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1

Coupled land-atmosphere modeling of methane emissions with WRF  

NASA Astrophysics Data System (ADS)

This project aims to couple a soil model for methane transport to an atmospheric model to predict methane emissions and dispersion. Methane is a potent greenhouse gas, 20 times as efficient at trapping heat in the atmosphere as the most prevalent greenhouse gas, carbon dioxide. It has been estimated that 60% of methane emissions in the earth's atmosphere come from anthropogenic sources, 17% of which comes from landfills, making landfills the third largest contributor of human-generated methane. Due to high costs and non-ideal weather conditions, field measurements of methane concentration at landfills are difficult and infrequent, so estimates of annual emissions from landfills are not very accurate. We plan to create a coupled land-atmosphere model that takes production and oxidation of methane into account when calculating methane emissions. This model will give a better understanding of how much methane is emitted annually from a given landfill and assist with monitoring efforts. It will also demonstrate the magnitude of diurnal and seasonal variations in methane emissions, which may identify errors in yearly methane emissions estimates made by extrapolating from a small number of field measurements. As a first step, an existing land-surface model, Noah, is modified to compute the transport of oxygen and methane along a 1-D soil column. Surface emissions are calculated using a gradient flux method with a boundary layer conductance that depends on the wind speed. These modifications to the land-surface model will be added to the Weather Research and Forecasting model to predict atmospheric dispersion of methane emitted by landfills. Comparisons to observations are made at two different landfill sites to validate the coupled model.

Taylor, D.

2013-12-01

2

Modeling Modern Methane Emissions From Natural Wetlands. 1; Model Description  

NASA Technical Reports Server (NTRS)

Methane is an important greenhouse gas which contributes about 22% to the present greenhouse effect. Natural wetlands currently constitute the biggest methane source and were the major one in pre-industrial times. Wetland emissions depend highly on the climate, i.e., on soil temperature and water table. In order to investigate the response of methane emissions from natural wetlands to climate variations, a process-based model that derives methane emissions from natural wetlands as a function of soil temperature, water table, and Net Primary Productivity is used. For its application on the global scale, global data sets for all model parameters are generated. In addition, a simple hydrologic model is developed in order to simulate the position of the water table in wetlands. The hydrologic model is tested against data from different wetland sites, and the sensitivity of the hydrologic model to changes in precipitation is examined. The global methane-hydrology model constitutes a tool to study temporal and spatial variations in methane emissions from natural wetlands.

Walter, Bernadette P.; Heimann, Martin; Matthews, Elaine; Hansen, James E. (Technical Monitor)

2001-01-01

3

Modeling methane emissions from boreal peatlands  

NASA Astrophysics Data System (ADS)

Natural wetlands are a significant source of methane (CH4): they have been estimated to account for about 30% of total global CH4 emissions. At the moment, the emission estimates are highly uncertain. These natural emissions respond to climatic variability, so it is necessary to understand their dynamics, in order to be able to predict how they affect the greenhouse-gas balance in the future. We have developed a model of CH4 production and transport in boreal peatlands. The aim is to make it a part of JSBACH, the land component of the Earth System Model of MPI Hamburg. The soil carbon model of JSBACH simulates peatland carbon processes like peat accumulation and decomposition and our CH4 module simulates production of CH4 as a proportion of the anaerobic peat decomposition, transport of CH4 and oxygen between the soil and the atmosphere, and oxidation of CH4 by methanotrophic microbes. The model has the three main pathways for transport: diffusion in aerenchymatous plants and in peat pores (water and air filled) and CH4 ebullition. The oxidation of CH4 depends on the oxygen concentrations in the peat. The model is largely based on existing models of CH4 production and transport but it includes some modifications that we will present here. We also will present the results of the first validations against observational data. The datasets are from two Finnish peatland sites, Siikaneva (southern) and Lompolojänkkä (northern Finland). Measurements of eddy covariance CH4 and CO2 fluxes and meteorological variables, as well as diverse ecological studies have been carried out on both sites over several years.

Raivonen, Maarit; Smolander, Sampo; Mäkelä, Jarmo; Tomasic, Marin; Aalto, Tuula; Markkanen, Tiina; Susiluoto, Jouni; Kleinen, Thomas; Brovkin, Victor; Rinne, Janne; Lohila, Annalea; Aurela, Mika; Vesala, Timo

2014-05-01

4

Methane emissions from rice paddies : experiments and modelling  

Microsoft Academic Search

This thesis describes model development and experimentation on the comprehension and prediction of methane (CH 4<\\/sub> ) emissions from rice paddies. The large spatial and temporal variability in CH 4<\\/sub> emissions and the dynamic non-linear relationships between processes underlying CH 4<\\/sub> emissions impairs the applicability of empirical relations. Mechanistic concepts are therefore starting point of analysis throughout the thesis.The process

Bodegom van P. M

2000-01-01

5

Modeling Modern Methane Emissions From Natural Wetlands, 1.  

National Technical Information Service (NTIS)

Methane is an important greenhouse gas which contributes about 22% to the present greenhouse effect. Natural wetlands currently constitute the biggest methane source and were the major one in pre-industrial times. Wetland emissions depend highly on the cl...

B. P. Walter M. Heimann E. Matthews

2001-01-01

6

A process-based model to derive methane emissions from natural wetlands  

Microsoft Academic Search

A process-based model has been developed in order to calculate methane emissions from natural wetlands as a function of the hydrologic and thermal conditions in the soil. The considered processes in the model are methane production, methane consumption and transport of methane by diffusion, ebullition and through plants. The model has been tested against data from a three-year field study

B. P. Walter; M. Heimann; R. D. Shannon; J. R. White

1996-01-01

7

Validation of a methane emission model using eddy covariance observations and footprint modeling.  

NASA Astrophysics Data System (ADS)

Several methane emission models were developed recently to quantify methane emissions. However, calibration of these models is currently performed using chamber flux methane measurements, which have a number of limitations, such as small footprint area and low temporal resolution. Furthermore, chamber measurements are unsuitable to register ebullition events, which can have a significant influence on observed fluxes. Eddy covariance measurements on the other hand provide high frequency (5 to 20 Hz) data and cover larger areas, while being a non-intrusive way to measure fluxes and account for ebullition. In this study, we present a validation of methane emission model using eddy covariance data, collected in summer periods at the Indigirka lowland site in Eastern Siberia. A flux footprint model was used together with a high resolution vegetation map of the area to retrieve vegetation distribution inside the footprint. Subsequently, this data with eddy covariance data is used to calibrate a methane emission model.

Budishchev, A.; Mi, Y.; Gallagher, A.; van Huissteden, J.; Schaepman-Strub, G.; Dolman, A. J.; Maximov, T. C.

2012-04-01

8

Dairy farm methane emissions using a dispersion model.  

PubMed

There is a need to know whole-farm methane (CH(4)) emissions since confined animal facilities such as beef cattle feedlots and dairy farms are emission "hot spots" in the landscape. However, measurements of whole-farm CH(4) emissions can differ between farms because of differences in contributing sources such as manure handling, number of lactating and nonlactating cows, and diet. Such differences may limit the usefulness of whole-farm emissions for national inventories and mitigation purposes unless the variance between farms is taken into account or a large number of farms can be examined. Our study describes the application of a dispersion model used in conjunction with field measurements of CH(4) concentration and stability of the air to calculate whole-farm emissions of CH(4) from three dairy farms in Alberta, Canada, during three sequential campaigns conducted in November 2004 and May and July 2005. The dairy farms ranged in herd size from 208 to 351 cows (102 to 196 lactating cows) and had different manure handling operations. The results indicate that the average CH(4) emission per cow (mixture of lactating and nonlactating) from the three dairy farms was 336 g d(-1), which was reduced to 271 g d(-1) when the emission (estimated) from the manure storage was removed. Further separation of source strength yielded an average CH(4) (enteric) emission of 363 g d(-1) for a lactating cow. The estimated CH(4) emission intensities were approximately 15 g CH(4) kg(-1) dry matter intake and 16.7 L CH(4) L(-1) of milk produced. The approach of understanding the farm-to-farm differences in CH(4) emissions as affected by diet, animal type, and manure management is essential when utilizing whole-farm emission measurements for mitigation and inventory applications. PMID:22218175

McGinn, S M; Beauchemin, K A

2012-01-01

9

Formation and emission of methane in rice soils: Experimental determination and modeling analysis. Final report  

SciTech Connect

Rice paddy soils have been identified as a major source of methane emissions contributing to the observed atmospheric increase in methane. This points to the need for a method of quantifying and predicting methane emissions for the widely varying conditions used in rice agriculture throughout the world. In the present work, a mathematical model for estimating the emission of methane from rice paddy soils is developed and refined. Kinetic parameters for methanogenesis in a Louisiana rice soil are determined from laboratory data on methane production from acetic acid substrate. Use of a stirred reactor allows simultaneous measurement of acetate consumption and methane production while minimizing mass transfer limitations. An existing model for rice plant growth is utilized to provide data on the availability of root exudates as a carbon source for the methanogens. The final methane model includes the kinetic parameters, plant data, and estimated transport parameters. With adjustments in these parameters, it provides an acceptable match to field data.

Law, V.J.; Bhattacharya, S.K.

1993-08-31

10

Modeling Modern Methane Emissions from Natural Wetlands. 2; Interannual Variations 1982-1993  

NASA Technical Reports Server (NTRS)

A global run of a process-based methane model [Walter et al., this issue] is performed using high-frequency atmospheric forcing fields from ECMWF reanalyses of the period from 1982 to 1993. We calculate global annual methane emissions to be 260 Tg/ yr. 25% of methane emissions originate from wetlands north of 30 deg. N. Only 60% of the produced methane is emitted, while the rest is re-oxidized. A comparison of zonal integrals of simulated global wetland emissions and results obtained by an inverse modeling approach shows good agreement. In a test with data from two wetlands, the seasonality of simulated and observed methane emissions agrees well. The effects of sub-grid scale variations in model parameters and input data are examined. Modeled methane emissions show high regional, seasonal and interannual variability. Seasonal cycles of methane emissions are dominated by temperature in high latitude wetlands, and by changes in the water table in tropical wetlands. Sensitivity tests show that +/- 1 C changes in temperature lead to +/- 20 % changes in methane emissions from wetlands. Uniform changes of +/- 20% in precipitation alter methane emissions by about +/- 18%. Limitations in the model are analyzed. Simulated interannual variations in methane emissions from wetlands are compared to observed atmospheric growth rate anomalies. Our model simulation results suggest that contributions from other sources than wetlands and/or the sinks are more important in the tropics than north-of 30 deg. N. In higher northern latitudes, it seems that a large part, of the observed interannual variations can be explained by variations in wetland emissions. Our results also suggest that reduced wetland emissions played an important role in the observed negative methane growth rate anomaly in 1992.

Walter, Bernadette P.; Heimann, Martin; Mattews, Elaine; Hansen, James E. (Technical Monitor)

2001-01-01

11

Modeling modern methane emissions from natural wetlands 2. Interannual variations 1982-1993  

Microsoft Academic Search

A global run of a process-based methane model [Walter et al., this issue] is performed using high-frequency atmospheric forcing fields from the European Center for Medium-Range Weather Forecasts (ECMWF) reanalyses of the period from 1982 to 1993. Modeled methane emissions show high regional, seasonal, and interannual variability. Seasonal cycles of methane emissions are dominated by temperature in high-latitude wetlands, and

Bernadette P. Walter; Martin Heimann; Elaine Matthews

2001-01-01

12

Modelling global methane emissions from livestock: Biological and nutritional controls  

NASA Technical Reports Server (NTRS)

The available observations of methane production from the literature have been compiled into a ruminant methane data base. This data base includes 400 treatment mean observations of methane losses from cattle and sheep, and minor numbers of measurements from other species. Methane loss varied from 2.0 to 11.6 percent of dietary gross energy. Measurements included describe the many different weights and physiological states of the animals fed and diets ranging from all forage to all concentrate diets or mixtures. An auxiliary spreadsheet lists approximately 1000 individual animal observations. Many important concepts have emerged from our query and analysis of this data set. The majority of the world's cattle, sheep, and goats under normal husbandry circumstances likely produce methane very close to 6 percent of their daily diets gross energy (2 percent of the diet by weight). Although individual animals or losses from specific dietary research circumstances can vary considerably, the average for the vast majority of groups of ruminant livestock are likely to fall between 5.5 to 6.5 percent. We must caution, however, that little experimental data is available for two-thirds of the world's ruminants in developing countries. Available evidence suggests similar percentage of emissions, but this supposition needs confirmation. More importantly, data is skimpy or unavailable to describe diet consumption, animal weight, and class distribution.

Johnson, Donald E.

1992-01-01

13

Estimation of Regional Methane Emission from Rice Fields Using Simple Atmospheric Diffusion Models  

Microsoft Academic Search

Two atmospheric diffusion models, the box model ad the ATDL (Atmospheric Turbulent and Diffusion Laboratory) model, were used to calculate regional methane (CH4) emissions of rice fields in the Beijing area. Compared with conventional closed chamber measurements, the box model overestimated CH4 emission because of meteorological conditions--the ground inverse layer was not favorable for the application of the model during

J. G. Liu; Y. H. Zhang; K. S. Shao; M. Shao; L. M. Zeng; S. H. Lu; S. Slanina; H. A. C. Denier van der Gon

2000-01-01

14

Modeling Modern Methane Emissions from Natural Wetlands, 2, Interannual Variations 1982-1993.  

National Technical Information Service (NTIS)

A global run of a process-based methane model (Walter et al., this issue) is performed using high-frequency atmospheric forcing fields from ECMWF reanalyses of the period from 1982 to 1993. We calculate global annual methane emissions to be 260 Tg/ yr. 25...

B. P. Walter M. Heimann E. Mattews

2001-01-01

15

Methane emissions from vehicles.  

PubMed

Methane (CH4) is an important greenhouse gas emitted by vehicles. We report results of a laboratory study of methane emissions using a standard driving cycle for 30 different cars and trucks (1995-1999 model years) from four different manufacturers. We recommend the use of an average emission factor for the U.S. on-road vehicle fleet of (g of CH/g of CO2) = (15 +/- 4) x 10(-5) and estimate that the global vehicle fleet emits 0.45 +/- 0.12 Tg of CH4 yr(-1) (0.34 +/- 0.09 Tg of C yr(-1)), which represents < 0.2% of anthropogenic CH4 emissions. This estimate includes the effects of vehicle aging, cold start, and hot running emissions. The contribution of CH4 emissions from vehicles to radiative forcing of climate change is 0.3-0.4% of that of CO2 emissions from vehicles. The environmental impact of CH4 emissions from vehicles is negligible and is likely to remain so for the foreseeable future. PMID:15112800

Nam, E K; Jensen, T E; Wallington, T J

2004-04-01

16

Quantifying methane emissions sources in the Arctic using measurements and dispersion modelling  

NASA Astrophysics Data System (ADS)

Methane is a greenhouse gas that is particularly important in the Arctic, as the largest emissions source at high northern latitudes (wetlands) increases with increasing temperature. This amplification of any warming from methane makes it particularly important to understand when considering climate change, however present day sources of methane in the Arctic are poorly quantified. For example, different inventories of wetlands emissions vary considerably in both wetland location and methane source strength. The aim of the MAMM project (Methane and other greenhouse gases in the Arctic - Measurements, process studies and Modelling) is to improve our understanding of the methane, carbon dioxide and nitrous oxide atmospheric concentrations, isotopic composition and emissions in the European Arctic. Field campaigns were held in July 2012, August 2013 and September 2013, in which ground- and aircraft-based measurements were taken of methane, other greenhouse gases and meteorological parameters. A Lagrangian particle dispersion model (NAME, the UK Met Office's Numerical Atmospheric dispersion Modelling Environment) has been used alongside the MAMM field campaign measurements to identify the sources of the methane. The model has been run backwards in time to identify source regions of plumes containing high methane concentrations, for which the carbon isotopes (which will vary dependent on the source) have been analysed. The model has also been run forwards in time to test whether emissions fluxes (from inventories or from simple calculations based on measurements) are consistent with the aircraft observations of methane concentration. Results from a few case studies will be presented, with a focus on quantifying the emissions fluxes by combining the observations with the dispersion model.

Cain, Michelle; Pyle, John; Warwick, Nicola; Manning, Alistair

2014-05-01

17

A process-based, climate-sensitive model to derive methane emissions from natural wetlands: Application to five wetland sites, sensitivity to model parameters, and climate  

Microsoft Academic Search

Methane emissions from natural wetlands constitute the largest methane source at present and depend highly on the climate. In order to investigate the response of methane emissions from natural wetlands to climate variations, a one-dimensional process-based climate-sensitive model to derive methane emissions from natural wetlands is developed. In the model the processes leading to methane emission are simulated within a

Bernadette P. Walter; Martin Heimann

2000-01-01

18

Modeling modern methane emissions from natural wetlands 1. Model description and results  

Microsoft Academic Search

Methane is an important greenhouse gas which contributes about 22% to the present greenhouse effect. Natural wetlands currently constitute the biggest methane source and were the major source in preindustrial times. Wetland emissions depend highly on the climate, i.e., on soil temperature and water table. To investigate the response of methane emissions from natural wetlands to climate variations, a process-based

Bernadette P. Walter; Martin Heimann; Elaine Matthews

2001-01-01

19

Characterization of urban methane emissions in Boston, Massachusetts using an observational network and inverse modeling framework  

NASA Astrophysics Data System (ADS)

There is much uncertainty about the magnitude of methane emissions from natural gas production and delivery infrastructure, yet this quantity is necessary for understanding the climate impact of natural gas as a major fuel source and for partitioning the global methane budget. Preliminary evidence suggests that leaks from urban natural gas distribution systems may release substantial quantities of methane to the atmosphere, but this source has seldom been directly investigated in the scientific literature. As a case study, we seek to describe and quantify the natural gas fraction of the total methane source in the Boston, Massachusetts metropolitan region. We describe the design of an atmospheric methane monitoring network in and around the city. Periodic measurements of atmospheric ethane are used to estimate the fractional contribution of natural gas to the total observed urban methane enhancement. A methane emission inventory is compiled from high-resolution information on biogenic methane sources, street-level methane concentrations, and the natural gas distribution infrastructure. We present preliminary results from the observational network and an inverse modeling framework.

McKain, K.; Wofsy, S. C.; John, B.; Hutyra, L.; Raciti, S.; Briber, B.; Phillips, N. G.; Jackson, R. B.; Down, A.; Schaaf, C.

2012-12-01

20

Modeling methane emissions from the Alaskan Yukon River basin, 1986-2005, by coupling a large-scale hydrological model and a process-based methane model  

NASA Astrophysics Data System (ADS)

Much progress has been made in methane modeling for the Arctic. However, there is still large uncertainty in emissions estimates due to the spatial variability in water table depth resulting from complex topographic gradients, and due to variations in methane production and oxidation due to complex freezing and thawing processes. Here we extended an extant methane emission module within a biogeochemistry model, the Terrestrial Ecosystem Model (TEM), to include a large-scale hydrology model, the variable infiltration capacity (VIC) model. The VIC model provides the required inputs, including freezing and thawing fronts, soil temperature and moisture, to the methane module. The effect of topography on the redistribution of soil moisture and water table depth was explicitly modeled using the TOPMODEL approach. The coupled modeling framework was applied to the Yukon River basin at a spatial resolution of 1 km from 1986 to 2005. The simulations show that the average annual net emissions of CH4 from the region are 4.01 Tg CH4 yr-1. El Niño phenomena usually lead to positive emission anomalies, while decreases in net CH4 emissions may be associated with strong La Niña events. Precipitation was found to be more closely related to CH4 dynamics than to soil temperature and active layer depth during the study period. This study suggests that the effects of soil freezing and thawing processes and the effects of microtopography on hydrology should be considered in the quantification of CH4 emissions.

Lu, Xiaoliang; Zhuang, Qianlai

2012-06-01

21

Model for estimating enteric methane emissions from United States dairy and feedlot cattle.  

PubMed

Methane production from enteric fermentation in cattle is one of the major sources of anthropogenic greenhouse gas emission in the United States and worldwide. National estimates of methane emissions rely on mathematical models such as the one recommended by the Intergovernmental Panel for Climate Change (IPCC). Models used for prediction of methane emissions from cattle range from empirical to mechanistic with varying input requirements. Two empirical and 2 mechanistic models (COWPOLL and MOLLY) were evaluated for their prediction ability using individual cattle measurements. Model selection was based on mean square prediction error (MSPE), concordance correlation coefficient, and residuals vs. predicted values analyses. In dairy cattle, COWPOLL had the lowest root MSPE and greatest accuracy and precision of predicting methane emissions (correlation coefficient estimate = 0.75). The model simulated differences in diet more accurately than the other models, and the residuals vs. predicted value analysis showed no mean bias (P = 0.71). In feedlot cattle, MOLLY had the lowest root MSPE with almost all errors from random sources (correlation coefficient estimate = 0.69). The IPCC model also had good agreement with observed values, and no significant mean (P = 0.74) or linear bias (P = 0.11) was detected when residuals were plotted against predicted values. A fixed methane conversion factor (Ym) might be an easier alternative to diet-dependent variable Ym. Based on the results, the 2 mechanistic models were used to simulate methane emissions from representative US diets and were compared with the IPCC model. The average Ym in dairy cows was 5.63% of GE (range 3.78 to 7.43%) compared with 6.5% +/- 1% recommended by IPCC. In feedlot cattle, the average Ym was 3.88% (range 3.36 to 4.56%) compared with 3% +/- 1% recommended by IPCC. Based on our simulations, using IPCC values can result in an overestimate of about 12.5% and underestimate of emissions by about 9.8% for dairy and feedlot cattle, respectively. In addition to providing improved estimates of emissions based on diets, mechanistic models can be used to assess mitigation options such as changing source of carbohydrate or addition of fat to decrease methane, which is not possible with empirical models. We recommend national inventories use diet-specific Ym values predicted by mechanistic models to estimate methane emissions from cattle. PMID:18539822

Kebreab, E; Johnson, K A; Archibeque, S L; Pape, D; Wirth, T

2008-10-01

22

Methane emission by camelids.  

PubMed

Methane emissions from ruminant livestock have been intensively studied in order to reduce contribution to the greenhouse effect. Ruminants were found to produce more enteric methane than other mammalian herbivores. As camelids share some features of their digestive anatomy and physiology with ruminants, it has been proposed that they produce similar amounts of methane per unit of body mass. This is of special relevance for countrywide greenhouse gas budgets of countries that harbor large populations of camelids like Australia. However, hardly any quantitative methane emission measurements have been performed in camelids. In order to fill this gap, we carried out respiration chamber measurements with three camelid species (Vicugna pacos, Lama glama, Camelus bactrianus; n?=?16 in total), all kept on a diet consisting of food produced from alfalfa only. The camelids produced less methane expressed on the basis of body mass (0.32±0.11 L kg?¹ d?¹) when compared to literature data on domestic ruminants fed on roughage diets (0.58±0.16 L kg?¹ d?¹). However, there was no significant difference between the two suborders when methane emission was expressed on the basis of digestible neutral detergent fiber intake (92.7±33.9 L kg?¹ in camelids vs. 86.2±12.1 L kg?¹ in ruminants). This implies that the pathways of methanogenesis forming part of the microbial digestion of fiber in the foregut are similar between the groups, and that the lower methane emission of camelids can be explained by their generally lower relative food intake. Our results suggest that the methane emission of Australia's feral camels corresponds only to 1 to 2% of the methane amount produced by the countries' domestic ruminants and that calculations of greenhouse gas budgets of countries with large camelid populations based on equations developed for ruminants are generally overestimating the actual levels. PMID:24718604

Dittmann, Marie T; Runge, Ullrich; Lang, Richard A; Moser, Dario; Galeffi, Cordula; Kreuzer, Michael; Clauss, Marcus

2014-01-01

23

Estimating methane gas generation from Devil's swamp landfill using greenhouse gas emission models  

NASA Astrophysics Data System (ADS)

Greenhouse gas (GHG) has been a key issue in the study, design, and management of landfills. Landfill gas (LFG) is considered either as a significant source of renewable energy (if extracted and processed accordingly) or significant source of pollution and risk (if not mitigated or processed). A municipal solid waste (MSW) landfill emits a significant amount of methane, a potent GHG. Thus, quantification and mitigation of GHG emissions is an important area of study in engineering and other sciences related to landfill technology and management. The present study will focus on estimating methane generation from Devils swamp landfill (DSLF), a closed landfill in Baton Rouge, LA. The landfill operated for 53 years (1940-1993) and contains both industrial and municipal waste products. Since the Clean Air Act of 1963, landfills are now classified as New Source Performance Standard (NSPS) waste (i.e., waste that will decompose to generate LFG). Currently, the DSLF is being used as source of renewable energy through the "Waste to Energy" program. For this study, to estimate the methane potential in the DSLF, it is important to determine the characteristics and classification of the landfill's wastes. The study uses and compares different GHG modeling tools---LandGEM, a multiphase model, and a simple first-order model---to estimate methane gas emission and compare results with the actual emissions from the DSLF. The sensitivity of the methane generation rate was analyzed by the methane generation models to assess the effects of variables such as initial conditions, specific growth rate, and reaction rate constants. The study concludes that methane (L0) and initial organic concentration in waste (k) are the most important parameters when estimating methane generation using the models.

Adeyemi, Ayodeji Thompson

24

Estimates of surface methane emissions over Europe using observed surface concentrations and the FLEXPART trajectory model  

NASA Astrophysics Data System (ADS)

We use surface methane observations from nine European ground stations, and the FLEXPART Lagrangian transport model to obtain surface methane emissions for 2010. Our inversion shows the strongest emissions from the Netherlands and the coal mines in Upper Silesia Poland. This is qualitatively consistent with the EDGAR surface flux inventory. We also report significant surface fluxes from wetlands in southern Finland during July and August and reduced wetland fluxes later in the year. Our simulated methane surface concentration captures at least half of the daily variability in the observations, suggesting that the transport model is correctly simulating the regional transport pathways over Europe. We also use our trajectory model to determine whether future space-based remote sensing instruments (MERLIN) will be able to detect both natural and anthropogenic changes in the surface flux strengths.

Weaver, C. J.; Kiemle, C.; Kawa, S. R.; Aalto, T.; Necki, J.; Steinbacher, M.; Arduini, J.; Apadula, F.; Berkhout, H.; Hatakka, J.; O'Doherty, S.

2013-12-01

25

Northern Eurasian Wetlands and the Carbon Cycle: Model Estimates of Carbon Storage and Methane Emissions  

NASA Astrophysics Data System (ADS)

The Eurasian Arctic drainage constitutes over ten percent of the global land area, and stores a substantial fraction of the terrestrial carbon pool in its soils and boreal forests. Specifically, boreal forests in this region constitute an estimated carbon sink of 0.5 Pg/y. However, assessments of carbon storage and fluxes in this region, and their role in climate change, vary considerably due to large uncertainties in the extent of wetlands, which both store carbon as peat and emit carbon as methane. Accurate estimates of wetland extent have been confounded by insufficient resolution of satellite imagery and poor coverage of in situ observations. In this study we refine these estimates of wetland extent, carbon storage, and methane emissions using a system of linked large-scale models of hydrology, terrestrial carbon dynamics, and methane emissions. Large-scale hydrology comes from the Variable Infiltration Capacity (VIC) hydrological model, which includes an updated lake/wetland parameterization that estimates the water table depth as a function of both lake level and wetland soil moisture. Fast ecosystem processes such as photosynthesis and respiration are simulated via the Biosphere Energy-Transfer Hydrology (BETHY) terrestrial carbon model. Methane emissions in areas of open water or saturated soil are simulated with the Walter-Heimann methane model. We validate this modeling system with respect to in situ observations of soil moisture and temperature, evaporation, and fluxes of CO2 and methane at flux towers at Fyodorovskoje, Hakasia, and Cherskii, Russia, over the period 1998- 2004. Sensitivity to calibration parameters such as the rooting depth and the proportionality between methane production rate and NPP are also explored.

Bohn, T. J.; Lettenmaier, D. P.; Sathulur, K.; Bowling, L. C.; McDonald, K. C.

2006-12-01

26

Modeling methane emissions from Alaskan Yukon River Basin from 1986 to 2005 by coupling a large-scale hydrological model and a process-based methane model  

NASA Astrophysics Data System (ADS)

Much progress has been made in methane modeling for the Arctic, there is still a large uncertainty in the emission estimate due to spatial variability of water table depth resulting from complex topographic gradient and variations in methane production and oxidation due to complex freezing and thawing processes. Here we extended an extant emission module within a biogeochemistry model, the Terrestrial Ecosystem Model (TEM) to including a large-scale hydrology model, the variable infiltration capacity (VIC) model. The VIC model provides required inputs including freezing and thawing fronts, soil temperature and moisture, to the methane simulation module. The effect of topography on the soil moisture redistribution is explicitly considered by using the TOPMODEL approach. The methane production, oxidation and transport are calculated in the soil profile at each 1 centimeter depth step and 1-hour time step. The coupled modeling framework is applied to the Yukon River Basin at a spatial resolution of 1km from 1986-2005. The simulations show that the average annual net emissions of CH4 from the region are 4.01 Tg CH4 yr-1. There is a large interannual variability in CH4 emissions during the study period and it is closely related to climate changes. El Nino phenomena usually lead to positive emission anomalies, while decreases in net CH4 emissions may be associated with strong La Niña events. The precipitation was found more closely related to the CH4 dynamics than soil temperature and active layer depth during the 1986-2005. The study highlights the importance of the effects of soil freezing and thawing process and the microtopography information in quantifying the dynamics of CH4 emissions from the complex landscape in the region.

Lu, X.; Zhuang, Q.

2011-12-01

27

Model Estimate of Pan-Arctic Lakes and Wetlands Methane Emissions and Their Future Climate Response  

NASA Astrophysics Data System (ADS)

Lakes and wetlands are important sources of the greenhouse gas CH4, whose emission rate is sensitive to climate. The northern high latitudes, which are especially susceptible to climate change, contain about 50% of the world's lakes and wetlands. Given predicted changes in the climate of this region over the next century (IPCC AR5 scenarios), there is concern about a possible positive feedback resulting from methane emissions from the region's wetlands and lakes. To study the climate response of emissions from northern high latitude lakes and wetlands, we employed a large-scale hydrology and carbon cycling model (Variable Infiltration Capacity model; VIC) over the Pan-Arctic domain, which was linked to an atmospheric model (Japan's National Institute of Environmental Studies transport model; NIES TM). In particular, the VIC model simulates the land surface hydrology and carbon cycling across a dynamic lake-wetland continuum, while NIES TM models the atmospheric mixing and 3-dimension transport of methane emitted. The VIC model includes a distributed wetland water table scheme, which accounts for microtopography around the lakes and simulates variations in inundated area that are calibrated to match a passive microwave based inundation product. Per-unit-area carbon uptake and methane emissions at the land surface have been calibrated using extensive in situ observations at West Siberia. Also, the atmospheric methane concentration from this linked model run was verified for the recent 5 years with satellite observations from Aqua's Atmospheric Infrared Sounder (AIRS) and Envisat's Scanning Imaging Absorption Spectrometer for Atmospheric Cartography (SCIAMACHY) instruments. Using RCP4.5 and RCP8.5 future climate scenarios, we examine CH4 emissions from high latitude lakes and wetlands, as well as their net greenhouse warming potential, over the next 3 centuries across the Pan-Arctic domain. We also assess relative uncertainties in emissions from each of the sources.

Chen, X.; Bohn, T. J.; Maksyutov, S. S.; Lettenmaier, D. P.

2013-12-01

28

[Prediction of methane emission of paddy field based on the support vector regression model].  

PubMed

The methane emission data of paddy fields was obtained by using the static chamber and gas chromatography, and six parameters including atmospheric temperature, soil temperature at 5 cm depth, pH of soil, Eh of soil, soil moisture and ground biomass were selected as the primary influencing factors of methane emission. The support vector regression (epsilon-SVR) model was built on the optimization of structural risk minimization, and the parameters of the epsilon-SVR model were optimized using Leave-one-out Cross Validation (LOOCV). The prediction accuracy of model was evaluated by k-fold cross validation with the mean relative error (MRE) and the root mean square error (RMSE). In addition, the accuracy of the epsilon-SVR model was analyzed by comparison with the Back Propagation-Artificial Neural Network (BP-ANN) model. The results indicated that the predicted value of the epsilon-SVR model with the parameters C and epsilon optimized by LOOCV was in good agreement with the measured value, and the average MRE of test samples was 44% and the average RMSE was 16.21 mg x (m2 x h)(-1) in the process of 11-fold cross validation. Compared with the BP-ANN model, the correlation coefficient was 0.863, and all the indicators were better. It demonstrated that the 8-SVR model could be applied to the prediction of methane emission of paddy fields. PMID:24191538

Chen, Qiang; Jiang, Wei-Guo; Chen, Xi; Yuan, Li-Hua; Wang, Wen-Jie; Pan, Ying-Zi; Wang, Wei; Liu, Xiao-Fu; Liu, Hai-Jiang

2013-08-01

29

What are wetlands and where are they? Part 2: Why are wetland areas and methane emissions so different among wetland-methane models and data sets?  

NASA Astrophysics Data System (ADS)

Natural wetlands are central to understanding current and future interactions between climate and carbon cycling. They are the world's largest source of methane (CH4) to the atmosphere and their distribution and emissions are sensitive to interannual and longer-term variations in climate. Field observations confirm heterogeneous responses of CH4 emissions to climate variations governed by interacting influences of vegetation, climate, and environmental characteristics that differ among wetland ecosystems. Therefore, improving models of wetland-CH4 emission requires characterizing methane-relevant information across the spectrum of wetland variability. Modeling wetland extent and type--inextricably entwined with predicting methane emissions--remains ad hoc such that improvements in both are needed to increase predictive capability especially under future climate. Wetland distributions from data sets, and simulated or prescribed in wetland-methane models, diverge widely in part because no consensus exists on what and where wetlands are, i.e., wetlands are an ill-defined modeling target. Simulated wetland-methane fluxes also vary widely in magnitude, seasonality and geography due in part to wetland definition but also because few of the ~800 published CH4 flux observations have been used to develop and verify the models. Finally, no approach exists to link methane fluxes of wetland ecosystems represented in the literature to the global distribution of those ecosystems. We diagnose underlying causes for differences in wetland areas and distributions in models and data sets, and quantify their impact on modeled methane emissions. We present initial results from a coordinated effort to codify and amplify methane-relevant wetland data and to link the large body of methane fluxes observed in wetland ecosystems to the global distribution of those ecosystems.

Matthews, E.; Bruhwiler, L.

2013-12-01

30

An Ecosystem Simulation Model for Methane Production and Emission from Wetlands  

NASA Technical Reports Server (NTRS)

Previous experimental studies suggest that methane emission from wetland is influenced by multiple interactive pathways of gas production and transport through soil and sediment layers to the atmosphere. The objective of this study is to evaluate a new simulation model of methane production and emission in wetland soils that was developed initially to help identify key processes that regulate methanogenesis and net flux of CH4 to the air, but which is designed ultimately for regional simulation using remotely sensed inputs for land cover characteristics. The foundation for these computer simulations is based on a well-documented model (CASA) of ecosystem production and carbon cycling in the terrestrial blaspheme. Modifications to represent flooded wetland soils and anaerobic decomposition include three new sub-models for: (1) layered soil temperature and water table depth (WTD) as a function of daily climate drivers, (2) CH4 production within the anoxic soil layer as a function of WTD and CO2 production under poorly drained conditions, and (3) CH4 gaseous transport pathways (molecular diffusion, ebullition, and plant vascular transport) as a function of WTD and ecosystem type. The model was applied and tested using climate and ecological data to characterize tundra wetland sites near Fairbanks, Alaska studied previously by Whalen and Reeburgh. Comparison of model predictions to measurements of soil temperature and thaw depth, water-table depth, and CH4 emissions over a two year period suggest that inter-site differences in soil physical conditions and methane fluxes could be reproduced accurately for selected periods. Day-to-day comparison of predicted emissions to measured CH4 flux rates reveals good agreement during the early part of the thaw season, but the model tends to underestimate production of CH4 during the months of July and August in both test years. Important seasonal effects, including that of falling WTD during these periods, are apparently overlooked in the model formulation. Nevertheless, reasonably close agreement was achieved between the model's mean daily and seasonal estimates of CH4 flux and observed emission rates for northern wetland ecosystems. Several features of the model are identified as crucial to more accurate prediction of wetland methane emission, including the capacity to incorporate influences of localized topographic and hydrologic features on site-specific soil temperature and WTD dynamics, and mechanistic simulation of methane emission transport pathways from within the soil profile.

Potter, C. S.; Peterson, David L. (Technical Monitor)

1997-01-01

31

A Simulation Model of Carbon Cycling and Methane Emissions in Amazon Wetlands  

NASA Technical Reports Server (NTRS)

An integrative carbon study is investigating the hypothesis that measured fluxes of methane from wetlands in the Amazon region can be predicted accurately using a combination of process modeling of ecosystem carbon cycles and remote sensing of regional floodplain dynamics. A new simulation model has been build using the NASA- CASA concept for predicting methane production and emission fluxes in Amazon river and floodplain ecosystems. Numerous innovations area being made to model Amazon wetland ecosystems, including: (1) prediction of wetland net primary production (NPP) as the source for plant litter decomposition and accumulation of sediment organic matter in two major vegetation classes - flooded forests (varzea or igapo) and floating macrophytes, (2) representation of controls on carbon processing and methane evasion at the diffusive boundary layer, through the lake water column, and in wetland sediments as a function of changes in floodplain water level, (3) inclusion of surface emissions controls on wetland methane fluxes, including variations in daily surface temperature and of hydrostatic pressure linked to water level fluctuations. A model design overview and early simulation results are presented.

Potter, Christopher; Melack, John; Hess, Laura; Forsberg, Bruce; Novo, Evlyn Moraes; Klooster, Steven

2004-01-01

32

A non-LTE model for the Jovian methane infrared emissions at high spectral resolution  

NASA Technical Reports Server (NTRS)

High resolution spectra of Jupiter in the 3.3 micrometer region have so far failed to reveal either the continuum or the line emissions that can be unambiguously attributed to the nu(sub 3) band of methane (Drossart et al. 1993; Kim et al. 1991). Nu(sub 3) line intensities predicted with the help of two simple non-Local Thermodynamic Equilibrium (LTE) models -- a two-level model and a three-level model, using experimentally determined relaxation coefficients, are shown to be one to three orders of magnitude respectively below the 3-sigma noise level of these observations. Predicted nu(sub 4) emission intensities are consistent with observed values. If the methane mixing ratio below the homopause is assumed as 2 x 10(exp -3), a value of about 300 K is derived as an upper limit to the temperature of the high stratosphere at microbar levels.

Halthore, Rangasayi N.; Allen, J. E., Jr.; Decola, Philip L.

1994-01-01

33

Modelling methane emissions from natural wetlands: TRIPLEX-GHG model integration, sensitivity analysis, and calibration  

NASA Astrophysics Data System (ADS)

This paper introduces TRIPLEX-GHG, a new process-based model framework used to quantify terrestrial ecosystem greenhouse gas dynamics by incorporating both ecological drivers and biogeochemical processes. TRIPLEX-GHG was developed from the Integrated Biosphere Simulator (IBIS), a dynamic global vegetation model, coupled with a new methane (CH4) biogeochemistry module (incorporating CH4 production, oxidation, and transportation processes) and a water table module to investigate CH4 emission processes that occur in natural wetlands. Sensitivity analysis indicates that the most sensitive parameters to use to evaluate CH4 emission processes from wetlands are r (defined as the CH4 to CO2 release ratio) and Q10 in CH4 production process. These two parameters were subsequently calibrated to data obtained from 19 sites collected from approximately 35 studies across different wetlands globally. Having a heterogeneous spatial distribution, r and Q10 parameters ranged from 0.1 to 0.55 with a mean value of 0.25 and from 1.6 to 4.5 with a mean value of 2.48, respectively. The model performed well when simulating magnitude and capturing temporal patterns in CH4 emissions from natural wetlands despite failing to capture CH4 emission pulses in certain cases. Results suggest the model can be applied to different wetlands under varying conditions and is also applicable for global scale simulations.

Zhu, Q.; Liu, J.; Peng, C.; Chen, H.; Fang, X.; Jiang, H.; Yang, G.; Zhu, D.; Wang, W.; Zhou, X.

2013-11-01

34

Global carbon exchange and methane emissions from natural wetlands: Application of a process-based model  

Microsoft Academic Search

Wetlands are one of the most important sources of atmospheric methane (CH4), but the strength of this source is still highly uncertain. To improve estimates of CH4 emission at the regional and global scales and predict future variation requires a process-based model integrating the controls of climatic and edaphic factors and complex biological processes over CH4 flux rates. This study

Mingkui Cao; Stewart Marshall; Keith Gregson

1996-01-01

35

Methane emissions from MBT landfills.  

PubMed

Within the scope of an investigation for the German Federal Environment Agency ("Umweltbundesamt"), the basics for the estimation of the methane emissions from the landfilling of mechanically and biologically treated waste (MBT) were developed. For this purpose, topical research including monitoring results regarding the gas balance at MBT landfills was evaluated. For waste treated to the required German standards, a methane formation potential of approximately 18-24 m(3)CH(4)/t of total dry solids may be expected. Monitoring results from MBT landfills show that a three-phase model with differentiated half-lives describes the degradation kinetics in the best way. This is due to the fact that during the first years of disposal, the anaerobic degradation processes still proceed relatively intensively. In addition in the long term (decades), a residual gas production at a low level is still to be expected. Most of the soils used in recultivation layer systems at German landfills show a relatively high methane oxidation capacity up to 5 l CH(4)/(m(2)h). However, measurements at MBT disposal sites indicate that the majority of the landfill gas (in particular at non-covered areas), leaves the landfill body via preferred gas emission zones (hot spots) without significant methane oxidation. Therefore, rather low methane oxidation factors are recommended for open and temporarily covered MBT landfills. Higher methane oxidation rates can be achieved when the soil/recultivation layer is adequately designed and operated. Based on the elaborated default values, the First Order Decay (FOD) model of the IPCC Guidelines for National Greenhouse Gas Inventories, 2006, was used to estimate the methane emissions from MBT landfills. Due to the calculation made by the authors emissions in the range of 60,000-135,000 t CO(2-eq.)/a for all German MBT landfills can be expected. This wide range shows the uncertainties when the here used procedure and the limited available data are applied. It is therefore necessary to generate more data in the future in order to calculate more precise methane emission rates from MBT landfills. This is important for the overall calculation of the climate gas production in Germany which is required once a year by the German Government. PMID:23756351

Heyer, K-U; Hupe, K; Stegmann, R

2013-09-01

36

Modelling methane emissions from natural wetlands by development and application of the TRIPLEX-GHG model  

NASA Astrophysics Data System (ADS)

A new process-based model TRIPLEX-GHG was developed based on the Integrated Biosphere Simulator (IBIS), coupled with a new methane (CH4) biogeochemistry module (incorporating CH4 production, oxidation, and transportation processes) and a water table module to investigate CH4 emission processes and dynamics that occur in natural wetlands. Sensitivity analysis indicates that the most sensitive parameters to evaluate CH4 emission processes from wetlands are r (defined as the CH4 to CO2 release ratio) and Q10 in the CH4 production process. These two parameters were subsequently calibrated to data obtained from 19 sites collected from approximately 35 studies across different wetlands globally. Being heterogeneously spatially distributed, r ranged from 0.1 to 0.7 with a mean value of 0.23, and the Q10 for CH4 production ranged from 1.6 to 4.5 with a mean value of 2.48. The model performed well when simulating magnitude and capturing temporal patterns in CH4 emissions from natural wetlands. Results suggest that the model is able to be applied to different wetlands under varying conditions and is also applicable for global-scale simulations.

Zhu, Q.; Liu, J.; Peng, C.; Chen, H.; Fang, X.; Jiang, H.; Yang, G.; Zhu, D.; Wang, W.; Zhou, X.

2014-05-01

37

Estimation of atmospheric methane emissions between 1996 and 2001 using a three-dimensional global chemical transport model  

NASA Astrophysics Data System (ADS)

Using an atmospheric inversion approach, we estimate methane surface emissions for different methane regional sources between 1996 and 2001. Data from 13 high-frequency and 79 low-frequency CH4 observing sites have been averaged into monthly mean values with associated errors arising from instrumental precision, mismatch error, and sampling frequency. Simulated methane mole fractions are generated using the 3-D global chemical transport model (MATCH), driven by NCEP analyzed observed meteorology (T62 resolution), which accounts for the impact of synoptic and interannually varying transport on methane observations. We adapted the Kalman filter to optimally estimate methane flux magnitudes and uncertainties from seven seasonally varying (monthly varying flux) and two aseasonal sources (constant flux). We further tested the sensitivity of the inversion to different observing sites, filtered versus unfiltered observations, different model sampling strategies, and alternative emitting regions. Over the 1996-2001 period the inversion reduces energy emissions and increases rice and biomass burning emissions relative to the a priori emissions. The global seasonal emission peak is shifted from August to July because of increased rice and wetland emissions from southeast Asia. The inversion also attributes the large 1998 increase in atmospheric CH4 to global wetland emissions. The current CH4 observational network can significantly constrain northern emitting regions but not tropical emitting regions. Better estimates of global OH fluctuations are also necessary to fully describe interannual methane observations. This is evident in the inability of the optimized emissions to fully reproduce the observations at Samoa.

Chen, Yu-Han; Prinn, Ronald G.

2006-05-01

38

A New Time-Dependent Inventory of Methane Emissions From Global Wetlands Based on Remote Sensing and Biogeochemical Modeling  

NASA Astrophysics Data System (ADS)

The dynamics of natural methane sources contribute to both seasonal and interannual variability in atmospheric methane concentrations. Wetlands are the largest natural source of methane and among the most variable in space and time. We compiled a new map of global wetlands using passive and active remote sensing based land cover information, and used these data to drive the LPJ-TG vegetation model to simulate wetland hydrology, biogeochemical cycling, and methane emissions over the period 1991-2004. Surface flux fields of wetland methane emissions were then coupled to the TM5 transport-chemistry model to simulate methane concentrations at a suite of tropospheric measuring stations. The new wetland map highlights the importance of seasonal wetlands in tropical floodplains and rainforests, while reducing estimates of boreal wetland area compared to previous work, especially in Europe. Our analysis further indicates that the tropics are likely to be a larger source of natural methane emissions than previously thought, and that interannual variability in methane emissions are driven by tropical wetlands, with year-on-year differences of up to 10% in the global wetland source. The seasonal cycle in wetland methane emissions is driven by northern hemisphere high-latitude peatlands, which have an annual amplitude of ca. 5 Tg. Sensitivity studies and comparison with observation networks of atmospheric methane concentrations demonstrate that this new inventory is a significant improvement over previous estimates in reproducing observed seasonal and interannual variability at several in-situ and aircraft-based measuring stations. The inventory will be an important component for evaluation of new remote sensing-based products of atmospheric methane concentrations.

Kaplan, J. O.; Bergamaschi, P.; Dentener, F.

2005-12-01

39

Assessing methane wetland emissions through the use of multiple models and GOSAT satellite observations  

NASA Astrophysics Data System (ADS)

Over a 20-year timescale, methane has a radiative forcing comparable to that of CO2, making it the second most important anthropogenic greenhouse gas. This, along with the influence it has on tropospheric ozone and water vapour, means that it plays a key role in the Earth's atmosphere. However, recent unexpected changes in the methane growth rate have highlighted that there are still gaps in our understanding of the CH4 budget which can arise from the upscaling of the highly accurate, but sparse, surface concentration data to continental scales. This work focuses on addressing the major uncertainties that currently exist in wetland methane emissions by comparing state-of-the-art chemical transport and climate-chemistry models, using a common set of wetland emission inventories, to the University of Leicester GOSAT CH4 dataset. We will present regional comparisons of the different model runs with the GOSAT satellite data with a particular focus on wetland regions such as the Amazon and south-East Asia and assess how well the different model runs agree with observations.

