weak consumption of atmospheric CH4, whereby its concentration in the air corresponds to the average content of this gas. Active methane oxidation and decomposition of organic matter under aerobic conditions result to intensive formation of carbon dioxide and, thus, increase its emission (600 mg*m-2*h-1), concentration in soils (0.2-0.9%) and in atmosphere (up to 0.5%). Fixed concentration of CO2 in the air is dangerous for human health. Thus, presence of gas generating grounds with high content of organic matter leads to methane formation, causing its intensive emission to atmosphere. At upper layers of soils and grounds bacterial oxidation of methane occurs and results in complete CH4 utilization. During this process significant amounts of carbon dioxide are released and accumulated in the atmosphere up to concentration dangerous for people. Carbon dioxide emission increases current level of this gas in the urban atmosphere.

Sustained in situ measurements of dissolved oxygen, methane and water transport processes in the benthic boundary layer at MC118, northern Gulf of Mexico

NASA Astrophysics Data System (ADS)

Martens, Christopher S.; Mendlovitz, Howard P.; Seim, Harvey; Lapham, Laura; D'Emidio, Marco

2016-07-01

Within months of the BP Macondo Wellhead blowout, elevated methane concentrations within the water column revealed a significant retention of light hydrocarbons in deep waters plus corresponding dissolved oxygen (DO) deficits. However, chemical plume tracking efforts were hindered by a lack of in situ monitoring capabilities. Here, we describe results from in situ time-series, lander-based investigations of physical and biogeochemical processes controlling dissolved oxygen, and methane at Mississippi Canyon lease block 118 ( 18 km from the oil spill) conducted shortly after the blowout through April 2012. Multiple sensor arrays plus open-cylinder flux chambers (;chimneys;) deployed from a benthic lander collected oxygen, methane, pressure, and current speed and direction data within one meter of the seafloor. The ROVARD lander system was deployed for an initial 21-day test experiment (9/13/2010-10/04/2010) at 882 m depth before a longer 160-day deployment (10/24/2011-4/01/2012) at 884 m depth. Temporal variability in current directions and velocities and water temperatures revealed strong influences of bathymetrically steered currents and overlying along-shelf flows on local and regional water transport processes. DO concentrations and temperature were inversely correlated as a result of water mass mixing processes. Flux chamber measurements during the 160-day deployment revealed total oxygen utilization (TOU) averaging 11.6 mmol/m2 day. Chimney DO concentrations measured during the 21-day deployment exhibited quasi-daily variations apparently resulting from an interaction between near inertial waves and the steep topography of an elevated scarp immediately adjacent to the 21-day deployment site that modulated currents at the top of the chimney. Variability in dissolved methane concentrations suggested significant temporal variability in gas release from nearby hydrocarbon seeps and/or delivery by local water transport processes. Free-vehicle (lander) monitoring over time scales of months to years utilizing in situ sensors can provide an understanding of processes controlling water transport, respiration and the fate and impacts of accidental and natural gas and oil releases.

Mitigating ammonia inhibition of thermophilic anaerobic treatment of digested piggery wastewater: use of pH reduction, zeolite, biomass and humic acid.

PubMed

Ho, L; Ho, G

2012-09-15

High free ammonia released during anaerobic digestion of livestock wastes is widely known to inhibit methanogenic microorganisms and result in low methane production. This was encountered during our earlier thermophilic semi-continuously fed continuously-stirred tank reactor (CSTR) treatment of piggery wastewater. This study explored chemical and biological means to mitigate ammonia inhibition on thermophilic anaerobic treatment of piggery wastewater with the aim to increase organic volatile carbon reduction and methane production. A series of thermophilic anaerobic batch experiments were conducted on the digested piggery effluent to investigate the effects of pH reduction (pH 8.3 to 7.5, 7.0 and 6.5) and additions of biomass (10% v/v and 19% v/v anaerobic digested piggery biomass and aerobic-anaerobic digested municipal biomass), natural zeolite (10, 15 and 20 g/L) and humic acid (1, 5 and 10 g/L) on methane production at 55 °C for 9-11 days. Reduction of the wastewater pH from its initial pH of 8.3 to 6.5 produced the greatest stimulation of methane production (3.4 fold) coupled with reductions in free ammonia (38 fold) and total volatile fatty acids (58% TVFA), particularly acetate and propionate. Addition of 10-20 g/L zeolite to piggery wastewater with and without pH reduction to 6.5 further enhanced total VFA reduction and methane production over their respective controls, with 20 g/L zeolite producing the highest enhancement effect despite the ammonia-nitrogen concentrations of the treated wastewaters remaining high. Without pH reduction, zeolite concentration up to 20 g/L was required to achieve comparable methane enhancement as the pH-reduced wastewater at pH 6.5. Although biomass (10% v/v piggery and municipal wastes) and low humic acid (1 and 5 g/L) additions enhanced total VFA reduction and methane production, they elevated the residual effluent total COD concentrations over the control wastewaters (pH-unadjusted and pH-reduced) unlike zeolite treatment. The outcomes from these batch experiments support the use of pH reduction to 6.5 and zeolite treatment (10-20 g/L) as effective strategies to mitigate ammonia inhibition of the thermophilic anaerobic treatment of piggery wastewater. Copyright © 2012 Elsevier Ltd. All rights reserved.

Anaerobic Transformation of Chlorinated Aliphatic Hydrocarbons in a Sand Aquifer Based on Spatial Chemical Distributions

NASA Astrophysics Data System (ADS)

Semprini, Lewis; Kitanidis, Peter K.; Kampbell, Don H.; Wilson, John T.

1995-04-01

We estimated the distribution of chlorinated aliphatic hydrocarbons (CAHs) from groundwater samples collected along three transects in a sand aquifer. Trichloroethylene (TCE) leaked and contaminated the aquifer probably more than a decade before we collected the measurements. The data show significant concentrations of TCE, cis-l,2-dichloroethylene (c-DCE), vinyl chloride (VC), and ethene. We attributed DCE, VC, and ethene to the reductive dehalogenation of TCE. The CAH concentrations varied significantly with depth and correlate with sulfate and methane concentrations. Anoxic aquifer conditions exist with methane present at relatively high concentrations at depth. High concentrations of TCE correspond with the absence of methane or low methane concentrations, whereas products of TCE dehalogenation are associated with higher methane concentrations and low sulfate concentrations. Indications are that the dechlorination of TCE and DCE to VC and ethene is associated with sulfate reduction and active methanogenesis. TCE dechlorination to DCE is likely occurring under the less reducing conditions of sulfate reduction, with further reductions to VC and ethene occurring under methanogenic conditions. We estimated that about 20% of TCE has dechlorinated to ethene. The analysis of the data enhanced our knowledge of natural in situ transformation and transport processes of CAHs.

40 CFR 60.565 - Reporting and recordkeeping requirements.

Code of Federal Regulations, 2014 CFR

2014-07-01

... emission control efficiency of a combustion device or the outlet concentration of TOC (minus methane and... performance test period, and (ii) The percent reduction of TOC (minus methane and ethane) achieved by the incinerator, the concentration of TOC (minus methane and ethane) (ppmv, by compound) at the outlet of the...

40 CFR 60.565 - Reporting and recordkeeping requirements.

Code of Federal Regulations, 2010 CFR

2010-07-01

... emission control efficiency of a combustion device or the outlet concentration of TOC (minus methane and... performance test period, and (ii) The percent reduction of TOC (minus methane and ethane) achieved by the incinerator, the concentration of TOC (minus methane and ethane) (ppmv, by compound) at the outlet of the...

40 CFR 60.565 - Reporting and recordkeeping requirements.

Code of Federal Regulations, 2012 CFR

2012-07-01

... emission control efficiency of a combustion device or the outlet concentration of TOC (minus methane and... performance test period, and (ii) The percent reduction of TOC (minus methane and ethane) achieved by the incinerator, the concentration of TOC (minus methane and ethane) (ppmv, by compound) at the outlet of the...

40 CFR 60.565 - Reporting and recordkeeping requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... emission control efficiency of a combustion device or the outlet concentration of TOC (minus methane and... performance test period, and (ii) The percent reduction of TOC (minus methane and ethane) achieved by the incinerator, the concentration of TOC (minus methane and ethane) (ppmv, by compound) at the outlet of the...

40 CFR 60.565 - Reporting and recordkeeping requirements.

Code of Federal Regulations, 2013 CFR

2013-07-01

... emission control efficiency of a combustion device or the outlet concentration of TOC (minus methane and... performance test period, and (ii) The percent reduction of TOC (minus methane and ethane) achieved by the incinerator, the concentration of TOC (minus methane and ethane) (ppmv, by compound) at the outlet of the...

30 CFR 75.388 - Boreholes in advance of mining.

Code of Federal Regulations, 2013 CFR

2013-07-01

... more than 1.0 percent methane, less than 19.5 percent oxygen, or harmful concentrations of carbon monoxide, carbon dioxide or other explosive, harmful or noxious gases; (2) Tests for methane, oxygen... and the mine workings; (3) The concentrations of methane, oxygen, carbon monoxide, and carbon dioxide...

30 CFR 75.388 - Boreholes in advance of mining.

Code of Federal Regulations, 2010 CFR

2010-07-01

... more than 1.0 percent methane, less than 19.5 percent oxygen, or harmful concentrations of carbon monoxide, carbon dioxide or other explosive, harmful or noxious gases; (2) Tests for methane, oxygen... and the mine workings; (3) The concentrations of methane, oxygen, carbon monoxide, and carbon dioxide...

30 CFR 75.388 - Boreholes in advance of mining.

Code of Federal Regulations, 2012 CFR

2012-07-01

... more than 1.0 percent methane, less than 19.5 percent oxygen, or harmful concentrations of carbon monoxide, carbon dioxide or other explosive, harmful or noxious gases; (2) Tests for methane, oxygen... and the mine workings; (3) The concentrations of methane, oxygen, carbon monoxide, and carbon dioxide...

30 CFR 75.388 - Boreholes in advance of mining.

Code of Federal Regulations, 2014 CFR

2014-07-01

... more than 1.0 percent methane, less than 19.5 percent oxygen, or harmful concentrations of carbon monoxide, carbon dioxide or other explosive, harmful or noxious gases; (2) Tests for methane, oxygen... and the mine workings; (3) The concentrations of methane, oxygen, carbon monoxide, and carbon dioxide...

30 CFR 75.388 - Boreholes in advance of mining.

Code of Federal Regulations, 2011 CFR

2011-07-01

... more than 1.0 percent methane, less than 19.5 percent oxygen, or harmful concentrations of carbon monoxide, carbon dioxide or other explosive, harmful or noxious gases; (2) Tests for methane, oxygen... and the mine workings; (3) The concentrations of methane, oxygen, carbon monoxide, and carbon dioxide...

Investigation of flame structure and burning intensity of partially premixed methane enrichment of syngas using OH-PLIF and kinetic simulation

NASA Astrophysics Data System (ADS)

Pu, Ge; Huang, Beibei; Zhang, Xun; Du, Jiantai; Zhu, Tuanhui; Chen, Bei

2018-05-01

Various experiments were conducted to study the combustion characteristics of partially premixed methane enrichment of syngas by using the OH-PLIF technique. Experiments were conducted on a co-flow burner, and the methane concentration (XCH4 = CH4/(H2+CO+CH4)) was varied from 0 to 20%, the overall equivalence ratio was varied from 0.4 to 1.2 and the inner equivalence ratio was varied from 1.5 to 3.5. Kinetic simulation was conducted by using OPPDIF module of CHEMKIN-Pro software. Results show that an increase in XCH4 and ϕoverall weakens the OH signal intensity. Adding methane into the fuel greatly increases the height of the inner flame front, and the increase of methane concentration has a negative effect on flame propagation speed. Meanwhile, simulation results remain consistent with the experiments. The main OH radical production reaction changes from R46: H+HO2 = 2OH to R38: H+O2 = O+OH when methane concentration contained in the fuel mixture increases. Sensitivity analysis also indicates that reaction which plays a dominant effect on temperature changes with the increase of methane concentration.

Ground truthing for methane hotspots at Railroad Valley, NV - application to Mars

NASA Astrophysics Data System (ADS)

Detweiler, A. M.; Kelley, C. A.; Bebout, B.; McKay, C. P.; DeMarines, J.; Yates, E. L.; Iraci, L. T.

2011-12-01

During the 2010 Greenhouse gas Observing SATellite (GOSAT) calibration and validation campaign at Railroad Valley (RRV) playa, NV, unexpected methane and carbon dioxide fluctuations were observed at the dry lakebed. Possible sources included the presence of natural gas (thermogenic methane) from oil deposits in the surrounding playa, and/or methane production from microbial activity (biogenic) in the subsurface of the playa. In the summer of 2011, measurements were undertaken to identify potential methane sources at RRV. The biogenicity of the methane was determined based on δ13C values and methane/ethane ratios. Soil gas samples and sediments were collected at different sites in the playa and surrounding areas. The soils of the playa consist of a surface crust layer (upper ~ 10 cm) grading to a dense clay below about 25 cm. Soil gas from the playa, sampled at about 20 and 80 cm depths, reflected atmospheric methane concentrations, ranging from 2 to 2.4 ppm, suggesting that no methane was produced within the playa. Natural springs on the northeast and western border of the playa, detected as methane hotspots from a flyover by the Sensor Integrated Environmental Remote Research Aircraft (SIERRA), were also sampled. Bubbles in these springs had methane concentrations that ranged from 69 to 84% by volume. In addition, ethane was detected at very low concentrations, giving methane/ethane ratios in excess of 100,000, indicating biogenic methane in the springs. Soils and sediments collected at the playa and spring sites were incubated in vials over a period of ~23 days. Methane production was observed in the spring sites (avg. 228.6 ± 49.1 nmol/g/d at Kate Springs), but was not evident for the playa sites. The incubation data, therefore, corroborated in situ methane concentration measurements. Particulate organic carbon (POC) was low for all sites samples (0.05-0.38%), with the exception of Kate Springs, which had a much higher POC concentration of 3.4 ± 0.7%. Temperature and relative humidity sensors were placed in the playa at 5, 20, and 30 cm below the surface. Since the relative humidity neared 100% (down to 20 cm below the surface), high enough to support microbial life, the observed absence of methane production in the playa itself is likely due to the low POC content, compared to other methane-producing environments. The spatial distribution of methane in combination with the spectral reflectance at the RRV dry lakebed makes it a good Mars analog. The ground truthing and satellite calibration work accomplished at RRV is a good exercise in preparation to identifying the origins of methane observed in the atmosphere of Mars during the upcoming 2012 Mars Science Laboratory and 2016 ExoMars Trace Gas Orbiter missions.

Methane emission through ebullition from an estuarine mudflat: 2. Field observations and modeling of occurrence probability

NASA Astrophysics Data System (ADS)

Chen, Xi; Schäfer, Karina V. R.; Slater, Lee

2017-08-01

Ebullition can transport methane (CH4) at a much faster rate than other pathways, albeit over limited time and area, in wetland soils and sediments. However, field observations present large uncertainties in ebullition occurrences and statistic models are needed to describe the function relationship between probability of ebullition occurrence and water level changes. A flow-through chamber was designed and installed in a mudflat of an estuarine temperate marsh. Episodic increases in CH4 concentration signaling ebullition events were observed during ebbing tides (15 events over 456 ebbing tides) and occasionally during flooding tides (4 events over 455 flooding tides). Ebullition occurrence functions were defined using logistic regression as the relative initial and end water levels, as well as tidal amplitudes were found to be the key functional variables related to ebullition events. Ebullition of methane was restricted by a surface frozen layer during winter; melting of this layer during spring thaw caused increases in CH4 concentration, with ebullition fluxes similar to those associated with large fluctuations in water level around spring tides. Our findings suggest that initial and end relative water levels, in addition to tidal amplitude, partly regulate ebullition events in tidal wetlands, modulated by the lunar cycle, storage of gas bubbles at different depths and seasonal changes in the surface frozen layer. Maximum tidal strength over a few days, rather than hourly water level, may be more closely associated with the possibility of ebullition occurrence as it represents a trade-off time scale in between hourly and lunar periods.

Methane concentration and isotopic composition (δ13C-CH4) in the Nerja Cave system (South Spain)

NASA Astrophysics Data System (ADS)

Vadillo, Iñaki; Etiope, Giuseppe; Benavente, José; Ojeda, Lucia; Liñán, Cristina; Carrasco, Francisco

2016-04-01

Air in underground caves often has methane (CH4) concentrations below the atmospheric level, due to methanotrophic or other unkown CH4 consuming processes. Caves are thus considered a potential sink for atmospheric methane. If globally important, this underground CH4 oxidation should be taken into account in the atmospheric methane budget, in addition to the known soil methanotrophy and tropospheric/stratospheric sinks. A large set of data is however necessary to understand how and how much methane from external atmospheric air is consumed in the caves. While methane concentration data are available for several caves worldwide, its isotopic composition and variations in space and time are poorly documented. We measured methane concentration and stable C isotope composition (δ13C) in the Nerja cave (Southern Spain) air during two surveys in March and April 2015. CH4 concentration decreases progressively from the more external cave rooms, with atmospheric levels of 1.9 ppmv, to the more internal and isolated rooms down to 0.5 ppmv. δ13C increases correspondingly from -47 ‰ to -41 ‰ (VPDB). CH4 is systematically 13C-enriched (δ13C > -45) in areas of the cave where the concentration is below 1.4 ppmv. This combination of concentration decrease and 13C-enrichment towards the more internal and isolated zones of the cave confirms the importance of CH4 oxidation, likely driven by methanotrophic bacteria. Further data, including stable H isotope composition of sub-atmospheric CH4 concentrations, CO2 and microbial analyses, shall be acquired over time to assess the actual role of methanotrophic bacteria and seasonal controls in the CH4 consumption process.

Constraining the relationships between anaerobic oxidation of methane and sulfate reduction under in situ methane concentrations

NASA Astrophysics Data System (ADS)

Zhuang, G.; Wegener, G.; Joye, S. B.

2017-12-01

The anaerobic oxidation of methane (AOM) is an important microbial metabolism in the global carbon cycle. In marine methane seeps sediment, this process is mediated by syntrophic consortium that includes anaerobic methanotrophic archaea (ANME) and sulfate-reducing bacteria (SRB). Stoichiometrically in AOM methane oxidation should be coupled to sulfate reduction (SR) in a 1:1 ratio. However, weak coupling of AOM and SR in seep sediments was frequently observed from the ex situ rate measurements, and the metabolic dynamics of AOM and SR under in situ conditions remain poorly understood. Here we investigated the metabolic activity of AOM and SR with radiotracers by restoring in situ methane concentrations under pressure to constrain the in situ relationships between AOM and SR in the cold seep sediments of Gulf of Mexico as well as the sediment-free AOM enrichments cultivated from cold seep of Italian Island Elba or hydrothermal vent of Guaymas Basin5. Surprisingly, we found that AOM rates strongly exceeded those of SR when high pressures and methane concentrations were applied at seep sites of GC600 and GC767 in Gulf of Mexico. With the addition of molybdate, SR was inhibited but AOM was not affected, suggesting the potential coupling of AOM with other terminal processes. Amendments of nitrate, iron, manganese and AQDS to the SR-inhibited slurries did not stimulate or inhibit the AOM activity, indicating either those electron acceptors were not limiting for AOM in the sediments or AOM was coupled to other process (e.g., organic matter). In the ANME enrichments, higher AOM rates were also observed with the addition of high concentrations of methane (10mM and 50 mM). The tracer transfer of CO2 to methane, i.e., the back reaction of AOM, increased with increasing methane concentrations and accounted for 1%-5% of the AOM rates. AOM rates at 10 mM and 50 mM methane concentration were much higher than the SR rates, suggesting those two processes were not tightly coupled. Collectively, our results provided evidence for the possible decoupling of AOM and SR under in situconditions. This decoupling appears to be widespread in methane-rich marine sediment, motivating a wide variety of future research endeavors.

Biochemical methane potential from sewage sludge: Effect of an aerobic pretreatment and fly ash addition as source of trace elements.

PubMed

Huiliñir, César; Pinto-Villegas, Paula; Castillo, Alejandra; Montalvo, Silvio; Guerrero, Lorna

2017-06-01

The effect of aerobic pretreatment and fly ash addition on the production of methane from mixed sludge is studied. Three assays with pretreated and not pretreated mixed sludge in the presence of fly ash (concentrations of 0, 10, 25, 50, 250 and 500mg/L) were run at mesophilic condition. It was found that the combined use of aerobic pretreatment and fly ash addition increases methane production up to 70% when the fly ash concentrations were lower than 50mg/L, while concentrations higher than 250mg/L cause up to 11% decrease of methane production. For the anaerobic treatment of mixed sludge without pretreatment, the fly ash improved methane generation at all the concentrations studied, with a maximum of 56%. The removal of volatile solids does not show an improvement compared to the separate use of an aerobic pre-treatment and fly ash addition. Therefore, the combined use of the aerobic pre-treatment and fly ash addition improves only the production of methane. Copyright © 2017 Elsevier Ltd. All rights reserved.

Multiband infrared inversion for low-concentration methane monitoring in a confined dust-polluted atmosphere.

PubMed

Wang, Wenzheng; Wang, Yanming; Song, Wujun; Li, Xueqin

2017-03-20

A multiband infrared diagnostic (MBID) method for methane emission monitoring in limited underground environments was presented considering the strong optical background of gas/solid attenuation. Based on spatial distribution of aerosols and complex refractive index of dust particles, forward calculations were carried out with/without methane to obtain the spectral transmittance through the participating atmosphere in a mine roadway. Considering the concurrent attenuation and absorption behavior of dust and gases, four infrared wavebands were selected to retrieve the methane concentration combined with a stochastic particle swarm optimization (SPSO) algorithm. Inversion results prove that the presented MBID method is robust and effective in identifying methane at concentrations of 0.1% or even lower with inversed relative error within 10%. Further analyses illustrate that the four selected wavebands are indispensable, and the MBID method is still valid with transmission signal disturbance in a conventional dust-polluted atmosphere under mechanized mining condition. However, the effective detection distance should be limited within 50 m to ensure inversed relative error less than 5% at 1% methane concentration.

Methane Ebullition During Simulated Lake Expansion and Permafrost Degradation

NASA Astrophysics Data System (ADS)

Mazéas, O.; von Fischer, J. C.; Whelan, M.; Rhew, R.

2007-12-01

Methane, a potent greenhouse gas, is emitted by Arctic tundra and lakes. Ebullition, or bubbling, of methane from Arctic lakes has been shown to be a major transport mechanism from the sediment to the atmosphere, and ebullition rates are greatest near the edges of the lakes where active erosion is occurring. In regions of continuous permafrost, Arctic lakes have been expanding in recent decades, attributed to permafrost melting and development of thermokarst. Lake expansion occurs when the margins erode into water, supplying large amounts of organic rich material to the sediment-water interface. This allows carbon that was previously stored in the soil (active layer and permafrost) to become bioavailable and subject to decomposition. An increase in Arctic methane emissions as a result of permafrost thawing and lake expansion would constitute a positive feedback to Arctic warming. In order to better understand these processes, an experiment was initiated in July 2007 at the Barrow Environmental Observatory, Barrow, AK. Different layers of locally collected tundra soil were placed into incubation chambers at the bottom of a shallow (about 1 m deep) lake. Each experimental chamber consists of a bucket fixed underneath an inverted funnel, with a sampling port on top to capture and collect the emitted gases. Gas samples are analyzed for methane and carbon dioxide concentrations, as well as relevant isotopic compositions. Gas sampling has occurred at frequent intervals during the late summer and will continue through the early winter. Three replicates of each layer (active layer, seasonally frozen active layer and permafrost) were incubated, as well as an empty control chamber. An additional chamber containing thawed permafrost and cellulose-rich sawdust was placed for comparison, as cellulose is a major component of plant tissue and the fermentation of the cellulose should yield substrates for methanogenesis. Total production of methane versus organic carbon content of initial sample, kinetics of ebullition, and relative potential emissions from each tundra layer will be assessed.

Quantification of methane and nitrous oxide emissions from various waste treatment facilities by tracer dilution method

NASA Astrophysics Data System (ADS)

Mønster, Jacob; Rella, Chris; Jacobson, Gloria; Kjeldsen, Peter; Scheutz, Charlotte

2013-04-01

Urban activities generate solid and liquid waste, and the handling and aftercare of the waste results in the emission of various compounds into the surrounding environment. Some of these compounds are emitted as gasses into the atmosphere, including methane and nitrous oxide. Methane and nitrous oxide are strong greenhouse gases and are considered to have 25 and 298 times the greenhouse gas potential of carbon dioxide on a hundred years term (Solomon et al. 2007). Global observations of both gasses have shown increasing concentrations that significantly contribute to the greenhouse gas effect. Methane and nitrous oxide are emitted from both natural and anthropogenic sources and inventories of source specific fugitive emissions from the anthropogenic sources of methane and nitrous oxide of are often estimated on the basis of modeling and mass balance. Though these methods are well-developed, actual measurements for quantification of the emissions is a very useful tool for verifying the modeling and mass balance as well as for validation initiatives done for lowering the emissions of methane and nitrous oxide. One approach to performing such measurements is the tracer dilution method (Galle et al. 2001, Scheutz et al. 2011), where the exact location of the source is located and a tracer gas is released at this source location at a known flow. The ratio of downwind concentrations of the tracer gas and the methane and nitrous oxide gives the emissions rates of the greenhouse gases. This tracer dilution method can be performed using both stationary and mobile measurements and in both cases, real-time measurements of both tracer and quantified gas are required, placing high demands on the analytical detection method. To perform the methane and nitrous oxide measurements, two robust instruments capable of real-time measurements were used, based on cavity ring-down spectroscopy and operating in the near-infrared spectral region. One instrument measured the methane and tracer gas concentrations while another measured the nitrous oxide concentration. We present the performance of these instruments at different waste treatment facilities (waste water treatment plants, composting facilities, sludge mineralization beds, anaerobic digesters and landfills) in Denmark, and discuss the strengths and limitations of the method of the method for quantifying methane and nitrous oxide emissions from the different sources. Furthermore, we have measured the methane emissions from 10 landfills with emission rates ranging from 5 to 135 kg/h depending on the age, state, content and aftercare of the landfill. In addition, we have studied 3 waste water treatment plants, and found nitrous oxide emission of 200 to 700 g/h from the aeration tanks and a total methane emission ranging from 2 to 15 kg/h, with the primary emission coming from the sludge treatment. References Galle, B., Samuelsson, J., Svensson, B.H., and Börjesson, G. (2001). Measurements of methane emissions from landfills using a time correlation tracer method based on FTIR absorption spectroscopy. Environmental Science & Technology 35 (1), 21-25 Scheutz, C., Samuelsson, J., Fredenslund, A. M., and Kjeldsen, P. (2011). Quantification of multiple methane emission sources at landfills using a double tracer technique. Waste Management, 31(5), 1009-17 Solomon, S., D. Qin, M. Manning, R.B. Alley, T. Berntsen, N.L. Bindoff, Z. Chen, A. Chidthaisong, J.M. Gregory, G.C. Hegerl, M. Heimann, B. Hewitson, B.J. Hoskins, F. Joos, J. Jouzel, V. Kattsov, U. Lohmann, T.Matsuno, M. Molina, N. Nicholls, J.Overpeck, G. Raga, V. Ramaswamy, J. Ren, M. Rusticucci, R. Somerville, T.F. Stocker, P. Whetton, R.A.Wood and D. Wratt, 2007: Technical Summary. In: Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA.

Anaerobic dechlorination of 2,4-dichlorophenol in freshwater sediments in the presence of sulfate.

PubMed Central

Kohring, G W; Zhang, X M; Wiegel, J

1989-01-01

In the presence of added sulfate, 2,4-dichlorophenol and 4-chlorophenol were transformed stoichiometrically to 4-chlorophenol and phenol, respectively, in anaerobic freshwater lake sediments between 18 and 40 degrees C. The concomitantly occurring sulfate reduction reduced the initial sulfate concentration from 25 mM to about 6 to 8 mM and depressed methane formation. PMID:2604410

Effect of propionic acid on citric acid fermentation in an integrated citric acid-methane fermentation process.

PubMed

Xu, Jian; Bao, Jia-Wei; Su, Xian-Feng; Zhang, Hong-Jian; Zeng, Xin; Tang, Lei; Wang, Ke; Zhang, Jian-Hua; Chen, Xu-Sheng; Mao, Zhong-Gui

2016-03-01

In this study, an integrated citric acid-methane fermentation process was established to solve the problem of wastewater treatment in citric acid production. Citric acid wastewater was treated through anaerobic digestion and then the anaerobic digestion effluent (ADE) was further treated and recycled for the next batch citric acid fermentation. This process could eliminate wastewater discharge and reduce water resource consumption. Propionic acid was found in the ADE and its concentration continually increased in recycling. Effect of propionic acid on citric acid fermentation was investigated, and results indicated that influence of propionic acid on citric acid fermentation was contributed to the undissociated form. Citric acid fermentation was inhibited when the concentration of propionic acid was above 2, 4, and 6 mM in initial pH 4.0, 4.5 and, 5.0, respectively. However, low concentration of propionic acid could promote isomaltase activity which converted more isomaltose to available sugar, thereby increasing citric acid production. High concentration of propionic acid could influence the vitality of cell and prolong the lag phase, causing large amount of glucose still remaining in medium at the end of fermentation and decreasing citric acid production.

Type and amount of organic amendments affect enhanced biogenic methane production from coal and microbial community structure

USGS Publications Warehouse

Davis, Katherine J.; Lu, Shipeng; Barnhart, Elliott P.; Parker, Albert E.; Fields, Matthew W.; Gerlach, Robin

2018-01-01

Slow rates of coal-to-methane conversion limit biogenic methane production from coalbeds. This study demonstrates that rates of coal-to-methane conversion can be increased by the addition of small amounts of organic amendments. Algae, cyanobacteria, yeast cells, and granulated yeast extract were tested at two concentrations (0.1 and 0.5 g/L), and similar increases in total methane produced and methane production rates were observed for all amendments at a given concentration. In 0.1 g/L amended systems, the amount of carbon converted to methane minus the amount produced in coal only systems exceeded the amount of carbon added in the form of amendment, suggesting enhanced coal-to-methane conversion through amendment addition. The amount of methane produced in the 0.5 g/L amended systems did not exceed the amount of carbon added. While the archaeal communities did not vary significantly, the bacterial populations appeared to be strongly influenced by the presence of coal when 0.1 g/L of amendment was added; at an amendment concentration of 0.5 g/L the bacterial community composition appeared to be affected most strongly by the amendment type. Overall, the results suggest that small amounts of amendment are not only sufficient but possibly advantageous if faster in situcoal-to-methane production is to be promoted.

Methane biofiltration using autoclaved aerated concrete as the carrier material.

PubMed

Ganendra, Giovanni; Mercado-Garcia, Daniel; Hernandez-Sanabria, Emma; Boeckx, Pascal; Ho, Adrian; Boon, Nico

2015-09-01

The methane removal capacity of mixed methane-oxidizing bacteria (MOB) culture in a biofilter setup using autoclaved aerated concrete (AAC) as a highly porous carrier material was tested. Batch experiment was performed to optimize MOB immobilization on AAC specimens where optimum methane removal was obtained when calcium chloride was not added during bacterial inoculation step and 10-mm-thick AAC specimens were used. The immobilized MOB could remove methane at low concentration (~1000 ppmv) in a biofilter setup for 127 days at average removal efficiency (RE) of 28.7 %. Unlike a plug flow reactor, increasing the total volume of the filter by adding a biofilter in series did not result in higher total RE. MOB also exhibited a higher abundance at the bottom of the filter, in proximity with the methane gas inlet where a high methane concentration was found. Overall, an efficient methane biofilter performance could be obtained using AAC as the carrier material.

Microbial production and oxidation of methane in deep subsurface

NASA Astrophysics Data System (ADS)

Kotelnikova, Svetlana

2002-10-01

The goal of this review is to summarize present studies on microbial production and oxidation of methane in the deep subterranean environments. Methane is a long-living gas causing the "greenhouse" effect in the planet's atmosphere. Earlier, the deep "organic carbon poor" subsurface was not considered as a source of "biogenic" methane. Evidence of active methanogenesis and presence of viable methanogens including autotrophic organisms were obtained for some subsurface environments including water-flooded oil-fields, deep sandy aquifers, deep sea hydrothermal vents, the deep sediments and granitic groundwater at depths of 10 to 2000 m below sea level. As a rule, the deep subterranean microbial populations dwell at more or less oligotrophic conditions. Molecular hydrogen has been found in a variety of subsurface environments, where its concentrations were significantly higher than in the tested surface aquatic environments. Chemolithoautotrophic microorganisms from deep aquifers that could grow on hydrogen and carbon dioxide can act as primary producers of organic carbon, initiating heterotrophic food chains in the deep subterranean environments independent of photosynthesis. "Biogenic" methane has been found all over the world. On the basis of documented occurrences, gases in reservoirs and older sediments are similar and have the isotopic character of methane derived from CO 2 reduction. Groundwater representing the methanogenic end member are characterized by a relative depletion of dissolved organic carbon (DOC) in combination with an enrichment in 13C in inorganic carbon, which is consistent with the preferential reduction of 12CO 2 by autotrophic methanogens or acetogens. The isotopic composition of methane formed via CO 2 reduction is controlled by the δ13C of the original CO 2 substrate. Literature data shows that CH 4 as heavy as -40‰ or -50‰ can be produced by the microbial reduction of isotopically heavy CO 2. Produced methane may be oxidized microbially to carbon dioxide. Microbial methane oxidation is a biogeochemical process that limits the release of methane, a greenhouse gas from anaerobic environments. Anaerobic methane oxidation plays an important role in marine sediments. Similar processes may take place in deep subsurface and thus fuel the deep microbial community. Organisms or consortia responsible for anaerobic methane oxidation have not yet been cultured, although diverse aerobic methanotrophs have been isolated from a variety of underground niches. The presence of aerobic methanotrophs in the anoxic subsurface remains to be explained. The presence of methane in the deep subsurface have been shown all over the world. The flux of gases between the deep subsurface and the atmosphere is driven by the concentration gradient from depth to the atmosphere. However, methane is consumed by methanotrophs on the way of its evolution in oxidized environments and is transformed to organic form, available for further microbial processing. When the impact of subsurface environments to global warming is estimated, it is necessary to take into account the activity of methane-producing Archaea and methane-oxidizing biofilters in groundwater. Microbial production and oxidation of methane is involved in the carbon cycle in the deep subsurface environments.

Aerobic methane production in surface waters of the Gulf of Mexico

NASA Astrophysics Data System (ADS)

Finke, N.; Crespo-Medina, M.; Schweers, J.; Joye, S. B.

2011-12-01

Near surface water of the global oceans often show elevated methane concentrations compared to the water column below with concentrations in supersaturation in regard to the atmosphere (Lamontagne et al. 1973), resulting in a source of this potent greenhouse gas to the atmosphere. The mechanisms leading to methane supersaturation in surface waters remains unclear. Incubations with Trichodesmium-containing Pacific surface water suggested methylphosphonate as potential methane precursor under phosphate limiting conditions (Karl et al. 2008), whereas in phosphate rich Arctic surface waters, DMSP addition stimulated methane production (Damm et al. 2010). Surface waters of the Gulf of Mexico typically exhibit a methane maximum that is conincident with the deep chlorophyll maximum, below the depths where Trichodesmium is abundant. Addition of methylphosphonate, dimethylsulfoniopropionate (DMSP) or methane thiol (MeSH), the proposed methane precursor in DMSP conversion to methane, to oxic sea water did not affect methane production within the chlorophyll maximum at most stations, whereas methyl phosphonate addition stimulated methane production in the surface water and proposed deep Trichodesmium horizon. Pre-filtration of the water through a 10 μm sieve, which eliminated Trichodesmium, or through a 1.2 μm filter, which eliminated additional cyanobacteria such as Synechococcus, did not reduce methane production. Under dark oxic and dark anoxic conditions, however, methane production was reduced 5 and 7-20 fold, respectively, indicating that anerobic methane production in anoxic microniches is not responsible for the methane production. The reduction of methane production under dark conditions suggests that methane production is, in some yet unrecognized way, linked to phototrophic metabolism. Cyanobacteria are likely not responsible for the observed aerobic methane production in the surface waters of the Gulf of Mexico and while methylphosphonate is a potential precursor in the surface waters, the precursor and methanism of methane production within the coincident deep chlorophyll/methane maximum remains unknown. Lamontagne R, Swinnert J, Linnenbo V, Smith WD (1973) Methane concentrations in various marine environments. Journal of Geophysical Research 78, 5317-5324 Karl DM et al. (2008) Aerobic production of methane in the sea. Nature Geosciences 1, 473-478 Damm E et al. (2010) Methane production in aerobic oligotrophic surface water in the central Arctic Ocean. Biogeosciences 7, 1099-1108

Optical fiber network sensor system for monitoring methane concentration

NASA Astrophysics Data System (ADS)

Zhang, Zhi-wei; Zhang, Ji-long

2011-08-01

With regard to the high accuracy optic-fiber sensor for monitoring methane concentration, the choice of light source depends on methane peak values. Besides, the environment of mine should be considered, that is to say other gas should be considered, such as vapor, CO and CO2 etc, without absorbent spectrum in the decided wavelength. It has been reported that vapor, CO and CO2 have no obvious absorption in 0.85μm, 1.3μm and 1.66μm area, CH4 has no obvious absorption in 0.85μm area. So diode laser with 1.3μm or 1.66μm peak wavelength is chosen as the optic-fiber sensor's light source for detecting methane concentration. On the basis of the principle of optic absorption varied with methane concentration at its characteristic absorbent wavelength, the advantage of optic-fiber sensor technology and the circumstance characteristic of the coal mine. An optic-fiber sensor system is presented for monitoring methane concentration. Space Division Multiple Access Technology (SDMAT) and long optical path absorbent pool technology are combined in the study. Considering the circumstance characteristic of the coal mine, the optic-fiber network sensors for detecting methane concentration from mix gas of vapor, CO, CH4 and CO2 are used. It introduces the principle of an optic-fiber sensor system for monitoring methane concentration in coal mine. It contains the structure block diagram of monitoring system, the system is mainly made up of diode laser for monitoring methane concentration, Y-shaped photo-coupler with coupled rate 50:50, optical switch 1×2, gas absorbent cell, the computer data process and control system and photoelectric transformer. In this study, in order to decrease to the influence of the dark-current of photodiode, intensity in light sources and temperature drifts of processing circuit on the system accuracy in measurement, a beam of light is broken down into two beams in the coupler of Y-shaped coupler, the one acts as the reference optical path, the other is known as the sensing optical path. The experimental result shows that diode laser with 1654.141nm in wavelength is taken as the optic source for detecting methane concentration, the detective limit of the sensor is below 4.274mg/m3 when the optical path of absorbent pool is 20 centimeters, and the prevision and stability could satisfy practical application. The whole instrument can also reach on-line measurement with multiple points on different spot.

A hydrothermal seep on the Costa Rica margin: middle ground in a continuum of reducing ecosystems

PubMed Central

Levin, Lisa A.; Orphan, Victoria J.; Rouse, Greg W.; Rathburn, Anthony E.; Ussler, William; Cook, Geoffrey S.; Goffredi, Shana K.; Perez, Elena M.; Waren, Anders; Grupe, Benjamin M.; Chadwick, Grayson; Strickrott, Bruce

2012-01-01

Upon their initial discovery, hydrothermal vents and methane seeps were considered to be related but distinct ecosystems, with different distributions, geomorphology, temperatures, geochemical properties and mostly different species. However, subsequently discovered vents and seep systems have blurred this distinction. Here, we report on a composite, hydrothermal seep ecosystem at a subducting seamount on the convergent Costa Rica margin that represents an intermediate between vent and seep ecosystems. Diffuse flow of shimmering, warm fluids with high methane concentrations supports a mixture of microbes, animal species, assemblages and trophic pathways with vent and seep affinities. Their coexistence reinforces the continuity of reducing environments and exemplifies a setting conducive to interactive evolution of vent and seep biota. PMID:22398162

Mechanism of Methane Transport from the Rhizosphere to the Atmosphere through Rice Plants 1

PubMed Central

Nouchi, Isamu; Mariko, Shigeru; Aoki, Kazuyuki

1990-01-01

To clarify the mechanisms of methane transport from the rhizosphere into the atmosphere through rice plants (Oryza sativa L.), the methane emission rate was measured from a shoot whose roots had been kept in a culture solution with a high methane concentration or exposed to methane gas in the gas phase by using a cylindrical chamber. No clear correlation was observed between change in the transpiration rate and that in the methane emission rate. Methane was mostly released from the culm, which is an aggregation of leaf sheaths, but not from the leaf blade. Micropores which are different from stomata were newly found at the abaxial epidermis of the leaf sheath by scanning electron microscopy. The measured methane emission rate was much higher than the calculated methane emission rate that would result from transpiration and the methane concentration in the culture solution. Rice roots could absorb methane gas in the gas phase without water uptake. These results suggest that methane dissolved in the soil water surrounding the roots diffuses into the cell-wall water of the root cells, gasifies in the root cortex, and then is mostly released through the micropores in the leaf sheaths. Images Figure 7 PMID:16667719

Atmospheric Impacts of Emissions from Oil and Gas Development in the Uintah Basin, Utah, USA

NASA Astrophysics Data System (ADS)

Helmig, D.; Boylan, P. J.; Hueber, J.; Van Dam, B. A.; Mauldin, L.; Parrish, D. D.

2012-12-01

In the Uintah Basin in northeast Utah, USA, surface ozone levels during winter months have approached and on occasion exceeded the US National Ambient Air Quality Standard (NAAQS). Emissions from the extensive oil and gas exploration in this region are suspected to be the cause of these ozone episodes; however emission rates and photochemical processes are uncertain. During February 2012 continuous surface measurements and vertical profiling from a tethered balloon platform at the Horsepool site yielded high resolution boundary layer profile data on ozone and ozone precursor compounds, i.e. nitrogen oxides and volatile organic compounds as well as methane. Findings from this study were: 1. Surface ozone during the study period, which had no snow cover, did not exceed the NAAQS. 2. Nitrogen oxides varied from 1-50 ppbv pointing towards significant emission sources, likely from oil and gas operations. 3. Methane concentrations were elevated, reaching up to ~10 times its Northern Hemisphere (NH) atmospheric background. 3. Light non-methane hydrocarbons (NMHC) constituted the main fraction of volatile organic compounds. NMHC concentrations were highly elevated, exceeding levels seen in urban areas. 4. Ozone, methane, NOx and VOC showed distinct diurnal cycles, with large concentration increases seen at night, except for ozone, which showed the opposite behavior. 5. During nighttime concentrations of NOx, NMHC, and methane built up near the surface to levels that were much higher than their daytime concentrations. 6. Comparing NMHC to methane concentrations indicates a mass flux ratio of ~30% for total VOC/methane emissions for the Uintah Basin.

Quantification of Methane Gas Flux and Bubble Fate on the Eastern Siberian Arctic Shelf Utilizing Calibrated Split-beam Echosounder Data.

NASA Astrophysics Data System (ADS)

Weidner, E. F.; Mayer, L. A.; Weber, T. C.; Jerram, K.; Jakobsson, M.; Chernykh, D.; Ananiev, R.; Mohammad, R.; Semiletov, I. P.

2016-12-01

On the Eastern Siberian Arctic Shelf (ESAS) subsea permafrost, shallow gas hydrates, and trapped free gas hold an estimated 1400 Gt of methane. Recent observations of methane bubble plumes and high concentrations of dissolved methane in the water column indicate methane release via ebullition. Methane gas released from the shallow ESAS (<50 m average depth) has high potential to be transported to the atmosphere. To directly and quantitatively address the magnitude of methane flux and the fate of rising bubbles in the ESAS, methane seeps were mapped with a broadband split-beam echosounder as part of the Swedish-Russian-US Arctic Ocean Investigation of Climate-Cryosphere-Carbon Interactions program (SWERUS-C3). Acoustic measurements were made over a broad range of frequencies (16 to 29 kHz). The broad bandwidth provided excellent discrimination of individual targets in the water column, allowing for the identification of single bubbles. Absolute bubble target strength values were determined by compensating apparent target strength measurements for beam pattern effects via standard calibration techniques. The bubble size distribution of seeps with individual bubble signatures was determined by exploiting bubble target strength models over the broad range of frequencies. For denser seeps, with potential higher methane flux, bubble size distribution was determined via extrapolation from seeps in similar geomorphological settings. By coupling bubble size distributions with rise velocity measurements, which are made possible by split-beam target tracking, methane gas flux can be estimated. Of the 56 identified seeps in the SWERUS data set, individual bubbles scatterers were identified in more than half (31) of the seeps. Preliminary bubble size distribution results indicate bubble radii range from 0.75 to 3.0 mm, with relatively constant bubble size distribution throughout the water column. Initial rise velocity observations indicate bubble rise velocity increases with decreasing depth, seemingly independent of bubble radius.

Sources and Fluxes of Atmospheric Methane from Lakes in the Alaskan Arctic

NASA Astrophysics Data System (ADS)

Townsend-Small, A.; Akerstrom, F.; Hinkel, K. M.; Arp, C. D.; Beck, R. A.; Grosse, G.; Jones, B. M.; Kim, C.; Lenters, J. D.; Liu, H.; Eisner, W. R.

2014-12-01

Climate warming in the Arctic may result in release of carbon dioxide and/or methane from thawing permafrost soils, resulting in a positive feedback to warming. Permafrost thaw may also result in release of methane from previously trapped natural gas. The Arctic landscape is approximately 50% covered by shallow permafrost lakes, and these environments may serve as bellwethers for climate change - carbon cycle feedbacks, since permafrost thaw is generally deeper under lakes than tundra soils. Since 2011, the Circum-Arctic Lakes Observation Network (CALON) project has documented landscape-scale variability in physical and biogeochemical processes of Arctic lakes in permafrost terrain, including carbon cycle feedbacks to climate warming. Here we present a dataset of concentrations, isotope ratios (13C and 2H), and atmospheric fluxes of methane from lakes in Arctic Alaska. Concentrations of methane in lake water ranged from 0.3 to 43 micrograms per liter, or between 6 and 750 times supersaturated with respect to air. Isotopic measurements of dissolved methane indicated that most of the lakes had methane derived from anaerobic organic matter decomposition, but that some lakes may have a small source of methane from fossil fuel sources such as natural gas or coal beds. Concurrent measurements of methane fluxes and dissolved methane concentrations in summer of 2014 will aid in translating routine dissolved measurements into fluxes, and will also elucidate the relative importance of diffusive versus ebulliative fluxes. It is essential that measurements of methane emissions from Arctic lakes be continued long-term to determine whether methane emissions are on the rise, and whether warming of the lakes leads to increased venting of fossil fuel methane from enhanced thaw of permafrost beneath the lakes.

Selection of associated heterotrophs by methane-oxidizing bacteria at different copper concentrations.

PubMed

van der Ha, David; Vanwonterghem, Inka; Hoefman, Sven; De Vos, Paul; Boon, Nico

2013-03-01

Due to the increasing atmospheric concentration of the greenhouse gas methane, more knowledge is needed on the management of methanotrophic communities. While most studies have focused on the characteristics of the methane-oxidizing bacteria (MOB), less is known about their interactions with the associated heterotrophs. Interpretative tools based on denaturing gradient gel electrophoresis allowed to evaluate the influence of copper-an important enzymatic regulator for MOB-on the activity and composition of the bacterial community. Over 30 days, enrichments with 0.1, 1.0 and 10 μM Cu(2+) respectively, showed comparable methane oxidation activities. The different copper concentrations did not create major shifts in the methanotrophic communities, as a Methylomonas sp. was able to establish dominance at all different copper concentrations by switching between both known methane monooxygenases. The associated heterotrophic communities showed continuous shifts, but over time all cultures evolved to a comparable composition, independent of the copper concentration. This indicates that the MOB selected for certain heterotrophs, possibly fulfilling vital processes such as removal of toxic compounds. The presence of a large heterotrophic food web indirectly depending on methane as sole carbon and energy source was confirmed by a clone library wherein MOB only formed a minority of the identified species.

Simulations of Flame Acceleration and DDT in Mixture Composition Gradients

NASA Astrophysics Data System (ADS)

Zheng, Weilin; Kaplan, Carolyn; Houim, Ryan; Oran, Elaine

2017-11-01

Unsteady, multidimensional, fully compressible numerical simulations of methane-air in an obstructed channel with spatial gradients in equivalence ratios have been carried to determine the effects of the gradients on flame acceleration and transition to detonation. Results for gradients perpendicular to the propagation direction were considered here. A calibrated, optimized chemical-diffusive model that reproduces correct flame and detonation properties for methane-air over a range of equivalence ratios was derived from a combination of a genetic algorithm with a Nelder-Mead optimization scheme. Inhomogeneous mixtures of methane-air resulted in slower flame acceleration and longer distance to DDT. Detonations were more likely to decouple into a flame and a shock under sharper concentration gradients. Detailed analyses of temperature and equivalence ratio illustrated that vertical gradients can greatly affect the formation of hot spots that initiate detonation by changing the strength of leading shock wave and local equivalence ratio near the base of obstacles. This work is supported by the Alpha Foundation (Grant No. AFC215-20).

The anaerobic digestion of biologically and physicochemically pretreated oily wastewater.

PubMed

Peng, Liyu; Bao, Meidan; Wang, Qingfeng; Wang, Fangchao; Su, Haijia

2014-01-01

To enhance the degradation of oily wastewater and its biogas production, a biological-physicochemical pretreatment was introduced prior to the anaerobic digestion system. The digestion thereafter proceeded more efficiently due to the inoculation by oil degrading bacteria (Bacillus). A 2-stage pre-mixing is more effective than directly mixing. The effects on the methane production were also investigated by pre-treatment with ultrasonic (US) treatment, combined with citric acid (CA) addition. US pre-treatment was found to improve the initial methane production, and CA pre-treatment could maintain this improvement during the whole digestion stage. Pre-mixing Bacillus at 9 wt.% inoculation, combined with US for 10 min and a CA concentration of 500 mg/L provided the optimum conditions. The most effective enhancement of methane yield was 1100.46 ml/g VS, exceeding that of the control by 280%. The change of coenobium shape and fatty acid content further proved that such pretreatment of oily wastewater can facilitate digestion. Copyright © 2013 Elsevier Ltd. All rights reserved.

Effect of silane concentration on the supersonic combustion of a silane/methane mixture

NASA Technical Reports Server (NTRS)

Northam, G. B.; Mclain, A. G.; Pellett, G. L.; Diskin, G. S.

1986-01-01

A series of direct connect combustor tests was conducted to determine the effect of silane concentration on the supersonic combustion characteristics of silane/methane mixtures. Shock tube ignition delay data indicated more than an order of magnitude reduction in ignition delay times for both 10 and 20 percent silane/methane mixtures as compared to methane. The ignition delay time of the 10 percent mixture was only a factor of 2.3 greater than that of the 20 percent mixture. Supersonic combustion tests were conducted with the fuel injected into a model scramjet combustor. The combustor was mounted at the exit of a Mach 2 nozzle and a hydrogen fired heater was used to provide a variation in test gas total temperature. Tests using the 20 percent silane/methane mixture indicated considerable combustion enhancement when compared to methane alone. This mixture had an autoignition total temperature of 1650 R. This autoignition temperature can be contrasted with 2330 R for hydrogen and 1350 R for a 20 percent silane/hydrogen mixture in similar hardware. Methane without the silane additive did not autoignite in this configuration at total temperatures as high as 3900 R, the maximum temperature at which tests were conducted. Supersonic combustion tests with the silane concentration reduced to 10 percent indicated little improvement in combustion performance over pure methane. The addition of 20 percent silane to methane resulted in a pyrophoric fuel with good supersonic combustion performance. Reducing the silane concentration below this level, however, yielded a less pyrophoric fuel that exhibited poor supersonic combustion performance.

Slaughterhouse by-products treatment using anaerobic digestion.

PubMed

Moukazis, Ioannis; Pellera, Frantseska-Maria; Gidarakos, Evangelos

2018-01-01

The objective of the present study is to evaluate the use of animal by-products (ABP) as substrates for anaerobic digestion, aiming at methane production. Specifically, four ABP of Category 2 and 3, namely (i) stomach and rumen, (ii) stomach contents, (iii) breasts and reproductive organs and (iv) bladders and intestines with their contents, were selected. The methane potential of each ABP was initially determined, while the feasibility of anaerobic co-digestion of ABP with two agroindustrial waste, i.e. orange peels and olive leaves was also studied. To this purpose, Biochemical Methane Potential (BMP), as well as semi-continuous assays were respectively conducted. In the latter, the effect of the variation in the organic loading rate (OLR) on methane production was investigated. Results obtained from BMP assays showed that the samples containing breasts and reproductive organs, bladders and intestine, and stomach and rumen, had higher methane potentials of 815, 787 and 759 mLCH 4,STP /gVS, respectively. Moreover, according to the results of the semi-continuous assays, maximum methane yields between 253 and 727mLCH 4 /gVS fed were obtained at an OLR of 0.8gVS/L/d. The only case in which methanogenesis inhibition phenomena, due to increased ammonia concentrations, were observed, was the assay being fed with a mixture of breasts and reproductive organs and orange peels, at the highest OLR. This inhibition phenomenon was attributed to an inappropriate C/N ratio. Copyright © 2017 Elsevier Ltd. All rights reserved.

Co-digestion of domestic kitchen waste and night soil sludge in a full-scale sludge treatment plant.

PubMed

Yoneyama, Y; Takeno, K

2002-01-01

A study was made on the domestic kitchen waste and night soil treatment performance of a full-scale sludge treatment plant. The sludge treatment at this plant was by thermophilic methane fermentation. The initial treatment, mesophilic to thermophilic fermentation, was able to be started up within a short time by adjusting the amount of influent waste. Thermophilic methane fermentation was carried out for five months (May-October) and the performance under a mean residual time of 22 days indicated a VTS decomposition of 42%, gas generation of 54-1,610 m3/day (average: 755 m3/day), and a mean methane concentration of 60%. The methane gas was used to generate power in the plant and the amount of power generated by methane gas was highest in October (average of 1,200 kWh/day). This was equivalent to about 7% of the power consumed at the entire sludge treatment plant. The BOD/NH4-N of the activated sludge influent water was lower, compared to a case where there is no recycle flow, due to the recycle flow from the methane fermentation process. There was, therefore, a tendency for an increase in the amount of methanol charged into the secondary denitrification tank. However, the quality of the effluent was satisfactory (BOD< 10 mg/L, SS< 5 mg/L, and T-N< 25 mg/L). Study results indicated that it was possible to implement a full-scale plant for recovering organic waste.

Effects of low oxygen concentrations on aerobic methane oxidation in seasonally hypoxic coastal waters

NASA Astrophysics Data System (ADS)

Steinle, Lea; Maltby, Johanna; Treude, Tina; Kock, Annette; Bange, Hermann W.; Engbersen, Nadine; Zopfi, Jakob; Lehmann, Moritz F.; Niemann, Helge

2017-03-01

Coastal seas may account for more than 75 % of global oceanic methane emissions. There, methane is mainly produced microbially in anoxic sediments from which it can escape to the overlying water column. Aerobic methane oxidation (MOx) in the water column acts as a biological filter, reducing the amount of methane that eventually evades to the atmosphere. The efficiency of the MOx filter is potentially controlled by the availability of dissolved methane and oxygen, as well as temperature, salinity, and hydrographic dynamics, and all of these factors undergo strong temporal fluctuations in coastal ecosystems. In order to elucidate the key environmental controls, specifically the effect of oxygen availability, on MOx in a seasonally stratified and hypoxic coastal marine setting, we conducted a 2-year time-series study with measurements of MOx and physico-chemical water column parameters in a coastal inlet in the south-western Baltic Sea (Eckernförde Bay). We found that MOx rates generally increased toward the seafloor, but were not directly linked to methane concentrations. MOx exhibited a strong seasonal variability, with maximum rates (up to 11.6 nmol L-1 d-1) during summer stratification when oxygen concentrations were lowest and bottom-water temperatures were highest. Under these conditions, 2.4-19.0 times more methane was oxidized than emitted to the atmosphere, whereas about the same amount was consumed and emitted during the mixed and oxygenated periods. Laboratory experiments with manipulated oxygen concentrations in the range of 0.2-220 µmol L-1 revealed a submicromolar oxygen optimum for MOx at the study site. In contrast, the fraction of methane-carbon incorporation into the bacterial biomass (compared to the total amount of oxidized methane) was up to 38-fold higher at saturated oxygen concentrations, suggesting a different partitioning of catabolic and anabolic processes under oxygen-replete and oxygen-starved conditions, respectively. Our results underscore the importance of MOx in mitigating methane emission from coastal waters and indicate an organism-level adaptation of the water column methanotrophs to hypoxic conditions.

30 CFR 75.323 - Actions for excessive methane.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 30 Mineral Resources 1 2013-07-01 2013-07-01 false Actions for excessive methane. 75.323 Section... excessive methane. (a) Location of tests. Tests for methane concentrations under this section shall be made.... (1) When 1.0 percent or more methane is present in a working place or an intake air course, including...

30 CFR 75.323 - Actions for excessive methane.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 30 Mineral Resources 1 2011-07-01 2011-07-01 false Actions for excessive methane. 75.323 Section... excessive methane. (a) Location of tests. Tests for methane concentrations under this section shall be made.... (1) When 1.0 percent or more methane is present in a working place or an intake air course, including...

30 CFR 75.323 - Actions for excessive methane.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 30 Mineral Resources 1 2014-07-01 2014-07-01 false Actions for excessive methane. 75.323 Section... excessive methane. (a) Location of tests. Tests for methane concentrations under this section shall be made.... (1) When 1.0 percent or more methane is present in a working place or an intake air course, including...

30 CFR 75.323 - Actions for excessive methane.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 30 Mineral Resources 1 2012-07-01 2012-07-01 false Actions for excessive methane. 75.323 Section... excessive methane. (a) Location of tests. Tests for methane concentrations under this section shall be made.... (1) When 1.0 percent or more methane is present in a working place or an intake air course, including...

30 CFR 75.323 - Actions for excessive methane.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 30 Mineral Resources 1 2010-07-01 2010-07-01 false Actions for excessive methane. 75.323 Section... excessive methane. (a) Location of tests. Tests for methane concentrations under this section shall be made.... (1) When 1.0 percent or more methane is present in a working place or an intake air course, including...

Extreme methane emissions from a Swiss hydropower reservoir: contribution from bubbling sediments.

PubMed

Delsontro, Tonya; McGinnis, Daniel F; Sobek, Sebastian; Ostrovsky, Ilia; Wehrli, Bernhard

2010-04-01

Methane emission pathways and their importance were quantified during a yearlong survey of a temperate hydropower reservoir. Measurements using gas traps indicated very high ebullition rates, but due to the stochastic nature of ebullition a mass balance approach was crucial to deduce system-wide methane sources and losses. Methane diffusion from the sediment was generally low and seasonally stable and did not account for the high concentration of dissolved methane measured in the reservoir discharge. A strong positive correlation between water temperature and the observed dissolved methane concentration enabled us to quantify the dissolved methane addition from bubble dissolution using a system-wide mass balance. Finally, knowing the contribution due to bubble dissolution, we used a bubble model to estimate bubble emission directly to the atmosphere. Our results indicated that the total methane emission from Lake Wohlen was on average >150 mg CH(4) m(-2) d(-1), which is the highest ever documented for a midlatitude reservoir. The substantial temperature-dependent methane emissions discovered in this 90-year-old reservoir indicate that temperate water bodies can be an important but overlooked methane source.

Archaeal abundance in post-mortem ruminal digesta may help predict methane emissions from beef cattle

NASA Astrophysics Data System (ADS)

Wallace, R. John; Rooke, John A.; Duthie, Carol-Anne; Hyslop, Jimmy J.; Ross, David W.; McKain, Nest; de Souza, Shirley Motta; Snelling, Timothy J.; Waterhouse, Anthony; Roehe, Rainer

2014-07-01

Methane produced from 35 Aberdeen-Angus and 33 Limousin cross steers was measured in respiration chambers. Each group was split to receive either a medium- or high-concentrate diet. Ruminal digesta samples were subsequently removed to investigate correlations between methane emissions and the rumen microbial community, as measured by qPCR of 16S or 18S rRNA genes. Diet had the greatest influence on methane emissions. The high-concentrate diet resulted in lower methane emissions (P < 0.001) than the medium-concentrate diet. Methane was correlated, irrespective of breed, with the abundance of archaea (R = 0.39), bacteria (-0.47), protozoa (0.45), Bacteroidetes (-0.37) and Clostridium Cluster XIVa (-0.35). The archaea:bacteria ratio provided a stronger correlation (0.49). A similar correlation was found with digesta samples taken 2-3 weeks later at slaughter. This finding could help enable greenhouse gas emissions of large animal cohorts to be predicted from samples taken conveniently in the abattoir.

Pasture-scale measurement of methane emissions of grazing cattle

USDA-ARS?s Scientific Manuscript database

Quantifying methane emission of cattle grazing on southern Great Plains pastures using micrometeorology presents several challenges. Cattle are elevated, mobile point sources of methane, so that knowing their location in relation to atmospheric methane concentration measurements becomes critical. St...

Tylosin effect on methanogenesis in an anaerobic biomass from swine wastewater treatment.

PubMed

García-Sánchez, Liliana; Garzón-Zúñiga, Marco Antonio; Buelna, Gerardo; Estrada-Arriaga, Edson Baltazar

2016-01-01

The effect of different concentrations of tylosin on methane production was investigated: first methanogenesis in a biomass without contact with the antibiotic, and later the ability of the sludge to adapt to increasing concentrations of tylosin. Results showed that, for biomass that had no contact with the antibiotic, the presence of tylosin inhibits the generation of methane even at concentrations as small as 0.01 mg L(-1), and samples at concentrations above 0.5 mg L(-1) produced practically no methane, whereas, in the digesters acclimated in the presence of tylosin at a concentration of 0.01 to 0.065 mg L(-1), methanogenesis is not inhibited in the presence of antibiotic and the generation of methane is improved. This behaviour suggests the microorganisms have developed not only resistance to the antibiotic but also an ability to metabolize it.

Linking Microbial and Biogeochemical Studies: Biological Controls of Methane Release from an Acidic Natural Wetland in Central Pennsylvania

NASA Astrophysics Data System (ADS)

Biddle, J. F.; Turich, C.; Brantley, S.; Bruns, M.

2002-12-01

Wetlands produce between 55 and 150 Tg of methane per year, or ~70% of all natural methane, and 20% of total methane (natural and anthropogenic). Understanding inputs to the global methane cycle depends on integrated in situ study of the sources and sinks of methane, as well as the rate and magnitude of methane production and consumption. Bear Meadows Natural Area in central Pennsylvania (N 40° 43.796' W 077° 45.310; 554 m elevation) contains an acidic, methane-producing, peaty bog with vegetation that is typical of wetlands at higher latitudes. In this four year study conducted within a cross-disciplinary training course offered by the NSF-IGERT Biogeochemical Research Initiative in Education (BRIE) program at Penn State University, graduate students applied a combination of geochemical and microbiological techniques to explore microbial diversity and activity in Bear Meadows sediments. The methane flux at the peat:water interface was highly variable, from 0.01 to over 3000 umol/m2/min in both sphagnum and sedge vegetation. The methane released from the bog had a carbon isotopic composition of -60 %o, typical of biogenic methane. Analysis of peat pore waters showed that the most methane was produced 30 cm below the peat:water interface, with a broad peak of methane in pore waters from 20-40 cm. At 21 cm below the peat:water interface, profiles of Archaeal 16S-23S ribosomal RNA spacer regions revealed the presence of populations having 92% similarity to 16S rRNA sequences of Methanoculleus marisnigri. Phospholipid fatty acids (PLFA) and compound specific isotope analysis revealed other biological controls on the methane cycle. PLFAs typical of methanotrophic bacteria were also present within peat cores from 20-30 cm below the water interface. The depleted carbon isotopic composition of these biomarkers (C16:1 and C18:1 fatty acids) was - 31.4 %o and - 33.8%o, indicative of methane oxidation. The presence of biomarkers of methane oxidizing bacteria within the zone of methane production may indicate that there is temporal or spatial heterogeneity in oxygen concentration within the peat. This interdisciplinary approach helped define specific ecological niches where novel methanogens and methane oxidizers may be active in a typical northern wetland. Through BRIE, on-going studies of the Bear Meadows wetland will focus on detecting other potentially novel aerobic and anaerobic microbes, and determining the biological influence on methane release to the atmosphere.

Improved enrichment culture technique for methane-oxidizing bacteria from marine ecosystems: the effect of adhesion material and gas composition.

PubMed

Vekeman, Bram; Dumolin, Charles; De Vos, Paul; Heylen, Kim

2017-02-01

Cultivation of microbial representatives of specific functional guilds from environmental samples depends largely on the suitability of the applied growth conditions. Especially the cultivation of marine methanotrophs has received little attention, resulting in only a limited number of ex situ cultures available. In this study we investigated the effect of adhesion material and headspace composition on the methane oxidation activity in methanotrophic enrichments obtained from marine sediment. Addition of sterilized natural sediment or alternatively the addition of acid-washed silicon dioxide significantly increased methane oxidation. This positive effect was attributed to bacterial adhesion on the particles via extracellular compounds, with a minimum amount of particles required for effect. As a result, the particles were immobilized, thus creating a stratified environment in which a limited diffusive gas gradients could build up and various microniches were formed. Such diffusive gas gradient might necessitate high headspace concentrations of CH 4 and CO 2 for sufficient concentrations to reach the methane-oxidizing bacteria in the enrichment culture technique. Therefore, high concentrations of methane and carbon dioxide, in addition to the addition of adhesion material, were tested and indeed further stimulated methane oxidation. Use of adhesion material in combination with high concentrations of methane and carbon dioxide might thus facilitate the cultivation and subsequent enrichment of environmentally important members of this functional guild. The exact mechanism of the observed positive effects on methane oxidation and the differential effect on methanotrophic diversity still needs to be explored.

Role of Megafauna and Frozen Soil in the Atmospheric CH4 Dynamics

PubMed Central

Zimov, Sergey; Zimov, Nikita

2014-01-01

Modern wetlands are the world’s strongest methane source. But what was the role of this source in the past? An analysis of global 14C data for basal peat combined with modelling of wetland succession allowed us to reconstruct the dynamics of global wetland methane emission through time. These data show that the rise of atmospheric methane concentrations during the Pleistocene-Holocene transition was not connected with wetland expansion, but rather started substantially later, only 9 thousand years ago. Additionally, wetland expansion took place against the background of a decline in atmospheric methane concentration. The isotopic composition of methane varies according to source. Owing to ice sheet drilling programs past dynamics of atmospheric methane isotopic composition is now known. For example over the course of Pleistocene-Holocene transition atmospheric methane became depleted in the deuterium isotope, which indicated that the rise in methane concentrations was not connected with activation of the deuterium-rich gas clathrates. Modelling of the budget of the atmospheric methane and its isotopic composition allowed us to reconstruct the dynamics of all main methane sources. For the late Pleistocene, the largest methane source was megaherbivores, whose total biomass is estimated to have exceeded that of present-day humans and domestic animals. This corresponds with our independent estimates of herbivore density on the pastures of the late Pleistocene based on herbivore skeleton density in the permafrost. During deglaciation, the largest methane emissions originated from degrading frozen soils of the mammoth steppe biome. Methane from this source is unique, as it is depleted of all isotopes. We estimated that over the entire course of deglaciation (15,000 to 6,000 year before present), soils of the mammoth steppe released 300–550 Pg (1015 g) of methane. From current study we conclude that the Late Quaternary Extinction significantly affected the global methane cycle. PMID:24695117

Pond Hockey on Whitmore Lacus: the Formation of Ponds and Ethane Ice Deposits Following Storm Events on Titan

NASA Astrophysics Data System (ADS)

Steckloff, Jordan; Soderblom, Jason M.

2017-10-01

Cassini ISS observations reveled regions, later identified as topographic low spots (Soderblom et al. 2014, DPS) on Saturn’s moon Titan become significantly darker (lower albedo) following storm events (Turtle et al. 2009, GRL; 2011, Science), suggesting pools of liquid hydrocarbon mixtures (predominantly methane-ethane-nitrogen). However, these dark ponds then significantly brighten (higher albedo relative to pre-storm albedo), before fading to their pre-storm albedos (Barnes et al. 2013 Planet. Sci; Soderblom et al. 2014, DPS). We interpret these data to be the result of ethane ice formation, which cools from evaporation of methane. The formation of ethane ices results from a unique sequence of thermophysical processes. Initially, the methane in the ternary mixture evaporates, cooling the pond. Nitrogen, dissolved primarily in the methane, exsolves, further cooling the liquid. However, because nitrogen is significantly more soluble in cooler methane-hydrocarbon mixtures, the relative concentration of nitrogen in the solution increases as it cools. This increased nitrogen fraction increases the density of the pond, as nitrogen is significantly more dense thane methane or ethane (pure ethane’s density is intermediate to that of methane and nitrogen). At around ~85 K the mixture is as dense as pure liquid ethane. Thus, further evaporative methane loss and cooling at the pond’s surface leads to a chemical stratification, with an increasingly ethane rich epilimnion (surface layer) overlying a methane rich hypolimnion (subsurface layer). Further evaporation of methane from the ethane-rich epilimnion drives its temperature and composition toward the methane-ethane-nitrogen liquidus curve, causing pure ethane ice to precipitate out of solution and settle to the bottom of the pool. This settling would obscure the ethane ice from Cassini VIMS and ISS, which would instead continue to appear as a dark pond on the surface. As the ethane precipitates out completely, a binary methane-nitrogen liquid mixture remains. Eventually, this residual liquid evaporates away, exposing the submerged ethane ice, which Cassini VIMS and ISS would observe as a dramatic brightening of the surface, consistent with observations.

Laser beam methane detector

NASA Technical Reports Server (NTRS)

Hinkley, E. D., Jr.

1981-01-01

Instrument uses infrared absorption to determine methane concentration in liquid natural gas vapor. Two sensors measure intensity of 3.39 mm laser beam after it passes through gas; absorption is proportional to concentration of methane. Instrument is used in modeling spread of LNG clouds and as leak detector on LNG carriers and installations. Unit includes wheels for mobility and is both vertically and horizontally operable.

Methane baseline concentrations and sources in shallow aquifers from the shale gas-prone region of the St. Lawrence lowlands (Quebec, Canada).

PubMed

Moritz, Anja; Hélie, Jean-Francois; Pinti, Daniele L; Larocque, Marie; Barnetche, Diogo; Retailleau, Sophie; Lefebvre, René; Gélinas, Yves

2015-04-07

Hydraulic fracturing is becoming an important technique worldwide to recover hydrocarbons from unconventional sources such as shale gas. In Quebec (Canada), the Utica Shale has been identified as having unconventional gas production potential. However, there has been a moratorium on shale gas exploration since 2010. The work reported here was aimed at defining baseline concentrations of methane in shallow aquifers of the St. Lawrence Lowlands and its sources using δ(13)C methane signatures. Since this study was performed prior to large-scale fracturing activities, it provides background data prior to the eventual exploitation of shale gas through hydraulic fracturing. Groundwater was sampled from private (n = 81), municipal (n = 34), and observation (n = 15) wells between August 2012 and May 2013. Methane was detected in 80% of the wells with an average concentration of 3.8 ± 8.8 mg/L, and a range of <0.0006 to 45.9 mg/L. Methane concentrations were linked to groundwater chemistry and distance to the major faults in the studied area. The methane δ(1)(3)C signature of 19 samples was > -50‰, indicating a potential thermogenic source. Localized areas of high methane concentrations from predominantly biogenic sources were found throughout the study area. In several samples, mixing, migration, and oxidation processes likely affected the chemical and isotopic composition of the gases, making it difficult to pinpoint their origin. Energy companies should respect a safe distance from major natural faults in the bedrock when planning the localization of hydraulic fracturation activities to minimize the risk of contaminating the surrounding groundwater since natural faults are likely to be a preferential migration pathway for methane.

Chasing Sources and Transports of Methane Plumes in the Northern Gulf of Mexico Using In Situ Sensors on Untethered Landers

NASA Astrophysics Data System (ADS)

Martens, C. S.; Mendlovitz, H.; Seim, H.; Lapham, L.; Magen, C.; Joye, S. B.; MacDonald, I. R.; Asper, V. L.; Diercks, A. R.

2016-02-01

In situ time-series measurements of light hydrocarbons, oxygen, temperature and bottom currents from landers and elevators in the benthic boundary layer (BBL) at multiple sites in the northern Gulf of Mexico reveal spatial and temporal variability in methane concentrations controlled by horizontal advection of methane-rich plumes originating from nearby natural oil and gas seeps. Multi-sensor systems deployed for several weeks within 1m of the seafloor at depths from 882 to 1622m revealed methane concentrations ranging from near atmospheric saturation (<3 nM) to over 4000 nM depending on seep proximity, current speed and direction. Methane concentrations observed in the BBL equal or exceed maximum near-bottom values seen in shipboard water column profiles analyzed by conventional gas chromatography. Continuous laser sensor methane measurements from mini-landers deployed in September 2015 at our Horn Dome and Bush Hill sites featuring numerous gas seeps revealed methane concentrations ranging from <3 to over 300 nM over two-week periods. Net current speeds in the BBL at our six lander sites in blocks GC600, OC26 and MC118 ranged from near zero to over 5 cm/s; instantaneous speeds ranged from near zero to over 30 cm/s. Near real-time acquisition of continuous hydrocarbon concentration and current data within the BBL and friction layer from untethered platforms provides important new opportunities for monitoring the impacts of natural seeps and accidental hydrocarbon releases. The instrumented approaches we have developed to simultaneously monitor methane sources and physical processes controlling plume development and transport will enable more effective responses to further accidental hydrocarbon releases.

Abiotic production of methane in terrestrial planets.

PubMed

Guzmán-Marmolejo, Andrés; Segura, Antígona; Escobar-Briones, Elva

2013-06-01

On Earth, methane is produced mainly by life, and it has been proposed that, under certain conditions, methane detected in an exoplanetary spectrum may be considered a biosignature. Here, we estimate how much methane may be produced in hydrothermal vent systems by serpentinization, its main geological source, using the kinetic properties of the main reactions involved in methane production by serpentinization. Hydrogen production by serpentinization was calculated as a function of the available FeO in the crust, given the current spreading rates. Carbon dioxide is the limiting reactant for methane formation because it is highly depleted in aqueous form in hydrothermal vent systems. We estimated maximum CH4 surface fluxes of 6.8×10(8) and 1.3×10(9) molecules cm(-2) s(-1) for rocky planets with 1 and 5 M⊕, respectively. Using a 1-D photochemical model, we simulated atmospheres with volume mixing ratios of 0.03 and 0.1 CO2 to calculate atmospheric methane concentrations for the maximum production of this compound by serpentinization. The resulting abundances were 2.5 and 2.1 ppmv for 1 M⊕ planets and 4.1 and 3.7 ppmv for 5 M⊕ planets. Therefore, low atmospheric concentrations of methane may be produced by serpentinization. For habitable planets around Sun-like stars with N2-CO2 atmospheres, methane concentrations larger than 10 ppmv may indicate the presence of life.

Ambiguity in the causes for decadal trends in atmospheric methane and hydroxyl

PubMed Central

Turner, Alexander J.; Wennberg, Paul O.; Jacob, Daniel J.

2017-01-01

Methane is the second strongest anthropogenic greenhouse gas and its atmospheric burden has more than doubled since 1850. Methane concentrations stabilized in the early 2000s and began increasing again in 2007. Neither the stabilization nor the recent growth are well understood, as evidenced by multiple competing hypotheses in recent literature. Here we use a multispecies two-box model inversion to jointly constrain 36 y of methane sources and sinks, using ground-based measurements of methane, methyl chloroform, and the C13/C12 ratio in atmospheric methane (δ13CH4) from 1983 through 2015. We find that the problem, as currently formulated, is underdetermined and solutions obtained in previous work are strongly dependent on prior assumptions. Based on our analysis, the mathematically most likely explanation for the renewed growth in atmospheric methane, counterintuitively, involves a 25-Tg/y decrease in methane emissions from 2003 to 2016 that is offset by a 7% decrease in global mean hydroxyl (OH) concentrations, the primary sink for atmospheric methane, over the same period. However, we are still able to fit the observations if we assume that OH concentrations are time invariant (as much of the previous work has assumed) and we then find solutions that are largely consistent with other proposed hypotheses for the renewed growth of atmospheric methane since 2007. We conclude that the current surface observing system does not allow unambiguous attribution of the decadal trends in methane without robust constraints on OH variability, which currently rely purely on methyl chloroform data and its uncertain emissions estimates. PMID:28416668

Continuous, Pulsed Export of Methane-Supersaturated Meltwaters from the Bed of the Greenland Ice Sheet

NASA Astrophysics Data System (ADS)

Lamarche-Gagnon, G.; Wadham, J.; Beaton, A.; Fietzek, P.; Stanley, K. M.; Tedstone, A.; Sherwood Lollar, B.; Lacrampe Couloume, G.; Telling, J.; Liz, B.; Hawkings, J.; Kohler, T. J.; Zarsky, J. D.; Stibal, M.; Mowlem, M. C.

2016-12-01

Both past and present ice sheets have been proposed to cap large quantities of methane (CH4), on orders of magnitude significant enough to impact global greenhouse gas concentrations during periods of rapid ice retreat. However, to date most evidence for sub-ice sheet methane has been indirect, derived from calculations of the methanogenic potential of basal-ice microbial communities and biogeochemical models; field-based empirical measurements are lacking from large ice sheet catchments. Here, we present the first continuous, in situ record of dissolved methane export from a large catchment of the Greenland Ice Sheet (GrIS) in South West Greenland from May-July 2015. Our results indicate that glacial runoff was continuously supersaturated with methane over the observation period (dissolved CH4 concentrations of 30-700 nM), with total methane flux rising as subglacial discharge increased. Periodic subglacial drainage events, characterised by rapid changes (i.e. pulses) in meltwater hydrochemistry, also coincided with a rise in methane concentrations. We argue that these are likely indicative of the flushing of subglacial reservoirs of CH4 beneath the ice sheet. Total methane export was relatively modest when compared to global methane budgets, but too high to be explained by previously determined methanogenic rates from Greenland basal ice. Discrepancies between estimated Greenland methane reserves and observed fluxes stress the need to further investigate GrIS methane fluxes and sources, and suggest a more biogeochemically active subglacial environment than previously considered. Results indicate that future warming, and a coincident increase in ice melt rates, would likely make the GrIS, and by extension the Antarctic Ice Sheet, more significant sources of atmospheric methane, consequently acting as a positive feedback to a warming climate.

Continuous in-situ methane measurements at paddy fields in a rural area of India with poor electric infrastructure, using a low-cost instrument based on open-path near-IR laser absorption spectroscopy

NASA Astrophysics Data System (ADS)

Hidemori, T.; Matsumi, Y.; Nakayama, T.; Kawasaki, M.; Sasago, H.; Takahashi, K.; Imasu, R.; Takeuchi, W.; Adachi, M.; Machida, T.; Terao, Y.; Nomura, S.; Dhaka, S. K.; Singh, J.

2015-12-01

In southeast and south Asia, the previous satellite observations suggest that the methane emission from rice paddies is significant and important source of methane during rainy season. Since it is difficult to measure methane stably and continuously at rural areas such as the paddy fields in terms of infrastructures and maintenances, there are large uncertainties in quantitative estimation of methane emission in these areas and there are needs for more certification between satellite and ground based measurements. To measure methane concentrations continuously at difficult situations such as the center of paddy fields　and wetlands, we developed the continuous in-situ measurement system, not to look for your lost keys under the streetlight. The methane gas sensor is used an open-path laser based measurement instrument (LaserMethane, ANRITSU CORPORATION), which can quickly and selectively detect average methane concentrations on the optical path of the laser beam. The developed system has the power supply and telecommunication system to run the laser gas sensor in rural areas with poor electricity infrastructure.The methane measurement system was installed at paddy fields of Sonepat, Haryana on the north of Delhi in India and has been operated from the end of 2014. The air sampling along with our measurement has been carried out once a week during daytime to calibrate the laser instrument. We found that the seasonal variation of methane concentrations was different from the satellite observations and there were significant diurnal variations, which it was difficult to detect from occasional air samplings. We will present details of the measurement system and recent results of continuous methane measurements in India.

Biogeochemistry of dissolved methane and hydrogen in basement fluids of the sediment-buried Juan de Fuca Ridge flank at Boreholes (CORKs) 1301A, 1362A and 1362B: methane isotopic compositions

NASA Astrophysics Data System (ADS)

Lin, H.; Cowen, J. P.; Olson, E. J.; Lilley, M. D.; Jungbluth, S.; Rappe, M. S.

2013-12-01

The ocean crust is the largest aquifer system on Earth. Within the sediment-buried 3.5 Myr basaltic crust of the eastern Juan de Fuca Ridge (JFR) flank, the circulating basement fluids have moderate temperature (~65°C) and potentially harbor a substantial subseafloor biosphere. With dissolved oxygen and nitrate exhausted, sulfate may serve as the major electron acceptor in this environment. This study aims to evaluate the availability and the biogeochemistry of two important electron donors, methane and hydrogen, for the subseafloor biosphere. Basement fluids were collected via stainless steel and ethylene-tetrafluoroethylene fluoropolymer (ETFE) fluid delivery lines associated with Integrated Ocean Drilling Program (IODP) Circulation Obviation Retrofit Kits (CORKs) that extend from basement depths to outlet ports at the seafloor. Three CORKs were visited; 1301A, 1362A and 1362B lie within 200 to 500 m of each other, and their fluid intakes lie at ~30, ~60, and ~50 m below the sediment-basement interface (mbs), respectively. In addition, CORK 1362A contains a second intake at a deep (~200 mbs) horizon. The basement fluids from the three CORKs contained significantly higher concentrations of methane (1.5-13μM) and hydrogen (0.05-1.1 μM) than in bottom seawater (0.002 and 0.0004, respectively), indicating that prevalence and availability of both methane and hydrogen as electron donors for the subseafloor biosphere. Thermodynamic calculations show that sulfate reduction coupled with either methane or hydrogen oxidation is energy yielding in the oceanic basement. The δ13C values of methane ranged from -43×1‰ to -58×0.3‰; the δ2H values of methane in CORKs 1301A, 1362A and 1362B fluids were 57×5‰, -262×2‰, -209×2‰, respectively. The isotopic compositions suggest that methane in the basement fluid is of biogenic origin. Interestingly, the δ2H value of methane in the CORK 1301A fluids is far more positive than that in other marine environments investigated so far (Martens et al., 1999; Kessler et al., 2006; Kessler et al., 2008). The positive δ2H value of methane is best explained by partial microbial oxidation of biogenic methane, which has an initial isotopic composition similar to that from CORK 1362A and 1362B borehole fluid. High-throughput sequencing of the small subunit ribosomal RNA gene indicates the presence of methanogenic Euryarchaeota (e.g. Methanobacteria) in each of the borehole fluid samples described here. On average, fluid samples from boreholes 1362A and 1362B possessed a relatively higher abundance of known methanogens compared to borehole 1301A, consistent with higher methane concentration in 1362A and 1362B relative to 1301A fluids. Methane-oxidizing bacterial lineages from the phyla Proteobacteria and Verrucomicrobia were also detected; however, these groups were less abundant relative to the putative methane-producing groups. In conclusion, our study shows that methane and hydrogen are available electron donors and that methane is produced and potentially consumed by microorganisms in the oceanic basement. The data presented will guide incubation experiments using basement fluid in order to better understand the methane production/utilization processes within the oceanic basement.

The Application of a Jet Fan for the Control of Air and Methane Streams Mixing at the Excavations Cross - The Results of Numerical Simulation

NASA Astrophysics Data System (ADS)

Wrona, Paweł; Różański, Zenon; Pach, Grzegorz; Domagała, Lech

2016-09-01

The paper presents the results of numerical simulations into the distribution of methane concentration at the intersection of two excavations with a fan (turned on) giving the air stream to the area of the crossing. Assumed case represents emergency situation related to the unexpected flow of methane from an excavation and its mixing with fresh air. It is possible when sudden gas outburst takes place, methane leaks from methane drainage system or gas leaks out the pipelines of underground coal gasification devices. Three options were considered - corresponding to three different speeds of the jet fan. They represent three stages of fan work. First - low air speed is forced by a pneumatic fan, when electricity is cut off after high methane concentration detection. Medium speed can be forced by pneumatic-electric device when methane concentration allows to turn on the electricity. Third, the highest speed is for electric fans. Simulations were carried out in the Fire Dynamics Simulator (FDS) belongs to the group of programs Computational Fluid Dynamics (CFD). The governing equations are being solved in a numerical way. It was shown that proposed solution allows partial dilution of methane in every variant of speed what should allow escape of the miners from hazardous area.

Significance of dissolved methane in effluents of anaerobically ...

EPA Pesticide Factsheets

The need for energy efficient Domestic Wastewater (DWW) treatment is increasing annually with population growth and expanding global energy demand. Anaerobic treatment of low strength DWW produces methane which can be used to as an energy product. Temperature sensitivity, low removal efficiencies (Chemical Oxygen Demand (COD), Suspended Solids (SS), and Nutrients), alkalinity demand, and potential greenhouse gas (GHG) emissions have limited its application to warmer climates. Although well designed anaerobic Membrane Bioreactors (AnMBRs) are able to effectively treat DWW at psychrophilic temperatures (10–30 °C), lower temperatures increase methane solubility leading to increased energy losses in the form of dissolved methane in the effluent. Estimates of dissolved methane losses are typically based on concentrations calculated using Henry's Law but advection limitations can lead to supersaturation of methane between 1.34 and 6.9 times equilibrium concentrations and 11–100% of generated methane being lost in the effluent. In well mixed systems such as AnMBRs which use biogas sparging to control membrane fouling, actual concentrations approach equilibrium values. Non-porous membranes have been used to recover up to 92.6% of dissolved methane and well suited for degassing effluents of Upflow Anaerobic Sludge Blanket (UASB) reactors which have considerable solids and organic contents and can cause pore wetting and clogging in microporous membrane modules. Micro

76 FR 37838 - Petitions for Modification of Application of Existing Mandatory Safety Standards

Federal Register 2010, 2011, 2012, 2013, 2014

2011-06-28

... may include periodic tests of methane levels and limits on the minimum methane concentrations that may...) Methane monitor(s) will be calibrated on the longwall, continuous mining machine, or cutting machine and... petitioner will test for methane with a hand-held methane detector at least every 10 minutes from the time...

Quantification of the methane concentration using anaerobic oxidation of methane coupled to extracellular electron transfer

EPA Science Inventory

A biofilm anode acclimated with acetate, acetate+methane, and methane growth media for over three years produced a steady current density of 1.6-2.3 mA/m^2 in a microbial electrochemical cell (MxC) fed with methane as the sole electron donor. Geobacter was the dominant genus for...

Microbial community dynamics and methane, carbon dioxide, oxygen, and nitrous oxide concentrations in upland forest and riparian soils across a seasonal gradient of fully saturated soils to completely dried soils

NASA Astrophysics Data System (ADS)

Jones, R. T.; McGlynn, B. L.; McDermott, T.; Dore, J. E.

2015-12-01

Gas concentrations (CH4, CO2, N2O, and O2), soil properties (soil water content and pH), and microbial community composition were measured from soils at 32 sites across the Stringer Creek Watershed in the Tenderfoot Creek Experimental Forest 7 times between June 3, 2013 and September 20, 2013. Soils were fully saturated during the initial sampling period and dried down over the course of the summer. Soils and gas were sampled from 5cm and 20cm at each site and also at 50cm at eight riparian sites. In total, 496 individual soil samples were collected. Soil moisture ranged from 3.7% to fully saturated; soil pH ranged from 3.60 to 6.68. Methane concentrations in soils ranged from 0.426 ppm to 218 ppm; Carbon dioxide concentrations ranged from 550 ppm to 42,990 ppm; Nitrous oxide concentrations ranged from 0.220 ppm to 2.111 ppm; Oxygen concentrations ranged from 10.2% to 21.5%. Soil microbial communities were characterized by DNA sequences covering the V4 region of the 16S rRNA gene. DNA sequences were generated (~30,000,000 sequences) from the 496 soil samples using the Illumina MiSeq platform. Operational Taxonomic Units were generated using USEARCH, and representative sequences were taxonomically classified according the Ribosomal Database Project's taxonomy scheme. Analysis of similarity revealed that microbial communities found within a landscape type (high upland forest, low upland forest, riparian) were more similar than among landscape types (R = 0.600; p<0.001). Similarly, communities from unique site x depths were similar across the 7 collection periods (R = 0.646; p<0.001) despite changes in soil moisture. Euclidean distances of soil properties and gas concentrations were compared to Bray-Curtis community dissimilarity matrices using Mantel tests to determine how community structure co-varies with the soil environment and gas concentrations. All variables measured significantly co-varied with microbial community membership (pH: R = 0.712, p < 0.001; CO2: R = 0.578, p < 0.001; O2: R = 0.517, p < 0.001; Soil moisture: R = 0.408, p < 0.001; N2O: R = 0.218, p = 0.003; CH4: R = 0.195, p = 0.008). Despite the rather low co-variation between methane concentrations and microbial community composition, relative abundances of methanotrophic and methanogenic lineages did co-vary strongly with methane concentrations.

Methods for Finding Legacy Wells in Residential and Commercial Areas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hammack, Richard W.; Veloski, Garret A.

In 1919, the enthusiasm surrounding a short-lived gas play in Versailles Borough, Pennsylvania resulted in the drilling of many needless wells. The legacy of this activity exists today in the form of abandoned, unplugged gas wells that are a continuing source of fugitive methane in the midst of a residential and commercial area. Flammable concentrations of methane have been detected near building foundations, which have forced people from their homes and businesses until methane concentrations decreased. Despite mitigation efforts, methane problems persist and have caused some buildings to be permanently abandoned and demolished. This paper describes the use of magneticmore » and methane sensing methods by the National Energy Technology Laboratory (NETL) to locate abandoned gas wells in Versailles Borough where site access is limited and existing infrastructure can interfere. Here, wells are located between closely spaced houses and beneath buildings and parking lots. Wells are seldom visible, often because wellheads and internal casing strings have been removed, and external casing has been cut off below ground level. The magnetic survey of Versailles Borough identified 53 strong, monopole magnetic anomalies that are presumed to indicate the locations of steel-cased wells. This hypothesis was tested by excavating the location of one strong, monopole magnetic anomaly that was within an area of anomalous methane concentrations. The excavation uncovered an unplugged gas well that was within 0.2 m of the location of the maximum magnetic signal. Truck-mounted methane surveys of Versailles Borough detected numerous methane anomalies that were useful for narrowing search areas. Methane sources identified during truck-mounted surveys included strong methane sources such as sewers and methane mitigation vents. However, inconsistent wind direction and speed, especially between buildings, made locating weaker methane sources (such as leaking wells) difficult. Walking surveys with the methane detector mounted on a cart or wagon were more effective for detecting leaking wells because the instrument’s air inlet was near the ground where: 1) the methane concentration from subsurface sources (including wells) was a maximum, and 2) there was less displacement of methane anomalies from methane sources by air currents. The Versailles Borough survey found 15 methane anomalies that coincided with the location of well-type magnetic anomalies; the methane sources for these anomalies were assumed to be leaking wells. For abandoned well locations where the wellhead and all casing strings have been removed and there is no magnetic anomaly, leaking wellbores can sometimes be detected by methane surveys. Unlike magnetic anomalies, methane anomalies can be: 1) ephemeral, 2) significantly displaced from the well location, and 3) from non-well sources that cannot be discriminated without isotopic analysis. If methane surveys are used for well location, the air inlet to the instrument should be kept as close to the ground as possible to minimize the likelihood of detecting methane from distant, wind-blown sources.« less

Prospecting for Methane in Arabia Terra, Mars - First Results

NASA Technical Reports Server (NTRS)

Allen, Carlton C.; Oehler, Dotoyhy Z.; Venechuk, Elizabeth M.

2006-01-01

Methane has been measured in the Martian atmosphere at concentrations of approx. 10 ppb. Since the photochemical lifetime of this gas is approx. 300 years, it is likely that methane is currently being released from the surface. Possible sources for the methane include 1) hydrothermal activity, 2) serpentinization of basalts and other water-rock interactions, 3) thermal maturation of sedimentary organic matter, and 4) metabolism of living bacteria. Any such discovery would revolutionize our understanding of Mars. Longitudinal variations in methane concentration, as measured by the Planetary Fourier Spectrometer (PFS) on Mars Express, show the highest values over Arabia Terra, Elysium Planum, and Arcadia-Memnonia, suggesting localized areas of methane release. We are using orbital data and methodologies derived from petroleum exploration in an attempt to locate these release points.

Fluxes of dissolved methane from the seafloor at the landward limit of the gas hydrate stability zone offshore western Svalbard

NASA Astrophysics Data System (ADS)

Graves, Carolyn; Steinle, Lea; Niemann, Helge; Rehder, Gregor; Fisher, Rebecca; Lowry, Dave; Connelly, Doug; James, Rachael

2015-04-01

Seepage of methane from seafloor sediments offshore Svalbard may partly be driven by destabilization of gas hydrates as a result of bottom water warming. As the world's oceans are expected to continue to warm, in particular in the Arctic, destabilization of hydrate may become an important source of methane to ocean bottom waters and potentially to the overlying atmosphere where it contributes to further warming. In order to quantify the fate of methane from seafloor seeps, we have determined the distribution of dissolved methane in the water column on the upper slope and shelf offshore western Svalbard during three research cruises with RRS James Clark Ross (JR253) in 2011 and R/V Maria S. Merian (MSM21/4) and Heincke (HE387) in 2012. Combining discrete depth profile methane concentration data and surface seawater concentrations from an equilibrator-online system with oxidation rate measurements and atmospheric methane observations allows insight into the fate of methane input from the seafloor, and evaluation of the potential contributions of other methane sources. A simple box model considering oxidation and horizontal and vertical mixing indicates that the majority of seep methane is oxidized at depth. A plume of high methane concentrations is expected to persist more than 100 km downstream of the seepage area in the rapid barotropic West Spitsbergen Current, which flows northward towards the Arctic Ocean. We calculate that the diffusive sea-air flux of methane is largest on the shallow shelf, reaching 36 μmol m-2 day-1. Over the entire western Svalbard region there is a persistent, but small, source of methane from surface seawater to the overlying atmosphere. Measurements of the atmospheric methane carbon isotope signature indicate that the seafloor seeps do not make a significant contribution to atmospheric methane in this region, which is consistent with earlier studies. Observations downstream of the seepage region are necessary to further constrain potential for transport of previously hydrate-bound methane to the atmosphere, which would require a mechanism for enhanced vertical mixing of dissolved methane from bottom waters into the surface mixed layer.

Determination of dissolved methane in natural waters using headspace analysis with cavity ring-down spectroscopy.

PubMed

Roberts, Hannah M; Shiller, Alan M

2015-01-26

Methane (CH4) is the third most abundant greenhouse gas (GHG) but is vastly understudied in comparison to carbon dioxide. Sources and sinks to the atmosphere vary considerably in estimation, including sources such as fresh and marine water systems. A new method to determine dissolved methane concentrations in discrete water samples has been evaluated. By analyzing an equilibrated headspace using laser cavity ring-down spectroscopy (CRDS), low nanomolar dissolved methane concentrations can be determined with high reproducibility (i.e., 0.13 nM detection limit and typical 4% RSD). While CRDS instruments cost roughly twice that of gas chromatographs (GC) usually used for methane determination, the process presented herein is substantially simpler, faster, and requires fewer materials than GC methods. Typically, 70-mL water samples are equilibrated with an equivalent amount of zero air in plastic syringes. The equilibrated headspace is transferred to a clean, dry syringe and then drawn into a Picarro G2301 CRDS analyzer via the instrument's pump. We demonstrate that this instrument holds a linear calibration into the sub-ppmv methane concentration range and holds a stable calibration for at least two years. Application of the method to shipboard dissolved methane determination in the northern Gulf of Mexico as well as river water is shown. Concentrations spanning nearly six orders of magnitude have been determined with this method. Copyright © 2014 Elsevier B.V. All rights reserved.

Processes and Parameters Controlling the Extent of Methanogenic Conditions in the Unsaturated Zone of a Crude Oil Spill Site

NASA Astrophysics Data System (ADS)

Molins, S.; Mayer, K.

2007-12-01

Gas concentrations measured in the vadose zone at a crude oil spill site near Bemidji, MN, show that a large area near the oil body is currently dominated by methanogenic conditions. Away from the oil body methane concentrations decrease as it is degraded by methanotrophic bacteria under aerobic conditions. Numerical simulations have been conducted to quantify the contributions of the relevant transport and reaction processes to the production and attenuation of methane in the vadose zone. Methane is generated in the vadose zone by anaerobic degradation of oil and is also added by fluxes from the capillary fringe and the saturated zone. Gas diffusion and advection contribute to the transport of methane in the lateral direction and towards the ground surface. Attenuation of methane concentrations occurs through aerobic oxidation in the presence of methanotrophic bacteria. Critical parameters were varied within bounds provided by field data and previous studies. Simulation results confirm that the layered sediment structure present at the site plays a significant role in explaining the observed distribution of gases in the vadose zone. The presence of a low permeability lens in the area upgradient from the source results in higher moisture contents, limiting diffusion of oxygen into the zone of methane production, and contributes to the spread of methane. Diffusion was identified as the most significant transport mechanism for gases in the vadose zone. However, field-observed zones of depleted and enriched N2 and Ar concentrations could only be explained by the development of advective fluxes induced by reactive processes (methanogenesis and methanotrophy). The zones of gas production are characterized by slightly increased total gas pressures and low concentrations of N2 and Ar, while zones of gas consumption show slightly depressed total gas pressures and high concentrations of N2 and Ar. The simulations suggest that the advective flux that develops between these zones contributes up to 15% of the total methane flux.

Assessing How Water Type, Climate, and Landscape Position Correlate with Variability of Methane in Shallow Groundwater in the Marcellus Region

NASA Astrophysics Data System (ADS)

Campbell, A.; Lautz, L.; Hoke, G. D.

2017-12-01

Prior work shows that spatial differences in naturally-occurring methane concentrations in shallow groundwater in the Marcellus Shale region are correlated with water type (e.g. Ca-HCO3 vs Na-HCO3) and landscape position (e.g. valley vs upland). However, little is known about how naturally-occurring methane in groundwater varies through time, particularly on a seasonal or monthly time scale, and how temporal variability is related to seasonal changes in climate. Extensive development of the Marcellus shale gas play in northeastern Pennsylvania limits opportunities for measuring baseline water quality through time. In contrast, a ban on hydraulic fracturing in NY affords an opportunity for characterizing baseline temporal variability in methane concentrations. The objective of this study is to characterize temporal variability of naturally-occurring methane in shallow groundwater in the Marcellus region, and how such temporal variability is correlated to other well characteristics, such as water type, landscape position, and climatic conditions. We worked with homeowners to sample 11 domestic wells monthly in the Marcellus Shale region of NY for methane concentrations and major ions for a full year. Wells were grouped according to the primary source of methane (e.g. thermogenic vs microbial) based upon δ13C-DIC, δ13C-CH4, and δD-CH4 isotopes. The full dataset and the grouped data were analyzed to assess how well climatic conditions, water type, and landscape position correlate with variability of methane concentrations through time. These data provide information on within year and between year variability of methane, as well as spatial variability between wells, which fills a data gap and can be used to inform policy regulations.

Stable isotope tracing of anaerobic methane oxidation in the gassy sediments of Eckernfoerde Bay, German Baltic Sea

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martens, C.S.; Albert, D.B.; Alperin, M.J.

Methane concentrations in the pore waters of Eckernfoerde Bay in the German Baltic Sea generally reach gas bubble saturation values within the upper meter of the sediment column. The depth at which saturation occurs is controlled by a balance between rates of methane production, consumption (oxidation), and transport. The relative importance of anaerobic methane oxidation (AMO) in controlling dissolved and gas bubble methane distributions in the bay's sediments is indirectly revealed through methane concentration versus depth profiles, depth variations in the stable C and H isotope composition of methane, and the C isotope composition of total dissolved inorganic carbon ({Sigma}CO{submore » 2}). Direct radiotracer measurements indicate that AMO rates of over 15 mM/yr are focused at the base of the sulfate reduction zone. Diagenetic equations that describe the depth destructions of the {delta}{sup 13}C and {delta}D values of methane reproduce isotopic shifts observed throughout the methane oxidation zone and are best fit with kinetic isotope fractionation factors of 1.012 {+-} 0.001 and 1.120 {plus{underscore}minus} 0.020 respectively.« less

Reactive transport model of growth and methane production by high-temperature methanogens in hydrothermal regions of the subseafloor

NASA Astrophysics Data System (ADS)

Stewart, L. C.; Algar, C. K.; Topçuoğlu, B. D.; Fortunato, C. S.; Larson, B. I.; Proskurowski, G. K.; Butterfield, D. A.; Vallino, J. J.; Huber, J. A.; Holden, J. F.

2014-12-01

Hydrogenotrophic methanogens are keystone high-temperature autotrophs in deep-sea hydrothermal vents and tracers of habitability and biogeochemical activity in the hydrothermally active subseafloor. At Axial Seamount, nearly all thermophilic methanogens are Methanothermococcus and Methanocaldococcus species, making this site amenable to modeling through pure culture laboratory experiments coupled with field studies. Based on field microcosm incubations with 1.2 mM, 20 μM, or no hydrogen, the growth of methanogens at 55°C and 80°C is limited primarily by temperature and hydrogen availability, with ammonium amendment showing no consistent effect on total methane output. The Arrhenius constants for methane production by Methanocaldococcus jannaschii (optimum 82°C) and Methanothermococcus thermolithotrophicus (optimum 65°C) were determined in pure culture bottle experiments. The Monod constants for hydrogen concentration were measured by growing both organisms in a 2-liter chemostat at two dilution rates; 55°C, 65°C and 82°C; and variable hydrogen concentrations. M. jannaschii showed higher ks and Vmax constants than M. thermolithotrophicus. In the field, hydrogen and methane concentrations in hydrothermal end-member and low-temperature diffuse fluids were measured, and the concentrations of methanogens that grow at 55°C and 80°C in diffuse fluids were determined using most-probable-number estimates. Methane concentration anomalies in diffuse fluids relative to end-member hydrothermal concentrations and methanogen cell concentrations are being used to constrain a 1-D reactive transport model using the laboratory-determined Arrhenius and Monod constants for methane production by these organisms. By varying flow path length and subseafloor cell concentrations in the model, our goal is to determine solutions for the potential depth of the subseafloor biosphere coupled with the amount of methanogenic biomass it contains.

Environmental baselines: preparing for shale gas in the UK

NASA Astrophysics Data System (ADS)

Bloomfield, John; Manamsa, Katya; Bell, Rachel; Darling, George; Dochartaigh, Brighid O.; Stuart, Marianne; Ward, Rob

2014-05-01

Groundwater is a vital source of freshwater in the UK. It provides almost 30% of public water supply on average, but locally, for example in south-east England, it is constitutes nearly 90% of public supply. In addition to public supply, groundwater has a number of other uses including agriculture, industry, and food and drink production. It is also vital for maintaining river flows especially during dry periods and so is essential for maintaining ecosystem health. Recently, there have been concerns expressed about the potential impacts of shale gas development on groundwater. The UK has abundant shales and clays which are currently the focus of considerable interest and there is active research into their characterisation, resource evaluation and exploitation risks. The British Geological Survey (BGS) is undertaking research to provide information to address some of the environmental concerns related to the potential impacts of shale gas development on groundwater resources and quality. The aim of much of this initial work is to establish environmental baselines, such as a baseline survey of methane occurrence in groundwater (National methane baseline study) and the spatial relationships between potential sources and groundwater receptors (iHydrogeology project), prior to any shale gas exploration and development. The poster describes these two baseline studies and presents preliminary findings. BGS are currently undertaking a national survey of baseline methane concentrations in groundwater across the UK. This work will enable any potential future changes in methane in groundwater associated with shale gas development to be assessed. Measurements of methane in potable water from the Cretaceous, Jurassic and Triassic carbonate and sandstone aquifers are variable and reveal methane concentrations of up to 500 micrograms per litre, but the mean value is relatively low at < 10 micrograms per litre. These values compare with much higher levels of methane in aquicludes and thermal waters, for example from the Carboniferous and Triassic which have concentrations in excess of 1500 micrograms per litre. It is important to understand the spatial relationships between potential shale gas source rocks and overlying aquifers if shale gas is to be developed in a safe and sustainable manner. The BGS and the Environment Agency have undertaken a national-scale study of the UK to assess the vertical separation between potential shale gas source rocks and major aquifers (iHydrogeology project). Aquifer - shale separations have been documented in the range <200m to >2km. The geological modelling process will be presented and discussed along with maps combining the results of the methane baseline study, the distribution of Principal Aquifers and shale/clay units, and aquifer - shale separation maps for the UK.

Consumption of atmospheric methane by tundra soils

NASA Technical Reports Server (NTRS)

Whalen, S. C.; Reeburgh, W. S.

1990-01-01

The results of field and laboratory experiments on methane consumption by tundra soils are reported. For methane concentrations ranging from below to well above ambient, moist soils are found to consume methane rapidly; in nonwaterlogged soils, equilibration with atmospheric methane is fast relative to microbial oxidation. It is concluded that lowering of the water table in tundra as a resulting from a warmer, drier climate will decrease methane fluxes and could cause these areas to provide negative feedback for atmospheric methane.

Seasonal and Latitudinal Variations in Dissolved Methane from 42 Lakes along a North-South Transect in Alaska

NASA Astrophysics Data System (ADS)

Sepulveda-Jauregui, A.; Walter Anthony, K. M.; Martinez-Cruz, K. C.; Anthony, P.; Thalasso, F.

2013-12-01

Armando Sepulveda-Jauregui,* Katey M. Walter Anthony,* Karla Martinez-Cruz,* ** Peter Anthony,* and Frederic Thalasso**. * Water and Environmental Research Center, Institute of Northern Engineering, University of Alaska Fairbanks, Fairbanks, Alaska. ** Biotechnology and Bioengineering Department, Cinvestav, Mexico city, D. F., Mexico. Northern lakes are important reservoirs and sources to the atmosphere of methane (CH4), a potent greenhouse gas. It is estimated that northern lakes (> 55 °N) contribute about 20% of the total global lake methane emissions, and that emissions from these lakes will increase with climate warming. Temperature rise enhances methane production directly by providing the kinetic energy to methanogenesis, and indirectly by supplying organic matter from thawing permafrost. Warmer lakes also store less methane since methane's solubility is inversely related to temperature. Alaskan lakes are located in three well-differentiated permafrost classes: yedoma permafrost with high labile carbon stocks, non-yedoma permafrost with lower carbon stocks, and areas without permafrost, also with generally lower carbon stocks. We sampled dissolved methane from 42 Alaskan lakes located in these permafrost cover classes along a north-south Alaska transect from Prudhoe Bay to the Kenai Peninsula during open-water conditions in summer 2011. We sampled 26 of these lakes in April, toward the end of the winter ice-covered period. Our results indicated that the largest dissolved methane concentrations occurred in interior Alaska thermokarst lakes formed in yedoma-type permafrost during winter and summer, with maximal concentrations of 17.19 and 12.76 mg L-1 respectively. In these lakes, emission of dissolved gases as diffusion during summer and storage release in spring were 18.4% and 17.4% of the annual emission budget, while ebullition (64.2 %) comprised the rest. Dissolved oxygen was inversely correlated with dissolved methane concentrations in both seasons; the absence of O2 enhances methane production, while high concentration of O2 could favor methane oxidation. These relationships suggest that permafrost type, and specifically the availability of permafrost organic matter, influences methane cycling in Alaskan lakes.

Methane Production and Transport within the Marsh Biome of Biosphere 2

NASA Technical Reports Server (NTRS)

Molnar, Jennifer; Goodridge, Kelven

1997-01-01

In recent decades, the concentration of methane in the earth's atmosphere increased 1-2% annually. It's rate of increases, combined with methane's effectiveness as a greenhouse gas, has led to an intensive research effort to determine the sources and sinks of the gas in the environment. Biosphere 2 offers a unique opportunity to contribute to the effort because it lacks a major photochemical sink present in the Earth's atmosphere. Researchers can therefore concentrate on biological processes involved in methane cycles. Wetlands are a large source of atmospheric methane, due to anoxic conditions in the sediments and the abundance of organic materials. In order to determine if these conditions in Biosphere 2 also promote methane production, this study looked for the fluxes of methane and methods of transport of the gas from from the water and sediments to the atmosphere in the Marsh Biome. Fluxes of methane from the sediments and waters were measured using static chambers, peepers, and leaf bags. Fluxes and vertical profiles of methane in the sediments show that substantial amounts of methane are being produced in the marsh and are being transported into the Biosphere 2 environment.

A possible reason behind the initial formation of pentagonal dodecahedron cavities in sI-methane hydrate nucleation: A DFT study

NASA Astrophysics Data System (ADS)

Mondal, Sukanta; Goswami, Tamal; Jana, Gourhari; Misra, Anirban; Chattaraj, Pratim Kumar

2018-01-01

In this letter, a possible reason behind selective host-guest organization in the initial stage of sI methane hydrate nucleation is provided, through density functional theory based calculations. In doing so, we have connected earlier experimental and theoretical observations on the structure and energetics of sI methane hydrate to our findings. Geometry and relative stability of small (H2O)5 and (H2O)6 clusters, presence of CH4 guest, integrity and cavity radius of (H2O)20 and (H2O)24, as well as the weak van der Waals type of forces, particularly dispersion interaction, are major factors responsible for initial formation of methane encapsulated dodecahedron cavity over tetrakaidecahedron.

Comparison of Methane Control Methods in Polish and Vietnamese Coal Mines

NASA Astrophysics Data System (ADS)

Borowski, Marek; Kuczera, Zbigniew

2018-03-01

Methane hazard often occurs in hard coal mines and causes very serious accidents and can be the reason of methane or methane and coal dust explosions. History of coal mining shows that methane released from the rock mass to the longwall area was responsible for numerous mining disasters. The main source of methane are coal deposits because it is autochthonous gas and is closely related with carbonification and forming of coal deposits. Degree of methane saturation in coal deposits depends on numerous factors; mainly on presence or lack of insulating layers in cover deposit that allow or do not on degasification and easily methane outflow into surroundings. Hence in coal mining there are coal deposits that contain only low degree of methane saturation in places where is lack of insulating layers till high in methane coal deposits occurring in insulating claystones or in shales. Conducting mining works in coal deposits of high methane hazard without using of special measures to combat (ventilation, methane drainage) could be impossible. Control of methane hazard depends also on other co-occuring natural dangers for which used preventive actions eliminate methane hazard. Safety in mines excavating coal deposits saturated with methane depends on the correct estimation of methane hazard, drawn up forecasts, conducted observations, hazard control as well as undertaken prevention measures. Methane risk prevention includes identification and control methods of methane hazards as well as means of combating the explosive accumulation of methane in longwall workings. The main preventive actions in underground coal mines are: effective ventilation that prevents forming of methane fuses or placed methane accumulation in headings ventilated by airflow created by main fans and in headings with auxiliary ventilation, methane drainage using drain holes that are drilled from underground headings or from the surface, methanometry control of methane concentration in the air; location of the sensors is defined by law, additional ventilation equipment used in places of lower intensity of ventilation and places where methane is concentrated.

Methane and nitrous oxide in the ice core record.

PubMed

Wolff, Eric; Spahni, Renato

2007-07-15

Polar ice cores contain, in trapped air bubbles, an archive of the concentrations of stable atmospheric gases. Of the major non-CO2 greenhouse gases, methane is measured quite routinely, while nitrous oxide is more challenging, with some artefacts occurring in the ice and so far limited interpretation. In the recent past, the ice cores provide the only direct measure of the changes that have occurred during the industrial period; they show that the current concentration of methane in the atmosphere is far outside the range experienced in the last 650,000 years; nitrous oxide is also elevated above its natural levels. There is controversy about whether changes in the pre-industrial Holocene are natural or anthropogenic in origin. Changes in wetland emissions are generally cited as the main cause of the large glacial-interglacial change in methane. However, changing sinks must also be considered, and the impact of possible newly described sources evaluated. Recent isotopic data appear to finally rule out any major impact of clathrate releases on methane at these time-scales. Any explanation must take into account that, at the rapid Dansgaard-Oeschger warmings of the last glacial period, methane rose by around half its glacial-interglacial range in only a few decades. The recent EPICA Dome C (Antarctica) record shows that methane tracked climate over the last 650,000 years, with lower methane concentrations in glacials than interglacials, and lower concentrations in cooler interglacials than in warmer ones. Nitrous oxide also shows Dansgaard-Oeschger and glacial-interglacial periodicity, but the pattern is less clear.

Advanced Fire Detector for Space Applications

NASA Technical Reports Server (NTRS)

Kutzner, Joerg

2012-01-01

A document discusses an optical carbon monoxide sensor for early fire detection. During the sensor development, a concept was implemented to allow reliable carbon monoxide detection in the presence of interfering absorption signals. Methane interference is present in the operating wavelength range of the developed prototype sensor for carbon monoxide detection. The operating parameters of the prototype sensor have been optimized so that interference with methane is minimized. In addition, simultaneous measurement of methane is implemented, and the instrument automatically corrects the carbon monoxide signal at high methane concentrations. This is possible because VCSELs (vertical cavity surface emitting lasers) with extended current tuning capabilities are implemented in the optical device. The tuning capabilities of these new laser sources are sufficient to cover the wavelength range of several absorption lines. The delivered carbon monoxide sensor (COMA 1) reliably measures low carbon monoxide levels even in the presence of high methane signals. The signal bleed-over is determined during system calibration and is then accounted for in the system parameters. The sensor reports carbon monoxide concentrations reliably for (interfering) methane concentrations up to several thousand parts per million.

Coupling p+n Field-Effect Transistor Circuits for Low Concentration Methane Gas Detection

PubMed Central

Zhou, Xinyuan; Yang, Liping; Bian, Yuzhi; Ma, Xiang; Chen, Yunfa

2018-01-01

Nowadays, the detection of low concentration combustible methane gas has attracted great concern. In this paper, a coupling p+n field effect transistor (FET) amplification circuit is designed to detect methane gas. By optimizing the load resistance (RL), the response to methane of the commercial MP-4 sensor can be magnified ~15 times using this coupling circuit. At the same time, it decreases the limit of detection (LOD) from several hundred ppm to ~10 ppm methane, with the apparent response of 7.0 ± 0.2 and voltage signal of 1.1 ± 0.1 V. This is promising for the detection of trace concentrations of methane gas to avoid an accidental explosion because its lower explosion limit (LEL) is ~5%. The mechanism of this coupling circuit is that the n-type FET firstly generates an output voltage (VOUT) amplification process caused by the gate voltage-induced resistance change of the FET. Then, the p-type FET continues to amplify the signal based on the previous VOUT amplification process. PMID:29509659

Coupling p+n Field-Effect Transistor Circuits for Low Concentration Methane Gas Detection.

PubMed

Zhou, Xinyuan; Yang, Liping; Bian, Yuzhi; Ma, Xiang; Han, Ning; Chen, Yunfa

2018-03-06

Nowadays, the detection of low concentration combustible methane gas has attracted great concern. In this paper, a coupling p+n field effect transistor (FET) amplification circuit is designed to detect methane gas. By optimizing the load resistance ( R L ), the response to methane of the commercial MP-4 sensor can be magnified ~15 times using this coupling circuit. At the same time, it decreases the limit of detection (LOD) from several hundred ppm to ~10 ppm methane, with the apparent response of 7.0 ± 0.2 and voltage signal of 1.1 ± 0.1 V. This is promising for the detection of trace concentrations of methane gas to avoid an accidental explosion because its lower explosion limit (LEL) is ~5%. The mechanism of this coupling circuit is that the n-type FET firstly generates an output voltage ( V OUT ) amplification process caused by the gate voltage-induced resistance change of the FET. Then, the p-type FET continues to amplify the signal based on the previous V OUT amplification process.

30 CFR 27.24 - Power-shutoff component.

Code of Federal Regulations, 2010 CFR

2010-07-01

... APPROVAL OF MINING PRODUCTS METHANE-MONITORING SYSTEMS Construction and Design Requirements § 27.24 Power... the machine or equipment when actuated by the methane detector at a methane concentration of 2.0... actuated by the methane detector, cause a control circuit to shut down the machine or equipment on which it...

30 CFR 27.24 - Power-shutoff component.

Code of Federal Regulations, 2013 CFR

2013-07-01

... the machine or equipment when actuated by the methane detector at a methane concentration of 2.0... actuated by the methane detector, cause a control circuit to shut down the machine or equipment on which it...-shutoff component shall, when actuated by the methane detector, cause a control circuit to deenergize the...

30 CFR 27.24 - Power-shutoff component.

Code of Federal Regulations, 2011 CFR

2011-07-01

... the machine or equipment when actuated by the methane detector at a methane concentration of 2.0... actuated by the methane detector, cause a control circuit to shut down the machine or equipment on which it...-shutoff component shall, when actuated by the methane detector, cause a control circuit to deenergize the...

30 CFR 27.24 - Power-shutoff component.

Code of Federal Regulations, 2012 CFR

2012-07-01

... the machine or equipment when actuated by the methane detector at a methane concentration of 2.0... actuated by the methane detector, cause a control circuit to shut down the machine or equipment on which it...-shutoff component shall, when actuated by the methane detector, cause a control circuit to deenergize the...