Parker, Robert; Boesch, Hartmut; Fraser, Annemarie; Palmer, Paul; Wilson, Chris; Mcnorton, Joey; Chipperfield, Martyn; Hayman, Garry

2014-05-01

40

Methane Emissions from Deciduous Trees  

Microsoft Academic Search

There is some disagreement today over whether terrestrial plants present a significant source of methane to the atmosphere. Even if the plants are recognized as a source, there is no clear method to extrapolate plant emissions to the global atmospheric budget of methane and estimates vary widely. There is also no consensus on a mechanism for methane production and\\/or plant-mediated

A. L. Rice; D. Teama; M. K. Khalil; M. J. Shearer; T. N. Rosenstiel

2008-01-01

41

A Process-based, Climate-Sensitive Model to Derive Methane Emissions from Natural Wetlands: Application to 5 Wetland Sites, Sensitivity to Model Parameters and Climate  

NASA Technical Reports Server (NTRS)

Methane emissions from natural wetlands constitutes the largest methane source at present and depends highly on the climate. In order to investigate the response of methane emissions from natural wetlands to climate variations, a 1-dimensional process-based climate-sensitive model to derive methane emissions from natural wetlands is developed. In the model the processes leading to methane emission are simulated within a 1-dimensional soil column and the three different transport mechanisms diffusion, plant-mediated transport and ebullition are modeled explicitly. The model forcing consists of daily values of soil temperature, water table and Net Primary Productivity, and at permafrost sites the thaw depth is included. The methane model is tested using observational data obtained at 5 wetland sites located in North America, Europe and Central America, representing a large variety of environmental conditions. It can be shown that in most cases seasonal variations in methane emissions can be explained by the combined effect of changes in soil temperature and the position of the water table. Our results also show that a process-based approach is needed, because there is no simple relationship between these controlling factors and methane emissions that applies to a variety of wetland sites. The sensitivity of the model to the choice of key model parameters is tested and further sensitivity tests are performed to demonstrate how methane emissions from wetlands respond to climate variations.

Walter, Bernadette P.; Heimann, Martin

1999-01-01

42

Dissolved methane in rising main sewer systems: field measurements and simple model development for estimating greenhouse gas emissions.  

PubMed

At present, the potential generation of methane in wastewater collection systems is ignored under international greenhouse gas (GHG) accounting protocols, despite recent reports of substantial dissolved methane formation in sewers. This suggests that the current national GHG inventories for wastewater handling systems are likely to be underestimated for some situations. This study presents a new catalogue of field data on methane formation in rising main sewerage systems and proposes an empirically-fitted, theoretical model to predict dissolved methane concentrations, based upon the independent variables of pipeline geometry (i.e. surface area to volume ratio, A/V) and hydraulic retention time (HRT). Systems with longer HRT and/or larger A/V ratios are shown to have higher dissolved methane concentrations. This simple predictive model provides a means for water authorities to estimate the methane emissions from other pressurised sewerage systems of similar characteristics. PMID:19934518

Foley, Jeff; Yuan, Zhiguo; Lant, Paul

2009-01-01

43

Emission of methane from plants  

PubMed Central

It has been proposed that plants are capable of producing methane by a novel and unidentified biochemical pathway. Emission of methane with an apparently biological origin was recorded from both whole plants and detached leaves. This was the first report of methanogenesis in an aerobic setting, and was estimated to account for 10–45 per cent of the global methane source. Here, we show that plants do not contain a known biochemical pathway to synthesize methane. However, under high UV stress conditions, there may be spontaneous breakdown of plant material, which releases methane. In addition, plants take up and transpire water containing dissolved methane, leading to the observation that methane is released. Together with a new analysis of global methane levels from satellite retrievals, we conclude that plants are not a major source of the global methane production.

Nisbet, R.E.R.; Fisher, R.; Nimmo, R.H.; Bendall, D.S.; Crill, P.M.; Gallego-Sala, A.V.; Hornibrook, E.R.C.; Lopez-Juez, E.; Lowry, D.; Nisbet, P.B.R.; Shuckburgh, E.F.; Sriskantharajah, S.; Howe, C.J.; Nisbet, E.G.

2009-01-01

44

Methane Emissions from Industrial Sources.  

National Technical Information Service (NTIS)

This chapter identifies and describes major industrial sources of methane (CH4) emissions. For each source type examined, CH4 release points are identified and a detailed discussion of the factors affecting emissions is provided. A summary and discussion ...

L. L. Beck S. D. Piccot D. A. Kirchgessner

1993-01-01

45

Future methane emissions from animals  

SciTech Connect

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 of roughly 1% per year averaged through 2025. Increasing levels are found to originate from developed countries even though the feedstock levels are lower.

Anastasi, C.; Simpson, V.J. (Univ. of York, Heslington (United Kingdom))

1993-04-20

46

Evaluation of methane emissions from Palermo municipal landfill: Comparison between field measurements and models  

SciTech Connect

Methane (CH{sub 4}) diffuse emissions from Municipal Solid Waste (MSW) landfills represent one of the most important anthropogenic sources of greenhouse gas. CH{sub 4} is produced by anaerobic biodegradation of organic matter in landfilled MSW and constitutes a major component of landfill gas (LFG). Gas recovery is a suitable method to effectively control CH{sub 4} emissions from landfill sites and the quantification of CH{sub 4} emissions represents a good tool to evaluate the effectiveness of a gas recovery system in reducing LFG emissions. In particular, LFG emissions can indirectly be evaluated from mass balance equations between LFG production, recovery and oxidation in the landfill, as well as by a direct approach based on LFG emission measurements from the landfill surface. However, up to now few direct measurements of landfill CH{sub 4} diffuse emissions have been reported in the technical literature. In the present study, both modeling and direct emission measuring methodologies have been applied to the case study of Bellolampo landfill located in Palermo, Italy. The main aim of the present study was to evaluate CH{sub 4} diffuse emissions, based on direct measurements carried out with the flux accumulation chamber (static, non-stationary) method, as well as to obtain the CH{sub 4} contoured flux map of the landfill. Such emissions were compared with the estimate achieved by means of CH{sub 4} mass balance equations. The results showed that the emissions obtained by applying the flux chamber method are in good agreement with the ones derived by the application of the mass balance equation, and that the evaluated contoured flux maps represent a reliable tool to locate areas with abnormal emissions in order to optimize the gas recovery system efficiency.

Di Bella, Gaetano, E-mail: dibella@idra.unipa.it [Dipartimento di Ingegneria Civile, Ambientale e Aerospaziale, Universita di Palermo, Viale delle Scienze, 90128 Palermo (Italy); Di Trapani, Daniele, E-mail: ditrapani@idra.unipa.it [Dipartimento di Ingegneria Civile, Ambientale e Aerospaziale, Universita di Palermo, Viale delle Scienze, 90128 Palermo (Italy); Viviani, Gaspare, E-mail: gviv@idra.unipa.it [Dipartimento di Ingegneria Civile, Ambientale e Aerospaziale, Universita di Palermo, Viale delle Scienze, 90128 Palermo (Italy)

2011-08-15

47

Prediction of enteric methane emissions from cattle.  

PubMed

Agriculture has a key role in food production worldwide and it is a major component of the gross domestic product of several countries. Livestock production is essential for the generation of high quality protein foods and the delivery of foods in regions where animal products are the main food source. Environmental impacts of livestock production have been examined for decades, but recently emission of methane from enteric fermentation has been targeted as a substantial greenhouse gas source. The quantification of methane emissions from livestock on a global scale relies on prediction models because measurements require specialized equipment and may be expensive. The predictive ability of current methane emission models remains poor. Moreover, the availability of information on livestock production systems has increased substantially over the years enabling the development of more detailed methane prediction models. In this study, we have developed and evaluated prediction models based on a large database of enteric methane emissions from North American dairy and beef cattle. Most probable models of various complexity levels were identified using a Bayesian model selection procedure and were fitted under a hierarchical setting. Energy intake, dietary fiber and lipid proportions, animal body weight and milk fat proportion were identified as key explanatory variables for predicting emissions. Models here developed substantially outperformed models currently used in national greenhouse gas inventories. Additionally, estimates of repeatability of methane emissions were lower than the ones from the literature and multicollinearity diagnostics suggested that prediction models are stable. In this context, we propose various enteric methane prediction models which require different levels of information availability and can be readily implemented in national greenhouse gas inventories of different complexity levels. The utilization of such models may reduce errors associated with prediction of methane and allow a better examination and representation of policies regulating emissions from cattle. PMID:24259373

Moraes, Luis E; Strathe, Anders B; Fadel, James G; Casper, David P; Kebreab, Ermias

2014-07-01

48

Sensitivity and Uncertainty of High-Latitude Terrestrial Methane Emissions in a Changing Climate: Application of a Methane Biogeochemical Model in CLM4  

NASA Astrophysics Data System (ADS)

Current terrestrial methane biogeochemical models rely on a suite of uncertain mechanistic representations and process parameterizations. These uncertainties propagate to large-scale predictions of current and future methane emissions. To improve understanding of these uncertainties and how they may propagate to climate feedback analyses, we applied a recently developed and tested CH4 biogeochemistry submodel integrated in CLM4 (the land-surface model of the Community Earth System Model (CESM)). The model includes process-based representations of CH4 production, oxidation, aerenchyma transport, ebullition, aqueous and gaseous diffusion, and fractional inundation. The seasonality and magnitude of predicted CH4 emissions were compared with observations from 18 sites spanning the tropics to high latitudes. We also compared model predictions to two global atmospheric inversions and a wide range of previous bottom-up CH4 emission estimates. Using the model, we demonstrate that increased aerenchyma area tends to decrease net CH4 emissions when the water table is at the surface, but can increase emissions when the water table is below the surface. Sensitivity and uncertainty analyses across the model parameter space were used to identify the dominant parameters affecting regional and global CH4 emissions. The microbial temperature responses, aerenchyma characteristics, oxidation, and redox parameterizations had large impacts on high-latitude fluxes. Using the full range found in the literature for each of these parameters yields up to a factor of five range in high-latitude methane emissions. We will also characterize these uncertainties under future climate scenarios. Finally, we discuss observations and experiments that would facilitate improvement of the growing number of regional and global CH4 biogeochemical models.

Riley, W. J.; Subin, Z.; Lawrence, D. M.; Swenson, S. C.; Torn, M. S.; Meng, L.; Mahowald, N. M.; Hess, P. G.

2010-12-01

49

Methane Emissions from Cattle  

Microsoft Academic Search

Increasing atmospheric concentra- tions of methane have led scientists to examine its sources of origin. Ruminant livestock can produce 250 to 500 L of methane per day. This level of production results in estimates of the contribution by cattle to global warming that may occur in the next 50 to 100 yr to be a little less than 2%. Many

K. A. Johnson; D. E. Johnson

2010-01-01

50

Integral emission factors for methane determined using urban flux measurements and local-scale inverse models  

NASA Astrophysics Data System (ADS)

The most important long-lived greenhouse gas (LLGHG) emitted during combustion of fuels is carbon dioxide (CO2), however also traces of the LLGHGs methane (CH4) and nitrous oxide (N2O) are released, the quantities of which depend largely on the conditions of the combustion process. Emission factors determine the mass of LLGHGs emitted per energy used (or kilometre driven for cars) and are key inputs for bottom-up emission modelling. Emission factors for CH4 are typically determined in the laboratory or on a test stand for a given combustion system using a small number of samples (vehicles, furnaces), yet associated with larger uncertainties when scaled to entire fleets. We propose an alternative, different approach - Can integrated emission factors be independently determined using direct micrometeorological flux measurements over an urban surface? If so, do emission factors determined from flux measurements (top-down) agree with up-scaled emission factors of relevant combustion systems (heating, vehicles) in the source area of the flux measurement? Direct flux measurements of CH4 were carried out between February and May, 2012 over a relatively densely populated, urban surface in Vancouver, Canada by means of eddy covariance (EC). The EC-system consisted of an ultrasonic anemometer (CSAT-3, Campbell Scientific Inc.) and two open-path infrared gas analyzers (Li7500 and Li7700, Licor Inc.) on a tower at 30m above the surface. The source area of the EC system is characterised by a relative homogeneous morphometry (5.3m average building height), but spatially and temporally varying emission sources, including two major intersecting arterial roads (70.000 cars drive through the 50% source area per day) and seasonal heating in predominantly single-family houses (natural gas). An inverse dispersion model (turbulent source area model), validated against large eddy simulations (LES) of the urban roughness sublayer, allows the determination of the spatial area that contributes to each measurement interval (30 min), which varies with wind direction and stability. A detailed geographic information system of the urban surface combined with traffic counts and building energy models makes it possible to statistically relate fluxes to vehicle density (km driven) and buildings (gas heated volume) - and ultimately quantify the contribution of space heating, transport sector and fugitive emissions to the total emitted CH4 from an urban environment. The measured fluxes of CH4 over the selected urban environment averaged to 22.8 mg CH4 m-2 day-1 during the study period. Compared with the simultaneously measured CO2 emissions, the contribution of CH4, however, accounts for only about 3% of the total LLGHG emissions from this particular urban surface. Traffic contributed 8.8 mg CH4 m-2 day-1, equivalent to 39% of the total CH4 flux. The determined emission factor for the typical fleet composition is 0.062 g CH4 per km driven which is higher than upscaled fleet emission factors (EPA) by a factor of two. This discrepancy can be partially explained through the slower city traffic with frequent idling (traffic congestion), fleet composition and cold starts. Emissions of CH4 by domestic space heating (55% of the total CH4 flux or 12.7 mg CH4 m-2 day-1) are also higher than estimated from upscaled emission factors. There is no evidence of substantial unknown sources such as soil processes, combustion of wood, and leakages from gas distribution pipes (residual: 6% or 1.3 mg CH4 m-2 day-1). The presented study is among the first direct measurements of CH4 emissions over an urban surface and demonstrates that flux measurements of greenhouse gases can be used to determine sources and emission factors in complex urban situations.

Christen, Andreas; Johnson, Mark; Molodovskaya, Marina; Ketler, Rick; Nesic, Zoran; Crawford, Ben; Giometto, Marco; van der Laan, Mike

2013-04-01

51

METHANE EMISSIONS FROM INDUSTRIAL SOURCES  

EPA Science Inventory

The chapter identifies and describes major industrial sources of methane (CH4) emissions. or each source type examined, it identifies CH4 release points and discusses in detail the factors affecting emissions. t also summarizes and discusses available global and country-specific ...

52

Process-based, Climate-Sensitive Model to Derive Methane Emissions from Natural Wetlands: Application to 5 Wetland Sites, Sensitivity to Model Parameters and Climate.  

National Technical Information Service (NTIS)

Methane emissions from natural wetlands constitutes the largest methane source at present and depends highly on the climate. In order to investigate the response of methane emissions from natural wetlands to climate variations, a 1-dimensional process-bas...

B. P. Walter M. Heimann

1999-01-01

53

Modelling the methane emissions from wetlands during the last interglacial period: potential impact on the atmospheric concentrations  

NASA Astrophysics Data System (ADS)

Present-day atmospheric methane concentrations have reached unprecedented levels over the whole 800,000 years recorded in the Antarctic ice core. Due to its high global warming potential, it is crucial to understand its sources and sinks. Whereas the present-day high anomaly is attributable to an increase in anthropogenic emissions, a large natural variability has been observed during the glacial-interglacial cycles, from ~360 ppbv for the cold glacials to ~700 ppbv for the warm interglacials. The origin of this natural variability of methane has been widely debated, suggesting a more plausible source driven variability (i.e. wetlands, representing 20 - 40% of global sources) while the oxidation capacity of the atmosphere (sinks) has remained roughly constant over the ice ages. Nevertheless, most previous studies rely on the use of simplified models of methane surface emissions (non-process based) and/or simplified models of atmospheric chemistry, with simple parametrisation of important processes, such as vegetation dynamics or isoprene chemistry in the atmosphere. We address this issue with state-of-the-art models, both for surface processes and for atmospheric chemistry. Ice core records provide insights of the past state of the atmosphere. From Antarctica's ice core studies, we believe that during the Last Interglacial (LIG), the atmospheric methane concentrations were similar to pre-industrial ones. However, due to strongly different orbital forcings than present-day, the climate at this time is suspected to have been largely different. For example, there is evidence of a +4 to +5°C warming in summer at high northern latitudes compared to pre-industrial (CAPE members, 2006). This could lead to considerable changes in wetland dynamics, however this is not evident in ice core records. The LIG period is used here as a case study for the models, to understand the mechanisms behind the natural variability of the methane atmospheric concentrations. To do so, we recently implemented a sophisticated process-based model of methane emissions (Walter and Heimann, 2000) into a Dynamic Global Vegetation Model (DGVM, Hybrid8). In order to move from surface emissions to atmospheric concentrations, we used a complex atmospheric chemistry model (Met Office UM - UKCA). We report an important sensitivity of the amplitude, seasonality and geographical pattern of the simulated emissions during the LIG. These sensitivities could explain the similar atmospheric methane concentrations between the LIG and the pre-industrial with a drastically different climate.

Quiquet, Aurélien; Friend, Andrew D.; Archibald, Alexander T.; Prentice, I. Colin; Pyle, John A.

2013-04-01

54

Assessment of emissions prediction capability of RANS based PDF models for lean premixed combustion of methane  

SciTech Connect

The high computational cost of Large Eddy Simulation (LES) makes Reynolds Averaged Navier-Stokes (RANS) methods the current standard for turbulent combustion modeling. Empirical models for turbulence, turbulence-combustion interaction and chemical kinetics are, however, a major source of uncertainty in RANS based combustion simulation. While Probability Density Function (PDF) based models overcome some of these issues, most commercial codes do not take full advantage of these models. In this study, lean premixed combustion of methane in a bluff-body combustor is simulated using two different reduced chemical mechanisms (ARM9 and ARM19) combined with the composition PDF transport combustion model in the commercial code FLUENT. Two different turbulence models, namely the RNG k-? model and the Reynolds Stress Model (RSM) are used and the results of the simulations are compared to experimental data. For all the models tested, the prediction of temperature and major species (CH4, O2, CO2, CO, H2, and H2O) was good when compared to experiments. While all of the model predictions for the intermediate species OH showed an order magnitude difference (compared to the experiments) close to the bluff body surface; downstream axial locations showed good quantitative and qualitative agreement with the experiments. In a trend similar to the previous study (Nanduri et al., 2007) using the Eddy Dissipation Concept (EDC) model, predicted values for NO emission radial profiles showed an average difference of ±5 ppm when compared to experimental values. The results were also compared to the results of a velocity-composition joint PDF model developed by researchers at the University of Pittsburgh. In terms of emissions (NO and CO) predictions the relatively expensive composition PDF model in FLUENT did not give significant improvement when compared to the computationally cheaper EDC models. However, the velocity-composition joint PFD model used by researchers at the University of Pittsburgh did show significant improvement over EDC models in the prediction of NO. Both of the PDF models resulted in better qualitative and quantitative agreement in H2 prediction, thus showing the promise of PDF based models in simulating lean premixed combustion of fuel blends like hydrogen enriched natural gas.

Parsons, D.R.; Nanduri, J.R.; Celik, Ismail; Strakey, P.A.

2008-01-01

55

Observational Constraints on Changing Arctic Methane Emissions  

NASA Astrophysics Data System (ADS)

Methane (CH4) is the second-most important greenhouse gas influenced by human activities. Its chemistry results in additional indirect climate effects from production of tropospheric O3, which also affects air quality, and stratospheric H2O. Because methane's atmospheric lifetime is relatively short (~9 yr) and ~70% of its emissions are anthropogenic, reductions in its emissions provide a potential cost-effective opportunity to slow the rate of increase of radiative forcing. Some fraction of decreased anthropogenic emissions may be canceled by potentially strong feed-backs to natural emissions. Because natural emissions of CH4 are diffuse, relatively weak, and highly-variable in space and time, quantifying changes for large spatial regions is difficult from small-scale field studies alone. Atmosphere observations at well-chosen sites integrate these emissions over large zonal regions and can be particularly useful for detecting changes in emissions. Paleo-climate studies indicate that CH4 emissions from Arctic wetlands are sensitive to climate and may provide a strong positive feedback as the Arctic warms. Measurements of atmospheric CH4 from the NOAA Global Monitoring Division's, Global Cooperative Air Sampling Network began in 1983. These high-precision observations offer key constraints on changes in Arctic CH4 emissions. During 2007, the CH4 growth rate increased in the Arctic, but was nearly zero during 2008. Use of the data in a chemical transport model suggest anomalous emissions of about 2 Tg CH4 during 2007, but returning to long-term average emissions after that. Another potential source affected by climate is emissions from methane clathrates. Measurements of methane's isotopic composition in the Arctic have been useful in showing that CH4 enhancements in Arctic air result from wetlands, not clathrates. Both potential sources are also constrained by spatial patterns in observed CH4, which indicate that, so far, changes in emissions of Arctic CH4 over the past 2 decades are less than ~2 Tg CH4 yr-1.

Dlugokencky, E. J.; Bruhwiler, L.; Lang, P. M.; Masarie, K.; Crotwell, A. M.; Crotwell, M.; Lowry, D.; Fisher, R. E.; Nisbet, E. G.

2012-12-01

56

Determining Methane Emissions From the Elgin North Sea Rig Using Ship-track Measurements and High Resolution Mesoscale Models  

NASA Astrophysics Data System (ADS)

On 27 March 2012 the natural gas exploitation rig "Elgin" on the North Sea, operated by Total, started leaking considerable amounts (company estimate 200 000 m3 per day) of methane to the atmosphere. A passenger ferry, daily sailing between IJmuiden (Netherlands) and Newcastle upon Tyne (United Kingdom) on a track just South of the Elgin rig was equipped with a high precision CRDS CH4/CO2 monitor. During April 2012 several cruises were made where the Elgin methane plume could be identified next to methane plumes from other rigs on the North Sea. Also at some land based observatories in NW Europe the Elgin methane plume could be detected. In this paper we deploy two high resolution models, WRF V3 and Flexpart, to derive emission estimates based on the observations. Despite the unique opportunity of trying to detect a single large point source on a relatively homogeneous surface, considerable model uncertainties remain; implications for inverse emission verification on more complex surface (land) areas will be discussed.

Vermeulen, A. T.; Hensen, A.; Bulk, P. V.; Rodink, R.

2012-12-01

57

Improving a plot-scale methane emission model and its performance at a Northeastern Siberian tundra site  

NASA Astrophysics Data System (ADS)

In order to better address the feedbacks between climate and wetland methane (CH4) emissions, we tested several mechanistic improvements to the wetland CH4 emission model Peatland-VU with a longer Arctic dataset than any other model: (1) inclusion of an improved hydrological module; (2) incorporation of a gross primary productivity (GPP) module; (3) a more realistic soil-freezing scheme. A long time series of field measurements (2003-2010) from a tundra site in Northeastern Siberia is used to validate the model, and the Generalized Likelihood Uncertainty Estimation (GLUE) methodology is used to test the sensitivity of model parameters. Peatland-VU is able to capture both the annual magnitude and seasonal variations of the CH4 flux, water table position and soil thermal properties. However, detailed daily variations are difficult to evaluate due to data limitation. Improvements due to the inclusion of a GPP module are less than anticipated, although this component is likely to become more important at larger spatial scales because the module can accommodate the variations in vegetation traits better than at plot-scale. Sensitivity experiments suggest that the methane production rate factor, the methane plant oxidation parameter, the reference temperature for temperature dependent decomposition, and the methane plant transport rate factor are the most important parameters affecting the data fit, regardless of vegetation type. Both wet and dry vegetation cover are sensitive to the minimum water table level, in addition to the runoff threshold and open water correction factor and the subsurface water evaporation and evapotranspiration correction factors, respectively. These results shed light on model parameterization and future improvement of CH4 modelling. However, high spatial variability of CH4 emissions within similar vegetation/soil units and data quality prove to impose severe limits on model testing and improvement.

Mi, Y.; van Huissteden, J.; Parmentier, F. J. W.; Gallagher, A.; Budishchev, A.; Berridge, C. T.; Dolman, A. J.

2013-12-01

58

Estimating Emissions of Ammonia and Methane from an Anaerobic Livestock Lagoon Using Micrometeorological Methods and Inverse Modeling  

NASA Astrophysics Data System (ADS)

Evaluating the impact of increased carbon and nitrogen emissions on local air quality and regional bionetworks due to animal agricultural activity is of great interest to the public, political, economic and ecological welfare of areas within the scope of these practices. Globally, livestock operations account for 64% of annual anthropogenic emissions of ammonia (NH3) [1]. Concerning methane (CH4), anaerobic lagoons from commercial dairy operations contribute the second largest share of CH4 emissions from manure in the United States[1], and additionally are a local source of NH3 as well. Anaerobic lagoons are commonly used in commercial animal agriculture and as significant local sources of greenhouse gases (GHG), there is a strong need to quantify GHG emissions from these systems. In 2012 at a commercial dairy operation in Northern Colorado, USA, measurements of CH4 were made using eddy covariance (EC), while NH3 was estimated using a combination of real-time monitoring (cavity ring-down spectroscopy as well as time-integrated passive samplers). Methane emissions have been measured at this lagoon using EC since 2011, with fluxes ranging from 0.5 mg m-2 s-1 in early summer to >2 mg m-2 s-1 in late summer and early fall. Concentration data of both CH4 and NH3 were used to estimate emissions using a 2-dimensional inverse model based on solving the advection-diffusion equation[2]. In the case of the CH4-EC data, results from the inverse model were compared with the EC-derived flux estimates for enhanced parameterization of surface geometry within the lagoon environment. The model was then applied using measured NH3 concentrations to achieve emissions estimates. While NH3 fluxes from the lagoon tend to be much lower than those of CH4 by comparison, modeling emissions of NH3 from the simple geometry of a lagoon will assist in applying the model to more complex surfaces. [1] FAO, 2006. Livestock's long shadow: Environmental issues and options. Livestock, Environment, and Development Initiative. Food and Agriculture Organization of the United Nations, Rome, Italy. [2] Loubet, B., Génermont, S., Ferrara, R., Bedos, C., Decuq, C., Personne, E., Fanucci, O., Durand, B., Rana, G., Cellier, P., 2010. An inverse model to estimate ammonia emissions from fields. Eur. J. Soil Sci. 61: 793-805. Panorama of a weather station (left) utilizing micrometeorological methods to aid in estimating emissions of methane and ammonia from an anaerobic livestock lagoon (center) at a commercial dairy in Northern Colorado, USA.

Shonkwiler, K. B.; Ham, J. M.; Williams, C.

2012-12-01

59

Climatic and Chemical Controls on Methane Emissions from Wetlands  

NASA Technical Reports Server (NTRS)

Natural wetlands are the largest single source of methane to the atmosphere and the only one dominated by climate. Although interannual variations in methane emissions from short-term climate variations are becoming better understood, major uncertainties remain with respect to the sensitivity of wetlands and their CH4 emissions to climate variability, the sensitivity of suppression of wetland methane missions to changes in low-dose sulfate deposition, and the response of wetland dynamics to climate variations. We present results from modeling, field, and remote sensing research that integrate current understanding of the dynamics of wetlands and their methane emissions.

Matthews, Elaine; Gauci, Vincent; Prigent, Catherine; Travis, Larry (Technical Monitor)

2002-01-01

60

Anthropogenic emissions of methane in the United States  

PubMed Central

This study quantitatively estimates the spatial distribution of anthropogenic methane sources in the United States by combining comprehensive atmospheric methane observations, extensive spatial datasets, and a high-resolution atmospheric transport model. Results show that current inventories from the US Environmental Protection Agency (EPA) and the Emissions Database for Global Atmospheric Research underestimate methane emissions nationally by a factor of ?1.5 and ?1.7, respectively. Our study indicates that emissions due to ruminants and manure are up to twice the magnitude of existing inventories. In addition, the discrepancy in methane source estimates is particularly pronounced in the south-central United States, where we find total emissions are ?2.7 times greater than in most inventories and account for 24 ± 3% of national emissions. The spatial patterns of our emission fluxes and observed methane–propane correlations indicate that fossil fuel extraction and refining are major contributors (45 ± 13%) in the south-central United States. This result suggests that regional methane emissions due to fossil fuel extraction and processing could be 4.9 ± 2.6 times larger than in EDGAR, the most comprehensive global methane inventory. These results cast doubt on the US EPA’s recent decision to downscale its estimate of national natural gas emissions by 25–30%. Overall, we conclude that methane emissions associated with both the animal husbandry and fossil fuel industries have larger greenhouse gas impacts than indicated by existing inventories.

Miller, Scot M.; Wofsy, Steven C.; Michalak, Anna M.; Kort, Eric A.; Andrews, Arlyn E.; Biraud, Sebastien C.; Dlugokencky, Edward J.; Eluszkiewicz, Janusz; Fischer, Marc L.; Janssens-Maenhout, Greet; Miller, Ben R.; Miller, John B.; Montzka, Stephen A.; Nehrkorn, Thomas; Sweeney, Colm

2013-01-01

61

Methane emissions from a small wind shielded lake determined by eddy covariance, flux chambers, anchored funnels, and boundary model calculations: a comparison.  

PubMed

Lakes are large sources of methane, held to be responsible for 18% of the radiative forcing, to the atmosphere. Periods of lake overturn (during fall/winter) are short and therefore difficult to capture with field campaigns but potentially one of the most important periods for methane emissions. We studied methane emissions using four different methods, including eddy covariance measurements, floating chambers, anchored funnels, and boundary model calculations. Whereas the first three methods agreed rather well, boundary model estimates were 5-30 times lower leading to a strong underestimation of methane fluxes from aquatic systems. These results show the importance of ebullition as the most important flux pathway and the need for continuous measurements with a large footprint covering also shallow parts of lakes. Although fluxes were high, on average 4 mmol m(-2) d(-1) during the overturn period, water column microbial methane oxidation removed 75% of the methane and only 25% of potential emissions were released to the atmosphere. Hence, this study illustrates second the importance of considering methane oxidation when estimating the flux of methane from lakes during overturn periods. PMID:22436104

Schubert, Carsten J; Diem, Torsten; Eugster, Werner

2012-04-17

62

Quantifying methane emissions from rice paddies in Northeast China by integrating remote sensing mapping with a biogeochemical model  

NASA Astrophysics Data System (ADS)

The Sanjiang Plain located in Northeastern China is one of the major rice producing regions in the country. However, differing from the majority rice regions in Southern China, the Sanjinag Plain possesses a much cooler weather. Could the rice paddies in this domain be an important source of global methane? To answer this question, we calculated methane (CH4) emissions from the region by integrating remote sensing mapping with a process-based biogeochemistry model, Denitrification and Decomposition or DNDC. To quantify regional CH4 emissions from the plain, we first tested the model against a two-year dataset of CH4 fluxes measured at a typical rice field within the domian. A sensitivity test was conducted to find out the most sensitive factors affecting CH4 emissions in the region. Based on the understanding gained from the validation and sensitivity tests, a geographic information system (GIS) database was constructed to hold the spatially differentiated input information to drive DNDC for its regional simulations. The GIS database included a rice map derived from the Landsat TM images, which provided crucial information about the spatial distribution of the rice fields within the domain of 10.93 million hectares. The modeled results showed that the total 1.44 million ha of rice paddies in the plain emitted 0.43-0.58 Tg CH4-C per year with spatially differentiated annual emission rates ranging between 100-800 kg CH4-C/ha, which are comparable with that observed in Southern China. The modeled data indicated that the high SOC contents, long crop season and high rice biomass enhanced CH4 production in the cool paddies. The modeled results proved that the northern wetland agroecosystems could make important contributions to global greenhouse gas inventory.

Zhang, Y.; Wang, Y. Y.; Su, S. L.; Li, C. S.

2011-01-01

63

Measuring and modeling nitrous oxide and methane emissions from beef cattle feedlot manure management: First assessments under Brazilian condition.  

PubMed

Intensive beef production has increased during recent decades in Brazil and may substantially increase both methane (CH4) and nitrous oxide (N2O) emissions from manure management. However, the quantification of these gases and methods for extrapolating them are scarce in Brazil. A case study examines CH4 and N2O emissions from one typical beef cattle feedlot manure management continuum in Brazil and the applicability of Manure-DNDC model in predicting these emissions for better understand fluxes and mitigation options. Measurements track CH4 and N2O emissions from manure excreted in one housing floor holding 21 animals for 78 days, stockpiled for 73 days and field spread (360 kg N ha(-1)). We found total emissions (CH4 + N2O) of 0.19 ± 0.10 kg CO2eq per kg of animal live weight gain; mostly coming from field application (73%), followed housing (25%) and storage (2%). The Manure-DNDC simulations were generally within the statistical deviation ranges of the field data, differing in -28% in total emission. Large uncertainties in measurements showed the model was more accurate estimating the magnitude of gases emissions than replicate results at daily basis. Modeled results suggested increasing the frequency of manure removal from housing, splitting the field application and adopting no-tillage system is the most efficient management for reducing emissions from manure (up to about 75%). Since this work consists in the first assessment under Brazilian conditions, more and continuous field measurements are required for decreasing uncertainties and improving model validations. However, this paper reports promising results and scientific perceptions for the design of further integrated work on farm-scale measurements and Manure-DNDC model development for Brazilian conditions. PMID:25035919

Costa, Ciniro; Li, Changsheng; Cerri, Carlos E P; Cerri, Carlos C

2014-09-01

64

Methane emissions (kt of CO2 equivalent)  

NSDL National Science Digital Library

List of countries with their annual methane emissions. The data are from 2005. The data are given in total annual emissions, thus must be compared with economic activity, geographic and most importantly, population data to be relevant.

Bank, World

65

The Impact of Methane Clathrate Emissions on the Earth System  

NASA Astrophysics Data System (ADS)

Methane is locked in ice-like deposits called clathrates in ocean sediments and underneath permafrost regions. Clathrates are stable under high pressures and low temperatures, so in a warming climate, increases in ocean temperatures could lead to dissociation of the clathrates and release methane into the ocean and subsequently the atmosphere, where methane is both an important greenhouse gas and a key species in atmospheric chemistry. Clathrates in the shallower parts of the Arctic Ocean (around 300m depth) are predicted to be particularly important since clathrates at that depth are expected to start outgassing abruptly in the next few decades. We will present the atmospheric impact of such methane emissions using multi-century steady-state simulations with a version of the Community Earth System Model (CESM) that includes atmospheric chemistry. Our simulations include a plausible release from clathrates in the Arctic that increases global methane emissions above present-day conditions by 22%, as well as a scenario with 10 times those clathrate emissions. The CESM model includes a fully interactive physical ocean, to which we added a fast atmospheric chemistry mechanism that represents methane as a fully interactive tracer (with emissions rather than concentration boundary conditions). The results indicate that such Arctic clathrate emissions (1) increase global methane concentrations by an average of 38%, non-uniformly; (2) increase surface ozone concentrations by around 10% globally, and even more in polluted regions; (3) increase methane lifetime by 13%; (4) increase the interannual variability in surface methane, surface ozone, and methane lifetime, and (5) show modest differences in surface temperature and methane lifetime compared to simulations in which the clathrate emissions are distributed uniformly. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Cameron-Smith, P. J.; Bhattacharyya, S.; Bergmann, D. J.; Reagan, M. T.; Elliott, S.; Moridis, G. J.

2013-12-01

66

Estimation method for national methane emission from solid waste landfills  

NASA Astrophysics Data System (ADS)

In keeping with the global efforts on inventorisation of methane emission, municipal solid waste (MSW) landfills are recognised as one of the major sources of anthropogenic emissions generated from human activities. In India, most of the solid wastes are disposed of by landfilling in low-lying areas located in and around the urban centres resulting in generation of large quantities of biogas containing a sizeable proportion of methane. After a critical review of literature on the methodology for estimation of methane emissions, the default methodology has been used in estimation following the IPCC guidelines 1996. However, as the default methodology assumes that all potential methane is emitted in the year of waste deposition, a triangular model for biogas from landfill has been proposed and the results are compared. The methodology proposed for methane emissions from landfills based on a triangular model is more realistic and can very well be used in estimation on global basis. Methane emissions from MSW landfills for the year AD 1980-1999 have been estimated which could be used in computing national inventories of methane emission.

Kumar, Sunil; Gaikwad, S. A.; Shekdar, A. V.; Kshirsagar, P. S.; Singh, R. N.

67

Applying guidance for methane emission estimation for landfills  

SciTech Connect

Quantification of methane emission from landfills is important to evaluate measures for reduction of greenhouse gas emissions. Both the United Nations and the European Union have adopted protocols to ensure quantification of methane emission from individual landfills. The purpose of these protocols is to disclose emission data to regulators and the general public. Criteria such as timeliness, completeness, certainty, comparability, consistency and transparency are set for inclusion of emission data in a publicly accessible database. All methods given as guidance to landfill operators to estimate landfill methane emissions are based on models. In this paper the consequences of applying six different models for estimates of three landfills are explored. It is not the intention of this paper to criticise or validate models. The modelling results are compared with whole site methane emission measurements. A huge difference in results is observed. This raises doubts about the accuracy of the models. It also indicates that at least some of the criteria previously mentioned are not met for the tools currently available to estimate methane emissions from individual landfills. This will inevitably lead to compiling and comparing data with an incomparable origin. Harmonisation of models is recommended. This may not necessarily reduce uncertainty, but it will at least result in comparable, consistent and transparent data.

Scharff, Heijo [NV Afvalzorg, Postbus 2, 1566 ZG Assendelft (Netherlands)]. E-mail: h.scharff@afvalzorg.nl; Jacobs, Joeri [NV Afvalzorg, Postbus 2, 1566 ZG Assendelft (Netherlands)]. E-mail: j.jacobs@afvalzorg.nl

2006-07-01

68

Methane emissions from floodplains in the Amazon Basin: challenges in developing a process-based model for global applications  

NASA Astrophysics Data System (ADS)

Tropical wetlands are estimated to represent about 50% of the natural wetland methane (CH4) emissions and explain a large fraction of the observed CH4 variability on timescales ranging from glacial-interglacial cycles to the currently observed year-to-year variability. Despite their importance, however, tropical wetlands are poorly represented in global models aiming to predict global CH4 emissions. This publication documents a first step in the development of a process-based model of CH4 emissions from tropical floodplains for global applications. For this purpose, the LPX-Bern Dynamic Global Vegetation Model (LPX hereafter) was slightly modified to represent floodplain hydrology, vegetation and associated CH4 emissions. The extent of tropical floodplains was prescribed using output from the spatially explicit hydrology model PCR-GLOBWB. We introduced new plant functional types (PFTs) that explicitly represent floodplain vegetation. The PFT parameterizations were evaluated against available remote-sensing data sets (GLC2000 land cover and MODIS Net Primary Productivity). Simulated CH4 flux densities were evaluated against field observations and regional flux inventories. Simulated CH4 emissions at Amazon Basin scale were compared to model simulations performed in the WETCHIMP intercomparison project. We found that LPX reproduces the average magnitude of observed net CH4 flux densities for the Amazon Basin. However, the model does not reproduce the variability between sites or between years within a site. Unfortunately, site information is too limited to attest or disprove some model features. At the Amazon Basin scale, our results underline the large uncertainty in the magnitude of wetland CH4 emissions. Sensitivity analyses gave insights into the main drivers of floodplain CH4 emission and their associated uncertainties. In particular, uncertainties in floodplain extent (i.e., difference between GLC2000 and PCR-GLOBWB output) modulate the simulated emissions by a factor of about 2. Our best estimates, using PCR-GLOBWB in combination with GLC2000, lead to simulated Amazon-integrated emissions of 44.4 ± 4.8 Tg yr-1. Additionally, the LPX emissions are highly sensitive to vegetation distribution. Two simulations with the same mean PFT cover, but different spatial distributions of grasslands within the basin, modulated emissions by about 20%. Correcting the LPX-simulated NPP using MODIS reduces the Amazon emissions by 11.3%. Finally, due to an intrinsic limitation of LPX to account for seasonality in floodplain extent, the model failed to reproduce the full dynamics in CH4 emissions but we proposed solutions to this issue. The interannual variability (IAV) of the emissions increases by 90% if the IAV in floodplain extent is accounted for, but still remains lower than in most of the WETCHIMP models. While our model includes more mechanisms specific to tropical floodplains, we were unable to reduce the uncertainty in the magnitude of wetland CH4 emissions of the Amazon Basin. Our results helped identify and prioritize directions towards more accurate estimates of tropical CH4 emissions, and they stress the need for more research to constrain floodplain CH4 emissions and their temporal variability, even before including other fundamental mechanisms such as floating macrophytes or lateral water fluxes.

Ringeval, B.; Houweling, S.; van Bodegom, P. M.; Spahni, R.; van Beek, R.; Joos, F.; Röckmann, T.

2014-03-01

69

Methane emissions from natural wetlands  

SciTech Connect

Analyses of air trapped in polar ice cores in conjunction with recent atmospheric measurements, indicate that the atmospheric methane concentration increased by about 250% during the past two or three hundred years (Rasmussen and Khalil, 1984). Because methane is a potent ``greenhouse`` gas, the increasing concentrations are expected to contribute to global warning (Dickinson and Cicerone, 1986). The timing of the methane increase suggests that it is related to the rapid growth of the human population and associated industrialization and agricultural development. The specific causes of the atmospheric methane concentration increase are not well known, but may relate to either increases in methane sources, decreases in the strengths of the sinks, or both.

Meyer, J.L. [Georgia Univ., Athens, GA (United States); Burke, R.A. Jr. [Environmental Protection Agency, Athens, GA (United States). Environmental Research Lab.

1993-09-01

70

Tidal influence on subtropical estuarine methane emissions  

NASA Astrophysics Data System (ADS)

The relatively unstudied subtropical estuaries, particularly in the Southern Hemisphere, represent an important gap in our understanding of global greenhouse gas (GHG) emissions. These systems are likely to form an important component of GHG budgets as they occupy a relatively large surface area, over 38 000 km2 in Australia. Here, we present studies conducted in the Brisbane River estuary, a representative system within the subtropical region of Queensland, Australia. This is a highly modified system typical of 80% of Australia's estuaries. Generally, these systems have undergone channel deepening and straightening for safer shipping access and these modifications have resulted in large increases in tidal reach. The Brisbane River estuary's natural tidal reach was 16 km and this is now 85 km and tidal currents influence double the surface area (9 km2 to 18 km2) in this system. Field studies were undertaken to improve understanding of the driving factors behind methane water-air fluxes. Water-air fluxes in estuaries are usually calculated with the gas exchange coefficient (k) for currents and wind as well as the concentration difference across the water-air interface. Tidal studies in the lower and middle reaches of the estuary were performed to monitor the influence of the tidal stage (a proxy for kcurrent) on methane fluxes. Results for both investigated reaches showed significantly higher methane fluxes during the transition time of tides, the time of greatest tidal currents, than during slack tide periods. At these tidal transition times with highest methane chamber fluxes, lowest methane surface water concentrations were monitored. Modelled fluxes using only wind speed (kwind) were at least one order of magnitude lower than observed from floating chambers, demonstrating that current speed was likely the driving factor of water-air fluxes. An additional study was then conducted sampling the lower, middle and upper reaches during a tidal transition period. Although dissolved methane surface water concentrations were highest in the upper reaches of the estuary, experiencing the lowest tidal currents, fluxes measured using chambers were lower relative to middle and lower reaches. This supports the tidal study findings as higher tidal currents were experienced in the middle and lower reaches. The dominant driver behind estuarine methane water-air fluxes in this system was tidal current speed. Future studies need to take into account flux rates during both transition and slack tide periods to quantify total flux rates.

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

2014-05-01

71

Methane emissions from canopy wetlands  

NASA Astrophysics Data System (ADS)

Ground wetlands are the main natural source of methane but they fail to explain the observed amounts of methane over tropical forests. Bromeliad tanks are discrete habitats for aquatic organisms and up to several thousand of bromeliad individuals per hectare of tropical forest create a unique canopy wetland ecosystem in neotropical forests. Recently, we have discovered that canopy wetlands inhabit methanogenic archaea, emit substantial amounts of methane and may help to explain the high amounts of methane over neotropical forests. However, the pathway of methane formation and potential methane production in canopy wetlands of different tropical forest ecosystems have not yet been studied. In this study, we investigated the stable carbon isotope fractionation, methanogenic pathway and potential methane production of bromeliad tanks along an elevation gradient in neotropical forests for the first time. We sampled the bromeliad tank-substrate of 3 tank bromeliads per functional type and elevation (1000 m, 2000 m and 3000 m above the sea level). We distinguished three functional types of tank bromeliads, based on plant architecture and ecological niche preference. Functional type I-tank bromeliads are concentrated in the understory and on the ground. Functional type II and type III are concentrated in the mid and overstory. We conducted tank-substrate incubation experiments and measured CH4, CO2, 13CH4 and 13CO2 at regular time intervals during the incubation period. The methane production potential of bromeliad tanks correlated positively with tank-substrate carbon concentration and decreased with increasing canopy height and increasing elevation. The dominant pathway of methane formation in bromeliad tanks was hydrogenotrophic methanogenesis (>50%) and this dominance increased with increasing canopy height and increasing elevation. Our results provide novel insights into the pathway of methane formation in neotropical canopy wetlands and suggest that canopy height is a more important indicator than tree or bromeliad species diversity on how methanogenic pathway and methane production changes within canopy wetlands.

Martinson, G. O.; Conrad, R.

2012-12-01

72

Landfill methane balance: Model and practical applications.  

National Technical Information Service (NTIS)

A rational mass-balance framework is described for improved quantification of landfill methane processes at a given site. The methane balance model examines the partitioning of methane generated into methane recovered (via extraction systems), methane emi...

J. Bogner K. Spokas

1995-01-01

73

Measurement and prediction of enteric methane emission  

NASA Astrophysics Data System (ADS)

The greenhouse gas (GHG) emissions from the agricultural sector account for about 25.5% of total global anthropogenic emission. While CO2 receives the most attention as a factor relative to global warming, CH4, N2O and chlorofluorocarbons (CFCs) also cause significant radiative forcing. With the relative global warming potential of 25 compared with CO2, CH4 is one of the most important GHGs. This article reviews the prediction models, estimation methodology and strategies for reducing enteric CH4 emissions. Emission of CH4 in ruminants differs among developed and developing countries, depending on factors like animal species, breed, pH of rumen fluid, ratio of acetate:propionate, methanogen population, composition of diet and amount of concentrate fed. Among the ruminant animals, cattle contribute the most towards the greenhouse effect through methane emission followed by sheep, goats and buffalos, respectively. The estimated CH4 emission rate per cattle, buffaloe, sheep and goat in developed countries are 150.7, 137, 21.9 and 13.7 (g/animal/day) respectively. However, the estimated rates in developing countries are significantly lower at 95.9 and 13.7 (g/animal/day) per cattle and sheep, respectively. There exists a strong interest in developing new and improving the existing CH4 prediction models to identify mitigation strategies for reducing the overall CH4 emissions. A synthesis of the available literature suggests that the mechanistic models are superior to empirical models in accurately predicting the CH4 emission from dairy farms. The latest development in prediction model is the integrated farm system model which is a process-based whole-farm simulation technique. Several techniques are used to quantify enteric CH4 emissions starting from whole animal chambers to sulfur hexafluoride (SF6) tracer techniques. The latest technology developed to estimate CH4 more accurately is the micrometeorological mass difference technique. Because the conditions under which animals are managed vary greatly by country, CH4 emissions reduction strategies must be tailored to country-specific circumstances. Strategies that are cost effective, improve productivity, and have limited potential negative effects on livestock production hold a greater chance of being adopted by producers. It is also important to evaluate CH4 mitigation strategies in terms of the total GHG budget and to consider the economics of various strategies. Although reductions in GHG emissions from livestock industries are seen as high priorities, strategies for reducing emissions should not reduce the economic viability of enterprises.

Sejian, Veerasamy; Lal, Rattan; Lakritz, Jeffrey; Ezeji, Thaddeus

2011-01-01

74

Heritability estimates of methane emissions from sheep.  