30 CFR 27.24 - Power-shutoff component.

Code of Federal Regulations, 2014 CFR

2014-07-01

... the machine or equipment when actuated by the methane detector at a methane concentration of 2.0... actuated by the methane detector, cause a control circuit to shut down the machine or equipment on which it...-shutoff component shall, when actuated by the methane detector, cause a control circuit to deenergize the...

High-pressure anaerobic digestion up to 100 bar: influence of initial pressure on production kinetics and specific methane yields.

PubMed

Merkle, Wolfgang; Baer, Katharina; Haag, Nicola Leonard; Zielonka, Simon; Ortloff, Felix; Graf, Frank; Lemmer, Andreas

2017-02-01

To ensure an efficient use of biogas produced by anaerobic digestion, in some cases it would be advisable to upgrade the biogenic gases and inject them into the transnational gas grids. To investigate biogas production under high-pressure conditions up to 100 bar, new pressure batch methane reactors were developed for preliminary lab-scale experiments with a mixture of grass and maize silage hydrolysate. During this investigation, the effects of different initial pressures (1, 50 and 100 bar) on pressure increase, gas production and the specific methane yield using nitrogen as inert gas were determined. Based on the experimental findings increasing initial pressures alter neither significantly, further pressure increases nor pressure increase rates. All supplied organic acids were degraded and no measurable inhibition of the microorganisms was observed. The results show that methane reactors can be operated at operating pressures up to 100 bar without any negative effects on methane production.

Tank-connected food waste disposer systems--current status and potential improvements.

PubMed

Bernstad, A; Davidsson, A; Tsai, J; Persson, E; Bissmont, M; la Cour Jansen, J

2013-01-01

An unconventional system for separate collection of food waste was investigated through evaluation of three full-scale systems in the city of Malmö, Sweden. Ground food waste is led to a separate settling tank where food waste sludge is collected regularly with a tank-vehicle. These tank-connected systems can be seen as a promising method for separate collection of food waste from both households and restaurants. Ground food waste collected from these systems is rich in fat and has a high methane potential when compared to food waste collected in conventional bag systems. The content of heavy metals is low. The concentrations of N-tot and P-tot in sludge collected from sedimentation tanks were on average 46.2 and 3.9 g/kg TS, equalling an estimated 0.48 and 0.05 kg N-tot and P-tot respectively per year and household connected to the food waste disposer system. Detergents in low concentrations can result in increased degradation rates and biogas production, while higher concentrations can result in temporary inhibition of methane production. Concentrations of COD and fat in effluent from full-scale tanks reached an average of 1068 mg/l and 149 mg/l respectively over the five month long evaluation period. Hydrolysis of the ground material is initiated between sludge collection occasions (30 days). Older food waste sludge increases the degradation rate and the risks of fugitive emissions of methane from tanks between collection occasions. Increased particle size decreases hydrolysis rate and could thus decrease losses of carbon and nutrients in the sewerage system, but further studies in full-scale systems are needed to confirm this. Copyright © 2012 Elsevier Ltd. All rights reserved.

Hydrocarbon Plume Dynamics in the Worldś Most Spectacular Hydrocarbon Seeps, Santa Barbara Channel, California

NASA Astrophysics Data System (ADS)

Mau, S.; Reed, J.; Clark, J.; Valentine, D.

2006-12-01

Large quantities of natural gas are emitted from the seafloor into the coastal ocean near Coal Oil Point, Santa Barbara Channel (SBC), California. Methane, ethane, and propane were quantified in the surface water at 79 stations in a 270 km2 area in order to map the surficial hydrocarbon plume and to quantify air-sea exchange of these gases. A time series was initiated for 14 stations to identify the variability of the mapped plume, and biologically-mediated oxidation rates of methane were measured to quantify the loss of methane in surface water. The hydrocarbon plume was found to comprise ~70 km2 and extended beyond study area. The plume width narrowed from 3 km near the source to 0.7 km further from the source, and then expanded to 6.7 km at the edge of the study area. This pattern matches the cyclonic gyre which is the normal current flow in this part of the Santa Barbara Channel - pushing water to the shore near the seep field and then broadening the plume while the water turns offshore further from the source. Concentrations of gaseous hydrocarbons decrease as the plume migrates. Time series sampling shows similar plume width and hydrocarbon concentrations when normal current conditions prevail. In contrast, smaller plume width and low hydrocarbon concentrations were observed when an additional anticyclonic eddy reversed the normal current flow, and a much broader plume with higher hydrocarbon concentrations was observed during a time of diminished speed within the current gyre. These results demonstrate that surface currents control hydrocarbon plume dynamics in the SBC, though hydrocarbon flux to the atmosphere is likely less dependent on currents. Estimates of air- sea hydrocarbon flux and biological oxidation rates will also be presented.

Development of a Field-Deployable Methane Carbon Isotope Analyzer

NASA Astrophysics Data System (ADS)

Dong, Feng; Baer, Douglas

2010-05-01

Methane is a potent greenhouse gas, whose atmospheric surface mixing ratio has almost doubled compared with preindustrial values. Methane can be produced by biogenic processes, thermogenic processes or biomass, with different isotopic signatures. As a key molecule involved in the radiative forcing in the atmosphere, methane is thus one of the most important molecules linking the biosphere and atmosphere. Therefore precise measurements of mixing ratios and isotopic compositions will help scientists to better understand methane sources and sinks. To date, high precision isotope measurements have been exclusively performed with conventional isotope ratio mass spectrometry, which involves intensive labor and is not readily field deployable. Optical studies using infrared laser spectroscopy have also been reported to measure the isotopic ratios. However, the precision of optical-based analyses, to date, is typically unsatisfactory without pre-concentration procedures. We present characterization of the performance of a portable Methane Carbon Isotope Analyzer (MCIA), based on cavity enhanced laser absorption spectroscopy technique, that provides in-situ measurements of the carbon isotope ratio (13C/12C or del_13C) and methane mixing ratio (CH4). The sample is introduced to the analyzer directly without any requirement for pretreatment or preconcentration. A typical precision of less than 1 per mill (< 0.1%) with a 10-ppm methane sample can be achieved in a measurement time of less than 100 seconds. The MCIA can report carbon isotope ratio and concentration measurements over a very wide range of methane concentrations. Results of laboratory tests and field measurements will be presented.

Abiotic Production of Methane in Terrestrial Planets

PubMed Central

Guzmán-Marmolejo, Andrés; Escobar-Briones, Elva

2013-01-01

Abstract On Earth, methane is produced mainly by life, and it has been proposed that, under certain conditions, methane detected in an exoplanetary spectrum may be considered a biosignature. Here, we estimate how much methane may be produced in hydrothermal vent systems by serpentinization, its main geological source, using the kinetic properties of the main reactions involved in methane production by serpentinization. Hydrogen production by serpentinization was calculated as a function of the available FeO in the crust, given the current spreading rates. Carbon dioxide is the limiting reactant for methane formation because it is highly depleted in aqueous form in hydrothermal vent systems. We estimated maximum CH4 surface fluxes of 6.8×108 and 1.3×109 molecules cm−2 s−1 for rocky planets with 1 and 5 M⊕, respectively. Using a 1-D photochemical model, we simulated atmospheres with volume mixing ratios of 0.03 and 0.1 CO2 to calculate atmospheric methane concentrations for the maximum production of this compound by serpentinization. The resulting abundances were 2.5 and 2.1 ppmv for 1 M⊕ planets and 4.1 and 3.7 ppmv for 5 M⊕ planets. Therefore, low atmospheric concentrations of methane may be produced by serpentinization. For habitable planets around Sun-like stars with N2-CO2 atmospheres, methane concentrations larger than 10 ppmv may indicate the presence of life. Key Words: Serpentinization—Exoplanets—Biosignatures—Planetary atmospheres. Astrobiology 13, 550–559. PMID:23742231

Dissolved methane in groundwater, Upper Delaware River Basin, Pennsylvania and New York, 2007-12

USGS Publications Warehouse

Kappel, William M.

2013-01-01

The prospect of natural gas development from the Marcellus and Utica Shales has raised concerns about freshwater aquifers being vulnerable to contamination. Well owners are asking questions about subsurface methane, such as, “Does my well water have methane and is it safe to drink the water?” and “Is my well system at risk of an explosion hazard associated with a combustible gas like methane in groundwater?” This newfound awareness of methane contamination of water wells by stray gas migration is based upon studies such as Molofsky and others (2011) who document the widespread natural occurrence of methane in drinking-water wells in Susquehanna County, Pennsylvania. In the same county, Osborn and others (2011) identified elevated methane concentrations in selected drinking-water wells in the vicinity of Marcellus Shale gas-development activities, although pre-development groundwater samples were not available for comparison. A compilation of dissolved methane concentrations in groundwater for New York State was published by Kappel and Nystrom (2012). Recent work documenting the occurrence and distribution of methane in groundwater was completed in southern Sullivan County, Pennsylvania (Sloto, 2013). Additional work is ongoing with respect to monitoring for stray gases in groundwater (Jackson and others, 2013). These studies and their results indicate the importance of collecting baseline or pre-development data. While such data are being collected in some areas, published data on methane in groundwater are sparse in the Upper Delaware River Basin of Pennsylvania, New York, and New Jersey. To manage drinking-water resources in areas of gas-well drilling and hydraulic fracturing in the Upper Delaware River Basin, the natural occurrence of methane in the tri-state aquifers needs to be documented. The purpose of this report is to present data on dissolved methane concentrations in the groundwater in the Upper Delaware River Basin. The scope is restricted to data for Pennsylvania and New York, no U.S. Geological Survey (USGS) methane analyses are presently available for northwestern New Jersey.

Inhibition effects of high calcium concentration on anaerobic biological treatment of MSW leachate.

PubMed

Xia, Yi; He, Pin-Jing; Pu, Hong-Xia; Lü, Fan; Shao, Li-Ming; Zhang, Hua

2016-04-01

With the increasing use of municipal solid waste incineration (MSWI) and more stringent limits on landfilling of organic waste, more MSWI bottom ash is being landfilled, and the proportion of inorganic wastes in landfills is increasing, causing the increased Ca concentrations in landfill leachate. In this research, the inhibition effect of Ca concentration on the anaerobic treatment of landfill leachate was studied using a biochemical methane potential experiment. Slight inhibition of methane production occurred when the addition of Ca concentration was less than 2000 mg/L. When the addition of Ca concentration was between 6000 and 8000 mg/L, methane production was significantly reduced (to 29.4-34.8 % of that produced by the BLK reactor), and the lag phase was increased from 8.55 to 16.32 d. Moreover, when the dosage of Ca concentration increased from zero to 8000 mg/L, reductions in solution Ca concentration increased from 929 to 2611 mg/L, and the proportion of Ca in the residual sludge increased from 22.58 to 46.87 %. Based on the results, when the dosage of Ca concentration was less than 4000 mg/L, the formation of Ca precipitates on the surface of sludge appeared to prevent mass transfer and was the dominant reason for the reduction in methane production and sludge biomass. At higher Ca concentrations (6000-8000 mg/L), the severe inhibition of methane production appeared to be caused by the toxic effect of highly concentrated Ca on sludge as well as mass transfer blockage.

METHOD FOR PRODUCING ISOTOPIC METHANES AND PARTIALLY HALOGENATED DERIVATIVES THEROF

DOEpatents

Frazer, J.W.

1959-08-18

A method is given for producing isotopic methanes and/ or partially halogenated derivatives. Lithium hydride, deuteride, or tritide is reacted with a halogenated methane or with a halogenated methane in combination with free halogen. The process is conveniently carried out by passing a halogenated methane preferably at low pressures or in an admixture with an inert gas through a fixed bed of finely divided lithium hydride heated initially to temperatures of 100 to 200 deg C depending upon the halogenated methane used.

A non-steady-state condition in sediments at the gas hydrate stability boundary off West Spitsbergen: Evidence for gas hydrate dissociation or just dynamic methane transport

NASA Astrophysics Data System (ADS)

Treude, Tina; Krause, Stefan; Bertics, Victoria; Steinle, Lea; Niemann, Helge; Liebetrau, Volker; Feseker, Tomas; Burwicz, Ewa; Krastel, Sebastian; Berndt, Christian

2015-04-01

In 2008, a large area with several hundred methane plumes was discovered along the West Spitsbergen continental margin at water depths between 150 and 400 m (Westbrook et al. 2009). Many of the observed plumes were located at the boundary of gas hydrate stability (~400 m water depth). It was speculated that the methane escape at this depth was correlated with gas hydrate destabilization caused by recent increases in water temperatures recorded in this region. In a later study, geochemical analyses of authigenic carbonates and modeling of heat flow data combined with seasonal changes in water temperature demonstrated that the methane seeps were active already prior to industrial warming but that the gas hydrate system nevertheless reacts very sensitive to even seasonal temperature changes (Berndt et al. 2014). Here, we report about a methane seep site at the gas hydrate stability boundary (394 m water depth) that features unusual geochemical profiles indicative for non-steady state conditions. Sediment was recovered with a gravity corer (core length 210 cm) and samples were analyzed to study porewater geochemistry, methane concentration, authigenic carbonates, and microbial activity. Porewater profiles revealed two zones of sulfate-methane transition at 50 and 200 cm sediment depth. The twin zones were confirmed by a double peaking in sulfide, total alkalinity, anaerobic oxidation of methane, and sulfate reduction. d18O values sharply increased from around -2.8 ‰ between 0 and 126 cm to -1.2 ‰ below 126 cm sediment depth. While U/Th isotope measurements of authigenic seep carbonates that were collected from different depths of the core illustrated that methane seepage must be occurring at this site since at least 3000 years, the biogeochemical profiles suggest that methane flux must have been altered recently. By applying a multi-phase reaction-transport model using known initial parameters from the study site (e.g. water depth, temperature profile, salinity, and sediment surface concentrations of CH4, SO4, DIC, and POC) were able to show that the observed twin sulfate-methane transition zones are an ephemeral phenomenon occurring during increase of methane production in the sediment, which can be introduced by, e.g., gas hydrate dissociation. References Berndt, C., T. Feseker, T. Treude, S. Krastel, V. Liebetrau, H. Niemann, V. J. Bertics, I. Dumke, K. Dunnbier, B. Ferre, C. Graves, F. Gross, K. Hissmann, V. Huhnerbach, S. Krause, K. Lieser, J. Schauer and L. Steinle (2014). "Temporal constraints on hydrate-controlled methane seepage off svalbard." Science 343: 284-287. Westbrook, G. K., K. E. Thatcher, E. J. Rohling, A. M. Piotrowski, H. Pälike, A. H. Osborne, E. G. Nisbet, T. A. Minshull, M. Lanoiselle, R. H. James, V. Hühnerbach, D. Green, R. E. Fisher, A. J. Crocker, A. Chabert, C. Bolton, A. Beszczynska-Möller, C. Berndt and A. Aquilina (2009). "Escape of methane gas from the seabed along the West Spitsbergen continental margin." Geophys. Res. Let. 36: doi:10.1029/2009GL039191.

A simple headspace equilibration method for measuring dissolved methane

USGS Publications Warehouse

Magen, C; Lapham, L.L.; Pohlman, John W.; Marshall, Kristin N.; Bosman, S.; Casso, Michael; Chanton, J.P.

2014-01-01

Dissolved methane concentrations in the ocean are close to equilibrium with the atmosphere. Because methane is only sparingly soluble in seawater, measuring it without contamination is challenging for samples collected and processed in the presence of air. Several methods for analyzing dissolved methane are described in the literature, yet none has conducted a thorough assessment of the method yield, contamination issues during collection, transport and storage, and the effect of temperature changes and preservative. Previous extraction methods transfer methane from water to gas by either a "sparge and trap" or a "headspace equilibration" technique. The gas is then analyzed for methane by gas chromatography. Here, we revisit the headspace equilibration technique and describe a simple, inexpensive, and reliable method to measure methane in fresh and seawater, regardless of concentration. Within the range of concentrations typically found in surface seawaters (2-1000 nmol L-1), the yield of the method nears 100% of what is expected from solubility calculation following the addition of known amount of methane. In addition to being sensitive (detection limit of 0.1 ppmv, or 0.74 nmol L-1), this method requires less than 10 min per sample, and does not use highly toxic chemicals. It can be conducted with minimum materials and does not require the use of a gas chromatograph at the collection site. It can therefore be used in various remote working environments and conditions.

Photochemical ozone formation from petroleum refinery emissions

NASA Astrophysics Data System (ADS)

Sexton, Ken; Westberg, Hal

Atmospheric emissions from the Marathon oil refinery at Robinson, Illinois were investigated during June and July 1977. Surface and aerial measurements were used to provide an integrated, three dimensional monitoring network. Concentrations of ozone, oxides of nitrogen, sulfur dioxide, methane, carbon dioxide, individual non-methane hydrocarbons and halocarbons were recorded on a routine basis. In addition, meteorological parameters such as wind speed, wind direction, solar radiation and mixing height were also measured. The field monitoring study focused on three major areas: (1) characterization of gaseous components within the refinery effluent, especially nonmethane hydrocarbons and nitrogen oxides; (2) natural sunlight bag irradiation experiments to examine ozone forming potential of refinery emissions and (3) aerial measurements of changes in plume chemistry during the first six to eight hours of transport. Results indicate levels of hydrocarbons and nitrogen oxides were elevated downwind of the refinery. Concentrations within the effluent exceeded background values by as much as 300- and 10-fold, respectively. Irradiations of captured refinery emissions suggest excess photochemical ozone can be produced in the first 6 h, with amounts varying according to NMHC/NO x, ratios and initial NMHC concentrations. Real-time measurements on board the aircraft documented instances of ozone buildup in the refinery plume as it drifted downwind.

Activities That Reduce Global Anthropogenic Methane Emissions Grant - Closed Announcement FY 2012

EPA Pesticide Factsheets

Grant to fund eligible projects for activities that advance near-term, cost-effective methane abatement or recovery and use as a clean energy source, and support the goals of of theGlobal Methane Initiative.

40 CFR 63.1426 - Process vent requirements for determining organic HAP concentration, control efficiency, and...

Code of Federal Regulations, 2014 CFR

2014-07-01

... Production § 63.1426 Process vent requirements for determining organic HAP concentration, control efficiency..., total organic HAP, or as TOC minus methane and ethane according to the procedures specified. When... methane and ethane) concentrations in all process vent streams and primary and secondary fuels introduced...

PORTABLE METHANE FLUX METER - PHASE I

EPA Science Inventory

This Phase I project will investigate achieving a low power, portable system for measuring methane concentrations and fluxes. The system will combine diode laser-based trace gas concentration measurements with rapid wind speed measurements to determine fluxes using eddy cor...

Interactions between nitrogen cycling and methane oxidation in the pelagic waters of the Gulf of Mexico.

NASA Astrophysics Data System (ADS)

Joye, S. B.; Weber, S.; Battles, J.; Montoya, J. P.

2014-12-01

Methane is an important greenhouse gas that plays a critical role in climate variation. Although a variety of marine methane sources and sinks have been identified, key aspects of the fate of methane in the ocean remain poorly constrained. At cold seeps in the Gulf of Mexico and elsewhere, methane is introduced into the overlying water column via fluid escape from the seabed. We quantified the fate of methane in the water column overlying seafloor cold seeps, in a brine basin, and at several control sites. Our goals were to determine the factors that regulated methane consumption and assimilation and to explore how these controlling factors varied among and between sites. In particular, we examined the impact of nitrogen availability on methane oxidation and studied the ability of methane oxidizing bacteria to fix molecular nitrogen. Methane oxidation rates were highest in the methane rich bottom waters of natural hydrocabron seeps. At these sites, inorganic nitrogen addition stimulated methane oxidation in laboratory experiments. In vitro shipboard experiments revealed that rates of methane oxidation and nitrogen fixation were correlated strongly, suggesting that nitrogen fixation may have been mediated by methanotrophic bacteria. The highest rates of methane oxidation and nitrogen fixation were observed in the deepwater above at natural hydrocarbon seeps. Rates of methane oxidation were substantial along the chemocline of a brine basin but in these ammonium-rich brines, addition of inorganic nitrogen had little impact on methane oxidation suggesting that methanotrophy in these waters were not nitrogen limited. Control sites exhibited the lowest methane concentrations and methane oxidation rates but even these waters exhibited substantial potential for methane oxidation when methane and inorganic nitrogen concentrations were increased. Together, these data suggest that the availability of inorganic nitrogen plays a critical role in regulating methane oxidation in pelagic ocean waters. Some methanotrophs may obtain a competitive advantage in nitrogen-limited oceanic environments by fixing molecular nitrogen. The importance of such "methano-diazotrophy" on a global scale warrants further investigation.

75 FR 75498 - Petitions for Modification of Existing Mandatory Safety Standards

Federal Register 2010, 2011, 2012, 2013, 2014

2010-12-03

... 75.151 will continuously monitor for methane immediately before and during the use of non... if methane is detected in concentrations at or above 1.0 percent methane; (4) when 1.0 percent or more of methane is detected while the non-permissible electronic equipment is being used, the equipment...

Analysis of Percent On-Cell Reformation of Methane in SOFC Stacks: Thermal, Electrical and Stress Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Recknagle, Kurtis P.; Yokuda, Satoru T.; Jarboe, Daniel T.

2006-04-07

This report summarizes a parametric analysis performed to determine the effect of varying the percent on-cell reformation (OCR) of methane on the thermal and electrical performance for a generic, planar solid oxide fuel cell (SOFC) stack design. OCR of methane can be beneficial to an SOFC stack because the reaction (steam-methane reformation) is endothermic and can remove excess heat generated by the electrochemical reactions directly from the cell. The heat removed is proportional to the amount of methane reformed on the cell. Methane can be partially pre-reformed externally, then supplied to the stack, where rapid reaction kinetics on the anodemore » ensures complete conversion. Thus, the thermal load varies with methane concentration entering the stack, as does the coupled scalar distributions, including the temperature and electrical current density. The endotherm due to the reformation reaction can cause a temperature depression on the anode near the fuel inlet, resulting in large thermal gradients. This effect depends on factors that include methane concentration, local temperature, and stack geometry.« less

Elimination of methane in exhaust gas from biogas upgrading process by immobilized methane-oxidizing bacteria.

PubMed

Wu, Ya-Min; Yang, Jing; Fan, Xiao-Lei; Fu, Shan-Fei; Sun, Meng-Ting; Guo, Rong-Bo

2017-05-01

Biogas upgrading is essential for the comprehensive utilization of biogas as substitute of natural gas. However, the methane in the biogas can be fully recovered during the upgrading process of biogas, and the exhaust gas produced during biogas upgrading may contain a very low concentration of methane. If the exhaust gas with low concentration methane releases to atmosphere, it will be harmful to environment. In addition, the utilization of large amounts of digestate produced from biogas plant is another important issue for the development of biogas industry. In this study, solid digestate was used to produce active carbon, which was subsequently used as immobilized material for methane-oxidizing bacteria (MOB) in biofilter. Biofilter with MOB immobilized on active carbon was used to eliminate the methane in exhaust gas from biogas upgrading process. Results showed porous active carbon was successfully made from solid digestate. The final methane elimination capacity of immobilized MOB reached about 13molh -1 m -3 , which was more 4 times higher than that of MOB without immobilization. Copyright © 2017 Elsevier Ltd. All rights reserved.

Carbon and hydrogen isotopic characterization of methane from wetlands and lakes of the Yukon-Kuskokwim Delta, Western Alaska

NASA Technical Reports Server (NTRS)

Martens, Christopher S.; Kelley, Cheryl A.; Chanton, Jeffrey P.; Showers, William J.

1992-01-01

The results are reported of a study of the carbon and hydrogen isotopic composition of methane from tundra environments of the Yukon-Kuskokwin Delta of western Alaska. The delta C-13 value of diffusive methane emissions from wet meadow tundra of the Delta is -65.82 +/- 2.21 per mil (n=18). Detritus-rich sediments of tundra lakes are loaded with methane-rich gas bubbles during the warm season. Spatial trend is the major gas concentration and isotopic values of methane in these gas bubbles appear to reflect processes associated with production rate and mechanisms; high methane concentrations, lightest delta C-13 values, the heaviest delta D value occur in detritus-rich sediments isolated from emergent vegetation. Heavier delta C-13 and lighter delta D values in methane from heavily vegetated lake margins suggest a shift toward a larger role for acetate fermentation in association with aquatic plants and plant detritus. Bubble ebullition is estimated to account for up to 17 percent of total Delta methane emissions.

Methane transport mechanisms and isotopic fractionation in emergent macrophytes of an Alaskan tundra lake

NASA Technical Reports Server (NTRS)

Chanton, Jeffrey P.; Martens, Christopher S.; Kelley, Cheryl A.; Crill, Patrick M.; Showers, William J.

1992-01-01

The stable carbon isotopic composition of methane associated with and emitted by the two dominant emergent macrophytes abundant in the many Alaskan tundra lakes, Carex rostrata and Arctophila fulva, is determined. The carbon isotopic composition of the methane was -58.6 +/- 0.5 (n=2) for Arctophila and -66.6 +/- 2.5 (n=6) for Carex. The methane emitted by these species is depleted in C-13 by 12 per mil for Arctophila and 18 per mil for Carex relative to methane withdrawn from plant stems 1-2 cm below the waterline. The results suggest more rapid transport of (C-12)H4 relative to (C-13)H4 through plants to the atmosphere. Plant stem methane concentrations ranged from 0.2 to 4.0 percent in Arctophila, with an isotopic composition of -46.1 +/- 4.3 percent (n=8). Carex stem methane concentrations ranged from 150 to 1200 ppm, with an isotopic composition of -48.3 +/- 1.4 per mil (n=3).

Regulation of Methane Oxidation in a Freshwater Wetland by Water Table Changes and Anoxia

NASA Technical Reports Server (NTRS)

Roslev, Peter; King, Gary M.

1996-01-01

The effects of water table fluctuations and anoxia on methane emission and methane oxidation were studied in a freshwater marsh. Seasonal aerobic methane oxidation rates varied between 15% and 76% of the potential diffusive methane flux (diffusive flux in the absence of aerobic oxidation). On an annual basis, approximately 43% of the methane diffusing into the oxic zone was oxidized before reaching the atmosphere. The highest methane oxidation was observed when the water table was below the peat surface. This was confirmed in laboratory experiments where short-term decreases in water table levels increased methane oxidation but also net methane emission. Although methane emission was generally not observed during the winter, stems of soft rush (Juncus effusus) emitted methane when the marsh was ice covered. Indigenous methanotrophic bacteria from the wetiand studied were relatively anoxia tolerant. Surface peat incubated under anoxic conditions maintained 30% of the initial methane oxidation capacity after 32 days of anoxia. Methanotrophs from anoxic peat initiated aerobic methane oxidation relatively quickly after oxygen addition (1-7 hours). These results were supported by culture experiments with the methanotroph Methylosinus trichosporium OB3b. This organism maintained a greater capacity for aerobic methane oxidation when starved under anoxic compared to oxic conditions. Anoxic incubation of M. trichosporium OB3b in the presence of sulfide (2 mM) and a low redox potential (-110 mV) did not decrease the capacity for methane oxidation relative to anoxic cultures incubated without sulfide. The results suggest that aerobic methane oxidation was a major regulator of seasonal methane emission front the investigated wetland. The observed water table fluctuations affected net methane oxidation presumably due to associated changes in oxygen gradients. However, changes from oxic to anoxic conditions in situ had relatively little effect on survival of the methanotrophic bacteria and thus on methane oxidation potential per se.

Methane oxidation in an intensively cropped tropical rice field soil under long-term application of organic and mineral fertilizers.

PubMed

Nayak, D R; Babu, Y Jagadeesh; Datta, A; Adhya, T K

2007-01-01

Methane (CH4) oxidation is the only known biological sink process for mitigating atmospheric and terrestrial emissions of CH4, a major greenhouse gas. Methane oxidation in an alluvial soil planted to rice (Oryza sativa L.) under long-term application of organic (compost with a C/N ratio of 21.71), and mineral fertilizers was measured in a field-cum-laboratory incubation study. Oxidation rates were quantified in terms of decrease in the concentration of CH4 in the headspace of incubation vessels and expressed as half-life (t(1)2) values. Methane oxidation rates significantly differed among the treatments and growth stages of the rice crop. Methane oxidation rates were high at the maximum tillering and maturity stages, whereas they were low at grain-filling stage. Methane oxidation was low (t(1)2) = 15.76 d) when provided with low concentration of CH4. On the contrary, high concentration of CH4 resulted in faster oxidation (t(1)2) = 6.67 d), suggesting the predominance of "low affinity oxidation" in rice fields. Methane oxidation was stimulated following the application of mineral fertilizers or compost implicating nutrient limitation as one of the factors affecting the process. Combined application of compost and mineral fertilizer, however, inhibited CH4 oxidation probably due to N immobilization by the added compost. The positive effect of mineral fertilizer on CH4 oxidation rate was evident only at high CH4 concentration (t(1)2 = 4.80 d), while at low CH4 concentration their was considerable suppression (t(1) = 17.60 d). Further research may reveal that long-term application of fertilizers, organic or inorganic, may not inhibit CH4 oxidation.

Seismic reflections identify finite differences in gas hydrate resources

USGS Publications Warehouse

Dillon, William P.; Max, M.

1999-01-01

Gas hydrate is a gas-bearing, ice-like crystalline solid. The substance's build ing blocks consist of a gas molecule (generally methane) sur-rounded by a cage of water molecules. The total amount of methane in hydrate in the world is immense - the most recent speculative estimate centers on values of 21x1015 cu meters. Thus, it may represent a future energy resource. This estimate was presented by Keith Kvenvolden at the International Symposium on Methane Hydrates, Resources in the Near Future, sponsor ed by Japanese National Oil Company (Tokyo, October, 1998).But, as with any natural resource, there is a need to find naturally occurring concentrations in order to effectively extract gas. We need to answer four basic questions:Do methane hydrate concentrations suitable for methane extraction exist?How can we recognize these concentrations?Where are concentrations located?What processes control methane hydrate concentrations?Gas hydrate occurs naturally at the pressure/ temperature/chemical conditions that are present within ocean floor sediments at water depths greater than about 500 meters. The gas hydrate stability zone (GHSZ) extends from the sea bottom downward to a depth where the natural increase in temperature causes the hydrate to melt (dissociate), even though the downward pressure increase is working to increase gas hydrate stability.Thus, the base of the GHSZ tends to parallel the seafloor at any given water depth (pressure), because the sub-seafloor isotherms (depths of constant temperature) generally parallel the seafloor. The layer at which gas hydrate is stable commonly extends from the sea floor to several hundred meters below it. The gas in most gas hydrates is methane, generated by bacteria in the sediments. In some cases, it can be higher carbon-number, thermogenic hydrocarbon gases that rise from greater depths.

Methane on Mars: Thermodynamic Equilibrium and Photochemical Calculations

NASA Technical Reports Server (NTRS)

Levine, J. S.; Summers, M. E.; Ewell, M.

2010-01-01

The detection of methane (CH4) in the atmosphere of Mars by Mars Express and Earth-based spectroscopy is very surprising, very puzzling, and very intriguing. On Earth, about 90% of atmospheric ozone is produced by living systems. A major question concerning methane on Mars is its origin - biological or geological. Thermodynamic equilibrium calculations indicated that methane cannot be produced by atmospheric chemical/photochemical reactions. Thermodynamic equilibrium calculations for three gases, methane, ammonia (NH3) and nitrous oxide (N2O) in the Earth s atmosphere are summarized in Table 1. The calculations indicate that these three gases should not exist in the Earth s atmosphere. Yet they do, with methane, ammonia and nitrous oxide enhanced 139, 50 and 12 orders of magnitude above their calculated thermodynamic equilibrium concentration due to the impact of life! Thermodynamic equilibrium calculations have been performed for the same three gases in the atmosphere of Mars based on the assumed composition of the Mars atmosphere shown in Table 2. The calculated thermodynamic equilibrium concentrations of the same three gases in the atmosphere of Mars is shown in Table 3. Clearly, based on thermodynamic equilibrium calculations, methane should not be present in the atmosphere of Mars, but it is in concentrations approaching 30 ppbv from three distinct regions on Mars.

A comparative study of leachate quality and biogas generation in simulated anaerobic and hybrid bioreactors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Qiyong; Tian, Ying; Wang, Shen

2015-07-15

Highlights: • Temporary aeration shortened the initial acid inhibition phase for methanogens. • COD decreased faster in the hybrid bioreactor than that in the anaerobic control. • Methane generations from hybrid bioreactors were 133.4 L/kg{sub vs} and 113.2 L/kg{sub vs}. • MSW settlement increased with increasing the frequency of intermittent aeration. - Abstract: Research has been conducted to compare leachate characterization and biogas generation in simulated anaerobic and hybrid bioreactor landfills with typical Chinese municipal solid waste (MSW). Three laboratory-scale reactors, an anaerobic (A1) and two hybrid bioreactors (C1 and C2), were constructed and operated for about 10 months. Themore » hybrid bioreactors were operated in an aerobic–anaerobic mode with different aeration frequencies by providing air into the upper layer of waste. Results showed that the temporary aeration into the upper layer aided methane generation by shortening the initial acidogenic phase because of volatile fatty acids (VFAs) reduction and pH increase. Chemical oxygen demand (COD) decreased faster in the hybrid bioreactors, but the concentrations of ammonia–nitrogen in the hybrid bioreactors were greater than those in the anaerobic control. Methanogenic conditions were established within 75 d and 60 d in C1 and C2, respectively. However, high aeration frequency led to the consumption of organic matters by aerobic degradation and resulted in reducing accumulative methane volume. The temporary aeration enhanced waste settlement and the settlement increased with increasing the frequency of aeration. Methane production was inhibited in the anaerobic control; however, the total methane generations from hybrid bioreactors were 133.4 L/kg{sub vs} and 113.2 L/kg{sub vs}. As for MSW with high content of food waste, leachate recirculation right after aeration stopped was not recommended due to VFA inhibition for methanogens.« less

Developing methanogenic microbial consortia from diverse coal sources and environments

DOE PAGES

Fuertez, John; Boakye, Richard; McLennan, John; ...

2017-08-18

Biogenic gas production is a promising alternative or supplement to conventional methane extraction from coalbeds. Adsorbed and free gas, generated over geologic time, can be supplemented with biogenic gas during short-term engineering operations. There are two generic protocols for doing this. The first is to contact the coal with nutrients to support native bacterial development. The second approach is to inject appropriately cultured ex-situ consortia into subsurface coal accumulations. Research has mainly focused on the former: in-situ stimulation of native microbial communities with added nutrients. Relatively few studies have been conducted on the strategies for enriching ex-situ microbial populations undermore » initial atmospheric exposure for subsequent injection into coal seams to stimulate biodegradation, and methanogenesis. In order to evaluate the feasibility of ex-situ cultivation, natural microbial populations were collected from various hydrocarbon-rich environments and locations characterized by natural methanogenesis. Different rank coals (i.e., lignite, sub-bituminous, bituminous), complex hydrocarbon sources (i.e., oil shale, waxy crude), hydrocarbon seeps, and natural biogenic environments were incorporated in the sampling. Three levels of screening (down-selection to high grade the most productive consortia) allowed selection of microbial populations, favorable nutrient amendments, sources of the microbial community, and quantification of methane produced from various coal types. Incubation periods of up to twenty-four weeks were evaluated at 23 °C. Headspace concentrations of CH 4 and CO 2 were analyzed by gas chromatography. After a two-week incubation period of the most promising microbes, generated headspace gas concentrations reached 873,400 ppm (154 sft 3/ton or 4.8 scm 3/g) for methane and 176,370 ppm (31 sft 3/ton or 0.9 scm 3/g) for carbon dioxide. Rudimentary statistical assessments – variance analysis (ANOVA) of a single factor - were used to identify trends and levels of significance or impact of the consortia enrichment. We then demonstrated that microbial communities from coal and lake sediments can be enriched and adapted to effectively generate methane under initial atmospheric exposure. The development and enrichment of these methanogenic consortia is described.« less

Developing methanogenic microbial consortia from diverse coal sources and environments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fuertez, John; Boakye, Richard; McLennan, John

Biogenic gas production is a promising alternative or supplement to conventional methane extraction from coalbeds. Adsorbed and free gas, generated over geologic time, can be supplemented with biogenic gas during short-term engineering operations. There are two generic protocols for doing this. The first is to contact the coal with nutrients to support native bacterial development. The second approach is to inject appropriately cultured ex-situ consortia into subsurface coal accumulations. Research has mainly focused on the former: in-situ stimulation of native microbial communities with added nutrients. Relatively few studies have been conducted on the strategies for enriching ex-situ microbial populations undermore » initial atmospheric exposure for subsequent injection into coal seams to stimulate biodegradation, and methanogenesis. In order to evaluate the feasibility of ex-situ cultivation, natural microbial populations were collected from various hydrocarbon-rich environments and locations characterized by natural methanogenesis. Different rank coals (i.e., lignite, sub-bituminous, bituminous), complex hydrocarbon sources (i.e., oil shale, waxy crude), hydrocarbon seeps, and natural biogenic environments were incorporated in the sampling. Three levels of screening (down-selection to high grade the most productive consortia) allowed selection of microbial populations, favorable nutrient amendments, sources of the microbial community, and quantification of methane produced from various coal types. Incubation periods of up to twenty-four weeks were evaluated at 23 °C. Headspace concentrations of CH 4 and CO 2 were analyzed by gas chromatography. After a two-week incubation period of the most promising microbes, generated headspace gas concentrations reached 873,400 ppm (154 sft 3/ton or 4.8 scm 3/g) for methane and 176,370 ppm (31 sft 3/ton or 0.9 scm 3/g) for carbon dioxide. Rudimentary statistical assessments – variance analysis (ANOVA) of a single factor - were used to identify trends and levels of significance or impact of the consortia enrichment. We then demonstrated that microbial communities from coal and lake sediments can be enriched and adapted to effectively generate methane under initial atmospheric exposure. The development and enrichment of these methanogenic consortia is described.« less

Improving biogas production from continuous co-digestion of oily wastewater and waste-activated sludge by hydrodynamic cavitation pre-treatment.

PubMed

Habashi, Nima; Alighardashi, Abolghasem; Mennerich, Artur; Mehrdadi, Nasser; Torabian, Ali

2018-04-01

Hydrodynamic cavitation (HC) was evaluated as a pretreatment for synthetic oily wastewater (OWW) to be co-digested with waste-activated sludge (WAS). The main objective of the present research was the enhancement of biogas production by the application of HC pretreatment. HC was applied to the OWW, and the OWW and WAS were added to a 50 L continuous digestion reactor. As a control system, an identical digestion reactor was set up for co-digestion of the WAS and the OWW without pretreatment. The reactors were initially filled with inoculum and the hydraulic retention time (HRT) was set to 22 d. The HRT was gradually reduced to 19, 16, and finally 13 d, but the substrate quality was kept constant. The loading rate, accordingly, increased from 0.86 to 1.46 g TVS/(L d). The biogas volume was recorded online and its quality was analyzed regularly. The HC improved biogas production up to 43% at 22 d of HRT. Reducing the HRT decreased biogas production from the main reactor while that of the control reactor was more or less constant. HC also increased the biogas methane content; the methane concentration of the main reactor was about 3% higher than the methane concentration of the control reactor. The main reactor experienced no clogging or accumulation of fatty materials.

Biological Pretreatment of Chicken Feather and Biogas Production from Total Broth.

PubMed

Patinvoh, Regina J; Feuk-Lagerstedt, Elisabeth; Lundin, Magnus; Sárvári Horváth, Ilona; Taherzadeh, Mohammad J

2016-12-01

Chicken feathers are available in large quantities around the world causing environmental challenges. The feathers are composed of keratin that is a recalcitrant protein and is hard to degrade. In this work, chicken feathers were aerobically pretreated for 2-8 days at total solid concentrations of 5, 10, and 20 % by Bacillus sp. C 4 , a bacterium that produces both α- and β-keratinases. Then, the liquid fraction (feather hydrolysate) as well as the total broth (liquid and solid fraction of pretreated feathers) was used as substrates for biogas production using anaerobic sludge or bacteria granules as inoculum. The biological pretreatment of feather waste was productive; about 75 % of feather was converted to soluble crude protein after 8 days of degradation at initial feather concentration of 5 %. Bacteria granules performed better during anaerobic digestion of untreated feathers, resulting in approximately two times more methane yield (i.e., 199 mlCH 4 /gVS compared to 105 mlCH 4 /gVS when sludge was used). Pretreatment improved methane yield by 292 and 105 % when sludge and granules were used on the hydrolysate. Bacteria granules worked effectively on the total broth, yielded 445 mlCH 4 /gVS methane, which is 124 % more than that obtained with the same type of inoculum from untreated feather.

Methane production correlates positively with methanogens, sulfate-reducing bacteria and pore water acetate at an estuarine brackish-marsh landscape scale

NASA Astrophysics Data System (ADS)

Tong, C.; She, C. X.; Jin, Y. F.; Yang, P.; Huang, J. F.

2013-11-01

Methane production is influenced by the abundance of methanogens and the availability of terminal substrates. Sulfate-reducing bacteria (SRB) also play an important role in the anaerobic decomposition of organic matter. However, the relationships between methane production and methanogen populations, pore water terminal substrates in estuarine brackish marshes are poorly characterized, and even to our knowledge, no published research has explored the relationship between methane production rate and abundance of SRB and pore water dimethyl sulfide (DMS) concentration. We investigated methane production rate, abundances of methanogens and SRB, concentrations of pore water terminal substrates and electron acceptors at a brackish marsh landscape dominated by Phragmites australis, Cyperus malaccensis and Spatina alterniflora marshes zones in the Min River estuary. The average rates of methane production at a soil depth of 30 cm in the three marsh zones were 0.142, 0.058 and 0.067 μg g-1 d-1, respectively. The abundance of both methanogens and SRB in the soil of the P. australis marsh with highest soil organic carbon content was higher than in the C. malaccensis and S. alterniflora marshes. The abundance of methanogens and SRB in the three soil layers was statistically indistinguishable. Mean pore water DMS concentrations at a soil depth of 30 cm under the S. alterniflora marsh were higher than those in the C. malaccensis and P. australis marshes. Methane production rate increased with the abundance of both methanogens and SRB across three marsh zones together at the landscape scale, and also increased with the concentration of pore water acetate, but did not correlate with concentrations of pore water DMS and dissolved CO2. Our results suggest that, provided that substrates are available in ample supply, methanogens can continue to produce methane regardless of whether SRB are prevalent in estuarine brackish marshes.

Impact of an historic underground gas well blowout on the current methane chemistry in a shallow groundwater system

PubMed Central

Schout, Gilian; Hartog, Niels; Hassanizadeh, S. Majid; Griffioen, Jasper

2018-01-01

Blowouts present a small but genuine risk when drilling into the deep subsurface and can have an immediate and significant impact on the surrounding environment. Nevertheless, studies that document their long-term impact are scarce. In 1965, a catastrophic underground blowout occurred during the drilling of a gas well in The Netherlands, which led to the uncontrolled release of large amounts of natural gas from the reservoir to the surface. In this study, the remaining impact on methane chemistry in the overlying aquifers was investigated. Methane concentrations higher than 10 mg/L (n = 12) were all found to have δ13C-CH4 values larger than −30‰, typical of a thermogenic origin. Both δ13C-CH4 and δD-CH4 correspond to the isotopic composition of the gas reservoir. Based on analysis of local groundwater flow conditions, this methane is not a remnant but most likely the result of ongoing leakage from the reservoir as a result of the blowout. Progressive enrichment of both δ13C-CH4 and δD-CH4 is observed with increasing distance and decreasing methane concentrations. The calculated isotopic fractionation factors of εC = 3 and εD = 54 suggest anaerobic methane oxidation is partly responsible for the observed decrease in concentrations. Elevated dissolved iron and manganese concentrations at the fringe of the methane plume show that oxidation is primarily mediated by the reduction of iron and manganese oxides. Combined, the data reveal the long-term impact that underground gas well blowouts may have on groundwater chemistry, as well as the important role of anaerobic oxidation in controlling the fate of dissolved methane. PMID:29279383

A UAV-based gas sensing system for detecting fugitive methane emissions

NASA Astrophysics Data System (ADS)

Hugenholtz, C.; Barchyn, T.; Myshak, S.; Bauer, J.

2016-12-01

Methane is one of the most prevalent greenhouse gases emitted by human activities and is a major component of government-led initiatives to reduce GHG emissions in Canada, the USA, and elsewhere. In light of growing demand for measurements and verification of atmospheric methane concentration across the oil and gas supply chain, an autonomous airborne gas sensing system was developed that combines a small UAV and a lightweight gas monitor. This paper outlines the technology, analytics, and presents data from a case study to demonstrate the proof of concept. The UAV is a fixed-wing (2.2 m wingspan), battery-operated platform, with a flight endurance of 80-120 minutes. The gas sensor onboard the UAV is a tunable diode laser absorption spectrometer that uses an integrated transmitter/receiver unit and a remote, passive retro-reflector. The transmitter is attached to one of the winglets, while the other is coated with reflective material. The total weight of the UAV and gas sensor is 4.3 kg. During flight, the system operates autonomously, acquiring averages of raw measurements at 1 Hz, with a recorded resolution of 0.0455 ppm. The onboard measurement and control unit (MCU) for the gas sensor is integrated with the UAV autopilot in order to provide time-stamped and geotagged concentration measurements, and to provide real-time flight adjustments when concentration exceeds a pre-determined threshold. The data are retrieved from the MCU when the mission is complete. In order to demonstrate the proof of concept, we present results from a case study and outline opportunities for translating the measurements into decision making.

Enhanced methane emissions from oil and gas exploration areas to the atmosphere--the central Bohai Sea.

PubMed

Zhang, Yong; Zhao, Hua-de; Zhai, Wei-dong; Zang, Kun-peng; Wang, Ju-ying

2014-04-15

The distributions of dissolved methane in the central Bohai Sea were investigated in November 2011, May 2012, July 2012, and August 2012. Methane concentration in surface seawater, determined using an underway measurement system combined with wavelength-scanned cavity ring-down spectroscopy, showed marked spatiotemporal variations with saturation ratio from 107% to 1193%. The central Bohai Sea was thus a source of atmospheric methane during the survey periods. Several episodic oil and gas spill events increased surface methane concentration by up to 4.7 times and raised the local methane outgassing rate by up to 14.6 times. This study demonstrated a method to detect seafloor CH4 leakages at the sea surface, which may have applicability in many shallow sea areas with oil and gas exploration activities around the world. Copyright © 2014 Elsevier Ltd. All rights reserved.

Testing short-range migration of microbial methane as a hydrate formation mechanism: Results from Andaman Sea and Kumano Basin drill sites and global implications

NASA Astrophysics Data System (ADS)

Malinverno, Alberto; Goldberg, David S.

2015-07-01

Methane gas hydrates in marine sediments often concentrate in coarse-grained layers surrounded by fine-grained marine muds that are hydrate-free. Methane in these hydrate deposits is typically microbial, and must have migrated from its source as the coarse-grained sediments contain little or no organic matter. In "long-range" migration, fluid flow through permeable layers transports methane from deeper sources into the gas hydrate stability zone (GHSZ). In "short-range" migration, microbial methane is generated within the GHSZ in fine-grained sediments, where small pore sizes inhibit hydrate formation. Dissolved methane can then diffuse into adjacent sand layers, where pore size does not restrict hydrate formation and hydrates can accumulate. Short-range migration has been used to explain hydrate accumulations in sand layers observed in drill sites on the northern Cascadia margin and in the Gulf of Mexico. Here we test the feasibility of short-range migration in two additional locations, where gas hydrates have been found in coarse-grained volcanic ash layers (Site NGHP-01-17, Andaman Sea, Indian Ocean) and turbidite sand beds (Site IODP-C0002, Kumano forearc basin, Nankai Trough, western Pacific). We apply reaction-transport modeling to calculate dissolved methane concentration and gas hydrate amounts resulting from microbial methane generated within the GHSZ. Model results show that short-range migration of microbial methane can explain the overall amounts of methane hydrate observed at the two sites. Short-range migration has been shown to be feasible in diverse margin environments and is likely to be a widespread methane transport mechanism in gas hydrate systems. It only requires a small amount of organic carbon and sediment sequences consisting of thin coarse-grained layers that can concentrate microbial methane generated within thick fine-grained sediment beds; these conditions are common along continental margins around the globe.

Thinking Like a Wildcatter: Prospecting for Methane in Arabia Terra, Mars

NASA Technical Reports Server (NTRS)

Allen, C. C.; Oehler, D. Z.

2005-01-01

Methane has been detected in the martian atmosphere at a concentration of approximately 10 ppb. The lifetime of such methane against decomposition by solar radiation is approximately 300 years, strongly suggesting that methane is currently being released to the atmosphere. By analogy to Earth, possible methane sources on Mars include active volcanism, hot springs, frozen methane clathrates, thermally-matured sedimentary organic matter, and extant microbial metabolism. The discovery of any one of these sources would revolutionize our understanding of Mars.

Effect of nickel ions on anaerobic methane production from water hyacinth.

PubMed

Cai, Xuan; Hong, Zi-Jian; Dai, Rui-Hua; Liu, Yan; Liu, Xiang

2012-01-01

The effect of different concentrations of nickel ions (Ni(2+), 0, 10, 40 and 80 mg/L) on the anaerobic methane production of water hyacinth were investigated. Under these four concentrations, the methane production in 40 d was 2,275, 2,703, 3,210 and 2,481 mL, respectively. This situation illustrated that the Ni(2+) promoted the growth of hydrogen-producing acetic acid bacteria and methanogenic bacteria, even at high concentrations (i.e. 40-80 mg/L). The highest methane production per unit weight water hyacinth reached 206 mL/gTS with 40 mg/L Ni(2+). Meanwhile, the modified Gompertz and Logistic equations were applied to describe the effect on anaerobic culture of Ni(2+). According to these models, the values of methane production potential (mL) for four concentrations were in the following order: 40 mg/L (3,123.42 ± 60.08) > 10 mg/L (2,541.16 ± 46.94) > 80 mg/L (2,432.36 ± 40.18) > 0 mg/L (2,238.10 ± 31.90). According to the analysis of the digestate, the residual concentration of Ni(2+) was approximately 1.05-4.9 mg/L, which was relatively low compared with the Ni(2+) concentrations in the raw feedstock. The results would provide academic guidance and technical support for treatment of water hyacinth with an accumulation of heavy metals.

Application of portable gas detector in point and scanning method to estimate spatial distribution of methane emission in landfill.

PubMed

Lando, Asiyanthi Tabran; Nakayama, Hirofumi; Shimaoka, Takayuki

2017-01-01

Methane from landfills contributes to global warming and can pose an explosion hazard. To minimize these effects emissions must be monitored. This study proposed application of portable gas detector (PGD) in point and scanning measurements to estimate spatial distribution of methane emissions in landfills. The aims of this study were to discover the advantages and disadvantages of point and scanning methods in measuring methane concentrations, discover spatial distribution of methane emissions, cognize the correlation between ambient methane concentration and methane flux, and estimate methane flux and emissions in landfills. This study was carried out in Tamangapa landfill, Makassar city-Indonesia. Measurement areas were divided into basic and expanded area. In the point method, PGD was held one meter above the landfill surface, whereas scanning method used a PGD with a data logger mounted on a wire drawn between two poles. Point method was efficient in time, only needed one person and eight minutes in measuring 400m 2 areas, whereas scanning method could capture a lot of hot spots location and needed 20min. The results from basic area showed that ambient methane concentration and flux had a significant (p<0.01) positive correlation with R 2 =0.7109 and y=0.1544 x. This correlation equation was used to describe spatial distribution of methane emissions in the expanded area by using Kriging method. The average of estimated flux from scanning method was 71.2gm -2 d -1 higher than 38.3gm -2 d -1 from point method. Further, scanning method could capture the lower and higher value, which could be useful to evaluate and estimate the possible effects of the uncontrolled emissions in landfill. Copyright © 2016 Elsevier Ltd. All rights reserved.

Assessing Methane in Shallow Groundwater in Unconventional Oil and Gas Play Areas, Eastern Kentucky.

PubMed

Zhu, Junfeng; Parris, Thomas M; Taylor, Charles J; Webb, Steven E; Davidson, Bart; Smath, Richard; Richardson, Stephen D; Molofsky, Lisa J; Kromann, Jenna S; Smith, Ann P

2018-05-01

The expanding use of horizontal drilling and hydraulic fracturing technology to produce oil and gas from tight rock formations has increased public concern about potential impacts on the environment, especially on shallow drinking water aquifers. In eastern Kentucky, horizontal drilling and hydraulic fracturing have been used to develop the Berea Sandstone and the Rogersville Shale. To assess baseline groundwater chemistry and evaluate methane detected in groundwater overlying the Berea and Rogersville plays, we sampled 51 water wells and analyzed the samples for concentrations of major cations and anions, metals, dissolved methane, and other light hydrocarbon gases. In addition, the stable carbon and hydrogen isotopic composition of methane (δ 13 C-CH 4 and δ 2 H-CH 4 ) was analyzed for samples with methane concentration exceeding 1 mg/L. Our study indicates that methane is a relatively common constituent in shallow groundwater in eastern Kentucky, where methane was detected in 78% of the sampled wells (40 of 51 wells) with 51% of wells (26 of 51 wells) exhibiting methane concentrations above 1 mg/L. The δ 13 C-CH 4 and δ 2 H-CH 4 ranged from -84.0‰ to -58.3‰ and from -246.5‰ to -146.0‰, respectively. Isotopic analysis indicated that dissolved methane was primarily microbial in origin formed through CO 2 reduction pathway. Results from this study provide a first assessment of methane in the shallow aquifers in the Berea and Rogersville play areas and can be used as a reference to evaluate potential impacts of future horizontal drilling and hydraulic fracturing activities on groundwater quality in the region. © 2017, National Ground Water Association.

Further developments in oxidation of methane traces with radiofrequency discharge

NASA Technical Reports Server (NTRS)

Flamm, D. L.; Wydeven, T. J.

1977-01-01

The radiofrequency discharge, previously shown to oxidize trace levels of methane in oxygen, was studied with contaminated air at 50, 600, and 760 torr. As with oxygen, the concentration of methane traces could be reduced by several orders of magnitude, and no organic reaction products were detected in the effluent; however, substantial concentrations of NOx (0.1-6%) were formed during treatment. The concentration of NOx was decreased by using a large diameter electrode. There is evidence that the process will oxidize N2 and NO as well as organic impurities in oxygen or oxygen/inert gas atmospheres.

Constructing a Spatially Resolved Methane Emission Inventory of Natural Gas Production and Distribution over Contiguous United States

NASA Astrophysics Data System (ADS)

Li, X.; Omara, M.; Adams, P. J.; Presto, A. A.

2017-12-01

Methane is the second most powerful greenhouse gas after Carbon Dioxide. The natural gas production and distribution accounts for 23% of the total anthropogenic methane emissions in the United States. The boost of natural gas production in U.S. in recent years poses a potential concern of increased methane emissions from natural gas production and distribution. The Emission Database for Global Atmospheric Research (Edgar) v4.2 and the EPA Greenhouse Gas Inventory (GHGI) are currently the most commonly used methane emission inventories. However, recent studies suggested that both Edgar v4.2 and the EPA GHGI largely underestimated the methane emission from natural gas production and distribution in U.S. constrained by both ground and satellite measurements. In this work, we built a gridded (0.1° Latitude ×0.1° Longitude) methane emission inventory of natural gas production and distribution over the contiguous U.S. using emission factors measured by our mobile lab in the Marcellus Shale, the Denver-Julesburg Basin, and the Uintah Basin, and emission factors reported from other recent field studies for other natural gas production regions. The activity data (well location and count) are mostly obtained from the Drillinginfo, the EPA Greenhouse Gas Reporting Program (GHGRP) and the U.S. Energy Information Administration (EIA). Results show that the methane emission from natural gas production and distribution estimated by our inventory is about 20% higher than the EPA GHGI, and in some major natural gas production regions, methane emissions estimated by the EPA GHGI are significantly lower than our inventory. For example, in the Marcellus Shale, our estimated annual methane emission in 2015 is 600 Gg higher than the EPA GHGI. We also ran the GEOS-Chem methane simulation to estimate the methane concentration in the atmosphere with our built inventory, the EPA GHGI and the Edgar v4.2 over the nested North American Domain. These simulation results showed differences in some major gas production regions. The simulated methane concentrations will be compared with the GOSAT satellite data to explore whether our built inventory could potentially improve the prediction of regional methane concentrations in the atmosphere.

Methane and Trichloroethylene Degradation by Methylosinus trichosporium OB3b Expressing Particulate Methane Monooxygenase

PubMed Central

Lontoh, Sonny; Semrau, Jeremy D.

1998-01-01

Whole-cell assays of methane and trichloroethylene (TCE) consumption have been performed on Methylosinus trichosporium OB3b expressing particulate methane monooxygenase (pMMO). From these assays it is apparent that varying the growth concentration of copper causes a change in the kinetics of methane and TCE degradation. For M. trichosporium OB3b, increasing the copper growth concentration from 2.5 to 20 μM caused the maximal degradation rate of methane (Vmax) to decrease from 300 to 82 nmol of methane/min/mg of protein. The methane concentration at half the maximal degradation rate (Ks) also decreased from 62 to 8.3 μM. The pseudo-first-order rate constant for methane, Vmax/Ks, doubled from 4.9 × 10−3 to 9.9 × 10−3 liters/min/mg of protein, however, as the growth concentration of copper increased from 2.5 to 20 μM. TCE degradation by M. trichosporium OB3b was also examined with varying copper and formate concentrations. M. trichosporium OB3b grown with 2.5 μM copper was unable to degrade TCE in both the absence and presence of an exogenous source of reducing equivalents in the form of formate. Cells grown with 20 μM copper, however, were able to degrade TCE regardless of whether formate was provided. Without formate the Vmax for TCE was 2.5 nmol/min/mg of protein, while providing formate increased the Vmax to 4.1 nmol/min/mg of protein. The affinity for TCE also increased with increasing copper, as seen by a change in Ks from 36 to 7.9 μM. Vmax/Ks for TCE degradation by pMMO also increased from 6.9 × 10−5 to 5.2 × 10−4 liters/min/mg of protein with the addition of formate. From these whole-cell studies it is apparent that the amount of copper available is critical in determining the oxidation of substrates in methanotrophs that are expressing only pMMO. PMID:16349516

Reduced Equations for Calculating the Combustion Rates of Jet-A and Methane Fuel

NASA Technical Reports Server (NTRS)

Molnar, Melissa; Marek, C. John

2003-01-01

Simplified kinetic schemes for Jet-A and methane fuels were developed to be used in numerical combustion codes, such as the National Combustor Code (NCC) that is being developed at Glenn. These kinetic schemes presented here result in a correlation that gives the chemical kinetic time as a function of initial overall cell fuel/air ratio, pressure, and temperature. The correlations would then be used with the turbulent mixing times to determine the limiting properties and progress of the reaction. A similar correlation was also developed using data from NASA's Chemical Equilibrium Applications (CEA) code to determine the equilibrium concentration of carbon monoxide as a function of fuel air ratio, pressure, and temperature. The NASA Glenn GLSENS kinetics code calculates the reaction rates and rate constants for each species in a kinetic scheme for finite kinetic rates. These reaction rates and the values obtained from the equilibrium correlations were then used to calculate the necessary chemical kinetic times. Chemical kinetic time equations for fuel, carbon monoxide, and NOx were obtained for both Jet-A fuel and methane.

Photocatalytic degradation of lignin on synthesized Ag-AgCl/ZnO nanorods under solar light and preliminary trials for methane fermentation.

PubMed

Li, Huifang; Lei, Zhongfang; Liu, Chunguang; Zhang, Zhenya; Lu, Baowang

2015-01-01

New photocatalysts, Ag-AgCl/ZnO nanorods, were successfully synthesized in this study by using microwave assisted chemical precipitation and deposition-precipitation-photoreduction methods. The optimal preparation condition was determined as pH 9 in distilled water and 40min for UV light photoreduction of Ag (i.e. Ag40-AgCl/ZnO) by degradation of methyl orange. This work investigated the feasibility of using Ag40-AgCl/ZnO to degrade lignin under natural solar light and then subsequent methane production with influencing factors like solution pH, dosage of catalyst and initial lignin concentration being considered. OH radicals were found to play the most important role in the photocatalytic process, and the new prepared catalyst possessed stable photocatalytic activity after 7 cycles' utilization. During the subsequent biogasification, the degraded lignin obtained from 120min photocatalysis yielded 184ml methane and 325ml biogas for per gram of removed total organic carbon, increased by 10.9% and 23.1%, respectively compared to the control. Copyright © 2014 Elsevier Ltd. All rights reserved.

Hercules 265 rapid response: Immediate ecosystem impacts of a natural gas blowout incident

NASA Astrophysics Data System (ADS)

Weber, Sarah C.; Peterson, Leigha; Battles, Jessica J.; Roberts, Brian J.; Peterson, Richard N.; Hollander, David J.; Chanton, Jeffrey P.; Joye, Samantha B.; Montoya, Joseph P.

2016-07-01

In late July 2013, the Hercules 265 drilling rig in the Northern Gulf of Mexico experienced a catastrophic loss of control. Large quantities of natural gas spewed into the environment for 2 days before the well self-sealed through down-hole collapse below the seafloor. Ecosystem Impacts of Oil and Gas Inputs to the Gulf (ECOGIG) and collaborating Gulf of Mexico Research Initiative (GoMRI) consortia mounted a rapid response cruise to characterize the waters around the Hercules 265 rig, beginning just 4 days after the blowout. Our analysis showed an immediate microbial response to the elevated concentrations of methane in the water column, as evidenced by the drawdown of oxygen to hypoxic conditions, the incorporation of methane-derived carbon into particles, and measurable rates of methane-assimilation and nitrogen-fixation. Additionally, radium isotope measurements allowed us to constrain the timescale of bottom water exposure to the influence of the rig. A second sampling by the Center for Integrated Modeling and Analysis of Gulf Ecosystems (C-IMAGE) consortium indicated that the ecosystem had returned to near pre-blowout conditions within one month.

Simultaneous chemical oxygen demand removal, methane production and heavy metal precipitation in the biological treatment of landfill leachate using acid mine drainage as sulfate resource.

PubMed

Li, Yu-Long; Wang, Jin; Yue, Zheng-Bo; Tao, Wei; Yang, Hai-Bin; Zhou, Yue-Fei; Chen, Tian-Hu

2017-07-01

Biological treatment played an important role in the treatment of landfill leachate. In the current study, acid mine drainage (AMD) was used as a source of sulfate to strengthen the anaerobic treatment of landfill leachate. Effects of chemical oxygen demand (COD) and SO 4 2- mass concentration ratio on the decomposition of organic matter, methane production and sulfate reduction were investigated and the microbial community was analyzed using the high throughout methods. Results showed that high removal efficiency of COD, methane production and heavy metal removal was achieved when the initial COD/SO 4 2- ratio (based on mass) was set at 3.0. The relative abundance of anaerobic hydrogen-producing bacteria (Candidatus Cloacamonas) in the experimental group with the addition of AMD was significantly increased compared to the control. Abundance of hydrogenotrophic methanogens of Methanosarcina and Methanomassiliicoccus was increased. Results confirmed that AMD could be used as sulfate resource to strengthen the biological treatment of landfill leachate. Copyright © 2017 The Society for Biotechnology, Japan. Published by Elsevier B.V. All rights reserved.

Marker Exchange Mutagenesis of mxaF, Encoding the Large Subunit of the Mxa Methanol Dehydrogenase, in Methylosinus trichosporium OB3b

PubMed Central

Farhan Ul Haque, Muhammad; Gu, Wenyu; DiSpirito, Alan A.

2015-01-01

Methanotrophs have remarkable redundancy in multiple steps of the central pathway of methane oxidation to carbon dioxide. For example, it has been known for over 30 years that two forms of methane monooxygenase, responsible for oxidizing methane to methanol, exist in methanotrophs, i.e., soluble methane monooxygenase (sMMO) and particulate methane monooxygenase (pMMO), and that expression of these two forms is controlled by the availability of copper. Specifically, sMMO expression occurs in the absence of copper, while pMMO expression increases with increasing copper concentrations. More recently, it was discovered that multiple forms of methanol dehydrogenase (MeDH), Mxa MeDH and Xox MeDH, also exist in methanotrophs and that the expression of these alternative forms is regulated by the availability of cerium. That is, expression of Xox MeDH increases in the presence of cerium, while Mxa MeDH expression decreases in the presence of cerium. As it had been earlier concluded that pMMO and Mxa MeDH form a supercomplex in which electrons from Mxa MeDH are back donated to pMMO to drive the initial oxidation of methane, we speculated that Mxa MeDH could be rendered inactive through marker-exchange mutagenesis but growth on methane could still be possible if cerium was added to increase the expression of Xox MeDH under sMMO-expressing conditions. Here we report that mxaF, encoding the large subunit of Mxa MeDH, could indeed be knocked out in Methylosinus trichosporium OB3b, yet growth on methane was still possible, so long as cerium was added. Interestingly, growth of this mutant occurred in both the presence and the absence of copper, suggesting that Xox MeDH can replace Mxa MeDH regardless of the form of MMO expressed. PMID:26712545

Characteristics of coal mine ventilation air flows.

PubMed

Su, Shi; Chen, Hongwei; Teakle, Philip; Xue, Sheng

2008-01-01

Coal mine methane (CMM) is not only a greenhouse gas but also a wasted energy resource if not utilised. Underground coal mining is by far the most important source of fugitive methane emissions, and approximately 70% of all coal mining related methane is emitted to the atmosphere through mine ventilation air. Therefore, research and development on mine methane mitigation and utilisation now focuses on methane emitted from underground coal mines, in particular ventilation air methane (VAM) capture and utilisation. To date, most work has focused on the oxidation of very low concentration methane. These processes may be classified based on their combustion kinetic mechanisms into thermal oxidation and catalytic oxidation. VAM mitigation/utilisation technologies are generally divided into two basic categories: ancillary uses and principal uses. However, it is possible that the characteristics of ventilation air flows, for example the variations in methane concentration and the presence of certain compounds, which have not been reported so far, could make some potential VAM mitigation and utilisation technologies unfeasible if they cannot cope with the characteristics of mine site ventilation air flows. Therefore, it is important to understand the characteristics of mine ventilation air flows. Moreover, dust, hydrogen sulphide, sulphur dioxide, and other possible compounds emitted through mine ventilation air into the atmosphere are also pollutants. Therefore, this paper presents mine-site experimental results on the characteristics of mine ventilation air flows, including methane concentration and its variations, dust loadings, particle size, mineral matter of the dust, and other compounds in the ventilation air flows. The paper also discusses possible correlations between ventilation air characteristics and underground mining activities.

2015-16 ENSO Drove Tropical Soil Moisture Dynamics and Methane Fluxes

NASA Astrophysics Data System (ADS)

Aronson, E. L.; Dierick, D.; Botthoff, J.; Swanson, A. C.; Johnson, R. F.; Allen, M. F.

2017-12-01

The El Niño/Southern Oscillation Event (ENSO) cycle drives large-scale climatic trends globally. Within the new world tropics, El Niño brings dryer weather than the counterpart La Niña. Atmospheric methane growth rates have shown extreme variability over the past three decades. One proposed driver is the proportion of tropical land surface saturated, affecting methane production or consumption. We measured methane flux bimonthly through the transition of 2015-16 ENSO. The date of measurement, across El Niño and La Niña within the typical "rainy" and "dry" seasons, to be the most significant driver of methane flux. Soil moisture varied across this time period, and regulated methane flux. During the strong El Niño, extreme dry soil conditions occurred in a typical "rainy" season month reducing soil moisture. Wetter than usual soil conditions appeared during the "rainy" season month of the moderate La Niña. The dry El Niño soils corresponded to greater methane consumption by tropical forest soils, and a reduced local atmospheric column methane concentration. Conversely, the wet La Niña soils had lower methane consumption and higher local atmospheric column methane concentrations. The ENSO cycle is a strong driver of tropical terrestrial and wetland soil moisture conditions, and can regulate global atmospheric methane dynamics.

Baseline assessment of groundwater quality in Wayne County, Pennsylvania, 2014

USGS Publications Warehouse

Senior, Lisa A.; Cravotta, III, Charles A.; Sloto, Ronald A.

2016-06-30

The Devonian-age Marcellus Shale and the Ordovician-age Utica Shale, geologic formations which have potential for natural gas development, underlie Wayne County and neighboring counties in northeastern Pennsylvania. In 2014, the U.S. Geological Survey, in cooperation with the Wayne Conservation District, conducted a study to assess baseline shallow groundwater quality in bedrock aquifers in Wayne County prior to potential extensive shale-gas development. The 2014 study expanded on previous, more limited studies that included sampling of groundwater from 2 wells in 2011 and 32 wells in 2013 in Wayne County. Eighty-nine water wells were sampled in summer 2014 to provide data on the presence of methane and other aspects of existing groundwater quality throughout the county, including concentrations of inorganic constituents commonly present at low levels in shallow, fresh groundwater but elevated in brines associated with fluids extracted from geologic formations during shale-gas development. Depths of sampled wells ranged from 85 to 1,300 feet (ft) with a median of 291 ft. All of the groundwater samples collected in 2014 were analyzed for bacteria, major ions, nutrients, selected inorganic trace constituents (including metals and other elements), radon-222, gross alpha- and gross beta-particle activity, selected man-made organic compounds (including volatile organic compounds and glycols), dissolved gases (methane, ethane, and propane), and, if sufficient methane was present, the isotopic composition of methane.Results of the 2014 study show that groundwater quality generally met most drinking-water standards, but some well-water samples had one or more constituents or properties, including arsenic, iron, pH, bacteria, and radon-222, that exceeded primary or secondary maximum contaminant levels (MCLs). Arsenic concentrations were higher than the MCL of 10 micrograms per liter (µg/L) in 4 of 89 samples (4.5 percent) with concentrations as high as 20 µg/L; arsenic concentrations were higher than the Health Advisory level of 2 µg/L in 27 of 89 samples (30 percent). Total iron concentrations exceeded the secondary maximum contaminant level (SMCL) of 300 µg/L in 9 of 89 samples (10 percent). The pH ranged from 5.4 to 9.3 and did not meet the SMCL range of greater than 6.5 to less than 8.5 in 27 samples (30 percent); 22 samples had pH values less than 6.5, and 5 samples had pH values greater than 8.5. Total coliform bacteria were detected in 22 of 89 samples (25 percent); Escherichia coli were detected in only 2 of those 22 samples. Radon-222 activities ranged from 25 to 7,400 picocuries per liter (pCi/L), with a median of 2,120 pCi/L, and exceeded the proposed drinking-water standard of 300 pCi/L in 86 of 89 samples (97 percent); radon-222 activities were higher than the alternative proposed standard of 4,000 pCi/L in 12 of 89 samples (13.5 percent).Water from 8 of the 89 wells (9 percent) had concentrations of methane greater than the reporting level of 0.24 milligrams per liter (mg/L) with the detectable methane concentrations ranging from 0.74 to 9.6 mg/L. Of 16 replicate samples submitted to another laboratory with a lower reporting level of 0.0002 mg/L, 15 samples had detectable methane concentrations that ranged from 0.0011 to 9.7 mg/L. Of these 15 samples, low levels of ethane (0.00032 to 0.0017 mg/L) were detected in 6 of 7 samples with methane concentrations greater than 0.75 mg/L. The isotopic composition of methane in 6 of 8 samples with sufficient dissolved methane (about 1 mg/L) for isotopic analysis is consistent with a predominantly thermogenic methane source (sample carbon isotopic ratio δ13CCH4 values ranging from -56.36 to -45.97 parts per thousand (‰) and hydrogen isotopic ratio δDCH4 values ranging from -233.1 to -141.1 ‰). However, the low levels of ethane relative to methane indicate that the methane may be of microbial origin and subsequently underwent oxidation. Isotopic compositions indicated a possibly mixed thermogenic and microbial source (carbon dioxide reduction process) for the methane in 1 of the 8 samples (δ13CCH4 of -63.72 and δDCH4 of -192.3 ‰) and potential oxidation of microbial and (or) thermogenic methane in the remaining sample (δ13CCH4 of -46.56 and δDCH4 of -79.7 ‰).Groundwater samples with relatively elevated methane concentrations (near or greater than 1 mg/L) had a chemical composition that differed in some respects (pH, selected major ions, and inorganic trace constituents) from groundwater with relatively low methane concentrations (less than 0.75 mg/L). The seven well-water samples with the highest methane concentrations (from about 1 to 9.6 mg/L) also had among the highest pH values (8.1 to 9.3, respectively) and the highest concentrations of sodium, lithium, boron, fluoride, arsenic, and bromide. Relatively elevated concentrations of some other constituents, such as barium, strontium, and chloride, commonly were present in, but not limited to, those well-water samples with elevated methane.Groundwater samples with the highest methane concentrations had chloride/bromide ratios that indicate mixing with a small amount of brine (0.02 percent or less, by volume) similar in composition to that reported for gas and oil well brines in Pennsylvania. Most other samples with low methane concentrations (less than about 1 mg/L) had chloride/bromide ratios that indicate predominantly man-made sources of chloride, such as road salt, septic systems, and (or) animal waste. Although naturally occurring brines may originate from deeper parts of the aquifer system, the man-made sources are likely to affect shallow groundwater.Geochemical modeling showed that the water chemistry of samples with elevated pH, sodium, lithium, bromide, and alkalinity could result from dissolution of calcite (calcium carbonate) combined with cation exchange and mixing with a small amount of brine. Through cation exchange reactions (which are equivalent to processes in a water softener) calcium ions released by calcite dissolution are exchanged for sodium ions on clay minerals. The spatial distribution of groundwater compositions generally shows that (1) relatively dilute, slightly acidic, oxygenated, calcium-carbonate type waters tend to occur in the uplands along the western border of Wayne County; (2) waters of near neutral pH with the highest amounts of hardness (calcium and magnesium) generally occur in areas of intermediate altitudes; and (3) waters with pH values greater than 8, low oxygen concentrations, and the highest arsenic, sodium, lithium, bromide, and methane concentrations can occur in deep wells in uplands but most frequently occur in stream valleys, especially at low elevations (less than about 1,200 ft above North American Vertical Datum of 1988) where groundwater may be discharging regionally, such as to the Delaware River. Thus, the baseline assessment of groundwater quality in Wayne County prior to gas-well development shows that shallow (less than about 1,000 ft deep) groundwater is generally of good quality, but methane and some constituents present in high concentrations in brine (and produced waters from gas and oil wells) may be present at low to moderate concentrations in some parts of Wayne County.

Impacts of an ethanol-blended fuel release on groundwater and fate of produced methane: Simulation of field observations

NASA Astrophysics Data System (ADS)

Rasa, Ehsan; Bekins, Barbara A.; Mackay, Douglas M.; de Sieyes, Nicholas R.; Wilson, John T.; Feris, Kevin P.; Wood, Isaac A.; Scow, Kate M.

2013-08-01

In a field experiment at Vandenberg Air Force Base (VAFB) designed to mimic the impact of a small-volume release of E10 (10% ethanol and 90% conventional gasoline), two plumes were created by injecting extracted groundwater spiked with benzene, toluene, and o-xylene, abbreviated BToX (no-ethanol lane) and BToX plus ethanol (with-ethanol lane) for 283 days. We developed a reactive transport model to understand processes controlling the fate of ethanol and BToX. The model was calibrated to the extensive field data set and accounted for concentrations of sulfate, iron, acetate, and methane along with iron-reducing bacteria, sulfate-reducing bacteria, fermentative bacteria, and methanogenic archaea. The benzene plume was about 4.5 times longer in the with-ethanol lane than in the no-ethanol lane. Matching this different behavior in the two lanes required inhibiting benzene degradation in the presence of ethanol. Inclusion of iron reduction with negligible growth of iron reducers was required to reproduce the observed constant degradation rate of benzene. Modeling suggested that vertical dispersion and diffusion of sulfate from an adjacent aquitard were important sources of sulfate in the aquifer. Matching of methane data required incorporating initial fermentation of ethanol to acetate, methane loss by outgassing, and methane oxidation coupled to sulfate and iron reduction. Simulation of microbial growth using dual Monod kinetics, and including inhibition by more favorable electron acceptors, generally resulted in reasonable yields for microbial growth of 0.01-0.05.

Impacts of an ethanol-blended fuel release on groundwater and fate of produced methane: simulation of field observations

USGS Publications Warehouse

Rasa, Ehsan; Bekins, Barbara A.; Mackay, Douglas M.; de Sieyes, Nicholas R.; Wilson, John T.; Feris, Kevin P.; Wood, Isaac A.; Scow, Kate M.

2013-01-01

In a field experiment at Vandenberg Air Force Base (VAFB) designed to mimic the impact of a small-volume release of E10 (10% ethanol and 90% conventional gasoline), two plumes were created by injecting extracted groundwater spiked with benzene, toluene, and o-xylene, abbreviated BToX (No-Ethanol Lane) and BToX plus ethanol (With-Ethanol Lane) for 283 days. We developed a reactive transport model to understand processes controlling the fate of ethanol and BToX. The model was calibrated to the extensive field dataset and accounted for concentrations of sulfate, iron, acetate, and methane along with iron-reducing bacteria, sulfate-reducing bacteria, fermentative bacteria, and methanogenic archaea. The benzene plume was about 4.5 times longer in the With-Ethanol Lane than in the No-Ethanol Lane. Matching this different behavior in the two lanes required inhibiting benzene degradation in the presence of ethanol. Inclusion of iron reduction with negligible growth of iron-reducers was required to reproduce the observed constant degradation rate of benzene. Modeling suggested that vertical dispersion and diffusion of sulfate from an adjacent aquitard were important sources of sulfate in the aquifer. Matching of methane data required incorporating initial fermentation of ethanol to acetate, methane loss by outgassing, and methane oxidation coupled to sulfate and iron reduction. Simulation of microbial growth using dual Monod kinetics, and including inhibition by more favorable electron acceptors, generally resulted in reasonable yields for microbial growth of 0.01-0.05.

Greenhouse Trace Gases in Deadwood

NASA Astrophysics Data System (ADS)

Covey, Kristofer; Bueno de Mesquita, Cliff; Oberle, Brad; Maynard, Dan; Bettigole, Charles; Crowther, Thomas; Duguid, Marlyse; Steven, Blaire; Zanne, Amy; Lapin, Marc; Ashton, Mark; Oliver, Chad; Lee, Xuhui; Bradford, Mark

2016-04-01

Deadwood, long recognized as playing an important role in carbon cycling in forest ecosystems, is more recently drawing attention for its potential role in the cycling of other greenhouse trace gases. We report data from four independent studies measuring internal gas concentrations in deadwood in in three Quercus dominated upland forest systems in the Northeastern and Central United States. Mean methane concentrations in deadwood were 23 times atmospheric levels, indicating a lower bound, mean radial wood surface area flux of ~6 x 10-4 μmol CH4 m-2 s-1. Site, decay class, diameter, and species were all highly significant predictors of methane abundance in deadwood, and log diameter and decay stage interacted as important controls limiting methane concentrations in the smallest and most decayed logs. Nitrous oxide concentrations were negatively correlated with methane and on average ~25% lower than ambient, indicating net consumption of nitrous oxide. These data suggest nonstructural carbohydrates fuel archaeal methanogens and confirm the potential for widespread in situ methanogenesis in both living and deadwood. Applying this understanding to estimate methane emissions from microbial activity in living trees implies a potential global flux of 65.6±12.0 Tg CH4 yr-1, more than 20 times greater than currently considered.

Bioconversion of methane to lactate by an obligate methanotrophic bacterium

DOE PAGES

Henard, Calvin A.; Smith, Holly; Dowe, Nancy; ...

2016-02-23

Methane is the second most abundant greenhouse gas (GHG), with nearly 60% of emissions derived from anthropogenic sources. Microbial conversion of methane to fuels and value-added chemicals offers a means to reduce GHG emissions, while also valorizing this otherwise squandered high-volume, high-energy gas. However, to date, advances in methane biocatalysis have been constrained by the low-productivity and limited genetic tractability of natural methane-consuming microbes. Here, leveraging recent identification of a novel, tractable methanotrophic bacterium, Methylomicrobium buryatense, we demonstrate microbial biocatalysis of methane to lactate, an industrial platform chemical. Heterologous overexpression of a Lactobacillus helveticus L-lactate dehydrogenase in M. buryatense resultedmore » in an initial titer of 0.06 g lactate/L from methane. Cultivation in a 5 L continuously stirred tank bioreactor enabled production of 0.8 g lactate/L, representing a 13-fold improvement compared to the initial titer. The yields (0.05 g lactate/g methane) and productivity (0.008 g lactate/L/h) indicate the need and opportunity for future strain improvement. Additionally, real-time analysis of methane utilization implicated gas-to-liquid transfer and/or microbial methane consumption as process limitations. This work opens the door to develop an array of methanotrophic bacterial strain-engineering strategies currently employed for biocatalytic sugar upgrading to “green” chemicals and fuels.« less

Bioconversion of methane to lactate by an obligate methanotrophic bacterium

DOE Office of Scientific and Technical Information (OSTI.GOV)

Henard, Calvin A.; Smith, Holly; Dowe, Nancy

Methane is the second most abundant greenhouse gas (GHG), with nearly 60% of emissions derived from anthropogenic sources. Microbial conversion of methane to fuels and value-added chemicals offers a means to reduce GHG emissions, while also valorizing this otherwise squandered high-volume, high-energy gas. However, to date, advances in methane biocatalysis have been constrained by the low-productivity and limited genetic tractability of natural methane-consuming microbes. Here, leveraging recent identification of a novel, tractable methanotrophic bacterium, Methylomicrobium buryatense, we demonstrate microbial biocatalysis of methane to lactate, an industrial platform chemical. Heterologous overexpression of a Lactobacillus helveticus L-lactate dehydrogenase in M. buryatense resultedmore » in an initial titer of 0.06 g lactate/L from methane. Cultivation in a 5 L continuously stirred tank bioreactor enabled production of 0.8 g lactate/L, representing a 13-fold improvement compared to the initial titer. The yields (0.05 g lactate/g methane) and productivity (0.008 g lactate/L/h) indicate the need and opportunity for future strain improvement. Additionally, real-time analysis of methane utilization implicated gas-to-liquid transfer and/or microbial methane consumption as process limitations. This work opens the door to develop an array of methanotrophic bacterial strain-engineering strategies currently employed for biocatalytic sugar upgrading to “green” chemicals and fuels.« less

Bioconversion of methane to lactate by an obligate methanotrophic bacterium

PubMed Central

Henard, Calvin A.; Smith, Holly; Dowe, Nancy; Kalyuzhnaya, Marina G.; Pienkos, Philip T.; Guarnieri, Michael T.

2016-01-01

Methane is the second most abundant greenhouse gas (GHG), with nearly 60% of emissions derived from anthropogenic sources. Microbial conversion of methane to fuels and value-added chemicals offers a means to reduce GHG emissions, while also valorizing this otherwise squandered high-volume, high-energy gas. However, to date, advances in methane biocatalysis have been constrained by the low-productivity and limited genetic tractability of natural methane-consuming microbes. Here, leveraging recent identification of a novel, tractable methanotrophic bacterium, Methylomicrobium buryatense, we demonstrate microbial biocatalysis of methane to lactate, an industrial platform chemical. Heterologous overexpression of a Lactobacillus helveticus L-lactate dehydrogenase in M. buryatense resulted in an initial titer of 0.06 g lactate/L from methane. Cultivation in a 5 L continuously stirred tank bioreactor enabled production of 0.8 g lactate/L, representing a 13-fold improvement compared to the initial titer. The yields (0.05 g lactate/g methane) and productivity (0.008 g lactate/L/h) indicate the need and opportunity for future strain improvement. Additionally, real-time analysis of methane utilization implicated gas-to-liquid transfer and/or microbial methane consumption as process limitations. This work opens the door to develop an array of methanotrophic bacterial strain-engineering strategies currently employed for biocatalytic sugar upgrading to “green” chemicals and fuels. PMID:26902345

Geochemical indicators of the origins and evolution of methane in groundwater: Gippsland Basin, Australia.

PubMed

Currell, Matthew; Banfield, Dominic; Cartwright, Ian; Cendón, Dioni I

2017-05-01

Recent expansion of shale and coal seam gas production worldwide has increased the need for geochemical studies in aquifers near gas deposits, to determine processes impacting groundwater quality and better understand the origins and behavior of dissolved hydrocarbons. We determined dissolved methane concentrations (n = 36) and δ 13 C and δ 2 H values (n = 31) in methane and groundwater from the 46,000-km 2 Gippsland Basin in southeast Australia. The basin contains important water supply aquifers and is a potential target for future unconventional gas development. Dissolved methane concentrations ranged from 0.0035 to 30 mg/L (median = 8.3 mg/L) and were significantly higher in the deep Lower Tertiary Aquifer (median = 19 mg/L) than the shallower Upper Tertiary Aquifer (median = 3.45 mg/L). Groundwater δ 13 C DIC values ranged from -26.4 to -0.4 ‰ and were generally higher in groundwater with high methane concentrations (mean δ 13 C DIC  = -9.5 ‰ for samples with >3 mg/L CH 4 vs. -16.2 ‰ in all others), which is consistent with bacterial methanogenesis. Methane had δ 13 C CH4 values of -97.5 to -31.8 ‰ and δ 2 H CH4 values of -391 to -204 ‰ that were also consistent with bacterial methane, excluding one site with δ 13 C CH4 values of -31.8 to -37.9 ‰, where methane may have been thermogenic. Methane from different regions and aquifers had distinctive stable isotope values, indicating differences in the substrate and/or methanogenesis mechanism. Methane in the Upper Tertiary Aquifer in Central Gippsland had lower δ 13 C CH4 (-83.7 to -97.5 ‰) and δ 2 H CH4 (-236 to -391 ‰) values than in the deeper Lower Tertiary Aquifer (δ 13 C CH4  = -45.8 to -66.2 ‰ and δ 2 H CH4  = -204 to -311 ‰). The particularly low δ 13 C CH4 values in the former group may indicate methanogenesis at least partly through carbonate reduction. In deeper groundwater, isotopic values were more consistent with acetate fermentation. Not all methane at a given depth and location is interpreted as being necessarily produced in situ. We propose that high dissolved sulphate concentrations in combination with high methane concentrations can indicate gas resulting from contamination and/or rapid migration as opposed to in situ bacterial production or long-term migration. Isotopes of methane and dissolved inorganic carbon (DIC) serve as further lines of evidence to distinguish methane sources. The study demonstrates the value of isotopic characterisation of groundwater including dissolved gases in basins containing hydrocarbons.

The Australian methane budget: Interpreting surface and train-borne measurements using a chemistry transport model

NASA Astrophysics Data System (ADS)

Fraser, Annemarie; Chan Miller, Christopher; Palmer, Paul I.; Deutscher, Nicholas M.; Jones, Nicholas B.; Griffith, David W. T.

2011-10-01

We investigate the Australian methane budget from 2005-2008 using the GEOS-Chem 3D chemistry transport model, focusing on the relative contribution of emissions from different sectors and the influence of long-range transport. To evaluate the model, we use in situ surface measurements of methane, methane dry air column average (XCH4) from ground-based Fourier transform spectrometers (FTSs), and train-borne surface concentration measurements from an in situ FTS along the north-south continental transect. We use gravity anomaly data from Gravity Recovery and Climate Experiment to describe the spatial and temporal distribution of wetland emissions and scale it to a prior emission estimate, which better describes observed atmospheric methane variability at tropical latitudes. The clean air sites of Cape Ferguson and Cape Grim are the least affected by local emissions, while Wollongong, located in the populated southeast with regional coal mining, samples the most locally polluted air masses (2.5% of the total air mass versus <1% at other sites). Averaged annually, the largest single source above background of methane at Darwin is long-range transport, mainly from Southeast Asia, accounting for ˜25% of the change in surface concentration above background. At Cape Ferguson and Cape Grim, emissions from ruminant animals are the largest source of methane above background, at approximately 20% and 30%, respectively, of the surface concentration. At Wollongong, emissions from coal mining are the largest source above background representing 60% of the surface concentration. The train data provide an effective way of observing transitions between urban, desert, and tropical landscapes.

Biogasification of sorghum

DOE Office of Scientific and Technical Information (OSTI.GOV)

Biljetina, R.; Srivastava, V.J.; Isaacson, H.R.

1987-01-01

The Institute of Gas Technology has been operating a 1200-gallon, anaerobic solids-concentrating digester at the Walt Disney World Resort Complex in Lake Buena Vista, Florida. This digester development work is part of a larger effort sponsored by the Gas Research Institute to provide an effective community waste treatment and energy recovery concept for smaller communities. As a result, an economically attractive, water hyacinth-based wastewater treatment system was developed that includes the digestion of water hyacinth and sludge to methane. A further extension of the community waste treatment concept is to include agricultural wastes in the energy recovery scheme. Therefore, duringmore » 1986 a test program was initiated to obtain data on the digestion of sorghum in the solids concentrating digester. Performance data was collected at both mesophilic and thermophilic operating conditions at total organic loading rates of 0.25 and 0.5 pounds per cubic foot of digester volume per day, respectively. Excellent methane yields were obtained during twelve months of stable and uninterrupted operation. This paper summarizes the performance data obtained on sorghum in this digester. 7 refs., 6 figs., 6 tabs.« less

Abundance and δ13C values of fatty acids in lacustrine surface sediments: Relationships with in-lake methane concentrations

NASA Astrophysics Data System (ADS)

Stötter, Tabea; Bastviken, David; Bodelier, Paul L. E.; van Hardenbroek, Maarten; Rinta, Päivi; Schilder, Jos; Schubert, Carsten J.; Heiri, Oliver

2018-07-01

Proxy-indicators in lake sediments provide the only approach by which the dynamics of in-lake methane cycling can be examined on multi-decadal to centennial time scales. This information is necessary to constrain how lacustrine methane production, oxidation and emissions are expected to respond to global change drivers. Several of the available proxies for reconstructing methane cycle changes of lakes rely on interpreting past changes in the abundance or relevance of methane oxidizing bacteria (MOB), either directly (e.g. via analysis of bacterial lipids) or indirectly (e.g. via reconstructions of the past relevance of MOB in invertebrate diet). However, only limited information is available about the extent to which, at the ecosystem scale, variations in abundance and availability of MOB reflect past changes in in-lake methane concentrations. We present a study examining the abundances of fatty acids (FAs), particularly of 13C-depleted FAs known to be produced by MOB, relative to methane concentrations in 29 small European lakes. 39 surface sediment samples were obtained from these lakes and FA abundances were compared with methane concentrations measured at the lake surface, 10 cm above the sediments and 10 cm within the sediments. Three of the FAs in the surface sediment samples, C16:1ω7c, C16:1ω5c/t, and C18:1ω7c were characterized by lower δ13C values than the remaining FAs. We show that abundances of these FAs, relative to other short-chain FAs produced in lake ecosystems, are related with sedimentary MOB concentrations assessed by quantitative polymerase chain reaction (qPCR). We observed positive relationships between methane concentrations and relative abundances of C16:1ω7c, C16:1ω5c/t, and C18:1ω7c and the sum of these FAs. For the full dataset these relationships were relatively weak (Spearman's rank correlation (rs) of 0.34-0.43) and not significant if corrected for multiple testing. However, noticeably stronger and statistically significant relationships were observed when sediments from near-shore and deep-water oxic environments (rs = 0.57 to 0.62) and those from anoxic deep-water environment (rs = 0.55 to 0.65) were examined separately. Our results confirm that robust relationships exist between in-lake CH4 concentrations and 13C-depleted groups of FAs in the examined sediments, agreeing with earlier suggestions that the availability of MOB-derived, 13C-depleted organic matter for aquatic invertebrates increases with increasing methane concentrations. However, we also show that these relationships are complex, with different relationships observed for oxic and anoxic sediments and highest values measured in sediments deposited in oxic environments overlain with relatively methane-rich water. Furthermore, although all three 13C-depleted FA groups identified in our survey are known to be produced by MOB, they also receive contributions by other organism groups, and this will have influenced their distribution in our dataset.

Atmospheric methane at Cape Meares - Analysis of a high-resolution data base and its environmental implications

NASA Technical Reports Server (NTRS)

Khalil, M. A. K.; Rasmussen, R. A.; Moraes, F.

1993-01-01

Between 1979 and 1992 we took some 120,000 measurements of atmospheric methane at Cape Meares on the Oregon coast. The site is representative of methane concentrations in the northern latitudes (from 30 deg N to 90 deg N). The average concentration during the experiment was 1698 parts per billion by volume (ppbv). Methane concentration increased by 190 ppbv (or 11.9 percent) during the 13-year span of the experiment. The rate of increase was about 20 +/- 4 ppbv/yr in the first 2 yr and 10 +/- 2 ppbv/yr in the last 2 yr of the experiment, suggesting a substantial decline in the trend at northern middle and high latitudes. Prominent seasonal cycles were observed. During the year, the concentration stays more or less constant until May and then starts falling, reaching lowest levels in July and August, then rises rapidly to nearly maximum concentrations in October. Interannual variations with small amplitudes of 2-3 ppbv occur with periods of 1.4 and 6.5 yr.

Methane Fingerprinting: Isotopic Methane and Ethane-to-Methane Ratio Analysis Using a Cavity Ring-Down Spectrometer

NASA Astrophysics Data System (ADS)

Saad, Nabil; Fleck, Derek; Hoffnagle, John

2016-04-01

Emissions of Natural gas, and methane (CH4) specifically, have come under increased scrutiny by virtue of methane's 28-36x greenhouse warming potential compared to carbon dioxide (CO2) while accounting for 10% of the total greenhouse gas emissions in the US. Large uncontrolled leaks, such as the recent Aliso Canyon leak, originating from uncapped wells, coal mines and storage facilities have increased the total global contribution of methane missions even further. Determining the specific fingerprint of methane sources, by quantifying δ13C values and C2:C1 ratios, provides the means to understand methane producing processes and allows for sources of methane to be mapped and classified through these processes; i.e. biogenic vs. thermogenic, wet vs dry. In this study we present a fully developed Cavity Ring-Down Spectrometer (CRDS) that precisely measures 12CH4 concentration and its 13CH4 isotope concentration, yielding δ13C measurements, C2H6 concentration, along with CO2 and H2O. This provides real-time continuous measurements without an upfront separation requirement or multiple analyses to derive the origin of the gas samples. The highly sensitive analyzer allows for measurements of scarce molecules down to sub-ppb 1-σ precision in 5 minutes of measurement: with CH4 <0.1ppb, δ13C <1‰ C2H6 <1ppb and CO2 <1ppm. To complement this work, we provide the analysis of different methane sources providing a 2-dimensional mapping of methane sources as functions of δ13C and C2:C1 ratios, which can be thought of as a modified Bernard Plot. This dual ratio mapping can be used to discriminate between naturally occurring biogenic methane sources, naturally occurring enriched thermogenic sources, and natural gas distribution sources. This also shows future promise in aiding gas and oil exploration, in distinguishing oil vs coal gases, as well as a valuable tool in the development of methane sequestration.

Exceptional summer warming leads to contrasting outcomes for methane cycling in small Arctic lakes of Greenland

NASA Astrophysics Data System (ADS)

Cadieux, Sarah B.; White, Jeffrey R.; Pratt, Lisa M.

2017-02-01

In thermally stratified lakes, the greatest annual methane emissions typically occur during thermal overturn events. In July of 2012, Greenland experienced significant warming that resulted in substantial melting of the Greenland Ice Sheet and enhanced runoff events. This unusual climate phenomenon provided an opportunity to examine the effects of short-term natural heating on lake thermal structure and methane dynamics and compare these observations with those from the following year, when temperatures were normal. Here, we focus on methane concentrations within the water column of five adjacent small lakes on the ice-free margin of southwestern Greenland under open-water and ice-covered conditions from 2012-2014. Enhanced warming of the epilimnion in the lakes under open-water conditions in 2012 led to strong thermal stability and the development of anoxic hypolimnia in each of the lakes. As a result, during open-water conditions, mean dissolved methane concentrations in the water column were significantly (p < 0.0001) greater in 2012 than in 2013. In all of the lakes, mean methane concentrations under ice-covered conditions were significantly (p < 0.0001) greater than under open-water conditions, suggesting spring overturn is currently the largest annual methane flux to the atmosphere. As the climate continues to warm, shorter ice cover durations are expected, which may reduce the winter inventory of methane and lead to a decrease in total methane flux during ice melt. Under open-water conditions, greater heat income and warming of lake surface waters will lead to increased thermal stratification and hypolimnetic anoxia, which will consequently result in increased water column inventories of methane. This stored methane will be susceptible to emissions during fall overturn, which may result in a shift in greatest annual efflux of methane from spring melt to fall overturn. The results of this study suggest that interannual variation in ground-level air temperatures may be the primary driver of changes in methane dynamics because it controls both the duration of ice cover and the strength of thermal stratification.

The occurrence of macro- and mesoscopic methane hydrate in the eastern margin of Japan Sea

NASA Astrophysics Data System (ADS)

Matsumoto, R.; Kakuwa, Y.; Tanahashi, M.; Hiruta, A.

2016-12-01

Shallow methane hydrate is known to occur in muddy sediments that were deposited in the eastern margin of Japan Sea. In such settings, the hydrate occurs just below the seabed or is exposed directly on the seabed. Its presence is quite different from the pore-filling type of hydrate typically found in sandstone of the Pacific Ocean side of the Japanese islands. This presentation focuses on categorizing the distribution of gas hydrate in Japan Sea which, until recently, has been poorly understood. Macroscopic occurrence: Numerous gas chimney structures, which are characterized by an acoustic blanking on sub-bottom profiler images, have been discovered in the eastern margin of Japan Sea. We carried out seafloor drilling at several topographic highs that showed gas chimney structures. The results confirm that, while methane hydrate does not occur in the well-stratified part of SBP images, it does occur uniquely in the gas chimney structure-bearing mounds and pockmarks. Several horizons of methane hydrate-concentrated layers are identified by our LWD data and are traceable over lateral distances of as much as a kilometer.. In another case, the methane hydrate-concentrated layers occur stratigraphically in a regular manner with methane-derived carbonate nodules. We interpret the second case as one in which methane gas was supplied by regularly repeated movements of active fault(s). Mesoscopic occurrence: Methane hydrate is classified into 5 types that are readily observable in drilled cores: granular, nodular, platy, veiny and massive. The granular type is common over shallower intervals, while platy and veiny types are more common in the deeper intervals. Nevertheless, a significant fraction of the granular type may have possibly originated from the destruction and dissociation of other types during drilling and recovery. The massive type hydrate that characterizes highly-concentrated layers transitions to other types laterally as methane hydrate becomes poorly concentrated. This study was conducted under the commission from AIST as a part of the methane hydrate research project funded by METI (the Ministry of Economy, Trade and Industry, Japan).

High-resolution passive sampling of dissolved methane in the water column of lakes in Greenland

NASA Astrophysics Data System (ADS)

Goldman, A. E.; Cadieux, S. B.; White, J. R.; Pratt, L. M.

2013-12-01

Arctic lakes are important participants in the global carbon cycle, releasing methane in a warming climate and contributing to a positive feedback to climate change. In order to yield detailed methane budgets and understand the implications of warming on methane dynamics, high-resolution profiles revealing methane behavior within the water column need to be obtained. Single day sampling using disruptive techniques has the potential to result in biases. In order to obtain high-resolution, undisturbed profiles of methane concentration and isotopic composition, this study evaluates a passive sampling method over a multi-day equilibration period. Selected for this study were two small lakes (<1km2) within a narrow valley stretching between Russells Glacier and Søndre Strømfjord in southwestern Greenland, which are part of an ongoing study of a series of seven lakes. Commercially available, 150 mL, polyethylene Passive Diffusion Bags (PDB's) were deployed in July 2013 for five days at 0.5-meter depth intervals. PDB samples were compared to samples collected with a submersible, electric pump taken immediately before PBD deployment. Preliminary CH4 concentrations and carbon isotopes for one lake were obtained in the field using a Los Gatos Research Methane Carbon Isotope Analyzer. PDB sampling and pump sampling resulted in statistically similar concentrations (R2=0.89), ranging from 0.85 to 135 uM from PDB and 0.74 to 143 uM from pump sampling. In anoxic waters of the lake, where concentrations were high enough to yield robust isotopic results on the LGR MCIA, δ13C were also similar between the two methods, yielding -73‰ from PDB and -74‰ from pump sampling. Further investigation will produce results for a second lake and methane carbon and hydrogen isotopic composition for both lakes. Preliminary results for this passive sampling method are promising. We envision the use of this technique in future studies of dissolved methane and expect that it will provide a more finely resolved vertical profile, allowing for a more complete understanding of lacustrine methane dynamics.

Can groundwater sampling techniques used in monitoring wells influence methane concentrations and isotopes?

PubMed

Rivard, Christine; Bordeleau, Geneviève; Lavoie, Denis; Lefebvre, René; Malet, Xavier

2018-03-06

Methane concentrations and isotopic composition in groundwater are the focus of a growing number of studies. However, concerns are often expressed regarding the integrity of samples, as methane is very volatile and may partially exsolve during sample lifting in the well and transfer to sampling containers. While issues concerning bottle-filling techniques have already been documented, this paper documents a comparison of methane concentration and isotopic composition obtained with three devices commonly used to retrieve water samples from dedicated observation wells. This work lies within the framework of a larger project carried out in the Saint-Édouard area (southern Québec, Canada), whose objective was to assess the risk to shallow groundwater quality related to potential shale gas exploitation. The selected sampling devices, which were tested on ten wells during three sampling campaigns, consist of an impeller pump, a bladder pump, and disposable sampling bags (HydraSleeve). The sampling bags were used both before and after pumping, to verify the appropriateness of a no-purge approach, compared to the low-flow approach involving pumping until stabilization of field physicochemical parameters. Results show that methane concentrations obtained with the selected sampling techniques are usually similar and that there is no systematic bias related to a specific technique. Nonetheless, concentrations can sometimes vary quite significantly (up to 3.5 times) for a given well and sampling event. Methane isotopic composition obtained with all sampling techniques is very similar, except in some cases where sampling bags were used before pumping (no-purge approach), in wells where multiple groundwater sources enter the borehole.

Numerical modelling of methane oxidation efficiency and coupled water-gas-heat reactive transfer in a sloping landfill cover.

PubMed

Feng, S; Ng, C W W; Leung, A K; Liu, H W

2017-10-01

Microbial aerobic methane oxidation in unsaturated landfill cover involves coupled water, gas and heat reactive transfer. The coupled process is complex and its influence on methane oxidation efficiency is not clear, especially in steep covers where spatial variations of water, gas and heat are significant. In this study, two-dimensional finite element numerical simulations were carried out to evaluate the performance of unsaturated sloping cover. The numerical model was calibrated using a set of flume model test data, and was then subsequently used for parametric study. A new method that considers transient changes of methane concentration during the estimation of the methane oxidation efficiency was proposed and compared against existing methods. It was found that a steeper cover had a lower oxidation efficiency due to enhanced downslope water flow, during which desaturation of soil promoted gas transport and hence landfill gas emission. This effect was magnified as the cover angle and landfill gas generation rate at the bottom of the cover increased. Assuming the steady-state methane concentration in a cover would result in a non-conservative overestimation of oxidation efficiency, especially when a steep cover was subjected to rainfall infiltration. By considering the transient methane concentration, the newly-modified method can give a more accurate oxidation efficiency. Copyright © 2017. Published by Elsevier Ltd.

Changes in methane emission, rumen fermentation, and methanogenic community in response to silage and dry cornstalk diets.

PubMed

Chong, Liu; Zhuping, Zhu; Tongjun, Guo; Yongming, Luo; Hongmin, Dong

2014-06-01

This study aimed to investigate the effect of silage or dry cornstalk diets on methane emission, rumen fermentation, and methanogenic community, and reveal whether the change of methanogenic compositions was related to the methane production. A total of 39 sheep were divided into four groups, fed diets of different concentrate level based on silage or dry cornstalk roughage for 40 days. It was found that, at 20% concentrate level, the sheep fed silage could suppress methanogenesis significantly in contrast with the silage diet (p < 0.05). The ruminal acetate:propionate ratio was 3.17 in the silage-fed sheep significantly lower than 3.78 in the dry cornstalk-fed sheep (p < 0.05), reflecting the effect of fermentation on methane output was related to roughage types. Furthermore, the methanogens was found to be significantly lower abundance (p < 0.05), and showed a different pattern using multivariate statistical analysis in silage-fed sheep. Compared with dry cornstalk diet, silage diet of 20% concentrate reduced methane production, decreased methanogenic abundance, and induced change of Methanobrevibacter composition at strain levels. This study showed variation of methanogenic compositions at strain level and its probable relationship with methane production, and provided microbial information to explain the low methane output when the animals were fed silage. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Concentrations and emission rates of aerial ammonia, nitrous oxide, methane, carbon dioxide, dust and endotoxin in UK broiler and layer houses.

PubMed

Wathes, C M; Holden, M R; Sneath, R W; White, R P; Phillips, V R

1997-03-01

1. A survey of the concentration and emission rates of aerial ammonia, nitrous oxide, methane, carbon dioxide, dust and endotoxin was undertaken in 4 examples each of typical UK broiler, cage and perchery houses over 24 h during winter and summer. 2. Overall the air quality within the poultry houses was unsatisfactory as judged by the dual criteria of farmer health and bird performance. 3. Mean concentrations of ammonia ranged from 12.3 to 24.2 ppm while concentrations of methane and nitrous oxide were close to ambient levels. Mass concentrations of aerial dust ranged from 2 to 10 mg/m3 and 0.3 to 1.2 mg/m3 for inspirable and respirable fractions respectively, while endotoxin concentration was typically about 0.1 microgram/m3 (inspirable fraction). 4. Emission rates of gaseous ammonia were rapid (9.2 g (NH3)/h per 500 kg live body weight) and uniform across the three types of building, while emissions of methane and nitrous oxide were slow. Rates of dust emission ranged from 0.86 to 8.24 g/h per 500 kg live body weight in the inspirable size fraction.

Oxidation of contaminative methane traces with radio-frequency discharge

NASA Technical Reports Server (NTRS)

Flamm, D. L.; Wydeven, T. L.

1976-01-01

An 11.8 MHz glow discharge was used to oxidize trace levels of methane in oxygen. The concentration of methane can be reduced by three orders of magnitude. The effects of power (0-400 W), flow rate (10-1000 cc-STP/min) and concentration (70-8000 ppm) were investigated at pressures ranging from 50 torr to almost 1 atm. No organic reaction products were detected in the treated gas stream. The process may prove useful for the removal of atmospheric trace contaminants at ambient pressure.

Pasture-scale methane emissions of grazing cattle

USDA-ARS?s Scientific Manuscript database

Grazing cattle are mobile point sources of methane and present challenges to quantify emissions using noninterfering micrometeorological methods. Stocking density is low and cattle can bunch up or disperse over a wide area, so knowing cattle locations is critical. The methane concentration downwind ...

Effect of dilution and ash supplement on the bio-methane potential of palm oil mill effluent (POME)

NASA Astrophysics Data System (ADS)

Jijai, Sunwanee; Muleng, Saina; Siripatana, Chairat

2017-08-01

This study aimed to evaluate the bio-methane potential of POME at different dilutions (100, 80, 60, 40, and 20 percent of initial POME) and different pH dues to different levels of ash supplement. Five different amounts of ash were added to digesters (0, 2, 4, 6, and 8 grams of ash were added to 170 ml of POME respectively). The digesters were operated in batch anaerobic digestion systems at room temperature (28-30 °C) and the experiments were performed in duplicate manner. The results showed that POME without dilution gave highest cumulative biogas (950 ml). However, 80% dilution from original POME gave the highest methane yield (45.83 mL CH4/ gCODadded or 103.13 mL CH4/ gCODremoved). Finally, the results of experiment 2, this adding ash into POME increased pH as well as enhanced the biogas production. It was found that adding ash at the ash:POME ratio of 2 g: 170 ml gave the highest both the cumulative biogas and methane yield (1,520 mL and 218.79 mL CH4/ gCODremoved respectively). The addition of ash in the raw waste of POME gave the pH in the range of criteria and highest bio-methane potential. The modified Gompertz equation, Schnute as well as Monod kinetic models were used to compare the data from the experiments. It was found that the factors that affected included, the bio-methane production and the kinetic parameters (the maximum specific methane production rates (Rm ml/day) and the methane production potential (P, mL)), initial COD, nutrients, levels of dilution, and initial pH (by adding different level of ash). However, λ (lag phase period) was not affected by initial COD and other factors. While Monod kinetics provides valuable insight in explaining what could happen behind the systematic trends.

Screening for Dissolved Methane in Groundwater Across Texas Shale Plays

NASA Astrophysics Data System (ADS)

Nicot, J. P.; Mickler, P. J.; Hildenbrand, Z.; Larson, T.; Darvari, R.; Uhlman, K.; Smyth, R. C.; Scanlon, B. R.

2014-12-01

There is considerable interest in methane concentrations in groundwater, particularly as they relate to hydraulic fracturing in shale plays. Recent studies of aquifers in the footprint of several gas plays across the US have shown that (1) dissolved thermogenic methane may or may not be present in the shallow groundwater and (2) shallow thermogenic methane may be naturally occurring and emplaced through mostly vertical migration over geologic time and not necessarily a consequence of recent unconventional gas production. We are currently conducting a large sampling campaign across the state of Texas to characterize shallow methane in fresh-water aquifers overlying shale plays and other tight formations. We collected a total of ~800 water samples, ~500 in the Barnett, ~150 in the Eagle Ford, ~80 in the Haynesville shale plays as well as ~50 in the Delaware Basin of West Texas. Preliminary analytical results suggest that dissolved methane is not widespread in shallow groundwater and that, when present at concentrations exceeding 10 mg/L, it is often of thermogenic origin according to the isotopic signature and to the presence of other light hydrocarbons. The Barnett Shale contains a large methane hotspot (~ 2 miles wide) along the Hood-Parker county line which is likely of natural origin whereas the Eagle Ford and Haynesville shales, neglecting microbial methane, show more distributed methane occurrences. Samples from the Delaware Basin show no methane except close to blowouts.

40 CFR 63.1253 - Standards: Storage tanks.

Code of Federal Regulations, 2014 CFR

2014-07-01

...) National Emission Standards for Pharmaceuticals Production § 63.1253 Standards: Storage tanks. (a) Except... a combustion control device achieving an outlet TOC concentration, as calibrated on methane or the... achieve an outlet TOC concentration, as calibrated on methane or the predominant HAP, of 50 ppmv or less...

40 CFR 63.1253 - Standards: Storage tanks.

Code of Federal Regulations, 2013 CFR

2013-07-01

...) National Emission Standards for Pharmaceuticals Production § 63.1253 Standards: Storage tanks. (a) Except... a combustion control device achieving an outlet TOC concentration, as calibrated on methane or the... achieve an outlet TOC concentration, as calibrated on methane or the predominant HAP, of 50 ppmv or less...

Sea-floor methane blow-out and global firestorm at the K-T boundary

USGS Publications Warehouse

Max, M.D.; Dillon, William P.; Nishimura, C.; Hurdle, B.G.

1999-01-01

A previously unsuspected source of fuel for the global firestorm recorded by soot in the Cretaceous-Tertiary impact layer may have resided in methane gas associated with gas hydrate in the end-Cretaceous seafloor. End-Cretaceous impact-generated shock and megawaves would have had the potential to initiate worldwide oceanic methane gas blow-outs from these deposits. The methane would likely have ignited and incompletely combusted. This large burst of methane would have been followed by longer-term methane release as a part of a positive thermal feedback in the disturbed ocean-atmosphere system.

Reactions of O/1D/ with methane and ethane.

NASA Technical Reports Server (NTRS)

Lin, C.-L.; Demore, W. B.

1973-01-01

Mixtures of nitrous oxide and methane and mixtures of nitrous oxide and ethane were photolyzed with 1849-A light. The reaction products were analyzed chromatographically. It was found that the reaction of the excited atomic oxygen with methane gives mainly CH3 and OH radicals as initial products, along with about 9% of formaldehyde and molecular hydrogen. The reaction of the excited atomic oxygen with ethane gives C2H5, OH, CH3 and CH2OH as major initial products, with only a few per cent of molecular hydrogen.

Methane in Pluto's Atmosphere

NASA Astrophysics Data System (ADS)

Roe, Henry G.

2006-09-01

The abundance of methane in Pluto's atmosphere has not been remeasured since its initial detection in 1992 by Young et al. (1997). As Pluto recedes from the Sun its atmosphere should eventually collapse and freeze out on the surface, but recent occultation observations (Elliot et al. 2003) show an expansion of the atmosphere rather than contraction. New measurements of Pluto's atmospheric methane abundance are warranted. We obtained high resolution (R=25000) near-infrared spectra of Pluto in July 2006 with NIRSPEC at the W.M. Keck II telescope and will report our initial analysis and results.

The C-13/C-12 kinetic isotope effect for soil oxidation of methane at ambient atmospheric concentrations

NASA Technical Reports Server (NTRS)

King, Stagg L.; Quay, Paul D.; Lansdown, John M.

1989-01-01

During a survey of the Alaskan North Slope to estimate the isotopic composition and fluxes of methane (CH4) from the tundra, two sites were encountered that showed net methane consumption within flux chambers. Methane concentrations decreased from ambient (1.78 ppmv) by up to 50 percent, and the delta C-13 increased by up to 10 percent in the two chamber deployments showing CH4 consumption. CH4 consumption rates were measured to be 1.2 and 0.6 mg CH4/sq m per day; the corresponding carbon kinetic isotope effects (k13/k12) were 0.974 and 0.984, respectively.

Indirect chemical effects of methane on climate warming

NASA Astrophysics Data System (ADS)

Lelieveld, Jos; Crutzen, Paul J.

1992-01-01

METHANE concentrations in the atmosphere have increased from about 0.75 to 1.7 p.p.m.v. since pre-industrial times1,2. The current annual rate of increase of about 0.8% yr-1 (ref. 2) is due to increases in industrial and agricultural emissions. This increase in atmospheric methane concentrations not only influences the climate directly, but also indirectly through chemical reactions. Here we show that the climate effects of methane's atmospheric chemistry have previously been overestimated, notably by the Inter-governmental Panel on Climate Change (IPCC)3, largely owing to neglect of the height dependence of certain atmospheric radiative processes. Using available estimates of fossil-fuel-related leaks of methane, our results show that switching from coal and oil to natural gas as an energy source would reduce climate warming. A significant fraction of methane emissions cannot, however, be accounted for by known sources; should leakages from gas production and distribution be underestimated for some countries, then it might be unwise to switch to using natural gas.

Evaluation of Methane Sources in Groundwater in Northeastern Pennsylvania

PubMed Central

Molofsky, Lisa J; Connor, John A; Wylie, Albert S; Wagner, Tom; Farhat, Shahla K

2013-01-01

Testing of 1701 water wells in northeastern Pennsylvania shows that methane is ubiquitous in groundwater, with higher concentrations observed in valleys vs. upland areas and in association with calcium-sodium-bicarbonate, sodium-bicarbonate, and sodium-chloride rich waters—indicating that, on a regional scale, methane concentrations are best correlated to topographic and hydrogeologic features, rather than shale-gas extraction. In addition, our assessment of isotopic and molecular analyses of hydrocarbon gases in the Dimock Township suggest that gases present in local water wells are most consistent with Middle and Upper Devonian gases sampled in the annular spaces of local gas wells, as opposed to Marcellus Production gas. Combined, these findings suggest that the methane concentrations in Susquehanna County water wells can be explained without the migration of Marcellus shale gas through fractures, an observation that has important implications for understanding the nature of risks associated with shale-gas extraction. PMID:23560830

Effect of coconut oil and defaunation treatment on methanogenesis in sheep.

PubMed

Machmüller, Andrea; Soliva, Carla R; Kreuzer, Michael

2003-01-01

The present study was conducted to evaluate in vivo the role of rumen ciliate protozoa with respect to the methane-suppressing effect of coconut oil. Three sheep were subjected to a 2 x 2 factorial design comprising two types of dietary lipids (50 g x kg(-1) coconut oil vs. 50 g x kg(-1) rumen-protected fat) and defaunation treatment (with vs. without). Due to the defaunation treatment, which reduced the rumen ciliate protozoa population by 94% on average, total tract fibre degradation was reduced but not the methane production. Feeding coconut oil significantly reduced daily methane release without negatively affecting the total tract nutrient digestion. Compared with the rumen-protected fat diet, coconut oil did not alter the energy retention of the animals. There was no interaction between coconut oil feeding and defaunation treatment in methane production. An interaction occurred in the concentration of methanogens in the rumen fluid, with the significantly highest values occurring when the animals received the coconut oil diet and were subjected to the defaunation treatment. Possible explanations for the apparent inconsistency between the amount of methane produced and the concentration of methane-producing microbes are discussed. Generally, the present data illustrate that a depression of the concentration of ciliate protozoa or methanogens in rumen fluid cannot be used as a reliable indicator for the success of a strategy to mitigate methane emission in vivo. The methane-suppressing effect of coconut oil seems to be mediated through a changed metabolic activity and/or composition of the rumen methanogenic population.

40 CFR 63.1304 - Testing requirements.

Code of Federal Regulations, 2011 CFR

2011-07-01

... for Hazardous Air Pollutants for Flexible Polyurethane Foam Production § 63.1304 Testing requirements... shall be: (i) Zero air (less than 10 ppm of hydrocarbon in air); and (ii) A mixture of methane and air... calibrated at a higher methane concentration (up to 2,000 ppm) than the leak definition concentration for a...