PubMed

The objective of this study was to determine the genetic parameters of methane (CH4) emissions and their genetic correlations with key production traits. The trial measured the CH4 emissions, at 5-min intervals, from 1225 sheep placed in respiration chambers for 2 days, with repeat measurements 2 weeks later for another 2 days. They were fed in the chambers, based on live weight, a pelleted lucerne ration at 2.0 times estimated maintenance requirements. Methane outputs were calculated for g CH4/day and g CH4/kg dry matter intake (DMI) for each of the 4 days. Single trait models were used to obtain estimates of heritability and repeatability. Heritability of g CH4/day was 0.29 ± 0.05, and for g CH4/kg DMI 0.13 ± 0.03. Repeatability between measurements 14 days apart were 0.55 ± 0.02 and 0.26 ± 0.02, for the two traits. The genetic and phenotypic correlations of CH4 outputs with various production traits (weaning weight, live weight at 8 months of age, dag score, muscle depth and fleece weight at 12 months of age) measured in the first year of life, were estimated using bivariate models. With the exception of fleece weight, correlations were weak and not significantly different from zero for the g CH4/kg DMI trait. For fleece weight the phenotypic and genetic correlation estimates were -0.08 ± 0.03 and -0.32 ± 0.11 suggesting a low economically favourable relationship. These results indicate that there is genetic variation between animals for CH4 emission traits even after adjustment for feed intake and that these traits are repeatable. Current work includes the establishment of selection lines from these animals to investigate the physiological, microbial and anatomical changes, coupled with investigations into shorter and alternative CH4 emission measurement and breeding value estimation techniques; including genomic selection. PMID:23739473

Pinares-Patiño, C S; Hickey, S M; Young, E A; Dodds, K G; MacLean, S; Molano, G; Sandoval, E; Kjestrup, H; Harland, R; Hunt, C; Pickering, N K; McEwan, J C

2013-06-01

75

Methane emissions from natural wetlands.  

National Technical Information Service (NTIS)

Analyses of air trapped in polar ice cores in conjunction with recent atmospheric measurements, indicate that the atmospheric methane concentration increased by about 250% during the past two or three hundred years (Rasmussen and Khalil, 1984). Because me...

J. L. Meyer R. A. Burke

1993-01-01

76

METHANE EMISSIONS FROM THE NATURAL GAS INDUSTRY  

EPA Science Inventory

The paper discusses a project to quantify methane (CH4) emissions from the U.S. natural gas industry. his study will measure or calculate all gas industry CH4 emissions--from production at the wellhead, through the system, to the customer's meter. missions downstream of the consu...

77

Modelling global methane emissions from livestock: Biological and nutritional controls. Final Report, 1 July 1989-30 June 1992  

SciTech Connect

The available observations of methane production from the literature have been compiled into a ruminant methane data base. This data base includes 400 treatment mean observations of methane losses from cattle and sheep, and minor numbers of measurements from other species. Methane loss varied from 2.0 to 11.6 percent of dietary gross energy. Measurements included describe the many different weights and physiological states of the animals fed and diets ranging from all forage to all concentrate diets or mixtures. An auxiliary spreadsheet lists approximately 1000 individual animal observations. Many important concepts have emerged from our query and analysis of this data set. The majority of the world's cattle, sheep, and goats under normal husbandry circumstances likely produce methane very close to 6 percent of their daily diets gross energy (2 percent of the diet by weight). Although individual animals or losses from specific dietary research circumstances can vary considerably, the average for the vast majority of groups of ruminant livestock are likely to fall between 5.5 to 6.5 percent. We must caution, however, that little experimental data is available for two-thirds of the world's ruminants in developing countries. Available evidence suggests similar percentage of emissions, but this supposition needs confirmation. More importantly, data is skimpy or unavailable to describe diet consumption, animal weight, and class distribution.

Johnson, D.E.

1992-10-01

78

Microbial methane oxidation processes and technologies for mitigation of landfill gas emissions.  

PubMed

Landfill gas containing methane is produced by anaerobic degradation of organic waste. Methane is a strong greenhouse gas and landfills are one of the major anthropogenic sources of atmospheric methane. Landfill methane may be oxidized by methanotrophic microorganisms in soils or waste materials utilizing oxygen that diffuses into the cover layer from the atmosphere. The methane oxidation process, which is governed by several environmental factors, can be exploited in engineered systems developed for methane emission mitigation. Mathematical models that account for methane oxidation can be used to predict methane emissions from landfills. Additional research and technology development is needed before methane mitigation technologies utilizing microbial methane oxidation processes can become commercially viable and widely deployed. PMID:19584243

Scheutz, Charlotte; Kjeldsen, Peter; Bogner, Jean E; De Visscher, Alex; Gebert, Julia; Hilger, Helene A; Huber-Humer, Marion; Spokas, Kurt

2009-08-01

79

Methane emission from rice paddies  

Microsoft Academic Search

Methane release rates from rice paddies have been measured in Andalusia, Spain, during almost a complete vegetation period in 1982 using the static box system. The release rates ranged between 2 and 14 mg\\/m2\\/h and exhibited a strong seasonal variation with low values during the tillering stage and shortly before harvest, while maximum values were observed at the end of

W. Seiler; A. Holzapfel-Pschorn; R. Conrad; D. Scharffe

1983-01-01

80

MEASUREMENT OF METHANE EMISSIONS FROM UNDERGROUND DISTRIBUTION MAINS AND SERVICES  

EPA Science Inventory

The paper reports results of measurements of methane emissions from underground distribution mains and services. he losses from the underground distribution network were estimated to be a significant source of methane emissions from the natural gas industry. ata acquired through ...

81

Methane emissions from natural wetlands  

Microsoft Academic Search

Methane is considered one of the most important greenhouse gases in the atmosphere. Because of the strict anaerobic conditions required by CH4-generating microorganisms, natural wetland ecosystems are one of the main sources of biogenic CH4. The total natural wetland area is estimated to be 5.3 to 5.7 × 1012 m2, making up less than 5% of the Earth's land surface.

Zhengping Wang; Dong Zeng; William H. Patrick

1996-01-01

82

METHANE EMISSIONS FROM ABANDONED UNDERGROUND COAL MINES  

EPA Science Inventory

The paper summarizes current research on abandoned underground coal mines. t forms an initial basis for developing an inventory of methane emissions from such mines. arly measurements have shown that some abandoned coal mines can liberate large volumes of high quality gas (up to ...

83

Diel methane emission patterns from Scirpus lacustris and Phragmites australis  

Microsoft Academic Search

In mature Phragmites australis and Scirpus lacustris vegetated sediment methane was emitted almost exclusively by plant-mediated transport, whereas in unvegetated, but otherwise identical sediment, methane was emitted almost exclusively by ebullition. Diel variations in methane emission, with highest emission rates at daytime and emission peaks following sunrise, were demonstrated for Phragmites and Scirpus. The diel difference and magnitude of the

Frans-Faco W. A. Van Der Nat; Daniëlle Van Meteren; Annette Wielemakers

1998-01-01

84

Biotic systems to mitigate landfill methane emissions.  

PubMed

Landfill gases produced during biological degradation of buried organic wastes include methane, which when released to the atmosphere, can contribute to global climate change. Increasing use of gas collection systems has reduced the risk of escaping methane emissions entering the atmosphere, but gas capture is not 100% efficient, and further, there are still many instances when gas collection systems are not used. Biotic methane mitigation systems exploit the propensity of some naturally occurring bacteria to oxidize methane. By providing optimum conditions for microbial habitation and efficiently routing landfill gases to where they are cultivated, a number of bio-based systems, such as interim or long-term biocovers, passively or actively vented biofilters, biowindows and daily-used biotarps, have been developed that can alone, or with gas collection, mitigate landfill methane emissions. This paper reviews the science that guides bio-based designs; summarizes experiences with the diverse natural or engineered substrates used in such systems; describes some of the studies and field trials being used to evaluate them; and discusses how they can be used for better landfill operation, capping, and aftercare. PMID:18338700

Huber-Humer, Marion; Gebert, Julia; Hilger, Helene

2008-02-01

85

Atmospheric Impact of Large Methane Emission in the Arctic Region  

NASA Astrophysics Data System (ADS)

A highly potent greenhouse gas, methane, is locked in the solid phase as ice-like deposits containing a mixture of water and gas (mostly methane) called clathrates, in ocean sediments and underneath permafrost regions. Clathrates are stable under high pressure and low temperatures. Recent estimates suggest that about 1600 - 2000GtC of clathrates are present in oceans and 400GtC in Arctic permafrost (Archer et al.2009) which is about 4000 times that of current annual emissions. In a warming climate, increase in ocean temperatures could alter the geothermal gradient, which in turn could lead to dissociation of the clathrates and release of methane into the ocean and subsequently into the atmosphere as well. This could be of particular importance in the shallow part of the Arctic Ocean where the clathrates are found in depths of only 300m. In this presentation, we shall show results from our ongoing simulation of a scenario of large scale methane outgassing from clathrate dissociation due to warming ocean temperatures in the Arctic based on ocean sediment modeling. To that end we use the CESM (Community Earth System Model) version 1 with fully active coupled atmosphere-ocean-land model together with fast atmospheric chemistry module to simulate the response to increasing methane emissions in the Barents Sea, Canadian Archipelago and the Sea of Okhotsk. The simulation shows the effect these methane emissions could have on global surface methane, surface ozone, surface air temperature and other related indices. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-491764

Bhattacharyya, S.; Cameron-Smith, P. J.; Bergmann, D.; Reagan, M. T.; Collins, W.; Elliott, S. M.; Maltrud, M. E.

2011-12-01

86

Impact of Changes in Barometric Pressure on Landfill Methane Emission  

NASA Astrophysics Data System (ADS)

Landfill methane emissions were measured continuously using the eddy covariance method from June to December 2010. The study site was located at the Bluff Road Landfill in Lincoln, Nebraska USA. Methane emissions strongly depended on changes in barometric pressure; rising barometric pressure suppressed the emission, while falling barometric pressure enhanced the emission. Emission rates were systematically higher in December than during the summer period. Higher methane emission rates were associated with changes in barometric pressure that were larger in magnitude and longer in duration in winter than in summer, and with lower mean temperatures, which appeared to reduce methane oxidation rates. Sharp changes in barometric pressure caused up to 35-fold variation in day-to-day methane emissions. Power spectrum and ogive analysis showed that continuous measurements over a period of at least 10 days were needed in order to capture 90% of total variance in the methane emission time series at our site. Our results suggest that point-in-time methane emission rate measurements taken at monthly or even longer time intervals using techniques such as the tracer plume method, the mass balance method, or the closed-chamber method may be subject to large variations because of the strong dependence of methane emissions on changes in barometric pressure. Estimates of long-term integrated methane emissions from landfills based on such measurements will inevitably yield large uncertainties. Our results demonstrate the value of continuous measurements for quantifying total annual methane emission from a landfill.

McDermitt, Dayle; Xu, Liukang; Lin, Xiaomao; Amen, Jim; Welding, Karla

2013-04-01

87

Controls on methane emissions from Alnus glutinosa saplings.  

PubMed

Recent studies have confirmed significant tree-mediated methane emissions in wetlands; however, conditions and processes controlling such emissions are unclear. Here we identify factors that control the emission of methane from Alnus glutinosa. Methane fluxes from the soil surface, tree stem surfaces, leaf surfaces and whole mesocosms, pore water methane concentrations and physiological factors (assimilation rate, stomatal conductance and transpiration) were measured from 4-yr old A. glutinosa trees grown under two artificially controlled water-table positions. Up to 64% of methane emitted from the high water-table mesocosms was transported to the atmosphere through A. glutinosa. Stem emissions from 2 to 22 cm above the soil surface accounted for up to 42% of total tree-mediated methane emissions. Methane emissions were not detected from leaves and no relationship existed between leaf surface area and rates of tree-mediated methane emissions. Tree stem methane flux strength was controlled by the amount of methane dissolved in pore water and the density of stem lenticels. Our data show that stem surfaces dominate methane egress from A. glutinosa, suggesting that leaf area index is not a suitable approach for scaling tree-mediated methane emissions from all types of forested wetland. PMID:24219654

Pangala, Sunitha R; Gowing, David J; Hornibrook, Edward R C; Gauci, Vincent

2014-02-01

88

News about methane emission from plant matter  

NASA Astrophysics Data System (ADS)

Almost two years ago, Keppler et al. [2006] published results from laboratory experiments indicating that living plants, plant litter and the structural plant component pectin emit methane to the atmosphere under aerobic conditions. These findings contradict the accepted view that methane can be formed under oxygen-free conditions only, and in fact we still lack a fundamental understanding of the production process. They also have far-reaching implications since they imply a new and possibly important plant-climate feedback, since the global source strength estimated from those laboratory measurements was large. The scientific debate first concentrated on the up-scaling approach, and several other approaches have been suggested. However, since no up-scaling rule has been identified, also other up-scaling methods lack a solid scientific basis and the fundamental question at this stage is whether aerobic CH4 emissions from the biosphere do actually exist. Several possible experimental artifacts in the experiments of Keppler et al. have been suggested, and in fact one recent study has reported the absence of CH4 emissions from vegetation [Dueck, et al., 2007], but the discrepancy to the measurements of Keppler et al. could not be explained. In our follow up research we have aimed at proving that an aerobic CH4 production mechanism does indeed exist. Our new results - obtained with different analytical techniques - show that dry and fresh plant matter, as well as several structural plant components, emit significant amounts of methane upon irradiation with UV light and heating. Emissions from UV irradiation are almost instantaneous, indicating a direct photochemical process. The size of the methane-forming reservoir exceeds the size of suggested contamination sources by several orders of magnitude. A dry leaf of a pure 13C plant also produces 13CH¬4. References Dueck, T. A., R. de Visser, H. Poorter, S. Persijn, A. Gorissen, W. de Visser, A. Schapendonk, J. Verhagen, J. Snel, F. J. M. Harren, A. K. Y. Ngai, F. Verstappen, H. Bouwmeester, L. A. C. J. Voesenek, and A. van der Werf, No evidence for substantial aerobic methane emission by terrestrial plants: a 13C-labelling approach New Phytologist, doi : 10.1111/j.1469-8137.2007.02103.x, 2007. Keppler, F., J. T. G. Hamilton, M. Brass, and T. Röckmann, Methane emissions from terrestrial plants under aerobic conditions, Nature, 439, 187-191, doi:110.1038/nature04420, 2006.

Röckmann, T.; Vigano, I.; Holzinger, R.; van Weelden, H.; Keppler, F.

2007-12-01

89

Methane emissions from floodplain swamps of the Ogeechee River: long-term patterns and effects of climate change  

Microsoft Academic Search

Patterns and rates of wetland methane emissions and their sensitivity to potential climate change are critical components of the global methane cycle. In this study, we use empirical simulation models to investigate these processes in floodplain swamps of the Ogeechee River in Georgia, U.S.A. We developed statistical models that relate methane emissions to monthly climate and river flow based on

William M. Pulliam; Judy L. Meyer

1992-01-01

90

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

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

91

Quantifying the relative contribution of natural gas fugitive emissions to total methane emissions in Colorado, Utah, and Texas using mobile isotopic methane analysis based on Cavity Ringdown Spectroscopy  

NASA Astrophysics Data System (ADS)

Fugitive emissions of methane into the atmosphere are a major concern facing the natural gas production industry. Because methane is more energy-rich than coal per kg of carbon dioxide emitted into the atmosphere, it represents an attractive alternative to coal for electricity generation, provided that the fugitive emissions of methane are kept under control. A key step in assessing these emissions in a given region is partitioning the observed methane emissions between natural gas fugitive emissions and other sources of methane, such as from landfills or agricultural activities. One effective method for assessing the contribution of these different sources is stable isotope analysis, using the isotopic carbon signature to distinguish between natural gas and landfills or ruminants. We present measurements of methane using a mobile spectroscopic stable isotope analyzer based on cavity ringdown spectroscopy, in three intense natural gas producing regions of the United States: the Denver-Julesburg basin in Colorado, the Uintah basin in Utah, and the Barnett Shale in Texas. Performance of the CRDS isotope analyzer is presented, including precision, calibration, stability, and the potential for measurement bias due to other atmospheric constituents. Mobile isotope measurements of individual sources and in the nocturnal boundary layer have been combined to establish the fraction of the observed methane emissions that can be attributed to natural gas activities. The fraction of total methane emissions in the Denver-Julesburg basin attributed to natural gas emissions is 78 +/- 13%. In the Uinta basin, which has no other significant sources of methane, the fraction is 96% +/- 15%. In addition, results from the Barnett shale are presented, which includes a major urban center (Dallas / Ft. Worth). Methane emissions in this region are spatially highly heterogeneous. Spatially-resolved isotope and concentration measurements are interpreted using a simple emissions model to arrive at an overall isotope ratio for the region.

Rella, Chris; Winkler, Renato; Sweeney, Colm; Karion, Anna; Petron, Gabrielle; Crosson, Eric

2014-05-01

92

Capturing fugitive methane emissions from natural gas compressor buildings  

Microsoft Academic Search

Fugitive methane emissions account for about 50% of the greenhouse gas (GHG) emissions from the Canadian conventional oil and gas sector. Sources include leaks in natural gas transmission facilities such as pipelines and compressor stations. There are three sources of methane emissions in a compressor station. The first is emissions resulting from incomplete combustion in the engine; the second is

R. Litto; R. E. Hayes; B. Liu

2007-01-01

93

The controls of methane emission from an Indian mangrove  

NASA Astrophysics Data System (ADS)

Mangroves have been rated for a long time as a minor methane source, but recent reports have shown that polluted mangroves may emit substantial amounts of methane. In an Indian mangrove dominated by Avicennia marina we measured annual methane emission rates of 10 g methane/year, comparable to those from Northern wetlands. Methane emission from a freshwater-influenced area was higher, but lower from a stunted mangrove growing on a hypersaline soil, respectively. Methane emission was mediated by the pneumatophores of Avicennia. This was consistent with the methane concentration in the aerenchyma that decreased on average from 350 ppmv in the cable roots to 10 ppmv in the emergent part of the pneumatophores. The number of pneumatophores varied seasonally. During the monsoon floods less pneumatophores emerged from the water, reducing methane fluxes largely. Hence, CH4 emission was controlled via the pneumatophores by the water level.

Purvaja, R.; Ramesh, R.; Frenzel, P.

2003-04-01

94

THE ROLE OF COVER SOIL IN MITIGATION OF METHANE EMISSION FROM SOLID WASTE DISPOSAL SITES  

Microsoft Academic Search

Methane is known as an important greenhouse gas. Since solid waste landfill and open dump are one of the methane emission sources, thus, aim of this study was to determine methane emission from these areas. Development of mitigation technique for methane emission from open dump via a biological methane oxidation was also investigated in this study. Methane emission rates (MER)

Wilai Chiemchaisri; Chart Chiemchaisri

95

Offsetting Ongoing Methane Emissions --- An Alternative to Emission Equivalence Metrics  

NASA Astrophysics Data System (ADS)

The Global Warming Potential (GWP) has been widely adopted as a metric for comparing the climate impact of different greenhouse gases. As has been frequently noted, there are many problems with using GWPs to define emission equivalence in spite of the use of GWPs for this purpose in contexts such as the Kyoto Protocol. We propose that for methane, rather than define emission equivalence, the appropriate comparison is between ongoing emissions of 0.9 to 1.0 kg of CH4 per year and one-off emissions of 1 tonne of carbon. This approach represents an approximate solution to the inverse problem of defining a forcing equivalent index (FEI) that gives exact equivalence of radiative forcing over a range of timescales. In our approach, if ongoing methane emissions are offset by a one-off carbon removal that is built up with 40-year e-folding time, then the result is close to radiatively neutral over periods from years to centuries. In contrast, the GWP provides radiative equivalence (in integrated terms) only at a single time, with large discrepancies at other times. Our approach also follows from consideration of greenhouse gas stabilisation, since stabilising atmospheric CO2 requires an approximate cap on total emissions, while stabilising methane requires stabilisation of ongoing emissions. Our quantitative treatment recognises that, on time scales of centuries, removal of 1 tonne of carbon only lowers the atmospheric carbon content by 0.3 to 0.35 tonnes. We discuss the implications for rangeland grazing systems. In the absence of effective mitigation techniques for methane from rangeland systems, this approach may provide an attractive offset mechanism in spite of requiring that woody vegetation be established and maintained over about 15% of the landscape, or an equivalent amount of carbon storage in soil.

Clisby, N.; Enting, I. G.; Lauder, A.; Carter, J.; Cowie, A.; Henry, B.; Raupach, M. R.

2012-12-01

96

Methane in the Baltic and North Seas and a reassessment of the marine emissions of methane  

SciTech Connect

During three measurement campaigns on the Baltic and North Seas, atmospheric and dissolved methane was determined with an automated gas chromatographic system. Area-weighted mean saturation values in the sea surface waters were 113{+-}5% and 395{+-}82% and 126{+-}8%. On the bases of our data and a compilation of literature data the global oceanic emissions of methane were reassessed by introducing a concept of regional gas transfer coefficients. Our estimates computed with two different air-sea exchange models lie in the range of 11-18 Tg CH{sub 4} yr{sup -1}. Despite the fact that shelf areas and estuaries only represent a small part of the world`s ocean they contribute about 75% to the global oceanic emissions. We applied a simple, coupled, three-layer model to evaluate the time dependent variation of the oceanic flux to the atmosphere. The model calculations indicate that even with increasing tropospheric methane concentration, the ocean will remain a source of atmospheric methane. 72 refs., 7 figs., 7 tabs.

Bange, H.W.; Bartell, U.H.; Rapsomanikis, S. [Max Planck Institute for Chemistry, Mainz (Germany)] [and others] [Max Planck Institute for Chemistry, Mainz (Germany); and others

1994-12-01

97

Methane Emissions Inventory Verification in Southern California  

NASA Astrophysics Data System (ADS)

The California Global Warming Solutions Act of 2006 (AB 32) requires the California Air Resources Board (CARB) to report and verify the statewide greenhouse gases (GHG) emissions inventory. In support of this program, CARB installed an air quality monitoring station near the Mt. Wilson Observatory to study GHG emissions in Southern California. Methane (CH4) and carbon monoxide (CO) have been measured since the spring of 2007. Both compounds are considered to be non-reactive on the time scale of dispersion and sources of both gases are likely to be similarly distributed (e.g., with population) and subject to similar scales of atmospheric transport and dilution. Therefore, the relationship of CH4 and CO allows scaling the CH4 emissions to the well known CO emissions. Using this approach, a "top-down" CH4 inventory was developed for South Coast Air Basin (SoCAB), based on measurements at Mt. Wilson. We compared this estimate with CARB's "official" GHG emissions inventory which is based on the Intergovernmental Panel on Climate Change (IPCC) recommended methodologies. The CH4 emissions inventory estimated from the observations at Mt. Wilson is approximately 14% to 33% greater than CARB's CH4 emissions inventory. Considering the uncertainties in both methodologies, the two CH4 emissions inventories are reasonably close.

Hsu, Y.; Vancuren, R.; Blake, D.

2008-12-01

98

Methane emissions from rice fields: Effects of soil properties  

NASA Astrophysics Data System (ADS)

Flooded rice fields emit methane and are important contributors to the increasing atmospheric methane concentration. Various estimates of global release rates of methane from rice paddies range from a low of 20 Tg per year to a high of 200 Tg per year. Global estimates of methane emissions from rice fields depend upon obtaining reliable data from a variety of soil types. We have compared a variety of methane emission data sets obtained over a four-year period from three different soil types found at the Texas Agricultural Experiment Station near Beaumont, Texas, with several physical and chemical properties of the soils. We find that seasonal methane emissions directly correlate with the percent sand in the soils. Along a transect with soil sand content ranging from 18.8% to 32.5%, seasonal methane emissions ranged from 15.1 g m -2 to 36.3 g m-2.

Sass, R. L.; Fisher, F. M.; Lewis, S. T.; Jund, M. F.; Turner, F. T.

1994-06-01

99

Methane emissions from cypress knees in a southeastern floodplain swamp  

Microsoft Academic Search

Methane emissions were observed from knees of baldcypress (Taxodium distichum) in floodplain swamps of the Ogeechee river, a blackwater river in the lower coastal plain of Georgia, USA Emissions were sampled on 10 dates from March 1988 to September 1989, with small chambers placed over single knees. Methane emission rates from individual knees averaged 0.90 mg\\/d, corresponding to an average

W. M. Pulliam

1992-01-01

100

Estimation of methane emissions from a wastewater treatment plant in Valence  

NASA Astrophysics Data System (ADS)

Methane is the second most important anthropogenic greenhouse gas emitted; its 20 year global-warming potential is about 56 to 72 depending on authors. One of its sources is the treatment of wastewaters and more particularly anaerobic digestion processes and sludge treatment. To reduce methane emissions from wastewater treatment plants, it is necessary to precisely quantify the amount emitted globally by the plant but also for each step of the process. Fixing the potential leaks and collecting the methane emitted by the different processes allows to reduce methane emissions and costs as methane can be sold or used on-site as an energy source. Moreover improve methods to estimate flow from atmospheric measurements of methane will reduce uncertainties in the inversion models. Several measurement campaigns have been realized in the wastewater treatment plant of Valence, France. This plant treats up to 2800 m3/h of polluted water through a biological treatment. To quantify methane emissions from this wastewater treatment plant, a dual tracer method had been used. It consists in releasing acetylene collocated with the methane source and in measuring both concentrations in the emitted plumes. In parallel, an atmospheric local scale model was used to compare with the experimental results. The higher concentration of methane's emissions was observed around the wastewater arrival. Plant's emissions are in the same range as estimations from the CITEPA French inventory. Measurements during the campaign are well correlated with the model results.

Ars, Sébastien; Yver Kwok, Camille; Bousquet, Philippe; Broquet, Grégoire; Ciais, Philippe; Wu, Lin

2014-05-01

101

Sediment trapping by dams creates methane emission hot spots.  

PubMed

Inland waters transport and transform substantial amounts of carbon and account for ?18% of global methane emissions. Large reservoirs with higher areal methane release rates than natural waters contribute significantly to freshwater emissions. However, there are millions of small dams worldwide that receive and trap high loads of organic carbon and can therefore potentially emit significant amounts of methane to the atmosphere. We evaluated the effect of damming on methane emissions in a central European impounded river. Direct comparison of riverine and reservoir reaches, where sedimentation in the latter is increased due to trapping by dams, revealed that the reservoir reaches are the major source of methane emissions (?0.23 mmol CH4 m(-2) d(-1) vs ?19.7 mmol CH4 m(-2) d(-1), respectively) and that areal emission rates far exceed previous estimates for temperate reservoirs or rivers. We show that sediment accumulation correlates with methane production and subsequent ebullitive release rates and may therefore be an excellent proxy for estimating methane emissions from small reservoirs. Our results suggest that sedimentation-driven methane emissions from dammed river hot spot sites can potentially increase global freshwater emissions by up to 7%. PMID:23799866

Maeck, Andreas; Delsontro, Tonya; McGinnis, Daniel F; Fischer, Helmut; Flury, Sabine; Schmidt, Mark; Fietzek, Peer; Lorke, Andreas

2013-08-01

102

Methane emission by bubbling from Gatun Lake, Panama  

Microsoft Academic Search

We studied methane emission by bubbling from Gatun Lake, Panama, at water depths of less than 1 m to about 10 m. Gas bubbles were collected in floating traps deployed during 12- to 60-hour observation periods. Comparison of floating traps and floating chambers showed that about 98% of methane emission occurred by bubbling and only 2% occurred by diffusion. Average

Michael Keller; Robert F. Stallard

1994-01-01

103

Evaluation of the SF6 tracer technique for estimating methane emission rates with reference to dairy cows using a mechanistic model.  

PubMed

A dynamic, mechanistic model of the sulfur hexafluoride (SF6) tracer technique, used for estimating methane (CH4) emission rates from ruminants, was constructed to evaluate the accuracy of the technique. The model consists of six state variables and six zero-pools representing the quantities of SF6 and CH4 in rumen and hindgut fluid, in rumen and hindgut headspace, and in blood and collection canister. The model simulates flows of CH4 and SF6 through the body, subsequent eructation and exhalation and accumulation in a collection canister. The model predicts CH4 emission by multiplying the SF6 release rate of a permeation device in the rumen by the ratio of CH4:SF6 in collected air. This prediction is compared with the actual CH4 production rate, assumed to be continuous and used as a driving variable in the model. A sensitivity analysis was conducted to evaluate the effect of changes in several parameters. The predicted CH4 emission appeared sensitive to parameters affected by the difference in CH4:SF6 ratio in exhaled and eructed air respectively, viz., hindgut fractional passage rate and hindgut CH4 production. This is caused by the difference in solubility of CH4 and SF6 and by hindgut CH4 production. In addition, the predicted CH4 emission rate appeared sensitive to factors that affect proportions of exhaled and eructed air sampled, i.e., eructation time fraction, exhalation time fraction, and distance from sampling point to mouth/nostrils. Changes in rumen fractional passage rate, eructation rate, SF6 release rate, background values and air sampling rate did not noticeably affect the predicted CH4 emission. Simulations with (13)CH4 as an alternative tracer show that the differences and sensitivity to parameters greatly disappear. The model is considered a useful tool to evaluate critical points in the SF6 technique. Data from in vivo experiments are needed to further evaluate model simulations. PMID:24625680

Berends, H; Gerrits, W J J; France, J; Ellis, J L; van Zijderveld, S M; Dijkstra, J

2014-07-21

104

Effect of water and heat transport processes on methane emissions from paddy soils: a process-based model analysis  

NASA Astrophysics Data System (ADS)

High CH4 fluxes are emitted from paddy fields worldwide and represent a considerable issue for the rice production eco-sustainability. Water and heat transport fluxes are known to strongly influence biogeochemical cycles in wetland environments, and therefore also CH4 emissions from paddy soils. Water percolation affects the dynamics of many compounds (e.g. DOC, O2) influencing CH4 fate. On the other hand, heat fluxes strongly influence CH4 production in submerged rice crops, and lowering ponding water temperature (LPWT) can reduce microbial activities and consequently decrease CH4 emissions. Moreover, as long as the optimal temperature range for rice growth is maintained, LPWT can lower CH4 emissions without rice yield limitation. Hence, a process-based model is proposed and applied to investigate the role of water flow on CH4 emissions, and to analyse the efficiency of LPWT as mitigation strategy for CH4 production and release. The process-based model relies on a system of partial differential mass balance equations to describe the vertical dynamics of the chemical compounds leading to CH4 production. Many physico-chemical processes and features characteristic of paddy soil are included: paddy soil stratigraphy; spatio-temporal variations of plant-root compartment; water and heat transport; SOC decomposition; heterotrophic reactions in both aerobic and anaerobic conditions; root radial oxygen loss; root solute uptake; DOC root exudation; plant-mediated, ebullition, and diffusion gas exchange pathways. LPWT is included as a temperature shift subtracted directly to the ponding water temperature. Model results confirm the importance of water flow on CH4 emission, since simulations that do not include water fluxes show a considerable overestimation of CH4 emissions due to a different DOC spatio-temporal dynamics. Particularly, when water fluxes are not modeled the overestimation can reach 67 % of the total CH4 emission over the whole growing season. Moreover, model results also suggest that roots influence CH4 dynamics principally due to their solute uptake, while root effect on advective flow plays a minor role. In addition, the analysis of CH4 transport fluxes show the limiting effect of upward dispersive transport fluxes on the downward CH4 percolation. Finally, LPWT is confirmed to be a valid mitigation strategy for CH4 emissions from paddy soils, since the reduction of CH4 emission reach about -50 % with a LPWT equal to only 2°C over the whole growing season.

Rizzo, Anacleto; Boano, Fulvio; Revelli, Roberto; Ridolfi, Luca

2013-04-01

105

Spatial variability of methane: attributing atmospheric concentrations to emissions.  

PubMed

Atmospheric methane concentrations were quantified along transects in Switzerland, using a mobile laser spectrometer combined with a GPS, to identify their spatio-temporal patterns and their controlling factors. Based on these measurements in complex terrain dominated by agriculture, three main factors were found to be responsible for the diurnal and regional patterns of atmospheric methane: (1) magnitude and distribution of methane sources within the region, (2) efficiency of vertical exchange, and (3) local wind patterns within the complex topography. An autocorrelation analysis of measured methane concentrations showed that nighttime measurements close to the ground provide information about regional sources (up to 8.3 km), while daytime measurements only carry information about sources located up to 240 m away in the upwind fetch. Compared to daytime concentrations, nighttime methane concentrations do also better reflect emissions obtained from a spatially explicit methane emission inventory and allowed the investigation of inconsistencies in this emission inventory. PMID:24727588

Bamberger, I; Stieger, J; Buchmann, N; Eugster, W

2014-07-01

106

Non-microbial methane emissions from soils  

NASA Astrophysics Data System (ADS)

Traditionally, methane (CH4) is anaerobically formed by methanogenic archaea. However, non-microbial CH4 can also be produced from geologic processes, biomass burning, animals, plants, and recently identified soils. Recognition of non-microbial CH4 emissions from soils remains inadequate. To better understand this phenomenon, a series of laboratory incubations were conducted to examine effects of temperature, water, and hydrogen peroxide (H2O2) on CH4 emissions under both aerobic and anaerobic conditions using autoclaved (30 min, 121 °C) soils and aggregates (>2000 ?m, A1; 2000-250 ?m, A2; 250-53 ?m, M1; and <53 ?m, M2). Results show that applying autoclaving to pre-treat soils is effective to inhibit methanogenic activity, ensuring the CH4 emitted being non-microbial. Responses of non-microbial CH4 emissions to temperature, water, and H2O2 were almost identical between aerobic and anaerobic conditions. Increasing temperature, water of proper amount, and H2O2 could significantly enhance CH4 emissions. However, the emission rates were inhibited and enhanced by anaerobic conditions without and with the existence of H2O2, respectively. As regards the aggregates, aggregate-based emission presented an order of M1 > A2 > A1 > M2 and C-based emission an order of M2 > M1 > A1 > A2, demonstrating that both organic carbon quantity and property are responsible for CH4 emissions from soils at the scale of aggregate. Whole soil-based order of A2 > A1 > M1 > M2 suggests that non-microbial CH4 release from forest soils is majorly contributed by macro-aggregates (i.e., >250 ?m). The underlying mechanism is that organic matter through thermal treatment, photolysis, or reactions with free radicals produce CH4, which, in essence, is identical with mechanisms of other non-microbial sources, indicating that non-microbial CH4 production may be a widespread phenomenon in nature. This work further elucidates the importance of non-microbial CH4 formation which should be distinguished from the well-known microbial CH4 formation in order to define both roles in the atmospheric CH4 global budget.

Wang, Bin; Hou, Longyu; Liu, Wei; Wang, Zhiping

2013-12-01

107

Atmospheric Inverse Estimates of Methane Emissions from Central California  

SciTech Connect

Methane mixing ratios measured at a tall-tower are compared to model predictions to estimate surface emissions of CH{sub 4} in Central California for October-December 2007 using an inverse technique. Predicted CH{sub 4} mixing ratios are calculated based on spatially resolved a priori CH{sub 4} emissions and simulated atmospheric trajectories. The atmospheric trajectories, along with surface footprints, are computed using the Weather Research and Forecast (WRF) coupled to the Stochastic Time-Inverted Lagrangian Transport (STILT) model. An uncertainty analysis is performed to provide quantitative uncertainties in estimated CH{sub 4} emissions. Three inverse model estimates of CH{sub 4} emissions are reported. First, linear regressions of modeled and measured CH{sub 4} mixing ratios obtain slopes of 0.73 {+-} 0.11 and 1.09 {+-} 0.14 using California specific and Edgar 3.2 emission maps respectively, suggesting that actual CH{sub 4} emissions were about 37 {+-} 21% higher than California specific inventory estimates. Second, a Bayesian 'source' analysis suggests that livestock emissions are 63 {+-} 22% higher than the a priori estimates. Third, a Bayesian 'region' analysis is carried out for CH{sub 4} emissions from 13 sub-regions, which shows that inventory CH{sub 4} emissions from the Central Valley are underestimated and uncertainties in CH{sub 4} emissions are reduced for sub-regions near the tower site, yielding best estimates of flux from those regions consistent with 'source' analysis results. The uncertainty reductions for regions near the tower indicate that a regional network of measurements will be necessary to provide accurate estimates of surface CH{sub 4} emissions for multiple regions.

Zhao, Chuanfeng; Andrews, Arlyn E.; Bianco, Laura; Eluszkiewicz, Janusz; Hirsch, Adam; MacDonald, Clinton; Nehrkorn, Thomas; Fischer, Marc L.

2008-11-21

108

Methane Emissions from Rice Fields - Final Report  

SciTech Connect

Methane (Ch4) is a greenhouse gas regarded second only to carbon dioxide in its ability to cause global warming. Methane is important because of its relatively fast increase, and also because it is, per molecule, some 60 times more effective than carbon dioxide in causing global warming. The largest present anthropogenic sources of methane are rice fields, cattle and biomass burning.

Khalil, M. Aslam; Rasmussen,Reinhold A.

2002-12-03

109

Field-scale operation of methane biofiltration systems to mitigate point source methane emissions.  

PubMed

Methane biofiltration (MBF) is a novel low-cost technique for reducing low volume point source emissions of methane (CH?). MBF uses a granular medium, such as soil or compost, to support the growth of methanotrophic bacteria responsible for converting CH? to carbon dioxide (CO?) and water (H?O). A field research program was undertaken to evaluate the potential to treat low volume point source engineered CH? emissions using an MBF at a natural gas monitoring station. A new comprehensive three-dimensional numerical model was developed incorporating advection-diffusive flow of gas, biological reactions and heat and moisture flow. The one-dimensional version of this model was used as a guiding tool for designing and operating the MBF. The long-term monitoring results of the field MBF are also presented. The field MBF operated with no control of precipitation, evaporation, and temperature, provided more than 80% of CH? oxidation throughout spring, summer, and fall seasons. The numerical model was able to predict the CH? oxidation behavior of the field MBF with high accuracy. The numerical model simulations are presented for estimating CH? oxidation efficiencies under various operating conditions, including different filter bed depths and CH? flux rates. The field observations as well as numerical model simulations indicated that the long-term performance of MBFs is strongly dependent on environmental factors, such as ambient temperature and precipitation. PMID:21414700

Hettiarachchi, Vijayamala C; Hettiaratchi, Patrick J; Mehrotra, Anil K; Kumar, Sunil

2011-06-01

110

Tropospheric impact of methane emissions from clathrates in the Arctic Region  

NASA Astrophysics Data System (ADS)

A highly potent greenhouse gas, methane, is locked in the solid phase as ice-like deposits containing a mixture of water and gas (mostly methane) called clathrates in both ocean sediments and underneath permafrost regions. Clathrates are stable under high pressures and low temperatures. In a warming climate, increases in ocean temperatures could lead to dissociation of the clathrates and release methane into the ocean and subsequently the atmosphere. This is of particular importance in the shallow parts of the Arctic Ocean, since clathrates are expected to start outgassing abruptly at depths of around 300 m. In this paper, we present a comparison of simulations from the Community Earth System Model (CESM1) for present-day conditions with and without additional methane emissions from a plausible clathrate release scenario based on a state-of-the-art ocean sediment model. The CESM model includes a fully interactive physical ocean and we added a fast atmospheric chemistry mechanism that represents methane as a fully interactive tracer (with emissions rather than concentration boundary conditions) along with the main chemical reactions for methane, ozone, and nitrous oxide. The results show that such Arctic clathrate emissions increase methane concentrations non-uniformly, and that increases in surface ozone concentrations are greatest in polluted regions. We also find that the interannual variability in surface methane and ozone increases.

Bhattacharyya, S.; Cameron-Smith, P.; Bergmann, D.; Reagan, M.; Elliott, S.; Moridis, G.

2012-10-01

111

Tropospheric impact of methane emissions from clathrates in the Arctic Region  

NASA Astrophysics Data System (ADS)

A highly potent greenhouse gas, methane, is locked in the solid phase as ice-like deposits containing a mixture of water and gas (mostly methane) called clathrates in both ocean sediments and underneath permafrost regions. Clathrates are stable under high pressures and low temperatures. In a warming climate, increases in ocean temperatures could lead to dissociation of the clathrates and release of methane into the ocean and subsequently into the atmosphere. This is of particular importance in the shallow part of the Arctic Ocean, where clathrates are expected to start outgassing abruptly at depths of around 300m. Here we present a comparison of simulations from the Community Earth System Model (CESM1) for present-day conditions with and without additional methane emissions from a plausible clathrate release scenario based on a state-of-the-art ocean sediment model. The model includes a fully interactive physical ocean and a fast atmospheric chemistry mechanism that represents methane as a fully interactive tracer (with emissions rather than concentration boundary conditions), along with the main chemical reactions for methane, ozone, and nitrous oxide. The results show that such clathrate emissions increase methane concentrations spatially non-uniformly, and that increases in surface ozone concentrations are greatest in polluted regions. We also find that the interannual variability in surface methane and ozone increases. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-570979

Bhattacharyya, S.; Cameron-Smith, P. J.; Bergmann, D.; Reagan, M. T.; Elliott, S. M.; Moridis, G. J.

2012-12-01

112

Methane Emission through Trees in Temperate and Tropical Wetlands  

NASA Astrophysics Data System (ADS)

Methane produced in wetland soil generally is thought to be emitted by a combination of three key processes: 1) diffusion through water-filled pores, 2) abrupt release of bubbles (ebullition), and 3) via internal spaces within the stems of herbaceous plants adapted to live in waterlogged soils. The capacity for trees to mediate methane emissions has received limited attention despite mesocosm studies of seedlings and saplings demonstrating that wetland trees have a significant capacity to transport soil-produced methane to the atmosphere. Notably ~60% of global wetlands are forested. We present in situ measurements of methane flux from a temperate carr (swamp) composed of alder (Alnus glutinosa) and birch (Betula pubescens) situated in the United Kingdom and a tropical forested peat swamp located in Borneo. The in situ data are complemented by a mesocosm experiment in which methane emissions were measured from alder saplings subjected to two water-regime treatments. In both the in situ and mesocosm studies, emissions from trees are compared to methane flux from the ground surface, the latter occurring via pore water diffusion, ebullition or via the aerenchyma of herbaceous plants. We show that tree stem emissions are controlled by a number of factors including tree species, soil pore-water concentration and stem lenticel density. Our results demonstrate that the omission of tree-mediated methane fluxes from measurement campaigns conducted in forested wetland can significantly underestimate the total ecosystem flux of methane.

Pangala, S. R.; Gauci, V.; Hornibrook, E. R.; Gowing, D.

2012-12-01

113

Future methane, hydroxyl, and their uncertainties: key climate and emission parameters for future predictions  

NASA Astrophysics Data System (ADS)

Accurate prediction of future methane abundances following a climate scenario requires understanding the lifetime changes driven by anthropogenic emissions, meteorological factors, and chemistry-climate feedbacks. Uncertainty in any of these influences or the underlying processes implies uncertainty in future abundance and radiative forcing. We simulate methane lifetime in three chemical transport models (CTMs) - UCI CTM, GEOS-Chem, and Oslo CTM3 - over the period 1997-2009 and compare the models' year-to-year variability against constraints from global methyl chloroform observations. Using sensitivity tests, we find that temperature, water vapor, stratospheric ozone column, biomass burning and lightning NOx are the dominant sources of interannual changes in methane lifetime in all three models. We also evaluate each model's response to forcings that have impacts on decadal time scales, such as methane feedback, and anthropogenic emissions. In general, these different CTMs show similar sensitivities to the driving variables. We construct a parametric model that reproduces most of the interannual variability of each CTM and use it to predict methane lifetime from 1980 through 2100 following a specified emissions and climate scenario (RCP 8.5). The parametric model propagates uncertainties through all steps and provides a foundation for predicting methane abundances in any climate scenario. Our sensitivity tests also enable a new estimate of the methane global warming potential (GWP), accounting for stratospheric ozone effects, including those mediated by water vapor. We estimate the 100-yr GWP to be 32, which is 25% larger than past assessments.

Holmes, C. D.; Prather, M. J.; Søvde, O. A.; Myhre, G.

2013-01-01

114

Three-dimensional model synthesis of the global methane cycle  

NASA Astrophysics Data System (ADS)

A synthesis of the global methane cycle is presented to attempt to generate an accurate global methane budget. Methane-flux measurements, energy data, and agricultural statistics are merged with databases of land-surface characteristics and anthropogenic activities. The sources and sinks of methane are estimated based on atmospheric methane composition and variations, and a global 3D transport model simulates the corresponding atmospheric responses. The geographic and seasonal variations of candidate budgets are compared with observational data, and the available observations are used to constrain the plausible methane budgets. The preferred budget includes annual destruction rates and annual emissions for various sources. The lack of direct flux measurements in the regions of many of these fluxes makes the unique determination of each term impossible. OH oxidation is found to be the largest single term, although more measurements of this and other terms are recommended.

Fung, I.; Prather, M.; John, J.; Lerner, J.; Matthews, E.

1991-07-01

115

Trace Gas Emissions Data from the Carbon Dioxide Information Analysis Center (CDIAC): Methane  

DOE Data Explorer

(Scroll down to find Methane, a subheading under the broader heading of Trace Gas Emissions) CDIAC products are indexed and searchable through a customized interface powered by ORNL's Mercury search engine. Products include numeric data packages, publications, trend data, atlases, models, etc. and can be searched for by subject area, keywords, authors, product numbers, time periods, collection sites, spatial references, etc. Some of the collections may also be included in the CDIAC publication Trends Online: A Compendium of Global Change Data. Most data sets, many with numerous data files, are free to download from CDIAC's ftp area. Information related to methane and other trace gas emissions includes: • Methane Emissions (Trends Online) • Annual Estimates of Global Anthropogenic Methane Emissions: 1860-1994, (1998) (Trends Online) • Global and Latitudinal Estimates of ? 13C from Fossil-Fuel Consumption and Cement Manufacture (1996) (Specialized Interface)

116

The influence of atmospheric pressure on landfill methane emissions.  

PubMed

Landfills are the largest source of anthropogenic methane (CH4) emissions to the atmosphere in the United States. However, few measurements of whole landfill CH4 emissions have been reported. Here, we present the results of a multi-season study of whole landfill CH4 emissions using atmospheric tracer methods at the Nashua, New Hampshire Municipal landfill in the northeastern United States. The measurement data include 12 individual emission tests, each test consisting of 5-8 plume measurements. Measured emissions were negatively correlated with surface atmospheric pressure and ranged from 7.3 to 26.5 m3 CH4 min(-1). A simple regression model of our results was used to calculate an annual emission rate of 8.4 x 10(6) m3 CH4 year(-1). These data, along with CH4 oxidation estimates based on emitted landfill gas isotopic characteristics and gas collection data, were used to estimate annual CH4 generation at this landfill. A reported gas collection rate of 7.1 x 10(6) m3 CH4 year(-1) and an estimated annual rate of CH4 oxidation by cover soils of 1.2 x 10(6) m3 CH4 year(-1) resulted in a calculated annual CH4 generation rate of 16.7 x 10(6) m3 CH4 year(-1). These results underscore the necessity of understanding a landfill's dynamic environment before assessing long-term emissions potential. PMID:12957154

Czepiel, P M; Shorter, J H; Mosher, B; Allwine, E; McManus, J B; Harriss, R C; Kolb, C E; Lamb, B K

2003-01-01

117

Future methane, hydroxyl, and their uncertainties: key climate and emission parameters for future predictions  

NASA Astrophysics Data System (ADS)

Accurate prediction of future methane abundances following a climate scenario requires understanding the lifetime changes driven by anthropogenic emissions, meteorological factors, and chemistry-climate feedbacks. Uncertainty in any of these influences or the underlying processes implies uncertainty in future abundance and radiative forcing. We simulate methane lifetime in multiple models over the period 1997-2009, adding sensitivity tests to determine key variables that drive the year-to-year variability. Across three atmospheric chemistry and transport models - UCI CTM, GEOS-Chem, and Oslo CTM3 - we find that temperature, water vapor, ozone column, biomass burning and lightning NOx are the dominant sources of interannual changes in methane lifetime. We also evaluate the model responses to forcings that have impacts on decadal time scales, such as methane feedback, and anthropogenic NOx emissions. In general, these different CTMs show similar sensitivities to the driving variables. We construct a parametric model that reproduces most of the interannual variability of each CTM and use it to predict methane lifetime from 1980 through 2100 following a specified emissions and climate scenario (RCP 8.5). The parametric model propagates uncertainties through all steps and provides a foundation for predicting methane abundances in any climate scenario. Our sensitivity tests also enable a new estimate of the methane global warming potential (GWP), accounting for stratospheric ozone effects, including those mediated by water vapor. We estimate the 100-yr GWP to be 32.