40 CFR 63.1253 - Standards: Storage tanks.

Code of Federal Regulations, 2011 CFR

2011-07-01

... Standards for Pharmaceuticals Production § 63.1253 Standards: Storage tanks. (a) Except as provided in... control device achieving an outlet TOC concentration, as calibrated on methane or the predominant HAP, of... outlet TOC concentration, as calibrated on methane or the predominant HAP, of 50 ppmv or less, and an...

40 CFR 63.1253 - Standards: Storage tanks.

Code of Federal Regulations, 2012 CFR

2012-07-01

... Standards for Pharmaceuticals Production § 63.1253 Standards: Storage tanks. (a) Except as provided in... control device achieving an outlet TOC concentration, as calibrated on methane or the predominant HAP, of... outlet TOC concentration, as calibrated on methane or the predominant HAP, of 50 ppmv or less, and an...

40 CFR 63.1304 - Testing requirements.

Code of Federal Regulations, 2012 CFR

2012-07-01

... for Hazardous Air Pollutants for Flexible Polyurethane Foam Production § 63.1304 Testing requirements... shall be: (i) Zero air (less than 10 ppm of hydrocarbon in air); and (ii) A mixture of methane and air... calibrated at a higher methane concentration (up to 2,000 ppm) than the leak definition concentration for a...

40 CFR 63.1304 - Testing requirements.

Code of Federal Regulations, 2010 CFR

2010-07-01

... for Hazardous Air Pollutants for Flexible Polyurethane Foam Production § 63.1304 Testing requirements... shall be: (i) Zero air (less than 10 ppm of hydrocarbon in air); and (ii) A mixture of methane and air... calibrated at a higher methane concentration (up to 2,000 ppm) than the leak definition concentration for a...

30 CFR 75.351 - Atmospheric monitoring systems.

Code of Federal Regulations, 2010 CFR

2010-07-01

... and type of AMS sensor at each location, and the intended air flow direction at these locations. This... methane concentration at any sensor reaches the alert level as specified in § 75.351(i). These signals... carbon monoxide, smoke, or methane concentration at any sensor reaches the alarm level as specified in...

30 CFR 75.351 - Atmospheric monitoring systems.

Code of Federal Regulations, 2011 CFR

2011-07-01

... and type of AMS sensor at each location, and the intended air flow direction at these locations. This... methane concentration at any sensor reaches the alert level as specified in § 75.351(i). These signals... carbon monoxide, smoke, or methane concentration at any sensor reaches the alarm level as specified in...

Reporting central tendencies of chamber measured surface emission and oxidation.

PubMed

Abichou, Tarek; Clark, Jeremy; Chanton, Jeffery

2011-05-01

Methane emissions, concentrations, and oxidation were measured on eleven MSW landfills in eleven states spanning from California to Pennsylvania during the three year study. The flux measurements were performed using a static chamber technique. Initial concentration samples were collected immediately after placement of the flux chamber. Oxidation of the emitted methane was evaluated using stable isotope techniques. When reporting overall surface emissions and percent oxidation for a landfill cover, central tendencies are typically used to report "averages" of the collected data. The objective of this study was to determine the best way to determine and report central tendencies. Results showed that 89% of the data sets of collected surface flux have lognormal distributions, 83% of the surface concentration data sets are also lognormal. Sixty seven percent (67%) of the isotope measured percent oxidation data sets are normally distributed. The distribution of data for all eleven landfills provides insight of the central tendencies of emissions, concentrations, and percent oxidation. When reporting the "average" measurement for both flux and concentration data collected at the surface of a landfill, statistical analyses provided insight supporting the use of the geometric mean. But the arithmetic mean can accurately represent the percent oxidation, as measured with the stable isotope technique. We examined correlations between surface CH(4) emissions and surface air CH(4) concentrations. Correlation of the concentration and flux values using the geometric mean proved to be a good fit (R(2)=0.86), indicating that surface scans are a good way of identifying locations of high emissions. Copyright © 2010 Elsevier Ltd. All rights reserved.

Tidal variability in methane and nitrous oxide emissions along a subtropical estuarine gradient

NASA Astrophysics Data System (ADS)

Sturm, Katrin; Werner, Ursula; Grinham, Alistair; Yuan, Zhiguo

2017-06-01

This study investigates the tidal variability in methane (CH4) and nitrous oxide (N2O) emissions along a gradient of the subtropical Brisbane River estuary. Sampling was conducted at the upper, middle and lower reaches over two tidal cycles in 2013 and 2014. Methane and N2O emissions varied significantly over tidal cycles at all sites. Methane and N2O emissions measured at all locations and in both campaigns varied substantially in time, with the maximum to minimum flux ratio in a cycle varying between 2.5 - 9 and 1.7-4.7 times, respectively. Methane emissions peaked just before or at slack tides. In comparison, no clear patterns were observed between the N2O emissions and the tidal cycle despite there being large variations in N2O emissions in some cases. Methane concentrations were elevated during low tides whereas N2O concentrations showed no clear pattern over the tidal cycle. Surface water concentrations and tidal currents played important roles in CH4 and N2O emissions, but wind did not. Our findings show that measurements at a single point in time and site would result in significant errors in CH4 and N2O emission estimates. An adequate and careful sampling scheme is required to capture spatial and temporal variations of CH4 and N2O emissions and surface water concentrations which should cover at least one tidal cycle in different estuarine sections.

Determination of methane concentrations in water in equilibrium with sI methane hydrate in the absence of a vapor phase by in situ Raman spectroscopy

USGS Publications Warehouse

Lu, W.; Chou, I.-Ming; Burruss, R.C.

2008-01-01

Most submarine gas hydrates are located within the two-phase equilibrium region of hydrate and interstitial water with pressures (P) ranging from 8 to 60 MPa and temperatures (T) from 275 to 293 K. However, current measurements of solubilities of methane in equilibrium with hydrate in the absence of a vapor phase are limited below 20 MPa and 283.15 K, and the differences among these data are up to 30%. When these data were extrapolated to other P-T conditions, it leads to large and poorly known uncertainties. In this study, in situ Raman spectroscopy was used to measure methane concentrations in pure water in equilibrium with sI (structure one) methane hydrate, in the absence of a vapor phase, at temperatures from 276.6 to 294.6 (??0.3) K and pressures at 10, 20, 30 and 40 (??0.4%) MPa. The relationship among concentration of methane in water in equilibrium with hydrate, in mole fraction [X(CH4)], the temperature in K, and pressure in MPa was derived as: X(CH4) = exp [11.0464 + 0.023267 P - (4886.0 + 8.0158 P)/T]. Both the standard enthalpy and entropy of hydrate dissolution at the studied T-P conditions increase slightly with increasing pressure, ranging from 41.29 to 43.29 kJ/mol and from 0.1272 to 0.1330 kJ/K ?? mol, respectively. When compared with traditional sampling and analytical methods, the advantages of our method include: (1) the use of in situ Raman signals for methane concentration measurements eliminates possible uncertainty caused by sampling and ex situ analysis, (2) it is simple and efficient, and (3) high-pressure data can be obtained safely. ?? 2007 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Holdridge, D. J.

Global Warming and Methane--Global warming, an increase in Earth's near-surface temperature, is believed to result from the buildup of what scientists refer to as ''greenhouse gases.'' These gases include water vapor, carbon dioxide, methane, nitrous oxide, ozone, perfluorocarbons, hydrofluoro-carbons, and sulfur hexafluoride. Greenhouse gases can absorb outgoing infrared (heat) radiation and re-emit it back to Earth, warming the surface. Thus, these gases act like the glass of a greenhouse enclosure, trapping infrared radiation inside and warming the space. One of the more important greenhouse gases is the naturally occurring hydrocarbon methane. Methane, a primary component of natural gas, is themore » second most important contributor to the greenhouse effect (after carbon dioxide). Natural sources of methane include wetlands, fossil sources, termites, oceans, fresh-waters, and non-wetland soils. Methane is also produced by human-related (or anthropogenic) activities such as fossil fuel production, coal mining, rice cultivation, biomass burning, water treatment facilities, waste management operations and landfills, and domesticated livestock operations (Figure 1). These anthropogenic activities account for approximately 70% of the methane emissions to the atmosphere. Methane is removed naturally from the atmosphere in three ways. These methods, commonly referred to as sinks, are oxidation by chemical reaction with tropospheric hydroxyl ion, oxidation within the stratosphere, and microbial uptake by soils. In spite of their important role in removing excess methane from the atmosphere, the sinks cannot keep up with global methane production. Methane concentrations in the atmosphere have increased by 145% since 1800. Increases in atmospheric methane roughly parallel world population growth, pointing to anthropogenic sources as the cause (Figure 2). Increases in the methane concentration reduce Earth's natural cooling efficiency by trapping more of the outgoing terrestrial infrared radiation, increasing the near-surface temperature.« less

Conversion of (Meth)acrylic acids to methane granular sludge: Initiation by specific anerobic microflora

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shtarkman, N.B.; Obraztova, A.Y.; Laurinavichyus, K.S.

1995-03-01

The role of a specific anaerobic microflora in the initiation of degradation of (meth)acrylic acids to methane by granular sludge from a UASB reactor was investigated. Associations of anaerobic bacteria isolated from the anaerobic sludge, which was used for a long time for treatment of wastewater from (meth)acrylate production, were able to realize the initial stage of (meth)acrylic acid decomposition, i.e., a conversion of acrylic and methacrylic acids to propionic and isobutyric acids, respectively. When added to granules, these association played a role of an {open_quotes}initiator{close_quotes} of the degradation process, which was then continued by the granular sludge microflora utilizingmore » propionate and isobutyrate. Some characteristics of the granules adapted to propionate or isobutyrate are presented. The rates of propionate and isobutyrate consumption by adapted granules is, respectively, 21 and 53 times higher than the values obtained for nonadapted granules. A combined use of {open_quotes}initiating{close_quotes} bacteria and adapted granules provided degradation of (meth)acrylic acids with a maximum methane yield. The possibility is discussed of employing the granules, which are adapted to short-chain fatty acids, and the {open_quotes}initiating{close_quotes} bacteria, which accomplish the initial steps of the organic material decomposition to lower fatty acids, for the conversion of various chemical compounds to methane. 10 refs., 3 figs., 2 tabs.« less

Potential of tannin-rich plants for modulating ruminal microbes and ruminal fermentation in sheep.

PubMed

Rira, M; Morgavi, D P; Archimède, H; Marie-Magdeleine, C; Popova, M; Bousseboua, H; Doreau, M

2015-01-01

The objective of this work was to study nutritional strategies for decreasing methane production by ruminants fed tropical diets, combining in vitro and in vivo methods. The in vitro approach was used to evaluate the dose effect of condensed tannins (CT) contained in leaves of Gliricidia sepium, Leucaena leucocephala, and Manihot esculenta (39, 75, and 92 g CT/kg DM, respectively) on methane production and ruminal fermentation characteristics. Tannin-rich plants (TRP) were incubated for 24 h alone or mixed with a natural grassland hay based on Dichanthium spp. (control plant), so that proportions of TRP were 0, 0.25, 0.5, 0.75, and 1.0. Methane production, VFA concentration, and fermented OM decreased with increased proportions of TRP. Numerical differences on methane production and VFA concentration among TRP sources may be due to differences in their CT content, with greater effects for L. leucocephala and M. esculenta than for G. sepium. Independently of TRP, the response to increasing doses of CT was linear for methane production but quadratic for VFA concentration. As a result, at moderate tannin dose, methane decreased more than VFA. The in vivo trial was conducted to investigate the effect of TRP on different ruminal microbial populations. To this end, 8 rumen-cannulated sheep from 2 breeds (Texel and Blackbelly) were used in two 4 × 4 Latin square designs. Diets were fed ad libitum and were composed of the same feeds used for the in vitro trial: control plant alone or combined with pellets made from TRP leaves at 44% of the diet DM. Compared to TRP, concentration of Ruminococcus flavefaciens was greater for the control diet and concentration of Ruminococcus albus was least for the control diet. The methanogen population was greater for Texel than for Blackbelly. By contrast, TRP-containing diets did not affect protozoa or Fibrobacter succinogenes numbers. Hence, TRP showed potential for mitigating methane production by ruminants. These findings suggest that TRP fed as pellets could be used to decrease methane production.

Determination of Chemical Kinetic Rate Constants of a Model for Carbothermal Processing of Lunar Regolith Simulant Using Methane

NASA Technical Reports Server (NTRS)

Balasubramaniam, R; Gokoglu, S.; Hegde, U.

2009-01-01

We have previously developed a chemical conversion model of the carbothermal processing of lunar regolith using methane to predict the rate of production of carbon monoxide. In this carbothermal process, gaseous methane is pyrolyzed as it flows over the hot surface of a molten zone of lunar regolith and is converted to carbon and hydrogen. Hydrogen is carried away by the exiting stream of gases and carbon is deposited on the melt surface. The deposited carbon mixes with the melt and reacts with the metal oxides in it to produce carbon monoxide that bubbles out of the melt. In our model, we assume that the flux of carbon deposited is equal to the product of the surface reaction rate constant gamma and the concentration of methane adjacent to the melt surface. Similarly, the rate of consumption of carbon per unit volume in the melt is equal to the product of the melt reaction rate constant k and the concentrations of carbon and metal oxide in the melt. In this paper, we describe our effort to determine gamma and k by comparison of the predictions from our model with test data obtained by ORBITEC (Orbital Technologies Corporation). The concentration of methane adjacent to the melt surface is a necessary input to the model. It is inferred from the test data by a mass balance of methane, adopting the usual assumptions of the continuously-stirred-tank-reactor model, whereby the average concentration of a given gaseous species equals its exit concentration. The reaction rates gamma and k have been determined by a non-linear least-squares fit to the test data for the production of carbon monoxide and the fraction of the incoming methane that is converted. The comparison of test data with our model predictions using the determined chemical kinetic rate constants provides a consistent interpretation of the process over the full range of temperatures, pressures, and methane flow rates used in the tests, thereby increasing our confidence to use the model for scale-up purposes.

Microbial diversity and dynamics during methane production from municipal solid waste

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bareither, Christopher A., E-mail: christopher.bareither@colostate.edu; Geological Engineering, University of Wisconsin-Madison, Madison, WI 53706; Wolfe, Georgia L., E-mail: gwolfe@wisc.edu

2013-10-15

Highlights: ► Similar bacterial communities developed following different start-up operation. ► Total methanogens in leachate during the decelerated methane phase reflected overall methane yield. ► Created correlations between methanogens, methane yield, and available substrate. ► Predominant bacteria identified with syntrophic polysaccharide degraders. ► Hydrogenotrophic methanogens were dominant in the methane generation process. - Abstract: The objectives of this study were to characterize development of bacterial and archaeal populations during biodegradation of municipal solid waste (MSW) and to link specific methanogens to methane generation. Experiments were conducted in three 0.61-m-diameter by 0.90-m-tall laboratory reactors to simulate MSW bioreactor landfills. Pyrosequencing ofmore » 16S rRNA genes was used to characterize microbial communities in both leachate and solid waste. Microbial assemblages in effluent leachate were similar between reactors during peak methane generation. Specific groups within the Bacteroidetes and Thermatogae phyla were present in all samples and were particularly abundant during peak methane generation. Microbial communities were not similar in leachate and solid fractions assayed at the end of reactor operation; solid waste contained a more abundant bacterial community of cellulose-degrading organisms (e.g., Firmicutes). Specific methanogen populations were assessed using quantitative polymerase chain reaction. Methanomicrobiales, Methanosarcinaceae, and Methanobacteriales were the predominant methanogens in all reactors, with Methanomicrobiales consistently the most abundant. Methanogen growth phases coincided with accelerated methane production, and cumulative methane yield increased with increasing total methanogen abundance. The difference in methanogen populations and corresponding methane yield is attributed to different initial cellulose and hemicellulose contents of the MSW. Higher initial cellulose and hemicellulose contents supported growth of larger methanogen populations that resulted in higher methane yield.« less

Environmental legacy of an underground gas well blowout: long-term effects of gas and brine leakage on groundwater quality

NASA Astrophysics Data System (ADS)

Schout, Gilian; Hartog, Niels; Majid Hassanizadeh, S.; Griffioen, Jasper

2017-04-01

In 1965, a catastrophic underground blowout occurred during the drilling of a gas well in the village of Sleen, the Netherlands. The blowout led to the uncontrolled release of large amounts of natural gas and saline groundwater. Now, 50 years later, a number of nearby groundwater monitoring have been sampled to study the long term effects of this event on the groundwater composition of the overlying freshwater aquifers. The findings are used as an analogue for studying the potential adverse effects of hydraulic fracturing on groundwater quality. In total, 27 samples were taken and analysed for dissolved gas molecular and isotopic composition, major ion chemistry, water isotopes and stable chlorine isotope ratios. The resulting data show that concentrations of dissolved methane are still strongly elevated compared to background samples in a plume downstream of the blowout location. Isotopic data reveals the thermogenic nature of this plume; all samples with methane concentrations greater than 10 mg/l (n=12) had δC-CH4 values greater than -30‰ (VPDB), characteristic of thermogenic methane. The maximum distance at which thermogenic methane is observed is at approximately 500 meter downstream of the centre of the blowout. The progressive enrichment of both δ13C-CH4 and δ2D-CH4, that is observed with distance from the well and decreasing methane concentrations, presents strong evidence for the role of anaerobic methane oxidation (AOM) in limiting the spread of the dissolved methane plume. Low sulphate and increased Fe(II) and Mn(II) concentrations indeed suggest that multiple AOM pathways are involved in the natural attenuation of the dissolved methane plume. Chlorine concentrations were only elevated in a subset of wells in close proximity to the blowout location, indicating that the present-day effects of brine migration are minimal. Nevertheless, elevated Na/Cl ratio's in multiple wells reveal that freshening of the aquifer is still on-going. In summary, this research sheds new light on the long-term effects of natural gas and brine leakage on groundwater quality, which is considered one of the main environmental hazards related to hydraulic fracturing and unconventional gas production in general. Notably, it shows that the anaerobic oxidation of methane may play a major role in containing the effects of uncontrolled gas migration from reservoirs to shallow aquifers.

Observations of atmospheric methane concentrations and sources at two supersites Tiksi, northern Siberia and Pallas-Sodankylä, northern Finland (Invited)

NASA Astrophysics Data System (ADS)

Laurila, T. J.; Aurela, M.; Hatakka, J.; Aalto, T.; Lohila, A.; Asmi, E.; Kondratyev, V.; Ivakhov, V.; Reshetnikov, A.; Makshtas, A. P.; Dlugokencky, E. J.; Uttal, T.

2013-12-01

Arctic and Boreal regions are important in the global methane budget mainly because emissions are large from the extensive wetlands. Recently the potential for increased emissions from methane hydrates under sediments at the bottom of the Arctic Ocean has been recognized. Resource exploitation in the Arctic is expanding and includes gas and oil drilling. Together with climate warming, we may expect changes in methane emissions from high northern latitudes. The main tools to probe the effect of this development on atmospheric methane are atmospheric methane observations and local emission measurements by micrometeorological and chamber methods. To better understand emissions at small and large scales, so called supersites have been introduced. At these sites, both atmospheric concentrations and emissions from representative ecosystems, together with suite of other environmental information, are measured continuously. We are running two of these supersites: Pallas-Sodankylä in northern Finland and Tiksi in Siberia on the coast of the Laptev Sea. In spite of the fact that both sites are north of the Arctic Circle, environmental conditions differ very much. In northern Scandinavia, climate is relatively marine, and wetland methane emissions are active throughout the year. In continental Tiksi the active layer is 30-80 cm and methane emissions cease during the coldest months when soil temperature is close to -20°C. Air mass advection is either from continental Siberia or from the Siberian seas. Forest and tundra fires are relatively common. At Pallas, advection is from the forested boreal and industrialized areas of Europe or the Norwegian or Barents Sea. In this presentation, we show seasonal variations of atmospheric methane concentrations at World Meteorological Organization - Global Atmosphere Watch sites: Pallas-Sodankylä and Tiksi. Source areas have been analyzed by trajectories. The main sources of methane in Tiksi were wetlands and the Laptev Sea, which is oversaturated regarding methane. Concentrations and their variability were high in June-October due to terrestrial and marine emissions. Sea ice restricts marine emissions very much. Interesting periods were when the sea froze in October and when the ice melted in early July. Seasonal pattern of tundra methane emissions will be presented including growing season onset in June-July, high season in August and late season emission rates extending to winter. These will be compared to emission rates at typical northern boreal fens of the Pallas-Sodankylä site. It is expected that the Tiksi and Pallas-Sodakyla site will form the foundation for further pan-Arctic comparisons between the observatories in the IASOA consortium (www.iasoa.org).

In situ Removal of Hydrogen Sulfide During Biogas Fermentation at Microaerobic Condition.

PubMed

Wu, Mengmeng; Zhang, Yima; Ye, Yuanyuan; Lin, Chunmian

2016-11-01

In this paper, rice straw was used as a raw material to produce biogas by anaerobic batch fermentation at 35 °C (mesophilic) or 55 °C (thermophilic). The hydrogen sulfide in biogas can be converted to S 0 or sulfate and removed in-situ under micro-oxygen environment. Trace oxygen was conducted to the anaerobic fermentation tank in amount of 0.5, 1.0, 2.0, 3.0, 4.0, 5.0, or 10.0 times stoichiometric equivalence, respectively, and the control experiment without oxygen addition was carried out. The results showed that the initial H 2 S concentrations of biogas are about 3235 ± 185 mg/m 3 (mesophilic) or 3394 ± 126 mg/m 3 (thermophilic), respectively. The desulfurization efficiency is 72.3 % (mesophilic) or 65.6 % (thermophilic), respectively, with oxygen addition by stoichiometric relation. When the oxygen feeded in amount of 2∼4 times, theoretical quantity demanded the removal efficiency of hydrogen sulfide could be over 92 %, and the oxygen residue in biogas could be maintained less than 0.5 %, which fit the requirement of biogas used as vehicle fuel or combined to the grid. Though further more oxygen addition could promote the removal efficiency of hydrogen sulfide (about 93.6 %), the oxygen residue in biogas would be higher than the application limit concentration (0.5 %). Whether mesophilic or thermophilic fermentation with the extra addition of oxygen, there were no obvious changes in the gas production and methane concentration. In conclusion, in-situ desulfurization can be achieved in the anaerobic methane fermentation system under micro-oxygen environment. In addition, air could be used as a substitute oxygen resource on the situation without strict demand for the methane content of biogas.

Modeling the Interaction of H2 on Root Exudate Degradation and Methanogenesis in Wetland Sediments

NASA Astrophysics Data System (ADS)

Pal, D. S.; Jaffe, P. R.

2014-12-01

CH4 is produced in wetland sediments from the microbial degradation of organic carbon through multiple fermentation steps and methanogenesis pathways. There are many potential sources of carbon for methananogenesis; in vegetated wetland sediments, microbial communities consume root exudates as a major source of organic carbon. In many methane models propionate is used as a model carbon molecule. This simple sugar is fermented into acetate and H2, acetate is transformed to methane and CO2 while the H2 and CO2 is synthesized to form an additional CH4 molecule. The hydrogenotrophic pathway involves the equilibrium of two dissolved gases, CH4 and H2. In an effort to limit CH4 emissions from wetlands, there has been growing interest in finding ways to limit plant transport of soil gases through root systems. While this may decrease the direct emissions of methane, there is little understanding about how H2 dynamics may feedback into overall methane production. Since H2 is used in methane production and produced in propionate fermentation, increased subsurface H2 concentrations can simultaneously inhibit propionate fermentation and acetate production and enhance hydrogenotrophic methanogenesis. For this study, we incubated soil samples from vegetated wetland sediments with propionate or acetate and four different hydrogen concentrations. The headspaces from these incubations were simultaneously analyzed for H2 and CH4 at multiple time points over two months. The comparison of methane production between different hydrogen concentrations and different carbon sources can indicate which process is most affected by increased hydrogen concentrations. The results from this study were combined with a newly formulated steady-state model of propionate degradation and formation of methane, that also accounts for the venting off both gases via plants. The resulting model indicates how methane production and emissions would be affected by plant volatilization.

Stable thermophilic anaerobic digestion of dissolved air flotation (DAF) sludge by co-digestion with swine manure.

PubMed

Creamer, K S; Chen, Y; Williams, C M; Cheng, J J

2010-05-01

Environmentally sound treatment of by-products in a value-adding process is an ongoing challenge in animal agriculture. The sludge produced as a result of the dissolved air flotation (DAF) wastewater treatment process in swine processing facilities is one such low-value residue. The objective of this study was to determine the fundamental performance parameters for thermophilic anaerobic digestion of DAF sludge. Testing in a semi-continuous stirred tank reactor and in batch reactors was conducted to determine the kinetics of degradation and biogas yield. Stable operation could not be achieved using pure DAF sludge as a substrate, possibly due to inhibition by long-chain fatty acids or to nutrient deficiencies. However, in a 1:1 ratio (w/w, dry basis) with swine manure, operation was both stable and productive. In the semi-continuous stirred reactor at 54.5 degrees Celsius, a hydraulic residence time of 10 days, and an organic loading rate of 4.68 gVS/day/L, the methane production rate was 2.19 L/L/day and the specific methane production rate was 0.47 L/gVS (fed). Maximum specific methanogenic activity (SMA) in batch testing was 0.15 mmoles CH(4) h(-1) gVS(-1) at a substrate concentration of 6.9 gVS L(-1). Higher substrate concentrations cause an initial lag in methane production, possibly due to long-chain fatty acid or nitrogen inhibition. Copyright 2009 Elsevier Ltd. All rights reserved.

Laser Induced Fluorescence Studies of NO Kinetics in Short Pulse Air and Air-Fuel Nonequilibrium Discharges

NASA Astrophysics Data System (ADS)

Lempert, Walter; Uddi, Mruthunjaya; Adamovich, Igor

2008-10-01

Laser Induced Fluorescence is used to measure absolute NO concentrations in air, methane-air, and ethylene-air non-equilibrium plasmas, as a function of time after initiation of a single 25 nsec discharge pulse. Peak NO density in air at 60 torr is ˜8.10^12 cm-3 occurring at ˜500 μs after the pulse, with decay time of ˜16.5 msec. Peak NO atom mole fraction in methane-air at φ=0.5 is approximately equal to that in pure air with similar rise and decay rate. In φ = 0.5 ethylene-air, the rise and decay times are also comparable to air and methane--air, but peak NO concentration is a factor of ˜2.5 lower. Spontaneous emission measurements show that N2(C) and NO (A) decay in ˜25ns and ˜2.5μs, respectively. Kinetic modeling calculations incorporating Boltzmann solver for EEDF, and electron impact and full air species kinetics, complemented with the GRI Mech 3.0 hydrocarbon oxidation mechanism, are compared with the experimental data using three different mechanisms. It is concluded that processes involving long lifetime (˜100 μsec) meta-stable states, such as N2 (X,v) and O2(b^1σ), which are formed by quenching of the metastable N2 (A) state by ground state O2, play a dominant role in NO formation.

Future methane emissions from animals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anastasi, C.; Simpson, V.J.

1993-04-20

The authors project future methane emissions from animals to the year 2025. They review the present estimated sources of methane from enteric fermentation in animals. Ruminant animals produce the highest concentrations of methane. Methane is a byproduct of anaerobic breakdown of carbohydrates by microbes in the digestive tract of herbatious animals. In general the methane production depends on the variety of animal, the quality of the feed, and the feeding level. Since cattle, sheep, and buffalo account for roughly 91% of all animal methane emission, they only study these animals in detail. Results suggest a rise in methane production ofmore » roughly 1% per year averaged through 2025. Increasing levels are found to originate from developed countries even though the feedstock levels are lower.« less

Methane- and Hydrogen-Influenced Microbial Communities in Hydrothermal Plumes above the Atlantis Massif, Mid Atlantic Ridge

NASA Astrophysics Data System (ADS)

Stewart, C. L.; Schrenk, M.

2017-12-01

Ultramafic-hosted hydrothermal systems associated with slow-spreading mid ocean ridges emit copious amounts of hydrogen and methane into the deep-sea, generated through a process known as serpentinization. Hydrothermal plumes carrying the reduced products of water-rock interaction dissipate and mix with deep seawater, and potentially harbor microbial communities adapted to these conditions. Methane and hydrogen enriched hydrothermal plumes were sampled from 3 sites near the Atlantis Massif (30°N, Mid Atlantic Ridge) during IODP Expedition 357 and used to initiate cultivation experiments targeting methanotrophic and hydrogenotrophic microorganisms. One set of experiments incubated the cultures at in situ hydrostatic pressures and gas concentrations resulting in the enrichment of gammaproteobacterial assemblages, including Marinobacter spp. That may be involved in hydrocarbon degradation. A second set of experiments pursued the anaerobic enrichment of microbial communities on solid media, resulting in the enrichment of alphaproteobacteria related to Ruegeria. The most prodigious growth in both case occurred in methane-enriched media, which may play a role as both an energy and carbon source. Ongoing work is evaluating the physiological characteristics of these isolates, including their metabolic outputs under different physical-chemical conditions. In addition to providing novel isolates from hydrothermal habitats near the Lost City Hydrothermal Field, these experiments will provide insight into the ecology of microbial communities from serpentinization influenced hydrothermal systems that may aid in future exploration of these sites.

Biogas and methane yield in response to co- and separate digestion of biomass wastes.

PubMed

Adelard, Laetitia; Poulsen, Tjalfe G; Rakotoniaina, Volana

2015-01-01

The impact of co-digestion as opposed to separate digestion, on biogas and methane yield (apparent synergetic effects) was investigated for three biomass materials (pig manure, cow manure and food waste) under mesophilic conditions over a 36 day period. In addition to the three biomass materials (digested separately), 13 biomass mixtures (co-digested) were used. Two approaches for modelling biogas and methane yield during co-digestion, based on volatile solids concentration and ultimate gas and methane potentials, were evaluated. The dependency of apparent synergetic effects on digestion time and biomass mixture composition was further assessed using measured cumulative biogas and methane yields and specific biogas and methane generation rates. Results indicated that it is possible, based on known volatile solids concentration and ultimate biogas or methane yields for a set of biomass materials digested separately, to accurately estimate gas yields for biomass mixtures made from these materials using calibrated models. For the biomass materials considered here, modelling indicated that the addition of pig manure is the main cause of synergetic effects. Co-digestion generally resulted in improved ultimate biogas and methane yields compared to separate digestion. Biogas and methane production was furthermore significantly higher early (0-7 days) and to some degree also late (above 20 days) in the digestion process during co-digestion. © The Author(s) 2014.

Stream measurements locate thermogenic methane fluxes in groundwater discharge in an area of shale-gas development.

PubMed

Heilweil, Victor M; Grieve, Paul L; Hynek, Scott A; Brantley, Susan L; Solomon, D Kip; Risser, Dennis W

2015-04-07

The environmental impacts of shale-gas development on water resources, including methane migration to shallow groundwater, have been difficult to assess. Monitoring around gas wells is generally limited to domestic water-supply wells, which often are not situated along predominant groundwater flow paths. A new concept is tested here: combining stream hydrocarbon and noble-gas measurements with reach mass-balance modeling to estimate thermogenic methane concentrations and fluxes in groundwater discharging to streams and to constrain methane sources. In the Marcellus Formation shale-gas play of northern Pennsylvania (U.S.A.), we sampled methane in 15 streams as a reconnaissance tool to locate methane-laden groundwater discharge: concentrations up to 69 μg L(-1) were observed, with four streams ≥ 5 μg L(-1). Geochemical analyses of water from one stream with high methane (Sugar Run, Lycoming County) were consistent with Middle Devonian gases. After sampling was completed, we learned of a state regulator investigation of stray-gas migration from a nearby Marcellus Formation gas well. Modeling indicates a groundwater thermogenic methane flux of about 0.5 kg d(-1) discharging into Sugar Run, possibly from this fugitive gas source. Since flow paths often coalesce into gaining streams, stream methane monitoring provides the first watershed-scale method to assess groundwater contamination from shale-gas development.

75 FR 81313 - Petitions for Modification of Existing Mandatory Safety Standards

Federal Register 2010, 2011, 2012, 2013, 2014

2010-12-27

... for methane, oxygen, and carbon monoxide concentrations using an approved hand-held device; (iv) measure air quantity using an appropriately calibrated anemometer. Methane gas or other harmful, noxious... percent methane above the previous reading or a 10 percent unplanned change in the airflow quantity from...

30 CFR 27.23 - Automatic warning device.

Code of Federal Regulations, 2010 CFR

2010-07-01

... APPROVAL OF MINING PRODUCTS METHANE-MONITORING SYSTEMS Construction and Design Requirements § 27.23... function automatically at a methane content of the mine atmosphere between 1.0 to 1.5 volume percent and at all higher concentrations of methane. (c) It is recommended that the automatic warning device be...

Monitoring Production of Methane from Spills of Gasoline at UST Release Sites.

EPA Science Inventory

ORD-362 (Rev 06/10/05) (Webforms v2.4) Abstract: Anaerobic biodegradation of the BTEX compounds can produce substantial concentrations of methane in ground water at gasoline spill sites. This methane can escape the ground water, move through the unsaturated zone and potentiall...

Transcontinental Surface Validation of Satellite Observations of Enhanced Methane Anomalies Associated with Fossil Fuel Industrial Methane Emissions

NASA Astrophysics Data System (ADS)

Leifer, I.; Culling, D.; Schneising, O.; Bovensmann, H.; Buchwitz, M.; Burrows, J. P.

2012-12-01

A ground-based, transcontinental (Florida to California - i.e., satellite-scale) survey was conducted to understand better the role of fossil fuel industrial (FFI) fugitive emissions of the potent greenhouse gas, methane. Data were collected by flame ion detection gas chromatography (Fall 2010) and by a cavity ring-down sensor (Winter 2012) from a nearly continuously moving recreational vehicle, allowing 24/7 data collection. Nocturnal methane measurements for similar sources tended to be higher compared to daytime values, sometime significantly, due to day/night meteorological differences. Data revealed strong and persistent FFI methane sources associated with refining, a presumed major pipeline leak, and several minor pipeline leaks, a coal loading plant, and areas of active petroleum production. Data showed FFI source emissions were highly transient and heterogeneous; however, integrated over these large-scale facilities, methane signatures overwhelmed that of other sources, creating clearly identifiable plumes that were well elevated above ambient. The highest methane concentration recorded was 39 ppm at an active central valley California production field, while desert values were as low as 1.80 ppm. Surface methane data show similar trends with strong emissions correlated with FFI on large (4° bin) scales and positive methane anomalies centered on the Gulf Coast area of Houston, home to most of US refining capacity. Comparison with SCIAMACHY and GOSAT satellite data show agreement with surface data in the large-scale methane spatial patterns. Positive satellite methane anomalies in the southeast and Mexico largely correlated with methane anthropogenic and wetland inventory models suggests most strong ground methane anomalies in the Gulf of Mexico region were related to dominant FFI input for most seasons. Wind advection played a role, in some cases confounding a clear relationship. Results are consistent with a non-negligible underestimation of the FFI contribution to global methane budgets.; In situ methane concentrations during transcontinental survey Fall 2010.

Observed variations of methane on Mars unexplained by known atmospheric chemistry and physics.

PubMed

Lefèvre, Franck; Forget, François

2009-08-06

The detection of methane on Mars has revived the possibility of past or extant life on this planet, despite the fact that an abiogenic origin is thought to be equally plausible. An intriguing aspect of the recent observations of methane on Mars is that methane concentrations appear to be locally enhanced and change with the seasons. However, methane has a photochemical lifetime of several centuries, and is therefore expected to have a spatially uniform distribution on the planet. Here we use a global climate model of Mars with coupled chemistry to examine the implications of the recently observed variations of Martian methane for our understanding of the chemistry of methane. We find that photochemistry as currently understood does not produce measurable variations in methane concentrations, even in the case of a current, local and episodic methane release. In contrast, we find that the condensation-sublimation cycle of Mars' carbon dioxide atmosphere can generate large-scale methane variations differing from those observed. In order to reproduce local methane enhancements similar to those recently reported, we show that an atmospheric lifetime of less than 200 days is necessary, even if a local source of methane is only active around the time of the observation itself. This implies an unidentified methane loss process that is 600 times faster than predicted by standard photochemistry. The existence of such a fast loss in the Martian atmosphere is difficult to reconcile with the observed distribution of other trace gas species. In the case of a destruction mechanism only active at the surface of Mars, destruction of methane must occur with an even shorter timescale of the order of approximately 1 hour to explain the observations. If recent observations of spatial and temporal variations of methane are confirmed, this would suggest an extraordinarily harsh environment for the survival of organics on the planet.

30 CFR 57.22604 - Blasting from the surface (II-B mines).

Code of Federal Regulations, 2010 CFR

2010-07-01

... MINES Safety Standards for Methane in Metal and Nonmetal Mines Explosives § 57.22604 Blasting from the surface (II-B mines). All development, production, and bench rounds shall be initiated from the surface... methane tests shall not enter the mine until all blast areas have been tested for methane. ...

30 CFR 57.22604 - Blasting from the surface (II-B mines).

Code of Federal Regulations, 2013 CFR

2013-07-01

... MINES Safety Standards for Methane in Metal and Nonmetal Mines Explosives § 57.22604 Blasting from the surface (II-B mines). All development, production, and bench rounds shall be initiated from the surface... methane tests shall not enter the mine until all blast areas have been tested for methane. ...

30 CFR 57.22604 - Blasting from the surface (II-B mines).

Code of Federal Regulations, 2011 CFR

2011-07-01

... MINES Safety Standards for Methane in Metal and Nonmetal Mines Explosives § 57.22604 Blasting from the surface (II-B mines). All development, production, and bench rounds shall be initiated from the surface... methane tests shall not enter the mine until all blast areas have been tested for methane. ...

30 CFR 57.22604 - Blasting from the surface (II-B mines).

Code of Federal Regulations, 2014 CFR

2014-07-01

... MINES Safety Standards for Methane in Metal and Nonmetal Mines Explosives § 57.22604 Blasting from the surface (II-B mines). All development, production, and bench rounds shall be initiated from the surface... methane tests shall not enter the mine until all blast areas have been tested for methane. ...

30 CFR 57.22604 - Blasting from the surface (II-B mines).

Code of Federal Regulations, 2012 CFR

2012-07-01

... MINES Safety Standards for Methane in Metal and Nonmetal Mines Explosives § 57.22604 Blasting from the surface (II-B mines). All development, production, and bench rounds shall be initiated from the surface... methane tests shall not enter the mine until all blast areas have been tested for methane. ...

A New IPCC Tier 4 Site-Specific Model for Landfill Methane Emissions Inclusive of Seasonal Methane Oxidation

USDA-ARS?s Scientific Manuscript database

This project was initiated in the U.S. by the California Energy Commission (CEC) in cooperation with the California Integrated Waste Management Board and the California Air Resources Board to develop improved methods for landfill methane emissions for the California greenhouse gas inventory. This 3-...

Biogas by semi-continuous anaerobic digestion of food waste.

PubMed

Zhang, Cunsheng; Su, Haijia; Wang, Zhenbin; Tan, Tianwei; Qin, Peiyong

2015-04-01

The semi-continuous anaerobic digestion of food waste was investigated in 1-L and 20-L continuously stirred tank reactors (CSTRs), to identify the optimum operation condition and the methane production of the semi-continuous anaerobic process. Results from a 1-L digester indicated that the optimum organic loading rate (OLR) for semi-continuous digestion is 8 g VS/L/day. The corresponding methane yield and chemical oxygen demand (COD) reduction were 385 mL/g VS and 80.2 %, respectively. Anaerobic digestion was inhibited at high OLRs (12 and 16 g VS/L/day), due to volatile fatty acid (VFA) accumulation. Results from a 20-L digester indicated that a higher methane yield of 423 mL/g VS was obtained at this larger scale. The analysis showed that the methane production at the optimum OLR fitted well with the determined kinetics equation. An obvious decrease on the methane content was observed at the initial of digestion. The increased metabolization of microbes and the activity decrease of methanogen caused by VFA accumulation explained the lower methane content at the initial of digestion.

Redox controls on methane formation, migration and fate in shallow aquifers

NASA Astrophysics Data System (ADS)

Humez, Pauline; Mayer, Bernhard; Nightingale, Michael; Becker, Veith; Kingston, Andrew; Taylor, Stephen; Bayegnak, Guy; Millot, Romain; Kloppmann, Wolfram

2016-07-01

Development of unconventional energy resources such as shale gas and coalbed methane has generated some public concern with regard to the protection of groundwater and surface water resources from leakage of stray gas from the deep subsurface. In terms of environmental impact to and risk assessment of shallow groundwater resources, the ultimate challenge is to distinguish (a) natural in situ production of biogenic methane, (b) biogenic or thermogenic methane migration into shallow aquifers due to natural causes, and (c) thermogenic methane migration from deep sources due to human activities associated with the exploitation of conventional or unconventional oil and gas resources. This study combines aqueous and gas (dissolved and free) geochemical and isotope data from 372 groundwater samples obtained from 186 monitoring wells of the provincial Groundwater Observation Well Network (GOWN) in Alberta (Canada), a province with a long record of conventional and unconventional hydrocarbon exploration. We investigated whether methane occurring in shallow groundwater formed in situ, or whether it migrated into the shallow aquifers from elsewhere in the stratigraphic column. It was found that methane is ubiquitous in groundwater in Alberta and is predominantly of biogenic origin. The highest concentrations of biogenic methane (> 0.01 mM or > 0.2 mgL-1), characterized by δ13CCH4 values < -55 ‰, occurred in anoxic Na-Cl, Na-HCO3, and Na-HCO3-Cl type groundwaters with negligible concentrations of nitrate and sulfate suggesting that methane was formed in situ under methanogenic conditions for 39.1 % of the samples. In only a few cases (3.7 %) was methane of biogenic origin found in more oxidizing shallow aquifer portions suggesting limited upward migration from deeper methanogenic aquifers. Of the samples, 14.1 % contained methane with δ13CCH4 values > -54 ‰, potentially suggesting a thermogenic origin, but aqueous and isotope geochemistry data revealed that the elevated δ13CCH4 values were caused by microbial oxidation of biogenic methane or post-sampling degradation of low CH4 content samples rather than migration of deep thermogenic gas. A significant number of samples (39.2 %) contained methane with predominantly biogenic C isotope ratios (δ13CCH4 < -55 ‰) accompanied by elevated concentrations of ethane and sometimes trace concentrations of propane. These gases, observed in 28.1 % of the samples, bearing both biogenic (δ13C) and thermogenic (presence of C3) characteristics, are most likely derived from shallow coal seams that are prevalent in the Cretaceous Horseshoe Canyon and neighboring formations in which some of the groundwater wells are completed. The remaining 3.7 % of samples were not assigned because of conflicting parameters in the data sets or between replicates samples. Hence, despite quite variable gas concentrations and a wide range of δ13CCH4 values in baseline groundwater samples, we found no conclusive evidence for deep thermogenic gas migration into shallow aquifers either naturally or via anthropogenically induced pathways in this baseline groundwater survey. This study shows that the combined interpretation of aqueous geochemistry data in concert with chemical and isotopic compositions of dissolved and/or free gas can yield unprecedented insights into formation and potential migration of methane in shallow groundwater. This enables the assessment of cross-formational methane migration and provides an understanding of alkane gas sources and pathways necessary for a stringent baseline definition in the context of current and future unconventional hydrocarbon exploration and exploitation.

GreenLITE™: a novel approach for quantification of atmospheric methane concentrations, 2-D spatial distribution, and flux

NASA Astrophysics Data System (ADS)

Dobler, J. T.; Blume, N.; Pernini, T.; Zaccheo, T. S.; Braun, M.

2017-12-01

The Greenhouse Gas Laser Imaging Tomography Experiment (GreenLITE™) was originally developed by Harris and Atmospheric and Environmental Research (AER) under a cooperative agreement with the National Energy Technology Laboratory of the Department of Energy. The system, initially conceived in 2013, used a pair of high-precision intensity modulated continuous wave (IMCW) transceivers and a series of retroreflectors to generate overlapping atmospheric density measurements of carbon dioxide (CO2) for continuous monitoring of ground carbon storage sites. The overlapping measurements provide an estimate of the two-dimensional (2-D) spatial distribution of the gas within the area of interest using sparsely sampled tomography methods. GreenLITE™ is a full end-to-end system that utilizes standard 4G connectivity and an all cloud-based data storage, processing, and dissemination suite to provide autonomous, near-real-time data via a web-based user interface. The system has been demonstrated for measuring and mapping CO2 over areas from approximately 0.04 km2 to 25 km2 ( 200 m X 200 m, up to 5 km X 5 km), including a year-long demonstration over the city of Paris, France. In late 2016, the GreenLITE™ system was converted by Harris and AER to provide similar measurement capabilities for methane (CH4). Recent experiments have shown that GreenLITE™ CH4 retrieved concentrations agree with a Picarro cavity ring-down spectrometer, calibrated with World Meteorological Organization traceable gas, to within approximately 0.5% of background or 10-15 parts per billion. The system has been tested with several controlled releases over the past year, including a weeklong experiment at an industrial oil and gas facility. Recent experiments have been exploring the use of a box model-based approach for estimating flux, and the initial results are very promising. We will present a description of the instrument, share some recent methane experimental results, and describe the flux estimation process and results of testing to date.

Biodegradation of individual and multiple chlorinated aliphatic hydrocarbons by methane-oxidizing cultures.

PubMed Central

Chang, H L; Alvarez-Cohen, L

1996-01-01

The microbial degradation of chlorinated and nonchlorinated methanes, ethanes, and ethanes by a mixed methane-oxidizing culture grown under chemostat and batch conditions is evaluated and compared with that by two pure methanotrophic strains: CAC1 (isolated from the mixed culture) and Methylosinus trichosporium OB3b. With the exception of 1,1-dichloroethylene, the transformation capacity (Tc) for each chlorinated aliphatic hydrocarbon was generally found to be in inverse proportion to its chlorine content within each aliphatic group (i.e., methanes, ethanes, and ethenes), whereas similar trends were not observed for degradation rate constants. Tc trends were similar for all methane-oxidizing cultures tested. None of the cultures were able to degrade the fully chlorinated aliphatics such as perchloroethylene and carbon tetrachloride. Of the four cultures tested, the chemostat-grown mixed culture exhibited the highest Tc for trichloroethylene, cis-1,2-dichloroethylene, tetrachloroethane, 1,1,1-trichloroethane, and 1,2-dichloroethane, whereas the pure batch-grown OB3b culture exhibited the highest Tc for all other compounds tested. The product toxicity of chlorinated aliphatic hydrocarbons in a mixture containing multiple compounds was cumulative and predictable when using parameters measured from the degradation of individual compounds. The Tc for each chlorinated aliphatic hydrocarbon in a mixture (Tcmix) and the total Tc for the mixture (sigma Tcmix) are functions of the individual Tc, the initial substrate concentration (S0), and the first-order rate constant (k/Ks) of each compound in the mixture, indicating the importance of identifying the properties and compositions of all potentially degradable compounds in a contaminant mixture. PMID:8795228

The impact of compaction and leachate recirculation on waste degradation in simulated landfills.

PubMed

Ko, Jae Hac; Yang, Fan; Xu, Qiyong

2016-07-01

This study investigated the impact of compaction and leachate recirculation on anaerobic degradation of municipal solid waste (MSW) at different methane formation phases. Two stainless steel lysimeters, C1 and C2, were constructed by equipping a hydraulic cylinder to apply pressure load (42kPs) on the MSW. When MSW started to produce methane, C1 was compacted, but C2 was compacted when the methane production rate declined from the peak generation rate. Methane production of C1was inhibited by the compaction and resulted in producing a total of 106L methane (44L/kgVS). However, the compaction in C2 promoted MSW degradation resulting in producing a total of 298L methane (125L/kgVS). The concentrations of volatile fatty acids and chemical oxygen demand showed temporary increases, when pressure load was applied. It was considered that the increased substrate accessibility within MSW by compaction could cause either the inhibition or the enhancement of methane production, depending the tolerability of methanogens on the acidic inhibition. Leachate recirculation also gave positive effects on methane generation from wet waste in the decelerated methanogenic phase by increasing mass transfer and the concentrations of volatile fatty acids. Copyright © 2016 Elsevier Ltd. All rights reserved.

[Remote system of natural gas leakage based on multi-wavelength characteristics spectrum analysis].

PubMed

Li, Jing; Lu, Xu-Tao; Yang, Ze-Hui

2014-05-01

In order to be able to quickly, to a wide range of natural gas pipeline leakage monitoring, the remote detection system for concentration of methane gas was designed based on static Fourier transform interferometer. The system used infrared light, which the center wavelength was calibrated to absorption peaks of methane molecules, to irradiated tested area, and then got the interference fringes by converging collimation system and interference module. Finally, the system calculated the concentration-path-length product in tested area by multi-wavelength characteristics spectrum analysis algorithm, furthermore the inversion of the corresponding concentration of methane. By HITRAN spectrum database, Selected wavelength position of 1. 65 microm as the main characteristic absorption peaks, thereby using 1. 65 pm DFB laser as the light source. In order to improve the detection accuracy and stability without increasing the hardware configuration of the system, solved absorbance ratio by the auxiliary wave-length, and then get concentration-path-length product of measured gas by the method of the calculation proportion of multi-wavelength characteristics. The measurement error from external disturbance is caused by this innovative approach, and it is more similar to a differential measurement. It will eliminate errors in the process of solving the ratio of multi-wavelength characteristics, and can improve accuracy and stability of the system. The infrared absorption spectrum of methane is constant, the ratio of absorbance of any two wavelengths by methane is also constant. The error coefficients produced by the system is the same when it received the same external interference, so the measured noise of the system can be effectively reduced by the ratio method. Experimental tested standards methane gas tank with leaking rate constant. Using the tested data of PN1000 type portable methane detector as the standard data, and were compared to the tested data of the system, while tested distance of the system were 100, 200 and 500 m. Experimental results show that the methane concentration detected value was stable after a certain time leakage, the concentration-path-length product value of the system was stable. For detection distance of 100 m, the detection error of the concentration-path-length product was less than 1. 0%. With increasing distance from tested area, the detection error is increased correspondingly. When the distance was 500 m, the detection error was less than 4. 5%. In short, the detected error of the system is less than 5. 0% after the gas leakage stable, to meet the requirements of the field of natural gas leakage remote sensing.

Mobile measurement of methane and hydrogen sulfide at natural gas production site fence lines in the Texas Barnett Shale.

PubMed

Eapi, Gautam R; Sabnis, Madhu S; Sattler, Melanie L

2014-08-01

Production of natural gas from shale formations is bringing drilling and production operations to regions of the United States that have seen little or no similar activity in the past, which has generated considerable interest in potential environmental impacts. This study focused on the Barnett Shale Fort Worth Basin in Texas, which saw the number of gas-producing wells grow from 726 in 2001 to 15,870 in 2011. This study aimed to measure fence line concentrations of methane and hydrogen sulfide at natural gas production sites (wells, liquid storage tanks, and associated equipment) in the four core counties of the Barnett Shale (Denton, Johnson, Tarrant, and Wise). A mobile measurement survey was conducted in the vicinity of 4788 wells near 401 lease sites, representing 35% of gas production volume, 31% of wells, and 38% of condensate production volume in the four-county core area. Methane and hydrogen sulfide concentrations were measured using a Picarro G2204 cavity ring-down spectrometer (CRDS). Since the research team did not have access to lease site interiors, measurements were made by driving on roads on the exterior of the lease sites. Over 150 hr of data were collected from March to July 2012. During two sets of drive-by measurements, it was found that 66 sites (16.5%) had methane concentrations > 3 parts per million (ppm) just beyond the fence line. Thirty-two lease sites (8.0%) had hydrogen sulfide concentrations > 4.7 parts per billion (ppb) (odor recognition threshold) just beyond the fence line. Measured concentrations generally did not correlate well with site characteristics (natural gas production volume, number of wells, or condensate production). t tests showed that for two counties, methane concentrations for dry sites were higher than those for wet sites. Follow-up study is recommended to provide more information at sites identified with high levels of methane and hydrogen sulfide. Implications: Information regarding air emissions from shale gas production is important given the recent increase in number of wells in various regions in the United States. Methane, the primary natural gas constituent, is a greenhouse gas; hydrogen sulfide, which can be present in gas condensate, is an odor-causing compound. This study surveyed wells representing one-third of the natural gas production volume in the Texas Barnett Shale and identified the percent of sites that warrant further study due to their fence line methane and hydrogen sulfide concentrations.

Tea saponin reduced methanogenesis in vitro but increased methane yield in lactating dairy cows.

PubMed

Guyader, J; Eugène, M; Doreau, M; Morgavi, D P; Gérard, C; Martin, C

2017-03-01

The effect of tea saponin supplementation in the ruminant diet on methane emissions, rumen fermentation, and digestive processes is still under debate. The objective of this study was to assess the effect of this plant extract on methanogenesis, total-tract digestibility, and lactating performances of dairy cows. The work included 2 independent and successive experiments. First, the effect of 7 tea saponin doses (from 0 to 0.50 g/L) on methane emissions and protozoa concentrations was tested in 2 repeated in vitro batch culture incubations using bovine rumen contents as inoculum and a cereal mixture as substrate. After 18 h of incubation, total gas production and composition as well as rumen fermentation parameters and protozoa concentration were analyzed. Increasing dosage of the plant extract reduced methane production and protozoa concentration, with a maximum reduction of 29% for CH 4 (mL/g of substrate) and 51% for protozoa (10 5 /mL). Tea saponin did not affect volatile fatty acids concentration, but marginally decreased total gas production by 5% at the highest dose. Second, a 2-period crossover design experiment was carried out with 8 lactating dairy cows fed a basal diet (54% corn silage, 6% hay, and 40% pelleted concentrates on a dry matter basis) without (control) or with 0.52% tea saponin (TSP). Each experimental period lasted 5 wk. Animals were fed ad libitum during the first 3 wk of the period (wk 1, 2, and 3) and restricted (95% of ad libitum intake) during the last 2 wk (wk 4 and 5). Intake and milk production were recorded daily. Methane emissions were quantified using open chambers (2 d, wk 4). Total-tract digestibility and nitrogen balance were determined from total feces and urine collected separately (5 d, wk 5). Rumen fermentation parameters and protozoa concentration were analyzed from samples taken after morning feeding (1 d, wk 5). Milk production, dry matter intake, and feed efficiency were reduced with TSP (-18, -12, and -8%, respectively). As daily methane production (g/d) was not affected, methane emissions (g/kg of dry matter intake) increased by 14% with TSP. Total-tract digestibility and nitrogen balance were similar between diets, except for acid detergent fiber digestibility, which tended to be improved with TSP (+4 percentage units). Rumen fermentation parameters and protozoa concentration were relatively unchanged by diets. Under the conditions of this experiment, tea saponin is not efficient to reduce methane emissions from dairy cows. Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

The interaction of climate change and methane hydrates

USGS Publications Warehouse

Ruppel, Carolyn D.; Kessler, John D.

2017-01-01

Gas hydrate, a frozen, naturally-occurring, and highly-concentrated form of methane, sequesters significant carbon in the global system and is stable only over a range of low-temperature and moderate-pressure conditions. Gas hydrate is widespread in the sediments of marine continental margins and permafrost areas, locations where ocean and atmospheric warming may perturb the hydrate stability field and lead to release of the sequestered methane into the overlying sediments and soils. Methane and methane-derived carbon that escape from sediments and soils and reach the atmosphere could exacerbate greenhouse warming. The synergy between warming climate and gas hydrate dissociation feeds a popular perception that global warming could drive catastrophic methane releases from the contemporary gas hydrate reservoir. Appropriate evaluation of the two sides of the climate-methane hydrate synergy requires assessing direct and indirect observational data related to gas hydrate dissociation phenomena and numerical models that track the interaction of gas hydrates/methane with the ocean and/or atmosphere. Methane hydrate is likely undergoing dissociation now on global upper continental slopes and on continental shelves that ring the Arctic Ocean. Many factors—the depth of the gas hydrates in sediments, strong sediment and water column sinks, and the inability of bubbles emitted at the seafloor to deliver methane to the sea-air interface in most cases—mitigate the impact of gas hydrate dissociation on atmospheric greenhouse gas concentrations though. There is no conclusive proof that hydrate-derived methane is reaching the atmosphere now, but more observational data and improved numerical models will better characterize the climate-hydrate synergy in the future.

The interaction of climate change and methane hydrates

NASA Astrophysics Data System (ADS)

Ruppel, Carolyn D.; Kessler, John D.

2017-03-01

Gas hydrate, a frozen, naturally-occurring, and highly-concentrated form of methane, sequesters significant carbon in the global system and is stable only over a range of low-temperature and moderate-pressure conditions. Gas hydrate is widespread in the sediments of marine continental margins and permafrost areas, locations where ocean and atmospheric warming may perturb the hydrate stability field and lead to release of the sequestered methane into the overlying sediments and soils. Methane and methane-derived carbon that escape from sediments and soils and reach the atmosphere could exacerbate greenhouse warming. The synergy between warming climate and gas hydrate dissociation feeds a popular perception that global warming could drive catastrophic methane releases from the contemporary gas hydrate reservoir. Appropriate evaluation of the two sides of the climate-methane hydrate synergy requires assessing direct and indirect observational data related to gas hydrate dissociation phenomena and numerical models that track the interaction of gas hydrates/methane with the ocean and/or atmosphere. Methane hydrate is likely undergoing dissociation now on global upper continental slopes and on continental shelves that ring the Arctic Ocean. Many factors—the depth of the gas hydrates in sediments, strong sediment and water column sinks, and the inability of bubbles emitted at the seafloor to deliver methane to the sea-air interface in most cases—mitigate the impact of gas hydrate dissociation on atmospheric greenhouse gas concentrations though. There is no conclusive proof that hydrate-derived methane is reaching the atmosphere now, but more observational data and improved numerical models will better characterize the climate-hydrate synergy in the future.

The interaction of climate change and methane hydrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ruppel, Carolyn D.; Kessler, John D.

Gas hydrate, a frozen, naturally-occurring, and highly-concentrated form of methane, sequesters significant carbon in the global system and is stable only over a range of low-temperature and moderate-pressure conditions. Gas hydrate is widespread in the sediments of marine continental margins and permafrost areas, locations where ocean and atmospheric warming may perturb the hydrate stability field and lead to release of the sequestered methane into the overlying sediments and soils. Methane and methane-derived carbon that escape from sediments and soils and reach the atmosphere could exacerbate greenhouse warming. The synergy between warming climate and gas hydrate dissociation feeds a popular perceptionmore » that global warming could drive catastrophic methane releases from the contemporary gas hydrate reservoir. Appropriate evaluation of the two sides of the climate-methane hydrate synergy requires assessing direct and indirect observational data related to gas hydrate dissociation phenomena and numerical models that track the interaction of gas hydrates/methane with the ocean and/or atmosphere. Methane hydrate is likely undergoing dissociation now on global upper continental slopes and on continental shelves that ring the Arctic Ocean. Many factors—the depth of the gas hydrates in sediments, strong sediment and water column sinks, and the inability of bubbles emitted at the seafloor to deliver methane to the sea-air interface in most cases—mitigate the impact of gas hydrate dissociation on atmospheric greenhouse gas concentrations though. There is no conclusive proof that hydrate-derived methane is reaching the atmosphere now, but more observational data and improved numerical models will better characterize the climate-hydrate synergy in the future.« less

The interaction of climate change and methane hydrates

DOE PAGES

Ruppel, Carolyn D.; Kessler, John D.

2016-12-14

Gas hydrate, a frozen, naturally-occurring, and highly-concentrated form of methane, sequesters significant carbon in the global system and is stable only over a range of low-temperature and moderate-pressure conditions. Gas hydrate is widespread in the sediments of marine continental margins and permafrost areas, locations where ocean and atmospheric warming may perturb the hydrate stability field and lead to release of the sequestered methane into the overlying sediments and soils. Methane and methane-derived carbon that escape from sediments and soils and reach the atmosphere could exacerbate greenhouse warming. The synergy between warming climate and gas hydrate dissociation feeds a popular perceptionmore » that global warming could drive catastrophic methane releases from the contemporary gas hydrate reservoir. Appropriate evaluation of the two sides of the climate-methane hydrate synergy requires assessing direct and indirect observational data related to gas hydrate dissociation phenomena and numerical models that track the interaction of gas hydrates/methane with the ocean and/or atmosphere. Methane hydrate is likely undergoing dissociation now on global upper continental slopes and on continental shelves that ring the Arctic Ocean. Many factors—the depth of the gas hydrates in sediments, strong sediment and water column sinks, and the inability of bubbles emitted at the seafloor to deliver methane to the sea-air interface in most cases—mitigate the impact of gas hydrate dissociation on atmospheric greenhouse gas concentrations though. There is no conclusive proof that hydrate-derived methane is reaching the atmosphere now, but more observational data and improved numerical models will better characterize the climate-hydrate synergy in the future.« less

40 CFR 63.1426 - Process vent requirements for determining organic HAP concentration, control efficiency, and...

Code of Federal Regulations, 2011 CFR

2011-07-01

... National Emission Standards for Hazardous Air Pollutant Emissions for Polyether Polyols Production § 63... percent reduction may be measured as total epoxide, total organic HAP, or as TOC minus methane and ethane... TOC (minus methane and ethane) concentrations in all process vent streams and primary and secondary...

40 CFR 63.1304 - Testing requirements.

Code of Federal Regulations, 2014 CFR

2014-07-01

... Emission Standards for Hazardous Air Pollutants for Flexible Polyurethane Foam Production § 63.1304 Testing... shall be: (i) Zero air (less than 10 ppm of hydrocarbon in air); and (ii) A mixture of methane and air... calibrated at a higher methane concentration (up to 2,000 ppm) than the leak definition concentration for a...

40 CFR 63.1426 - Process vent requirements for determining organic HAP concentration, control efficiency, and...

Code of Federal Regulations, 2012 CFR

2012-07-01

... National Emission Standards for Hazardous Air Pollutant Emissions for Polyether Polyols Production § 63... percent reduction may be measured as total epoxide, total organic HAP, or as TOC minus methane and ethane... TOC (minus methane and ethane) concentrations in all process vent streams and primary and secondary...

40 CFR 63.1304 - Testing requirements.

Code of Federal Regulations, 2013 CFR

2013-07-01

... Emission Standards for Hazardous Air Pollutants for Flexible Polyurethane Foam Production § 63.1304 Testing... shall be: (i) Zero air (less than 10 ppm of hydrocarbon in air); and (ii) A mixture of methane and air... calibrated at a higher methane concentration (up to 2,000 ppm) than the leak definition concentration for a...

Profiles of alpha 13 C and alpha D in methane from the lower stratosphere

NASA Technical Reports Server (NTRS)

Wahlen, Martin; Tanaka, Nori; Henry, Robert; Weyer, Harley

1991-01-01

Methane is an important greenhouse gas of biogenic and anthropogenic origin for which global budgets are being constructed from a variety of data. One approach to the global methane budget is the use of the stable isotopes C-13 and D, and the radionuclide C-14 as tracers. The authors measured the isotopic composition of methane from various sources and in tropospheric air for a number of locations. Here, the authors report on the isotopic composition of methane from the lower stratosphere. Measurements of this concentration in the stratosphere can yield estimates for the kinetic isotope effects in the methane destruction reactions. These effects have to be known for quantitative isotopic methane budgets.

Natural and anthropogenic variations in methane sources during the past two millennia.

PubMed

Sapart, C J; Monteil, G; Prokopiou, M; van de Wal, R S W; Kaplan, J O; Sperlich, P; Krumhardt, K M; van der Veen, C; Houweling, S; Krol, M C; Blunier, T; Sowers, T; Martinerie, P; Witrant, E; Dahl-Jensen, D; Röckmann, T

2012-10-04

Methane is an important greenhouse gas that is emitted from multiple natural and anthropogenic sources. Atmospheric methane concentrations have varied on a number of timescales in the past, but what has caused these variations is not always well understood. The different sources and sinks of methane have specific isotopic signatures, and the isotopic composition of methane can therefore help to identify the environmental drivers of variations in atmospheric methane concentrations. Here we present high-resolution carbon isotope data (δ(13)C content) for methane from two ice cores from Greenland for the past two millennia. We find that the δ(13)C content underwent pronounced centennial-scale variations between 100 BC and AD 1600. With the help of two-box model calculations, we show that the centennial-scale variations in isotope ratios can be attributed to changes in pyrogenic and biogenic sources. We find correlations between these source changes and both natural climate variability--such as the Medieval Climate Anomaly and the Little Ice Age--and changes in human population and land use, such as the decline of the Roman empire and the Han dynasty, and the population expansion during the medieval period.

Baseline assessment of groundwater quality in Pike County, Pennsylvania, 2015

USGS Publications Warehouse

Senior, Lisa A.; Cravotta, Charles A.

2017-12-29

The Devonian-age Marcellus Shale and the Ordovician-age Utica Shale, which have the potential for natural gas development, underlie Pike County and neighboring counties in northeastern Pennsylvania. In 2015, the U.S. Geological Survey, in cooperation with the Pike County Conservation District, conducted a study that expanded on a previous more limited 2012 study to assess baseline shallow groundwater quality in bedrock aquifers in Pike County prior to possible extensive shale-gas development. Seventy-nine water wells ranging in depths from 80 to 610 feet were sampled during June through September 2015 to provide data on the presence of methane and other aspects of existing groundwater quality in the various bedrock geologic units throughout the county, including concentrations of inorganic constituents commonly present at low values in shallow, fresh groundwater but elevated in brines associated with fluids extracted from geologic formations during shale-gas development. All groundwater samples collected in 2015 were analyzed for bacteria, dissolved and total major ions, nutrients, selected dissolved and total inorganic trace constituents (including metals and other elements), radon-222, gross alpha- and gross beta-particle activity, dissolved gases (methane, ethane, and propane), and, if sufficient methane was present, the isotopic composition of methane. Additionally, samples from 20 wells distributed throughout the county were analyzed for selected man-made volatile organic compounds, and samples from 13 wells where waters had detectable gross alpha activity were analyzed for radium-226 on the basis of relatively elevated gross alpha-particle activity.Results of the 2015 study show that groundwater quality generally met most drinking-water standards for constituents and properties included in analyses, but groundwater samples from some wells had one or more constituents or properties, including arsenic, iron, manganese, pH, bacteria, sodium, chloride, sulfate, total dissolved solids, and radon-222, that did not meet (commonly termed failed or exceeded) primary or secondary maximum contaminant levels (MCLs) or Health Advisories (HA) for drinking water. Except for iron, dissolved and total concentrations of major ions and most trace constituents generally were similar. Only 1 of 79 well-water samples had any constituent that exceeded a MCL, with an arsenic concentration of about 30 micrograms per liter (µg/L) that was higher than the MCL of 10 µg/L. However, total arsenic concentrations were higher than the HA of 2 µg/L in samples from another 12 of 79 wells (about 15 percent). Secondary maximum contaminant levels (SMCLs) were exceeded most frequently by pH and concentrations of iron and manganese. The pH was outside of the SMCL range of 6.5–8.5 in samples from 24 of 79 wells (30 percent), ranging from 5.5 to 9.2; more samples had pH values less than 6.5 than had pH values greater than 8.5. Total iron concentrations typically were much greater than dissolved iron concentrations, indicating substantial presence of iron in particulate phase, and exceeded the SMCL of 300 µg/L more often [35 of 79 samples (44 percent)] than dissolved iron concentrations [samples from 8 of 79 wells (10 percent)]. Total manganese concentrations exceeded the SMCL of 50 µg/L in samples from 31 of 79 wells (39 percent) and the HA of 300 µg/L in samples from 13 of 79 wells (about 16 percent). A few (1–2) samples had concentrations of sodium, chloride, sulfate, or TDS higher than the SMCLs of 60, 250, 250, and 500 mg/L, respectively. However, dissolved sodium concentrations were higher than the HA of 20 mg/L in samples from 15 of 79 wells (nearly 20 percent). Total coliform bacteria were detected in samples from 25 of 79 wells (32 percent) but Escherichia coli were not detected in any sample. Radon-222 activities ranged from 11 to 5,100 picocuries per liter (pCi/L), with a median of 1,440 pCi/L, and exceeded the proposed and the alternate proposed drinking-water standards of 300 and 4,000 pCi/L, respectively, in samples from 60 of 79 wells (75 percent) and in samples from 2 of 79 wells (3 percent), respectively.Groundwater samples from all wells were analyzed for dissolved methane by one contract laboratory that determined water from 19 of the 79 wells (24 percent) had concentrations of methane greater than the reporting level of 0.010 milligrams per liter (mg/L) with a maximum methane concentration of 2.5 mg/L. Methane concentrations in 18 replicate samples submitted to a second laboratory for dissolved gas and isotopic analysis generally were higher by as much as a factor of 2.7 from those determined by the first laboratory, indicating potential bias related to combined sampling and analytical methods, and therefore, caution needs to be used when comparing methane results determined by different methods. The isotopic composition of methane in 9 of 10 samples with sufficient dissolved methane (about 0.3 mg/L) for isotopic analysis is consistent with values reported for methane of microbial origin produced through carbon dioxide reduction; an isotopic shift in 1 or 2 samples may indicate subsequent methane oxidation. The low concentrations of ethane relative to methane in these samples further indicate that the methane may be of microbial origin. Groundwater samples with relatively elevated methane concentrations (near or greater than 0.3 mg/L) also had chemical compositions that differed in some respects from groundwater with relatively low methane concentrations (less than 0.3 mg/L) by having higher pH (greater than 8) and higher concentrations of sodium, lithium, boron, fluoride, arsenic, and bromide and chloride/bromide ratios indicative of mixing with a small amount of brine of probable natural occurrence.The spatial distribution of groundwater compositions differs by topographic setting and lithology and generally shows that (1) relatively dilute, slightly acidic, oxygenated, calcium-carbonate type waters tend to occur in the uplands underlain by the undivided Poplar Gap and Packerton members of the Catskill Formation in southwestern Pike County; (2) waters of near neutral pH with the highest amounts of hardness (calcium and magnesium) generally occur in areas of intermediate altitudes underlain by other members of the Catskill Formation; and (3) waters with pH values greater than 8, low oxygen concentrations, and the highest arsenic, sodium, lithium, bromide, and methane concentrations can be present in deep wells in uplands but most frequently occur in stream valleys, especially at low altitudes (less than about 1,200 feet above North American Vertical Datum of 1988) where groundwater may be discharging regionally, such as to the Delaware River in northern and eastern Pike County. Thus, the baseline assessment of groundwater quality in Pike County prior to gas-well development shows that shallow (less than about 1,000 feet deep) groundwater generally meets primary drinking-water standards for inorganic constituents but varies spatially, with methane and some constituents present in high concentrations in brine (and connate waters from gas and oil reservoirs) present at low to moderate concentrations in some parts of Pike County.

Baseline groundwater quality from 34 wells in Wayne County, Pennsylvania, 2011 and 2013

USGS Publications Warehouse

Sloto, Ronald A.

2014-01-01

Differences in groundwater chemistry were related to pH. Water with a pH greater than 7.6 generally had low dissolved oxygen concentrations, indicating reducing conditions in the aquifer. These high pH waters also had relatively elevated concentrations of methane, arsenic, boron, bromide, fluoride, lithium, and sodium but low concentrations of copper, nickel, and zinc. Water samples with a pH greater than 7.8 had methane concentrations equal to or greater than 0.04 mg/L.

Resolved 12CH2D2 and 13CH3D in CH4 as Sensitive Indicators of Disequilibrium and Equilibrium during Microbial Methane Cycling

NASA Astrophysics Data System (ADS)

Ash, J. L.; Egger, M.; Slomp, C. P.; Kohl, I. E.; Treude, T.; Rumble, D.; Young, E. D.

2016-12-01

The ability to measure the relative concentrations of at least two doubly-substituted rare isotopologues of gases with biogeochemical relevance provides new constraints on sources and sinks of these gases. In particular, as shown recently for O2, the use of two independent, rare isotopologues allows for detection of thermodynamic intra-species equilibrium and disequilibrium. Here, we report the first measurements of fully resolved 13CH3D and 12CH2D2 from natural samples of microbial methane gas. A suite of sedimentary methane samples from the Bornholm Basin in the Baltic Sea was collected during IODP Exp. 347. Sample depths range from 2-20 meters below seafloor (mbsf). Methane concentrations decrease with depth, and mcrA (a marker for methanogenesis and methanotropy) is present throughout. See Figure. Both Δ13CH3D and Δ12CH2D2 increase with depth as methane concentrations decrease with the shallowest samples exhibiting disequilibrium by up to 2‰ in Δ13CH3D and 13‰ in Δ12CH2D2 while the deepest samples approach isotopic thermodynamic equilibrium (marked by grey bars in Figure). The Fe-mediated anaerobic oxidation of methane (Fe-AOM) has been inferred in these sediments by geochemical modeling . Slow methane cycling by methanogensis and methanotrophy is likely responsible for the approach to isotopic bond order equilibrium in CH4 with depth, consistent with Fe-AOM. While axenic culturing experiments generate methane with large deficits in 12CH2D2 (reported at this meeting), these data from the Baltic Sea demonstrate that isotopic equilibrium can be achieved during microbial recycling of methane. In the absence of Δ12CH2D2, the Δ13CH3D values alone could be misinterpreted as representing gradients in temperature due perhaps to exothermic organic matter degradation. The combination of both mass-18 rare isotopologues of methane provides the means to distinguish equilibrium from disequilibrium and probe microbial methane cycling even where Δ13CH3D suggests reasonable temperatures.

UV production of methane from surface and sedimenting IDPs on Mars in light of REMS data and with insights for TGO

NASA Astrophysics Data System (ADS)

Moores, John E.; Smith, Christina L.; Schuerger, Andrew C.

2017-11-01

This paper refines model predictions for the production of methane from UV-irradiated interplanetary dust particles (IDPs) now that the Rover Environmental Monitoring Station (REMS) instrument onboard the Mars Science Laboratory (MSL) Rover has made the first measurements of the UV environment on the surface of Mars, at Gale Crater. Once these measurements are included in a UV radiative transfer model, we find that modelled UV sol-integrated energies across the planet are lower than pre-measurement estimates by 35% on average, considering all latitudes and seasons. This reduction, in turn, reduces the predicted production of methane from individual accreting IDPs, extending their lifetimes and increasing the surface concentration of organics that must accumulate in order to emit sufficient methane to balance the accretion of organic compounds to Mars. Emission from reasonable accumulations of IDPs could range up to ∼7.9 × 10-4 ppbv sol-1. Richer deposits of organic carbon at the surface may emit methane at no more than 3.9 ppbv sol-1. An examination of IDP-derived methane production during atmospheric settling indicates that no more than 0.32% of organic carbon from meteor streams may be deposited in the atmosphere. Thus, such a process cannot explain either the spikes observed in methane nor the low equilibrium values observed by MSL. Instead, this discrepancy may be explained if < 80 tons per year of organic carbon survives to the surface, the atmospheric lifetime of methane is < 110 years or the efficiency of the UV-CH4 process is <7%. Under the assumption of reduced carbon input cycling in the Martian system from these processes, both soil concentrations of organic carbon and atmospheric measurements of methane observed by MSL are consistent with the UV-CH4 process. This refinement of methane production from IDPs and its geographical and vertical distribution will be an important input for models attempting to understand the results to be derived from the Trace Gas Orbiter (TGO) mission that will map methane concentrations in the martian atmosphere in 2018 at 0.01 ppbv.

Background concentrations for high resolution satellite observing systems of methane

NASA Astrophysics Data System (ADS)

Benmergui, J. S.; Propp, A. M.; Turner, A. J.; Wofsy, S. C.

2017-12-01

Emerging satellite technologies promise to measure total column dry-air mole fractions of methane (XCH4) at resolutions on the order of a kilometer. XCH4 is linearly related to regional methane emissions through enhancements in the mixed layer, giving these satellites the ability to constrain emissions at unprecedented resolution. However, XCH4 is also sensitive to variability in transport of upwind concentrations (the "background concentration"). Variations in the background concentration are caused by synoptic scale transport in both the free troposphere and the stratosphere, as well as the rate of methane oxidation. Misspecification of the background concentration is aliased onto retrieved emissions as bias. This work explores several methods of specifying the background concentration for high resolution satellite observations of XCH4. We conduct observing system simulation experiments (OSSEs) that simulate the retrieval of emissions in the Barnett Shale using observations from a 1.33 km resolution XCH4 imaging satellite. We test background concentrations defined (1) from an external continental-scale model, (2) using pixels along the edge of the image as a boundary value, (3) using differences between adjacent pixels, and (4) using differences between the same pixel separated by one hour in time. We measure success using the accuracy of the retrieval, the potential for bias induced by misspecification of the background, and the computational expedience of the method. Pathological scenarios are given to each method.

Numerical Study of Contaminant Effects on Combustion of Hydrogen, Ethane, and Methane in Air

NASA Technical Reports Server (NTRS)

Lai, H. T.; Thomas, S. R.

1995-01-01

A numerical study was performed to assess the effects of vitiated air on the chemical kinetics of hydrogen, ethane, and methane combustion with air. A series of calculations in static reacting systems was performed, where the initial temperature was specified and reactions occurred at constant pressure. Three different types of test flow contaminants were considered: NP, H2O, and a combustion of H2O and CO2. These contaminants are present in the test flows of facilities used for hypersonic propulsion testing. The results were computed using a detailed reaction mechanism and are presented in terms of ignition and reaction times. Calculations were made for a wide range of contaminant concentrations, temperatures and pressures. The results indicate a pronounced kinetic effect over a range of temperatures, especially with NO contamination and, to a lesser degree, with H2O contamination. In all cases studied, CO2 remained kinetically inert, but had a thermodynamic effect on results by acting as a third body. The largest effect is observed with combustion using hydrogen fuel, less effect is seen with combustion of ethane, and little effect of contaminants is shown with methane combustion.

Numerical study of contaminant effects on combustion of hydrogen, ethane, and methane in air

NASA Technical Reports Server (NTRS)

Lai, H. T.; Thomas, S. R.

1995-01-01

A numerical study was performed to assess the effects of vitiated air on the chemical kinetics of hydrogen, ethane, and methane combustion with air. A series of calculations in static reacting systems was performed, where the initial temperature was specified and reactions occurred at constant pressure. Three different types of test flow contaminants were considered: NO, H2O, and a combination of H2O and CO2. These contaminants are present in the test flows of facilities used for hypersonic propulsion testing. The results were computed using a detailed reaction mechanism and are presented in terms of ignition and reaction times. Calculations were made for a wide range of contaminant concentrations, temperatures and pressures. The results indicate a pronounced kinetic effect over a range of temperatures, especially with NO contamination and, to a lesser degree, with H2O contamination. In all cases studied, CO2 remained kinetically inert, but had a thermodynamically effect on results by acting as a third body. The largest effect is observed with combustion using hydrogen fuel, less effect is seen with combustion of ethane, and little effect of contaminants is shown with methane combustion.

Seasonal Oxygen Dynamics in a Thermokarst Bog in Interior Alaska: Implications for Rates of Methane Oxidation

NASA Astrophysics Data System (ADS)

Neumann, R. B.; Moorberg, C.; Wong, A.; Waldrop, M. P.; Turetsky, M. R.

2015-12-01

Methane is a potent greenhouse gas, and wetlands represent the largest natural source of methane to the atmosphere. However, much of the methane generated in anoxic wetlands never gets emitted to the atmosphere; up to >90% of generated methane can get oxidized to carbon dioxide. Thus, oxidation is an important methane sink and changes in the rate of methane oxidation can affect wetland methane emissions. Most methane is aerobically oxidized at oxic-anoxic interfaces where rates of oxidation strongly depend on methane and oxygen concentrations. In wetlands, oxygen is often the limiting substrate. To improve understanding of belowground oxygen dynamics and its impact on methane oxidation, we deployed two planar optical oxygen sensors in a thermokarst bog in interior Alaska. Previous work at this site indicated that, similar to other sites, rates of methane oxidation decrease over the growing season. We used the sensors to track spatial and temporal patterns of oxygen concentrations over the growing season. We coupled these in-situ oxygen measurements with periodic oxygen injection experiments performed against the sensor to quantify belowground rates of oxygen consumption. We found that over the season, the thickness of the oxygenated water layer at the peatland surface decreased. Previous research has indicated that in sphagnum-dominated peatlands, like the one studied here, rates of methane oxidation are highest at or slightly below the water table. It is in these saturated but oxygenated locations that both methane and oxygen are available. Thus, a seasonal reduction in the thickness of the oxygenated water layer could restrict methane oxidation. The decrease in thickness of the oxygenated layer coincided with an increase in the rate of oxygen consumption during our oxygen injection experiments. The increase in oxygen consumption was not explained by temperature; we infer it was due to an increase in substrate availability for oxygen consuming reactions and/or abundance of key microbial populations. Together, the data provide an explanation for the seasonal decrease in methane oxidation: rates of oxygen consumption increase over the season, which decreases the amount of oxygen dissolved in porewater at the peatland surface and reduces rates of methane oxidation.

Internal reforming characteristics of cermet supported solid oxide fuel cell using yttria stabilized zirconia fed with partially reformed methane

NASA Astrophysics Data System (ADS)

Momma, Akihiko; Takano, Kiyonami; Tanaka, Yohei; Negishi, Akira; Kato, Ken; Nozaki, Ken; Kato, Tohru; Ichigi, Takenori; Matsuda, Kazuyuki; Ryu, Takashi

In order to investigate the internal reforming characteristics in a cermet supported solid oxide fuel cell (SOFC) using YSZ as the electrolyte, the concentration profiles of the gaseous species along the gas flow direction in the anode were measured. Partially reformed methane using a pre-reformer kept at a constant temperature is supplied to the center of the cell which is operated with a seal-less structure at the gas outlet. The anode gas is sucked in via silica capillaries to the initially evacuated gas tanks. The process is simultaneously carried out using five sampling ports. The sampled gas is analyzed by a gas chromatograph. Most of the measurements are made at the cell temperature (T cell) of 750 °C and at various temperatures of the pre-reformer (T ref) with various fuel utilizations (U f) of the cell. The composition of the fuel at the inlet of the anode was confirmed to be almost the same as that theoretically calculated assuming equilibrium at the temperature of the pre-reformer. The effect of internal reforming in the anode is clearly observed as a steady decrease in the methane concentration along the flow axis. The effect of the water-gas shift reaction is also observed as a decrease in the CO 2 concentration and an increase of CO concentration around the gas inlet region, as the water-gas shift reaction inversely proceeds when T cell is higher than T ref. The diffusion of nitrogen from the seal-less outermost edge is observed, and the diffusion is confirmed to be more significant as U f decreases. The observations are compared with the results obtained by the SOFC supported by lanthanum gallate electrolyte. With respect to the internal reforming performance, the cell investigated here is found to be more effective when compared to the previously reported electrolyte supported cell.

Methane emissions, body composition, and rumen fermentation traits of beef heifers differing in residual feed intake.

PubMed

Fitzsimons, C; Kenny, D A; Deighton, M H; Fahey, A G; McGee, M

2013-12-01

This study examined the relationship of residual feed intake (RFI) and performance with methane emissions, rumen fermentation, and digestion in beef heifers. Individual DMI and growth performance were measured for 22 Simmental heifers (mean initial BW 449 kg, SD = 46.2 kg) offered grass silage ad libitum for 120 d. Ultrasonically scanned muscle and fat depth, BCS, muscularity score, skeletal measurements, blood variables, rumen fermentation (via stomach tube), and total tract digestibility (indigestible marker) were measured. Methane production was estimated using the sulfur hexafluoride tracer gas technique over two 5-d periods beginning on d 20 and 75 of the RFI measurement period. Phenotypic RFI was calculated as actual DMI minus expected DMI. The residuals of the regression of DMI on ADG and midtest metabolic body weight, using all heifers, were used to compute individual RFI coefficients. Heifers were ranked by RFI and assigned to low (efficient), medium, or high (inefficient) groupings. Overall ADG and DMI were 0.58 kg (SD = 0.18) and 7.40 kg (SD = 0.72), respectively. High-RFI heifers consumed 9 and 15% more (P < 0.05) than medium- and low-RFI groups, respectively. Body weight, growth, skeletal, and composition traits did not differ (P > 0.05) between low- and high-RFI groups. High-RFI heifers had higher concentrations of plasma glucose (6%) and urea (13%) and lower concentrations of plasma creatinine (9%) than low-RFI heifers (P < 0.05). Rumen pH and apparent in vivo digestibility did not differ (P > 0.05) between RFI groups, although acetate:propionate ratio was lowest (P = 0.07) for low-RFI (3.5) and highest for high-RFI (4.6) heifers. Methane production expressed as grams per day or grams per kilogram metabolic body weight was greater (P < 0.05) for high (297 g/d and 2.9 g/kg BW0.75) compared with low (260 g/d and 2.5 g/kg BW0.75) RFI heifers, with medium (275 g/d and 2.7 g/kg BW0.75) RFI heifers being intermediate. Regression analysis indicated that a 1 kg DM/d increase in RFI was associated with a 23 g/d increase (P = 0.09) in methane emissions. Results suggest that improved RFI will reduce methane emissions without affecting productivity of growing beef cattle.

40 CFR 60.614 - Test methods and procedures.

Code of Federal Regulations, 2012 CFR

2012-07-01

... or TOC (less methane and ethane) reduction efficiency shall be prior to the inlet of the control... TOC (minus methane and ethane), dry basis, ppm by volume. %O2d=Concentration of O2, dry basis, percent.... (ii) The emission reduction (R) of TOC (minus methane and ethane) shall be determined using the...

40 CFR 60.664 - Test methods and procedures.

Code of Federal Regulations, 2012 CFR

2012-07-01

... (less methane and ethane) reduction efficiency shall be prior to the inlet of the control device and... methane and ethane), dry basis, ppm by volume. %O2d=Concentration of O2, dry basis, percent by volume. (4... emission reduction (R) of TOC (minus methane and ethane) shall be determined using the following equation...

77 FR 38667 - Petitions for Modification of Application of Existing Mandatory Safety Standards

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-28

... request. (d) A qualified person as defined in 30 CFR 75.151 will continuously monitor for methane.... (e) Nonpermissible surveying equipment will not be used if methane is detected in concentrations at or above one percent for the area being surveyed. When methane is detected at such levels while the...

77 FR 19722 - Petitions for Modification of Application of Existing Mandatory Safety Standards

Federal Register 2010, 2011, 2012, 2013, 2014

2012-04-02

... request. (d) A qualified person as defined in 30 CFR 75.151 will continuously monitor for methane.... (e) Nonpermissible surveying equipment will not be used if methane is detected in concentrations at or above one percent for the area being surveyed. When methane is detected at such levels while the...

77 FR 37926 - Petitions for Modification of Application of Existing Mandatory Safety Standards

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-25

... defined in 30 CFR 75.151 will continuously monitor for methane immediately before and during the use of... electronic testing and diagnostic equipment will not be used if methane is detected in concentrations at or above one percent. When one percent or more methane is detected while the nonpermissible electronic...

78 FR 3032 - Petitions for Modification of Application of Existing Mandatory Safety Standards

Federal Register 2010, 2011, 2012, 2013, 2014

2013-01-15

... request. (d) A qualified person as defined in 30 CFR 75.151 will continuously monitor for methane.... (e) Nonpermissible surveying equipment will not be used if methane is detected in concentrations at or above one percent for the area being surveyed. When methane is detected at such levels while the...

78 FR 55297 - Petitions for Modification of Application of Existing Mandatory Safety Standards

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-10

... request. (d) A qualified person as defined in 30 CFR 75.151 will continuously monitor for methane.... (e) Nonpermissible surveying equipment will not be used if methane is detected in concentrations at or above one percent for the area being surveyed. When methane is detected at such levels while the...

77 FR 38324 - Petitions for Modification of Application of Existing Mandatory Safety Standards

Federal Register 2010, 2011, 2012, 2013, 2014

2012-06-27

... person as defined in 30 CFR 75.151 will continuously monitor for methane immediately before and during... surveying equipment will not be used if methane is detected in concentrations at or above one percent for the area being surveyed. When methane is detected at such levels while the nonpermissible surveying...

77 FR 14430 - Petitions for Modification of Application of Existing Mandatory Safety Standards

Federal Register 2010, 2011, 2012, 2013, 2014

2012-03-09

....151 will continuously monitor for methane immediately before and during the use of non-permissible... used if methane is detected in concentrations at or above one percent for the area being surveyed. When methane is detected at such levels while the non- permissible surveying equipment is being used, the...

Chemical composition and methane yield of reed canary grass as influenced by harvesting time and harvest frequency.

PubMed

Kandel, Tanka P; Sutaryo, Sutaryo; Møller, Henrik B; Jørgensen, Uffe; Lærke, Poul E

2013-02-01

This study examined the influence of harvest time on biomass yield, dry matter partitioning, biochemical composition and biological methane potential of reed canary grass harvested twice a month in one-cut (OC) management. The regrowth of biomass harvested in summer was also harvested in autumn as a two-cut management with (TC-F) or without (TC-U) fertilization after summer harvest. The specific methane yields decreased significantly with crop maturity that ranged from 384 to 315 and from 412 to 283 NL (normal litre) (kgVS)(-1) for leaf and stem, respectively. Approximately 45% more methane was produced by the TC-F management (5430Nm(3)ha(-1)) as by the OC management (3735Nm(3)ha(-1)). Specific methane yield was moderately correlated with the concentrations of fibre components in the biomass. Larger quantity of biogas produced at the beginning of the biogas assay from early harvested biomass was to some extent off-set by lower concentration of methane. Copyright © 2012 Elsevier Ltd. All rights reserved.

Quantitative modeling of the rise in atmospheric oxygen

NASA Astrophysics Data System (ADS)

Claire, Mark W.

The abrupt rise of molecular oxygen in Earth's atmosphere approximately 2.4 billion years ago was perhaps the most profound event in Earth's history after the evolution of life itself. Biogeochemical cycles in Earth's atmosphere, ocean, and crust were completely reorganized and it also likely marked the first moment when our planet could be deemed "inhabited" across interstellar space via identification of biogenically produced O 2 and O 3 in a spectrum of Earth's atmosphere. This dissertation explores the "Great Oxidation Event" via numerical modeling of evolving ancient atmospheres. In creating a self-consistent description of evolving redox fluxes in the Earth system, we reach the following conclusions. After the evolution of oxygenic photosynthesis, the atmosphere has two primary stable states--one is methane- rich and produces mass-independent fractionation of sulfur isotopes (MIF-S), and one is oxygen-rich and does not produce MIF-S. These two stable states are separated by only a few percent in the fluxes of O 2 and CH 4 needed to sustain them. The atmosphere evolves rapidly from one state to the other when the net flux of reductants drops below the net flux of oxidants into the atmosphere. The transition between the two states - "the rise of oxygen" - is only feasible once methane levels drop below ~50 ppm. We show numerically that hydrogen escape can drive irreversible oxidation of Earth's crust, leading to decreasing CH 4 concentrations over long timescales. We argue that the disappearance of the MIF-S signal is better described as recording a collapse of atmospheric CH 4 , rather than the appearance of O 2 . As CH 4 levels decrease, a positive feedback between oxidative weathering, oceanic sulfate concentrations, and the anaerobic oxidation of methane further drives atmospheric instability. Once a critical threshold in CH 4 concentration is overcome, the atmosphere transitions from an anoxic to oxic state on the timescale of 10 3 years. The post-transition levels of O 2 and CH 4 and the global climate are strongly driven by biological forcing. Considering the events of 2.4 Ga as a "Great Collapse of Methane" helps explain the initiation of Snowball Earth, the disappearance of MIF-S, and the rise of oxygen.

Effect of Initial Mixture Temperature on Flame Speed of Methane-Air, Propane-Air, and Ethylene-Air Mixtures

NASA Technical Reports Server (NTRS)

Dugger, Gordon L

1952-01-01

Flame speeds based on the outer edge of the shadow cast by the laminar Bunsen cone were determined as functions of composition for methane-air mixtures at initial mixture temperatures ranging from -132 degrees to 342 degrees c and for propane-air and ethylene-air mixtures at initial mixture temperatures ranging from -73 degrees to 344 degrees c. The data showed that maximum flame speed increased with temperature at an increasing rate. The percentage change in flame speed with change in initial temperature for the three fuels followed the decreasing order, methane, propane, and ethylene. Empirical equations were determined for maximum flame speed as a function of initial temperature over the temperature range covered for each fuel. The observed effect of temperature on flame speed for each of the fuels was reasonably well predicted by either the thermal theory as presented by Semenov or the square-root law of Tanford and Pease.

Spatially and Temporally Resolved Atomic Oxygen Measurements in Short Pulse Discharges by Two Photon Laser Induced Fluorescence

NASA Astrophysics Data System (ADS)

Lempert, Walter; Uddi, Mruthunjaya; Mintusov, Eugene; Jiang, Naibo; Adamovich, Igor

2007-10-01

Two Photon Laser Induced Fluorescence (TALIF) is used to measure time-dependent absolute oxygen atom concentrations in O2/He, O2/N2, and CH4/air plasmas produced with a 20 nanosecond duration, 20 kV pulsed discharge at 10 Hz repetition rate. Xenon calibrated spectra show that a single discharge pulse creates initial oxygen dissociation fraction of ˜0.0005 for air like mixtures at 40-60 torr total pressure. Peak O atom concentration is a factor of approximately two lower in fuel lean (φ=0.5) methane/air mixtures. In helium buffer, the initially formed atomic oxygen decays monotonically, with decay time consistent with formation of ozone. In all nitrogen containing mixtures, atomic oxygen concentrations are found to initially increase, for time scales on the order of 10-100 microseconds, due presumably to additional O2 dissociation caused by collisions with electronically excited nitrogen. Further evidence of the role of metastable N2 is demonstrated from time-dependent N2 2^nd Positive and NO Gamma band emission spectroscopy. Comparisons with modeling predictions show qualitative, but not quantitative, agreement with the experimental data.

Groundwater quality for 75 domestic wells in Lycoming County, Pennsylvania, 2014

USGS Publications Warehouse

Gross, Eliza L.; Cravotta, Charles A.

2017-03-06

Groundwater is a major source of drinking water in Lycoming County and adjacent counties in north-central and northeastern Pennsylvania, which are largely forested and rural and are currently undergoing development for hydrocarbon gases. Water-quality data are needed for assessing the natural characteristics of the groundwater resource and the potential effects from energy and mineral extraction, timber harvesting, agriculture, sewage and septic systems, and other human influences.This report, prepared in cooperation with Lycoming County, presents analytical data for groundwater samples from 75 domestic wells sampled throughout Lycoming County in June, July, and August 2014. The samples were collected using existing pumps and plumbing prior to any treatment and analyzed for physical and chemical characteristics, including nutrients, major ions, metals and trace elements, volatile organic compounds, gross-alpha particle and gross beta-particle activity, uranium, and dissolved gases, including methane and radon-222.Results indicate groundwater quality generally met most drinking-water standards, but that some samples exceeded primary or secondary maximum contaminant levels (MCLs) for arsenic, iron, manganese, total dissolved solids (TDS), chloride, pH, bacteria, or radon-222. Arsenic concentrations were higher than the MCL of 10 micrograms per liter (µg/L) in 9 of the 75 (12 percent) well-water samples, with concentrations as high as 23.6 μg/L; arsenic concentrations were higher than the health advisory level (HAL) of 2 μg/L in 23 samples (31 percent). Total iron concentrations exceeded the secondary maximum contaminant level (SMCL) of 300 μg/L in 20 of the 75 samples. Total manganese concentrations exceeded the SMCL of 50 μg/L in 20 samples and the HAL of 300 μg/L in 2 of those samples. Three samples had chloride concentrations that exceeded the SMCL of 250 milligrams per liter (mg/L); two of those samples exceeded the SMCL of 500 mg/L for TDS. The pH ranged from 5.3 to 9.15 and did not meet the SMCL range of 6.5 to 8.5 in 22 samples, with 17 samples having a pH less than 6.5 and 8 samples having pH greater than 8.5. Generally, the samples that had elevated TDS, chloride, or arsenic concentrations had high pH.Total coliform bacteria were detected in 39 of 75 samples (52 percent), with Escherichia coli detected in 10 of those 39 samples. Radon-222 activities ranged from non-detect to 7,420 picocuries per liter (pCi/L), with a median of 863 pCi/L, and exceeded the proposed drinking-water standard of 300 pCi/L in 50 (67 percent) of the 75 samples; radon-222 activities were higher than the alternative proposed standard of 4,000 pCi/L in 3 samples.Water from 15 of 75 (20 percent) wells had concentrations of methane greater than the reporting level of 0.01 mg/L; detectable methane concentrations ranged from 0.04 to 16.8 mg/L. Two samples had methane concentrations (13.1 and 16.8 mg/L) exceeding the action level of 7 mg/L. Low levels of ethane (up to 0.12 mg/L) were present in the five samples with the highest methane concentrations (near or above 1 mg/L) that were analyzed for hydrocarbon compounds and isotopic composition. The isotopic composition of methane in four of these groundwater samples, from the Catskill and Lock Haven Formations and the Hamilton Group, have sample carbon isotopic ratio delta values (carbon-13/carbon-12) ranging from –42.36 to –36.08 parts per thousand (‰) and hydrogen isotopic ratio delta values (deuterium/protium) ranging from –212.0 to –188.4 ‰, which are consistent with the isotopic compositions reported for mud-gas logging samples from these geologic units and a thermogenic source of the methane. However, the isotopic composition and ratios of methane to ethane in a fifth sample indicate the methane in that sample may be of microbial origin that subsequently underwent oxidation. The fifth sample had the highest concentration of methane, 16.8 mg/L, with an carbon isotopic ratio delta values of -50.59 ‰ and a hydrogen isotopic ratio delta values of -209.7 ‰.The six well-water samples with the highest methane concentrations also had among the highest pH values (8.25 to 9.15) and elevated concentrations of sodium, lithium, boron, fluoride, arsenic, and bromide. Relatively elevated concentrations of some other constituents, such as barium, strontium, and chloride, commonly were present in, but not limited to, those well-water samples with elevated methane.Three of the six groundwater samples with the highest methane concentrations had chloride/bromide ratios that indicate mixing with a small amount of brine (0.02 percent or less) similar in composition to those reported at undetermined depth below the freshwater aquifer and for gas and oil well brines in Pennsylvania. The sample with the highest methane concentration and most other samples with low methane concentrations (less than about 1 mg/L) have chloride/bromide ratios that indicate predominantly anthropogenic sources of chloride, such as road-deicing salt, septic systems, and (or) animal waste. Brines that are naturally present may originate from deeper parts of the aquifer system, while anthropogenic sources are more likely to affect shallow groundwater because they occur on or near the land-surface.The spatial distribution of groundwater compositions generally indicate that (1) uplands along the western border of Lycoming County usually have dilute, slightly acidic oxygenated, calcium-bicarbonate type waters; (2) intermediate altitudes or areas of carbonate bedrock usually have water of near neutral pH, with highest amounts of hardness (calcium and magnesium); (3) stream valleys, low elevations where groundwater may be discharging, and deep wells in uplands usually have water with pH values greater than 8 and highest arsenic, sodium, lithium, bromide concentrations. Geochemical modeling indicated that for samples with elevated pH, sodium, lithium, bromide, and alkalinity, the water chemistry could have resulted by dissolution of calcite (calcium carbonate) combined with cation-exchange and mixing with a small amount of brine. Through cation-exchange reactions between water and bedrock, which are equivalent to processes in a water softener, calcium ions released by calcite dissolution are exchanged for sodium ions on clay minerals. Thus, the assessment of groundwater quality in Lycoming County indicates groundwater is generally of good quality, but various parts of Lycoming County can have groundwater with low to moderate concentrations of methane and other constituents that appear in naturally present brine and produced waters from gas and oil wells at high concentrations."

The distribution of methane in groundwater in Alberta (Canada) and associated aqueous geochemistry conditions

NASA Astrophysics Data System (ADS)

Humez, Pauline; Mayer, Bernhard; Nightingale, Michael; Becker, Veith; Kingston, Andrew; Taylor, Stephen; Millot, Romain; Kloppmann, Wolfram

2016-04-01

Development of unconventional energy resources such as shale gas and coalbed methane has generated some public concern with regard to the protection of groundwater and surface water resources from leakage of stray gas from the deep subsurface. In terms of environmental impact to and risk assessment of shallow groundwater resources, the ultimate challenge is to distinguish: (a) natural in-situ production of biogenic methane, (b) biogenic or thermogenic methane migration into shallow aquifers due to natural causes, and (c) thermogenic methane migration from deep sources due to human activities associated with the exploitation of conventional or unconventional oil and gas resources. We have conducted a NSERC-ANR co-funded baseline study investigating the occurrence of methane in shallow groundwater of Alberta (Canada), a province with a long record of conventional and unconventional hydrocarbon exploration. Our objective was to assess the occurrence and sources of methane in shallow groundwaters and to also characterize the hydrochemical environment in which the methane was formed or transformed through redox processes. Ultimately our aim was to determine whether methane was formed in-situ or whether it migrated from deeper formations into shallow aquifers. Combining hydrochemical and dissolved and free geochemical gas data from 372 groundwater samples obtained from 186 monitoring wells of the provincial groundwater observation well network (GOWN) in Alberta, it was found that methane is ubiquitous in groundwater in Alberta and is predominantly of biogenic origin. The highest concentrations of dissolved biogenic methane (> 0.01 mM or > 0.2 mg/L), characterized by δ13CCH4 values < -55‰, occurred in anoxic Na-Cl, Na-HCO3 and Na-HCO3-Cl type groundwater with negligible concentrations of nitrate and sulfate suggesting that methane was formed in-situ under methanogenic conditions consistent with the redox ladder concept. Despite quite variable gas concentrations and a wide range of δ13CCH4 values in baseline groundwater samples, no conclusive evidence was found for deep thermogenic gas that had migrated in significant amounts into shallow aquifers either naturally or via anthropogenically induced pathways. This study shows that the combined interpretation of aqueous geochemistry data in concert with the chemical and isotopic composition of dissolved and/or free gas can yield unprecedented insights into formation or migration of methane in shallow groundwater. This enables the assessment of cross-formational methane migration and provides an understanding of alkane gas sources and pathways necessary for a stringent baseline definition in the context of current and future unconventional hydrocarbon exploration and exploitation.

40 CFR Figure 1 to Subpart G of... - Definitions of Terms Used in Wastewater Equations

Code of Federal Regulations, 2010 CFR

2010-07-01

... wastewater, ppmw. CG=Concentration of TOC (minus methane and ethane) or total organic hazardous air pollutants, in vented gas stream, dry basis, ppmv. CGc=Concentration of TOC or organic hazardous air... flow rate of vented gas stream, dry standard, m3/min. QMG=Mass flowrate of TOC (minus methane and...

Contribution of Changing Sources and Sinks to the Growth Rate of Atmospheric Methane Concentrations for the Last Two Decades

NASA Technical Reports Server (NTRS)

Matthews, Elaine; Walter, B.; Bogner, J.; Sarma, D.; Portney, B.; Hansen, James (Technical Monitor)

2000-01-01

In situ measurements of atmospheric methane concentrations begun in the early 1980s show decadal trends, as well as large interannual variations, in growth rate. Recent research indicates that while wetlands can explain several of the large growth anomalies for individual years, the decadal trend may be the combined effect of increasing sinks, due to increases in tropospheric OH, and stabilizing sources. We discuss new 20-year histories of annual, global source strengths for all major methane sources, i.e., natural wetlands, rice cultivation, ruminant animals, landfills, fossil fuels, and biomass burning, and present estimates of the temporal pattern of the sink required to reconcile these sources and atmospheric concentrations over the time period. Analysis of the individual emission sources, together with model-derived estimates of the OH sink strength, indicates that the growth rate of atmospheric methane observed over the last 20 years can only be explained by a combination of changes in source emissions and an increasing tropospheric sink.

Evaluation of methane sources in groundwater in northeastern Pennsylvania.

PubMed

Molofsky, Lisa J; Connor, John A; Wylie, Albert S; Wagner, Tom; Farhat, Shahla K

2013-01-01

Testing of 1701 water wells in northeastern Pennsylvania shows that methane is ubiquitous in groundwater, with higher concentrations observed in valleys vs. upland areas and in association with calcium-sodium-bicarbonate, sodium-bicarbonate, and sodium-chloride rich waters--indicating that, on a regional scale, methane concentrations are best correlated to topographic and hydrogeologic features, rather than shale-gas extraction. In addition, our assessment of isotopic and molecular analyses of hydrocarbon gases in the Dimock Township suggest that gases present in local water wells are most consistent with Middle and Upper Devonian gases sampled in the annular spaces of local gas wells, as opposed to Marcellus Production gas. Combined, these findings suggest that the methane concentrations in Susquehanna County water wells can be explained without the migration of Marcellus shale gas through fractures, an observation that has important implications for understanding the nature of risks associated with shale-gas extraction. © 2013, Cabot Oil and Gas Corporation. Groundwater © 2013, National GroundWater Association.

Localization and Quantification of Trace-gas Fugitive Emissions Using a Portable Optical Spectrometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Eric; Teng, Chu; van Kessel, Theodore

We present a portable optical spectrometer for fugitive emissions monitoring of methane (CH4). The sensor operation is based on tunable diode laser absorption spectroscopy (TDLAS), using a 5 cm open path design, and targets the 2ν3 R(4) CH4 transition at 6057.1 cm-1 (1651 nm) to avoid cross-talk with common interfering atmospheric constituents. Sensitivity analysis indicates a normalized precision of 2.0 ppmv∙Hz-1/2, corresponding to a noise-equivalent absorption (NEA) of 4.4×10-6 Hz-1/2 and minimum detectible absorption (MDA) coefficient of αmin = 8.8×10-7 cm-1∙Hz-1/2. Our TDLAS sensor is deployed at the Methane Emissions Technology Evaluation Center (METEC) at Colorado State University (CSU) formore » initial demonstration of single-sensor based source localization and quantification of CH4 fugitive emissions. The TDLAS sensor is concurrently deployed with a customized chemi-resistive metal-oxide (MOX) sensor for accuracy benchmarking, demonstrating good visual correlation of the concentration time-series. Initial angle-of-arrival (AOA) results will be shown, and development towards source magnitude estimation will be described.« less

Activity and diversity of aerobic methanotrophs in a coastal marine oxygen minimum zone

NASA Astrophysics Data System (ADS)

Padilla, C. C.; Bristow, L. A.; Sarode, N. D.; Garcia-Robledo, E.; Girguis, P. R.; Thamdrup, B.; Stewart, F. J.

2016-02-01

The pelagic ocean is a sink for the potent greenhouse gas methane, with methane consumption regulated primarily by aerobic methane-oxidizing bacteria (MOB). Marine oxygen minimum zones (OMZs) contain the largest pool of pelagic methane in the oceans but remain largely unexplored for their potential to harbor MOB communities and contribute to methane cycling. Here, we present meta-omic and geochemical evidence that aerobic MOB are present and active in a coastal OMZ, in Golfo Dulce, Costa Rica. Oxygen concentrations were < 50 nM below 85 m, and sulfide accumulated below 140 m, with methane concentrations ranging from trace levels above the oxycline to 78 nM at 180 m. The upper OMZ (90 m) was characterized by an abundant MOB and methylotroph community representing diverse lineages of the Methylophilaceae, Methylophaga, and Methylococcales. Of these, Type I methanotrophs of the Order Methylococcales dominated , representing >5% of total 16S rRNA genes and >19% of 16S rRNA transcripts. This peak in ribosomal abundance and activity was affiliated with methane oxidation rates of 2.6 ± 0.7 nM d-1, measured in seawater incubations with estimated O2 concentrations of 50 nM. Rates fell to zero with the addition of acetylene, an inhibitor of aerobic methanotrophy. In contrast, methane oxidation was below detection at lower depths in the OMZ (100 m and 120 m). Metatranscriptome sequencing indicated a peak at 90 m in the expression of pathways essential to Methylococcales, including aerobic methanotrophy and the RuMP pathway of carbon assimilation, as well as the serine pathway of Type II methanotrophs. Preliminary analysis of single-cell genomes suggests distinct adaptations by Methylococcales from the Golfo Dulce, helping explain the persistence of putative aerobic methanotrophs under very low oxygen in this OMZ. Taken together, these data suggest the boundary layers of OMZs, despite extreme oxygen depletion, are a niche for aerobic MOBs and therefore potentially important zones of pelagic methane loss.

Laboratory formation of non-cementing, methane hydrate-bearing sands

USGS Publications Warehouse

Waite, William F.; Bratton, Peter M.; Mason, David H.

2011-01-01

Naturally occurring hydrate-bearing sands often behave as though methane hydrate is acting as a load-bearing member of the sediment. Mimicking this behavior in laboratory samples with methane hydrate likely requires forming hydrate from methane dissolved in water. To hasten this formation process, we initially form hydrate in a free-gas-limited system, then form additional hydrate by circulating methane-supersaturated water through the sample. Though the dissolved-phase formation process can theoretically be enhanced by increasing the pore pressure and flow rate and lowering the sample temperature, a more fundamental concern is preventing clogs resulting from inadvertent methane bubble formation in the circulation lines. Clog prevention requires careful temperature control throughout the circulation loop.

Variability of methane fluxes over high latitude permafrost wetlands

NASA Astrophysics Data System (ADS)

Serafimovich, Andrei; Hartmann, Jörg; Larmanou, Eric; Sachs, Torsten

2013-04-01

Atmospheric methane plays an important role in the global climate system. Due to significant amounts of organic material stored in the upper layers of high latitude permafrost wetlands and a strong Arctic warming trend, there is concern about potentially large methane emissions from Arctic and sub-Arctic areas. The quantification of methane fluxes and their variability from these regions therefore plays an important role in understanding the Arctic carbon cycle and changes in atmospheric methane concentrations. However, direct measurements of methane fluxes in permafrost regions are sparse, very localized, inhomogeneously distributed in space, and thus difficult to use for accurate model representation of regional to global methane contributions from the Arctic. We aim to contribute to reducing uncertainty and improve spatial coverage and spatial representativeness of flux estimates by using airborne eddy covariance measurements across large areas. The research aircraft POLAR 5 was equipped with a turbulence nose boom and a fast response methane analyzer and served as the platform for measurements of methane emissions. The measuring campaign was carried out from 28 June to 10 July 2012 across the entire North Slope of Alaska and the Mackenzie Delta in Canada. The supplemented simulations from the Weather Research and Forecasting (WRF) model exploring the dynamics of the atmospheric boundary layer were used to analyze high methane concentrations occasionally observed within the boundary layer with a distinct drop to background level above. Strong regional differences were detected over both investigated areas showing the non-uniform distribution of methane sources. In order to cover the whole turbulent spectrum and at the same time to resolve methane fluxes on a regional scale, different integration paths were analyzed and validated through spectral analysis. Methane emissions measured over the Mackenzie Delta were higher and generally more variable in space, especially in the outer Delta with known geogenic methane seepage. On the North Slope, methane fluxes were larger in the western part than in the central and eastern parts. The obtained results are essential for the advanced, scale dependent quantification of methane emissions. Our contribution will present an overview of the experiment as well as preliminary results from more than 52 flight hours over high latitude permafrost wetlands.

Methane Fluxes at the Tree Stem, Soil, and Ecosystem-scales in a Cottonwood Riparian Forest

NASA Astrophysics Data System (ADS)

Flanagan, L. B.; Nikkel, D. J.; Scherloski, L. M.; Tkach, R. E.; Rood, S. B.

2017-12-01

Trees can emit methane to the atmosphere that is produced by microbes inside their decaying stems or by taking up and releasing methane that is produced by microbes in adjacent, anoxic soil layers. The significance of these two methane production pathways for possible net release to the atmosphere depends on the magnitude of simultaneous oxidation of atmospheric methane that occurs in well-aerated, shallow soil zones. In order to quantify the significance of these processes, we made methane flux measurements using the eddy covariance technique at the ecosystem-scale and via chamber-based methods applied on the soil surface and on tree stems in a riparian cottonwood ecosystem in southern Alberta that was dominated by Populus tree species and their natural hybrids. Tree stem methane fluxes varied greatly among individual Populus trees and changed seasonally, with peak growing season average values of 4 nmol m-2 s-1 (tree surface area basis). When scaled to the ecosystem, the tree stem methane emissions (0.9 nmol m-2 s-1, ground area basis) were slightly higher than average soil surface methane uptake rates (-0.8 nmol m-2 s-1). In addition, we observed regular nighttime increases in methane concentration within the forest boundary layer (by 300 nmol mol-1 on average at 22 m height during July). The majority of the methane concentration build-up was flushed from the ecosystem to the well-mixed atmosphere, with combined eddy covariance and air column storage fluxes reaching values of 70-80 nmol m-2 s-1 for approximately one hour after sunrise. Daily average net methane emission rates at the ecosystem-scale were 4.4 nmol m-2 s-1 during July. Additional lab studies demonstrated that tree stem methane was produced via the CO2-reduction pathway, as tissue in the central stem of living Populus trees was being decomposed. This study demonstrated net methane emission from an upland, cottonwood forest ecosystem, resulting from microbe methane production in tree stems that exceeded simultaneous oxidation of atmospheric methane in shallow, aerobic soils.

Methane emissions from termites - landscape level estimates and methods of measurement

NASA Astrophysics Data System (ADS)

Jamali, Hizbullah; Livesley, Stephen J.; Hutley, Lindsay B.; Arndt, Stefan K.

2013-04-01

Termites contribute between <5 and 19% of the global methane emissions. These estimates have large uncertainties because of the limited number of field-based studies and species investgated, as well as issues of diurnal and seasonal variations. We measured methane fluxes from four common mound-building termite species diurnally and seasonally in tropical savannas in the Northern Territory, Australia. Our results showed that there were significant diel and seasonal variations of methane emissions from termite mounds and we observed large species-specific differences. On a diurnal basis, methane fluxes were least at the coolest time of the day and greatest at the warmest for all species for both wet and dry seasons. We observed a strong and significant positive correlation between methane flux and mound temperature for all species. Fluxes in the wet season were 5-26-fold greater than those in the dry season and this was related to population dynamics of the termites. We observed significant relationships between mound methane flux and mound carbon dioxide flux, enabling the prediction of methane flux from measured carbon dioxide flux. However, these relationships were clearly termite species specific. We also determined significant relationships between mound flux and gas concentration inside mound, for both gases, and for all termite species, thereby enabling the prediction of flux from measured mound internal gas concentration. However, these relationships were also termite species specific. Consequently, there was no generic relationship that would enable an easier prediction of methane flux from termite mounds. On a landscape scale we estimated that termites were a methane source of +0.24 kg methane-C ha-1 year-1 whilst savanna soils were a methane sink of 1.14 kg methane-C ha-1 year-1. Termites therefore only offset 21% of methane consumed by savanna soil resulting in net sink strength of -0.90 kg methane-C ha-1 year-1 for these savannas. Assuming a similar contribution of termites in the savannas and tropical rain forests worldwide, termites would globally produce around 27 Tg CO2-e year-1, which is 0.2% of the global methane source budget or an order of magnitude smaller than many of the previous estimates.

Copper enhances the activity and salt resistance of mixed methane-oxidizing communities.

PubMed

van der Ha, David; Hoefman, Sven; Boeckx, Pascal; Verstraete, Willy; Boon, Nico

2010-08-01

Effluents of anaerobic digesters are an underestimated source of greenhouse gases, as they are often saturated with methane. A post-treatment with methane-oxidizing bacterial consortia could mitigate diffuse emissions at such sites. Semi-continuously fed stirred reactors were used as model systems to characterize the influence of the key parameters on the activity of these mixed methanotrophic communities. The addition of 140 mg L(-1) NH (4) (+) -N had no significant influence on the activity nor did a temperature increase from 28 degrees C to 35 degrees C. On the other hand, addition of 0.64 mg L(-1) of copper(II) increased the methane removal rate by a factor of 1.5 to 1.7 since the activity of particulate methane monooxygenase was enhanced. The influence of different concentrations of NaCl was also tested, as effluents of anaerobic digesters often contain salt levels up to 10 g NaCl L(-1). At a concentration of 11 g NaCl L(-1), almost no methane-oxidizing activity was observed in the reactors without copper addition. Yet, reactors with copper addition exhibited a sustained activity in the presence of NaCl. A colorimetric test based on naphthalene oxidation showed that soluble methane monooxygenase was inhibited by copper, suggesting that the particulate methane monooxygenase was the active enzyme and thus more salt resistant. The results obtained demonstrate that the treatment of methane-saturated effluents, even those with increased ammonium (up to 140 mg L(-1) NH (4) (+) -N) and salt levels, can be mitigated by implementation of methane-oxidizing microbial consortia.

Global health benefits of mitigating ozone pollution with methane emission controls.