Holmes, C. D.; Prather, M. J.; Søvde, O. A.; Myhre, G.

2012-08-01

118

A multitower measurement network estimate of California's methane emissions  

NASA Astrophysics Data System (ADS)

present an analysis of methane (CH4) emissions using atmospheric observations from five sites in California's Central Valley across different seasons (September 2010 to June 2011). CH4 emissions for spatial regions and source sectors are estimated by comparing measured CH4 mixing ratios with transport model (Weather Research and Forecasting and Stochastic Time-Inverted Lagrangian Transport) predictions based on two 0.1° CH4 (seasonally varying "California-specific" (California Greenhouse Gas Emission Measurements, CALGEM) and a static global (Emission Database for Global Atmospheric Research, release version 42, EDGAR42)) prior emission models. Region-specific Bayesian analyses indicate that for California's Central Valley, the CALGEM- and EDGAR42-based inversions provide consistent annual total CH4 emissions (32.87 ± 2.09 versus 31.60 ± 2.17 Tg CO2eq yr-1; 68% confidence interval (CI), assuming uncorrelated errors between regions). Summing across all regions of California, optimized CH4 emissions are only marginally consistent between CALGEM- and EDGAR42-based inversions (48.35 ± 6.47 versus 64.97 ± 11.85 Tg CO2eq), because emissions from coastal urban regions (where landfill and natural gas emissions are much higher in EDGAR than CALGEM) are not strongly constrained by the measurements. Combining our results with those from a recent study of the South Coast Air Basin narrows the range of estimates to 43-57 Tg CO2eq yr-1 (1.3-1.8 times higher than the current state inventory). These results suggest that the combination of rural and urban measurements will be necessary to verify future changes in California's total CH4 emissions.

Jeong, Seongeun; Hsu, Ying-Kuang; Andrews, Arlyn E.; Bianco, Laura; Vaca, Patrick; Wilczak, James M.; Fischer, Marc L.

2013-10-01

119

Estimating Methane Emissions from Central California  

NASA Astrophysics Data System (ADS)

A three-month time series of continuous CH4 mixing ratio measurements obtained from a tall-tower are applied in an inverse model to estimate regional surface emissions of CH4 in Central California. Simulated CH4 mixing ratios are calculated based on spatially resolved a priori CH4 emission estimates and simulated atmospheric transport. Atmospheric transport and surface influences (footprints) are computed using the Stochastic Time-Inverted Lagrangian Transport (STILT) model driven by customized output from the Weather Research and Forecasting (WRF) model. An uncertainty analysis is performed that propagates measurement and model errors through the inverse model to provide quantitative uncertainties in the estimated CH4 emissions. WRF-STILT predictions of daytime planetary boundary layer (PBL) heights are found to be over-estimated by a factor of 1.33 ± 0.13 (1s) through comparison with PBL heights estimated from a wind profiler located near the tower site for October, 2007. The inverse model estimates of CH4 emissions are performed in three ways. First, geometric linear regressions of modeled and measured CH4 mixing ratios obtains slopes of 0.95 ± 0.14 and 1.12 ± 0.12 for the October and Oct.-Dec., 2007 periods respectively, suggesting that total a priori CH4 emissions estimates are consistent with the atmospheric measurements and the transport model. Second, a Baysian inverse analysis of the Oct.-Dec., 2007 period obtains posterior scaling factors for CH4 suggesting that landfills and crop agriculuture are lower and livestock and petroleum emissions are higher than a priori estimates respectively. Third, a Baysian analysis of uncertainty, using 13 spatial sub-regions as basis functions, shows that the CH4 measurements significantly reduce posterior uncertainties in CH4 emissions relative the a priori assumptions for only the three sub-regions nearest the tower site. This suggests that a regional network of measurement sites will be necessary to provide high-accuracy retrievals of surface CH4 emissions for multiple regions comprising California's CH4 emissions.

Zhao, C.; Fischer, M. L.; Andrews, A. E.; Eluszkiewicz, J.; MacDonald, C. P.; Nehrkorn, T.; Hirsch, A. I.

2008-12-01

120

Landfill methane emissions measured by enclosure and atmospheric tracer methods  

Microsoft Academic Search

Methane (CH4) emissions were measured from the Nashua, New Hampshire municipal landfill using static enclosure and atmospheric tracer methods. The spatial variability of emissions was also examined using geostatistical methods. One hundred and thirty nine enclosure measurements were performed on a regular grid pattern over the emitting surface of the landfill resulting in an estimate of whole landfill emissions of

P. M. Czepiel; B. Mosher; R. C. Harriss; J. H. Shorter; J. B. McManus; C. E. Kolb; E. Allwine; B. K. Lamb

1996-01-01

121

Annual Estimates of Global Anthropogenic Methane Emissions: 1860-1994  

NSDL National Science Digital Library

David Stern and Robert Kaufmann, of the Center for Energy and Environmental Studies at Boston University, provide "the first estimates," by year, of human-made methane emissions from seven sources, including gas flaring, coal mining, and biomass burning. Data are available in ASCII or binary spreadsheet formats, and a graph shows the rise in methane emissions from 1860 to 1994. The site explains Stern and Kaufmann's methods, including mathematical equations.

Kaufmann, Robert K.; Stern, David I.

1998-01-01

122

Inventory of methane emissions from U.S. cattle  

NASA Astrophysics Data System (ADS)

Many countries, including the United States, are in the process of inventorying greenhouse gas emissions as a prerequisite for designing control strategies. We have developed a measurement-based inventory of methane emissions from cattle in the United States. Methane emission factors were established for the major livestock groups using an internal tracer method. The groups studied included cows, replacement heifers, slaughter cattle, calves, and bulls in the beef sector and cows plus replacement heifers in the dairy industry. Since methane emission is dependent on the quality and quantity of feed, diets were chosen that are representative of the feed regimes utilized by producers in the United States. Regional cattle populations, obtained from U.S. Department of Agriculture statistics, were combined with the methane emission factors to yield regional emission estimates. The methane totals from the five regions were then summed to give a U.S. inventory of cattle emissions for 1990, 1992, 1994, 1996, and 1998. Annual releases ranged from 6.50 Tg in 1990 to a high of 6.98 Tg in 1996. On a regional scale the North Central region of the United States had the largest methane emissions from livestock followed by the South Central and the West. The beef cow group released the most methane (˜2.5 Tg yr-1) followed by slaughter cattle (˜1.7 Tg yr-1) and dairy cows at about 1.5 Tg yr-1. Methane released by cattle in the United States contributes about 11% of the global cattle source.

Westberg, H.; Lamb, B.; Johnson, K. A.; Huyler, M.

2001-01-01

123

Development of atmospheric tracer methods to measure methane emissions from natural gas facilities and urban areas  

Microsoft Academic Search

A new, integrated methodology to locate and measure methane emissions from natural gas systems has been developed. Atmospheric methane sources are identified by elevated ambient CHâ concentrations meaured with a mobile laser-based methane analyzer. The total methane emission rate from a source is obtained by simulating the source with a sulfur hexafluoride (SFâ) tracer gas release and by measuring methane

Brian Lamb; E. Allwine; R. Siverson; H. Westberg; J. B. McManus; C. B. Kolb; J. H. Shorter; B. Mosher; D. Blaha; R. C. Harris; Robert Lott; Hal Westburg; Pat Zimmerman

1995-01-01

124

Methane, microbes and models: fundamental understanding of the soil methane cycle for future predictions.  

PubMed

Methane is an important greenhouse gas and microbes in the environment play major roles in both global methane emissions and terrestrial sinks. However, a full mechanistic understanding of the response of the methane cycle to global change is lacking. Recent studies suggest that a number of biological and environmental processes can influence the net flux of methane from soils to the atmosphere but the magnitude and direction of their impact are still debated. Here, we synthesize recent knowledge on soil microbial and biogeochemical process and the impacts of climate change factors on the soil methane cycle. We focus on (i) identification of the source and magnitude of methane flux and the global factors that may change the flux rate and magnitude in the future, (ii) the microbial communities responsible for methane production and terrestrial sinks, and (iii) how they will respond to future climatic scenarios and the consequences for feedback responses at a global scale. We also identify the research gaps in each of the topics identified above, provide evidence which can be used to demonstrate microbial regulation of methane cycle and suggest that incorporation of microbial data from emerging -omic technologies could be harnessed to increase the predictive power of simulation models. PMID:23718889

Nazaries, Loïc; Murrell, J Colin; Millard, Pete; Baggs, Liz; Singh, Brajesh K

2013-09-01

125

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

NASA Technical Reports Server (NTRS)

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.

King, G. M.

1997-01-01

126

Methane emission by bubbling from Gatun Lake, Panama  

SciTech Connect

We studied methane emission by bubbling from Gatun Lake, Panama, at water depths of less than 1 m to about 10 m. Gas bubbles were collected in floating traps deployed during 12- to 60-hour observation periods. Comparison of floating traps and floating chambers showed that about 98% of methane emission occurred by bubbling and only 2% occurred by diffusion. Average methane concentration of bubbles at our sites varied from 67% to 77%. Methane emission by bubbling occurred episodically, with greatest rates primarily between the hours of 0800 and 1400 LT. Events appear to be triggered by wind. The flux of methane associated with bubbling was strongly anticorrelated with water depth. Seasonal changes in water depth caused seasonal variation of methane emission. Bubble methane fluxes through the lake surface into the atmosphere measured during 24-hour intervals were least (10-200 mg m{sup -2} d{sup -1}) at deeper sites (>7 m) and greatest (300-2000 mg m{sup -2} d{sup -1}) at shallow sites (<2 m). 37 refs., 11 figs., 5 tabs.

Keller, M. [National Center for Atmospheric Research, Boulder, CO (United States)] [National Center for Atmospheric Research, Boulder, CO (United States); Stallard, R.F. [Geological Survey, Denver, CO (United States)] [Geological Survey, Denver, CO (United States)

1994-04-20

127

Methane emission by bubbling from Gatun Lake, Panama  

NASA Technical Reports Server (NTRS)

We studied methane emission by bubbling from Gatun Lake, Panama, at water depths of less than 1 m to about 10 m. Gas bubbles were collected in floating traps deployed during 12- to 60-hour observation periods. Comparison of floating traps and floating chambers showed that about 98% of methane emission occurred by bubbling and only 2% occurred by diffusion. Average methane concentration of bubbles at our sites varied from 67% to 77%. Methane emission by bubbling occurred episodically, with greatest rates primarily between the hours of 0800 and 1400 LT. Events appear to be triggered by wind. The flux of methane associated with bubbling was strongly anticorrelated with water depth. Seasonal changes in water depth caused seasonal variation of methane emission. Bubble methane fluxes through the lake surface into the atmosphere measured during 24-hour intervals were least (10-200 mg/m2/d) at deeper sites (greater than 7 m) and greatest (300-2000 mg/m2/d) at shallow sites (less than 2 m).

Keller, Michael; Stallard, Robert F.

1994-01-01

128

Observational constraints on the distribution, seasonality, and environmental predictors of North American boreal methane emissions  

NASA Astrophysics Data System (ADS)

Wetlands comprise the single largest global source of atmospheric methane, but current flux estimates disagree in both magnitude and distribution at the continental scale. This study uses atmospheric methane observations over North America from 2007 to 2008 and a geostatistical inverse model to improve understanding of Canadian methane fluxes and associated biogeochemical models. The results bridge an existing gap between traditional top-down, inversion studies, which typically emphasize total emission budgets, and biogeochemical models, which usually emphasize environmental processes. The conclusions of this study are threefold. First, the most complete process-based methane models do not always describe available atmospheric methane observations better than simple models. In this study, a relatively simple model of wetland distribution, soil moisture, and soil temperature outperformed more complex model formulations. Second, we find that wetland methane fluxes have a broader spatial distribution across western Canada and into the northern U.S. than represented in existing flux models. Finally, we calculate total methane budgets for Canada and for the Hudson Bay Lowlands, a large wetland region (50-60°N, 75-96°W). Over these lowlands, we find total methane fluxes of 1.8±0.24 Tg C yr-1, a number in the midrange of previous estimates. Our total Canadian methane budget of 16.0±1.2 Tg C yr-1 is larger than existing inventories, primarily due to high anthropogenic emissions in Alberta. However, methane observations are sparse in western Canada, and additional measurements over Alberta will constrain anthropogenic sources in that province with greater confidence.

Miller, Scot M.; Worthy, Doug E. J.; Michalak, Anna M.; Wofsy, Steven C.; Kort, Eric A.; Havice, Talya C.; Andrews, Arlyn E.; Dlugokencky, Edward J.; Kaplan, Jed O.; Levi, Patricia J.; Tian, Hanqin; Zhang, Bowen

2014-02-01

129

Future methane, OH, and their uncertainties: parametric relations with emissions and climate change  

NASA Astrophysics Data System (ADS)

Methane and hydrofluorocarbons (HFCs) are chemically reactive greenhouse gases whose future atmospheric abundances will change as a result of socioeconomic and climate forces. Accurate projections of these climate forcing agents requires knowing the sensitivity of their abundances to emissions, meteorological factors, and chemical feedbacks. Uncertainties in each of these processes implies uncertainty in future methane and HFC abundances and their radiative forcing. We conduct simulations of methane lifetime over the last 15 years in several atmospheric chemistry and transport models (CTMs) and use sensitivity tests to determine the key processes controlling interannual variability in these models. Across several CTMs (UCI CTM, GEOS-Chem, Oslo CTM3) we find that temperature, water vapor, biomass burning, and lightning NOx are the dominant sources of year-to-year changes in methane lifetime. We also evaluate the model responses to forcings that change on slower time scales, such as methane feedback, and anthropogenic emissions magnitude and location. From the range of CTM responses, we construct a parametric model for future methane and OH that includes their uncertainties. We show that this simple parametric model is consistent with the ensemble spread from the Atmospheric Chemistry and Climate Modeling Intercomparison Project (ACC-MIP). This parametric model provides a foundation for methane and HFCs along multiple socioeconomic and climate trajectories.

Holmes, C. D.; Prather, M. J.; Mu, M.; Isaksen, I. S. A.; Sovde, O. A.

2012-04-01

130

Interannual variation of methane emissions in a boreal peatland - cross-evaluation of chamber measurements (7 years) and model results (LPJ-WHyMe)  

NASA Astrophysics Data System (ADS)

Boreal peatlands are a major natural source of methane (CH4). Due to a lack of longterm measurements, the interannual variability of CH4 emission is still uncertain. To fill this gap, a combination of measurements and models is necessary. Here, we present chamber measurements of 7 years from a boreal mire in Finland and compare them with the output of a methane model that is integrated into a dynamic global vegetation model (LPJ-WHyMe: Wania et al. 2010). The mire is characterized by three microsite types which vary in vegetation cover and hydrology (hummocks, lawns, flarks). Chamber measurements have been conducted on all three microsite types in 1993 (Saarnio et al. 1997) and 2005-2007 (Becker et al. 2008, Schäfer 2007, Forbrich et al., in prep.), while in 1996-1998 they have been conducted exclusively on lawns (Saarnio et al. 2000). When all microsite types were measured, we upscale these measurements using classified high-aerial photographs (Becker et al. 2008). Additionally, we analyze the time series of measurements on lawns, which represent the most dominant CH4 source in the peatland (contributing on average 80% to the ecosystem flux: Forbrich et al., in prep.). LPJ-WHyMe has been applied for the grid cell containing the peatland for the years 1988-2008 using the settings of Wania et al. (2010). The upscaled chamber measurements (ecosystem flux estimate) for 1993 and 2005-2007 are generally lower than the model estimates (7-52%). Reasons for the mismatch can be both caused by the measurements and the model: Chamber measurements do miss ebullition fluxes (contributing 68.2% to the modelled annual emission: Wania et al. 2010) and/or the linear flux calculation underestimates the actual flux (Forbrich et al. 2010) while LPJ-WHyMe tends to overestimate the available carbon pool (Wania et al. 2009). Absolute values of observations of lawns in 1993 are well matched by model results (Wania et al. 2010). However, for the other years the model output is substantially larger than the measured fluxes (54-89%). This mismatch is decreasing when ebullition fluxes are neglected. To analyze this mismatch we will conduct an uncertainty analysis of the upscaling procedure of measurements and test different parameter settings. The interannual variability of measured CH4 fluxes can best be explained by the varying hydrology (Schäfer 2007): When the water table is low during the growing season, the measured fluxes decrease while they follow a seasonal curve when the water table is relatively stable over time. This is not exactly matched by LPJ-WHyMe, although generally the modelled mean water table matches very well the measured mean water table of lawns. Only the modelled diffusion fluxes seem to be affected by the water table position, while modelled emissions due to plant-mediated transport stay relatively stable for the investigated years. Modelled ebullition fluxes show a high variability: The amount of days when ebullition fluxes are modelled to take place range from 89 (2006) to 141 (2005 and 2007). References: Becker et al. 2008, Biogeosciences, 5:1387-1393 Forbrich et al., 2010, Soil Biology and Biochemistry, in press Saarnio et al. 1997, Oecologia, 110:414-422 Saarnio et al. 2000, Global Change Biology, 6: 137-144 Schäfer 2007, diploma thesis, University of Greifswald Wania et al. 2009, Global Biogeochemical Cycles, 23, 3, doi:10.1029/2008GB003413 Wania et al. 2010, Geoscientific Model Development Discussions, 3:1-59

Forbrich, Inke; Wania, Rita; Saarnio, Sanna; Schäfer, Carolyn; Kutzbach, Lars; Wilmking, Martin

2010-05-01

131

Sensitivity of detection of fugitive methane emissions from coal seam gas fields  

NASA Astrophysics Data System (ADS)

There is increasing recognition that minimising methane emissions from the oil and gas sector is a key step in reducing global greenhouse gas emissions in the near term. Atmospheric monitoring techniques are likely to play an important future role in measuring the extent of existing emissions and verifying emission reductions. They can be very suitable for monitoring gas fields as they are continuous and integrate emissions from a number of potential point and diffuse sources that may vary in time. Geoscience Australia and CSIRO Marine & Atmospheric Research have collected three years of continuous methane and carbon dioxide measurements at their atmospheric composition monitoring station ('Arcturus') in the Bowen Basin, Australia. Methane signals in the Bowen Basin are likely to be influenced by cattle production, landfill, coal production, and conventional and coal seam gas (CSG) production. Australian CSG is typically 'dry' and is characterised by a mixed thermogenic-biogenic methane source with an absence of C3-C6+ alkanes. The range of ?13C isotopic signatures of the CSG is similar to methane from landfill gas and cattle emissions. The absence of standard in-situ tracers for CSG fugitive emissions suggests that having a comprehensive baseline will be critical for successful measurement of fugitive emissions using atmospheric techniques. In this paper we report on the sensitivity of atmospheric techniques for the detection of fugitive emissions from a simulated new CSG field against a three year baseline signal. Simulation of emissions was performed for a 1-year period using the coupled prognostic meteorological and air pollution model TAPM at different fugitive emission rates (i.e. estimates of <1% to up to 10% of production lost) and distances (i.e. 10 - 50 km) from the station. Emissions from the simulated CSG field are based on well density, production volumes, and field size typical of CSG fields in Australia. The distributions of the perturbed and baseline signals were evaluated and statistically compared to test for the presence of fugitive methane emissions. In addition, a time series model of the methane baseline was developed in order to generate alternative realizations of the baseline signal. These were used to provide measures of both the likelihood of detecting fugitive emissions at various emission levels and of the false alarm rate. Results of the statistical analysis and an indicative minimum fugitive methane emission rate that can be detected using a single monitoring station are presented.

Feitz, A. J.; Berko, H.; Wilson, P.; Jenkins, C.; Loh, Z. M.; Etheridge, D.

2013-12-01

132

Future methane, tropospheric ozone, and their uncertainties: parametric relationships with emissions and climate change  

NASA Astrophysics Data System (ADS)

Methane and ozone are chemically reactive greenhouse gases whose future abundances will change as a result of socioeconomic and climate forces. Accurate projections of these climate forcing agents requires knowing the sensitivity of their abundances to emissions, meteorological factors, and chemical feedbacks. Uncertainties in each of these processes implies uncertainty in future methane and ozone abundances and their radiative forcings. We analyze the sensitivity of methane lifetime and tropospheric ozone to key processes in atmospheric chemistry models (CTMs), including convection, anthropogenic and lightning NOx emissions, humidity, and interannual meteorological variability. We evaluate the consistency of each sensitivity across several CTMs (UCI CTM, GEOS-Chem, and Oslo CTM2), and to the ensemble spread from the Atmospheric Chemistry and Climate Modeling Intercomparison Project (ACC-MIP). From these results, we construct a parametric model for projecting future methane and tropospheric ozone abundances and their uncertainties along multiple socioeconomic and climate trajectories.

Holmes, C. D.; Prather, M. J.

2011-12-01

133

METHANE EMISSIONS FROM THE NATURAL GAS INDUSTRY: PRODUCTION AND TRANSMISSION EMISSIONS  

EPA Science Inventory

The paper discusses a co-funded, Gas Research Institute/EPA project to quantify methane emissions to the atmosphere resulting from operations in the natural gas industry. tudy results will measure or calculate all methane emissions, from production at the well and up to, but not ...

134

Methane Emissions from the U.S. Petroleum Industry.  

National Technical Information Service (NTIS)

The report quantifies methane (CH4) emissions from the U.S. petroleum inustry by identifying sources of CH4 from the production, transportation, and refining of oil. Emissions are reported for the base year 1993 and for the years 1986 through 1992, based ...

M. R. Harrison T. M. Shires R. A. Baker C. J. Loughran

1999-01-01

135

Methane in the Baltic and North Seas and a reassessment of the marine emissions of methane  

Microsoft Academic Search

During three measurement campaigns on the Baltic and North Seas, atmospheric and dissolved methane was determined with an automated gas chromatographic system. Area-weighted mean saturation values in the sea surface waters were 113{+-}5% and 395{+-}82% and 126{+-}8%. On the bases of our data and a compilation of literature data the global oceanic emissions of methane were reassessed by introducing a

H. W. Bange; U. H. Bartell; S. Rapsomanikis; M. O. Andreae

1994-01-01

136

MICROBIAL ECOLOGY OF METHANE EMISSION IN RICE AGROECOSYSTEM: A REVIEW  

Microsoft Academic Search

Methane has profound impact on the physico-chemical properties in atmosphere leading to global climate change. Out of the various sources of CH4, rice fields are the most significant contributors. The processes involved in the emission of CH4 from rice fields to the atmosphere include CH4 production (methanogenesis) in the soil by methanogens, methane oxidation (methanotrophy) by methanotrophs and vertical transfer

S. K. DUBEY

2005-01-01

137

Direct measurements of methane emissions from grazing and feedlot cattle.  

PubMed

Methane (CH4) emissions from animals represent a significant contribution to anthropogenically produced radiatively active trace gases. Global and national CH4 budgets currently use predictive models based on emission data from laboratory experiments to estimate the magnitude of the animal source. This paper presents a method for measuring CH4 from animals under undisturbed field conditions and examines the performance of common models used to simulate field conditions. A micrometeorological mass difference technique was developed to measure CH4 production by cattle in pasture and feedlot conditions. Measurements were made continuously under field conditions, semiautomatically for several days, and the technique was virtually nonintrusive. The method permits a relatively large number of cattle to be sampled. Limitations include light winds (less than approximately 2 m/s), rapid wind direction changes, and high-precision CH4 gas concentration measurement. Methane production showed a marked periodicity, with greater emissions during periods of rumination as opposed to grazing. When the cattle were grazed on pasture, they produced .23 kg CH4 x animal(-1) x d(-1), which corresponded to the conversion of 7.7 to 8.4% of gross energy into CH4. When the same cattle were fed a highly digestible, high-grain diet, they produced .07 kg CH4 x animal(-1) x d(-1), corresponding to a conversion of only 1.9 to 2.2% of the feed energy to CH4. These measurements clearly document higher CH4 production (about four times) for cattle receiving low-quality, high-fiber diets than for cattle fed high-grain diets. The mass difference method provides a useful tool for "undisturbed" measurements on the influence of feedstuffs and nutritional management practices on CH4 production from animals and for developing improved management practice for enhanced environmental quality. PMID:10375217

Harper, L A; Denmead, O T; Freney, J R; Byers, F M

1999-06-01

138

[Estimating spatiotemporal dynamics of methane emissions from livestock in China].  

PubMed

Combining Tier 2 method presented in the guidelines of the Intergovernmental Panel on Climate Change (IPCC, 2006) with GIS techniques, a primary estimation of methane emission from livestock in 2004 (including emission from enteric fermentation and manure management system) was made with county-level livestock statistics and 1 km x 1 km raster data. The results indicated that the methane emission from livestock was 12.79 x 10(6) tons totally in China, and 11.64 x 10(6) tons from enteric fermentation and 1.16 x 10(6) tons from manure management. The uncertainties of the methane emission from enteric fermentation and manure management were +/- 35.10% and +/- 14. 58% respectively. The high methane emission was at Yellow River basin, especially in the lower reaches of the Yellow River and the North China Plain. The Southwestern China also can be found with high emission. In accordance with the seasonal temperature changes, the temporal variation of manure management emission was estimated the highest in summer and the lowest in winter. PMID:22619939

Lin, Yu; Zhang, Wen; Huang, Yao

2011-08-01

139

Emissions of organic carbon and methane from petroleum and dairy operations in California's San Joaquin Valley  

NASA Astrophysics Data System (ADS)

Petroleum and dairy operations are prominent sources of gas-phase organic compounds in California's San Joaquin Valley. It is essential to understand the emissions and air quality impacts of these relatively understudied sources, especially for oil/gas operations in light of increasing US production. Ground site measurements in Bakersfield and regional aircraft measurements of reactive gas-phase organic compounds and methane were part of the CalNex (California Research at the Nexus of Air Quality and Climate Change) project to determine the sources contributing to regional gas-phase organic carbon emissions. Using a combination of near-source and downwind data, we assess the composition and magnitude of emissions, and provide average source profiles. To examine the spatial distribution of emissions in the San Joaquin Valley, we developed a statistical modeling method using ground-based data and the FLEXPART-WRF transport and meteorological model. We present evidence for large sources of paraffinic hydrocarbons from petroleum operations and oxygenated compounds from dairy (and other cattle) operations. In addition to the small straight-chain alkanes typically associated with petroleum operations, we observed a wide range of branched and cyclic alkanes, most of which have limited previous in situ measurements or characterization in petroleum operation emissions. Observed dairy emissions were dominated by ethanol, methanol, acetic acid, and methane. Dairy operations were responsible for the vast majority of methane emissions in the San Joaquin Valley; observations of methane were well correlated with non-vehicular ethanol, and multiple assessments of the spatial distribution of emissions in the San Joaquin Valley highlight the dominance of dairy operations for methane emissions. The petroleum operations source profile was developed using the composition of non-methane hydrocarbons in unrefined natural gas associated with crude oil. The observed source profile is consistent with fugitive emissions of condensate during storage or processing of associated gas following extraction and methane separation. Aircraft observations of concentration hotspots near oil wells and dairies are consistent with the statistical source footprint determined via our FLEXPART-WRF-based modeling method and ground-based data. We quantitatively compared our observations at Bakersfield to the California Air Resources Board emission inventory and find consistency for relative emission rates of reactive organic gases between the aforementioned sources and motor vehicles in the region. We estimate that petroleum and dairy operations each comprised 22% of anthropogenic non-methane organic carbon at Bakersfield and were each responsible for 8-13% of potential precursors to ozone. Yet, their direct impacts as potential secondary organic aerosol (SOA) precursors were estimated to be minor for the source profiles observed in the San Joaquin Valley.

Gentner, D. R.; Ford, T. B.; Guha, A.; Boulanger, K.; Brioude, J.; Angevine, W. M.; de Gouw, J. A.; Warneke, C.; Gilman, J. B.; Ryerson, T. B.; Peischl, J.; Meinardi, S.; Blake, D. R.; Atlas, E.; Lonneman, W. A.; Kleindienst, T. E.; Beaver, M. R.; St. Clair, J. M.; Wennberg, P. O.; VandenBoer, T. C.; Markovic, M. Z.; Murphy, J. G.; Harley, R. A.; Goldstein, A. H.

2014-05-01

140

The influence of atmospheric pressure on landfill methane emissions  

SciTech Connect

Landfills are the largest source of anthropogenic methane (CH{sub 4}) emissions to the atmosphere in the United States. However, few measurements of whole landfill CH{sub 4} emissions have been reported. Here, we present the results of a multi-season study of whole landfill CH{sub 4} emissions using atmospheric tracer methods at the Nashua, New Hampshire Municipal landfill in the northeastern United States. The measurement data include 12 individual emission tests, each test consisting of 5-8 plume measurements. Measured emissions were negatively correlated with surface atmospheric pressure and ranged from 7.3 to 26.5 m{sup 3} CH{sub 4} min{sup -1}. A simple regression model of our results was used to calculate an annual emission rate of 8.4x10{sup 6} m{sup 3} CH{sub 4} year{sup -1}. These data, along with CH{sub 4} oxidation estimates based on emitted landfill gas isotopic characteristics and gas collection data, were used to estimate annual CH{sub 4} generation at this landfill. A reported gas collection rate of 7.1x10{sup 6} m{sup 3} CH{sub 4} year{sup -1} and an estimated annual rate of CH{sub 4} oxidation by cover soils of 1.2x10{sup 6} m{sup 3} CH{sub 4} year{sup -1} resulted in a calculated annual CH{sub 4} generation rate of 16.7x10{sup 6} m{sup 3} CH{sub 4} year{sup -1}. These results underscore the necessity of understanding a landfill's dynamic environment before assessing long-term emissions potential.

Czepiel, P.M.; Shorter, J.H.; Mosher, B.; Allwine, E.; McManus, J.B.; Harriss, R.C.; Kolb, C.E.; Lamb, B.K

2003-07-01

141

Estimate of methane emissions from the U.S. natural gas industry  

Microsoft Academic Search

Global methane emissions from the fossil fuel industries have been poorly quantified and, in many cases, emissions are not well-known even at the country level. Historically, methane emissions from the U.S. gas industry have been based on sparse data, incorrect assumptions, or both. As a result, the estimate of the contribution these emissions make to the global methane inventory could

David A. Kirchgessner; Robert A. Lott; R. Michael Cowgill; Matthew R. Harrison; Theresa M. Shires

1997-01-01

142

Methane emissions measured directly from grazing livestock in New Zealand  

NASA Astrophysics Data System (ADS)

We report measurements of methane emissions from individual ruminant livestock-both sheep and dairy cows-grazing pasture typical of New Zealand lowlands in the temperate southwest Pacific. These are the first measurements reported from grazing sheep, and among the first from grazing cattle. The measurement technique, developed at Washington State University, enables emission rates to be determined from analyses of "breath" samples collected while grazing. More than 250 measurements of daily methane emission from 50 sheep (8 months old) were made, with flock-mean emission 18.9 ± 0.8 g hd -1 d -1. Although emissions were weakly correlated with feed intake, they represented a 4.6 ± 0.1 % average loss of gross dietary energy. The corresponding mean emission based on 40 measurements of daily emissions from 10 lactating dairy cows was 263 ± 10 g hd -1 d -1, approximately 6.2% of estimated gross energy intake. A notable feature was the large inter-sheep variability in daily methane emission (factor of 1.4 range) that could not be attributed to variable intake. This would appear to suggest an appreciable diversity of methanogenetic response to digestion, and may be significant in the search for strategies to control emissions of this greenhouse gas.

Lassey, Keith R.; Ulyatt, Marcus J.; Martin, Ross J.; Walker, Carolyn F.; David Shelton, I.

143

Methane emissions from a dairy feedlot during the fall and winter seasons in Northern China.  

PubMed

Accurately determining methane emission factors of dairy herd in China is imperative because of China's large population of dairy cattle. An inverse dispersion technique in conjunction with open-path lasers was used to quantify methane emissions from a dairy feedlot during the fall and winter seasons in 2009-2010. The methane emissions had a significant diurnal pattern during both periods with three emission peaks corresponding to the feeding schedule. A 10% greater emission rate in the fall season was obtained most likely by the higher methane emission from manure during that period. An annual methane emission rate of 109±6.7 kg CH4 yr(-1) characterized with a methane emission intensity of 32.3±1.59 L CH4 L(-1) of milk and a methane conversion factor (Ym) of 7.3±0.38% for mature cattle was obtained, indicating the high methane emission intensity and low milk productivity in Northern China. PMID:21354680

Gao, Zhiling; Yuan, Huijun; Ma, Wenqi; Liu, Xuejun; Desjardins, R L

2011-05-01

144

Climate Feedback on Methane Emissions From Terrestrial Ecosystems  

NASA Astrophysics Data System (ADS)

Terrestrial ecosystems are one of the important components of the climate system that are bound to change and cause feedbacks with global warming. One major mechanism of this feedback is the response of biological processes, mostly bacteria, that produce or consume greenhouse gases such as carbon dioxide (CO2) and methane (CH4). Here we are concerned with the emissions of CH4 which is considered the most important non-CO2 greenhouse gas because it has more than doubled during the last century and is about 20 times more potent per kilogram once emitted to the atmosphere. Methane is produced by anaerobic methanogens in wetland soils and rice paddies, and is consumed by methanotrophic bacteria in aerobic and upland soils. Together these sources account for about 40-60% of global methane emissions. Properly accounting for the feedback of CH4 emissions with temperature in Earth Systems Models (ESMs) remains an open challenge in part due to the lack of experimental data. Reported Q10 values (factor by which reaction rate increases for a 10°C rise in temperature) of CH4 flux from wetlands and rice agriculture vary over an order of magnitude for reasons that are not well known contributing to this uncertainty. We report here a suite of experimental measurements to determine the Q10 of CH4 flux from rice agriculture and to understand how it depends on the temperature responses of its underlying processes. Since processes may have different Q10 values it is essential that these are properly represented in ESMs. We grew rice plants in temperature-controlled mesocosms at 20, 24, 28 and 32°C over two seasons (years 2009 - 2010) and measured flux, production and oxidation rates, at regular intervals using static chambers, soil core incubations, and carbon isotopes (?13C-CH4), respectively. In addition we used qPCR techniques to measure methyl coenzyme M reductase (mcrA) and particulate methane monooxygenase (pmoA) genes from mesocosm soil cores to establish the temperature response of methanogen and methanotroph populations. We used a simple box model to relate the flux Q10 with the Q10 values for production, oxidation, and plant-mediated transport. Among other results, we found that flux Q10 values varied between 1 and 20 on a day-to-day basis throughout the growing season, with the largest values occurring at the beginning of the season when fluxes were low. This variation could in part be explained by differences in rates of plant-mediated transport brought about by the different plant growth rates at different temperatures. The seasonally-averaged flux Q10 was ~2, which was lower than the average production Q10 of ~3, indicating that the temperature response of CH4 oxidation in part offsets the increased emissions expected from enhanced production at higher temperatures. This has important implications for how CH4 emissions from terrestrial ecosystems will respond to global warming.

Butenhoff, C. L.; Sithole, A.; Khalil, A. K.; Rice, A. L.; Shearer, M. J.

2012-12-01

145

Emissions of organic carbon and methane from petroleum and dairy operations in California's San Joaquin Valley  

NASA Astrophysics Data System (ADS)

Petroleum and dairy operations are prominent sources of gas-phase organic compounds in California's San Joaquin Valley. Ground site measurements in Bakersfield and aircraft measurements of reactive gas-phase organic compounds were made in this region as part of the CalNex (California Research at the Nexus of Air Quality and Climate Change) project to determine the sources contributing to regional gas-phase organic carbon emissions. Using a combination of near-source and downwind data, we assess the composition and magnitude of emissions from these prominent sources that are relatively understudied compared to motor vehicles We also developed a statistical modeling method with the FLEXPART-WRF transport and meteorological model using ground-based data to assess the spatial distribution of emissions in the San Joaquin Valley. We present evidence for large sources of paraffinic hydrocarbons from petroleum extraction/processing operations and oxygenated compounds from dairy (and other cattle) operations. In addition to the small straight-chain alkanes typically associated with petroleum operations, we observed a wide range of branched and cyclic alkanes that have limited previous in situ measurements or characterization in emissions from petroleum operations. Observed dairy emissions were dominated by ethanol, methanol, and acetic acid, and methane. Dairy operations were responsible for the vast majority of methane emissions in the San Joaquin Valley; observations of methane were well-correlated with non-vehicular ethanol, and multiple assessments of the spatial distribution of emissions in the San Joaquin Valley highlight the dominance of dairy operations for methane emissions. The good agreement of the observed petroleum operations source profile with the measured composition of non-methane hydrocarbons in unrefined natural gas associated with crude oil suggests a fugitive emissions pathway during petroleum extraction, storage, or processing with negligible coincident methane emissions Aircraft observations of emission hotspots from operations at oil wells and dairies are consistent with the statistical source footprint determined via transport modeling and ground-based data. At Bakersfield, petroleum and dairy operations each comprised 22-23% of anthropogenic non-methane organic carbon and were each responsible for ~12% of potential precursors to ozone, but their direct impacts as potential SOA precursors were estimated to be minor. A comparison with the California Air Resources Board emission inventory supports the current relative emission rates of reactive organic gases from these sources in the region.

Gentner, D. R.; Ford, T. B.; Guha, A.; Boulanger, K.; Brioude, J.; Angevine, W. M.; de Gouw, J. A.; Warneke, C.; Gilman, J. B.; Ryerson, T. B.; Peischl, J.; Meinardi, S.; Blake, D. R.; Atlas, E.; Lonneman, W. A.; Kleindienst, T. E.; Beaver, M. R.; St. Clair, J. M.; Wennberg, P. O.; VandenBoer, T. C.; Markovic, M. Z.; Murphy, J. G.; Harley, R. A.; Goldstein, A. H.

2013-10-01

146

A new approach to estimation of methane emission rates from landfills.  

PubMed

Methane emission monitoring has become increasingly essential for diffusive area sources, especially for landfills, which contribute to a significant fraction of the total anthropogenic methane emission globally. Statutorily, methane emission rate from landfills in Germany shall be examined on a semiannual basis; however, an appropriate approach has yet to be developed and adopted for general use. In this study, a new method is proposed based on experimental results, which utilizes a TDLAS (Tunable Diode Laser Absorption Spectroscopy) instrument - GasFinder2.0 system and a dispersion model LASAT (Lagrangian Simulation of Aerosol Transport) as the measurement device and calculation model, respectively. Between April 2010 and December 2011, a research project was conducted at a pilot scale landfill in the south of Germany. Drawing on the extensive research into this pilot project, an effective strategy of measurement setup was determined. Methane concentration was measured with GasFinder2.0 system in the upstream and downstream sections of the project site, while wind and turbulence data were measured simultaneously by an ultrasonic anemometer. The average methane emission rate from the source can be calculated by using the results as input data in the dispersion model. With this method, site-specific measurement approaches can be designed for not only landfills, but also different diffusive area sources with less workload and lower cost compared to conventional FID (Flame Ionization Detector) method. PMID:24084101

Zhu, Han; Letzel, Marcus O; Reiser, Martin; Kranert, Martin; Bächlin, Wolfgang; Flassak, Thomas

2013-12-01

147

Carbon dioxide and methane emissions from the Yukon River system  

NASA Astrophysics Data System (ADS)

Carbon dioxide (CO2) and methane (CH4) emissions are important, but poorly quantified, components of riverine carbon (C) budgets. This is largely because the data needed for gas flux calculations are sparse and are spatially and temporally variable. Additionally, the importance of C gas emissions relative to lateral C exports is not well known because gaseous and aqueous fluxes are not commonly measured on the same rivers. We couple measurements of aqueous CO2 and CH4 partial pressures (pCO2, pCH4) and flux across the water-air interface with gas transfer models to calculate subbasin distributions of gas flux density. We then combine those flux densities with remote and direct observations of stream and river water surface area and ice duration, to calculate C gas emissions from flowing waters throughout the Yukon River basin. CO2 emissions were 7.68 Tg C yr-1 (95% CI: 5.84 -10.46), averaging 750 g C m-2 yr-1 normalized to water surface area, and 9.0 g C m-2 yr-1 normalized to river basin area. River CH4 emissions totaled 55 Gg C yr-1 or 0.7% of the total mass of C emitted as CO2 plus CH4 and ˜6.4% of their combined radiative forcing. When combined with lateral inorganic plus organic C exports to below head of tide, C gas emissions comprised 50% of total C exported by the Yukon River and its tributaries. River CO2 and CH4 derive from multiple sources, including groundwater, surface water runoff, carbonate equilibrium reactions, and benthic and water column microbial processing of organic C. The exact role of each of these processes is not yet quantified in the overall river C budget.

Striegl, Robert G.; Dornblaser, M. M.; McDonald, C. P.; Rover, J. R.; Stets, E. G.

2012-12-01

148

Magnitude and Seasonality of Wetland Methane Emissions from the Hudson Bay Lowlands (Canada)  

NASA Technical Reports Server (NTRS)

The Hudson Bay Lowlands (HBL) is the second largest boreal wetland ecosystem in the world and an important natural source of global atmospheric methane. We quantify the HBL methane emissions by using the GEOS-Chem chemical transport model to simulate aircraft measurements over the HBL from the ARCTAS and pre-HIPPO campaigns in May-July 2008, together with continuous 2004-2008 surface observations at Fraserdale (southern edge of HBL) and Alert (Arctic background). The difference in methane concentrations between Fraserdale and Alert is shown to be a good indicator of HBL emissions, and implies a sharp seasonal onset of emissions in late May (consistent with the aircraft data), a peak in July-August, and a seasonal shut-off in September. The model, in which seasonal variation of emission is mainly driven by surface temperature, reproduces well the observations in summer but its seasonal shoulders are too broad. We suggest that this reflects the suppression of emissions by snow cover and greatly improve the model simulation by accounting for this effect. Our resulting best estimate for HBL methane emissions is 2.3 Tg/a, several-fold higher than previous estimates (Roulet et al., 1994; Worthy et al., 2000).

Pickett-Heaps, C. A.; Jacob, D. J.; Wecht, K. J.; Kort, E. A.; Wofsy, S. C.; Diskin, G. S.; Worthy, D. E. J.; Kaplan, J. O.; Bey, I.; Drevet, J.

2011-01-01

149

Methane emissions from wetlands, southern Hudson Bay lowland  

SciTech Connect

This article describes the monitoring of methane emissions at 39 wetland ecosystem sites in the Hudson Bay Lowland. The study sites were located along a transect from the James Bay Coast at the tip of the Hudson Bay to Kinosheo Lake near Moosonee, Ontario, Canada. Measurements of methane flux were made using a static chamber technique. Weak statistical relationships were noted at each site between the daily methane flux rate, ground-water depth, and peat temperatures. On a regional scale, a significant correlation was noted over the complete range of sites between the seasonal methane flux and the average position of the ground-water table. Other observations are also described. 51 refs., 7 figs., 4 tabs.

Moore, T.R.; Heyes, A. [McGill Univ., Montreal (Canada)] [McGill Univ., Montreal (Canada); Roulet, N.T. [York Univ., Ontario (Canada)] [York Univ., Ontario (Canada)

1994-01-20

150

Spatial variability in methane emissions from a Texas rice field with some general implications  

NASA Astrophysics Data System (ADS)

This study addresses the issue of the effect of spatial variability within a single rice field on methane emissions observed using static flux boxes. The experimental data were collected from a commercially farmed field located near Richmond, Texas. The field was managed according to the normal practice of the area, including continuous flooding and the use of only inorganic fertilizer. Twenty-four experimental plots were employed to measure daily and seasonal methane emission, seasonal aboveground biomass, and soil texture. A statistical analysis of the data provided predictive information on the precision with which static flux box measurements can determine the actual methane emission value in a particular field. The results of this study are related to the general global question of spatial variability in rice fields by comparisons with experimental and calculated methane emissions from several comparably managed rice fields around the world. Results from the present study indicate that methane emission values obtained from static flux box measurements are within +/-20% of the actual field values within a 95% confidence interval. A comparison of this study with other reported results and related model calculations indicate that static flux box measurements are within +/-24% of the actual field values.

Sass, Ronald L.; Fisher, Frank M.; Andrews, Jeffrey A.

2002-03-01

151

Methane Emissions from Alaska Arctic Tundra in Response to Climatic Change.  

National Technical Information Service (NTIS)

In situ observations of methane emissions from the Alaska North Slope in 1987 and 1989 provide insight into the environmental interactions regulating methane emissions and into the local- and regional-scale response of the arctic tundra to interannual env...

G. P. Livingston L. A. Morrissey

1992-01-01

152

Methane emission from a landfill and the methane oxidising capacity of its covering soil  

Microsoft Academic Search

Methane emission from a small covered landfill site showed, seasonally varying fluxes, ranging from ?5.9 to 914.3 mg CH4 m?2 d?1. The moisture content of the CH4-oxidising cover soil was thought to cause this variation. Comparing gross and net CH4 emission rates, it was found that the cover soil, due to its CH4 oxidising capacity, had a large mitigating effect

Pascal Boeckx; Oswald van Cleemput; Ida Villaralvo

1996-01-01

153

Assessment of nitrous oxide and methane emissions for California agriculture  

NASA Astrophysics Data System (ADS)

The California Global Warming Solutions Act of 2006 (AB 32) mandates comprehensive strategies to reduce nitrous oxide (N2O) and methane (CH4) emissions. In agriculture crop production, sources of N2O are related to nitrogen fertilization while CH4 emission is associated with rice production. More than half the GHG emissions from agriculture are attributed to N2O production. Currently, baseline N2O emission data for most cropping systems in the State is lacking. Estimates of CH4 emission in rice have been established from previous studies, but a lack of information exists for its expansion into the San Joaquin Delta to address subsidence issues. The paucity of N2O emission data has hampered biogeochemical modeling efforts. The objectives of this assessment are to (1) measure annual N2O and CH4 emissions for major California crops (vineyards, almonds, tomato, wheat, alfalfa, lettuce, and rice) under typical management practices, (2) characterize the effects of environmental factors on the temporal profile of N2O and CH4 emissions, and (3) determine N2O emission factors. The growth of rice in Delta peat soils produced highly variable CH4 emissions depending on tillage intensity. In 2010, standard tillage produced 184 kg CH4-C/ha while in 2011 after deep plowing placing rice residue deeper into the soil, only 26 kg CH4-C/ha was observed. In processing tomato systems, an average 2.5 kg N2O-N/ha was emitted with standard fertilization (160 kg N / ha), similar to background emissions and those from a drip irrigated system, while 4.0 to 5.8 kg N2O-N /ha y-1 was emitted at fertilizer rates of 225 and 300 kg N /ha (see Fig. 1 for example of temporal sources of emissions). About half the annual emissions were emitted within 3 d after the first seasonal rainfall event. In other tomato studies, estimated losses of fertilizer N as N2O were 0.38 ± 0.03 kg/ha y-1 in a drip irrigated system and 1.79 ± 0.21 kg/ha y-1 in furrow irrigated system, which was equivalent to 0.19% and 0.73% of the added fertilizer, respectively. In a lettuce production system, annual N2O emissions were about 1 kg N2O-N /ha y-1. In a wheat system, emissions during the growing season in the rainy season were between 1.0 and 1.5 kg N2O-N, with highest emissions occurring after anhydrous ammonium applications. Older alfalfa fields were larger sources of N2O. This two-year dataset will serve as the basis for developing mitigation practices.igure 1. Nitrous oxide emissions in tomato systems in 2009/10 during the rainy season, between starter and sidedress application of fertilizers, during the growing season and after the first rainfall after harvest.

Horwath, W. R.; Burger, M.; Assa, Y.; Wilson, T. J.

2012-12-01

154

Patterns of methane emission from excreta of grazing animals  

Microsoft Academic Search

Emissions of methane from dung pats under field and laboratory conditions have been determined. A range of dung materials from cattle and sheep and from cattle with different background managements was used and results indicated that all acted as significant sources of CH4 over a relatively short period, usually less than 10–15 days. The patterns of release were similar, although

S. C. Jarvis; R. D. Lovell; R. Panayides

1995-01-01

155

Methane emissions to the atmosphere through aquatic plants  

NASA Technical Reports Server (NTRS)

The movement of methane (CH4) from anaerobic sediments through the leaves, stems, and flowers of aquatic plants and into the atmosphere was found to provide a significant pathway for the emission of CH4 from the aquatic substrates of flooded wetlands. Methane concentrations well above the surrounding ambient air levels were found in the mesophyll of 16 varies of aquatic plants and are attributed to transpiration, diffusion, and pressure-induced flow of gaseous CH4 from the roots when they are embedded in CH4-saturated anaerobic sediments. Methane emissions from the emergent parts of aquatic plants were measured using floating chamber techniques and by enclosing the plants in polyethylene bags of known volume. Concentration changes were monitored in the trapped air using syringes and gas chromatographic techniques. Vertical profiles of dissolved CH4 in sediment pore water surrounding the aquatic plants' rhizomes were obtained using an interstitial sampling technique. Methane emissions from the aquatic plants studied varied from 14.8 mg CH4/d to levels too low to be detectable. Rooted and unrooted freshwater aquatic plants were studied as well as saltwater and brackish water plants. Included in the experiment is detailed set of measurements on CH4 emissions from the common cattail (Typha latifolia). This paper illustrates that aquatic plants play an important gas exchange role in the C cycle between wetlands and the atmosphere.

Sebacher, D. I.; Harriss, R. C.; Bartlett, K. B.

1985-01-01

156

On the gas hydtrate methane emissions and possible hypoxia in the East Siberian Arctic Seas  

NASA Astrophysics Data System (ADS)

Recent field companies showed the high concentrations of dissolved methane in the region of East Siberian Arctic Seas (ESAS). These high concentrations were attributed to the degradation of the underwater permafrost which corked the methane from the shallow gas-hydrates deposits (Shakhova, et. al., 2010). Some aspects of the problem of the methane evolution, released at ESAS, were investigated in (Malakhova amd Golubeva, 2013), where the estimated methane emission to the atmosphere was two order lower than the estimates by Shakhova, et.al., 2010. In this study the version of the regional 3D coupled ice-ocean model FEMAO-1 was applied to the problem of the methane transport, oxidation and emission to the atmosphere. Model was driven by the AOMIP-FAMOS forcing 1948-2011, and showed the steady rise of mean bottom temperature at ESAS after 1990 till now. This temperature rise assumed to be sufficient to destabilize undersea permafrost and provoke the additional methane release from gas-hydrates. A set of numerical experiments were carried out to simulate various scenarios of the methane evolution: 1. The quasi-equilibrium state of the dissolved methane distribution forced by the sources at the continental slope and river runoff transport for the period of 1948-1990. This set of experiments was aimed to reproduce the observed methane concentrations and to tune the model parameterizations. 2. The scenario of ESAS abrupt methane release during 1990-2011 with various fractions of dissolved methane and bubbles. The fractions of the dissolved methane and bubbles were previously estimated in (Stepanenko and Iakovlev, 2013). This set of experiments was aimed to reproduce the observed vertical methane distribution with maximum at the ocean surface. 3. The ESAS abrupt methane release with limitation of oxidation in areas of hypoxia. This set of experiments was aimed to evaluate the possibility of hypoxia at the ESAS shelf and beyond, and to estimate the required methane flux to switch off the oxidation. Acknowledgements: This work was supported by the Russian Foundation for Basic Research Project 13-05-12052ofi_m. References. Shakhova, N., I.Semiletov, A.Salyuk, V.Yusupov, D.Kosmach, and Ö.Gustafsson. Extensive Methane Venting to the Atmosphere from Sediments of the East Siberian Arctic Shelf. Science 5 March 2010: Vol. 327 no.5970 pp. 1246-1250 DOI: 10.1126/science.1182221. Malakhova, V. and E. Golubeva. On the possible methane emissions from the East Siberian Arctic Seas. Geophysical Research Abstracts Vol. 15, EGU2013-4480, 2013, EGU General Assembly 2013. Iakovlev, N.G. On the Simulation of Temperature and Salinity Fields in the Arctic Ocean. Izvestiya, Atmospheric and Oceanic Physics. 2012. 48(1), pp. 86-101. doi: 10.1134/S0001433812010136. V. Stepanenko and N. Iakovlev. Numerical simulation of vertical transport and oxidation of methane in Arctic Ocean. Geophysical Research Abstracts Vol. 15, EGU2013-4009-1, 2013, EGU General Assembly 2013.

Iakovlev, Nikolay

2014-05-01

157

A model study of mechanisms of methane transfer from Arctic shelf to the atmosphere  

NASA Astrophysics Data System (ADS)

A possible positive feedback to rapid climate warming in Arctic - degradation of methane hydrates in the shelf bottom ground - has recently attracted attention of many research groups. This was primarily caused by new empirical evidence of very high concentrations of dissolved methane in Russian Arctic and methane fluxes to the atmosphere. A number of studies were conducted to access a possible effect of methane hydrates degradation in response to future warming of the ocean. Climate change scenarios were used to force the models of heat transfer in shelf ground. However, in majority of these works it was assumed that all methane released from shelf bottom reaches atmosphere. This precludes the possibility of taking into account methane bubbles dissolution, methane oxidation and subsequent ocean acidification effects. In this study we apply three modeling frameworks for quantifying these effects. First, one-dimensional (in vertical) model of water reservoir is used (Stepanenko et al. 2011), calculating vertical profiles of dissolved methane, bubbles' parameters and emission to the atmosphere. This model utilizes a bubble model by McGinnis et al. (2006), and diffusion-reaction equations for methane, oxygen and carbon dioxide concentrations in dissolved state. Thus, interaction between bubbles and dissolved gases and methane oxidation are described explicitly. Second, one-dimensional methane model is forced by temperature profile and eddy diffusion coefficients from 3D ocean dynamics model (Iakovlev 2009). And third, methane model is coupled to 3D ocean dynamics model allowing to reproduce advection of methane by oceanic currents in addition to above mentioned processes. This set of experiments allows to assess a significance of ocean dynamics for bottom-released methane transport and methane emission to the atmosphere. Since a number of parameters (e.g. initial bubble radius at the bottom, constants entering reaction rates formulae) are highly uncertain due to lack of relevant observational data, a sensitivity study if performed in respect to these parameters.

Stepanenko, V. M.; Iakovlev, N. G.

2012-04-01

158

An integrated approach for estimation of methane emissions from wetlands and lakes in high latitude regions  

NASA Astrophysics Data System (ADS)

In recent years, there has been increasing evidence of significant alteration in the extent of lakes and wetlands in high latitude regions due in part to thawing permafrost, as well as other changes governing surface and subsurface hydrology. Methane is a 23 times more efficient greenhouse gas than carbon dioxide; changes in surface water extent, and the associated subsurface anaerobic conditions, are important controls on methane emissions in high latitude regions. Methane emissions from wetlands vary substantially in both time and space, and are influenced by plant growth, soil organic matter decomposition, methanogenesis, and methane oxidation controlled by soil temperature, water table level and net primary productivity (NPP). The understanding of spatial and temporal heterogeneity of surface saturation, thermal regime and carbon substrate in northern Eurasian wetlands from point measurements are limited. In order to better estimate the magnitude and variability of methane emissions from northern lakes and wetlands, we present an integrated assessment approach based on remote sensing image classification, land surface modeling and process-based ecosystem modeling. Wetlands classifications based on L-band JERS-1 SAR (100m) and ALOS PALSAR (~30m) are used together with topographic information to parameterize a lake and wetland algorithm in the Variable Infiltration Capacity (VIC) land surface model at 25 km resolution. The enhanced VIC algorithm allows subsurface moisture exchange between surface water and wetlands and includes a sub-grid parameterization of water table position within the wetland area using a generalized topographic index. Average methane emissions are simulated by using the Walter and Heimann methane emission model based on temporally and spatially varying soil temperature, net primary productivity and water table generated from the modified VIC model. Our five preliminary study areas include the Z. Dvina, Upper Volga, Yeloguy, Syum, and Chaya river basins. The temporally-variable inundation extent simulated by the VIC model is compared to 25 km resolution inundation products developed from combined QuikSCAT, AMSR-E and MODIS data sets covering the time period from 2002 onward. The seasonal variation in methane emissions associated with sub-grid variability in water table extent is explored between 1948 and 2006. This work was carried out at Purdue University, at the University of Washington, and at the Jet Propulsion Laboratory, California Institute of Technology, under contract with the NASA.

Chiu, C.; Bowling, L. C.; Podest, E.; Bohn, T. J.; Lettenmaier, D. P.; Schroeder, R.; McDonald, K. C.

2009-04-01

159

Quantifying Methane Emissions from Shale Gas Wells in Pennsylvania  

NASA Astrophysics Data System (ADS)

A major question facing assessment of greenhouse gas sources and sinks is the impact of shale gas drilling operations on methane emissions. Estimating fugitive methane emissions is a challenge because of the temporal variability of emissions and because of the inaccessibility of the emission plumes using traditional measurement techniques. In June of 2012 we conducted flights over shale gas wells in the Marcellus Formation near Washington, PA using Purdue University's Airborne Laboratory for Atmospheric Research (ALAR) which is equipped with a 0.5 Hz Picarro CO2/CH4/H2O analyzer and a programmable flask package provided by NOAA. We calculated methane fluxes for two wells, here denoted as Well Delta and Well Tau, via the aircraft-based mass balance technique that has been previously described by Mays et al. (2009). Briefly, horizontal transects perpendicular to the prevailing wind direction were flown at different altitudes up to the top of the convective boundary layer downwind of a source. The data were interpolated to create a complete 2-d snapshot of methane concentrations derived from the source. By multiplying the background subtracted concentration by the perpendicular component of the horizontal winds and integrating over the plume dimensions the flux can be obtained. During the experiment elevated background concentrations were observed in the southwestern corner of Pennsylvania during the morning shown in Figure 1. We mapped the extent of this elevated methane region and used it to obtain an estimate of the regional enhancement of methane. Here we present our preliminary analysis, and results. Well Delta was sampled in three separate experiments; however, it was close to several other active wells. When the signal was too diffuse to obtain separate well specific fluxes, the flux for the entire area was averaged over the number of wells that may have contributed. Well Tau was sampled during one experiment and a nearby relatively large methane emission source was observed during the experiment. In flight investigation revealed the source of this enhancement to be from a coal mine, for which a flux estimate was made.igure 1. CH4 distribution over southwestern Pennsylvania on 6/21/12 between 9:00 and 10:30 EDT plotted in Google Earth.

Caulton, D.; Shepson, P.; Cambaliza, M. L.; Sparks, J. P.; Santoro, R.; Sweeney, C.; Davis, K. J.; Lauvaux, T.; Howarth, R.; Stirm, B.; Sarmiento, D.; Belmecheri, S.

2012-12-01

160

In situ sensing of methane emissions from natural marine hydrocarbon seeps: A potential remote sensing technology  

Microsoft Academic Search

The sources and sinks of methane, an important greenhouse gas, are poorly constrained. Remote sensing techniques can significantly improve our understanding of the global methane budget. Field and laboratory studies using in situ direct and spectral measurements of methane emissions from natural marine seepage allowed assessment of the feasibility of remote sensing. Methane plume characteristics were estimated by repeated transects

Ira Leifer; Dar Roberts; Jack Margolis; Frank Kinnaman

2006-01-01

161

Global Scale Methane Emissions from On-Site Wastewater Management  

NASA Astrophysics Data System (ADS)

Pit latrines and other on-site sanitation methods are important forms of wastewater management at the global scale, providing hygienic and low-cost sanitation for more than 1.7 billion people in developing and middle-income regions. Latrines have also been identified as major sources of the greenhouse gas methane (CH4) from the anaerobic decomposition of organic waste in pits. Understanding the greenhouse gas footprint of different wastewater systems is essential for sustainable water resource development and management. Despite this importance, CH4 emissions from decentralized wastewater treatment have received little attention in the scientific literature, and the rough calculations underlying government inventories and integrated assessment models do not accurately capture variations in emissions within and between countries. In this study, we improve upon earlier efforts and develop the first spatially explicit approach to quantifying latrine CH4 emissions, combining a high-resolution geospatial analysis of population, urbanization, and water table (as an indicator of anaerobic decomposition pathways) with CH4 emissions factors from the 2006 IPCC Guidelines for National Greenhouse Gas Inventories. Country-level health and sanitation surveys were used to determine latrine utilization in 2000 and predict usage in 2015. 18 representative countries in Asia, Africa, and Latin America were selected for this analysis to illustrate regional variations in CH4 emissions and to include the greatest emitting nations. Our analysis confirms that pit latrines are a globally significant anthropogenic CH4 source, emitting 4.7 Tg CH4 yr-1 in the countries considered here. This total is projected to decrease ~25% by 2015, however, driven largely by rapid urbanization in China and decreased reliance on latrines in favor of flush toilets. India has the greatest potential for large growth in emissions in the post-2015 period, since public health campaigns to end open defecation, which is currently practiced by more than 600 million people in India, will rely heavily on latrines. Our results emphasize that decisions regarding water and sanitation can significantly influence anthropogenic CH4 emissions, and that discussions around sustainable water resources policy should give full consideration to the greenhouse gas impacts of decentralized sanitation systems like latrines. We conclude with a brief discussion of household biogas and composting toilets as CH4 mitigation options which also allow for harvesting of renewable energy and/or nutrients from wastewater.

Reid, M. C.; Guan, K.; Mauzerall, D. L.

2013-12-01

162

Measurement and prediction of enteric methane emission  

Microsoft Academic Search

The greenhouse gas (GHG) emissions from the agricultural sector account for about 25.5% of total global anthropogenic emission.\\u000a While CO2 receives the most attention as a factor relative to global warming, CH4, N2O and chlorofluorocarbons (CFCs) also cause significant radiative forcing. With the relative global warming potential of 25\\u000a compared with CO2, CH4 is one of the most important GHGs.

Veerasamy Sejian; Rattan Lal; Jeffrey Lakritz; Thaddeus Ezeji

2011-01-01

163

Recent findings on methane emissions from vegetation (Invited)  

NASA Astrophysics Data System (ADS)

Three years ago, Keppler et al. (2006) reported from laboratory experiments that living plants, plant litter and the structural plant component pectin emit methane to the atmosphere under aerobic conditions. These observations caused considerable controversy amongst the scientific community and the general public because of their far-reaching implications for two main reasons. Firstly, it is generally accepted knowledge that the reduced compound methane can only be produced naturally from organic matter by methanogens in the absence of oxygen, or at high temperatures, e.g. in biomass burning. The fact that no mechanism for ‘aerobic’ production of methane had been identified at the molecular level in plants added to the consternation. Secondly, the first extrapolations from laboratory measurements to the global scale indicated that these emissions could constitute a substantial fraction of the total global emissions of methane. After publication of the findings of Keppler et al. (2006), their extrapolation procedure employed was severely criticised, and other up-scaling calculations suggested much lower methane emissions. However, it became clear, that without further insight into the mechanism of the ‘aerobic’ production of methane, any up-scaling approach would have considerable uncertainties and thus be of questionable value. Whilst several subsequent studies (e.g. Dueck et al., 2007, Nisbet et al., 2009) could not confirm the original findings of Keppler et al. (2006) others (e.g. McLeod et al., 2008) including stable isotope studies (e.g. Vigano et al., 2009) verified methane formation from both dead plant tissues and living intact plants (Brüggemann et al. 2009).Therefore, the principle scientific questions are now: if, by how much, and by what mechanisms is methane emitted from dead plant matter and living vegetation. An overview of the current state of knowledge and the most recent findings will be presented. References: Brüggemann N, et al. (2009) New Phytologist, 23, 912-918. Dueck TA, et al. (2007). New Phytologist, 175, 29-35. Keppler F, et al. (2006). Nature 439, 187-191. McLeod AR, et al. (2008). New Phytologist, 180, 124-132. Nisbet RER, et al. (2009). Proc. R. Soc. B, 276, 1347-1354. Vigano I, et al. (2009). Atmospheric Environment, in press.

Keppler, F.; Roeckmann, T.; Vigano, I.; Hamilton, J. T.; McLeod, A.

2009-12-01

164

Hydrogen sulphide and methane emissions on the central Namibian shelf  

NASA Astrophysics Data System (ADS)

Hydrogen sulphide occurs frequently in the waters of the inner shelf coastal upwelling area off central Namibia. The area affected coincides with hatching grounds of commercially important pelagic fish, whose recruitment may be severely affected by recurring toxic sulphidic episodes. Both episodic biogenic methane gas-driven advective and molecular diffusive flux of hydrogen sulphide have been implicated as transport mechanisms from the underlying organic-matter-rich diatomaceous mud. To test hypotheses on the controls of hydrogen sulphide transport from the sediments on the inner Namibian shelf, water column and sediment data were acquired from four stations between 27 and 72 m water depth over a 3 year long period. On 14 cruises, temperature, salinity, dissolved oxygen, nitrate, methane, and total dissolved sulphide were determined from water column samples, and pore water dissolved methane, total dissolved sulphide, biomass of benthic sulphide-oxidising bacteria Beggiatoa and Thiomargarita, and bacterial sulphate reduction rates were determined from sediment cores. Superimposed on a trend of synchronous changes in water column oxygen and nutrient concentrations controlled by regional hydrographic conditions were asynchronous small-scale variations at the in-shore stations that attest to localized controls on water column chemistry. Small temporal variations in sulphate reduction rates determined with 35S-labeled sulphate do not support the interpretation that variable emissions of sulphide and methane from sediments are driven by temporal changes in the degradation rates of freshly deposited organic matter. The large temporal changes in the concentrations of hydrogen sulphide and the co-occurrence of pore water sulphate and methane support an interpretation of episodic advection of methane and hydrogen sulphide from deeper sediment depths - possibly due to gas bubble transport. Effective fluxes of hydrogen sulphide and methane to the water column, and methane and sulphide concentrations in the bottom waters were decoupled, likely due to the activity of sulphide-oxidising bacteria. While the causal mechanism for the episodic fluctuations in methane and dissolved sulphide concentrations remains unclear, this data set points to the importance of alternating advective and diffusive transport of methane and hydrogen sulphide to the water column.

Brüchert, Volker; Currie, Bronwen; Peard, Kathleen R.

2009-12-01

165

Methane emission from mires of the West Siberian taiga  

NASA Astrophysics Data System (ADS)

In the summer-autumn seasons of 2007-2011, the methane emission from typical mire landscapes of Western Siberia was studied using the static chamber method. The lowest methane flux turned out to be characteristic of the ryams (pine-dwarf shrub-sphagnum associations) and the ridges of the ridge-hollow complexes, as well as of the wetland lakes in the northern and middle taiga (the medians are within the range of 0.1-0.5 mg C-CH4/m2 h). Values that are 10 times higher are typical for the oligotrophic hollows, fens, peat mats, and poor fens in different subzones (the medians are 2 to 7 mg C-CH4/m2 h). The maximal values of the methane flux from the wetland lakes of the southern taiga are 17.98 mg C-CH4/m2 h. Based on the data obtained by the authors, along with the previously published ones, the regional methane fluxes from the taiga mires were calculated: 2.22 Mt C-CH4/m2 per year, or about 80% of the total methane flux from the West Siberian mires. The estimates of the CH4 regional flux obtained by other researchers are discussed; the main source of the estimation uncertainty is analyzed.

Sabrekov, A. F.; Glagolev, M. V.; Kleptsova, I. E.; Machida, T.; Maksyutov, S. S.

2013-12-01

166

Estimation of methane and nitrous oxide emissions from Indian livestock.  

PubMed

Greenhouse gas (GHG; methane and nitrous oxide) emissions from enteric fermentation and manure management of Indian livestock were estimated from the last two Indian livestock census datasets (2003 and 2007) using IPCC Tier 2 (2006) guidelines. The total annual GHG emissions from Indian livestock increased in 2007 compared to the year 2003 with an annual growth rate of 1.52% over this period. The contributions of GHG by dairy cattle, non-dairy cattle, buffaloes, goats, sheep and other animals (yak, mithun, horse, donkeys, pigs and poultry) were 30.52, 24.0, 37.7, 4.34, 2.09 and 3.52%, respectively, in 2007. Enteric fermentation was the major source of methane, accounting for 89.2% of the total GHG emissions, followed by manure methane (9.49%). Nitrous oxide emissions accounted for 1.34%. GHG emissions (CO(2)-eq. per kg of fat and protein corrected milk (FPCM)) by female animals were considerably lower for crossbred cows (1161 g), followed by buffaloes (1332 g) and goats (2699 g), and were the highest for indigenous cattle (3261 g) in 2007. There was a decreasing trend in GHG emissions (-1.82% annual growth rate) in relation to milk production from 2003 to 2007 (1818 g and 1689 g CO(2)-eq. per kg FPCM in 2003 and 2007, respectively). This study revealed that GHG emissions (total as well as per unit of products) from dairy and other categories of livestock populations could be reduced substantially through proper dairy herd management without compromising animal production. In conclusion, although the total GHG emissions from Indian livestock increased in 2007, there was a decreasing trend in GHG production per kg of milk production or animal products. PMID:22898933

Patra, Amlan K

2012-10-26

167

Wetlands and methane emission in the XXI century: RCM-based projection for Northern Eurasia  

NASA Astrophysics Data System (ADS)

Russia has largest resources of wetlands in the world. Marshes and forested swamps occupy up to 20% of country's territory. The role of wetlands in the natural processes and human society is multifunctional: from providing wildlife habitat and biodiversity to determining water filtration and runoff control. Wetland is an important agent in the global cycling of greenhouse gases. Their exchanges with the atmosphere affects to the regional and global climates thus represent an essential component of environment. In this study the changes in the spatial distributions of wetlands and methane emission are evaluated using the output from MGO GCM/RCM future climate projection. The calculations were performed for the late 20th century (1981-2000) and mid 21st century (2041-2060) under IPCC A2 GHG/aerosols emission scenario. Several characteristics including moisture coefficient and water table have been analysed in order to describe wetland distribution across Eurasia. It has been found that there is a considerable uncertainty in distributions of the analysed characteristics that complicates wetland identification. The water table depth has been adopted to approximate observed distribution of wetlands. As projected by the regional climate model for the mid 21st century the wetland area will expand, notably in May and September and shrink in summer. Evaluated are methane emissions for the late 20th century over wetlands and its possible changes by the mid 21st century. According to RCM projection the methane emission will likely increase in the forthcoming 50 years due to climate warming by approximately 30%. Modeling deficiencies in the wetland distributions and methane emission calculations are discussed. An attention in the analysis is also given to the expected changes in the methane emission potential due to taliks and lakes.

Pikaleva, A.

2012-04-01

168

Determination of Methane Emissions by Region and Generating Process Using Inverse Methods  

NASA Astrophysics Data System (ADS)

Methane is a chemically and radiatively important trace gas with a wide range of geographically and temporally varying biogenic and anthropogenic sources and sinks. A powerful method for determining the net methane fluxes due to these sources and sinks involves solution of an inverse problem in which the observed concentrations are effectively lagrangian line integrals and the unknown fluxes are contained in the integrands. The general method calculates optimal estimates in the Bayesian sense using an eulerian or lagrangian atmospheric transport model and global atmospheric methane measurements. We review the results of previous studies of regional and global methane fluxes using these methods. We also present the results of a recently completed study using a Kalman filter and the global 3D Model for Atmospheric Transport and Chemistry (MATCH) driven by NCEP analysed observed meteorology at T62 (1.8o x 1.8o) resolution. Monthly fluxes are optimally estimated for three large wetland/bog regions, rice agriculture (globally aggregated), and three large biomass burning regions. The study uses AGAGE, CMDL and other methane observations for 1996-2001 and also estimates average annual emissions from coal, gas, animals and waste sites. Deduced seasonal cycles for the biogenic sources (including rice) are qualitatively similar to prior estimates from site measurements but show differences in peak amplitudes and phases and significant year-to-year variability. Emissions from rice-growing regions are greater than prior estimates, while emissions from fossil sources are less. Enhanced emissions from northern wetland/bog regions are inferred to be the dominant contributor to the large 1998 increases in methane.

Prinn, P. G.

2004-12-01

169

Atmospheric methane observed from space over the Asian monsoon: implications for emission from Asian rice paddies  

Microsoft Academic Search

More than 40% of anthropogenic emissions of methane, the second most important greenhouse gas, is estimated to be from agricultural sources, including rice cultivation. Unfortunately, the strength of individual sources of methane remains uncertain, despite the importance of its effect in global warming. Here we focus on the Asian monsoon region to improve our understanding of methane emission from rice

S. Hayashida; S. Yoshizaki; C. Frankenberg; X. Yan

2010-01-01

170

Revisiting factors controlling methane emissions from high-arctic tundra  

NASA Astrophysics Data System (ADS)

Among the numerous studies of methane emission from northern wetlands the number of measurements carried on at high latitudes (north of the Arctic Circle) is very limited, and within these there is a bias towards studies of the growing season. Here we present results of five years of automatic chamber measurements at a high-arctic location in Zackenberg, NE Greenland covering both the growing seasons and two months of the following freeze-in period. The measurements show clear seasonal dynamics in methane emission. The start of the growing season increase in CH4 fluxes were strongly related to the date of snow melt. The greatest variation in fluxes between the study years were observed during the first part of the growing season. Somewhat surprisingly this variability could not be explained by commonly known factors controlling methane emission, i.e. temperature and water table position. Late in the growing season CH4 emissions were found to be very similar between the study years (except the extremely dry 2010) despite large differences in climatic factors (temperature and water table). Late-season bursts of CH4 coinciding with soil freezing in the autumn were observed at least during three years between 2006 and 2010. The accumulated emission during the freeze-in CH4 bursts was comparable in size with the growing season emission for the year 2007, and about one third of the growing season emissions for the years 2009 and 2010. In all three cases the CH4 burst was accompanied by a~corresponding episodic increase in CO2 emission, which can compose a significant contribution to the annual CO2 flux budget. The most probable mechanism of the late season CH4 and CO2 bursts is physical release of gases, accumulated in the soil during the growing season. In this study we investigate the drivers and links between growing season and late season fluxes. The reported surprising seasonal dynamics of CH4 emissions at this site show that there are important occasions where conventional knowledge on factors controlling methane emissions is overruled by other processes, acting in longer than seasonal time scales. Our findings suggest the importance of multiyear studies with continued focus on shoulder seasons.

Mastepanov, M.; Sigsgaard, C.; Tagesson, T.; Ström, L.; Tamstorf, M. P.; Lund, M.; Christensen, T. R.

2012-11-01

171

Revisiting factors controlling methane emissions from high-arctic tundra  

NASA Astrophysics Data System (ADS)

Among the numerous studies of methane emission from northern wetlands the number of measurements carried on at high latitudes (north of the Arctic Circle) is very limited, and within these there is a bias towards studies of the growing season. Here we present results of five years of automatic chamber measurements at a high-arctic location in Zackenberg, NE Greenland, covering both the growing seasons and two months of the following freeze-in period. The measurements show clear seasonal dynamics in methane emission. In the beginning of the growing season increase in CH4 fluxes was strongly related to the date of snow melt. The greatest variation in fluxes between the study years were observed during the first part of the growing season. Somewhat surprisingly this variability could not be explained by commonly known factors controlling methane emission, i.e. temperature and water table position. Late in the growing season CH4 emissions were found to be very similar between the study years (except the extremely dry 2010) despite large differences in climatic factors (temperature and water table). Late-season bursts of CH4 coinciding with soil freezing in the autumn were observed at least during three out of five years 2006 - 2010. The accumulated emission during the freeze-in CH4 bursts was comparable in size with the growing season emission for the year 2007, and about one third of the growing season emissions for the years 2009 and 2010. In all three cases the CH4 burst was accompanied by a corresponding episodic increase in CO2 emission, which can compose a significant contribution to the annual CO2 flux budget. The most probable mechanism of the late season CH4 and CO2 bursts is physical release of gases, accumulated in the soil during the growing season. In this study we investigate the drivers and links between growing season and late season fluxes. The reported surprising seasonal dynamics of CH4 emissions at this site show that there are important occasions where conventional knowledge on factors controlling methane emissions is overruled by other processes, acting in longer than seasonal time scales. Our findings suggest the importance of multiyear studies with continued focus on shoulder seasons.

Mastepanov, Mikhail; Sigsgaard, Charlotte; Tagesson, Torbern; Strom, Lena; Tamstorf, Mikkel; Lund, Magnus; Christensen, Torben

2013-04-01

172

Development of methane emission factors for Indian paddy fields and estimation of national methane budget  

Microsoft Academic Search

A state-wise assessment of methane (CH4) budget for Indian paddies, based on a decadal measurement data across India is presented for the calendar year (CY) 1994, the base year for India’s Initial National Communication (NATCOM) to the United Nations Framework Convention on Climate Change (UNFCCC), along with national trend from CY 1979 to 2006. The NATCOM CH4 emission factors (EFs)

Prabhat K. Gupta; Vandana Gupta; C. Sharma; S. N. Das; N. Purkait; T. K. Adhya; H. Pathak; R. Ramesh; K. K. Baruah; L. Venkatratnam; Gulab Singh; C. S. P. Iyer

2009-01-01

173

Methane fugitive emissions quantification using the novel 'plume camera' (spatial correlation) method  

NASA Astrophysics Data System (ADS)

Fugitive emissions of methane into the atmosphere are a major concern facing the natural gas production industry. Given that the global warming potential of methane is many times greater than that of carbon dioxide, the importance of quantifying methane emissions becomes clear. The rapidly increasing reliance on shale gas (or other unconventional sources) is only intensifying the interest in fugitive methane releases. Natural gas (which is predominantly methane) is an attractive energy source, as it emits 40% less carbon dioxide per Joule of energy generated than coal. However, if just a small percentage of the natural gas consumed is lost due to fugitive emissions during production, processing, or transport, this global warming benefit is lost (Howarth et al. 2012). It is therefore imperative, as production of natural gas increases, that the fugitive emissions of methane are quantified accurately. Traditional direct measurement techniques often involve physical access of the leak itself to quantify the emissions rate, and are generally require painstaking effort to first find the leak and then quantify the emissions rate. With over half a million natural gas producing wells in the U.S. (U.S. Energy Information Administration), not including the associated processing, storage, and transport facilities, and with each facility having hundreds or even thousands of fittings that can potentially leak, the need is clear to develop methodologies that can provide a rapid and accurate assessment of the total emissions rate on a per-well head basis. In this paper we present a novel method for emissions quantification which uses a 'plume camera' with three 'pixels' to quantify emissions using direct measurements of methane concentration in the downwind plume. By analyzing the spatial correlation between the pixels, the spatial extent of the instantaneous plume can be inferred. This information, when combined with the wind speed through the measurement plane, provides a direct measurement of the emission rate. One example of this method is shown in Fig. 1. This method is simple to deploy, does not require an accurate model of atmospheric transport or knowledge of the distance to the emission source or its spatial distribution. Accurate measurements of the emissions can be made with just a few minutes of data collection. Results of controlled release methane experiments are presented, and the strengths and limitations of the methodology are discussed. REFERENCES R. Howarth, R. Santoro, and A. Ingraffea (2011): "Methane and the greenhouse-gas footprint of natural gas from shale formations," Climatic Change 106, 679 - 690. Fig 1: Spatial correlation analysis for two measurement points (or pixels) distributed vertically (A and B) or horizontally (A and C), for measurements at a distance of 21 meters from a methane point source of 650 sccm. The emission rate recovered from this analysis was 496 ± 160 sccm of CH4. The total measurement time was 30 minutes.

Crosson, E.; Rella, C.

2012-12-01

174

Methane from the Tropospheric Emission Spectrometer (TES)  

NASA Technical Reports Server (NTRS)

TES V5 CH4 captures latitudinal gradients, regional variability and interannual variation in the free troposphere. V5 joint retrievals offer improved sensitivity to lower troposphere. Time series extends from 2004 to present. V5 reprocessing in progress. Upper tropospheric bias. Mitigated by N2O correction. Appears largely spatially uniform, so can be corrected. How to relate free-tropospheric values to surface emissions.

Payne, Vivienne; Worden, John; Kulawik, Susan; Frankenberg, Christian; Bowman, Kevin; Wecht, Kevin

2012-01-01

175

Cost-effectiveness of emission-reducing measures for methane in the Netherlands  

Microsoft Academic Search

The present methane emissions in the Netherlands amount to 1190 ktonne per year. It is expected that these emissions will decrease by 20% up to the year 2000 due to environmental policies already in place. However, additional emission reduction may be necessary. In this article, the reduction potential and specific costs of additional methane emission reduction measures are presented. The

David de Jager; Kornelis Blok

1996-01-01

176

Methane production, oxidation and emission in United Kingdom peatlands and the effect of anions from acid rain  

NASA Astrophysics Data System (ADS)

The production, oxidation and emission of methane in UK peatlands was investigated. The main field study site was Ellergower Moss, Dumfriesshire where the peat was characterised by hollows (water-filled depressions) and hummocks (raised vegetative areas). The pathways of carbon flow in peat under hummocks and hollows were determined and compared on a seasonal basis. Methane emissions were significantly greater from hollows than hummocks (0.88 mols and 0.07 mols CH4 m-2 y-1 respectively). Methane emission rates varied seasonally e.g. for hollows were 0.04 mmols CH4 m-2 d-1 for January and 2.3 mmols CH4 m-2 d-1 for June. Methane emissions were modulated by biological methane oxidation by 0% of methane produced in the winter months, increasing during spring until 97% of methane produced was oxidised in the summer months. Both methane oxidation and methanogenesis were strongly temperature dependant with Q10 values of 2.2 and 16, respectively. Rates of methane oxidation potential (MOP) were greatest between 4-8 cm depths below the level of the water table, and were located above the most active zone of methanogenesis (8-16 cm depths below the water table levels). This enabled vertically diffusing methane to be utilised by methanotrophic bacteria, providing a very efficient filter for methane. Methanogenesis was limited by hydrogen availability in the peat, but not by acetate, suggesting that methane was produced by hydrogenophilic methanogenic bacteria (MB), rather than acetate utilising MB. Acid rain pollutants were found to significantly affect carbon flow, with sulphate deposition causing a seasonal inhibition in methanogenesis. Carbon flow predominated through sulphate reduction in the winter and spring months (sulphate reduction to methane production ratio was 1008 and 189, for hummocks and hollows respectively) when sulphate was freely available and when temperatures were low. During the summer when temperatures increased and sulphate became limited carbon flow through methanogenesis predominated (sulphate reduction to methane production ratio 0.39 and 0.07, for hummocks and hollows respectively). The examination of two other peatlands-Great Dun Fell and Caithness which received higher and lower sulphate loadings than Ellergower respectively, did not show a consistent effect of sulphate inhibition on methanogenesis. The methane oxidation kinetics were used in a mathematical model to examine the effect of plant roots on increasing the vertical transport rate of methane out, and oxygen into the peat, by gas phase transport through the roots. (Abstract shortened by UMI.)

Watson, Andrea

177

The impact of air pollutant and methane emission controls on tropospheric ozone and radiative forcing: CTM calculations for the period 1990-2030  

Microsoft Academic Search

To explore the relationship between tropospheric ozone and radiative forcing with changing emissions, we compiled two sets of global scenarios for the emissions of the ozone precursors methane (CH4), carbon monoxide (CO), non-methane volatile organic compounds (NMVOC) and nitrogen oxides (NOx) up to the year 2030 and implemented them in two global Chemistry Transport Models. The \\

F. Dentener; D. Stevenson; J. Cofala; R. Mechler; M. Amann; P. Bergamaschi; F. Raes; R. Derwent

2004-01-01

178

The impact of air pollutant and methane emission controls on tropospheric ozone and radiative forcing: CTM calculations for the period 1990-2030  

Microsoft Academic Search

To explore the relationship between tropospheric ozone and radiative forcing with changing emissions, we compiled two sets of global scenarios for the emissions of the ozone precursors methane (CH4), carbon monoxide (CO), non-methane volatile organic compounds (NMVOC) and nitrogen oxides (NOx) up to the year 2030 and implemented them in two global Chemistry Transport Models. The \\

F. Dentener; D. Stevenson; J. Cofala; R. Mechler; M. Amann; P. Bergamaschi; F. Raes; R. Derwent

2005-01-01

179

Revisiting factors controlling methane emissions from high-Arctic tundra  

NASA Astrophysics Data System (ADS)

The northern latitudes are experiencing disproportionate warming relative to the mid-latitudes, and there is growing concern about feedbacks between this warming and methane production and release from high-latitude soils. Studies of methane emissions carried out in the Arctic, particularly those with measurements made outside the growing season, are underrepresented in the literature. Here we present results of 5 yr (2006-2010) of automatic chamber measurements at a high-Arctic location in Zackenberg, NE Greenland, covering both the growing seasons and two months of the following freeze-in periods. The measurements show clear seasonal dynamics in methane emission. The start of the growing season and the increase in CH4 fluxes were strongly related to the date of snowmelt. Within each particular growing season, CH4 fluxes were highly correlated with the soil temperature (R2 > 0.75), which is probably explained by high seasonality of both variables, and weakly correlated with the water table. The greatest variability in fluxes between the study years was observed during the first part of the growing season. Somewhat surprisingly, this variability could not be explained by commonly known factors controlling methane emission, i.e. temperature and water table position. Late in the growing season CH4 emissions were found to be very similar between the study years (except the extremely dry 2010) despite large differences in climatic factors (temperature and water table). Late-season bursts of CH4 coinciding with soil freezing in the autumn were observed during at least three years. The cumulative emission during the freeze-in CH4 bursts was comparable in size with the growing season emission for the year 2007, and about one third of the growing season emissions for the years 2009 and 2010. In all three cases the CH4 burst was accompanied by a corresponding episodic increase in CO2 emission, which can compose a significant contribution to the annual CO2 flux budget. The most probable mechanism of the late-season CH4 and CO2 bursts is physical release of gases accumulated in the soil during the growing season. In this study we discuss possible links between growing season and autumn fluxes. Multiannual dynamics of the subsurface CH4 storage pool are hypothesized to be such a link and an important driver of intearannual variations in the fluxes, capable of overruling the conventionally known short-term control factors (temperature and water table). Our findings suggest the importance of multiyear studies with a continued focus on shoulder seasons in Arctic ecosystems.

Mastepanov, M.; Sigsgaard, C.; Tagesson, T.; Ström, L.; Tamstorf, M. P.; Lund, M.; Christensen, T. R.

2013-07-01

180

Methane oxidation and methanotrophs: resistance and resilience against model perturbations  

NASA Astrophysics Data System (ADS)

Biodiversity is claimed to be essential for ecosystem functioning. However, most experiments on biodiversity and ecosystem functioning (BEF) have been made on higher plants, while only few studies have dealt with microbial communities. Overall microbial diversity may be very high, and general functions like aerobic carbon mineralization are assumed to be supported by highly redundant communities. Therefore, we focused on methane oxidation, a microbial process of global importance mitigating methane emissions from wetland, rice fields, and landfills. We used a rice paddy as our model system, where >90% of potentially emitted methane may be oxidized in the oxic surface layer. This community is presumed to consist of 10-20 taxa more or less equivalent to species. We focused on the ability of methanotrophs to recover from a disturbance causing a significant die-off of all microbial populations. This was simulated by mixing native with sterile soil in two ratios (1:4 and 1:40). Microcosms were incubated and the temporal shift of the methanotrophic communities was followed by pmoA-based Terminal Restriction Length Polymorphism (T-RFLP), qPCR, and a pmoA-based diagnostic microarray. We consistently observed distinctive temporal shifts between Methylocystaceaea and Methylococcacea, a rapid population growth leading to the same or even higher cell numbers as in microcosms made from native soil alone, but no effect on the amount of methane oxidized. The ratio of different methanotrophs changed with treatment, while the number of taxa stayed nearly the same. Overall, methanotrophs showed a remarkable resilience compensating for die-offs. It has to be noted, however, that our experiment focused on methanotrophs adapted to and living at high methane fluxes. Quite different, methanotrophs living in upland soils do not mitigate methane emissions, but are the only biological sink to atmospheric methane. These microbes are severely substrate limited, and will be much more susceptible to perturbations.

Ho, A.; Frenzel, P.

2009-04-01

181

Environmental factors controlling methane emissions from peatlands in northern Minnesota  

NASA Technical Reports Server (NTRS)

The environmental factors affecting the emission of methane from peatlands were investigated by correlating CH4 emission data for two years, obtained from five different peatland ecosystems in northern Minnesota, with peat temperature, water table position, and degree of peat humification. The relationship obtained between the CH4 flux and these factors was compared to results from a field manipulation experiment in which the water table was artificially raised in three experimental plots within the driest peatland. It was found that peat temperature, water table position, and degree of peat humification explained 91 percent of the variance in log CH4 flux, successfully predicted annual CH4 emission from individual wetlands, and predicted the change in flux due to the water table manipulation. Raising the water table in the bog corrals by an average of 6 cm in autumn 1989 and 10 cm in summer 1990 increased CH4 emission by 2.5 and 2.2 times, respectively.

Dise, Nancy B.; Gorham, Eville; Verry, Elon S.

1993-01-01

182

Decreasing anthropogenic methane emissions in Europe and Siberia inferred from continuous carbon dioxide and methane observations at Alert, Canada  

NASA Astrophysics Data System (ADS)

The rate of increase in global atmospheric methane (CH4) abundance has steadily declined since the late 1980s with near zero increase from 1999 through 2006. At the Canadian Baseline Observatory at Alert, Canada (82°28'N, 62°30'W), continuous measurements of methane (CH4) and carbon dioxide (CO2) have been made since 1987. During winter, both gases are frequently highly correlated during well-defined episodes lasting from 2 to 5 days. We observe a gradual decrease in the ratios of CH4/CO2 during these episodes from ˜16 ppb CH4 (ppm CO2)-1 to ˜12 ppb CH4 (ppm of CO2)-1 over the entire record. An atmospheric transport model with prescribed CO2 and CH4 source distributions is used to partition simulated CH4 events into contributions by region. We show that anthropogenic emissions from Europe and Siberia account for more than 85% of the CO2 and CH4 enhancements simulated at Alert, but without a change in CH4 emissions, modeled CH4/CO2 ratios remain constant. To reproduce the observed trend in the ratio of CH4/CO2, the model requires a reduction in emissions of CH4 on the order of 30 Tg (13.6 to 33.4 Tg) in Europe and Siberia over the observational period. This is about twice the drop reported by the Emission Database for Global Atmospheric Research (EDGAR) emissions inventory and large enough to account for the leveling off of the global atmospheric CH4 burden observed over the past 20 years.

Worthy, Douglas E. J.; Chan, Elton; Ishizawa, Misa; Chan, Douglas; Poss, Christian; Dlugokencky, Edward J.; Maksyutov, Shamil; Levin, Ingeborg

2009-05-01

183

Compositional modeling of enhanced coalbed methane recovery  

NASA Astrophysics Data System (ADS)

A development and validation of a three-dimensional, two-phase, dual porosity, fully implicit, compositional coalbed simulator is presented. A multicomponent sorption equilibria using a thermodynamically consistent ideal adsorbed solution theory and Peng-Robinson equation of state is implemented to the simulator using a non-equilibrium sorption formulation. The simulator is used to model the nitrogen and carbon dioxide injections in the enhanced coalbed methane recovery which involves gas component and fluid phase appearances and disappearances. The effects of absolute permeability, vertical heterogeneity, lateral heterogeneity, and sorption time constant to the methane recovery performance are studied. The performances of nitrogen and carbon dioxide injections in the enhanced coalbed methane recovery are compared. The roles of the injected gas composition, delayed injection, well spacing, cyclic injection/production, and intermittent gas injection to the methane recovery performance are studied.

Manik, Julio

184

Quantifying the effect of oxidation on landfill methane emissions  

Microsoft Academic Search

Field, laboratory, and computer modeling methods were utilized to quantitatively assess the capability of aerobic microorganisms to oxidize landfill-derived methane (CH4) in cover soils. The investigated municipal landfill, located in Nashua, New Hampshire, was operating without gas controls of any type at the time of sample collection. Soil samples from locations of CH 4 flux to the atmosphere were returned

P. M. Czepiel; B. Mosher; P. M. Crill; R. C. Harriss

1996-01-01

185

Measurements of methane emissions from rice fields in China  

NASA Astrophysics Data System (ADS)

Rice fields have always been regarded as one of the largest anthropogenic sources of atmospheric methane. Here we report the results of a 7-year study of methane emissions from rice fields in the Sichuan Province of China. In this region, there is one crop of rice per year, the fields are continuously flooded from transplanting to harvest, and there is heavy use of organic fertilizers. Emissions over the entire growing season were measured from each of up to 24 plots. Environmental variables were measured and relevant supporting data on the agricultural practices were recorded. The fields were studied under prevailing agricultural practices of the local farmers. The results represent emissions under standard agricultural practices and the year to year variability of climate, fertilizers, available irrigation water, and cultivars. Based on some 5000 flux measurements, the average emission rates between 1988 and 1994 were 30 mg/m2/h for a growing season of between 100 and 120 days. This emission rate is comparable to other published data from similar rice fields but somewhat on the high side of the range. There were no systematic trends of emissions during the 7 years of our experiment, but there was substantial year to year variability. The data have been subjected to exhaustive analyses for validity, accuracy, and reliability. From this, a high-quality, spatially averaged data set has been constructed representing average emissions from the rice fields for each day when measurements were taken. We describe here the main observational results and document the spatial and temporal variability observed on timescales ranging from a day to several years and on spatial scales ranging from 0.5 m2 to 16 m2.

Khalil, M. A. K.; Rasmussen, R. A.; Shearer, M. J.; Dalluge, R. W.; Ren, L. X.; Duan, C.-L.

1998-10-01

186

Design and evaluation of a porous burner for the mitigation of anthropogenic methane emissions.  

PubMed

Methane constitutes 15% of total global anthropogenic greenhouse gas emissions. The mitigation of these emissions could have a significant near-term effect on slowing global warming, and recovering and burning the methane would allow a wasted energy resource to be exploited. The typically low and fluctuating energy content of the emission streams makes combustion difficult; however porous burners-an advanced combustion technology capable of burning low-calorific value fuels below the conventional flammability limit-are one possible mitigation solution. Here we discuss a pilot-scale porous burner designed for this purpose. The burner comprises a cylindrical combustion chamber filled with a porous bed of alumina saddles, combined with an arrangement of heat exchanger tubes for preheating the incoming emission stream. A computational fluid dynamics model was developed to aid in the design process. Results illustrating the burner's stable operating range and behavior are presented: stable ultralean combustion is demonstrated at natural gas concentrations as low as 2.3 vol%, with transient combustion at concentrations down to 1.1 vol%; the system is comparatively stable to perturbations in the operating conditions, and emissions of both carbon monoxide and unburned hydrocarbons are negligible. Based on this pilot-scale demonstration, porous burners show potential as a methane mitigation technology. PMID:20000525

Wood, Susie; Fletcher, David F; Joseph, Stephen D; Dawson, Adrian; Harris, Andrew T

2009-12-15

187

Possible Jovian methane emission at 76 GHz in coincidence with decameter activity  

NASA Technical Reports Server (NTRS)

The tentative detection of a methane line in emission at 76.2 GHz in the atmosphere of Jupiter is reported. The observed feature is well-correlated with the presence and absence of Jovian decameter-emission activity on successive days. The present results may represent the first detection of extraterrestrial methane microwave emission.