PubMed

West, J Jason; Fiore, Arlene M; Horowitz, Larry W; Mauzerall, Denise L

2006-03-14

Methane (CH(4)) contributes to the growing global background concentration of tropospheric ozone (O(3)), an air pollutant associated with premature mortality. Methane and ozone are also important greenhouse gases. Reducing methane emissions therefore decreases surface ozone everywhere while slowing climate warming, but although methane mitigation has been considered to address climate change, it has not for air quality. Here we show that global decreases in surface ozone concentrations, due to methane mitigation, result in substantial and widespread decreases in premature human mortality. Reducing global anthropogenic methane emissions by 20% beginning in 2010 would decrease the average daily maximum 8-h surface ozone by approximately 1 part per billion by volume globally. By using epidemiologic ozone-mortality relationships, this ozone reduction is estimated to prevent approximately 30,000 premature all-cause mortalities globally in 2030, and approximately 370,000 between 2010 and 2030. If only cardiovascular and respiratory mortalities are considered, approximately 17,000 global mortalities can be avoided in 2030. The marginal cost-effectiveness of this 20% methane reduction is estimated to be approximately 420,000 US dollars per avoided mortality. If avoided mortalities are valued at 1 US dollars million each, the benefit is approximately 240 US dollars per tone of CH(4) ( approximately 12 US dollars per tone of CO(2) equivalent), which exceeds the marginal cost of the methane reduction. These estimated air pollution ancillary benefits of climate-motivated methane emission reductions are comparable with those estimated previously for CO(2). Methane mitigation offers a unique opportunity to improve air quality globally and can be a cost-effective component of international ozone management, bringing multiple benefits for air quality, public health, agriculture, climate, and energy.

A new model for including the effect of fly ash on biochemical methane potential.

PubMed

Gertner, Pablo; Huiliñir, César; Pinto-Villegas, Paula; Castillo, Alejandra; Montalvo, Silvio; Guerrero, Lorna

2017-10-01

The modelling of the effect of trace elements on anaerobic digestion, and specifically the effect of fly ash, has been scarcely studied. Thus, the present work was aimed at the development of a new function that allows accumulated methane models to predict the effect of FA on the volume of methane accumulation. For this, purpose five fly ash concentrations (10, 25, 50, 250 and 500mg/L) using raw and pre-treated sewage sludge were used to calibrate the new function, while three fly ash concentrations were used (40, 150 and 350mg/L) for validation. Three models for accumulated methane volume (the modified Gompertz equation, the logistic function, and the transfer function) were evaluated. The results showed that methane production increased in the presence of FA when the sewage sludge was not pre-treated, while with pretreated sludge there is inhibition of methane production at FA concentrations higher than 50mg/L. In the calibration of the proposed function, it fits well with the experimental data under all the conditions, including the inhibition and stimulating zones, with the values of the parameters of the methane production models falling in the range of those reported in the literature. For validation experiments, the model succeeded in representing the behavior of new experiments in both the stimulating and inhibiting zones, with NRMSE and R 2 ranging from 0.3577 to 0.03714 and 0.2209 to 0.9911, respectively. Thus, the proposed model is robust and valid for the studied conditions. Copyright © 2017 Elsevier Ltd. All rights reserved.

Impacts of the large increase in international ship traffic 2000-2007 on tropospheric ozone and methane.

PubMed

Dalsøren, Stig B; Eide, Magnus S; Myhre, Gunnar; Endresen, Oyvind; Isaksen, Ivar S A; Fuglestvedt, Jan S

2010-04-01

The increase in civil world fleet ship emissions during the period 2000-2007 and the effects on key tropospheric oxidants are quantified using a global Chemical Transport Model (CTM). We estimate a substantial increase of 33% in global ship emissions over this period. The impact of ship emissions on tropospheric oxidants is mainly caused by the relatively large fraction of NOx in ship exhaust. Typical increases in yearly average surface ozone concentrations in the most impacted areas are 0.5-2.5 ppbv. The global annual mean radiative forcing due to ozone increases in the troposphere is 10 mWm(-2) over the period 2000-2007. We find global average tropospheric OH increase of 1.03% over the same period. As a result of this the global average tropospheric methane concentration is reduced by approximately 2.2% over a period corresponding to the turnover time. The resulting methane radiative forcing is -14 mWm(-2) with an additional contribution of -6 mWm(-2) from methane induced reduction in ozone. The net forcing of the ozone and methane changes due to ship emissions changes between 2000 and 2007 is -10 mWm(-2). This is significant compared to the net forcing of these components in 2000. Our findings support earlier observational studies indicating that ship traffic may be a major contributor to recent enhancement of background ozone at some coastal stations. Furthermore, by reducing global mean tropospheric methane by 40 ppbv over its turnover time it is likely to contribute to the recent observed leveling off in global mean methane concentration.

Effects of lipid concentration on anaerobic co-digestion of municipal biomass wastes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Yifei, E-mail: sunif@buaa.edu.cn; Wang, Dian; Yan, Jiao

2014-06-01

Highlights: • Lipid in municipal biomass would not inhibited the anaerobic digestion process. • A lipid concentration of 65% of total VS was the inhibition concentration. • The amount of Brevibacterium decreased with the increasing of the lipid contents. • Long chain fatty acids stacked on the methanogenic bacteria and blocked the mass transfer process. - Abstract: The influence of the lipid concentration on the anaerobic co-digestion of municipal biomass waste and waste-activated sludge was assessed by biochemical methane potential (BMP) tests and by bench-scale tests in a mesophilic semi-continuous stirred tank reactor. The effect of increasing the volatile solidmore » (VS) concentration of lipid from 0% to 75% was investigated. BMP tests showed that lipids in municipal biomass waste could enhance the methane production. The results of bench-scale tests showed that a lipids concentration of 65% of total VS was the inhibition concentration. Methane yields increased with increasing lipid concentration when lipid concentrations were below 60%, but when lipid concentration was set as 65% or higher, methane yields decreased sharply. When lipid concentrations were below 60%, the pH values were in the optimum range for the growth of methanogenic bacteria and the ratios of volatile fatty acid (VFA)/alkalinity were in the range of 0.2–0.6. When lipid concentrations exceeded 65%, the pH values were below 5.2, the reactor was acidized and the values of VFA/alkalinity rose to 2.0. The amount of Brevibacterium decreased with increasing lipid content. Long chain fatty acids stacked on the methanogenic bacteria and blocked the mass transfer process, thereby inhibiting anaerobic digestion.« less

Pretreatment of Cottage Cheese to Enhance Biogas Production

PubMed Central

Salgaonkar, Bhakti; Mutnuri, Srikanth

2014-01-01

This study evaluated the possibility of pretreating selected solid fraction of an anaerobic digester treating food waste to lower the hydraulic retention time and increase the methane production. The study investigated the effect of different pretreatments (thermal, chemical, thermochemical and enzymatic) for enhanced methane production from cottage cheese. The most effective pretreatments were thermal and enzymatic. Highest solubilisation of COD was observed in thermal pretreatment, followed by thermochemical. In single enzyme systems, lipase at low concentration gave significantly higher methane yield than for the experiments without enzyme additions. The highest lipase dosages decreased methane yield from cottage cheese. However, in case of protease enzyme an increase in concentration of the enzyme showed higher methane yield. In the case of mixed enzyme systems, pretreatment at 1 : 2 ratio of lipase : protease showed higher methane production in comparison with 1 : 1 and 2 : 1 ratios. Methane production potentials for different pretreatments were as follows: thermal 357 mL/g VS, chemical 293 mL/g VS, and thermochemical 441 mL/g VS. The average methane yield from single enzyme systems was 335 mL/g VS for lipase and 328 mL/g VS for protease. Methane potentials for mixed enzyme ratios were 330, 360, and 339 mL/g VS for 1 : 1, 1 : 2, and 2 : 1 lipase : protease, respectively. PMID:24995288

Seasonal Rates of Methane Oxidation in Anoxic Marine Sediments

PubMed Central

Iversen, Niels; Blackburn, T. Henry

1981-01-01

Methane concentrations and rates of methane oxidation were measured in intact sediment cores from an inshore marine sediment at Jutland, Denmark. The rates of methane oxidation, determined by the appearance of 14CO2 from injected 14CH4, varied with sediment depth and season. Most methane oxidation was anoxic, but oxygen may have contributed to methane oxidation at the sediment surface. Cumulative rates (0- to 12-cm depth) for methane oxidation at Kysing Fjord were 3.34, 3.48, 8.60, and 17.04 μmol m−2 day−1 for April (4°C), May (13°C), July (17°C), and August (21°C), respectively. If all of the methane was oxidized by sulfate, it would account for only 0.01 to 0.06% of the sulfate reduction. The data indicate that methane was produced, in addition to being oxidized, in the 0- to 18-cm sediment stratum. PMID:16345784

CARVE Measurements of Atmospheric Methane Concentrations and Emissions in Arctic and Boreal Alaska

NASA Astrophysics Data System (ADS)

Miller, C. E.; Miller, J. B.; Chang, R. Y.; Sweeney, C.; Karion, A.; Wofsy, S. C.; Henderson, J.; Eluszkiewicz, J.; Mountain, M.; Oechel, W. C.

2013-12-01

The Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE) is a NASA Earth Ventures (EV-1) investigation designed to quantify correlations between atmospheric and surface state variables for the Alaskan terrestrial ecosystems through intensive seasonal aircraft campaigns, ground-based observations, and analysis sustained over a 5-year mission. CARVE bridges critical gaps in our knowledge and understanding of Arctic ecosystems, linkages between the Arctic hydrologic and terrestrial carbon cycles, and the feedbacks from fires and thawing permafrost. We present CARVE airborne measurements of spatial and temporal patterns in atmospheric CH4 concentrations and estimated surface-atmosphere emissions for Arctic and Boreal Alaska. Continuous in situ CH4, CO2 and CO data are supplemented by periodic whole air flask samples from which 13CH4 and non-methane hydrocarbons are used to assess the relative contributions of wetlands, fossil fuel combustion, and oil and gas production to the observed CH4 signals. The CARVE project has also initiated monthly 14CH4 sampling at Barrow, AK (BRW) and the CARVE Tower in Fox, AK (CRV) to evaluate seasonal changes in the fraction of old carbon being mobilized via methanogenesis.

Anaerobic co-digestion of chicken manure and corn stover in batch and continuously stirred tank reactor (CSTR).

PubMed

Li, Yeqing; Zhang, Ruihong; He, Yanfeng; Zhang, Chenyu; Liu, Xiaoying; Chen, Chang; Liu, Guangqing

2014-03-01

Anaerobic co-digestion of chicken manure and corn stover in batch and CSTR were investigated. The batch co-digestion tests were performed at an initial volatile solid (VS) concentration of 3gVS/L, carbon-to-nitrogen (C/N) ratio of 20, and retention time of 30d. The methane yield was determined to be 281±12mL/gVSadded. Continuous reactor was carried out with feeding concentration of 12% total solids and C/N ratio of 20 at organic loading rates (OLRs) of 1-4gVS/L/d. Results showed that at OLR of 4gVS/L/d, stable and preferable methane yield of 223±7mL/gVSadded was found, which was equal to energy yield (EY) of 8.0±0.3MJ/kgVSadded. Post-digestion of digestate gave extra EY of 1.5-2.6MJ/kgVSadded. Pyrolysis of digestate provided additional EY of 6.1MJ/kgVSadded. Pyrolysis can be a promising technique to reduce biogas residues and to produce valuable gas products simultaneously. Copyright © 2014 Elsevier Ltd. All rights reserved.

Method for the photocatalytic conversion of gas hydrates

DOEpatents

Taylor, Charles E.; Noceti, Richard P.; Bockrath, Bradley C.

2001-01-01

A method for converting methane hydrates to methanol, as well as hydrogen, through exposure to light. The process includes conversion of methane hydrates by light where a radical initiator has been added, and may be modified to include the conversion of methane hydrates with light where a photocatalyst doped by a suitable metal and an electron transfer agent to produce methanol and hydrogen. The present invention operates at temperatures below 0.degree. C., and allows for the direct conversion of methane contained within the hydrate in situ.

Biogeochemical and microbiological characteristic of the pockmark sediments, the Gdansk Deep, The Baltic Sea

NASA Astrophysics Data System (ADS)

Pimenov, Nikolay; Kanapatskiy, Timur; Sivkov, Vadim; Toshchakov, Stepan; Korzhenkov, Aleksei; Ulyanova, Marina

2016-04-01

Comparison of the biogeochemical and microbial features was done for the gas-bearing and background sediments as well as near-bottom water of the Gdansk Deep, The Baltic Sea. Data were received in October, 2015 during 64th cruise of the R/V Akademik Mstislav Keldysh. Gas-bearing sediments were sampled within the known pockmark (Gas-Point, depth 94 m). Background sediments area (BG-Point, depth 86 m) was located several km off the pockmark area. The sulphate concentration in the pore water of the surface sediment layer (0-5 cm) of Gas-Point was 9,7 mmol/l, and sharply decreased with depth (did not exceed 1 mmol/l deeper than 50 cm). The sulphate concentration decrease at BG-Point also took place but was not so considerable. Sulphate concentration decrease is typical for the organic rich sediments of the high productive areas, both as for the methane seep areas. Fast sulphate depletion occurs due to active processes of its microbial reduction by consortium of the sulphate-reduction bacteria, which may use low-molecular organic compounds or hydrogen, formed at the different stages of the organic matter destruction; as well as within the process of the anaerobic methane oxidation by consortium of the methane-trophic archaea and sulphate-reduction bacteria. Together with sulphate concentration decrease the methane content increase, typical for the marine sediments, occurred. At the Gas-Point the methane concentration varied within 10 μmol/dm3 in the surface layer till its maximum at sediment horizon of 65 cm (5 mmol/dm3), and decreased to 1.5 mmol/dm3 at depth of 300 cm. The BG-Point maximum values were defined at sediment horizon 6 cm (2,6 μmol/dm3). Methane sulfate transition zone at the Gas-Point sediments was at 25-35 cm depth; whereas it was not defined at the BG-Point mud. High methane concentration in the gas-bearing sediments results in the formation of the methane seep from the sediments to the near-bottom water. So the Gas-Point near-bottom waters were characterized by high methane concentration (0.36-0.50 μmol/l) even in the water 2-5 m above the bottom (0.08-0.28 μmol/l), whereas at the BG-Point sediments methane concentration in the near-bottom water was 0.06-0.08 μmol/l. In order to get insights into the structure of microbial community responsible for realization of these redox processes we performed microbial community profiling using high-throughput 16S amplicon sequencing. DNA was extracted from sediments and water column in pockmark and background zones. NGS libraries were prepared with fusion primers for V4 variable region (Caporaso et al., 2012) and sequenced on the MiSeq system. Results well correlated with new data obtained from the analysis of the intensity of microbial processes. The study was financed by the Russian Scientific Fund (grant 14-37-00047). Caporaso JG, Lauber CL, Walters WA, Berg-Lyons D, Huntley J, Fierer N, Owens SM, Betley J, Fraser L, Bauer M, Gormley N, Gilbert JA, Smith G, Knight R. Ultra-high-throughput microbial community analysis on the Illumina HiSeq and MiSeq platforms. ISME J. 2012 Aug;6(8):1621-4

Thermophilic methane production from cattle waste.

PubMed Central

Varel, V H; Isaacson, H R; Bryant, M P

1977-01-01

Methane production from waste of cattle fed a finishing diet was investigated, using four 3-liter-working volume anaerobic digestors at 60 degrees C. At 55 degrees C a start-up culture, in which waste was the only source of bacteria, was generated within 8 days and readily adapted to 60 degrees C, where efficiency of methanogenesis was greater. Increasing the temperature from 60 to 65 degrees C tended to drastically lower efficiency. When feed concentrations of volatile solids (VS, organic matter) were increased in steps of 2% after holding for 1 months at a given concentration, the maximum concentrations for efficient fermentation were 8.2, 10.0, 11.6, and 11.6% for the retention times (RT) of 3, 6, 9, and 12 days, respectively. The VS destructions for these and lower feed concentrations were 31 to 37, 36 to 40, 47 to 49 and 51 to 53% for the 3-, 6-, 9-, and 12-day RT digestors, respectively, and the corresponding methane production rates were about 0.16, 0.18, 0.20, and 0.22 liters/day per g of VS in the feed. Gas contained 52 to 57% methane. At the above RT and feed concentrations, alkalinity rose to 5,000 to 7,700 mg of CaCo3 per liter (pH to 7.5 to 7.8), NH3 plus NH4+ to 64 to 90 mM, and total volatile acids to 850 to 2,050 mg/liter as acetate. The 3-day RT digestor was quite stable up to 8.2% feed VS and at this feed concentration produced methane at the very high rate of 4.5 liters/day per liter of digestor. Increasing the percentage of feed VS beyond those values indicated above resulted in greatly decreased organic matter destruction and methane production, variable decrease in pH, and increased alkalinity, ammonia, and total volatile acid concentrations, with propionate being the first to accumulate in large amounts. In a second experiment with another lot of waste, the results were similar. These studies indicate that loading rates can be much higher than those previously thought useful for maximizing methanogenesis from cattle waste. PMID:557954

Methane turnover and methanotrophic communities in arctic aquatic ecosystems of the Lena Delta, Northeast Siberia.

PubMed

Osudar, Roman; Liebner, Susanne; Alawi, Mashal; Yang, Sizhong; Bussmann, Ingeborg; Wagner, Dirk

2016-08-01

Large amounts of organic carbon are stored in Arctic permafrost environments, and microbial activity can potentially mineralize this carbon into methane, a potent greenhouse gas. In this study, we assessed the methane budget, the bacterial methane oxidation (MOX) and the underlying environmental controls of arctic lake systems, which represent substantial sources of methane. Five lake systems located on Samoylov Island (Lena Delta, Siberia) and the connected river sites were analyzed using radiotracers to estimate the MOX rates, and molecular biology methods to characterize the abundance and the community composition of methane-oxidizing bacteria (MOB). In contrast to the river, the lake systems had high variation in the methane concentrations, the abundance and composition of the MOB communities, and consequently, the MOX rates. The highest methane concentrations and the highest MOX rates were detected in the lake outlets and in a lake complex in a flood plain area. Though, in all aquatic systems, we detected both, Type I and II MOB, in lake systems, we observed a higher diversity including MOB, typical of the soil environments. The inoculation of soil MOB into the aquatic systems, resulting from permafrost thawing, might be an additional factor controlling the MOB community composition and potentially methanotrophic capacity. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

Methane asphyxia. Coal mine accident investigation of distribution of gas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Terazawa, K.; Takatori, T.; Tomii, S.

1985-09-01

Death from asphyxia due to substitution of air by methane gas may occur in coal mine by gas outburst. In such a case, it is required to determine methane gas contents from cadaveric blood and tissues for diagnosing cause of death and estimating conditions of the accident. The methane concentration in blood and tissue samples of 22 male victims by a gas outburst accident was measured by gas chromatography. The level of methane in the cardiac blood was in the range of 6.8-26.8 microliters/g. As a model of gas outburst in coal mine, rats were exposed experimentally to various concentrationsmore » of methane. Their course of death and methane distribution in the bodies were observed. From these findings, diagnostic criteria for asphyxia from substitution of air by methane are also discussed.« less

Differentiation of pre-existing trapped methane from thermogenic methane in an igneous-intruded coal by hydrous pyrolysis

USGS Publications Warehouse

Dias, Robert F.; Lewan, Michael D.; Birdwell, Justin E.; Kotarba, Maciej J.

2014-01-01

So as to better understand how the gas generation potential of coal changes with increasing rank, same-seam samples of bituminous coal from the Illinois Basin that were naturally matured to varying degrees by the intrusion of an igneous dike were subjected to hydrous pyrolysis (HP) conditions of 360 °C for 72 h. The accumulated methane in the reactor headspace was analyzed for δ13C and δ2H, and mol percent composition. Maximum methane production (9.7 mg/g TOC) occurred in the most immature samples (0.5 %Ro), waning to minimal methane values at 2.44 %Ro (0.67 mg/g TOC), and rebounding to 3.6 mg/g TOC methane in the most mature sample (6.76 %Ro). Methane from coal with the highest initial thermal maturity (6.76 %Ro) shows no isotopic dependence on the reactor water and has a microbial δ13C value of −61‰. However, methane from coal of minimal initial thermal maturity (0.5 %Ro) shows hydrogen isotopic dependence on the reaction water and has a δ13C value of −37‰. The gas released from coals under hydrous pyrolysis conditions represents a quantifiable mixture of ancient (270 Ma) methane (likely microbial) that was generated in situ and trapped within the rock during the rapid heating by the dike, and modern (laboratory) thermogenic methane that was generated from the indigenous organic matter due to thermal maturation induced by hydrous pyrolysis conditions. These findings provide an analytical framework for better assessment of natural gas sources and for differentiating generated gas from pre-existing trapped gas in coals of various ranks.

77 FR 77113 - Petitions for Modification of Application of Existing Mandatory Safety Standards

Federal Register 2010, 2011, 2012, 2013, 2014

2012-12-31

... for methane immediately before and during the use of nonpermissible surveying equipment in or inby the last open crosscut. (e) Nonpermissible surveying equipment will not be used if methane is detected in concentrations at or above one percent for the area being surveyed. When methane is detected at such levels while...

77 FR 57157 - Petitions for Modification of Application of Existing Mandatory Safety Standards

Federal Register 2010, 2011, 2012, 2013, 2014

2012-09-17

... for methane immediately before and during the use of nonpermissible surveying equipment in or inby the last open crosscut. (e) Nonpermissible surveying equipment will not be used if methane is detected in concentrations at or above one percent for the area being surveyed. When methane is detected at such levels while...

78 FR 59723 - Petitions for Modification of Application of Existing Mandatory Safety Standards

Federal Register 2010, 2011, 2012, 2013, 2014

2013-09-27

... person as defined in 30 CFR 75.151 will continuously monitor for methane immediately before and during... equipment will not be used if methane is detected in concentrations at or above one percent for the area being surveyed. When methane is detected at such levels while the nonpermissible surveying equipment is...

A 3D Microphysical Model of Titan's Methane Cloud

NASA Astrophysics Data System (ADS)

Xiao, J.; Newman, C.; Inada, A.; Richardson, M.

2006-12-01

A time-dependent idealized 3D microphysical model for Titan's methane cloud is described. This new high resolution microphysical model nests in a Titan WRF GCM model. It assumes the vapor-liquid equilibria of methane-nitrogen mixtures which are based on the recent chemical experiments and thermodynamics models. In particular, the methane is condensed at a given temperature and pressure. Meanwhile nitrogen is dissolved in the methane liquid. The new model first uses the data from the thermodynamic model (Kouvaris et al. 1991), which involves saturation criteria, composition of condensate, and latent heat for a given pressure-temperature profile. For altitudes lower than 14 km, methane is saturated and condensed into liquid phase. However for altitudes from 14 km above to tropopause, methane is changed into supercooled liquid state. Then, we do some testing experiments with 1D model by varying the initial methane vapor mass mixing ratio profile and the initial mole fraction of methane in liquid phase. Based on the steady state results from 1D model, an idealized 3D microphysics model is developed to investigate the convection cloud in Titan's troposphere. Due to lower relative humidity at titan's surface (Samuelson et al. 1997) and the current estimated moist adiabatic lapse rate, convection is hardly to happen without lifting. For this reason, we apply a symmetry cosine ridge in a 100*100 grids box to force the air flow lifted at certain levels, which in turn drives the condensation of methane vapor. In addition to the abundance of methane clouds and its duration provided by the 3D model, our study demonstrates that vertical motion might be likely the major cause of convection clouds in Titan's troposphere. As the future work, we will further investigate size-resolved microphysical scheme to insight into the nature of methane cycle in Titan's atmosphere.

Determining the flux of methane into Hudson Canyon at the edge of methane clathrate hydrate stability

USGS Publications Warehouse

Weinsten, A.; Navarrete, L; Ruppel, Carolyn D.; Weber, T.C.; Leonte, M.; Kellermann, M.; Arrington, E.; Valentine, D.L.; Scranton, M.L; Kessler, John D.

2016-01-01

Methane seeps were investigated in Hudson Canyon, the largest shelf-break canyon on the northern US Atlantic Margin. The seeps investigated are located at or updip of the nominal limit of methane clathrate hydrate stability. The acoustic identification of bubble streams was used to guide water column sampling in a 32 km2 region within the canyon's thalweg. By incorporating measurements of dissolved methane concentration with methane oxidation rates and current velocity into a steady-state box model, the total emission of methane to the water column in this region was estimated to be 12 kmol methane per day (range: 6 – 24 kmol methane per day). These analyses suggest this methane is largely retained inside the canyon walls below 300 m water depth, and that it is aerobically oxidized to near completion within the larger extent of Hudson Canyon. Based on estimated methane emissions and measured oxidation rates, the oxidation of this methane to dissolved CO2 is expected to have minimal influences on seawater pH. This article is protected by copyright. All rights reserved.

Determining the flux of methane into Hudson Canyon at the edge of methane clathrate hydrate stability

NASA Astrophysics Data System (ADS)

Weinstein, Alexander; Navarrete, Luis; Ruppel, Carolyn; Weber, Thomas C.; Leonte, Mihai; Kellermann, Matthias Y.; Arrington, Eleanor C.; Valentine, David L.; Scranton, Mary I.; Kessler, John D.

2016-10-01

Methane seeps were investigated in Hudson Canyon, the largest shelf-break canyon on the northern U.S. Atlantic Margin. The seeps investigated are located at or updip of the nominal limit of methane clathrate hydrate stability. The acoustic identification of bubble streams was used to guide water column sampling in a 32 km2 region within the canyon's thalweg. By incorporating measurements of dissolved methane concentration with methane oxidation rates and current velocity into a steady state box model, the total emission of methane to the water column in this region was estimated to be 12 kmol methane per day (range: 6-24 kmol methane per day). These analyses suggest that the emitted methane is largely retained inside the canyon walls below 300 m water depth, and that it is aerobically oxidized to near completion within the larger extent of Hudson Canyon. Based on estimated methane emissions and measured oxidation rates, the oxidation of this methane to dissolved CO2 is expected to have minimal influences on seawater pH.

The regulation of methane oxidation in soil

NASA Technical Reports Server (NTRS)

Mancinelli, R. L.

1995-01-01

The atmospheric concentration of methane, a greenhouse gas, has more than doubled during the past 200 years. Consequently, identifying the factors influencing the flux of methane into the atmosphere is becoming increasingly important. Methanotrophs, microaerophilic organisms widespread in aerobic soils and sediments, oxidize methane to derive energy and carbon for biomass. In so doing, they play an important role in mitigating the flux of methane into the atmosphere. Several physico-chemical factors influence rates of methane oxidation in soil, including soil diffusivity; water potential; and levels of oxygen, methane, ammonium, nitrate, nitrite, and copper. Most of these factors exert their influence through interactions with methane monooxygenase (MMO), the enzyme that catalyzes the reaction converting methane to methanol, the first step in methane oxidation. Although biological factors such as competition and predation undoubtedly play a role in regulating the methanotroph population in soils, and thereby limit the amount of methane consumed by methanotrophs, the significance of these factors is unknown. Obtaining a better understanding of the ecology of methanotrophs will help elucidate the mechanisms that regulate soil methane oxidation.

Environmental impacts on the diversity of methane-cycling microbes and their resultant function

PubMed Central

Aronson, Emma L.; Allison, Steven D.; Helliker, Brent R.

2013-01-01

Methane is an important anthropogenic greenhouse gas that is produced and consumed in soils by microorganisms responding to micro-environmental conditions. Current estimates show that soil consumption accounts for 5–15% of methane removed from the atmosphere on an annual basis. Recent variability in atmospheric methane concentrations has called into question the reliability of estimates of methane consumption and calls for novel approaches in order to predict future atmospheric methane trends. This review synthesizes the environmental and climatic factors influencing the consumption of methane from the atmosphere by non-wetland, terrestrial soil microorganisms. In particular, we focus on published efforts to connect community composition and diversity of methane-cycling microbial communities to observed rates of methane flux. We find abundant evidence for direct connections between shifts in the methane-cycling microbial community, due to climate and environmental changes, and observed methane flux levels. These responses vary by ecosystem and associated vegetation type. This information will be useful in process-based models of ecosystem methane flux responses to shifts in environmental and climatic parameters. PMID:23966984

Microbial oxidation as a methane sink beneath the West Antarctic Ice Sheet

NASA Astrophysics Data System (ADS)

Michaud, Alexander B.; Dore, John E.; Achberger, Amanda M.; Christner, Brent C.; Mitchell, Andrew C.; Skidmore, Mark L.; Vick-Majors, Trista J.; Priscu, John C.

2017-08-01

Aquatic habitats beneath ice masses contain active microbial ecosystems capable of cycling important greenhouse gases, such as methane (CH4). A large methane reservoir is thought to exist beneath the West Antarctic Ice Sheet, but its quantity, source and ultimate fate are poorly understood. For instance, O2 supplied by basal melting should result in conditions favourable for aerobic methane oxidation. Here we use measurements of methane concentrations and stable isotope compositions along with genomic analyses to assess the sources and cycling of methane in Subglacial Lake Whillans (SLW) in West Antarctica. We show that sub-ice-sheet methane is produced through the biological reduction of CO2 using H2. This methane pool is subsequently consumed by aerobic, bacterial methane oxidation at the SLW sediment-water interface. Bacterial oxidation consumes >99% of the methane and represents a significant methane sink, and source of biomass carbon and metabolic energy to the surficial SLW sediments. We conclude that aerobic methanotrophy may mitigate the release of methane to the atmosphere upon subglacial water drainage to ice sheet margins and during periods of deglaciation.

Real-time surrogate analysis for potential oil and gas contamination of drinking water resources

NASA Astrophysics Data System (ADS)

Son, Ji-Hee; Carlson, Kenneth H.

2015-09-01

Public concerns related to the fast-growing shale oil and gas industry have increased during recent years. The major concern regarding shale gas production is the potential of fracturing fluids being injected into the well or produced fluids flowing out of the well to contaminate drinking water resources such as surface water and groundwater. Fracturing fluids contain high total dissolved solids (TDS); thus, changes in TDS concentrations in groundwater might indicate influences of fracturing fluids. An increase of methane concentrations in groundwater could also potentially be due to hydraulic fracturing activities. To understand the possible contamination of groundwater by fracturing activities, real-time groundwater monitoring is being implemented in the Denver-Julesburg basin of northeast Colorado. A strategy of monitoring of surrogate parameters was chosen instead of measuring potential contaminants directly, an approach that is not cost effective or operationally practical. Contaminant surrogates of TDS and dissolved methane were proposed in this study, and were tested for correlation and data distribution with laboratory experiments. Correlations between TDS and electrical conductivity (EC), and between methane contamination and oxidation-reduction potential (ORP) were strong at low concentrations of contaminants (1 mg/L TDS and 0.3 mg/L CH4). Dissolved oxygen (DO) was only an effective surrogate at higher methane concentrations (≥2.5 mg/L). The results indicated that EC and ORP are effective surrogates for detecting concentration changes of TDS and methane, respectively, and that a strategy of monitoring for easy to measure parameters can be effective detecting real-time, anomalous behavior relative to a predetermined baseline.

Model development and evaluation of methane potential from anaerobic co-digestion of municipal wastewater sludge and un-dewatered grease trap waste.

PubMed

Yalcinkaya, Sedat; Malina, Joseph F

2015-06-01

The performance of anaerobic co-digestion of municipal wastewater sludge with un-dewatered grease trap waste was assessed using modified biochemical methane potential tests under mesophilic conditions (35°C). Methane potentials, process inhibition and chemical behavior of the process were analyzed at different grease trap waste feed ratios on volatile solids basis. Nonlinear regression analyses of first order reaction and modified Gompertz equations were performed to assist in interpretation of the experimental results. Methane potential of un-dewatered grease trap waste was measured as 606 mL CH4/g VS(added), while methane potential of municipal wastewater sludge was only 223 mL CH4/g VS(added). The results indicated that anaerobic digestion of grease trap waste without dewatering yields less methane potential than concentrated/dewatered grease trap waste because of high wastewater content of un-dewatered grease trap waste. However, anaerobic co-digestion of municipal wastewater sludge and grease trap waste still yields over two times more methane potential and approximately 10% more volatile solids reduction than digestion of municipal wastewater sludge alone. The anaerobic co-digestion process inhibitions were reported at 70% and greater concentrated/dewatered grease trap waste additions on volatile solids basis in previous studies; however, no inhibition was observed at 100% un-dewatered grease trap waste digestion in the present study. These results indicate that anaerobic co-digestion of un-dewatered grease trap waste may reduce the inhibition risk compared to anaerobic co-digestion of concentrated/dewatered grease trap waste. In addition, a mathematical model was developed in this study for the first time to describe the relationship between grease trap waste feed ratio on volatile solids basis and resulting methane potential. Experimental data from the current study as well as previous biochemical methane potential studies were successfully fit to this relationship and allowed estimation of key performance parameters that provide additional insight into the factors affecting biochemical methane potential. Copyright © 2015 Elsevier Ltd. All rights reserved.

Effect of 3-nitrooxypropanol on methane and hydrogen emissions, methane isotopic signature, and ruminal fermentation in dairy cows.

PubMed

Lopes, J C; de Matos, L F; Harper, M T; Giallongo, F; Oh, J; Gruen, D; Ono, S; Kindermann, M; Duval, S; Hristov, A N

2016-07-01

The objective of this crossover experiment was to investigate the effect of a methane inhibitor, 3-nitrooxypropanol (3NOP), on enteric methane emission, methane isotopic composition, and rumen fermentation and microbial profile in lactating dairy cows. The experiment involved 6 ruminally cannulated late-lactation Holstein cows assigned to 2 treatments: control and 3NOP (60 mg/kg of feed dry matter). Compared with the control, 3NOP decreased methane emission by 31% and increased hydrogen emission from undetectable to 1.33 g/d. Methane emissions per kilogram of dry matter intake and milk yield were also decreased 34% by 3NOP. Milk production and composition were not affected by 3NOP, except milk fat concentration was increased compared with the control. Concentrations of total VFA and propionate in ruminal fluid were not affected by treatment, but acetate concentration tended to be lower and acetate-to-propionate ratio was lower for 3NOP compared with the control. The 3NOP decreased the molar proportion of acetate and increase those of propionate, butyrate, valerate, and isovalerate. Deuterium-to-hydrogen ratios of methane and the abundance of (13)CH3D were similar between treatments. Compared with the control, minor (4‰) depletion in the (13)C/(12)C ratio was observed for 3NOP. Genus composition of methanogenic archaea (Methanobrevibacter, Methanosphaera, and Methanomicrobium) was not affected by 3NOP, but the proportion of methanogens in the total cell counts tended to be decreased by 3NOP. Prevotella spp., the predominant bacterial genus in ruminal contents in this experiment, was also not affected by 3NOP. Compared with the control, Ruminococcus and Clostridium spp. were decreased and Butyrivibrio spp. was increased by 3NOP. This experiment demonstrated that a substantial inhibition of enteric methane emission by 3NOP in dairy cows was accompanied with increased hydrogen emission and decreased acetate-to-propionate ratio; however, neither an effect on rumen archaeal community composition nor a significant change in the isotope composition of methane was observed. Copyright © 2016 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Biohydrogen and methane production via a two-step process using an acid pretreated native microalgae consortium.

PubMed

Carrillo-Reyes, Julian; Buitrón, Germán

2016-12-01

A native microalgae consortium treated under thermal-acidic hydrolysis was used to produce hydrogen and methane in a two-step sequential process. Different acid concentrations were tested, generating hydrogen and methane yields of up to 45mLH 2 gVS -1 and 432mLCH 4 gVS -1 , respectively. The hydrogen production step solubilized the particulate COD (chemical oxygen demand) up to 30%, creating considerable amounts of volatile fatty acids (up to 10gCODL -1 ). It was observed that lower acid concentration presented higher hydrogen and methane production potential. The results revealed that thermal acid hydrolysis of a native microalgae consortium is a simple but effective strategy for producing hydrogen and methane in the sequential process. In addition to COD removal (50-70%), this method resulted in an energy recovery of up to 15.9kJ per g of volatile solids of microalgae biomass, one of the highest reported. Copyright © 2016 Elsevier Ltd. All rights reserved.

Unmanned aerial system laser based measurements of ammonia and methane emissions from animal feeding operations

NASA Astrophysics Data System (ADS)

Shadman, S.; McHale, L.; Miller, T.; Yalin, A.

2017-12-01

In the US, 40 Tg of ammonia is emitted every year into the atmosphere via agricultural activities. Ammonia is the third most abundant nitrogen containing species in the atmosphere and it has important impacts on atmospheric chemistry, health, and the environment. Since the atmospheric lifetime of ammonia is a few days, it typically deposits to the ground close to its source. In this study we are developing two laser-based sensors to measure ammonia and methane emissions from concentrated animal feeding operations (CAFOs) with the specific goal of quantifying the dry deposition of ammonia in the first few kilometers downwind of the CAFOs. Since methane is nonreactive and does not undergo dry deposition, its change in concentration with downwind distance is due to dispersion alone. We therefore plan to use methane as a conservative tracer, and will infer the ammonia deposition from the changing (deceasing) ratio of ammonia to methane as a function of downwind position. The laser sensors (ammonia and methane) developed in this study are relatively lightweight (<3.5 kg), low power (<40 W) and achieve part-per-billion level concentration sensitivity via sensitive open-path absorption spectroscopy methods. The sensors are designed for simultaneous airborne measurements of both species on a 12 foot Telemaster unmanned aerial system (UAS). The methane sensor employs cavity ring-down spectroscopy (CRDS) at 1.65 um with a distributed feedback laser and has effective cavity length of 20 km. The ammonia sensor employs wavelength modulation spectroscopy (WMS) with a quantum cascade laser at 10.33 um with a Herriot multipass cell (19 m effective length). In order to minimize the thermal expansion effects, most mounts and physical structures are made from carbon-fiber. For each sensor, a custom electronics module has been designed to control and power the electro-optic components, as well as to acquire, analyze, and save data (including concentration, temperature, pressure, and GPS time and position). The sensors have been characterized in the lab (Allan variance) and show sensitivities of 1.5 ppb (at 1 Hz) and 20 ppb (at 1 Hz), for ammonia and methane respectively.

A cryptic sulfur cycle driven by iron in the methane zone of marine sediment (Aarhus Bay, Denmark)

NASA Astrophysics Data System (ADS)

Holmkvist, Lars; Ferdelman, Timothy G.; Jørgensen, Bo Barker

2011-06-01

Sulfate reduction and sulfur-iron geochemistry were studied in 5-6 m deep gravity cores of Holocene mud from Aarhus Bay (Denmark). A goal was to understand whether sulfate is generated by re-oxidation of sulfide throughout the sulfate and methane zones, which might explain the abundance of active sulfate reducers deep below the main sulfate zone. Sulfate penetrated down to 130 cm where methane started to build up and where the concentration of free sulfide peaked at 5.5 mM. Below this sulfate-methane transition, sulfide diffused downwards to a sulfidization front at 520 cm depth, below which dissolved iron, Fe 2+, accumulated in the pore water. Sulfate reduction rates measured by 35S-tracer incubations in the sulfate zone were high due to high concentrations of reactive organic matter. Within the sulfate-methane transition, sulfate reduction was distinctly stimulated by the anaerobic oxidation of methane. In the methane zone below, sulfate remained at positive "background" concentrations of <0.5 mM down to the sulfidization front. Sulfate reduction decreased steeply to rates which at 300-500 cm depth were 0.2-1 pmol SO 42- cm -3 d -1, i.e., 4-5 orders of magnitude lower than rates measured near the sediment surface. The turn-over time of sulfate increased from 3 years at 12 cm depth to 100-1000 years down in the methane zone. Sulfate reduction in the methane zone accounted for only 0.1% of sulfate reduction in the entire sediment column and was apparently limited by the low pore water concentration of sulfate and the low availability of organic substrates. Amendment of the sediment with both sulfate and organic substrates immediately caused a 10- to 40-fold higher, "potential sulfate reduction" which showed that a physiologically intact community of sulfate reducing bacteria was present. The "background" sulfate concentration appears to be generated from the reaction of downwards diffusing sulfide with deeply buried Fe(III) species, such as poorly-reactive iron oxides or iron bound in reactive silicates. The oxidation of sulfide to sulfate in the sulfidic sediment may involve the formation of elemental sulfur and thiosulfate and their further disproportionation to sulfide and sulfate. The net reaction of sulfide and Fe(III) to form pyrite requires an additional oxidant, irrespective of the formation of sulfate. This could be CO 2 which is reduced with H 2 to methane. The methane subsequently diffuses upwards to become re-oxidized at the sulfate-methane transition and thereby removes excess reducing power and enables the formation of excess sulfate. We show here how the combination of these well-established sulfur-iron-carbon reactions may lead to the deep formation of sulfate and drive a cryptic sulfur cycle. The iron-rich post-glacial sediments underlying Holocene marine mud stimulate the strong sub-surface sulfide reoxidation observed in Aarhus Bay and are a result of the glacial to interglacial history of the Baltic Sea area. Yet, processes similar to the ones described here probably occur widespread in marine sediments, in particular along the ocean margins.

Formation of methane nano-bubbles during hydrate decomposition and their effect on hydrate growth.

PubMed

Bagherzadeh, S Alireza; Alavi, Saman; Ripmeester, John; Englezos, Peter

2015-06-07

Molecular dynamic simulations are performed to study the conditions for methane nano-bubble formation during methane hydrate dissociation in the presence of water and a methane gas reservoir. Hydrate dissociation leads to the quick release of methane into the liquid phase which can cause methane supersaturation. If the diffusion of methane molecules out of the liquid phase is not fast enough, the methane molecules agglomerate and form bubbles. Under the conditions of our simulations, the methane-rich quasi-spherical bubbles grow to become cylindrical with a radius of ∼11 Å. The nano-bubbles remain stable for about 35 ns until they are gradually and homogeneously dispersed in the liquid phase and finally enter the gas phase reservoirs initially set up in the simulation box. We determined that the minimum mole fraction for the dissolved methane in water to form nano-bubbles is 0.044, corresponding to about 30% of hydrate phase composition (0.148). The importance of nano-bubble formation to the mechanism of methane hydrate formation, growth, and dissociation is discussed.

Effect of Dietary Forage to Concentrate Ratio on Lactation Performance and Methane Emission from Dairy Cows

USDA-ARS?s Scientific Manuscript database

Our objective was to determine the effect of feeding diets with different forage to concentrate ratios (F:C) on performance and methane (CH4) emission from lactating dairy cows. Eight multiparous Holstein cows (means ± standard deviation: 620 ± 38 kg of body weight (BW); 41 ± 34 days in milk (DIM)) ...

40 CFR 63.1426 - Process vent requirements for determining organic HAP concentration, control efficiency, and...

Code of Federal Regulations, 2010 CFR

2010-07-01

... percent reduction may be measured as total epoxide, total organic HAP, or as TOC minus methane and ethane... TOC (minus methane and ethane) concentrations in all process vent streams and primary and secondary... million by volume total epoxide or TOC limit in § 63.1425(b)(1)(ii) or (b)(2)(iii), the sampling site...

Dissolved methane concentration and flux in the coastal zone of the Southern California Bight-Mexican sector: Possible influence of wastewater

EPA Science Inventory

We measured dissolved methane concentrations ([CH4]) in the coastal zone of the Southern California Bight-Mexican sector (SCBMex) during two cruises: S1 in the USA–Mexico Border Area (BA) during a short rainstorm and S2 in the entire SCBMex during a drier period a few days later....

Solubility of aqueous methane under metastable conditions: implications for gas hydrate nucleation.

PubMed

Guo, Guang-Jun; Rodger, P Mark

2013-05-30

To understand the prenucleation stage of methane hydrate formation, we measured methane solubility under metastable conditions using molecular dynamics simulations. Three factors that influence solubility are considered: temperature, pressure, and the strength of the modeled van der Waals attraction between methane and water. Moreover, the naturally formed water cages and methane clusters in the methane solutions are analyzed. We find that both lowering the temperature and increasing the pressure increase methane solubility, but lowering the temperature is more effective than increasing the pressure in promoting hydrate nucleation because the former induces more water cages to form while the latter makes them less prevalent. With an increase in methane solubility, the chance of forming large methane clusters increases, with the distribution of cluster sizes being exponential. The critical solubility, beyond which the metastable solutions spontaneously form hydrate, is estimated to be ~0.05 mole fraction in this work, corresponding to the concentration of 1.7 methane molecules/nm(3). This value agrees well with the cage adsorption hypothesis of hydrate nucleation.

The lipid response of aerobic marine methanotroph communities under changing environmental conditions.

NASA Astrophysics Data System (ADS)

Rush, D.; Villanueva, L.; van der Meer, M.; S Sinninghe Damsté, J.

2017-12-01

Methane (CH4) originating from marine environments accounts for a significant amount of atmospheric greenhouse gas. Aerobic methanotrophs, which convert CH4 to CO­2, are responsible for quenching a part of this methane before its release. Modern-day climate projections show a rapid shift towards a warmer, more acidic ocean. How do these important methanotrophic communities respond to such changes to their environment? Here, we present the results of microcosm experiments from three marine regions influenced by CH4. Particulate organic matter and sediment were collected from the Black Sea, the Baltic Sea, and the North Sea, at depths ideal for aerobic methanotroph communities at the time of sampling (e.g. oxic, in area of active CH4 release). These were incubated under different temperatures, pHs, and labelled 13CH4 concentrations. We monitored methane concentration in these microcosms as an indication of 13CH4 consumption by methanotrophs. Once the methane concentration was <0.1%, incubations were terminated. We will trace isotopically heavy 13C in the DNA and lipids of the organisms oxidising methane in order to elucidate which organisms are performing methane oxidation and whether they synthesize specific biomarker lipids. Particular attention will be paid to the abundances and diversity of bacteriohopanepolyol lipids, known methanotroph biomarkers. The ultimate goal of our investigation is to determine the effect changes in these environmental parameters have on aerobic methanotroph community structures and their lipid fingerprints. By establishing reliable biomarker lipids for aerobic methanotrophy at certain conditions, we will then be able to investigate the contribution of aerobic methanotrophy throughout Earth's history, especially at times when CH4 concentrations were higher than they are at present.

Biofiltration of air polluted with methane at concentration levels similar to swine slurry emissions: influence of ammonium concentration.

PubMed

Veillette, Marc; Avalos Ramirez, Antonio; Heitz, Michèle

2012-01-01

An evaluation of the effect of ammonium on the performance of two up-flow inorganic packed bed biofilters treating methane was conducted. The air flow rate was set to 3.0 L min(-1) for an empty bed residence time of 6.0 min. The biofilter was fed with a methane concentration of 0.30% (v/v). The ammonium concentration in the nutrient solution was increased by small increments (from 0.01 to 0.025 gN-NH(4) (+) L(-1)) for one biofilter and by large increments of 0.05 gN-NH(4) (+) L(-1) in the other biofilter. The total concentration of nitrogen was kept constant at 0.5 gN-NH(4) (+) L(-1) throughout the experiment by balancing ammonium with nitrate. For both biofilters, the methane elimination capacity, carbon dioxide production, nitrogen bed retention and biomass content decreased with the ammonium concentration in the nutrient solution. The biofilter with smaller ammonium increments featured a higher elimination capacity and carbon dioxide production rate, which varied from 4.9 to 14.3 g m(-3) h(-1) and from 11.5 to 30 g m(-3) h(-1), respectively. Denitrification was observed as some values of the nitrate production rate were negative for ammonium concentrations below 0.2 gN-NH(4) (+) L(-1). A Michalelis-Menten-type model fitted the ammonium elimination rate and the nitrate production rate.

Effect of sediment composition on methane concentration and production in the transition zone of a mangrove (Sepetiba Bay, Rio de Janeiro, Brazil).

PubMed

Marinho, C C; Campos, E A; Guimarães, J R D; Esteves, F A

2012-08-01

The aim of this research was to evaluate the effect of sediment composition on methane (CH4) dynamics in sediments of different areas in the transition zone between a mangrove and the sea. This research was conducted in a mangrove at Coroa Grande, on the southern coast of Rio de Janeiro. Samples were collected at three stations: (1) region colonised by Rhizophora mangle L. on the edge of the mangrove, (2) region colonised by seagrasses and (3) infra-littoral region without vegetation. Samples were collected from the surface layer of the sediment to determine the concentrations of nutrients (C, N and P) and CH4 concentration and production. We observed that concentrations of CH4 and carbon (C) were significantly higher (p < 0.05) in station 1 than station 3. The molar ratios (C:N, C:P and N:P) suggest that the origin of the substrate is mainly autochthonous. Methanogenesis was initially low, possibly due to competition between methanogens and sulfate reducers, and increased significantly (p < 0.05) on the twenty-sixth day in the sediment of station 1, probably due to higher organic matter (OM) availability in this region. Results indicate that methanogenic activity observed herein is not regulated by the amount or quality of OM, but by other factors. The concentration of CH4 in the sea-land ecotone at Mangrove Coroa Grande is a function of available OM suggesting a possible inhibition of methanotrophy by intense oxygen consumption in the soil surface covered by detritus of Rhizophora mangle vegetation.

3D Simulations of methane convective storms on Titan's atmosphere

NASA Astrophysics Data System (ADS)

Hueso, R.; Sánchez-Lavega, A.

2005-08-01

The arrival of the Cassini/Huygens mission to Titan has opened an unprecedented opportunity to study the atmosphere of this satellite. Under the pressure-temperature conditions on Titan, methane, a large atmospheric component amounting perhaps to a 3-5% of the atmosphere, is close to its triple point, potentially playing a similar role as water on Earth. The Huygens probe has shown a terrain shaped by erosion of probably liquid origin, suggestive of past rain. On the other hand, Voyager IRIS spectroscopic observations of Titan imply a saturated atmosphere of methane (amounting perhaps to 150 covered by methane clouds, if we think on Earth meteorology. However, observations from Earth and Cassini have shown that clouds are localized, transient and fast evolving, in particular in the South Pole (currently in its summer season). This might imply a lack of widespread presence on Titan of nuclei where methane could initiate condensation and particle growth with subsequent precipitation. We investigate different scenarios of moist convective storms on Titan using a complete 3D atmospheric model that incorporates a full microphysics treatment required to study cloud formation processes under a saturated atmosphere with low concentration of condensation nuclei. We study local convective development under a variety of atmospheric conditions: sub-saturation, super-saturation, abundances of condensation nuclei fall, condensation nuclei lifted from the ground or gently falling from the stratosphere. We show that under the appropriate circumstances, precipitation rates comparable to typical tropical storms on Earth can be found. Acknowledgements: This work has been funded by Spanish MCYT PNAYA2003-03216, fondos FEDER and Grupos UPV 15946/2004. R. Hueso acknowledges a post-doc fellowship from Gobierno Vasco.

Dissolved Organic Carbon: Nitrate Ratios as a Driver of Methane Fluxes in Stream Ecosystems

NASA Astrophysics Data System (ADS)

Sullivan, B. W.; Wymore, A.; Schade, J. D.; McDowell, W. H.

2016-12-01

Fluvial ecosystems are poorly understood components of the global methane (CH4) budget because the ecology of CH4 fluxes in streams has yet to be sufficiently elucidated. Both CH4 production and uptake via oxidation are microbially mediated processes, but it is unclear where in the fluvial environment are the sources and sinks of CH4 and what role terrestrial inputs of carbon (C) and nutrients have on the magnitude and direction of CH4 flux. To address these uncertainties, we measured CH4 fluxes in a laboratory incubation from two temperate headwater streams that differed in ambient dissolved organic carbon (DOC) and nitrate (NO3-) concentrations. We amended stream water and sediment microcosms from each site with labile DOC from senesced leaf litter to assess how DOC concentration and the DOC:NO3- ratio affect proximate controls on CH4 flux. Lastly, we manipulated sediment and water column ratios (0-100%) to estimate sources and fates of CH4 flux within the ecosystem. We measured CH4 fluxes for the first 120 minutes of the incubation to simulate short-term, in stream processes. Initially, streams were a source of methane, but switched to a sink within 120 minutes. Methane fluxes were statistically similar in both stream sediment and water, suggesting that microbial processing of CH4 has similar directionality and magnitude in each environment. Both CH4 oxidation and production were significantly correlated with the DOC: NO3- ratio over the course of the incubation. Early in the incubation, increasing DOC: NO3- increased CH4 flux, but late in the incubation, increasing DOC: NO3- increased CH4 oxidation. Together, our results challenge existing paradigms of CH4 flux in the fluvial environment and identify the DOC:NO3- ratio as a possible mechanism that can explain spatial and temporal CH4 flux patterns in streams.

Effect of biomass concentration on methane oxidation activity using mature compost and graphite granules as substrata.

PubMed

Xie, S; O'Dwyer, T; Freguia, S; Pikaar, I; Clarke, W P

2016-10-01

Reported methane oxidation activity (MOA) varies widely for common landfill cover materials. Variation is expected due to differences in surface area, the composition of the substratum and culturing conditions. MOA per methanotrophic cell has been calculated in the study of natural systems such as lake sediments to examine the inherent conditions for methanotrophic activity. In this study, biomass normalised MOA (i.e., MOA per methanotophic cell) was measured on stabilised compost, a commonly used cover in landfills, and on graphite granules, an inert substratum widely used in microbial electrosynthesis studies. After initially enriching methanotrophs on both substrata, biomass normalised MOA was quantified under excess oxygen and limiting methane conditions in 160ml serum vials on both substrata and blends of the substrata. Biomass concentration was measured using the bicinchoninic acid assay for microbial protein. The biomass normalised MOA was consistent across all compost-to-graphite granules blends, but varied with time, reflecting the growth phase of the microorganisms. The biomass normalised MOA ranged from 0.069±0.006μmol CH4/mg dry biomass/h during active growth, to 0.024±0.001μmol CH4/mg dry biomass/h for established biofilms regardless of the substrata employed, indicating the substrata were equally effective in terms of inherent composition. The correlation of MOA with biomass is consistent with studies on methanotrophic activity in natural systems, but biomass normalised MOA varies by over 5 orders of magnitude between studies. This is partially due to different methods being used to quantify biomass, such as pmoA gene quantification and the culture dependent Most Probable Number method, but also indicates that long term exposure of materials to a supply of methane in an aerobic environment, as can occur in natural systems, leads to the enrichment and adaptation of types suitable for those conditions. Copyright © 2016 Elsevier Ltd. All rights reserved.

Magnetic Diagenesis in the Gas Hydrate System

NASA Astrophysics Data System (ADS)

Enkin, R. J.; Hamilton, T. S.; Esteban, L.

2009-05-01

Natural gas hydrate is a methane-bearing form of ice which occurs in permafrost and continental slope settings. Geochemical processes associated with gas hydrate formation lead to the growth of iron sulphides which have a geophysically measurable magnetic signature. Detailed magnetic investigation and complementary petrological observations were undertaken on unconsolidated sediments from three gas hydrate (GH) settings: permafrost in fluvial-deltaic silts and sands in the Western Canadian Arctic (Japex et al. Mallik 5L-38 in 2002); diamictons and hemipelagics in the Cascadia accretionary wedge west of Vancouver Island (IODP Exp.311 in 2006); and marine sands and hemipelagics from the Bay of Bengal (NGHP Exp.01 in 2007). These magnetic measurements provide stratigraphic profiles which reveal fine scale variations in lithology, magnetic grain size, and paleo-pore fluid geochemistry. The highest magnetic susceptibility values are observed in strata which preserve high initial concentrations of detrital magnetite, such as glacial deposits. The lowest values of magnetic susceptibility are observed where iron has been reduced to paramagnetic pyrite, formed in settings with high methane and sulphate flux such as at methane vents. Enhanced values of magnetic susceptibility characterize the introduction of the ferrimagnetic iron sulphide minerals greigite and smythite. These magnetic minerals are mostly found immediately adjacent to the sedimentary horizons which host the gas hydrate and their textures and compositions indicate rapid disequilibrium crystallization. The observed diagenesis result from the unique physical and geochemical properties of the environment where gas hydrates form: methane is available to fuel microbiological activity and the freezing which accompanied GH crystallization quickly removed pure water, froze the sediments into an impermeable solid and expelled more concentrated brines into the adjacent less permeable strata to the point of inducing fracture formation. Magnetic surveying techniques can help delineate anomalies related to gas hydrate deposits, and magnetic logging of wells and core samples provide information on the original lithology and diagenesis caused by gas hydrate formation.

Anaerobic degradation of aircraft deicing fluid (ADF) in upflow anaerobic sludge blanket (UASB) reactors and the fate of ADF additives

NASA Astrophysics Data System (ADS)

Pham, Thi Tham

2002-11-01

A central composite design was employed to methodically investigate anaerobic treatment of aircraft deicing fluid (ADF) in bench-scale Upflow Anaerobic Sludge Blanket (UASB) reactors. A total of 23 runs at 17 different operating conditions were conducted in continuous mode. The development of four empirical models describing process responses (i.e., chemical oxygen demand (COD) removal efficiency, biomass specific acetoclastic activity, methane production rate, and methane production potential) as functions of ADF concentration, hydraulic retention time (HRT), and biomass concentration is presented. Model verification indicated that predicted responses (COD removal efficiencies, biomass specific acetoclastic activity, and methane production rates and potential) were in good agreement with experimental results. Biomass specific acetoclastic activity was improved by almost two-fold during ADF treatment in UASB reactors. For the design window, COD removal efficiencies were higher than 90%. Predicted methane production potentials were close to theoretical values, and methane production rates increased as the organic loading rate (OLR) was increased. ADF toxicity effects were evident for 1.6% ADF at medium specific organic loadings (SOLR above 0.5 g COD/g VSS/d). In contrast, good reactor stability and excellent removal efficiencies were achieved at 1.2% ADF for reactor loadings approaching that of highly loaded systems (0.73 g COD/g VSS/d). Acclimation to ADF resulted in an initial reduction in the biomass settling velocity. The fate of ADF additives was also investigated. There was minimal sorption of benzotriazole (BT), 5-methyl-1 H-benzotriazole (MeBT), and 5,6-dimethyl-1 H-benzotriazole (DiMeBT) to anaerobic granules. A higher sorption capacity was measured for NP. Active transport may be one of the mechanisms for NP sorption. Ethylene glycol degradation experiments indicated that BT, MeBT, DiMeBT, and the nonionic surfactant Tergitol NP-4 had no significant effects on acidogenesis and methanogenesis at the concentration levels studied. A significant inhibition of acetoclastic activity was observed for NP at 100 mg/L, with acetic acid consumption rate at 38% of that for controls. No evidence for anaerobic degradation of benzotriazole and its derivatives was observed; however, both batch and continuous experiments suggested that anaerobic degradation of NP occurred. Kinetic analysis of operational data obtained for the anaerobic treatment of ADF in UASB reactors indicated that the substrate utilization rate was independent of the reactor biomass concentration. The maximum rate of substrate utilization and the half-velocity constants for ADF treatment were 28.4 g COD/L/d and 648 mg COD/L, respectively. For 1.2% ADF, the biomass yield and endogenous decay coefficients were 0.027 g VSS/g COD and 0.012 d-1 , respectively.

Factors controlling the concentration of methane and other volatiles in groundwater and soil-gas around a waste site

NASA Astrophysics Data System (ADS)

Barber, C.; Davis, G. B.; Briegel, D.; Ward, J. K.