Fox, K.; Jennings, D. E.

1977-01-01

188

Mars methane emission and transport scenarios using the GEM-Mars GCM  

NASA Astrophysics Data System (ADS)

The observation of methane (Formisano et al., 2004; Krasnopolsky et al., 2004; Mumma et al., 2009) in the Martian atmosphere has raised questions about its source and origin as well as its chemical behaviour. The photochemical lifetime of methane is on the order of several hundred years which would give a well-mixed, uniform distribution but measurements suggest locally enhanced "plumes". The GEM-Mars three-dimensional global chemistry-climate model is used to investigate the possible emission rates and lifetime of methane. The model simulations have a horizontal resolution of 4x4 degrees with 101 vertical levels up to approximately 140 km. References Formisano, V., S. Atreya, T. Encrenaz, N. Ignatiev, and M. Giuranna (2004), Detection of Methane in the Atmosphere of Mars, Science 306, 1758 (2004). Krasnopolsky, V. A., J. P. Maillard, and T. C. Owen (2004), Icarus 172, 537. Mumma, M.J., G.L. Villanueva, R.E. Novak, T. Hewagama, B.P. Bonev, M.A. DiSanti, A.M. Mandell, and M.D. Smith (2009), Strong Release of Methane on Mars in Northern Summer 2003. Science, 2009. 323: p. 1041-1045.

Neary, Lori; Daerden, Frank; Kaminski, J. W.; McConnell, J. C.

2010-05-01

189

Natural emissions of methane from geological seepage in Europe  

NASA Astrophysics Data System (ADS)

Recent studies have shown that geological emissions of methane are an important greenhouse-gas source. Remarkable amounts of methane, estimated in the order of 40-60 Tg yr -1, are naturally released into the atmosphere from the Earth's crust through faults and fractured rocks. The main source is natural gas, both microbial and thermogenic, produced in hydrocarbon-prone sedimentary basins and injected into the atmosphere through macro-seeps (onshore and offshore mud volcanoes and other seeps) and microseepage, an invisible but pervasive flux from the soil. This source is now evaluated for Europe on the basis of a literature survey, new field measurements and derived emission factors. The up-scaling criteria recommended by the EMEP/CORINAIR guidelines are applied to the local point and area source data. In Europe, 25 countries host oil and/or natural gas reservoirs and potentially, or actually, emit geological methane. Flux data, however, are available only from 10 countries: the onshore or offshore petroliferous sectors of Denmark, Italy, Greece, Romania, Spain, Switzerland, United Kingdom and Black Sea countries (Bulgaria, Ukraine, Georgia). Azerbaijan, whose emissions due to mud volcanism are known to be relevant, is included in the estimate. The sum of emissions, regional estimates and local measurements, related to macro-seeps leads to a conservative total value of about 2.2 Tg yr -1. Together with the potential microseepage fluxes from the petroliferous basins, estimated on the basis of the Total Petroleum System concept (around 0.8 Tg yr -1), the total European seepage is projected to 3 Tg yr -1. This preliminary figure would represent, in terms of magnitude, the second natural methane source for Europe after wetlands. The estimate will have to be refined by increasing the number of seepage measurements both on lands, where there is high potential for microseepage (e.g., Germany, Hungary, Romania, Ukraine, Belarus, Russia, Georgia) and in coastal marine areas (the North Sea, the Black Sea, offshore Greece and Italy) where emission factors and the extent of the underwater seeping area are not completely known.

Etiope, Giuseppe

190

[Simulation of methane emissions from rice fields in the Taihu Lake region, China by using different unit of soil database with the DNDC model].  

PubMed

Application of a biogeochemical model, DeNitrification and DeComposition or DNDC, was discussed to assess the impact of CH4 emissions on different soil database from rice fields in Taihu Lake region of China. The results showed that CH4 emissions of the polygon-based soil database of 1:50000, which contained 52034 polygons of paddy soils representing 1107 paddy soil profiles extracted from the latest national soil map (1:50000), were located within the ranges produced by the county-based soil database of 1:50000. However, total emissions of the whole area differed by about 1680 Gg CH4-C. Moreover, CH4 emissions of the polygon-based soil database of 1:50000 and the county-based soil database of 14,000,000, which was the most popular data source when DNDC model was applied in China, have a big estimation discrepancy among each county-based unit in spite of total emissions of the whole area by a difference of 180 Gg CH4-C. This indicated that the more precise soil database was necessary to better simulate CH4 emissions from rice fields in Taihu Lake region using the DNDC model. PMID:19799272

Zhang, Li-ming; Yu, Dong-sheng; Shi, Xue-zheng; Zhao, Li-min; Ding, Wei-xin; Wang, Hong-jie; Pan, Jian-jun

2009-08-15

191

Study of thin biocovers (TBC) for oxidizing uncaptured methane emissions in bioreactor landfills  

Microsoft Academic Search

Bioreactor landfills are designed to accelerate municipal solid waste biodegradation and stabilization; however, the uncaptured methane gas escapes to the atmosphere during their filling. This research investigates the implementation of a novel methane emission control technique that involves thin biocovers (TBC) placed as intermediate waste covers to oxidize methane without affecting the operation of bioreactor landfills. Batch incubation experiments were

Konstantina Perdikea; Anil K. Mehrotra; J. Patrick A. Hettiaratchi

2008-01-01

192

Determinants influencing seasonal variations of methane emissions from alpine wetlands in Zoige Plateau and their implications  

Microsoft Academic Search

To understand the seasonality of methane flux from alpine wetlands in Zoige Plateau, 30 plots were set to measure the methane emissions in the growing and nongrowing seasons in three environmental types: dry hummock (DH), Carex muliensis (CM), and Eleocharis valleculosa (EV) sites. There were clearly seasonal patterns of methane flux in different environmental types in the growing and nongrowing

Huai Chen; Shouping Yao; Ning Wu; Yanfen Wang; Peng Luo; Jianqing Tian; Yongheng Gao; Geng Sun

2008-01-01

193

Production, oxidation, emission and consumption of methane by soils: A review  

Microsoft Academic Search

Methane emission by soils results from antagonistic but correlated microbial activities. Methane is produced in the anaerobic zones of submerged soils by methanogens and is oxidised into CO2 by methanotrophs in the aerobic zones of wetland soils and in upland soils. Methanogens and methanotrophs are ubiquitous in soils where they remain viable under unfavourable conditions. Methane transfer from the soil

Jean Le Mer; Pierre Roger

2001-01-01

194

Reducing Open Cell Landfill Methane Emissions with a Bioactive Alternative Daily.  

National Technical Information Service (NTIS)

Methane and carbon dioxide are formed in landfills as wastes degrade. Molecule-for-molecule, methane is about 20 times more potent than carbon dioxide at trapping heat in the earth's atmosphere, and thus, it is the methane emissions from landfills that ar...

D. Jones H. Hilger J. Bogner J. Oliver

2009-01-01

195

Evaluation of enteric methane prediction equations for dairy cows used in whole farm models  

Microsoft Academic Search

The importance of evaluating greenhouse gas (GHG) emissions from dairy cows within the whole farm setting is being realized as more important than evaluating these emissions in isolation. Current whole farm models aimed at evaluating GHG emissions make use of simple regression equations to predict enteric methane (CH4) production. The objective of the current paper is to evaluate the performance

J. L. Ellis; A. Bannink; E. Kebreab; J. Dijkstra

2010-01-01

196

Wetland methane emissions during the Last Glacial Maximum estimated from PMIP2 simulations: Climate, vegetation, and geographic controls  

Microsoft Academic Search

It is an open question to what extent wetlands contributed to the interglacial-glacial decrease in atmospheric methane concentration. Here we estimate methane emissions from glacial wetlands, using newly available PMIP2 simulations of the Last Glacial Maximum (LGM) climate from coupled atmosphere-ocean and atmosphere-ocean-vegetation models. These simulations apply improved boundary conditions resulting in better agreement with paleoclimatic data than earlier PMIP1

S. L. Weber; A. J. Drury; W. H. J. Toonen; M. van Weele

2010-01-01

197

Global annual methane emission rate derived from its current atmospheric mixing ratio and estimated lifetime  

NASA Astrophysics Data System (ADS)

We use the estimated lifetime of methane (CH4), the current methane concentration, and its annual growth rate to calculate the global methane emission rate. The upper and lower limits of the annual global methane emission rate, depending on loss of CH4 into the stratosphere and methane consuming bacteria, amounts to 648.0 Mt a-1 and 608.0 Mt a-1. These values are in reasonable agreement with satellite and with much more accurate in situ measurements of methane. We estimate a mean tropospheric and mass-weighted temperature related to the reaction rate and employ a mean OH-concentration to calculate a mean methane lifetime. The estimated atmospheric lifetime of methane amounts to 8.28 years and 8.84 years, respectively. In order to improve the analysis a realistic 3D-calculations should be performed.

Sonnemann, G. R.; Grygalashvyly, M.

2014-03-01

198

Quantifying the relative contribution of natural gas fugitive emissions to total methane emissions in Colorado, Utah, and Texas using mobile ?13CH4 analysis  

NASA Astrophysics Data System (ADS)

Fugitive emissions of methane into the atmosphere are a major concern facing the natural gas production industry. Because methane is more energy-rich than coal per kg of CO2 emitted into the atmosphere, it represents an attractive alternative to coal for electricity generation, provided that the fugitive emissions of methane are kept under control. A key step in assessing these emissions in a given region is partitioning the observed methane emissions between natural gas fugitive emissions and other sources of methane, such as from landfills or agricultural activities. One effective method for assessing the contribution of these different sources is stable isotope analysis, using the ?13CH4 signature to distinguish between natural gas and landfills or ruminants. We present measurements of mobile field ?13CH4 using a spectroscopic stable isotope analyzer based on cavity ringdown spectroscopy, in three intense natural gas producing regions of the United States: the Denver-Julesburg basin in Colorado, the Uintah basin in Utah, and the Barnett Shale in Texas. Mobile isotope measurements of individual sources and in the nocturnal boundary layer have been combined to establish the fraction of the observed methane emissions that can be attributed to natural gas activities. The fraction of total methane emissions in the Denver-Julesburg basin attributed to natural gas emissions is 78 +/- 13%. In the Uinta basin, which has no other significant sources of methane, the fraction is 96% +/- 15%. In addition, results from the Barnett shale are presented, which includes a major urban center (Dallas / Ft. Worth). Methane emissions in this region are spatially highly heterogeneous. Spatially-resolved isotope and concentration measurements are interpreted using a simple emissions model to arrive at an overall isotope ratio for the region. (left panel) Distribution of oil and gas well pads (yellow) and landfills (blue) in the Dallas / Ft. Worth area. Mobile nocturnal measurements of methane are shown in red, indicating a strong degree of source heterogeneity. (right panel) Histogram of individual isotopic source signatures, showing distinct signatures for landfills (red) and oil and gas sources (green).

Rella, C.; Crosson, E.; Petron, G.; Sweeney, C.; Karion, A.

2013-12-01

199

Towards an inventory of methane emissions from manure management that is responsive to changes on Canadian farms  

NASA Astrophysics Data System (ADS)

Methane emissions from manure management represent an important mitigation opportunity, yet emission quantification methods remain crude and do not contain adequate detail to capture changes in agricultural practices that may influence emissions. Using the Canadian emission inventory methodology as an example, this letter explores three key aspects for improving emission quantification: (i) obtaining emission measurements to improve and validate emission model estimates, (ii) obtaining more useful activity data, and (iii) developing a methane emission model that uses the available farm management activity data. In Canada, national surveys to collect manure management data have been inconsistent and not designed to provide quantitative data. Thus, the inventory has not been able to accurately capture changes in management systems even between manure stored as solid versus liquid. To address this, we re-analyzed four farm management surveys from the past decade and quantified the significant change in manure management which can be linked to the annual agricultural survey to create a continuous time series. In the dairy industry of one province, for example, the percentage of manure stored as liquid increased by 300% between 1991 and 2006, which greatly affects the methane emission estimates. Methane emissions are greatest from liquid manure, but vary by an order of magnitude depending on how the liquid manure is managed. Even if more complete activity data are collected on manure storage systems, default Intergovernmental Panel on Climate Change (IPCC) guidance does not adequately capture the impacts of management decisions to reflect variation among farms and regions in inventory calculations. We propose a model that stays within the IPCC framework but would be more responsive to farm management by generating a matrix of methane conversion factors (MCFs) that account for key factors known to affect methane emissions: temperature, retention time and inoculum. This MCF matrix would be populated using a mechanistic emission model verified with on-farm emission measurements. Implementation of these MCF values will require re-analysis of farm surveys to quantify liquid manure emptying frequency and timing, and will rely on the continued collection of this activity data in the future. For model development and validation, emission measurement campaigns will be needed on representative farms over at least one full year, or manure management cycle (whichever is longer). The proposed approach described in this letter is long-term, but is required to establish baseline data for emissions from manure management systems. With these improvements, the manure management emission inventory will become more responsive to the changing practices on Canadian livestock farms.

VanderZaag, A. C.; MacDonald, J. D.; Evans, L.; Vergé, X. P. C.; Desjardins, R. L.

2013-09-01

200

Three-dimensional model synthesis of the global methane cycle  

Microsoft Academic Search

A synthesis of the global methane cycle is presented to attempt to generate an accurate global methane budget. Methane-flux measurements, energy data, and agricultural statistics are merged with databases of land-surface characteristics and anthropogenic activities. The sources and sinks of methane are estimated based on atmospheric methane composition and variations, and a global 3D transport model simulates the corresponding atmospheric

I. Fung; M. Prather; J. John; J. Lerner; E. Matthews; L. P. Steele; P. J. Fraser

1991-01-01

201

Biotic landfill cover treatments for mitigating methane emissions.  

PubMed

Landfill methane (CH4) emissions have been cited as one of the anthropogenic gas releases that can and should be controlled to reduce global climate change. This article reviews recent research that identifies ways to enhance microbial consumption of the gas in the aerobic portion of a landfill cover. Use of these methods can augment CH4 emission reductions achieved by gas collection or provide a sole means to consume CH4 at small landfills that do not have active gas collection systems. Field studies indicate that high levels of CH4 removal can be achieved by optimizing natural soil microbial processes. Further, during biotic conversion, not all of the CH4 carbon is converted to carbon dioxide (CO2) gas and released to the atmosphere; some of it will be sequestered in microbial biomass. Because biotic covers can employ residuals from other municipal processes, financial benefits can also accrue from avoided costs for residuals disposal. PMID:12733810

Hilgeri, Helene; Humer, Marion

2003-05-01

202

Modeling of methane release from intact coal  

SciTech Connect

Development of percolating clusters when loading samples of a geomaterial that is hierarchically and stochastically heterogeneous is modeled. The conditions are analyzed for propagation of crack under pressure of methane in the transition phase from a bound state into a free one on the faces of the growing crack in coal.

Odintsev, V.N. [Russian Academy of Science, Moscow (Russian Federation)

2005-09-15

203

Methane Emissions from the Natural Gas Industry. Volume 3. General Methodology.  

National Technical Information Service (NTIS)

The report describes the methods used to quantify the annual methane emissions from the natural gas industry. The methods include the general methods used for emission factor measurement, activity factor quantification, and extrapolation.

M. R. Harrison H. J. Williamson L. M. Campbell

1996-01-01

204

Methane emissions from rice fields amended with biogas slurry and farm yard manure  

Microsoft Academic Search

In an experiment on methane-emission measurements from rice fields amended with urea, biogas spent slurry (BSS) + urea, and farm yard manure (FYM) + urea, three distinctive peaks in the methane emissions were observed at 15, 46, and 69 days after transplanting (DAT) due to the availability of readily degradable C-sources. In all cases, the highest peak was at 69

Goutam Debnath; M. C. Jain; Sushil Kumar; K. Sarkar; Suresh K. Sinha

1996-01-01

205

A GLOBAL METHANE EMISSIONS PROGRAM FOR LANDFILLS, COAL MINES, AND NATURAL GAS SYSTEMS  

EPA Science Inventory

The paper gives the scope and methodology of EPA/AEERL's methane emissions studies and discloses data accumulated thus far in the program. Anthropogenic methane emissions are a principal focus in AEERL's global climate research program, including three major sources: municipal so...

206

Methane emissions from a freshwater marsh in response to experimentally simulated global warming and nitrogen enrichment  

Microsoft Academic Search

We determined methane (CH4) emissions in a field enclosure experiment in a littoral freshwater marsh under the influence of experimentally simulated warming and enhanced nitrogen deposition. Methane emissions by ebullition from the marsh composed of Phragmites australis were measured with funnel traps deployed in a series of enclosures for two 3 week periods. Diffusive fluxes were estimated on the basis

Sabine Flury; Daniel F. McGinnis; Mark O. Gessner

2010-01-01

207

Atmospheric Impact of Large Methane Emissions and the Gulf Oil Spill  

NASA Astrophysics Data System (ADS)

A vast quantity of a highly potent greenhouse gas, methane, is locked in the solid phase as methane clathrates in ocean sediments and underneath permafrost regions. Clathrates are ice-like deposits containing a mixture of water and gas (mostly methane) which are stable under high pressure and low temperatures. Current estimates are about 1600 - 2000 GtC present in oceans and about 400GtC in Arctic permafrost (Archer et al. 2009). This is about 4000 times that of current annual emissions. In a warming climate, increase in ocean temperatures could rapidly destabilize the geothermal gradient which in turn could lead to dissociation of the clathrates and release of methane into the ocean and subsequently into the atmosphere as well. This could result in a number of effects including strong greenhouse heating, increased surface ozone, reduced stratospheric ozone, and intensification of the Arctic ozone hole. Many of the effects in the chemistry of the atmosphere are non-linear. In this paper, we present a parametric study of the effect of large scale methane release to the atmosphere. To that end we use the CESM (Community Earth System Model) version 1 with fully active coupled atmosphere-ocean-land model together with super-fast atmospheric chemistry module to simulate the response to increasing CH4 by 2, 3, 10 and 100 times that of the present day. We have also conducted a parametric study of the possible impact of gaseous emissions from the oil spill in the Gulf of Mexico, which is a proxy for future clathrate releases. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Bhattacharyya, S.; Cameron-Smith, P. J.; Bergmann, D. J.

2010-12-01

208

On the possible methane emissions from the East Siberian Arctic Seas  

NASA Astrophysics Data System (ADS)

Global changes in the Arctic occur in the growth of average air temperatures, rapidly melting ice on land and sea, and underwater permafrost degradation. The extensive Arctic Shelf can play an important role in methane cycling because of the huge storage of organic matter buried in permafrost, which can be involved in the modern biogeochemical cycles under warming. The dissolved methane concentrations in the East Siberian Arctic Shelf water during summers of 2003 to 2008 show a widespread oversaturation in large spatial scales [1]. The horizontal and vertical methane distributions in the observational data indicate a sedimentary source which is likely associated with thawing of the underwater permafrost and release of gas from the shallow Arctic gas hydrate. Based on the regional model the Arctic Ocean-North Atlantic, developed in ICMMG SB RAS [2], the variability of the Arctic Ocean water masses state was simulated for the period from 1948 to 2010. The model was driven by atmospheric data from the CORE-2 and NCEP/NCAR reanalysis. The analysis of the thermohaline characteristics of the East Siberia Shelf water in the model run showed the positive trend in the bottom temperature, which is in agreement with the observational data. Temperature increase of the bottom waters can lead to the thawing of the frozen bottom sediments and the release of additional amount of methane from gas hydrates. Assuming the increase in the gas permeability of the perennial frozen sediment caused by climate change, the numerical simulation of the dissolved methane transport from the bottom reservoirs in the shelf water was performed. A three-dimensional mathematical model of the dissolved gas transport by the ocean currents with the parameterization of the oxidation process was used for the quantitative evaluation of the scale of a possible methane flux from the submarine sources. According to our numerical results obtained in the period from 2002 to 2010, the total methane emission in the eastern Arctic shelf waters can be estimated from 16 to 54 kilotons per year, which is two orders lower than the estimates given in [1]. Acknowledgements: This work is supported by the IP SB RAS #109, RFBR # 11-05-01075- projects. 1. Shakhova N., Semiletov I., Salyuk A., Yusupov V., Kosmach D., Gustafsson O. Extensive methane venting to the atmosphere from sediments of the East Siberian Arctic Shelf // Science. 2010. # 327. P. 1246-1250. 2. Golubeva E.N., Platov G.A. On improving the simulation of Atlantic Water circulation in the Arctic Ocean // J.Geoph.Res. - 2007. - Vol. 112. - C04S05. - doi:10.1029/2006JC003734.

Malakhova, Valentina; Golubeva, Elena

2013-04-01

209

40 CFR Table W - 7 of Subpart W of Part 98-Default Methane Emission Factors for Natural Gas Distribution  

Code of Federal Regulations, 2013 CFR

...98-Default Methane Emission Factors for Natural Gas Distribution W Table W Protection...GREENHOUSE GAS REPORTING Petroleum and Natural Gas Systems Definitions. Pt...Default Methane Emission Factors for Natural Gas Distribution Natural gas...

2013-07-01

210

Natural gas fugitive emissions rates constrained by global atmospheric methane and ethane.  

PubMed

The amount of methane emissions released by the natural gas (NG) industry is a critical and uncertain value for various industry and policy decisions, such as for determining the climate implications of using NG over coal. Previous studies have estimated fugitive emissions rates (FER)-the fraction of produced NG (mainly methane and ethane) escaped to the atmosphere-between 1 and 9%. Most of these studies rely on few and outdated measurements, and some may represent only temporal/regional NG industry snapshots. This study estimates NG industry representative FER using global atmospheric methane and ethane measurements over three decades, and literature ranges of (i) tracer gas atmospheric lifetimes, (ii) non-NG source estimates, and (iii) fossil fuel fugitive gas hydrocarbon compositions. The modeling suggests an upper bound global average FER of 5% during 2006-2011, and a most likely FER of 2-4% since 2000, trending downward. These results do not account for highly uncertain natural hydrocarbon seepage, which could lower the FER. Further emissions reductions by the NG industry may be needed to ensure climate benefits over coal during the next few decades. PMID:24945600

Schwietzke, Stefan; Griffin, W Michael; Matthews, H Scott; Bruhwiler, Lori M P

2014-07-15

211

Infrared radiation models for atmospheric methane  

NASA Technical Reports Server (NTRS)

Mutually consistent line-by-line, narrow-band and broad-band infrared radiation models are presented for methane, a potentially important anthropogenic trace gas within the atmosphere. Comparisons of the modeled band absorptances with existing laboratory data produce the best agreement when, within the band models, spurious band intensities are used which are consistent with the respective laboratory data sets, but which are not consistent with current knowledge concerning the intensity of the infrared fundamental band of methane. This emphasizes the need for improved laboratory band absorptance measurements. Since, when applied to atmospheric radiation calculations, the line-by-line model does not require the use of scaling approximations, the mutual consistency of the band models provides a means of appraising the accuracy of scaling procedures. It is shown that Curtis-Godson narrow-band and Chan-Tien broad-band scaling provide accurate means of accounting for atmospheric temperature and pressure variations.

Cess, R. D.; Kratz, D. P.; Caldwell, J.; Kim, S. J.

1986-01-01

212

Deploying Methane Bubble Traps at Varying Lake Depths to Validate Bubble Dissolution Models  

NASA Astrophysics Data System (ADS)

Methane is a potent greenhouse gas, and understanding environmental methane cycles is critical both to developing accurate estimates of current methane emission rates and to modeling how cycles may respond to climate change. While there are many natural sources of methane, bubbling from lake sediments, or ebullition, is considered an important emission pathway. Ebullition can transport methane directly to the atmosphere, bypassing potential chemical or biological degradation in the water column. Existing bubble models predict some methane dissolution from rising bubbles, though dissolution estimates depend on the particular equations chosen to parameterize bubble rise velocity and gas transfer rates. To test current bubble dissolution models we installed a series of bubble traps at multiple depths in Upper Mystic Lake near Boston, Massachusetts. Traps gathered bubbles continuously during the summer of 2013 and were periodically emptied for gas volume measurements and chemical composition analysis. The gathered trap data demonstrated that surface traps have a significantly reduced bubble volume and methane fraction when compared with lake-bottom traps. This difference allows us to quantify the amount of methane dissolved in the water column due to ebullition. Preliminary data suggest that dissolution from bubbles could account for approximately 5% of the previously observed hypolimnetic methane accumulation in Upper Mystic Lake. Bubble methane contents in surface traps are consistent with average bubble sizes in the 3-6 mm diameter range based on the bubble models of McGinnis et al, 2006, and suggest that on the order of 50% of methane released by ebullition in this lake is dissolved before reaching the atmosphere. Data also indicates that careful corrections may be needed to account for small amounts of potential gas losses associated with dissolution at the gas/water interface within the traps. Using the gathered data to understand bubble size distributions, calculate methane dissolution quantities, and to calibrate simultaneous sonar studies of ebullition (Scandella et al) will help us develop a detailed lake-wide methane budget. In turn, understanding how ebullition impacts lake-wide methane cycling can lead to better predictive models of lake methane emissions under different climate change scenarios.

Delwiche, K.; Scandella, B.; Juanes, R.; Ruppel, C. D.; Hemond, H.

2013-12-01

213

Efficiency of the benthic filter: Biological control of the emission of dissolved methane from sediments containing shallow gas hydrates at Hydrate Ridge  

Microsoft Academic Search

In marine sedimentary environments, microbial methanotrophy represents an important sink for methane before it leaves the seafloor and enters the water column. Using benthic observatories in conjunction with numerical modeling of pore water gradients, we investigated seabed methane emission rates at cold seep sites with underlying gas hydrates at Hydrate Ridge, Cascadia margin. Measurements were conducted at three characteristic sites

S. Sommer; O. Pfannkuche; P. Linke; R. Luff; J. Greinert; M. Drews; S. Gubsch; M. Pieper; M. Poser; T. Viergutz

2006-01-01

214

Quantification of methane emission rates from coal mine ventilation shafts using airborne remote sensing data  

NASA Astrophysics Data System (ADS)

The quantification of emissions of the greenhouse gas methane is essential for attributing the roles of anthropogenic activity and natural phenomena in global climate change. Our current measurement systems and networks, whilst having improved during the last decades, are deficient in many respects. For example, the emissions from localised and point sources such as landfills or fossil fuel exploration sites are not readily assessed. A tool developed to better understand point sources of the greenhouse gases carbon dioxide and methane is the optical remote sensing instrument MAMAP (Methane airborne MAPper), operated from aircraft. After a recent instrument modification, retrievals of the column-averaged dry air mole fractions for methane XCH4 (or for carbon dioxide XCO2) derived from MAMAP data have a precision of about 0.4% or better and thus can be used to infer emission rate estimates using an optimal estimation inverse Gaussian plume model or a simple integral approach. CH4 emissions from two coal mine ventilation shafts in western Germany surveyed during the AIRMETH 2011 measurement campaign are used as examples to demonstrate and assess the value of MAMAP data for quantifying CH4 from point sources. While the knowledge of the wind is an important input parameter in the retrieval of emissions from point sources and is generally extracted from models, additional information from a turbulence probe operated on-board the same aircraft was utilised to enhance the quality of the emission estimates. Although flight patterns were optimised for remote sensing measurements, data from an in situ analyser for CH4 were found to be in good agreement with retrieved dry columns of CH4 from MAMAP and could be used to investigate and refine underlying assumptions for the inversion procedures. With respect to the total emissions of the mine at the time of the overflight, the inferred emission rate of 50.4 kt CH4 yr-1 has a difference of less than 1% compared to officially reported values by the mine operators, while the uncertainty, which reflects variability of the sources and conditions as well as random and systematic errors, is about ±13.5%.

Krings, T.; Gerilowski, K.; Buchwitz, M.; Hartmann, J.; Sachs, T.; Erzinger, J.; Burrows, J. P.; Bovensmann, H.

2013-01-01

215

Tank bromeliad - a natural model ecosystem for methane cycling research  

NASA Astrophysics Data System (ADS)

Tank bromeliads are common epiphytes throughout neotropical forest ecosystems. They are relatively small discrete habitats for terrestrial and aquatic macro- and microorganisms and naturally replicated. Their tanks effectively collect leaf litter and water and harbor a diverse microbial community. Up to several thousands of these tank bromeliads per hectare of tropical forest create a unique wetland ecosystem responsible for significant methane emissions. In a field study in tropical montane forests of southern Ecuador we sampled tank bromeliads of different species, size and canopy height and found that tank water availability controlled community composition of methanogenic archaea, determined by molecular analysis of the archaeal 16S rRNA genes. We set up a greenhouse experiment to investigate drying and re-wetting effects on microbial community composition and methanogenesis. Additionally, we conducted 13-CH-4 and 13-CO-2 labeling studies to investigate potential interaction of plant and microbial metabolism during methane cycling in tank bromeliads. Drying resulted in rapid change of the microbial community composition. The relative abundance of acetoclastic methanogens increased and that of hydrogenotrophic methanogens decreased with decreasing tank water availability confirming our field observations. Labeling studies showed that carbon was released from the plant into the tank supporting methanogenesis and that tank-produced methane was ventilated through the bromeliad leaf structure into the atmosphere which is analogous to the rhizosphere environment of wetland ecosystems. The bromeliad ecosystem may therefore provide a natural model to study how environmental changes and plant-microbe interactions drive methane cycling in aquatic-terrestrial ecosystems.

Martinson, Guntars; Brandt, Franziska; Conrad, Ralf

2014-05-01

216

Detection of marine methane emissions with AVIRIS band ratios  

NASA Astrophysics Data System (ADS)

The relative source contributions of methane (CH4) have high uncertainty, creating a need for local-scale characterization in concert with global satellite measurements. However, efforts towards methane plume imaging have yet to provide convincing results for concentrated sources. Although atmospheric CH4 mapping did not motivate the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) design, recent studies suggest its potential for studying concentrated CH4 sources such as the Coal Oil Point (COP) seep field (˜0.015 Tg CH4 yr-1) offshore Santa Barbara, California. In this study, we developed a band ratio approach on high glint COP AVIRIS data and demonstrate the first successful local-scale remote sensing mapping of natural atmospheric CH4 plumes. Plume origins closely matched surface and sonar-derived seepage distributions, with plume characteristics consistent with wind advection. Imaging spectrometer data may also be useful for high spatial-resolution characterization of concentrated, globally-significant CH4 emissions from offshore platforms and cattle feedlots.

Bradley, Eliza S.; Leifer, Ira; Roberts, Dar A.; Dennison, Philip E.; Washburn, Libe

2011-05-01

217

Mitigation of methane emission from an old unlined landfill in Klintholm, Denmark using a passive biocover system.  

PubMed

Methane generated at landfills contributes to global warming and can be mitigated by biocover systems relying on microbial methane oxidation. As part of a closure plan for an old unlined landfill without any gas management measures, an innovative biocover system was established. The system was designed based on a conceptual model of the gas emission patterns established through an initial baseline study. The study included construction of gas collection trenches along the slopes of the landfill where the majority of the methane emissions occurred. Local compost materials were tested as to their usefulness as bioactive methane oxidizing material and a suitable compost mixture was selected. Whole site methane emission quantifications based on combined tracer release and downwind measurements in combination with several local experimental activities (gas composition within biocover layers, flux chamber based emission measurements and logging of compost temperatures) proved that the biocover system had an average mitigation efficiency of approximately 80%. The study showed that the system also had a high efficiency during winter periods with temperatures below freezing. An economic analysis indicated that the mitigation costs of the biocover system were competitive to other existing greenhouse gas mitigation options. PMID:24755356

Scheutz, Charlotte; Pedersen, Rasmus Broe; Petersen, Per Haugsted; Jørgensen, Jørgen Henrik Bjerre; Ucendo, Inmaculada Maria Buendia; Mønster, Jacob G; Samuelsson, Jerker; Kjeldsen, Peter

2014-07-01

218

Preliminary results from measurement of methane at Gosan, Jeju Island, Korea for understanding emissions in East Asia  

NASA Astrophysics Data System (ADS)

Importance of methane (CH4) to the global biogeochemical cycle and climate change has been well documented, and while the total global methane emissions are relatively well known, the strength of each source component and their trends are not, due to the varied biological and anthropogenic sources of emissions. This is especially true in East Asia, where strong expected emissions of CH4 from fossil fuel mining and burning as well as rice agriculture remain less understood. In this study, we present atmospheric measurements of methane and preliminary analysis of the results. Measurement site for this study is at Gosan, a remote background site located on Jeju Island, Korea. Due to its central location in East Asia, monitoring of both background and pollution from the surrounding regions is possible, thus ideal for monitoring methane emissions in East Asia. To facilitate high-quality continuous measurements, an automated measurement system with a GC-FID has been created and tested at Seoul National University. Identification of the dominant CH4 emission sources could be better understood by analyzing correlation with other anthropogenically and biogenically emitted compounds such as CO (important indicator for fossil fuel burning) and chlorinated compounds (emitted from biomass burning and the use of coal). Advanced air mass transport modeling will also be used to analyze different emission patterns by region.

Lee, E.; Kim, J.; Ahn, K.; Park, M.; Kim, K.

2010-12-01

219

Methane, carbon dioxide, and nitrous oxide emissions from septic tank systems.  

PubMed

Emissions of CH4, CO2, and N2O from conventional septic tank systems are known to occur, but there is a dearth of information as to the extent. Mass emission rates of CH4, CO2, and N2O, as measured with a modified flux chamber approach in eight septic tank systems, were determined to be 11, 33.3, and 0.005 g capita(-1) day(-1), respectively, in this research. Existing greenhouse gas (GHG) emission models based on BOD (biochemical oxygen demand) loading have estimated methane emissions to be as high as 27.1 g CH4 capita(-1) day(-1), more than twice the value measured in our study, and concluded that septic tanks are potentially significant sources of GHGs due to the large number of systems currently in use. Based on the measured CH4 emission value, a revised CH4 conversion factor of 0.22 (compared to 0.5) for use in the emissions models is suggested. Emission rates of CH4, CO2, and N2O were also determined from measurements of gas concentrations and flow rates in the septic vent system and were found to be 10.7, 335, and 0.2 g capita(-1)day(-1), respectively. The excellent agreement in the CH4 emission rates between the flux chamber and the vent values indicates the dominant CH4 source is the septic tank. PMID:21381675

Diaz-Valbuena, Libia R; Leverenz, Harold L; Cappa, Christopher D; Tchobanoglous, George; Horwath, William R; Darby, Jeannie L

2011-04-01

220

Characterizing Spatiotemporal Dynamics of Methane Emissions from Rice Paddies in Northeast China from 1990 to 2010  

PubMed Central

Background Rice paddies have been identified as major methane (CH4) source induced by human activities. As a major rice production region in Northern China, the rice paddies in the Three-Rivers Plain (TRP) have experienced large changes in spatial distribution over the recent 20 years (from 1990 to 2010). Consequently, accurate estimation and characterization of spatiotemporal patterns of CH4 emissions from rice paddies has become an pressing issue for assessing the environmental impacts of agroecosystems, and further making GHG mitigation strategies at regional or global levels. Methodology/Principal Findings Integrating remote sensing mapping with a process-based biogeochemistry model, Denitrification and Decomposition (DNDC), was utilized to quantify the regional CH4 emissions from the entire rice paddies in study region. Based on site validation and sensitivity tests, geographic information system (GIS) databases with the spatially differentiated input information were constructed to drive DNDC upscaling for its regional simulations. Results showed that (1) The large change in total methane emission that occurred in 2000 and 2010 compared to 1990 is distributed to the explosive growth in amounts of rice planted; (2) the spatial variations in CH4 fluxes in this study are mainly attributed to the most sensitive factor soil properties, i.e., soil clay fraction and soil organic carbon (SOC) content, and (3) the warming climate could enhance CH4 emission in the cool paddies. Conclusions/Significance The study concluded that the introduction of remote sensing analysis into the DNDC upscaling has a great capability in timely quantifying the methane emissions from cool paddies with fast land use and cover changes. And also, it confirmed that the northern wetland agroecosystems made great contributions to global greenhouse gas inventory.

Zhang, Yuan; Su, Shiliang; Zhang, Feng; Shi, Runhe; Gao, Wei

2012-01-01

221

Atmospheric observations of Arctic Ocean methane emissions up to 82° north  

NASA Astrophysics Data System (ADS)

Uncertainty in the future atmospheric burden of methane, a potent greenhouse gas, represents an important challenge to the development of realistic climate projections. The Arctic is home to large reservoirs of methane, in the form of permafrost soils and methane hydrates, which are vulnerable to destabilization in a warming climate. Furthermore, methane is produced in the surface ocean and the surface waters of the Arctic Ocean are supersaturated with respect to methane. However, the fate of this oceanic methane is uncertain. Here, we use airborne observations of methane to assess methane efflux from the remote Arctic Ocean, up to latitudes of 82°north. We report layers of increased methane concentrations near the surface ocean, with little or no enhancement in carbon monoxide levels, indicative of a non-combustion source. We further show that high methane concentrations are restricted to areas over open leads and regions with fractional sea-ice cover. Based on the observed gradients in methane concentration, we estimate that sea-air fluxes amount to around 2 mg d-1 m-2, comparable to emissions seen on the Siberian shelf. We suggest that the surface waters of the Arctic Ocean represent a potentially important source of methane, which could prove sensitive to changes in sea-ice cover.

Kort, E. A.; Wofsy, S. C.; Daube, B. C.; Diao, M.; Elkins, J. W.; Gao, R. S.; Hintsa, E. J.; Hurst, D. F.; Jimenez, R.; Moore, F. L.; Spackman, J. R.; Zondlo, M. A.

2012-05-01

222

Status of worldwide coal mine methane emissions and use  

Microsoft Academic Search

Underground coal mines worldwide liberate an estimated 29–41×109 m3 of methane annually, of which less than 2.3×109 m3 are used as fuel. The remaining methane is emitted to the atmosphere, representing the loss of a valuable energy resource. Methane is also a major greenhouse gas and is thus detrimental to the environment when vented to the atmosphere. Coal mine methane

Carol J Bibler; James S Marshall; Raymond C Pilcher

1998-01-01

223

Methane emissions from 20 landfills across the United States using vertical radial plume mapping.  

PubMed

Landfill fugitive methane emissions were quantified as a function of climate type and cover type at 20 landfills using US. Environmental Protection Agency (EPA) Other Test Method (OTM)-10 vertical radial plume mapping (VRPM) with tunable diode lasers (TDLs). The VRPM data were initially collected as g CH4/sec emission rates and subsequently converted to g CH4/m2/ day rates using two recently published approaches. The first was based upon field tracer releases of methane or acetylene and multiple linear regression analysis (MLRM). The second was a virtual computer model that was based upon the Industrial Source Complex (ISC3) and Pasquill plume stability class models (PSCMs). Calculated emission results in g CH4/m2/day for each measured VRPM with the two approaches agreed well (r2 = 0.93). The VRPM data were obtained from the working face, temporary soil, intermediate soil, and final soil or synthetic covers. The data show that methane emissions to the atmosphere are a function of climate and cover type. Humid subtropical climates exhibited the highest emissions for all cover types at 207, 127, 102, and 32 g CH4/m2/day, for working face (no cover), temporary, intermediate, and final cover, respectively. Humid continental warm summers showed 67, 51, and 27 g CH4/m2/day for temporary, intermediate, and final covers. Humid continental cool summers were 135, 40, and 26 g CH4/m2/day for the working face, intermediate, and final covers. Mediterranean climates were examined for intermediate and final covers only and found to be 11 and 6 g CH4/m2/day, respectively, whereas semiarid climates showed 85, 11, 3.7, and 2.7 g CH4/m2/day for working face, temporary, intermediate, and final covers. A closed, synthetically capped landfill covered with soil and vegetation with a gas collection system in a humid continental warm summer climate gave mostly background methane readings and average emission rates of only 0.09 g CH4/m2/day flux when measurable. PMID:22442934

Goldsmith, C Douglas; Chanton, Jeffrey; Abichou, Tarek; Swan, Nathan; Green, Roger; Haters, Gary

2012-02-01

224

Effect of Carex rostrata on seasonal and interannual variability in peatland methane emissions  

NASA Astrophysics Data System (ADS)

are a large natural source of atmospheric methane (CH4), and the sedge Carex rostrata plays a critical role in the production, oxidation, and transport of CH4 in these systems. This 4 year clipping experiment examined the changes in CH4 emissions from a temperate peatland after removing all aboveground C. rostrata biomass. Methane fluxes, dissolved CH4, and environmental variables were measured during spring, summer, and fall from 2008 to 2011. Clipping and removing the C. rostrata leaves and stems caused an immediate decrease in CH4 emissions that persisted over 4 years of this study. There was a strong seasonal trend in CH4 flux, with the largest treatment effects occurring during the fall months when the sedges were senescing. As expected, there was a strong positive correlation between C. rostrata green-leaf area and CH4 flux, implying that the presence of C. rostrata increases CH4 emissions from this peatland. Large interannual variability in vegetation distribution and biomass, water table depth, and temperature was observed in this study, indicating the importance of multiyear studies for understanding the interactions among these factors to determine how they could be incorporated into biogeochemical models to predict CH4 emissions under changing environmental conditions.

Noyce, Genevieve L.; Varner, Ruth K.; Bubier, Jill L.; Frolking, Steve

2014-01-01

225

Importance of the autumn overturn and anoxic conditions in the hypolimnion for the annual methane emissions from a temperate lake.  

PubMed

Changes in the budget of dissolved methane measured in a small temperate lake over 1 year indicate that anoxic conditions in the hypolimnion and the autumn overturn period represent key factors for the overall annual methane emissions from lakes. During periods of stable stratification, large amounts of methane accumulate in anoxic deep waters. Approximately 46% of the stored methane was emitted during the autumn overturn, contributing ?80% of the annual diffusive methane emissions to the atmosphere. After the overturn period, the entire water column was oxic, and only 1% of the original quantity of methane remained in the water column. Current estimates of global methane emissions assume that all of the stored methane is released, whereas several studies of individual lakes have suggested that a major fraction of the stored methane is oxidized during overturns. Our results provide evidence that not all of the stored methane is released to the atmosphere during the overturn period. However, the fraction of stored methane emitted to the atmosphere during overturn may be substantially larger and the fraction of stored methane oxidized may be smaller than in the previous studies suggesting high oxidation losses of methane. The development or change in the vertical extent and duration of the anoxic hypolimnion, which can represent the main source of annual methane emissions from small lakes, may be an important aspect to consider for impact assessments of climate warming on the methane emissions from lakes. PMID:24873684

Encinas Fernández, Jorge; Peeters, Frank; Hofmann, Hilmar

2014-07-01

226

Methane emissions from tank bromeliads in neotropical forests  

NASA Astrophysics Data System (ADS)

Methane is a potent greenhouse gas. Methane concentrations above neotropical forests-the tropical forests found in Mexico, Central America, South America and the Caribbean-are high according to space-borne observations. However, the source of the methane is uncertain. Here, we measure methane fluxes from tank bromeliads-a common group of herbaceous plants in neotropical forests that collect water in tank-like structures-using vented static chambers. We sampled 167 bromeliads in the Ecuadorian Andes, and found that all of them emitted methane. We found a diverse community of methane-producing archaea within the water-containing tanks, suggesting that the tanks served as the source of the methane. Indeed, tank water was supersaturated with methane, and 13C-labelled methane added to tank water was emitted though the leaves. We suggest that the bromeliad tanks form a wetland environment conducive to methane production. In conjunction with other wetlands hidden beneath the copy surface, bromeliads may help to explain the inexplicably high methane levels observed over neotropical forests.

Martinson, Guntars O.; Werner, Florian A.; Scherber, Christoph; Conrad, Ralf; Corre, Marife D.; Flessa, Heiner; Wolf, Katrin; Klose, Melanie; Gradstein, S. Robbert; Veldkamp, Edzo

2010-11-01

227

Development of methane emission factors for Indian paddy fields and estimation of national methane budget.  

PubMed

A state-wise assessment of methane (CH(4)) budget for Indian paddies, based on a decadal measurement data across India is presented for the calendar year (CY) 1994, the base year for India's Initial National Communication (NATCOM) to the United Nations Framework Convention on Climate Change (UNFCCC), along with national trend from CY 1979 to 2006. The NATCOM CH(4) emission factors (EFs) for Indian paddy cultivation areas, generally having less than 0.7% of soil organic carbon (SOC), have been estimated as 17.48+/-4 g m(-2) for irrigated continuously flooded (IR-CF), 6.95+/-1.86 g m(-2) for rain-fed drought prone (RF-DP), 19+/-6 g m(-2) for rain-fed flood prone (RF-FP) and deep-water (DW), 6.62+/-1.89 g m(-2) for irrigated intermittently flooded single aeration (IR-IF-SA) and 2.01+/-1.49 g m(-2) for IR-IF multiple aeration (MA) paddy water regimes. The state-wise study for 1994 has indicated national CH(4) budget estimate of 4.09+/-1.19 Tg y(-1) and the trend from 1979 to 2006 was in the range of 3.62+/-1 to 4.09+/-1.19 Tg y(-1). Four higher emitting or "hot spot" states (West Bengal, Bihar, Madhya Pradesh and Uttar Pradesh) have accounted for 53.9% of total CH(4) emission with RF-FP paddy water regime as the major contributor. CH(4) emissions were enhanced by factors such as SOC ( approximately 1.5 times due to increase in SOC by approximately 1.8 times), paddy cultivars (approximately 1.5 times), age of seedlings (approximately 1.4 times), and seasons (approximately 1.8 times in Kharif or monsoon than in Rabi or winter season). PMID:18996564

Gupta, Prabhat K; Gupta, Vandana; Sharma, C; Das, S N; Purkait, N; Adhya, T K; Pathak, H; Ramesh, R; Baruah, K K; Venkatratnam, L; Singh, Gulab; Iyer, C S P

2009-01-01

228

Baseline study of methane emission from anaerobic ponds of palm oil mill effluent treatment.  

PubMed

The world currently obtains its energy from the fossil fuels such as oil, natural gas and coal. However, the international crisis in the Middle East, rapid depletion of fossil fuel reserves as well as climate change have driven the world towards renewable energy sources which are abundant, untapped and environmentally friendly. Malaysia has abundant biomass resources generated from the agricultural industry particularly the large commodity, palm oil. This paper will focus on palm oil mill effluent (POME) as the source of renewable energy from the generation of methane and establish the current methane emission from the anaerobic treatment facility. The emission was measured from two anaerobic ponds in Felda Serting Palm Oil Mill for 52 weeks. The results showed that the methane content was between 35.0% and 70.0% and biogas flow rate ranged between 0.5 and 2.4 L/min/m(2). Total methane emission per anaerobic pond was 1043.1 kg/day. The total methane emission calculated from the two equations derived from relationships between methane emission and total carbon removal and POME discharged were comparable with field measurement. This study also revealed that anaerobic pond system is more efficient than open digesting tank system for POME treatment. Two main factors affecting the methane emission were mill activities and oil palm seasonal cropping. PMID:16125215

Yacob, Shahrakbah; Ali Hassan, Mohd; Shirai, Yoshihito; Wakisaka, Minato; Subash, Sunderaj

2006-07-31

229

Mitigation of methane emissions from rice fields: Possible adverse effects of incorporated rice straw  

NASA Astrophysics Data System (ADS)

Increased world demand for rice production may lead to an increase in methane emission to the atmosphere and future global warming. One suggested way to reduce methane emission is to discourage the practice of incorporating previous crop residue prior to planting rice, since the residue may enhance methane emission from flooded rice fields. This concept is supported by data from a 2-year study of flooded rice fields on two different soil types in Texas. In 1990, rice stubble from 1989 was incorporated into both soils. Seasonal methane emission from a Lake Charles clay field increased from 15.9 g m-2 in 1989 to 31.0 g m-2 in 1990. In the Beaumont clay field, seasonal methane emission increased from 4.5 to 11.4 g m-2. While methane emission increased between 1989 and 1990, grain yield dropped by 2100 and 840 kg ha-1 in the Lake Charles and Beaumont fields, respectively. Visual inspection at harvest indicated that the 1990 rice yield decrease resulted from grain abortion, presumably caused by the rice cultivar's sensitivity to soil anaerobiosis. The calculated amount of organic carbon not translocated to grain was comparable to the estimated amount of organic carbon required for the increased methane emission. We hypothesize that labile carbon in straighthead susceptible rice cultivars can "leak" from roots damaged by excessively anaerobic soil and be metabolized to its equivalent in methane. These data suggest that minimizing incorporation of crop residue prior to planting can decrease methane emission from flooded rice and reduce the potential for yield loss, particularly with some cultivars and in soils with low rates of seepage and percolation.

Sass, R. L.; Fisher, F. M.; Harcombe, P. A.; Turner, F. T.

1991-09-01

230

Prediction of methane production in beef cattle within a mechanistic digestion model  

Microsoft Academic Search

\\u000a Methane is produced by ruminants as the result of microbial digestion, it represents an energy loss to the animal, and it\\u000a is also a potent greenhouse gas. Mechanistic modelling can lend insight into dietary strategies aimed at reducing methane\\u000a emissions from cattle, but require proper representation of aspects of underlying rumen fermentation and digestion. Proper\\u000a prediction of the production of

J. L. Ellis; J. Dijkstra; E. Kebreab; S. Archibeque; A. Bannink

2010-01-01

231

Comparison of first-order-decay modeled and actual field measured municipal solid waste landfill methane data.  

PubMed

The first-order decay (FOD) model is widely used to estimate landfill gas generation for emissions inventories, life cycle assessments, and regulation. The FOD model has inherent uncertainty due to underlying uncertainty in model parameters and a lack of opportunities to validate it with complete field-scale landfill data sets. The objectives of this paper were to estimate methane generation, fugitive methane emissions, and aggregated collection efficiency for landfills through a mass balance approach using the FOD model for gas generation coupled with literature values for cover-specific collection efficiency and methane oxidation. This study is unique and valuable because actual field data were used in comparison with modeled data. The magnitude and variation of emissions were estimated for three landfills using site-specific model parameters and gas collection data, and compared to vertical radial plume mapping emissions measurements. For the three landfills, the modeling approach slightly under-predicted measured emissions and over-estimated aggregated collection efficiency, but the two approaches yielded statistically equivalent uncertainties expressed as coefficients of variation. Sources of uncertainty include challenges in large-scale field measurement of emissions and spatial and temporal fluctuations in methane flow balance components (generated, collected, oxidized, and emitted methane). Additional publication of sets of field-scale measurement data and methane flow balance components will reduce the uncertainty in future estimates of fugitive emissions. PMID:23988298

Amini, Hamid R; Reinhart, Debra R; Niskanen, Antti

2013-12-01

232

Quantification of methane emission rates from coal mine ventilation shafts using airborne remote sensing data  

NASA Astrophysics Data System (ADS)

The quantification of emissions of the greenhouse gas methane is essential for attributing the roles of anthropogenic activity and natural phenomena in global climate change. Our current measurement systems and networks whilst having improved during the last decades, are deficient in many respects. For example, the emissions from localised and point sources such as landfills or fossil fuel exploration sites are not readily assessed. A tool developed to better understand point sources of the greenhouse gases carbon dioxide and methane is the optical remote sensing instrument MAMAP, operated from aircraft. After a recent instrument modification, retrievals of the column averaged dry air mole fractions for methane XCH4 (or for carbon dioxide XCO2) derived from MAMAP data, have a precision of about 0.4% or better and thus can be used to infer emission rate estimates using an optimal estimation inverse Gaussian plume model or a simple integral approach. CH4 emissions from two coal mine ventilation shafts in Western Germany surveyed during the AIRMETH 2011 measurement campaign are used as examples to demonstrate and assess the value of MAMAP data for quantifying CH4 from point sources. While the knowledge of the wind is an important input parameter in the retrieval of emissions from point sources and is generally extracted from models, additional information from a turbulence probe operated on-board the same aircraft was utilised to enhance the quality of the emission estimates. Although flight patterns were optimised for remote sensing measurements, data from an in-situ analyser for CH4 were found to be in good agreement with retrieved dry columns of CH4 from MAMAP and could be used to investigate and refine underlying assumptions for the inversion procedures. With respect to the total emissions of the mine at the time of the overflight, the inferred emission rate of 50.4 kt CH4 yr-1 has a difference of less than 1% compared to officially reported values by the mine operators, while the uncertainty, which reflects variability of the sources and conditions as well as random and systematic errors, is about ±13.5%.

Krings, T.; Gerilowski, K.; Buchwitz, M.; Hartmann, J.; Sachs, T.; Erzinger, J.; Burrows, J. P.; Bovensmann, H.

2012-10-01

233

Global methane emission from wetlands and its sensitivity to climate change  

Microsoft Academic Search

The concentration of atmospheric methane (CH4) exerts a strong influence on atmospheric chemistry and the global climate. Natural and cultivated wetlands (rice paddies) are important sources of CH4, and the extent and strength of these sources may increase as a result of global warming and extension of rice production. Emission of methane from wetlands is an ecosystem process, closely coupled

Mingkui Cao; Keith Gregson; Stewart Marshall

1998-01-01

234

Effect of application of ammonium thiosulphate on production and emission of methane in a tropical rice soil  

Microsoft Academic Search

Agricultural sources of atmospheric methane include flooded rice (Oryza sativa L.) paddies. However, certain soil nutrient management and cultural practices offer opportunities to reduce methane emissions. The effect of application of ammonium thiosulphate, a potential source of nitrogen and sulphur and also an inhibitor of nitrification and urease on methane production and emission from flooded alluvial (Typic Haplaquept) rice soil

Arun Kumar Rath; B Ramakrishnan; N Sethunathan

2002-01-01

235

Methane emissions from a freshwater marsh in response to experimentally simulated global warming and nitrogen enrichment  

NASA Astrophysics Data System (ADS)

We determined methane (CH4) emissions in a field enclosure experiment in a littoral freshwater marsh under the influence of experimentally simulated warming and enhanced nitrogen deposition. Methane emissions by ebullition from the marsh composed of Phragmites australis were measured with funnel traps deployed in a series of enclosures for two 3 week periods. Diffusive fluxes were estimated on the basis of measured CH4 concentrations and application of Fick's law. Neither diffusive nor ebullitive fluxes of methane were significantly affected by warming or nitrate enrichment, possibly because variability both within and among replicate experimental enclosures was high. Average emission rates resulted primarily from ebullition (0.2-30.3 mmol CH4 m-2 d-1), which were 4 orders of magnitude higher than estimated diffusive fluxes and were of similar importance as the coarsely estimated advective methane transport through plants. Significant correlations between dissolved oxygen and dissolved methane and ebullition flux suggest that methane release from the sediment might feed back positively on methane production by reducing dissolved oxygen in the water column and oxygen flux into the sediment. Nitrate may have a similar effect. Extrapolation of our limited data indicates that total methane fluxes from vegetated littoral zones of temperate lakes may contribute 0.5%-7% of the global natural CH4 emissions. These results emphasize the importance of freshwater marshes as sources of methane emissions to the atmosphere, even when they occupy only relatively small littoral areas. More detailed investigations are clearly needed to assess whether global warming and nitrogen deposition can have climate feedbacks by altering methane fluxes from these wetlands.

Flury, Sabine; McGinnis, Daniel F.; Gessner, Mark O.

2010-03-01

236

Rice Cultivation and Methane Emission: Documentation of Distributed Geographic Data Sets.  

National Technical Information Service (NTIS)

High-resolution global data bases on the geographic and seasonal distribution of rice cultivation and associated methane emission, compiled by Matthews et al., were archived for public use. In addition to the primary data sets identifying location, season...

E. Matthews J. John I. Fung

1994-01-01

237

Control of the Diurnal Pattern of Methane Emission from Emergent Aquatic Macrophytes by Gas Transport Mechanisms.  

National Technical Information Service (NTIS)

Methane emissions from Typha latifolia (L.) showed a large mid-morning transient peak associated with rising light levels. This peak was also associated with a steep decline in lacunal CH, concentrations near the stem base. This pattern contrasted sharply...

G. J. Whiting J. P. Chanton

1995-01-01

238

Suppression of rice methane emission by sulfate deposition in simulated acid rain  

Microsoft Academic Search

Sulfate in acid rain is known to suppress methane (CH4) emissions from natural freshwater wetlands. Here we examine the possibility that CH4 emissions from rice agriculture may be similarly affected by acid rain, a major and increasing pollution problem in Asia. Our findings suggest that acid rain rates of SO42? deposition may help to reduce CH4 emissions from rice agriculture.

Vincent Gauci; Nancy B. Dise; Graham Howell; Meaghan E. Jenkins

2008-01-01

239

Suppression of rice methane emission by sulfate deposition in simulated acid rain  

Microsoft Academic Search

Sulfate in acid rain is known to suppress methane (CH4) emissions from natural freshwater wetlands. Here we examine the possibility that CH4 emissions from rice agriculture may be similarly affected by acid rain, a major and increasing pollution problem in Asia. Our findings suggest that acid rain rates of SO4 2- deposition may help to reduce CH4 emissions from rice

Vincent Gauci; Nancy B. Dise; Graham Howell; Meaghan E. Jenkins

2008-01-01

240

Natural emissions of methane from geothermal and volcanic sources in Europe  

Microsoft Academic Search

It has recently been demonstrated that methane emission from lithosphere degassing is an important component of the natural greenhouse-gas atmospheric budget. Globally, the geological sources are mainly due to seepage from hydrocarbon-prone sedimentary basins, and subordinately from geothermal\\/volcanic fluxes. This work provides a first estimate of methane emission from the geothermal\\/volcanic component at European level.In Europe, 28 countries have geothermal

G. Etiope; T. Fridriksson; F. Italiano; W. Winiwarter; J. Theloke

2007-01-01

241

Spatial profiles of methane at the Swiss Plateau: A confrontation between measurements and emission inventories.  

NASA Astrophysics Data System (ADS)

Methane and carbon dioxide are the two most prominent greenhouse gases in the atmosphere and a detailed knowledge about their sources is essential for climate predictions (Solomon et al., 2007). The knowledge about greenhouse gas fluxes is usually merged, albeit including considerable uncertainties, to emission inventories. To increase the quality of the inventories a comparison with measurements is necessary. We evaluate the values given by a Swiss emission inventory with regard to atmospheric measurements of methane in Switzerland. Spatial profiles of carbon dioxide and methane were investigated at the Swiss Plateau during two consecutive warm and sunny summer days in July 2012. For the mobile methane and carbon dioxide measurements a LGR methane analyser and a LI-COR closed-path infrared gas analyser (IRGA) were mounted on a car together with an AIRMAR WeatherStation to track geodetic-coordinates and meteorological parameters. First results of the measurements including aerial profiles of the greenhouse gases and bin-averaged elevation profiles of methane and temperature will be presented and a highly-resolved methane emission inventory will be evaluated in comparison with the spatial profiles of atmospheric methane at the Swiss Plateau. References: Solomon, S., Qin D., et al. (Eds.) (2007) Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, 996 S. pp., Cambridge University Press, Cambridge.

Bamberger, Ines; Eugster, Werner; Buchmann, Nina

2013-04-01

242

Grape marc reduces methane emissions when fed to dairy cows.  

PubMed

Grape marc (the skins, seeds, stalk, and stems remaining after grapes have been pressed to make wine) is currently a by-product used as a feed supplement by the dairy and beef industries. Grape marc contains condensed tannins and has high concentrations of crude fat; both these substances can reduce enteric methane (CH4) production when fed to ruminants. This experiment examined the effects of dietary supplementation with either dried, pelleted grape marc or ensiled grape marc on yield and composition of milk, enteric CH4 emissions, and ruminal microbiota in dairy cows. Thirty-two Holstein dairy cows in late lactation were offered 1 of 3 diets: a control (CON) diet; a diet containing dried, pelleted grape marc (DGM); and a diet containing ensiled grape marc (EGM). The diet offered to cows in the CON group contained 14.0kg of alfalfa hay dry matter (DM)/d and 4.3kg of concentrate mix DM/d. Diets offered to cows in the DGM and EGM groups contained 9.0kg of alfalfa hay DM/d, 4.3kg of concentrate mix DM/d, and 5.0kg of dried or ensiled grape marc DM/d, respectively. These diets were offered individually to cows for 18d. Individual cow feed intake and milk yield were measured daily and milk composition measured on 4d/wk. Individual cow CH4 emissions were measured by the SF6 tracer technique on 2d at the end of the experiment. Ruminal bacterial, archaeal, fungal, and protozoan communities were quantified on the last day of the experiment. Cows offered the CON, DGM, and EGM diets, ate 95, 98, and 96%, respectively, of the DM offered. The mean milk yield of cows fed the EGM diet was 12.8kg/cow per day and was less than that of cows fed either the CON diet (14.6kg/cow per day) or the DGM diet (15.4kg/cow per day). Feeding DGM and EGM diets was associated with decreased milk fat yields, lower concentrations of saturated fatty acids, and enhanced concentrations of mono- and polyunsaturated fatty acids, in particular cis-9,trans-11 linoleic acid. The mean CH4 emissions were 470, 375, and 389g of CH4/cow per day for cows fed the CON, DGM, and EGM diets, respectively. Methane yields were 26.1, 20.2, and 21.5g of CH4/kg of DMI for cows fed the CON, DGM, and EGM diets, respectively. The ruminal bacterial and archaeal communities were altered by dietary supplementation with grape marc, but ruminal fungal and protozoan communities were not. Decreases of approximately 20% in CH4 emissions and CH4 yield indicate that feeding DGM and EGM could play a role in CH4 abatement. PMID:24952778

Moate, P J; Williams, S R O; Torok, V A; Hannah, M C; Ribaux, B E; Tavendale, M H; Eckard, R J; Jacobs, J L; Auldist, M J; Wales, W J

2014-08-01

243

Optimal estimation of North American methane emissions using GOSAT data: A contribution to the NASA Carbon Monitoring System  

NASA Astrophysics Data System (ADS)

We use methane observations from the Greenhouse Gases Observing SATellite (GOSAT) to constrain methane emissions from North America in support of the NASA Carbon Monitoring System. We apply two methods: (1) an adjoint-based 4DVAR inversion, and (2) an analytical inversion with an optimally reduced state vector enabling full characterization of the solution. The GOSAT methane retrievals are validated using aircraft data from the HIPPO campaign, and our overall 4DVAR framework is shown to compare successfully to a Lagrangian inversion of CalNex aircraft data over California. The adjoint-based method has high resolution but does not suitably characterize the information content of the data or the error in the optimized emissions. The analytical inversion is based on a Gaussian Mixture Model (GMM) to explore the actual information content of the GOSAT data by optimally reducing the dimensionality of the state vector. The Maximum A Posteriori (MAP) solution from the analytical inversion yields emission constraints consistent with the 4DVAR approach while allowing construction of the full posterior solution, averaging kernel matrix, and posterior covariance matrix in an easily parallelizable framework. We find that methane emissions from the Canadian wetlands are overestimated in current inventories and that the EDGARv4.2 anthropogenic inventory underestimates emissions over the south-central US. We will show preliminary results applying the GMM method over the duration of the GOSAT record. This method can evolve into an operational tool for monitoring of methane emissions from North America using satellite data and including characterization of uncertainties.

Turner, A. J.; Jacob, D. J.; Wecht, K.; Sulprizio, M.; Payne, V.; Santoni, G.; Wofsy, S. C.; Bowman, K. W.; Parker, R.; Boesch, H.

2013-12-01

244

On the consistency between global and regional methane emissions inferred from SCIAMACHY, TANSO-FTS, IASI and surface measurements  

NASA Astrophysics Data System (ADS)

Satellite retrievals of methane weighted atmospheric columns are assimilated within a Bayesian inversion system to infer the global and regional methane emissions and sinks for the period August 2009 to July 2010. Inversions are independently computed from three different space-borne observing systems and one surface observing system under several hypotheses for prior-flux and observation errors. Posterior methane emissions are compared and evaluated against surface mole fraction observations via a chemistry-transport model. Apart from SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CartograpHY), the simulations agree fairly well with the surface mole fractions. The most consistent configurations of this study using TANSO-FTS (Thermal And Near infrared Sensor for carbon Observation - Fourier Transform Spectrometer), IASI (Infrared Atmospheric Sounding Interferometer) or surface measurements induce posterior methane global emissions of, respectively, 565 ± 21 Tg yr-1, 549 ± 36 Tg yr-1 and 538 ± 15 Tg yr-1 over the one-year period August 2009-July 2010. This consistency between the satellite retrievals (apart from SCIAMACHY) and independent surface measurements is promising for future improvement of CH4 emission estimates by atmospheric inversions.

Cressot, C.; Chevallier, F.; Bousquet, P.; Crevoisier, C.; Dlugokencky, E. J.; Fortems-Cheiney, A.; Frankenberg, C.; Parker, R.; Pison, I.; Scheepmaker, R. A.; Montzka, S. A.; Krummel, P. B.; Steele, L. P.; Langenfelds, R. L.

2014-01-01

245

Did geologic emissions of methane play any role in Quaternary climate change?  

NASA Astrophysics Data System (ADS)

The "methane-led hypotheses" assume that gas hydrates and marine seeps are the sole geologic factors controlling Quaternary atmospheric and climate changes. Nevertheless, a wider class of geologic sources of methane exist which could have played a role in past climate changes. Beyond offshore seepage, relevant geologic emissions of methane (GEM) are from onshore seepage, including mud volcanism, microseepage and geothermal flux; altogether GEM are the second most important natural source of atmospheric methane at present. The amount of methane entering the atmosphere from onshore GEM seems to prevail on that from offshore seepage. Onshore sources inject a predominantly isotopically heavy ( 13C-enriched) methane into the atmosphere. They are controlled mainly by endogenic (geodynamic) processes, which induce large-scale gas flow variations over geologic and millennial time scales, and only partially by exogenic (surface) conditions, so that they are not affected by negative feedbacks. The eventual influence on atmospheric methane concentration does not necessarily require catastrophic or abrupt releases, as proposed for the "clathrate gun hypothesis". Enhanced degassing from these sources could have contributed to the methane trends observed in the ice core records, and could explain the late Quaternary peaks of increased methane concentrations accompanied by the enrichment of isotopically heavy methane, as recently observed. This hypothesis shall be tested by means of robust multidisciplinary studies, mainly based on a series of atmospheric, biologic and geologic proxies.

Etiope, Giuseppe; Milkov, Alexei V.; Derbyshire, Edward

2008-03-01

246

In situ sensing of methane emissions from natural marine hydrocarbon seeps: A potential remote sensing technology  

NASA Astrophysics Data System (ADS)

The sources and sinks of methane, an important greenhouse gas, are poorly constrained. Remote sensing techniques can significantly improve our understanding of the global methane budget. Field and laboratory studies using in situ direct and spectral measurements of methane emissions from natural marine seepage allowed assessment of the feasibility of remote sensing. Methane plume characteristics were estimated by repeated transects of an intense marine seep area with a flame ion detector (FID) and then fit with a Gaussian plume to allow calculation of methane column abundances. These showed values greater than 0.5 g m - 2 to a downwind distance of 70 m. A numerical radiative-transfer calculation showed that in the spectral region between 2200 and 2340 nm, which is sensitive to methane, there is mild sensitivity to water vapor interference, and that methane levels were well above the noise equivalent delta radiance of the Airborne Visible Infrared Imaging Spectrometer (AVIRIS). During a separate field study, FIDs recorded methane concentrations at 2.2, 3.6, and 5-m height while transecting an active seep area and concurrently collecting spectra using a field spectrometer. Several plumes were identified and a peak concentration of 200 ppm was measured. The presence of methane plumes along the incident path, as determined from the FID data, was related to the presence of methane absorption features in spectra above atmospheric background, which were absent outside the plumes.

Leifer, Ira; Roberts, Dar; Margolis, Jack; Kinnaman, Frank

2006-05-01

247

Methane emissions from beef cattle: effects of fumaric acid, essential oil, and canola oil.  

PubMed

The objective of this study was to identify feed additives that reduce enteric methane emissions from cattle. We measured methane emissions, total tract digestibility (using chromic oxide), and ruminal fermentation (4 h after feeding) in growing beef cattle fed a diet supplemented with various additives. The experiment was designed as a replicated 4 x 4 Latin square with 21-d periods and was conducted using 16 Angus heifers (initial BW of 260 +/- 32 kg). Treatments were: control (no additive), fumaric acid (175 g/d) with sodium bicarbonate (75 g/d), essential oil and spice extract (1 g/d), or canola oil (4.6% of DMI). The basal diet consisted of 75% whole-crop barley silage, 19% steam-rolled barley, and 6% supplement (DM basis). Four large chambers (2 animals fed the same diet per chamber) were equipped to measure methane emissions for 3 d each period. Adding canola oil to the diet decreased (P = 0.009) total daily methane emissions by 32% and tended (P = 0.09) to decrease methane emissions as a percentage of gross energy intake by 21%. However, much of the reduction in methane emissions was due to decreased (P < 0.05) feed intake and lower (P < 0.05) total tract digestibility of DM and fiber. Digestibility of all nutrients was also lowered (P < 0.05) by feeding essential oil, but there were no effects on ruminal fermentation or methane emissions. In contrast, adding fumaric acid to the diet increased total VFA concentration (P = 0.03), increased propionate proportions (P = 0.01), and decreased the acetate:propionate ratio (P = 0.002), but there was no measurable effect on methane emissions. The study demonstrates that canola oil can be used to reduce methane losses from cattle, but animal performance may be compromised due to lower feed intake and decreased fiber digestibility. Essential oils had no effect on methane emissions, whereas fumaric acid caused potentially beneficial changes in ruminal fermentation but no measurable reductions in methane emissions. PMID:16699105

Beauchemin, K A; McGinn, S M

2006-06-01

248

Methane Emission Resolving Power of the Proposed GEO-CAPE Satellite  

NASA Astrophysics Data System (ADS)

Methane (CH4) is an important greenhouse gas in the atmosphere, ranked second behind carbon dioxide in total preindustrial to present radiative forcing. Despite a well-constrained global methane budget, there are still large uncertainties regarding the magnitude and trend of emissions at regional scales. Recent studies of methane emissions from the U.S. natural gas industry have found discrepancies between reported emission inventories and values observed in field studies. The proposed Geostationary Coastal and Air Pollution Events (GEO-CAPE) satellite mission proposes to launch an instrument, GCIRI, that would provide hourly methane observations over North America. In this study, we examined the potential methane emission resolving ability of GCIRI using an ensemble Monte-Carlo approach to approximate the posterior error of CH4 flux inversions. Initial results show that inversions using GCIRI observations reduce the emission error by 50-100% of the a priori error in regions with moderate to high methane emissions. We further quantify the information content of the inversion by investigating the overall degrees of freedom for signal and the resolution matrix. While initial results are promising, further experiments using an alternative ensemble scheme and finite-difference tests are being performed to verify estimated posterior error values. Lastly, we consider how satellite characteristics, such as the averaging kernel and observational error, impact the information content of the inversion.

Perkins, W. A.; Henze, D. K.; Bousserez, N.; Wecht, K.

2013-12-01

249

Reducing the environmental impact of methane emissions from dairy farms by anaerobic digestion of cattle waste.  

PubMed

Four dairy cattle farms considered representative of Northern Spain milk production were studied. Cattle waste was characterised and energy consumption in the farms was inventoried. Methane emissions due to slurry/manure management and fuel consumption on the farms were calculated. The possibility of applying anaerobic digestion to the slurry to minimise emissions and of using the biogas produced to replace fossil fuels on the farm was considered. Methane emissions due to slurry management (storage and use as fertiliser) ranged from 34 to 66kg CH(4)cow(-1)year(-1) for dairy cows and from 13 to 25kg CH(4)cow(-1)year(-1) for suckler calves. Cattle on these farms are housed for most of the year, and the contribution from emissions from manure dropped in pastures is insignificant due to the very low methane conversion factors. If anaerobic digestion were implemented on the farms, the potential GHG emissions savings per livestock unit would range from 978 to 1776kg CO(2)eq year(-1), with the main savings due to avoided methane emissions during slurry management. The methane produced would be sufficient to supply digester heating needs (35-55% of the total methane produced) and on-farm fuel energy requirements. PMID:21504844

Marañón, E; Salter, A M; Castrillón, L; Heaven, S; Fernández-Nava, Y

2011-08-01

250

Fallow season straw and water management effects on methane emissions in California rice  

NASA Astrophysics Data System (ADS)

In response to legislative mandate to reduce postharvest straw burning and environmental concerns to restore wetland habitat for Pacific flyway waterfowl, California rice growers are incorporating straw into soil and flooding rice fields in winter. These changes were hypothesized to alter soil carbon cycling pathways across the region. The principal objective of this study was to determine how various winter fallowed straw and water management changes would affect year-round methane emissions. Main plots were winter flood and nonflood, and subplots had straw treatments: burned, soil incorporated, or rolled (partially soil incorporated). Results showed the principal factor controlling methane emissions was the interaction of flooding and straw amendments. The presence of either water or straw alone led to low emissions. Winter emissions accounted for 50% of annual totals in straw-amended treatments despite lower temperatures and the presence of plants in summer. Summer emissions were significantly influenced by winter straw amendments but not by winter flood. Postdrain peaks after winter drain accounted for 10-13% of annual emissions in treatments with amended straw. Although rolled and incorporated treatments had similar straw inputs, methane fluxes from rolled treatments were higher than from incorporated treatments. Measurements of methane should be conducted year-round to capture fallow and postdrain fluxes and improve global emission estimates. Regional emission estimates showed that 2.6 times more methane was emitted after flooding plus incorporation was implemented than before the legislative mandate was enacted.

Fitzgerald, G. J.; Scow, K. M.; Hill, J. E.

2000-09-01

251

Modeling of Microscale Variations in Methane Fluxes.  

National Technical Information Service (NTIS)

The current study analyzes the different modes of variation in methane fluxes from different microsites of a boreal mire. The results emphasize the importance of microsite characteristics, water table and vegetation cover for methane fluxes. Water level a...

A. Kettunen

2002-01-01

252

Methane emissions from terrestrial plants under aerobic conditions  

Microsoft Academic Search

Methane is an important greenhouse gas and its atmospheric concentration has almost tripled since pre-industrial times. It plays a central role in atmospheric oxidation chemistry and affects stratospheric ozone and water vapour levels. Most of the methane from natural sources in Earth's atmosphere is thought to originate from biological processes in anoxic environments. Here we demonstrate using stable carbon isotopes

Frank Keppler; John T. G. Hamilton; Marc Braß; Thomas Röckmann

2006-01-01

253

Methane emission from Russian frozen wetlands under conditions of climate change  

NASA Astrophysics Data System (ADS)

There is growing evidence that the climate change will have significant impact on permafrost, leading to warming, thawing, and disappearance of the frozen ground. Arctic soils contain 14%-30% of all the carbon stored in soils worldwide, many of which is accumulated in the Arctic wetlands (Anisimov & Reneva 2006). Wetlands occupy almost 2 million km2 in the circumpolar region, contain about 50 Gt C, and because of the high groundwater levels favour the production of methane in the anaerobic carbon-rich soil layer (Anisimov et al 2005). Methane has 21-times stronger greenhouse effect than the equal amount of CO2, and there are growing concerns that enhanced CH4 emission may have significant effect on the global radiative forcing. The goal of our study was to estimate the potential increase in the methane emission from Russian frozen wetlands under the projected for the mid-21st century climatic conditions and to evaluate the effect it may have on global radiative forcing. We used digital geographically referenced contours of Russian wetlands from 1:1,000,000-scale topographic maps to calculate the total area (350 000 km2) and the fraction of land they occupy in the nodes of 0.5 by 0.5 degree lat/long regular grid spanning permafrost regions. These data were overlaid with the results from predictive permafrost model (Anisimov & Belolutskaia 2003, Anisimov et al 1999) forced by CCC, HadCM3, GFDL, NCAR climatic projections for 2050 under B1 emission scenario (ref. http://ipcc-ddc.cru.uea.ac.uk/ and http://igloo.atmos.uiuc.edu/IPCC/). Ultimately, we calculated the increase in the amount of organic material that may potentially become available for decomposition due to deeper seasonal thawing of wetlands in the Russian part of Arctic. Following (Christensen et al 2003a, Christensen et al 2003b) we hypothesised that the temperature and substrate availability combined explain almost entirely the variations in mean annual methane emissions. We used the results of numerous calculations with the full-scale carbon model simulating a large variety of soil and temperature conditions to derive a simple parameterization that links the relative changes of methane flux with soil temperature and active layer thickness: J2/J1= exp 0.1(T2 - T1) , where J - methane flux, T - ground temperature, Hd - thaw depth, subscripts 1 and 2 designate the baseline and future climatic conditions current and the future time slices. Our results for the mid-21stcentury indicate that the annual emission of methane from Russian permafrost region may increase by 20% - 40% over most of the area, and by 50% - 80% in the northernmost locations, which corresponds to 6-8 Mt y-1. Given that the average residence time of methane in the atmosphere is 12 years, and assuming that other sinks and sources remain unchanged, by the mid-21st century the additional annual 6-8 Mt source due to thawing of permafrost may increase the overall amount of atmospheric methane by approximately 100 Mt, or 0.04 ppm. The sensitivity of the global temperature to 1 ppm of atmospheric methane is approximately 0.3 oC (Ramaswamy 2001), and thus the additional radiative forcing resulting from such an increase may raise the global mean annual air temperature by 0.012 oC. References Anisimov OA, Belolutskaia MA. 2003. Climate-change impacts on permafrost: predictive modeling and uncertainties. In Problems of ecological modeling and monitoring of ecosystems, ed. Y Izrael, pp. 21-38. S.Petersburg: Hydrometeoizdat Anisimov OA, Lavrov SA, Reneva SA. 2005. Modelling the emission of greenhouse gases from the Arctic wetlands under the conditions of the global warming. In Climatic and environmental changes, ed. GV Menzhulin, pp. 21-39. S.Petersburg: Hydrometeoizdat Anisimov OA, Nelson FE, Pavlov AV. 1999. Predictive scenarios of permafrost development under the conditions of the global climate change in the XXI century. Earth Cryosphere 3: 15-25 Anisimov OA, Reneva SA. 2006. Permafrost and changing climate: the Russian perspective. Ambio 35: 169-75 Christensen TR, Ekberg A, Strom L, Mastepanov M,

Reneva, S.

2009-04-01

254

Characterising Arctic Wetland Methane Emissions - Isotope studies from the ground to tropopause  

NASA Astrophysics Data System (ADS)

Many methane sources have distinct isotopic signatures and hence atmospheric measurements can be used to apportion emissions from different source categories (wetlands, gas leaks, biomass burning etc). However within source categories there are often temporal and geographic variations in the emitted signature. Production, transport and oxidation of methane from wetlands before emission to the atmosphere can vary according to the trophic status, temperature, water table and vegetation type. The ?13C signature of produced methane depends on the distribution of and the ratio of methane from acetate dissimilation and CO2 reduction. The signature of methane released to the atmosphere will also depend on the transport pathway and the amount of oxidation that has occurred. Flux and isotopic signature from one chamber to the next and from one region to another are highly variable. This study presents measurements from the MAMM campaigns of 2012 and 2013 which incorporated ground and aircraft sampling of methane across northern Scandinavia for isotopic analysis. On the ground isotopic signature was measured in chambers at Sodankylä (Finland) and Abisko (Sweden) and diurnal measurements were made within five wetland areas. Concurrent tower and aircraft measurements considered emissions over a larger region. Wetland emissions dominate the methane source measured over the European Arctic in the summer. In the July 2012 aircraft campaign elevated methane concentrations were measured in the low altitude samples over land with an isotopic source signature (?13C) of -72 × 4 ‰, comparable to the isotopic signature of -71 × 2 ‰ measured on the ground in emissions from wetlands. The isotopic composition of methane measured over the same area in an aircraft campaign in March 2012 was significantly more enriched in 13C at -53 ‰. High latitude wetland methane emissions tend to be more depleted in 13C than those from wetlands further south. Fluxes are highly seasonal with emissions occurring from northern Scandinavia between May and October. The wetland source is visible in atmospheric methane ?13C records measured at high latitude atmospheric background stations as a late summer depletion in 13C which contrasts with the more enriched 13C signature of winter emissions from northern sources such as gas fields.

Fisher, R. E.; France, J. L.; Lowry, D.; Lanoiselle, M.; Skiba, U.; Drewer, J.; Aurela, M.; Crill, P. M.; Bauguitte, S.; O'Shea, S.; Allen, G.; Gallagher, M. W.; Cain, M.; Warwick, N. J.; Pyle, J. A.; Nisbet, E. G.

2013-12-01

255

A conduit dilation model of methane venting from lake sediments  

USGS Publications Warehouse

Methane is a potent greenhouse gas, but its effects on Earth's climate remain poorly constrained, in part due to uncertainties in global methane fluxes to the atmosphere. An important source of atmospheric methane is the methane generated in organic-rich sediments underlying surface water bodies, including lakes, wetlands, and the ocean. The fraction of the methane that reaches the atmosphere depends critically on the mode and spatiotemporal characteristics of free-gas venting from the underlying sediments. Here we propose that methane transport in lake sediments is controlled by dynamic conduits, which dilate and release gas as the falling hydrostatic pressure reduces the effective stress below the tensile strength of the sediments. We test our model against a four-month record of hydrostatic load and methane flux in Upper Mystic Lake, Mass., USA, and show that it captures the complex episodicity of methane ebullition. Our quantitative conceptualization opens the door to integrated modeling of methane transport to constrain global methane release from lakes and other shallow-water, organic-rich sediment systems, and to assess its climate feedbacks.

Scandella, B. P.; Varadharajan, C.; Hemond, H. F.; Ruppel, C.; Juanes, R.

2011-01-01

256

Fugitive coal mine methane emissions at five mining areas in China  

NASA Astrophysics Data System (ADS)

Large quantities (about 28 billion m 3) of methane are released to the atmosphere every year from coal-mining activities around the world. This methane represents not only a significant greenhouse gas that is contributing to global temperature change, but is also a wasted energy resource. China, the largest coal producer in the world, is responsible for over 50% of the total global release of methane-containing ventilation air from coal mines. A mine site investigation methodology was developed for collecting reliable methane emission data from coal mines. Five main coal-mining areas in China were studied and specific data were collected from two mines in each of the five mining groups. Information such as coal and methane reserves, ventilation air released, methane concentration and methane release rates were collected. Future development plans were evaluated and used to estimate potential future emissions. It was determined that most of the methane generated in the five mining areas is currently released to the atmosphere.

Su, Shi; Han, Jiaye; Wu, Jinyan; Li, Hongjun; Worrall, Rhys; Guo, Hua; Sun, Xin; Liu, Wenge

2011-04-01

257

Climate versus emission drivers of methane lifetime against loss by tropospheric OH from 1860-2100  

NASA Astrophysics Data System (ADS)

With a more-than-doubling in the atmospheric abundance of the potent greenhouse gas methane (CH4) since preindustrial times, and indications of renewed growth following a leveling off in recent years, questions arise as to future trends and resulting climate and public health impacts from continued growth without mitigation. Changes in atmospheric methane lifetime are determined by factors which regulate the abundance of OH, the primary methane removal mechanism, including changes in CH4 itself. We investigate the role of emissions of short-lived species and climate in determining the evolution of methane lifetime against loss by tropospheric OH, (?CH4_OH), in a suite of historical (1860-2005) and future Representative Concentration Pathway (RCP) simulations (2006-2100), conducted with the Geophysical Fluid Dynamics Laboratory (GFDL) fully coupled chemistry-climate model (CM3). From preindustrial to present, CM3 simulates an overall 5% increase in ?CH4_OH due to a doubling of the methane burden which offsets coincident increases in nitrogen oxide (NOx emissions. Over the last two decades, however, the ?CH4_OH declines steadily, coinciding with the most rapid climate warming and observed slow-down in CH4 growth rates, reflecting a possible negative feedback through the CH4 sink. Sensitivity simulations with CM3 suggest that the aerosol indirect effect (aerosol-cloud interactions) plays a significant role in cooling the CM3 climate. The projected decline in aerosols under all RCPs contributes to climate warming over the 21st century, which influences the future evolution of OH concentration and ?CH4_OH. Projected changes in ?CH4_OH from 2006 to 2100 range from -13% to +4%. The only projected increase occurs in the most extreme warming case (RCP8.5) due to the near-doubling of the CH4 abundance, reflecting a positive feedback on the climate system. The largest decrease occurs in the RCP4.5 scenario due to changes in short-lived climate forcing agents which reinforce climate warming and enhance OH. This decrease is more-than-halved in a sensitivity simulation in which only well-mixed greenhouse gas radiative forcing changes along the RCP4.5 scenario (5% vs. 13%).

John, J. G.; Fiore, A. M.; Naik, V.; Horowitz, L. W.; Dunne, J. P.

2012-12-01

258

Retrieval of methane source strengths in Europe using a simple modeling approach to assess the potential of space-borne lidar observations  

NASA Astrophysics Data System (ADS)

We investigate the sensitivity of future space-borne lidar measurements to changes in surface methane emissions. We use surface methane observations from nine European ground stations, and a Lagrangian transport model to obtain surface methane emissions for 2010. Our inversion shows the strongest emissions from the Netherlands, the coalmines in Upper Silesia Poland, and wetlands in southern Finland. Our simulated methane surface concentration captures at least half of the daily variability in the observations, suggesting that the transport model is correctly simulating the regional transport pathways over Europe. With this tool we can perturb the surface fluxes and see the resulting changes in the simulated column methane measurements. For example, we show that future lidar instruments can detect a 50% reduction in methane emissions from the Netherlands and Germany, but only after averaging measurements on a monthly time scale.

Weaver, C.; Kiemle, C.; Kawa, S. R.; Aalto, T.; Necki, J.; Steinbacher, M.; Arduini, J.; Apadula, F.; Berkhout, H.; Hatakka, J.; O'Doherty, S.

2013-07-01

259

Mapping Asian anthropogenic emissions of non-methane volatile organic compounds to multiple chemical mechanisms  

NASA Astrophysics Data System (ADS)

An accurate speciation mapping of non-methane volatile organic compounds (NMVOC) emissions has an important impact on the performance of chemical transport models (CTMs) in simulating ozone mixing ratios and secondary organic aerosols. Taking the INTEX-B Asian NMVOC emission inventory as the case, we developed an improved speciation framework to generate model-ready anthropogenic NMVOC emissions for various gas-phase chemical mechanisms commonly used in CTMs in this work, by using an explicit assignment approach and updated NMVOC profiles. NMVOC profiles were selected and aggregated from a wide range of new measurements and the SPECIATE database v.4.2. To reduce potential uncertainty from individual measurements, composite profiles were developed by grouping and averaging source profiles from the same category. The fractions of oxygenated volatile organic compounds (OVOC) were corrected during the compositing process for those profiles which used improper sampling and analyzing methods. Emissions of individual species were then lumped into species in different chemical mechanisms used in CTMs by applying mechanism-dependent species mapping tables, which overcomes the weakness of inaccurate mapping in previous studies. Emission estimates for individual NMVOC species differ between one and three orders of magnitude for some species when different sets of profiles are used, indicating that source profile is the most important source of uncertainties of individual species emissions. However, those differences are diminished in lumped species as a result of the lumping in the chemical mechanisms. Gridded emissions for eight chemical mechanisms at 30 min × 30 min resolution as well as the auxiliary data are available at http://mic.greenresource.cn/intex-b2006. The framework proposed in this work can be also used to develop speciated NMVOC emissions for other regions.

Li, M.; Zhang, Q.; Streets, D. G.; He, K. B.; Cheng, Y. F.; Emmons, L. K.; Huo, H.; Kang, S. C.; Lu, Z.; Shao, M.; Su, H.; Yu, X.; Zhang, Y.

2014-06-01

260

A Multi-tower Measurement Network Estimate of California's Methane Emissions  

SciTech Connect

We present an analysis of methane (CH{sub 4}) emissions using atmospheric observations from five sites in California’s Central Valley across different seasons (September 2010 to June 2011). CH{sub 4} emissions for spatial regions and source sectors are estimated by comparing measured CH{sub 4} mixing ratios with transport model (WRF-STILT) predictions based on two 0.1 degree CH{sub 4} (seasonally varying “California-specific” (CALGEM) and a static global (EDGAR42)) prior emission models. Region-specific Bayesian analyses indicate that for California’s Central Valley the CALGEM- and EDGAR42-based inversions provide consistent annual total CH{sub 4} emissions (32.87±2.09 vs. 31.60±2.17 Tg CO{sub 2}eq yr{sup -1}; 68% C.I., assuming uncorrelated errors between regions). Summing across all regions of California, optimized CH{sub 4} emissions are only marginally consistent between CALGEM- and EDGAR42-based inversions (48.35±6.47 vs. 64.97±11.85 Tg CO{sub 2}eq), because emissions from coastal urban regions (where landfill and natural gas emissions are much higher in EDGAR than CALGEM) are not strongly constrained by the measurements. Combining our results with those from a recent study of the South Coast air basin narrows the range of estimates to 43 – 57 Tg CO{sub 2}eq yr{sup -1} (1.3 - 1.8 times higher than the current state inventory). These results suggest that the combination of rural and urban measurements will be necessary to verify future changes in California’s total CH{sub 4} emissions.

Jeong, Seongeun; Hsu, Ying-Kuang; Andrews, Arlyn E.; Bianco, Laura; Vaca, Patrick; Wilczak, James M.; Fischer, Marc L.

2013-12-02

261

Significant Methane Emissions from Abandoned Oil and Gas wells in Northwest Pennsylvania  

NASA Astrophysics Data System (ADS)

Abandoned (no longer operated), Orphaned (abandoned and responsible party unavailable), and/or Lost (location unknown, cannot be confirmed, or not on record) (AOL) wells provide a potential pathway for subsurface migration, and emissions to the atmosphere, of methane and other volatile hydrocarbons. However, little is known about methane fluxes from AOL wells. Of the 12,000 abandoned and orphaned oil and gas wells on the Pennsylvania Department of Environmental Protection's (PA DEP) list, 36% are in McKean County. McKean County is home to the Bradford Oil Field, the world's first large oil field, which in 1881 produced 83% of America's output. A large fraction of the oil and gas wells in McKean County are AOL and some estimates of the number of AOL wells exceed the number of wells listed by the PA DEP by factors of 20 or more. To characterize AOL wells' potential as a significant methane source, we made first-of-a-kind measurements of methane fluxes from 8 abandoned wells in McKean County using static flux chambers. These wells are on a 40-acre lot, which includes various land cover types. Four of the eight measured wells are in forested areas, while three are in grassland, and one is in wetland areas. Two of the eight wells, one in a forested area and one in the grassland area, are plugged. Fluxes of methane, ethane, propane, and n-butane were measured using flame ionization gas chromatography. To gain insight into the source of methane (biogenic vs. thermogenic), carbon and hydrogen isotopes of methane were analyzed and the ratio of methane to heavier hydrocarbons were computed. In addition, a LI-7700 open path methane analyzer was used to provide on-line methane concentration measurement in the vicinity of AOL wells and in flux chambers. We found methane fluxes from the measured AOL wells to be significantly higher than fluxes observed in similar natural environments. Methane emissions from the two plugged wells were smaller than those from unplugged wells but non-negligible. The atmospheric methane concentration in the vicinity of some wells was elevated up to fifteen times higher than the background concentration, indicating that methane concentrations near the land surface can be used to detect emissions from AOL wells. Given the large number of AOL wells in Pennsylvania and across the country, methane emissions from AOL wells may be a significant anthropogenic source of methane and other hydrocarbons to the atmosphere. An improved understanding of the role of AOL wells as methane emission sources can aid in bridging the current gap in global and regional methane budgets, while plugging wells could provide a future opportunity for emissions reduction. Furthermore, with the growth of unconventional oil and gas production in Pennsylvania and across the globe, characterization of AOL wells as a methane source is useful for determining impacts of past, current, and future oil and gas production.

Kang, M.; Zhang, X.; Reid, M. C.; Kanno, C.; Celia, M. A.; Mauzerall, D. L.; Sun, K.; Miller, D. J.; Zondlo, M. A.; Chen, Y.; Onstott, T. C.

2013-12-01

262

Evaluation of fluidized-bed methanation catalysts and reactor modeling  

Microsoft Academic Search

The simple reactor model developed for the fluidized-bed methanator PEDU gives reasonably good parity plots for six PEDU tests using six different catalysts. This model can be used to predict the performance of the pilot plant methanator and as a building block in any computerized simulation of the BI-GAS process for process development, design or optimization purposes. Some refinements could

James T. Cobb; Robert C. Streeter

1979-01-01

263

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

NASA Astrophysics Data System (ADS)

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.

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

2011-10-01

264

The modeling of tropospheric methane: How well can point measurements be reproduced by a global model?  

NASA Astrophysics Data System (ADS)

Global model simulations of tropospheric methane are presented, using state of the art representations of its terrestrial sources. Parameters critical for its tropospheric sink and transport have been evaluated using CH3CCl3 and SF6. We assess how well available methane measurements can be reproduced by the model, and how model and measurements can most efficiently be compared. Using European Centre for Medium-Range Weather Forecasts reanalyzed meteorological fields, direct comparisons between model results and flask or in situ measurements are presented, as opposed to comparing multiannual averaged seasonal cycles and trends as was done in previous studies. When comparing monthly means derived from weekly flask sampling and the model, the agreement at stations as Bermuda East and Mace Head is improved if, instead of sampling the model at each model time step, samples are taken at the same times as the measurements were taken. A method is presented to estimate the potential influence of subgrid variability using a marked tracer that is emitted in the vicinity of observational stations only. From the contribution of this tracer to the computed methane concentration at a particular station, the potential contribution of subgrid sources can be estimated. Radon 222 is used to select baseline conditions in the model to improve the comparability of model and measurements when a clean air sector is selected for sampling. Comparisons of model results and measurements, screened for local influences and artifacts of wind sector selection, indicate that the model has in particular difficulty reproducing seasonal cycles at higher latitude stations of the Northern Hemisphere. Sensitivity simulations show that the simulated annual variation at these stations is sensitive to the parameterization of wetland emissions. Also at the South China Sea, model simulations point to errors in the representation of methane sources. Marked tracer simulations indicate that this is most likely related to emissions from natural wetlands and rice paddies, in line with recent inverse modeling and up-scaling estimates.

Houweling, Sander; Dentener, Frank; Lelieveld, Jos; Walter, Bernadette; Dlugokencky, Ed

2000-04-01

265

Measurements of methane emissions at natural gas production sites in the United States  

PubMed Central

Engineering estimates of methane emissions from natural gas production have led to varied projections of national emissions. This work reports direct measurements of methane emissions at 190 onshore natural gas sites in the United States (150 production sites, 27 well completion flowbacks, 9 well unloadings, and 4 workovers). For well completion flowbacks, which clear fractured wells of liquid to allow gas production, methane emissions ranged from 0.01 Mg to 17 Mg (mean = 1.7 Mg; 95% confidence bounds of 0.67–3.3 Mg), compared with an average of 81 Mg per event in the 2011 EPA national emission inventory from April 2013. Emission factors for pneumatic pumps and controllers as well as equipment leaks were both comparable to and higher than estimates in the national inventory. Overall, if emission factors from this work for completion flowbacks, equipment leaks, and pneumatic pumps and controllers are assumed to be representative of national populations and are used to estimate national emissions, total annual emissions from these source categories are calculated to be 957 Gg of methane (with sampling and measurement uncertainties estimated at ±200 Gg). The estimate for comparable source categories in the EPA national inventory is ?1,200 Gg. Additional measurements of unloadings and workovers are needed to produce national emission estimates for these source categories. The 957 Gg in emissions for completion flowbacks, pneumatics, and equipment leaks, coupled with EPA national inventory estimates for other categories, leads to an estimated 2,300 Gg of methane emissions from natural gas production (0.42% of gross gas production).