1990-01-01

The concentration of methane in groundwater and soil-gas in the vicinity of a waste landfill on an unconfined sand aquifer has been investigated in detail. These data have been used to evaluate techniques which use volatile organic compounds in soil-gas as indicators of groundwater contamination. Simple one-dimensional models of gas advection and diffusion have been adapted for use in the study. Lateral advection of gas in the unsaturated sand was found to be seasonal and was most noticeable in winter when the profile was wet; a mean velocity of 1 m d - was measured from breakthrough of a helium tracer in an injection test. The effects of advection on trace concentrations of methane in soil-gas were limited to within 150-200m from the waste site and resulted from pressure gradients brought about by positive gas pressures in the landfill, and also as a result of ebullition (gas bubbling) from contaminated groundwater. The distribution of methane in soil-gas at shallow (2m) depth gave a general indication of the direction of movement of contaminants with groundwater in close proximity to the landfill. Outside this zone, diffusional transport of methane from groundwater to soil-gas occurred and methane in soil-gas sampled close to the water table was found to be a useful indicator of contaminated groundwater. Modelling the exchange of volatiles between aqueous and gas phases indicates that a wide range of organic compounds, particularly those with Henry's Law constants greater than 2.5 × 10 t-2 kPam 3mol -1, would have potential for use as indicators of pollution, if these were present in groundwater and they behaved relatively conservatively. In general, the principal factors controlling the concentration of these volatiles in soil-gas were the concentration gradient at the water table and capillary fringe and the ratio of diffusion coefficients in the saturated and unsaturated zones.

40 CFR 60.612 - Standards.

Code of Federal Regulations, 2010 CFR

2010-07-01

... start-up, whichever date comes first. Each owner or operator shall either: (a) Reduce emissions of TOC (minus methane and ethane) by 98 weight-percent, or to a TOC (minus methane and ethane) concentration of...

Multi-scale monitoring of a marine geologic methane source in the Santa Barbara Channel using imaging spectrometry, ARCTAS-CARB in situ sampling and coastal hourly total hydrocarbon measurements

NASA Astrophysics Data System (ADS)

Bradley, E. S.; Leifer, I.; Roberts, D.; Dennison, P. E.; Margolis, J.; Moritsch, M.; Diskin, G. S.; Sachse, G. W.

2009-12-01

The Coal Oil Point (COP) hydrocarbon seep field off the coast of Santa Barbara, CA is one of the most active and best-studied marine geologic methane sources in the world and contributes to elevated terrestrial methane concentrations downwind. In this study, we investigate the spatiotemporal variability of this local source and the influence of meteorological conditions on transport and concentration. A methane plume emanating from Trilogy Seep was mapped with the Airborne Visible Infrared Imaging Spectrometer at a 7.5 m resolution with a short-wave infrared band ratio technique. This structure agrees with the local wind speed and direction and is orthogonal to the surface currents. ARCTAS-CARB aircraft in situ sampling of lower-troposphere methane is compared to sub-hour total hydrocarbon concentration (THC) measurements from the Santa Barbara Air Pollution Control District (SBAPCD) station located near COP. Hourly SBAPCD THC values from 1980-2008 demonstrate a decrease in seep source strength until the late 1990s, followed by a consistent increase. The occurrence of elevated SBAPCD THC values for onshore wind conditions as well as numerous positive outliers as high as 17 ppm suggests that seep field emissions are both quasi-steady state and transient, direct (bubble) and diffuse (outgassing). As demonstrated for the COP seeps, the combination of imaging spectrometry, aircraft in situ sampling, and ground-based monitoring provides a powerful approach for understanding local methane sources and transport processes.

Methyl-coenzyme M reductase A as an indicator to estimate methane production from dairy cows.

PubMed

Aguinaga Casañas, M A; Rangkasenee, N; Krattenmacher, N; Thaller, G; Metges, C C; Kuhla, B

2015-06-01

The evaluation of greenhouse gas mitigation strategies requires the quantitative assessment of individual methane production. Because methane measurement in respiration chambers is highly accurate, but also comprises various disadvantages such as limited capacity and high costs, the establishment of an indicator for estimating methane production of individual ruminants would provide an alternative to direct methane measurement. Methyl-coenzyme M reductase is involved in methanogenesis and the subunit α of methyl-coenzyme M reductase is encoded by the mcrA gene of rumen archaea. We therefore examined the relationship between methane emissions of Holstein dairy cows measured in respiration chambers with 2 different diets (high- and medium-concentrate diet) and the mcrA DNA and mcrA cDNA abundance determined from corresponding rumen fluid samples. Whole-body methane production per kilogram of dry matter intake and mcrA DNA normalized to the abundance of the rrs gene coding for 16S rRNA correlated significantly when using qmcrA primers. Use of qmcrA primers also revealed linear correlation between mcrA DNA copy number and methane yield. Regression analyses based on normalized mcrA cDNA abundances revealed no significant linear correlation with methane production per kilogram of dry matter intake. Furthermore, the correlations between normalized mcrA DNA abundance and the rumen fluid concentration of acetic and isobutyric acid were positive, whereas the correlations with propionic and lactic acid were negative. These data suggest that the mcrA DNA approach based on qmcrA primers could potentially be a molecular proxy for methane yield after further refinement. Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

Hydrologic controls of methane dynamics in a karst subterranean estuary

NASA Astrophysics Data System (ADS)

Brankovits, D.; Pohlman, J.; Ganju, N. K.; Lowell, N. S.; Roth, E.; Lapham, L.

2017-12-01

Subterranean estuaries extend into carbonate landmasses where abundant cave networks influence the hydrology and biogeochemistry of the coastal aquifer environment. Enhanced density stratification between meteoric freshwater and saline groundwater facilitates the development of sharp salinity and redox gradients associated with the production and consumption of methane, a potent greenhouse gas. These processes impact methane-dynamics in the coastal zone and provide nutritive resources for the cave-adapted estuarine food web in this oligotrophic habitat. These observations were based on sampling in discrete time periods, leaving questions about the effects of temporally dynamic hydrology on the production, consumption and transport of methane. In this study, we evaluated hydro-biogeochemical controls of methane dynamics in a subterranean estuary to quantify the magnitude of the methane sink in the coastal karst platform of the Yucatan Peninsula, Mexico. We deployed osmotically-driven sampling devices (OsmoSamplers) in flooded cave passages to document temporal variability in methane concentrations and δ13C values, as well as major ions in the groundwater. Water level, current velocities, water and air temperatures, and precipitation were also monitored. Using these records, we built an integrated model to provide a first-order calculation on methane consumption rates for the coastal aquifer. The year-long water chemistry record reveals higher source concentrations of methane in the dry season (5849 ± 1198 nM) than in the wet season (4265 ± 778 nM) with depleted δ13C values (-65.4 ± 2.1 ‰) throughout the year. Our analyses suggest the methane sink potential and ecosystem function are significantly affected by precipitation induced hydrological changes within the tropical subterranean karst estuary.

Metabolic activity of subterranean microbial communities in deep granitic groundwater supplemented with methane and H2

PubMed Central

Pedersen, Karsten

2013-01-01

It was previously concluded that opposing gradients of sulphate and methane, observations of 16S ribosomal DNA sequences displaying great similarity to those of anaerobic methane-oxidizing Archaea and a peak in sulphide concentration in groundwater from a depth of 250–350 m in Olkiluoto, Finland, indicated proper conditions for methane oxidation with sulphate. In the present research, pressure-resistant, gas-tight circulating systems were constructed to enable the investigation of attached and unattached anaerobic microbial populations from a depth of 327 m in Olkiluoto under in situ pressure (2.4 MPa), diversity, dissolved gas and chemistry conditions. Three parallel flow cell cabinets were configured to allow observation of the influence on microbial metabolic activity of 11 mℳ methane, 11 mℳ methane plus 10 mℳ H2 or 2.1 mℳ O2 plus 7.9 mℳ N2 (that is, air). The concentrations of these gases and of organic acids and carbon, sulphur chemistry, pH and Eh, ATP, numbers of cultivable micro-organisms, and total numbers of cells and bacteriophages were subsequently recorded under batch conditions for 105 days. The system containing H2 and methane displayed microbial reduction of 0.7 mℳ sulphate to sulphide, whereas the system containing only methane resulted in 0.2 mℳ reduced sulphate. The system containing added air became inhibited and displayed no signs of microbial activity. Added H2 and methane induced increasing numbers of lysogenic bacteriophages per cell. It appears likely that a microbial anaerobic methane-oxidizing process coupled to acetate formation and sulphate reduction may be ongoing in aquifers at a depth of 250–350 m in Olkiluoto. PMID:23235288

Utilization of coal mine methane for methanol and SCP production. Topical report, May 5, 1995--March 4, 1996

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1998-12-31

The feasibility of utilizing a biological process to reduce methane emissions from coal mines and to produce valuable single cell protein (SCP) and/or methanol as a product has been demonstrated. The quantities of coal mine methane from vent gas, gob wells, premining wells and abandoned mines have been determined in order to define the potential for utilizing mine gases as a resource. It is estimated that 300 MMCFD of methane is produced in the United States at a typical concentration of 0.2-0.6 percent in ventilation air. Of this total, almost 20 percent is produced from the four Jim Walter Resourcesmore » (JWR) mines, which are located in very gassy coal seams. Worldwide vent gas production is estimated at 1 BCFD. Gob gas methane production in the U.S. is estimated to be 38 MMCFD. Very little gob gas is produced outside the U.S. In addition, it is estimated that abandoned mines may generate as much as 90 MMCFD of methane. In order to make a significant impact on coal mine methane emissions, technology which is able to utilize dilute vent gases as a resource must be developed. Purification of the methane from the vent gases would be very expensive and impractical. Therefore, the process application must be able to use a dilute methane stream. Biological conversion of this dilute methane (as well as the more concentrated gob gases) to produce single cell protein (SCP) and/or methanol has been demonstrated in the Bioengineering Resources, Inc. (BRI) laboratories. SCP is used as an animal feed supplement, which commands a high price, about $0.11 per pound.« less

Comparative Analysis of the Methane Data Products from the Tropospheric Emission Spectrometer and the Atmospheric Infrared Sounder.

NASA Astrophysics Data System (ADS)

Pagano, T. J.; Worden, J. R.

2016-12-01

Methane is the second most powerful greenhouse gas with a highly positive radiative forcing of 0.48 W/m2 (IPCC 2013). Global concentrations of methane have been steadily increasing since 2007 (Bruhwiler 2014), raising concerns about methane's impact on the future global climate. For about the last decade, the Tropospheric Emission Spectrometer (TES) on the Earth Observing System (EOS) Aura spacecraft has been detecting several trace gas species in the troposphere including methane. The goal of this study is to compare TES methane products to that of the Atmospheric Infrared Sounder (AIRS) on the EOS Aqua spacecraft so that scientific investigations may be transferred from TES to AIRS. The two instruments fly in the afternoon constellations (A-Train), providing numerous coincident measurements for comparison. In addition, they also have a similar spectral range, (3.3 to 15.4 µm) for TES (Beer, 2006) and (3.7 to 15.4 µm) for AIRS (Chahine, 2006), making both satellites sensitive to the mid and upper troposphere. This makes them ideal candidates to compare methane data products. In a previous study, total column methane was mapped and global zonal averages were compared. It was found that bias of the total column measurements between the two sounders was about constant over tropical and subtropical regions. However, because AIRS spectral resolution is lower than that of the TES, it is important to analyze the difference in vertical sensitivity. In this study, we will construct vertical profiles of methane concentration and compare them statistically through RMS difference and bias to better understand these differences. In addition, we will compare the error profile and total column errors of the TES and AIRS methane from the data to better understand error characteristics of the products.

Increasing the concentration of linolenic acid in diets fed to Jersey cows in late lactation does not affect methane production

USDA-ARS?s Scientific Manuscript database

Oil and fat products has shown to reduce methane, however, limited research compares different fat sources effects on methane production. A study using 8 multiparous (325 ± 17 DIM) (mean ± SD) lactating dairy cows, was conducted to determine effects of feeding canola/tallow vs. extruded byproduct co...

Two Mechanisms for Methane Release at the Paleocene/Eocene Boundary

NASA Astrophysics Data System (ADS)

Katz, M. E.; Cramer, B. S.; Mountain, G. S.; Mountain, G. S.; Katz, S.; Miller, K. G.; Miller, K. G.

2001-12-01

The rapid global warming of the Paleocene/Eocene thermal maximum (PETM) has been attributed to a massive methane release from marine gas hydrate reservoirs. Two mechanisms have been proposed for this methane release. The first relies on a deepwater circulation change and water temperature increase that was sufficiently large and rapid to trigger massive thermal dissociation of gas hydrate frozen beneath the seafloor (Dickens et al., 1995). The second relies on slope failure (via erosion or seismic activity) of the oversteepened continental margins of the western North Atlantic to allow methane to escape from gas reservoirs trapped between the hydrate-bearing sediments and the underlying reef front (Katz et al., in press). We evaluate thermal dissociation by modeling heat flow through the sediments to show the effect of the temperature change on the gas hydrate stability zone through time. We use Paleocene bottom water temperatures (constrained by isotope records) and assume an instantaneous water temperature increase (i.e., no time allotted for ocean circulation change and water mass mixing). This yields an end-member minimum estimate of >2350 years necessary to melt all gas hydrate at locations shallower than 1570m; gas hydrates at greater depths remain frozen. We also use this model to predict the amount of C12-enriched methane that could have contributed to the carbon isotope excursion (CIE). Using reasonable methane distributions within sediments, we conclude that thermal dissociation alone cannot account for the full magnitude of the CIE. We propose that thermal dissociation did not initiate the CIE; rather, a different mechanism injected a large amount of carbon into the atmosphere, causing global greenhouse warming that could have led to subsequent thermal dissociation. Methane remains a plausible source for this initial carbon injection; however, initial release would have resulted from mechanical disruption of sediments rather than thermal dissociation. Seismic evidence tied to borehole data shows that methane may have been released from the U.S. continental slope in areas proximal to a buried Mesozoic reef, in contrast to the broader depth range predicted for methane release via thermal dissociation.

Methane emission from animals: A Global High-Resolution Data Base

NASA Astrophysics Data System (ADS)

Lerner, Jean; Matthews, Elaine; Fung, Inez

1988-06-01

We present a high-resolution global data base of animal population densities and associated methane emission. Statistics on animal populations from the Food and Agriculture Organization and other sources have been compiled. Animals were distributed using a 1° resolution data base of countries of the world and a 1° resolution data base of land use. The animals included are cattle and dairy cows, water buffalo, sheep, goats, camels, pigs, horses and caribou. Published estimates of methane production from each type of animal have been applied to the animal populations to yield a global distribution of annual methane emission by animals. There is large spatial variability in the distribution of animal populations and their methane emissions. Emission rates greater than 5000 kg CH4 km-2 yr-1 are found in small regions such as Bangladesh, the Benelux countries, parts of northern India, and New Zealand. Of the global annual emission of 75.8 Tg CH4 for 1984, about 55% is concentrated between 25°N and 55°N, a significant contribution to the observed north-south gradient of atmospheric methane concentration. A magnetic tape of the global data bases is available from the authors.

Why Methane Increasing in the Atmosphere is Pushing us Towards New Analytical Approaches for Stable Isotope Ratios

NASA Astrophysics Data System (ADS)

White, J. W. C.; Michel, S. E.; Vaughn, B. H.; Miller, J. B.; Masarie, K. A.; Dlugokencky, E. J.; Sherwood, O.; Tans, P. P.

2015-12-01

Methane is increasing again in the atmosphere after nearly a decade of stable concentrations. As methane has risen by 2.5 times since the beginning of the industrial era, such a rise in concentrations is not surprising. Carbon isotopes, however, make it clear that the recent rise is not simply a resumption of the dramatic rise in the 1900s, but that other causes are at play, and that multiple fluxes may be interacting to yield the observed rise. At the same time, cautious attention is focused on the Arctic, where vast stores of carbon are poised for release as frozen soils melt, and some of that carbon will be released as methane. These realities make it imperative that we improve our monitoring of methane and methane isotopes in the atmosphere. This talk will address the issues that we face in meeting this challenge in the NOAA Global Greenhouse Gas Reference Network, including targets for precision and accuracy needed to calculate regional and global fluxes, technological advances in analytical equipment, maintaining standards, ensuring adequate monitoring sites and meeting all of these needs in an era of funding cuts and uncertainty for environmental monitoring.

The fate of ethane in Titan's hydrocarbon lakes and seas

NASA Astrophysics Data System (ADS)

Mousis, Olivier; Lunine, Jonathan I.; Hayes, Alexander G.; Hofgartner, Jason D.

2016-05-01

Ethane is expected to be the dominant photochemical product on Titan's surface and, in the absence of a process that sequesters it from exposed surface reservoirs, a major constituent of its lakes and seas. Absorption of Cassini's 2.2 cm radar by Ligeia Mare however suggests that this north polar sea is dominated by methane. In order to explain this apparent ethane deficiency, we explore the possibility that Ligeia Mare is the visible part of an alkanofer that interacted with an underlying clathrate layer and investigate the influence of this interaction on an assumed initial ethane-methane mixture in the liquid phase. We find that progressive liquid entrapment in clathrate allows the surface liquid reservoir to become methane-dominated for any initial ethane mole fraction below 0.75. If interactions between alkanofers and clathrates are common on Titan, this should lead to the emergence of many methane-dominated seas or lakes.

Methane Leakage From Hydrocarbon Wellbores into Overlying Groundwater: Numerical Investigation of the Multiphase Flow Processes Governing Migration

NASA Astrophysics Data System (ADS)

Rice, Amy K.; McCray, John E.; Singha, Kamini

2018-04-01

Methane leakage due to compromised hydrocarbon well integrity can lead to impaired groundwater quality. Here we use a three-dimensional, multiphase (vapor and aqueous), multicomponent (methane, water, salt), numerical model (TOUGH2 EOS7C) to investigate hydrogeological conditions that could result in groundwater contamination from natural gas wellbore leakage that migrates upward toward a freshwater aquifer. The conceptual model used for the simulations assumes methane leakage at 20-30 m below groundwater. We perform 180 simulations for a sensitivity analysis, examining (1) multiphase flow parameters related to storage, capillarity, and relative permeability, including porosity (ϕ), initial fluid-phase saturation (SL), and van Genuchten n and α, (2) geostatistical variations in intrinsic permeability (ki), and (3) methane source-zone pressure. Simulated mean ki values are 10-18 and 10-13 m2 with variances of 1 and 5 m4. Simulated source-zone pressures range from just over ambient hydrostatic pressure at the depth of leakage (100 kPa) to the maximum pressure that steel casings are commonly rated to withstand (20,340 kPa). ki, initial SL, ϕ, and van Genuchten's n and α were the most important parameters in determining the volume of methane reaching groundwater during a given time period. Multiphase parameterization of formations underlying freshwater aquifers and overlying hydrocarbon production zones is fundamental to assessing aquifer vulnerability to methane leakage.

Identification and characterization of high methane-emitting abandoned oil and gas wells

PubMed Central

Kang, Mary; Christian, Shanna; Celia, Michael A.; Mauzerall, Denise L.; Bill, Markus; Miller, Alana R.; Chen, Yuheng; Conrad, Mark E.; Darrah, Thomas H.; Jackson, Robert B.

2016-01-01

Recent measurements of methane emissions from abandoned oil/gas wells show that these wells can be a substantial source of methane to the atmosphere, particularly from a small proportion of high-emitting wells. However, identifying high emitters remains a challenge. We couple 163 well measurements of methane flow rates; ethane, propane, and n-butane concentrations; isotopes of methane; and noble gas concentrations from 88 wells in Pennsylvania with synthesized data from historical documents, field investigations, and state databases. Using our databases, we (i) improve estimates of the number of abandoned wells in Pennsylvania; (ii) characterize key attributes that accompany high emitters, including depth, type, plugging status, and coal area designation; and (iii) estimate attribute-specific and overall methane emissions from abandoned wells. High emitters are best predicted as unplugged gas wells and plugged/vented gas wells in coal areas and appear to be unrelated to the presence of underground natural gas storage areas or unconventional oil/gas production. Repeat measurements over 2 years show that flow rates of high emitters are sustained through time. Our attribute-based methane emission data and our comprehensive estimate of 470,000–750,000 abandoned wells in Pennsylvania result in estimated state-wide emissions of 0.04–0.07 Mt (1012 g) CH4 per year. This estimate represents 5–8% of annual anthropogenic methane emissions in Pennsylvania. Our methodology combining new field measurements with data mining of previously unavailable well attributes and numbers of wells can be used to improve methane emission estimates and prioritize cost-effective mitigation strategies for Pennsylvania and beyond. PMID:27849603

Exploring the metabolic potential of microbial communities in ultra-basic, reducing springs at The Cedars, CA, USA: Experimental evidence of microbial methanogenesis and heterotrophic acetogenesis

NASA Astrophysics Data System (ADS)

Kohl, Lukas; Cumming, Emily; Cox, Alison; Rietze, Amanda; Morrissey, Liam; Lang, Susan Q.; Richter, Andreas; Suzuki, Shino; Nealson, Kenneth H.; Morrill, Penny L.

2016-04-01

Present-day serpentinization generates groundwaters with conditions (pH > 11, Eh < -550 mV) favorable for the microbial and abiotic production of organic compounds from inorganic precursors. Elevated concentrations of methane, C2-C6 alkanes, acetate, and formate have been detected at these sites, but the microbial or abiotic origin of these compounds remains unclear. While geochemical data indicate that methane at most sites of present-day serpentinization is abiogenic, the stable carbon, hydrogen, and clumped isotope data as well as the hydrocarbon gas composition from The Cedars, CA, USA, are consistent with a microbial origin for methane. However, there is no direct evidence of methanogenesis at this site of serpentinization. We report on laboratory experiments in which the microbial communities in fluids and sediments from The Cedars were incubated with 13C labeled substrates. Increasing methane concentrations and the incorporation of 13C into methane in live experiments, but not in killed controls, demonstrated that methanogens converted methanol, formate, acetate (methyl group), and bicarbonate to methane. The apparent fractionation between methane and potential substrates (α13CCH4-CO2(g) = 1.059 to 1.105, α13CCH4-acetate = 1.042 to 1.119) indicated that methanogenesis was dominated by the carbonate reduction pathway. Increasing concentrations of volatile organic acid anions indicated microbial acetogenesis. α13CCO2(g)-acetate values (0.999 to 1.000), however, were inconsistent with autotrophic acetogenesis, thus suggesting that acetate was produced through fermentation. This is the first study to show direct evidence of microbial methanogenesis and acetogenesis by the native microbial community at a site of present-day serpentinization.

Kinetics and methane gas yields of selected C1 to C5 organic acids in anaerobic digestion.

PubMed

Yang, Yu; Chen, Qian; Guo, Jialiang; Hu, Zhiqiang

2015-12-15

Volatile fatty acids (VFAs) and other short-chain organic acids such as lactic and pyruvic acids are intermediates in anaerobic organic degradation. In this study, anaerobic degradation of seven organic acids in salt form was investigated, including formate (C1), acetate (C2), propionate (C3), pyruvate (C3), lactate (C3), butyrate (C4), and valerate (C5). Microbial growth kinetics on these organic acids were determined individually at 37 °C through batch anaerobic digestion tests by varying substrate concentrations from 250 to 4000 mg COD/L. The cumulative methane generation volume was determined real-time by respirometry coupled with gas chromatographic analysis while methane yield and related kinetics were calculated. The methane gas yields (fe, mg CH4 COD/mg substrate COD) from anaerobic degradation of formate, acetate, propionate, pyruvate, lactate, butyrate, and valerate were 0.44 ± 0.27, 0.58 ± 0.05, 0.53 ± 0.18, 0.24 ± 0.05, 0.17 ± 0.05, 0.43 ± 0.15, 0.49 ± 0.11, respectively. Anaerobic degradation of formate showed self-substrate inhibition at the concentrations above 3250 mg COD/L. Acetate, propionate, pyruvate, butyrate, lactate, and valerate did not inhibit methane production at the highest concentrations tested (i.e., 4000 mg COD/L). Microbes growing on acetate had the highest overall specific growth rate (0.30 d(-1)) in methane production. For comparison, the specific microbial growth rates on formate, propionate, pyruvate, butyrate, lactate, and valerate for methane production were 0.10, 0.06, 0.08, 0.07, 0.05, 0.15 d(-1), respectively. Copyright © 2015 Elsevier Ltd. All rights reserved.

Trace gas transport out of the Indian Summer Monsoon

NASA Astrophysics Data System (ADS)

Tomsche, Laura; Pozzer, Andrea; Zimmermann, Peter; Parchatka, Uwe; Fischer, Horst

2016-04-01

The trace gas transport out of the Indian summer monsoon was investigated during the aircraft campaign OMO (Oxidation Mechanism Observations) with the German research aircraft HALO (High Altitude and Long Range Research Aircraft) in July/August 2015. HALO was based at Paphos/Cyprus and also on Gan/Maledives. Flights took place over the Mediterranean Sea, the Arabian Peninsula and the Arabian Sea. In this work the focus is on the distribution of carbon monoxide (CO) and methane (CH4) in the upper troposphere. They were measured with the laser absorption spectrometer TRISTAR on board of HALO. During the Indian summer monsoon strong convection takes place over India and the Bay of Bengal. In this area the population is high accompanied by many emission sources e.g. wetlands and cultivation of rice. Consequently the boundary layer is polluted containing high concentrations of trace gases like methane and carbon monoxide. Due to vertical transport these polluted air masses are lifted to the upper troposphere. Here they circulate with the so called Asian monsoon anticyclone. In the upper troposphere polluted air masses lead to a change in the chemical composition thus influence the chemical processes. Furthermore the anticyclone spreads the polluted air masses over a larger area. Thus the outflow of the anticyclone in the upper troposphere leads to higher concentrations of trace gases over the Arabian Sea, the Arabian Peninsula and also over the eastern part of North Africa and the eastern part of the Mediterranean Sea. During OMO higher concentrations of methane and carbon monoxide were detected at altitudes between 11km and 15km. The highest measured concentrations of carbon monoxide and methane were observed over Oman. The CO concentration in the outflow of the monsoon exceeds background levels by 10-15ppb. However the enhancement in the concentration is not obviously connected to the monsoon due to the natural variability in the troposphere. The enhancement in the methane concentration (30-40ppb) is more obviously connected to the monsoon because it is much higher than the natural variability. Consequently methane is a very good tracer for the monsoon influenced air masses. Beside flights into the outflow of the Indian summer monsoon, there were also measurements of background concentrations in the upper troposphere in air not influenced by the monsoon. Profiles have shown that the high concentrations of trace gases are only observed in the upper troposphere. The high concentrations in the upper troposphere cannot be explained by vertical transport form local ground sources.

Investigation of hydrate formation in the system H2-CH4-H2O at a pressure up to 250 MPa.

PubMed

Skiba, Sergei S; Larionov, Eduard G; Manakov, Andrey Y; Kolesov, Boris A; Kosyakov, Viktor I

2007-09-27

Phase equilibria in the system H2-CH4-H2O are investigated by means of differential thermal analysis within hydrogen concentration range 0-70 mol % and at a pressure up to 250 MPa. All the experiments were carried out under the conditions of gas excess. With an increase in hydrogen concentration in the initial gas mixture, decomposition temperature of the formed hydrates decreased. X-ray diffraction patterns and Raman spectra of the quenched hydrate samples obtained at a pressure of 20 MPA from a gas mixture containing 40 mol % hydrogen were recorded. It turned out that the hydrate has cubic structure I under these conditions. The Raman spectra showed that hydrogen molecules are not detected in the hydrate within the sensitivity of the method, that is, almost pure methane hydrate is formed. The general view of the phase diagram of the investigated system is proposed. A thermodynamic model was proposed to explain a decrease in hydrate decomposition temperature in the system with an increase in the concentration of hydrogen in the initial mixture.

Effect of forage to concentrate ratio in dairy cow diets on emission of methane, carbon dioxide and ammonia, lactation performance and manure excretion

USDA-ARS?s Scientific Manuscript database

Holstein cows housed in a modified tie-stall barn were used to determine the effect of feeding diets with different forage to concentrate ratios (F:C) on performance and emission of methane (CH4), carbon dioxide (CO2) and manure ammonia-nitrogen (NH3-N). Eight multiparous cows (means ± standard devi...

Influence of Different Plant Species on Methane Emissions from Soil in a Restored Swiss Wetland

PubMed Central

Bhullar, Gurbir S.; Edwards, Peter J.; Olde Venterink, Harry

2014-01-01

Plants are a major factor influencing methane emissions from wetlands, along with environmental parameters such as water table, temperature, pH, nutrients and soil carbon substrate. We conducted a field experiment to study how different plant species influence methane emissions from a wetland in Switzerland. The top 0.5 m of soil at this site had been removed five years earlier, leaving a substrate with very low methanogenic activity. We found a sixfold difference among plant species in their effect on methane emission rates: Molinia caerulea and Lysimachia vulgaris caused low emission rates, whereas Senecio paludosus, Carex flava, Juncus effusus and Typha latifolia caused relatively high rates. Centaurea jacea, Iris sibirica, and Carex davalliana caused intermediate rates. However, we found no effect of either plant biomass or plant functional groups – based on life form or productivity of the habitat – upon methane emission. Emissions were much lower than those usually reported in temperate wetlands, which we attribute to reduced concentrations of labile carbon following topsoil removal. Thus, unlike most wetland sites, methane production in this site was probably fuelled chiefly by root exudation from living plants and from root decay. We conclude that in most wetlands, where concentrations of labile carbon are much higher, these sources account for only a small proportion of the methane emitted. Our study confirms that plant species composition does influence methane emission from wetlands, and should be considered when developing measures to mitigate the greenhouse gas emissions. PMID:24586894

40 CFR 60.702 - Standards.

Code of Federal Regulations, 2010 CFR

2010-07-01

... first. Each owner or operator shall either: (a) Reduce emissions of TOC (less methane and ethane) by 98 weight-percent, or to a TOC (less methane and ethane) concentration of 20 ppmv, on a dry basis corrected...

40 CFR 60.662 - Standards.

Code of Federal Regulations, 2010 CFR

2010-07-01

..., whichever date comes first. Each owner or operator shall either: (a) Reduce emissions of TOC (less methane and ethane) by 98 weight-percent, or to a TOC (less methane and ethane) concentration of 20 ppmv, on a...

Perspectives On The Global Budget of Methane

NASA Astrophysics Data System (ADS)

Khalil, M. K.; Butenhoff, C. L.; Shearer, M. J.

2008-12-01

Early budgets of methane focused on the emissions from individual sources but the estimates had large uncertainties. These uncertainties have been reduced considerably in recent years, but we need an understanding of the trends in the sources as well as their spatial distributions if we are to use methane to control global warming. A nearly 30 year long time series of global atmospheric methane concentrations has accumulated that can provide some of the answers. One of the most dramatic findings is that the increase of methane has nearly stopped in the last decade. But the record also shows that the trend was falling ever since systematic measurements were taken, and perhaps even before that. This finding has led to some puzzles. There is a belief that the anthropogenic sources of methane are increasing but to explain the falling trend we need decreasing sources (or increasing sinks). In fact, the atmospheric measurements show only that the most probable explanation for the decreasing trend and the present near constancy of concentrations is that the global source of methane has been more or less constant over the last 30 years with many short-term ups and downs. Moreover, there is good evidence that some of the major man-made sources of methane, such as cattle, biomass burning and possibly others, have stopped increasing some time back and other sources such as rice agriculture may have decreased over the last 30 years. This allows some smaller energy based sources to have increased, consistent with expectations, and balance out the decreasing sources to keep the total more or less constant. A credible quantitative case can be made for a stable global source based on available information on the trends of the various sources and sinks of methane, but uncertainties remain. We will argue that the stability of sources and sinks is the most likely explanation of the methane concentration trends. We will use this result to re-evaluate the future of man- made methane and its role in global warming. The current IPCC scenarios project a wide range of possible anthropogenic emissions by the year 2100 from 240 Tg/y, which is 25% less than present emissions to 1070 Tg/y which is more than 3 times present emissions. The stabilization or reduction in major man-made sources at this time greatly limits the possibility of major increases in these sources in the future. We will discuss the expected trends of sources to reduce the uncertainty in projected concentrations. These results will in turn contribute to a more realistic use of methane in controlling global warming under current and pending policies or treaties to control greenhouse gas emissions. This research was supported by the Office of Science (BER), U.S. DOE grant # DE-FG02-08ER64515 and DE-FG02-04ER63913.

Hydrogen sulfide formation control and microbial competition in batch anaerobic digestion of slaughterhouse wastewater sludge: Effect of initial sludge pH.

PubMed

Yan, Li; Ye, Jie; Zhang, Panyue; Xu, Dong; Wu, Yan; Liu, Jianbo; Zhang, Haibo; Fang, Wei; Wang, Bei; Zeng, Guangming

2018-07-01

High sulfur content in excess sludge impacts the production of biomethane during anaerobic digestion, meanwhile leads to hydrogen sulfide (H 2 S) formation in biogas. Effect of initial sludge pH on H 2 S formation during batch mesophilic anaerobic digestion of slaughterhouse wastewater sludge was studied in this paper. The results demonstrated that when the initial sludge pH increased from 6.5 to 8.0, the biogas production increased by 10.1%, the methane production increased by 64.1%, while the H 2 S content in biogas decreased by 44.7%. The higher initial sludge pH inhibited the competition of sulfate-reducing bacteria with methane-producing bacteria, and thus benefitted the growth of methanogens. Positive correlation was found between the relative abundance of Desulfomicrobium and H 2 S production, as well as the relative abundance of Methanosarcina and methane production. More sulfates and organic sulfur were transferred to solid and liquid rather than H 2 S formation at a high initial pH. Copyright © 2018 Elsevier Ltd. All rights reserved.

Methane Emissions from Small Lakes: Dynamics and Distribution Patterns

NASA Astrophysics Data System (ADS)

Encinas Fernández, J. M.; Peeters, F.; Hofmann, H.

2014-12-01

The dynamics of dissolved methane were measured during three years in five small lakes with different surface areas and maximum water depth. We analyze and compare the horizontal and vertical distribution of dissolved methane within these lakes during different time periods: the stratified period in summer, the autumn overturn, the winter mixing period, and the period from spring to summer stratification. The horizontal distributions of dissolved methane within the lakes suggest that the relation between surface area and maximum water-depth is a key factor determining the heterogeneity of methane concentrations in the surface water. During most of the year littoral zones are the main source of the methane that is emitted to the atmosphere except for the overturn periods. The vertical distributions of temperature and dissolved oxygen within the different seasons affect the vertical distribution of dissolved methane and thus the methane budget within lakes. Anoxic conditions in the hypolimnion and the intense mixing during overturn periods are key factors for the overall annual methane emissions from lakes.

Martian Atmospheric Methane Plumes from Meteor Shower Infall: A Hypothesis

NASA Technical Reports Server (NTRS)

Fries, M.; Christou, A.; Archer, D.; Conrad, P.; Cooke, W.; Eigenbrode, J.; ten Kate, I. L.; Matney, M.; Niles, P.; Sykes, M.

2016-01-01

Methane plumes in the martian atmosphere have been detected using Earth-based spectroscopy, the Planetary Fourier Spectrometer on the ESA Mars Express mission, and the NASA Mars Science Laboratory. The methane's origin remains a mystery, with proposed sources including volcanism, exogenous sources like impacts and interplanetary dust, aqueous alteration of olivine in the presence of carbonaceous material, release from ancient deposits of methane clathrates, and/or biological activity. To date, none of these phenomena have been found to reliably correlate with the detection of methane plumes. An additional source exists, however: meteor showers could generate martian methane via UV pyrolysis of carbon-rich infall material. We find a correlation between the dates of Mars/cometary orbit encounters and detections of methane on Mars. We hypothesize that cometary debris falls onto Mars during these interactions, depositing freshly disaggregated meteor shower material in a regional concentration. The material generates methane via UV photolysis, resulting in a localized "plume" of short-lived methane.

Development and testing of an electrochemical methane sensor

DOE PAGES

Sekhar, Praveen K.; Kysar, Jesse; Brosha, Eric Lanich; ...

2016-01-12

In this article, the development of an electrochemical methane sensor is presented. The mixed potential based sensor is based on tin doped indium oxide (ITO) and platinum electrodes and yttria-stabilized zirconia (YSZ) electrolyte. The sensor was fabricated using the inexpensive tape-cast method. The sensor responded to methane with a response time of 15 s. The staircase response to methane indicated a 44 mV sensor response to 100 ppm of methane. The sensor response indicated a log-linear relationship with the methane concentration. Upon 500 h of sensor testing, a 5% reduction in methane sensitivity was observed. The cross-sensitivity study on themore » sensor indicated minimal interference to NO, NO 2, and CO 2. To improve the sensitivity to methane, a signal conditioning method referred to as the pulsed discharge technique (PDT) was applied. Finally, a fourfold increase in methane sensitivity was observed when the sensor was subjected to PDT. Future studies include the miniaturization of the sensor with integrated heater design.« less

Development and testing of an electrochemical methane sensor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sekhar, Praveen K.; Kysar, Jesse; Brosha, Eric Lanich

In this article, the development of an electrochemical methane sensor is presented. The mixed potential based sensor is based on tin doped indium oxide (ITO) and platinum electrodes and yttria-stabilized zirconia (YSZ) electrolyte. The sensor was fabricated using the inexpensive tape-cast method. The sensor responded to methane with a response time of 15 s. The staircase response to methane indicated a 44 mV sensor response to 100 ppm of methane. The sensor response indicated a log-linear relationship with the methane concentration. Upon 500 h of sensor testing, a 5% reduction in methane sensitivity was observed. The cross-sensitivity study on themore » sensor indicated minimal interference to NO, NO 2, and CO 2. To improve the sensitivity to methane, a signal conditioning method referred to as the pulsed discharge technique (PDT) was applied. Finally, a fourfold increase in methane sensitivity was observed when the sensor was subjected to PDT. Future studies include the miniaturization of the sensor with integrated heater design.« less

Exposure to polystyrene nanoplastic leads to inhibition of anaerobic digestion system.

PubMed

Fu, Shan-Fei; Ding, Jian-Nan; Zhang, Yun; Li, Yi-Fei; Zhu, Rong; Yuan, Xian-Zheng; Zou, Hua

2018-06-01

In this study, impacts of nanoplastic on the pure and mixed anaerobic digestion systems were investigated. Results showed the growth and metabolism of Acetobacteroides hydrogenigenes were partly inhibited by nanoplastic existed in the pure anaerobic digestion system. The anaerobic digestion of sewage sludge was also obviously inhibited by nanoplastic existed in the mixed anaerobic digestion system. Both the methane yield and methane production rate of the mixed anaerobic digestion system showed negative correlation with the nanoplastic concentration. Compared with anaerobic digestion system without nanoplastic, methane yield and maximum daily methane yield at the nanoplastic concentration of 0.2g/L decreased for 14.4% and 40.7%, respectively. In addition, the start-up of mixed anaerobic digestion system was prolonged by addition of nanoplastic. Microbial community structure analysis indicated the microbial community structures were also affected by nanoplastic existed in the system. At the nanoplastic concentration of 0.2g/L, the relative abundances of family Cloacamonaceae, Porphyromonadaceae, Anaerolinaceae and Gracilibacteraceae decreased partly. Conversely, the relative abundances of family Anaerolinaceae, Clostridiaceae, Geobacteraceae, Dethiosulfovibrionaceae and Desulfobulbaceae improved partly. Copyright © 2017 Elsevier B.V. All rights reserved.

Methane concentrations in water wells unrelated to proximity to existing oil and gas wells in northeastern Pennsylvania.

PubMed

Siegel, Donald I; Azzolina, Nicholas A; Smith, Bert J; Perry, A Elizabeth; Bothun, Rikka L

2015-04-07

Recent studies in northeastern Pennsylvania report higher concentrations of dissolved methane in domestic water wells associated with proximity to nearby gas-producing wells [ Osborn et al. Proc. Natl. Acad. Sci. U. S. A. 2011 , 108 , 8172 ] and [ Jackson et al. Proc. Natl. Acad. Sci. U. S. A. , 2013 , 110 , 11250 ]. We test this possible association by using Chesapeake Energy's baseline data set of over 11,300 dissolved methane analyses from domestic water wells, densely arrayed in Bradford and nearby counties (Pennsylvania), and near 661 pre-existing oil and gas wells. The majority of these, 92%, were unconventional wells, drilled with horizontal legs and hydraulically fractured. Our data set is hundreds of times larger than data sets used in prior studies. In contrast to prior findings, we found no statistically significant relationship between dissolved methane concentrations in groundwater from domestic water wells and proximity to pre-existing oil or gas wells. Previous analyses used small sample sets compared to the population of domestic wells available, which may explain the difference in prior findings compared to ours.

An empirical equation with tables of smoothed solubilities of methane in water and aqueous sodium chloride solutions up to 25 weight percent, 360 degrees C, and 138 MPa

USGS Publications Warehouse

Haas, John L.

1978-01-01

The total pressure for the system H2O-CH 4 is given by p(total) = P(H2O,t) + exp10[log x(CH 4) - a - b x(CH4)], where P(H2O,t) is the vapor pressure of H2O liquid at the temperature t (?C) and x(CH 4) is the molal concentration of methane in the solution. The terms a and b are functions of temperature only. Where the total pressure and temperature are known, the concentration of methane, x(CH4), is found by iteration. The concentration of methane in a sodium chloride brine, y(CH4), is estimated using the function log y(CH4) = log x(CH4) - A I, where A is the salting out constant and I is the ionic strength. For sodium chloride solutions, the ionic strength is equal to the molality of the salt. The equations are valid to 360?C, 138 MPa, and 25 weight percent sodium chloride.

Effect of initial pH on anaerobic co-digestion of kitchen waste and cow manure.

PubMed

Zhai, Ningning; Zhang, Tong; Yin, Dongxue; Yang, Gaihe; Wang, Xiaojiao; Ren, Guangxin; Feng, Yongzhong

2015-04-01

This study investigated the effects of different initial pH (6.0, 6.5, 7.0, 7.5 and 8.0) and uncontrolled initial pH (CK) on the lab-scale anaerobic co-digestion of kitchen waste (KW) with cow manure (CM). The variations of pH, alkalinity, volatile fatty acids (VFAs) and total ammonia nitrogen (NH4(+)-N) were analyzed. The modified Gompertz equation was used for selecting the optimal initial pH through comprehensive evaluation of methane production potential, degradation of volatile solids (VS), and lag-phase time. The results showed that CK and the fermentation with initial pH of 6.0 failed. The pH values of the rest treatments reached 7.7-7.9 with significantly increased methane production. The predicted lag-phase times of treatments with initial pH of 6.5 and 7.5 were 21 and 22 days, which were 10 days shorter than the treatments with initial pH of 7.0 and 8.0, respectively. The maximum methane production potential (8579 mL) and VS degradation rate (179.8 mL/g VS) were obtained when the initial pH was 7.5, which is recommended for co-digestion of KW and CM. Copyright © 2015 Elsevier Ltd. All rights reserved.

Raman studies of methane-ethane hydrate metastability.

PubMed

Ohno, Hiroshi; Strobel, Timothy A; Dec, Steven F; Sloan, E Dendy; Koh, Carolyn A

2009-03-05

The interconversion of methane-ethane hydrate from metastable to stable structures was studied using Raman spectroscopy. sI and sII hydrates were synthesized from methane-ethane gas mixtures of 65% or 93% methane in ethane and water, both with and without the kinetic hydrate inhibitor, poly(N-vinylcaprolactam). The observed faster structural conversion rate in the higher methane concentration atmosphere can be explained in terms of the differences in driving force (difference in chemical potential of water in sI and sII hydrates) and kinetics (mass transfer of gas and water rearrangement). The kinetic hydrate inhibitor increased the conversion rate at 65% methane in ethane (sI is thermodynamically stable) but retards the rate at 93% methane in ethane (sII is thermodynamically stable), implying there is a complex interaction between the polymer, water, and hydrate guests at crystal surfaces.

Importance of methane-oxidizing bacteria in the methane budget as revealed by the use of a specific inhibitor

USGS Publications Warehouse

Oremland, R.S.; Culbertson, C.W.

1992-01-01

METHANE is a greenhouse gas whose concentration in the atmosphere is increasing1-3 Much of this methane is derived from the metabolism of methane-generating (methanogenic) bacteria4,5, and over the past two decades much has been learned about the ecology of methanogens; specific inhibitors of methanogenesis, such as 2-bromoethanesulphonic acid, have proved useful in this regard6. In contrast, although much is known about the biochemistry of methane-oxidizing (methanotrophic) bacteria7, ecological investigations have been hampered by the lack of an analogous specific inhibitor6. Methanotrophs limit the flux of methane to the atmosphere from sediments8,9 and consume atmospheric methane10, but the quantitative importance of methanotrophy in the global methane budget is not well known5. Methylfluoride (CH3F) is known to inhibit oxygen consumption by Methylococcus capsulatus11, and to inhibit the oxidation of 14CH4 to 14CO2 by endosymbionts in mussel gill tissues12. Here we report that methylfluoride (MF) inhibits the oxidation of methane by methane monooxygenase, and by using methylfluoride in field investigations, we find that methanotrophic bacteria can consume more than 90% of the methane potentially available.

Assessing sulfate reduction and methane cycling in a high salinity pore water system in the northern Gulf of Mexico

USGS Publications Warehouse

Pohlman, J.W.; Ruppel, C.; Hutchinson, D.R.; Downer, R.; Coffin, R.B.

2008-01-01

Pore waters extracted from 18 piston cores obtained on and near a salt-cored bathymetric high in Keathley Canyon lease block 151 in the northern Gulf of Mexico contain elevated concentrations of chloride (up to 838 mM) and have pore water chemical concentration profiles that exhibit extensive departures (concavity) from steady-state (linear) diffusive equilibrium with depth. Minimum ??13C dissolved inorganic carbon (DIC) values of -55.9??? to -64.8??? at the sulfate-methane transition (SMT) strongly suggest active anaerobic oxidation of methane (AOM) throughout the study region. However, the nonlinear pore water chemistry-depth profiles make it impossible to determine the vertical extent of active AOM or the potential role of alternate sulfate reduction pathways. Here we utilize the conservative (non-reactive) nature of dissolved chloride to differentiate the effects of biogeochemical activity (e.g., AOM and/or organoclastic sulfate reduction) relative to physical mixing in high salinity Keathley Canyon sediments. In most cases, the DIC and sulfate concentrations in pore waters are consistent with a conservative mixing model that uses chloride concentrations at the seafloor and the SMT as endmembers. Conservative mixing of pore water constituents implies that an undetermined physical process is primarily responsible for the nonlinearity of the pore water-depth profiles. In limited cases where the sulfate and DIC concentrations deviated from conservative mixing between the seafloor and SMT, the ??13C-DIC mixing diagrams suggest that the excess DIC is produced from a 13C-depleted source that could only be accounted for by microbial methane, the dominant form of methane identified during this study. We conclude that AOM is the most prevalent sink for sulfate and that it occurs primarily at the SMT at this Keathley Canyon site.

Biogeochemical cycles at the sulfate-methane transition zone (SMTZ) and geochemical characteristics of the pore fluids offshore southwestern Taiwan

NASA Astrophysics Data System (ADS)

Hu, Ching-Yi; Frank Yang, Tsanyao; Burr, George S.; Chuang, Pei-Chuan; Chen, Hsuan-Wen; Walia, Monika; Chen, Nai-Chen; Huang, Yu-Chun; Lin, Saulwood; Wang, Yunshuen; Chung, San-Hsiung; Huang, Chin-Da; Chen, Cheng-Hong

2017-11-01

In this study, we used pore water dissolved inorganic carbon (DIC), SO42-, Ca2+ and Mg2+ gradients at the sulfate-methane transition zone (SMTZ) to estimate biogeochemical fluxes for cored sediments collected offshore SW Taiwan. Net DIC flux changes (ΔDIC-Prod) were applied to determine the proportion of sulfate consumption by organic matter oxidation (heterotrophic sulfate reduction) and anaerobic oxidation of methane (AOM), and to determine reliable CH4 fluxes at the SMTZ. Our results show that SO42- profiles are mainly controlled by AOM rather than heterotrophic sulfate reduction. Refinement of CH4 flux estimates enhance our understanding of methane abundance from deep carbon reservoirs to the SMTZ. Concentrations of chloride (Cl-), bromide (Br-) and iodide (I-) dissolved in pore water were used to identify potential sources that control fluid compositions and the behavior of dissolved ions. Constant Cl- concentrations throughout ∼30 m sediment suggest no influence of gas hydrates for the compositions within the core. Bromide (Br-) and Iodine (I-) concentrations increase with sediment depth. The I-/Br- ratio appears to reflect organic matter degradation. SO42- concentrations decrease with sediment depth at a constant rate, and sediment depth profiles of Br- and I- concentrations suggests diffusion as the main transport mechanism. Therefore diffusive flux calculations are reasonable. Coring sites with high CH4 fluxes are more common in the accretionary wedge, amongst thrust faults and fractures, than in the passive continental margin offshore southwestern Taiwan. AOM reactions are a major sink for CH4 passing upward through the SMTZ and prevent high methane fluxes in the water column and to the atmosphere.

Methane and other hydrocarbon gases in sediment from the southeastern North American continental margin

USGS Publications Warehouse

Kvenvolden, K.A.; Lorenson, T.D.

2000-01-01

Residual concentrations and distributions of hydrocarbon gases from methane to n-heptane were measured in sediments at seven sites on Ocean Drilling Program (ODP) Leg 164. Three sites were drilled at the Cape Fear Diapir of the Carolina Rise, and one site was drilled on the Blake Ridge Diapir. Methane concentrations at these sites result from microbial generation which is influenced by the amount of pore-water sulfate and possible methane oxidation. Methane hydrate was found at the Blake Ridge Diapir site. The other hydrocarbon gases at these sites are likely the produce of early microbial processes. Three sites were drilled on a transect of holes across the crest of the Blake Ridge. The base of the zone of gas-hydrate occurrence was penetrated at all three sites. Trends in hydrocarbon gas distributions suggest that methane is microbial in origin and that the hydrocarbon gas mixture is affected by diagenesis, outgassing, and, near the surface, by microbial oxidation. Methane hydrate was recovered at two of these three sites, although gas hydrate is likely present at all three sites. The method used here for determining amounts of residual hydrocarbon gases has its limitations and provides poor assessment of gas distributions, particularly in the stratigraphic interval below about ~ 100 mbsf. One advantage of the method, however, is that it yields sufficient quantities of gas for other studies such as isotopic determinations.

Climatic Changes on Tibetan Plateau Based on Ice Core Records

NASA Astrophysics Data System (ADS)

Yao, T.

2008-12-01

Climatic changes have been reconstructed for the Tibetan Plateau based on ice core records. The Guliya ice core on the Tibetan Plateau presents climatic changes in the past 100,000 years, thus is comparative with that from Vostok ice core in Antarctica and GISP2 record in Arctic. These three records share an important common feature, i.e., our climate is not stable. It is also evident that the major patterns of climatic changes are similar on the earth. Why does climatic change over the earth follow a same pattern? It might be attributed to solar radiation. We found that the cold periods correspond to low insolation periods, and warm periods to high insolation periods. We found abrupt climatic change in the ice core climatic records, which presented dramatic temperature variation of as much as 10 °C in 50 or 60 years. Our major challenge in the study of both climate and environment is that greenhouse gases such as CO2, CH4 are possibly amplifying global warming, though at what degree remains unclear. One of the ways to understand the role of greenhouse gases is to reconstruct the past greenhouse gases recorded in ice. In 1997, we drilled an ice core from 7100 m a.s.l. in the Himalayas to reconstruct methane record. Based on the record, we found seasonal cycles in methane variation. In particular, the methane concentration is high in summer, suggestiing active methane emission from wet land in summer. Based on the seasonal cycle, we can reconstruct the methane fluctuation history in the past 500 years. The most prominent feature of the methane record in the Himalayan ice core is the abrupt increase since 1850 A.D.. This is closely related to the industrial revolution worldwide. We can also observe sudden decrease in methane concentration during the World War I and World War II. It implies that the industrial revolution has dominated the atmospheric greenhouse gas emission for about 100 years. Besides, the average methane concentration in the Himalayan ice core is higher than that in polar regions, indicating that the low latitude wet land is a major natural source of atmospheric methane.

Overcoming sodium toxicity by utilizing grass leaves as co-substrate during the start-up of batch thermophilic anaerobic digestion.

PubMed

Suwannoppadol, Suwat; Ho, Goen; Cord-Ruwisch, Ralf

2012-12-01

Sodium toxicity is a common problem causing inhibition of anaerobic digestion, and digesters treating highly concentrated wastes, such as food and municipal solid waste, and concentrated animal manure, are likely to suffer from partial or complete inhibition of methane-producing consortia, including methanogens. When grass clippings were added at the onset of anaerobic digestion of acetate containing a sodium concentration of 7.8 gNa(+)/L, a total methane production about 8L/L was obtained, whereas no methane was produced in the absence of grass leaves. In an attempt to narrow down which components of grass leaves caused decrease of sodium toxicity, different hypotheses were tested. Results revealed that betaine could be a significant compound in grass leaves causing reduction to sodium inhibition. Copyright © 2012 Elsevier Ltd. All rights reserved.

Biomass Burning and the Production of Greenhouse Gases. Chapter 9

NASA Technical Reports Server (NTRS)

Levine, Joel S.

1994-01-01

Biomass burning is a source of greenhouse gases, carbon dioxide, methane, and nitrous oxide. In addition, biomass burning is a source of chemically active gases, including carbon monoxide, nonmethane hydrocarbons, and nitric oxide. These gases, along with methane, lead to the chemical production of tropospheric ozone (another greenhouse gas) as well as control the concentration of the hydroxyl radical, which regulates the lifetime of almost every atmospheric gas. Following biomass burning, biogenic emissions of nitrous oxide, nitric oxide, and methane are significantly enhanced. It is hypothesized that enhanced postburn biogenic emissions of these gases are related to fire-induced changes in soil chemistry and/or microbial ecology. Biomass burning, once believed to be a tropical phenomenon, has been demonstrated by satellite imagery to also be a regular feature of the world's boreal forests. One example of biomass burning is the extensive 1987 fire that destroyed more than 12 million acres of boreal forest in the People's Republic of China and across its border in the Soviet Union. Recent estimates indicate that almost all biomass burning is human-initiated and that it is increasing with time. With the formation of greenhouse and chemically active gases as direct combustion products and a longer-term enhancement of biogenic emissions of gases, biomass burning may be a significant driver for global change.

77 FR 42005 - Petitions for Modification of Application of Existing Mandatory Safety Standards

Federal Register 2010, 2011, 2012, 2013, 2014

2012-07-17

... will continuously monitor for methane immediately before and during the use of nonpermissible surveying... methane is detected in concentrations at or above one percent for the area being surveyed. [[Page 42006

76 FR 16641 - Petitions for Modification of Existing Mandatory Safety Standards

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-24

... past the evaluation points to determine the methane, oxygen, and carbon monoxide concentrations using a...; (e) if an increase of 0.5 percent methane above the previous reading or a 10 percent unplanned change...

40 CFR 61.245 - Test methods and procedures.

Code of Federal Regulations, 2010 CFR

2010-07-01

... methane or n-hexane and air at a concentration of approximately, but less than, 10,000 ppm methane or n-hexane. (5) The instrument probe shall be traversed around all potential leak interfaces as close to the...

40 CFR 61.245 - Test methods and procedures.

Code of Federal Regulations, 2011 CFR

2011-07-01

... methane or n-hexane and air at a concentration of approximately, but less than, 10,000 ppm methane or n-hexane. (5) The instrument probe shall be traversed around all potential leak interfaces as close to the...

40 CFR 264.1063 - Test methods and procedures.

Code of Federal Regulations, 2011 CFR

2011-07-01

... in air). (ii) A mixture of methane or n-hexane and air at a concentration of approximately, but less than, 10,000 ppm methane or n-hexane. (5) The instrument probe shall be traversed around all potential...

40 CFR 61.245 - Test methods and procedures.

Code of Federal Regulations, 2013 CFR

2013-07-01

... methane or n-hexane and air at a concentration of approximately, but less than, 10,000 ppm methane or n-hexane. (5) The instrument probe shall be traversed around all potential leak interfaces as close to the...

40 CFR 264.1063 - Test methods and procedures.

Code of Federal Regulations, 2012 CFR

2012-07-01

... in air). (ii) A mixture of methane or n-hexane and air at a concentration of approximately, but less than, 10,000 ppm methane or n-hexane. (5) The instrument probe shall be traversed around all potential...

40 CFR 265.1063 - Test methods and procedures.

Code of Federal Regulations, 2013 CFR

2013-07-01

... of hydrocarbon in air). (ii) A mixture of methane or n-hexane and air at a concentration of approximately, but less than, 10,000 ppm methane or n-hexane. (5) The instrument probe shall be traversed around...

40 CFR 264.1063 - Test methods and procedures.

Code of Federal Regulations, 2014 CFR

2014-07-01

... in air). (ii) A mixture of methane or n-hexane and air at a concentration of approximately, but less than, 10,000 ppm methane or n-hexane. (5) The instrument probe shall be traversed around all potential...

40 CFR 265.1063 - Test methods and procedures.

Code of Federal Regulations, 2012 CFR

2012-07-01

... of hydrocarbon in air). (ii) A mixture of methane or n-hexane and air at a concentration of approximately, but less than, 10,000 ppm methane or n-hexane. (5) The instrument probe shall be traversed around...

40 CFR 265.1063 - Test methods and procedures.

Code of Federal Regulations, 2014 CFR

2014-07-01

... of hydrocarbon in air). (ii) A mixture of methane or n-hexane and air at a concentration of approximately, but less than, 10,000 ppm methane or n-hexane. (5) The instrument probe shall be traversed around...

40 CFR 265.1063 - Test methods and procedures.

Code of Federal Regulations, 2011 CFR

2011-07-01

... of hydrocarbon in air). (ii) A mixture of methane or n-hexane and air at a concentration of approximately, but less than, 10,000 ppm methane or n-hexane. (5) The instrument probe shall be traversed around...

40 CFR 264.1063 - Test methods and procedures.

Code of Federal Regulations, 2010 CFR

2010-07-01

... in air). (ii) A mixture of methane or n-hexane and air at a concentration of approximately, but less than, 10,000 ppm methane or n-hexane. (5) The instrument probe shall be traversed around all potential...

40 CFR 61.245 - Test methods and procedures.

Code of Federal Regulations, 2012 CFR

2012-07-01

... methane or n-hexane and air at a concentration of approximately, but less than, 10,000 ppm methane or n-hexane. (5) The instrument probe shall be traversed around all potential leak interfaces as close to the...

40 CFR 265.1063 - Test methods and procedures.

Code of Federal Regulations, 2010 CFR

2010-07-01

... of hydrocarbon in air). (ii) A mixture of methane or n-hexane and air at a concentration of approximately, but less than, 10,000 ppm methane or n-hexane. (5) The instrument probe shall be traversed around...