Allen, David T.; Torres, Vincent M.; Thomas, James; Sullivan, David W.; Harrison, Matthew; Hendler, Al; Herndon, Scott C.; Kolb, Charles E.; Fraser, Matthew P.; Hill, A. Daniel; Lamb, Brian K.; Miskimins, Jennifer; Sawyer, Robert F.; Seinfeld, John H.

2013-01-01

266

Measurements of methane emissions at natural gas production sites in the United States.  

PubMed

Engineering estimates of methane emissions from natural gas production have led to varied projections of national emissions. This work reports direct measurements of methane emissions at 190 onshore natural gas sites in the United States (150 production sites, 27 well completion flowbacks, 9 well unloadings, and 4 workovers). For well completion flowbacks, which clear fractured wells of liquid to allow gas production, methane emissions ranged from 0.01 Mg to 17 Mg (mean = 1.7 Mg; 95% confidence bounds of 0.67-3.3 Mg), compared with an average of 81 Mg per event in the 2011 EPA national emission inventory from April 2013. Emission factors for pneumatic pumps and controllers as well as equipment leaks were both comparable to and higher than estimates in the national inventory. Overall, if emission factors from this work for completion flowbacks, equipment leaks, and pneumatic pumps and controllers are assumed to be representative of national populations and are used to estimate national emissions, total annual emissions from these source categories are calculated to be 957 Gg of methane (with sampling and measurement uncertainties estimated at ± 200 Gg). The estimate for comparable source categories in the EPA national inventory is ~1,200 Gg. Additional measurements of unloadings and workovers are needed to produce national emission estimates for these source categories. The 957 Gg in emissions for completion flowbacks, pneumatics, and equipment leaks, coupled with EPA national inventory estimates for other categories, leads to an estimated 2,300 Gg of methane emissions from natural gas production (0.42% of gross gas production). PMID:24043804

Allen, David T; Torres, Vincent M; Thomas, James; Sullivan, David W; Harrison, Matthew; Hendler, Al; Herndon, Scott C; Kolb, Charles E; Fraser, Matthew P; Hill, A Daniel; Lamb, Brian K; Miskimins, Jennifer; Sawyer, Robert F; Seinfeld, John H

2013-10-29

267

Reducing Open Cell Landfill Methane Emissions with a Bioactive Alternative Daily  

SciTech Connect

Methane and carbon dioxide are formed in landfills as wastes degrade. Molecule-for-molecule, methane is about 20 times more potent than carbon dioxide at trapping heat in the earth's atmosphere, and thus, it is the methane emissions from landfills that are scrutinized. For example, if emissions composed of 60% methane and 40% carbon dioxide were changed to a mix that was 40% methane and 60% carbon dioxide, a 30% reduction in the landfill's global warming potential would result. A 10% methane, 90% carbon dioxide ratio will result in a 75% reduction in global warming potential compared to the baseline. Gas collection from a closed landfill can reduce emissions, and it is sometimes combined with a biocover, an engineered system where methane oxidizing bacteria living in a medium such as compost, convert landfill methane to carbon dioxide and water. Although methane oxidizing bacteria merely convert one greenhouse gas (methane) to another (carbon dioxide), this conversion can offer significant reductions in the overall greenhouse gas contribution, or global warming potential, associated with the landfill. What has not been addressed to date is the fact that methane can also escape from a landfill when the active cell is being filled with waste. Federal regulations require that newly deposited solid waste to be covered daily with a 6 in layer of soil or an alternative daily cover (ADC), such as a canvas tarp. The aim of this study was to assess the feasibility of immobilizing methane oxidizing bacteria into a tarp-like matrix that could be used for alternative daily cover at open landfill cells to prevent methane emissions. A unique method of isolating methanotrophs from landfill cover soil was used to create a liquid culture of mixed methanotrophs. A variety of prospective immobilization techniques were used to affix the bacteria in a tarp-like matrix. Both gel encapsulation of methanotrophs and gels with liquid cores containing methanotrophs were readily made but prone to rapid desiccation. Bacterial adsorption onto foam padding, natural sponge, and geotextile was successful. The most important factor for success appeared to be water holding capacity. Prototype biotarps made with geotextiles plus adsorbed methane oxidizing bacteria were tested for their responses to temperature, intermittent starvation, and washing (to simulate rainfall). The prototypes were mesophilic, and methane oxidation activity remained strong after one cycle of starvation but then declined with repeated cycles. Many of the cells detached with vigorous washing, but at least 30% appeared resistant to sloughing. While laboratory landfill simulations showed that four-layer composite biotarps made with two different types of geotextile could remove up to 50% of influent methane introduced at a flux rate of 22 g m{sup -2} d{sup -1}, field experiments did not yield high activity levels. Tests revealed that there were high hour-to-hour flux variations in the field, which, together with frequent rainfall events, confounded the field testing. Overall, the findings suggest that a methanotroph embedded biotarp appears to be a feasible strategy to mitigate methane emission from landfill cells, although the performance of field-tested biotarps was not robust here. Tarps will likely be best suited for spring and summer use, although the methane oxidizer population may be able to shift and adapt to lower temperatures. The starvation cycling of the tarp may require the capacity for intermittent reinoculation of the cells, although it is also possible that a subpopulation will adapt to the cycling and become dominant. Rainfall is not expected to be a major factor, because a baseline biofilm will be present to repopulate the tarp. If strong performance can be achieved and documented, the biotarp concept could be extended to include interception of other compounds beyond methane, such as volatile aromatic hydrocarbons and chlorinated solvents.

Helene Hilger; James Oliver; Jean Bogner; David Jones

2009-03-31

268

Methane emissions and related physicochemical soil and water parameters in rice–fish systems in Bangladesh  

Microsoft Academic Search

Lowland rice fields constitute a semi aquatic environment, which is potentially suitable for fish production. Little is known about the effect of fish on greenhouse gas emissions from integrated rice–fish systems. An experiment was carried out at the Bangladesh Agricultural University to assess the effect of the stocking of fish on methane emissions from rice fields. Common carp, Cyprinus carpio

M. Frei; M. A. Razzak; M. M. Hossain; M. Oehme; S. Dewan; K. Becker

2007-01-01

269

Reducing the environmental impact of methane emissions from dairy farms by anaerobic digestion of cattle waste  

Microsoft Academic Search

Four dairy cattle farms considered representative of Northern Spain milk production were studied. Cattle waste was characterised and energy consumption in the farms was inventoried. Methane emissions due to slurry\\/manure management and fuel consumption on the farms were calculated. The possibility of applying anaerobic digestion to the slurry to minimise emissions and of using the biogas produced to replace fossil

E. Marañón; A. M. Salter; L. Castrillón; S. Heaven; Y. Fernández-Nava

2011-01-01

270

METHOD FOR ESTIMATING METHANE EMISSIONS FROM UNDERGROUND COAL MINES: PRELIMINARY FINDINGS  

EPA Science Inventory

The paper discusses the development of an improved method for estimating global methane (CH4) emissions from underground coal mining. ince emissions data presently not available for surface mines, this method is currently restricted to underground mines. The EPA has embarked on a...

271

Methane Emissions from Irrigated Rice Fields in Northern India (New Delhi)  

Microsoft Academic Search

Methane (CH4) emission fluxes from rice fields as affected by water regime, organic amendment, and rice cultivar were measured at the Indian Agricultural Research Institute, New Delhi, using manual and automatic sampling techniques of the closed chamber method. Measurements were conducted during four consecutive cropping seasons (July to October) from 1994 to 1997. Emission rates were very low (between 16

M. C. Jain; S. Kumar; R. Wassmann; S. Mitra; S. D. Singh; J. P. Singh; R. Singh; A. K. Yadav; S. Gupta

2000-01-01

272

METHANE EMISSIONS FROM THE NATURAL GAS INDUSTRY VOLUME 11: COMPRESSOR DRIVER EXHAUST  

EPA Science Inventory

The 15-volume report summarizes the results of a comprehensive program to quantify methane (CH4) emissions from the U.S. natural gas industry for the base year. The objective was to determine CH4 emissions from the wellhead and ending downstream at the customer's meter. The accur...

273

METHANE EMISSIONS FROM THE NATURAL GAS INDUSTRY VOLUME 13: CHEMICAL INJECTION PUMPS  

EPA Science Inventory

The 15-volume report summarizes the results of a comprehensive program to quantify methane (CH4) emissions from the U.S. natural gas industry for the base year. The objective was to determine CH4 emissions from the wellhead and ending downstream at the customer's meter. The accur...

274

METHANE EMISSIONS FROM THE NATURAL GAS INDUSTRY VOLUME 14: GLYCOL DEHYDRATORS  

EPA Science Inventory

The 15-volume report summarizes the results of a comprehensive program to quantify methane (CH4) emissions from the U.S. natural gas industry for the base year. The objective was to determine CH4 emissions from the wellhead and ending downstream at the customer's meter. The accur...

275

METHANE EMISSIONS FROM THE NATURAL GAS INDUSTRY VOLUME 12: PNEUMATIC DEVICES  

EPA Science Inventory

The 15-volume report summarizes the results of a comprehensive program to quantify methane (CH4) emissions from the U.S. natural gas industry for the base year. The objective was to determine CH4 emissions from the wellhead and ending downstream at the customer's meter. The accur...

276

Methane emissions from rice fields: The effects of climatic and agricultural factors. Final report, March 1, 1994--April 30, 1997  

SciTech Connect

The work reported was performed for the purpose of refining estimates of methane emissions from rice fields. Research performed included methane flux measurements, evaluation of variables affecting emissions, compilation of a data base, and continental background measurements in China. The key findings are briefly described in this report. Total methane emissions, seasonal patterns, and spatial variability were measured for a 7-year periods. Temperature was found to be the most important variable studies affecting methane emissions. The data archives for the research are included in the report. 5 refs., 6 figs.

Khalil, M.A.K. [Portland State Univ., OR (United States). Dept. of Physics] [Portland State Univ., OR (United States). Dept. of Physics; Rasmussen, R.A. [Oregon Graduate Institute, Portland, OR (United States). Dept. of Environmental Science and Engineering] [Oregon Graduate Institute, Portland, OR (United States). Dept. of Environmental Science and Engineering

1997-10-01

277

Dynamic Viscosity Modeling of Methane + n-Decane and Methane + Toluene Mixtures : Comparative Study of Some Representative Models  

Microsoft Academic Search

Viscosity measurements of well-defined mixtures are useful in order to evaluate existing viscosity models. Recently, an extensive experimental study of the viscosity at pressures up to 140 MPa has been carried out for the binary systems methane + n-decane and methane + toluene, between 293.15 and 373.15 K and for several methane compositions. Although very far from real petroleum fluids, these mixtures are interesting in order

Antoine Baylaucq; Christian Boned; Xavier Canet; Claus K. Zéberg-Mikkelsen; Sergio E. Quiñones-Cisneros; Honggang Zhou

2005-01-01

278

Mapping Asian anthropogenic emissions of non-methane volatile organic compounds to multiple chemical mechanisms  

NASA Astrophysics Data System (ADS)

An accurate speciation mapping of non-methane volatile organic compounds (NMVOC) emissions has an important impact on the performance of chemical transport models (CTMs) in simulating ozone mixing ratios and secondary organic aerosols. In this work, we developed an improved speciation framework to generate model-ready anthropogenic Asian NMVOC emissions for various gas-phase chemical mechanisms commonly used in CTMs by using an explicit assignment approach and updated NMVOC profiles, based on the total NMVOC emissions in the INTEX-B Asian inventory for the year 2006. NMVOC profiles were selected and aggregated from a wide range of new measurements and the SPECIATE database. To reduce potential uncertainty from individual measurements, composite profiles were developed by grouping and averaging source profiles from the same category. The fractions of oxygenated volatile organic compounds (OVOC) were corrected during the compositing process for those profiles which used improper sampling and analyzing methods. Emissions of individual species were then lumped into species in different chemical mechanisms used in CTMs by applying mechanism-dependent species mapping tables, which overcomes the weakness of inaccurate mapping in previous studies. Gridded emissions for eight chemical mechanisms are developed at 30 min × 30 min resolution using various spatial proxies and are provided through the website: http://mic.greenresource.cn/intex-b2006. Emission estimates for individual NMVOC species differ between one and three orders of magnitude for some species when different sets of profiles are used, indicating that source profile is the most important source of uncertainties of individual species emissions. However, those differences are diminished in lumped species as a result of the lumping in the chemical mechanisms.

Li, M.; Zhang, Q.; Streets, D. G.; He, K. B.; Cheng, Y. F.; Emmons, L. K.; Huo, H.; Kang, S. C.; Lu, Z.; Shao, M.; Su, H.; Yu, X.; Zhang, Y.

2013-12-01

279

[Distribution and emission of methane from the Changjiang].  

PubMed

Field surveys along the Changjiang were carried out in January 2008 and September 2008, persistently. Monthly survey at Xuliujing of the Changjiang Estuary was carried out from September 2007 to August 2008. Concentrations of methane in the Changjiang were measured by purge and trap-gas chromatography and the atmospheric methane fluxes were calculated according to the equation by Wanninkhof. The mean concentration in surface waters of the Changjiang was (330.8 +/- 186.9) nmol x L(-1) in January 2008 and (80.9 +/- 58.3) nmol x L(-1) in September 2008, persistently. Concentrations in bottom waters were consistent with those in surface waters. Supersaturated in methane with an average air-water flux of (385.1 +/- 278.0) micromol x (m2 x d)(-1). Besides, average methane concentration at Xuliujing was (167.5 +/- 91.4) nmol x L(-1) with an average air-water flux (690.9 +/- 291.6) micromol x (m2 x d)(-1), the high values appeared in February and July. Along the middle reaches of the Yangtze River, methane concentrations were increased, and the lower reaches were reduced. In the estuary, methane concentrations decreased rapidly from Xuliujing to the sea, showed negative correlation with salinity. The input of CH4-rich water form tributaries and lakes impacted the methane concentration trend of the Changjiang. The Changjiang was estimated to contribute 208 Gg CH4 to the atmosphere annually. However, the freshwater CH4 discharge to the East China Sea was 112 x 10(6) mol x a(-1) in the estuary. PMID:21404659

Zhao, Jing; Zhang, Gui-Ling; Wu, Ying; Yang, Jing

2011-01-01

280

Urban sources and emissions of nitrous oxide and methane in southern California, USA  

NASA Astrophysics Data System (ADS)

Anthropogenic activities have resulted in increasing levels of greenhouse gases, including carbon dioxide, methane, and nitrous oxide. While global and regional emissions sources of carbon dioxide are relatively well understood, methane and nitrous oxide are less constrained, particularly at regional scales. Here we present the results of an investigation of sources and emissions of methane and nitrous oxide in Los Angeles, California, USA, one of Earth's largest urban areas. The original goal of the project was to determine whether isotopes are useful tracers of agricultural versus urban nitrous oxide and methane sources. For methane, we found that stable isotopes (carbon-13 and deuterium) and radiocarbon are good tracers of biogenic versus fossil fuel sources. High altitude observations of methane concentration, measured continuously using tunable laser spectroscopy, and isotope ratios, measured on discrete flask samples using mass spectrometry, indicate that the predominant methane source in Los Angeles is from fossil fuels, likely from "fugitive" emissions from geologic formations, natural gas pipelines, oil refining, or power plants. We also measured nitrous oxide emissions and isotope ratios from urban (landscaping and wastewater treatment) and agricultural sources (corn and vegetable fields). There was no difference in nitrous oxide isotope ratios between the different types of sources, although stable isotopes did differ between nitrous oxide produced in oxic and anoxic wastewater treatment tanks. Our nitrous oxide flux data indicate that landscaped turfgrass emits nitrous oxide at rates equivalent to agricultural systems, indicating that ornamental soils should not be disregarded in regional nitrous oxide budgets. However, we also showed that wastewater treatment is a much greater source of nitrous oxide than soils regionally. This work shows that global nitrous oxide and methane budgets are not easily downscaled to regional, urban settings, which has implications for cities and states, such as California, looking to reduce their overall greenhouse gas footprints.

Townsend-Small, A.; Pataki, D.; Tyler, S. C.; Czimczik, C. I.; Xu, X.; Christensen, L. E.

2012-12-01

281

Trends and inter-annual variability of methane emissions derived from 1979-1993 global CTM simulations  

Microsoft Academic Search

The trend and interannual variability of methane sources are derived from multi-annual simulations of tropospheric photochemistry using a 3-D global chemistry-transport model. Our semi-inverse analysis uses the fifteen years (1979--1993) re-analysis of ECMWF meteorological data and annually varying emissions including photo-chemistry, in conjunction with observed CH4 concentration distributions and trends derived from the NOAA-CMDL surface stations. Dividing the world in

F. Dentener; M. van Weele; M. Krol; S. Houweling; P. van Velthoven

2003-01-01

282

Recent decreases in fossil-fuel emissions of ethane and methane derived from firn air.  

PubMed

Methane and ethane are the most abundant hydrocarbons in the atmosphere and they affect both atmospheric chemistry and climate. Both gases are emitted from fossil fuels and biomass burning, whereas methane (CH(4)) alone has large sources from wetlands, agriculture, landfills and waste water. Here we use measurements in firn (perennial snowpack) air from Greenland and Antarctica to reconstruct the atmospheric variability of ethane (C(2)H(6)) during the twentieth century. Ethane levels rose from early in the century until the 1980s, when the trend reversed, with a period of decline over the next 20?years. We find that this variability was primarily driven by changes in ethane emissions from fossil fuels; these emissions peaked in the 1960s and 1970s at 14-16 teragrams per year (1?Tg = 10(12)?g) and dropped to 8-10?Tg? yr(-1) by the turn of the century. The reduction in fossil-fuel sources is probably related to changes in light hydrocarbon emissions associated with petroleum production and use. The ethane-based fossil-fuel emission history is strikingly different from bottom-up estimates of methane emissions from fossil-fuel use, and implies that the fossil-fuel source of methane started to decline in the 1980s and probably caused the late twentieth century slow-down in the growth rate of atmospheric methane. PMID:21833087

Aydin, Murat; Verhulst, Kristal R; Saltzman, Eric S; Battle, Mark O; Montzka, Stephen A; Blake, Donald R; Tang, Qi; Prather, Michael J

2011-08-11

283

Rice cultivation and methane emission: Documentation of distributed geographic data sets  

NASA Technical Reports Server (NTRS)

High-resolution global data bases on the geographic and seasonal distribution of rice cultivation and associated methane emission, compiled by Matthews et al., were archived for public use. In addition to the primary data sets identifying location, seasonality, and methane emission from rice cultivation, a series of supporting data sets is included, allowing users not only to replicate the work of Matthews et al. but to investigate alternative cultivation and emission scenarios. The suite of databases provided, at 1 latitude by 1 longitude resolution for the globe, includes (1) locations of rice cultivation, (2) monthly arrays of actively growing rice areas, (3) countries and political subdivisions, and (4) monthly arrays of methane emission from rice cultivation. Ancillary data include (1) a listing, by country, of harvested rice areas and seasonal distribution of crop cycles and (2) country names and codes. Summary tables of zonal/monthly distributions of actively growing rice areas and of methane emissions are presented. Users should consult original publications for complete discussion of the data bases. This short paper is designed only to document formats of the distributed information and briefly describe the contents of the data sets and their initial application to evaluating the role of rice cultivation in the methane budget.

Matthews, Elaine; John, Jasmin; Fung, Inez

1994-01-01

284

Abiotic emissions of methane and reduced organic compounds from organic matter  

NASA Astrophysics Data System (ADS)

Recent laboratory studies show that the important greenhouse gas methane, but also other reduced atmospheric trace gases, can be emitted by abiotic processes from organic matter, such as plants, pure organic compounds and soils. It is very difficult to distinguish abiotic from biotic emissions in field studies, but in laboratory experiments this is easier because it is possible to carefully prepare/sterilize samples, or to control external parameters. For example, the abiotic emissions always show a strong increase with temperature when temperatures are increased to 70C or higher, well above the temperature optimum for bacterial activity. UV radiation has also been clearly shown to lead to emission of methane and other reduced gases from organic matter. Interesting information on the production mechanism has been obtained from isotope studies, both at natural abundance and with isotope labeling. For example, the methoxyl groups of pectin were clearly identified to produce methane. However, analysis of the isotopic composition of methane from natural samples clearly indicates that there must be other molecular mechanisms that lead to methane production. Abiotic methane generation could be a ubiquitous process that occurs naturally at low rates from many different sources.

Roeckmann, T.; Keppler, F.; Vigano, I.; Derendorp, L.; Holzinger, R.

2012-12-01

285

Temporal patterns of methane emissions from wetland rice fields treated by different modes of N application  

SciTech Connect

Methane emission rates from wetland rice fields were determined in Los Banos (Philipppines) using an automatic system that allows continuous measurements over time. Methane emission was monitored in an irrigated Aquandic Epiaqualf planted to rice cultivar IR72. Urea fertilizer was applied using four modes: (1) broadcast 10 days after transplanting, (2) broadcast at transplanting, (3) broadcast and incorporated at final harrowing, and (4) deep placement as sulfur-coated granules. The treatments were laid out in a randomized complete block design with four replicates. Measurements were done in the 1991 wet season, 1992 dry season (four treatments), and the 1992 wet season (only treatment 3). Methane emission rates from the experimental plots showed pronounced season and diel variations. The diel pattern of methane emission rates followed a consistent pattern, with highest rates observed in the early afternoon and lowest rates in the early morning. Methane emission rate was generally highest at the ripening stage. The average methane emission rate during the 1992 dry season (190 mg CH{sub 4} m{sup {minus}2} d{sup {minus}1}) exceeded the average flux rates of the 1992 wet season (79 mg CH{sub 4} m{sup {minus}2} d{sup {minus}1}) by a factor of 2.4. The total methane emitted from these flooded rice fields amounted to 19 g CH{sub 4} m{sup {minus}2} in the dry season with rice yields of 5.2-6.3 ha{sup {minus}1} and 7 g CH{sub 4} m{sup {minus}2} in the wet season with rice yields of 2.4-3.3 t ha{sup {minus}1} regardless of the mode of N application. Significant amounts corresponding to 20% of the methane released under waterlogged conditions were released when the soil was drained after harvest. Emission rates increased sharply when the floodwater receded and macropores started to drain. Emission of methane stopped only when the soil became fully aerated. 25 refs., 5 figs., 1 tab.

Wassmann, R. [International Rice Research Institute, Los Banos (Philippines)] [International Rice Research Institute, Los Banos (Philippines); [Fraunhofer Institute for Atmospheric Environmental Research, Garmisch-Partenkirchen (Germany); Neue, H.U.; Lantin, R.S.; Aduna, J.B.; Alberto, M.C.R.; Andales, M.J.; Tan, M.J. [International Rice Research Institute, Los Banos (Philippines)] [International Rice Research Institute, Los Banos (Philippines); Hoffmann, H.; Papen, H. [Fraunhofer Institute for Atmospheric Environmental Research, Garmisch-Partenkirchen (Germany)] [Fraunhofer Institute for Atmospheric Environmental Research, Garmisch-Partenkirchen (Germany); Gon, H.A.C. D. van der [Agricultural Univ., Wageningen (Netherlands)

1994-08-20

286

Methane emissions from beef cattle: Effects of monensin, sunflower oil, enzymes, yeast, and fumaric acid.  

PubMed

Methane emitted from the livestock sector contributes to greenhouse gas (GHG) emissions. Understanding the effects of diet on enteric methane production can help refine GHG emission inventories and identify viable GHG reduction strategies. Our study focused on measuring methane and carbon dioxide emissions, total-tract digestibility, and ruminal fermentation in growing beef cattle fed a diet supplemented with various additives or ingredients. Two experiments, each designed as a 4 x 4 Latin square with 21-d periods, were conducted using 16 Holstein steers (initial BW 311.6 +/- 12.3 kg). In Exp. 1, treatments were control (no additive), monensin (Rumensin, Elanco Animal Health, Indianapolis, IN; 33 mg/kg DM), sunflower oil (400 g/d, approximately 5% of DMI), and proteolytic enzyme (Protex 6-L, Genencor Int., Inc., CA; 1 mL/kg DM). In Exp. 2, treatments were control (no additive), Procreatin-7 yeast (Prince Agri Products, Inc., Quincy, IL; 4 g/d), Levucell SC yeast (Lallemand, Inc., Rexdale, Ontario, Canada; 1 g/d), and fumaric acid (Bartek Ingredients Inc., Stoney Creek, Ontario, Canada; 80 g/d). The basal diet consisted of 75% barley silage, 19% steam-rolled barley grain, and 6% supplement (DM basis). Four large chambers (two animals per chamber) were equipped with lasers and infrared gas analyzers to measure methane and carbon dioxide, respectively, for 3 d each period. Total-tract digestibility was determined using chromic oxide. Approximately 6.5% of the GE consumed was lost in the form of methane emissions from animals fed the control diet. In Exp. 1, sunflower oil decreased methane emissions by 22% (P = 0.001) compared with the control, whereas monensin (P = 0.44) and enzyme had no effect (P = 0.82). However, oil decreased (P = 0.03) the total-tract digestibility of NDF by 20%. When CH(4) emissions were corrected for differences in energy intake, the loss of GE to methane was decreased by 21% (P = 0.002) using oil and by 9% (P = 0.09) using monensin. In Exp. 2, Procreatin-7 yeast (P = 0.72), Levucell SC yeast (P = 0.28), and fumaric acid (P = 0.21) had no effect on methane emissions, although emissions as a percentage of GE intake were 3% (non-significant, P = 0.39) less for steers fed Procreatin-7 yeast compared with the control. This study demonstrates that sunflower oil, ionophores, and possibly some yeast products can be used to decrease the GE lost as methane from cattle, but fiber digestibility is impaired with oil supplementation. PMID:15542482

McGinn, S M; Beauchemin, K A; Coates, T; Colombatto, D

2004-11-01

287

A model of the methane cycle, permafrost, and hydrology of the Siberian continental margin  

NASA Astrophysics Data System (ADS)

A two-dimensional model of a passive continental margin was adapted to the simulation of the methane cycle on Siberian continental shelf and slope, attempting to account for the impacts of glacial/interglacial cycles in sea level, alternately exposing the continental shelf to freezing conditions with deep permafrost formation during glacial times, and immersion in the ocean in interglacial times. The model is used to gauge the impact of the glacial cycles, and potential anthropogenic warming in the deep future, on the atmospheric methane emission flux, and the sensitivities of that flux to processes such as permafrost formation and terrestrial organic carbon (Yedoma) deposition. Hydrological forcing drives a freshening and ventilation of pore waters in areas exposed to the atmosphere, which is not quickly reversed by invasion of seawater upon submergence, since there is no analogous saltwater pump. This hydrological pump changes the salinity enough to affect the stability of permafrost and methane hydrates on the shelf. Permafrost formation inhibits bubble transport through the sediment column, by construction in the model. The impact of permafrost on the methane budget is to replace the bubble flux by offshore groundwater flow containing dissolved methane, rather than accumulating methane for catastrophic release when the permafrost seal fails during warming. By far the largest impact of the glacial/interglacial cycles on the atmospheric methane flux is attenuation by dissolution of bubbles in the ocean when sea level is high. Methane emissions are highest during the regression (soil freezing) part of the cycle, rather than during transgression (thawing). The model-predicted methane flux to the atmosphere in response to a warming climate is small, relative to the global methane production rate, because of the ongoing flooding of the continental shelf. A slight increase due to warming could be completely counteracted by sea level rise on geologic time scales, decreasing the efficiency of bubble transit through the water column. The methane cycle on the shelf responds to climate change on a long time constant of thousands of years, because hydrate is excluded thermodynamically from the permafrost zone by water limitation, leaving the hydrate stability zone at least 300 m below the sediment surface.

Archer, D.

2014-06-01

288

Climate-methane cycle feedback in global climate model model simulations forced by RCP scenarios  

NASA Astrophysics Data System (ADS)

Methane cycle module of the global climate model of intermediate complexity developed at the A.M. Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences (IAP RAS CM) is extended by coupling with a detailed module for thermal and hydrological processes in soil (Deep Soil Simulator, (Arzhanov et al., 2008)). This is an important improvement with respect with the earlier IAP RAS CM version (Eliseev et al., 2008) which has employed prescribed soil hydrology to simulate CH4 emissions from soil. Geographical distribution of water inundated soil in the model was also improved by replacing the older Olson's ecosystem data base by the data based on the SCIAMACHY retrievals (Bergamaschi et al., 2007). New version of the IAP RAS CM module for methane emissions from soil is validated by using the simulation protocol adopted in the WETCHIMP (Wetland and Wetland CH4 Inter-comparison of Models Project). In addition, atmospheric part of the IAP RAS CM methane cycle is extended by temperature dependence of the methane life-time in the atmosphere in order to mimic the respective dependence of the atmospheric methane chemistry (Denisov et al., 2012). The IAP RAS CM simulations are performed for the 18th-21st centuries according with the CMIP5 protocol taking into account natural and anthropogenic forcings. The new IAP RAS CM version realistically reproduces pre-industrial and present-day characteristics of the global methane cycle including CH4 concentration qCH4 in the atmosphere and CH4 emissions from soil. The latter amounts 150 - 160 TgCH4-yr for the late 20th century and increases to 170 - 230 TgCH4-yr in the late 21st century. Atmospheric methane concentration equals 3900 ppbv under the most aggressive anthropogenic scenario RCP 8.5 and 1850 - 1980 ppbv under more moderate scenarios RCP 6.0 and RCP 4.5. Under the least aggressive scenario RCP 2.6 qCH4 reaches maximum 1730 ppbv in 2020s and declines afterwards. Climate change impact on the methane emissions from soil enhances build up of the methane stock in the atmosphere by 10 - 25% depending on anthropogenic scenario and time instant. In turn, decrease of methane life-time in the atmosphere suppresses this build up by 5 - 40%. The net effect is uncertain but small in terms of resulting additional greenhouse radiative forcing. This smallness is reflected in small additional (relative to the model version with both methane emissions from soil and methane life-time in the atmosphere fixed at their preindustrial values) near-surface warming which globally is not larger than 1 K, i.e, ˜ 4% of warming exhibited by the model version neglecting climate-methane cycle interaction. References [1] M.M. Arzhanov, P.F. Demchenko, A.V. Eliseev, and I.I. Mokhov. Simulation of characteristics of thermal and hydrologic soil regimes in equilibrium numerical experiments with a climate model of intermediate complexity. Izvestiya, Atmos. Ocean. Phys., 44(5):279-287, 2008. doi: 10.1134/S0001433808050022. [2] P. Bergamaschi, C. Frankenberg, J.F. Meirink, M. Krol, F. Dentener, T. Wagner, U. Platt, J.O. Kaplan, S. Körner, M. Heimann, E.J. Dlugokencky, and A. Goede. Satellite chartography of atmospheric methane from SCIAMACHY on board ENVISAT: 2. Evaluation based on inverse model simulations. J. Geophys. Res., 112(D2):D02304, 2007. doi: 10.1029/2006JD007268. [3] S.N. Denisov, A.V. Eliseev, and I.I. Mokhov. Climate change in the IAP RAS global model with interactive methane cycle under RCP anthropogenic scenarios. Rus. Meteorol. Hydrol., 2012. [submitted]. [4] A.V. Eliseev, I.I. Mokhov, M.M. Arzhanov, P.F. Demchenko, and S.N. Denisov. Interaction of the methane cycle and processes in wetland ecosystems in a climate model of intermediate complexity. Izvestiya, Atmos. Ocean. Phys., 44(2):139-152, 2008. doi: 10.1134/S0001433808020011.

Eliseev, Alexey V.; Denisov, Sergey N.; Arzhanov, Maxim M.; Mokhov, Igor I.

2013-04-01

289

Detection and Monitoring of Changing Natural Methane Emissions in the Arctic  

NASA Astrophysics Data System (ADS)

Climate models suggest that the future Arctic climate will continue to warm and become wetter as well. This implies increased emissions of CH4 from wetlands, however, the future of Arctic hydrology is uncertain given expected melting of permafrost. In addition, vast stores of organic carbon are thought to be frozen in Arctic soils; as much as 1,700 billion tonnes of carbon, several times the amount emitted by fossil fuel use to date and about equal to known coal reserves. If mobilized to the atmosphere, this carbon would have significant impacts on global climate, especially if emitted as CH4. NOAA ESRL, Environment Canada, and other agencies have collected observations of greenhouse gases in the Arctic and the rest of the world for at least several decades. Analysis of this data does not currently support increased Arctic emissions of CO2 or CH4. However, it is difficult to detect changes in Arctic emissions because of transport from lower latitudes and high inter-annual variability. Arctic surface emissions are also especially difficult to detect from space, and current satellite platforms do not provide useful information about greenhouse gas budgets in the lower Arctic troposphere. Modeling/assimilation systems, such as NOAA's CarbonTracker-CH4 system can help untangle the Arctic budget and trends of greenhouse gases. On the other hand, the CarbonTracker is dependent on assumptions about prior fluxes and wetland distributions and source estimates are highly uncertain. We address the plausibility of monitoring the Arctic greenhouse gas emission trends. How large would Arctic emission trends have to be before they could be identified in network observations? What spatial information could be recovered? How would the spatial density of observations affect our ability to perceive and attribute trends in Arctic emissions? Could emission have already been increasing during the close of the 20th century? Trends in emissions need to be large before they can be discerned in network observations; our calculations show that emissions of methane must increase by at least 5TgCH4/yr to be seen in a 10-year observational record. The current NASA CARVE mission has the potential to improve prior flux estimates by providing information on how small scale emission processes can be translated to regional scales by a combination of ground-based and aircraft platform measurements of atmospheric concentrations and important surface state variables, and we provide an update on lessons learned so far from the CARVE mission.

Bruhwiler, L.; Sweeney, C.; Dlugokencky, E. J.; Miller, J. B.; Karion, A.; Miller, C. E.

2012-12-01

290

A synthesis of methane emissions from 71 northern, temperate, and subtropical wetlands.  

PubMed

Wetlands are the largest natural source of atmospheric methane. Here, we assess controls on methane flux using a database of approximately 19 000 instantaneous measurements from 71 wetland sites located across subtropical, temperate, and northern high latitude regions. Our analyses confirm general controls on wetland methane emissions from soil temperature, water table, and vegetation, but also show that these relationships are modified depending on wetland type (bog, fen, or swamp), region (subarctic to temperate), and disturbance. Fen methane flux was more sensitive to vegetation and less sensitive to temperature than bog or swamp fluxes. The optimal water table for methane flux was consistently below the peat surface in bogs, close to the peat surface in poor fens, and above the peat surface in rich fens. However, the largest flux in bogs occurred when dry 30-day averaged antecedent conditions were followed by wet conditions, while in fens and swamps, the largest flux occurred when both 30-day averaged antecedent and current conditions were wet. Drained wetlands exhibited distinct characteristics, e.g. the absence of large flux following wet and warm conditions, suggesting that the same functional relationships between methane flux and environmental conditions cannot be used across pristine and disturbed wetlands. Together, our results suggest that water table and temperature are dominant controls on methane flux in pristine bogs and swamps, while other processes, such as vascular transport in pristine fens, have the potential to partially override the effect of these controls in other wetland types. Because wetland types vary in methane emissions and have distinct controls, these ecosystems need to be considered separately to yield reliable estimates of global wetland methane release. PMID:24777536

Turetsky, Merritt R; Kotowska, Agnieszka; Bubier, Jill; Dise, Nancy B; Crill, Patrick; Hornibrook, Ed R C; Minkkinen, Kari; Moore, Tim R; Myers-Smith, Isla H; Nykänen, Hannu; Olefeldt, David; Rinne, Janne; Saarnio, Sanna; Shurpali, Narasinha; Tuittila, Eeva-Stiina; Waddington, J Michael; White, Jeffrey R; Wickland, Kimberly P; Wilmking, Martin

2014-07-01

291

Mechanisms of crop management impact on methane emissions from rice fields in Los Baños, Philippines  

Microsoft Academic Search

\\u000a This article comprises 4 yr of field experiments on methane (CH4) emissions from rice fields conducted at Los Baños, Philippines. The experimental layout allowed automated measurements of\\u000a CH4 emissions as affected by water regime, soil amendments (mineral and organic), and cultivars. In addition to emission records\\u000a over 24 h, ebullition and dissolved CH4 in soil solution were recorded in weekly

R. Wassmann; L. V. Buendia; R. S. Lantin; C. S. Bueno; L. A. Lubigan; A. Umali; N. N. Nocon; A. M. Javellana; H. U. Neue

292

Effects of vegetation on the emission of methane from submerged paddy soil  

Microsoft Academic Search

Summary  Methane emission rates from rice-vegetated paddy fields followed a seasonal pattern different to that of weed-covered or unvegetated\\u000a fields. Presence of rice plants stimulated the emission of CH4 both in the laboratory and in the field. In unvegetated paddy fields CH4 was emitted almost exclusively by ebullition. By contrast, in rice-vegetated fields more than 90% of the CH4 emission was

A. Holzapfel-Pschorn; R. Conrad; W. Seiler

1986-01-01

293

Record of methane emissions from the Arctic during the last Deglaciation  

NASA Astrophysics Data System (ADS)

The methane hydrates of the Arctic represent potentially significant carbon resources that are sensitive to climate change. Methane hydrate provinces are widespread in the Arctic, but their stability and longevity through time, and the significance of their contribution to the global carbon budget, is still poorly understood. It is, therefore, critical to resolve the frequency of methane (CH4) seafloor emissions through time, in relation to past climate change with a special focus on periods of climate warming. The values of ?13C in benthic foraminifera have been measured in two cores, one collected from an area of active methane venting and one from an inactive area on the Vestnesa Ridge (NW Svalbard continental margin), in order to reconstruct the local history of methane emissions over the past 16,000 years BP. The chronostratigraphic framework of the cores has been derived from biostratigraphic analysis and AMS 14C dates. While foraminifera from some intervals have ?13C within the normal marine range (0 to -1), several intervals are characterized by much lower ?13C, as low as -17.4o in the active core and as low as -4.37o in the inactive core. These intervals are interpreted to record the incorporation of 13C-depleted carbon in the presence of methane emissions at the seafloor during biomineralization of the carbonate foraminiferal tests and subsequent secondary mineralization. The longest of these 'methane emission events' (MEE) coincides with the start of the warm Bølling-Allerød Interstadial (GI-1 in the Greenland ice core record). The lack of correlation between the values of ?13C and ?18O, however, appears to preclude warming of bottom waters as the principal control on methane release. Rather, it seems likely that methane release is related to changes in gas migration pathways, or other geological processes still under debate. Details on the CAGE research plan and organization can be found on www.cage.uit.no to foster opportunities for cross-disciplinary collaboration. Based in Tromsø, at the world's northernmost University, CAGE establishes the intellectual and infrastructure resources for studying the amount of methane hydrate and magnitude of methane release in Arctic Ocean environments on time scales from the Neogene to the present. The Centre of Excellence is funded by the Norwegian Research Council (grant No. 223259) over a period of ten years.

Panieri, Giuliana; Consolaro, Chiara; James, Rachael; Westbrook, Graham; Rasmussen, Tine; Mienert, Jürgen

2014-05-01

294

Natural emissions of methane from geothermal and volcanic sources in Europe  

NASA Astrophysics Data System (ADS)

It has recently been demonstrated that methane emission from lithosphere degassing is an important component of the natural greenhouse-gas atmospheric budget. Globally, the geological sources are mainly due to seepage from hydrocarbon-prone sedimentary basins, and subordinately from geothermal/volcanic fluxes. This work provides a first estimate of methane emission from the geothermal/volcanic component at European level. In Europe, 28 countries have geothermal systems and at least 10 countries host surface geothermal manifestations (hot springs, mofettes, gas vents). Even if direct methane flux measurements are available only for a few small areas in Italy, a fair number of data on CO 2, CH 4 and steam composition and flux from geothermal manifestations are today available for 6 countries (Czech Republic, Germany, Greece, Iceland, Italy, Spain). Following the emission factor and area-based approach, the available data have been analyzed and have led to an early and conservative estimate of methane emission into the atmosphere around 10,000 ton/yr (4000-16,000 ton/yr), basically from an area smaller than 4000 km 2, with a speculative upper limit in the order of 10 5 ton/yr. Only 4-18% of the conservative estimate (about 720 ton/yr) is due to 12 European volcanoes, where methane concentration in volcanic gases is generally in the order of a few tens of ppmv. Volcanoes are thus not a significant methane source. While the largest emission is due to geothermal areas, which may be situated next to volcanoes or independent. Here inorganic synthesis, thermometamorphism and thermal breakdown of organic matter are substantial. Methane flux can reach hundreds of ton/yr from small individual vents. Geothermal methane is mainly released in three countries located in the main high heat flow regions: Italy, Greece, and Iceland. Turkey is likely a fourth important contributor but the absolute lack of data prevents any emission estimate. Therefore, the actual European geothermal-volcanic methane emission could be easily projected to the 10 5 ton/yr levels, reaching the magnitude of some other natural sources such as forest fires or wild animals.

Etiope, G.; Fridriksson, T.; Italiano, F.; Winiwarter, W.; Theloke, J.

2007-08-01

295

Emission of methane and other trace gases from the Amazon Varzea  

NASA Technical Reports Server (NTRS)

Researchers measured the distributions and fluxes of methane and other trace gases from the various Amazon floodplain environments. These were determined during both a large scale, quasi-synoptic survey along a 2000 km reach of the Amazon river and an intensive local study (by J. Melack, R. Harriss et al.) covering a six-week period. The environments studied included the major rivers, connecting channels (paranas), floating macrophyte beds, flooded forests, open lakes and recently wetted soils. The results are summarized. Measured rates of methane emission averaged about 300 mg m-2 d-1, but with considerable variance, and were comparable to or higher than previously reported emissions from similar temperature zone environments. In general, areas covered by floating macrophytes showed the highest emissions. Individual hotspots had among the highest rates ever observed, over 10 g m-2 d-1. The high methane emissions appear to result because about 50% of the organic matter fixed on the floodplain (either terrestrial or aquatic) that is oxidized in the water is decomposed anaerobically via methanogensis. Measured fluxes of methane to the atmosphere appear to be significantly correlated with surface water dissolved methane concentrations.

Richey, Jeffrey E.; Devol, Allan H.

1986-01-01

296

Methane emission from fields with three various rice straw treatments in Taiwan paddy soils.  

PubMed

Flooded rice fields are one of the major biogenic methane sources. In this study, the effects of straw residual treatments on methane emission from paddy fields were discussed. The experimental field was located at Tainan District Agricultural Improvement Station in Chia-Yi county (23 degrees 25'08''N, 120degrees16'26''E) of southern Taiwan throughout the first and the second crop seasons in 2000. The seasonal methane fluxes in the first crop season with rice stubble removed, rice straw burned and rice straw incorporated were 4.41, 3.78 and 5.27 g CH4 m(-2), and the values were 32.8, 38.9 and 75.1 g CH4 m(-2) in the second crop season, respectively. In comparison of three management methods of rice straw residue, the incorporation of rice straw residue should show a significant tendency for enhancing methane emission in the second crop season. Moreover, stubble removed and straw burned treatments significantly reduced CH4 emissions by 28 approximately 56% emissions compared to straw incorporated plot. Concerning for air quality had led to legislation restricting rice straw burning, removing of rice stubble might be an appropriate methane mitigation strategy in Taiwan paddy soils. PMID:12856932

Liou, Rey-May; Huang, Shan-Ney; Lin, Chin-Wei; Chen, Shin-Hsiung

2003-07-01

297

Wetland methane modelling over the Scandinavian Arctic: Performance of current land-surface models  

NASA Astrophysics Data System (ADS)

Wetlands are generally accepted as being the largest, but least well quantified, single natural source of CH4, with global emission estimates ranging from 100-231 Tg yr-1 [1] and for which the Boreal and Arctic regions make a significant contribution [2, 3]. The recent review by Melton et al. [4] has provided a summary of the current state of knowledge on the modelling of wetlands and the outcome of the WETCHIMP model intercomparison exercise. Melton et al. found a large variation in the wetland areas and associated methane emissions from the participating models and varying responses to climate change. In this paper, we report results from offline runs of two land surface models over Scandinavia (JULES, the Joint UK Land Environment Simulator [5, 6] and HYBRID8 [7]), using the same driving meteorological dataset (CRU-NCEP) for the period from January 1980 to December 2010. Although the two land surface models are very different, both models have used a TOPMODEL approach to derive the wetland area and have similar parameterisations of the methane wetland emissions. We find that both models give broadly similar results. They underestimate the wetland areas over Northern Scandinavia, compared to remote sensing and map-based datasets of wetlands [8]. This leads to lower predicted methane emissions compared to those observed on the ground and from aircraft [9]. We will present these findings and identify possible reasons for the underprediction. We will show the sensitivity to using the observed wetland areas to improve the methane emission estimates. References [1] Denman, K., et al.,: Couplings Between Changes in the Climate System and Biogeochemistry, 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, United Kingdom, 2007; [2] Smith, L. C., et al.: Siberian peatlands a net carbon sink and global methane source since the early Holocene, Science, 303, 353-356, doi:10.1126/science.1090553, 2004; [3] Zhuang, Q., et al.: CO2 and CH4 exchanges between land ecosystems and the atmosphere in northern high latitudes over the 21st century, Geophysical Research Letters, 33, doi:10.1029/2006gl026972, 2006; [4] Melton, J.R., et al.: Present state of global wetland extent and wetland methane modelling: conclusions from a model inter-comparison project (WETCHIMP), Biogeosciences, 10, 753-788, doi:10.5194/bg-10-753-2013, 2013; [5] Best, M. J., et al.: The Joint UK Land Environment Simulator (JULES), model description - Part 1: Energy and water fluxes, Geoscientific Model Development, 4, 677-699, doi:10.5194/gmd-4-677-2011, 2011; [6] Clark, D.B., et al.: The Joint UK Land Environment Simulator (JULES), Model description - Part 2: Carbon fluxes and vegetation. Geoscientific Model Development, 4, 701-722, doi:10.5194/gmd-4-701-2011, 2011; [7] Friend, A.D., and N.Y. Kiang: Land surface model development for the GISS GCM: Effects of improved canopy physiology on simulated climate. J. Climate, 18, 2883-2902, doi:10.1175/JCLI3425.1, 2005; [8] Prigent, C., et al.: Changes in land surface water dynamics since the 1990s and relation to population pressure, Geophys. Res. Lett., 39, L08403, doi:10.1029/2012GL051276, 2012; [9] O'Shea, S., et al.: Methane and carbon dioxide fluxes from the European Arctic wetlands during the MAMM project, paper in preparation.

Hayman, Garry; Quiquet, Aurélien; Gedney, Nicola; Clark, Douglas; Friend, Andrew; George, Charles; Prigent, Catherine

2014-05-01

298

Seasonal dynamics in methane emissions from the Amazon River floodplain to the troposphere  

SciTech Connect

Methane fluxes to the troposphere from the three principal habitats of the floodplain of the Amazon River main stem (open waters, emergent macrophyte beds, and flooded forests) were determined along a 1,700-km reach of the river during the low-water period of the annual flood cycle (November-December 1988). Overall, emissions averaged 68 ({plus minus} 20) mg CH{sub 4} m{sup {minus}2} d{sup {minus}1} and were significantly lower than similar emissions determined previously for the high-water period, 184 ({plus minus} 41) mg CH{sub 4} m{sup {minus}2} d{sup {minus}1} (July-August 1986). This difference was due to significantly lower emissions from floating macrophyte environments. Low-water emissions from open waters and flooded forest areas were not significantly different than at high water. A monthly time series of methane emissions from eight lakes located in the central Amazon basin showed similar results. Average annual emission from the lakes was 125 ({plus minus} 28) mg CH{sub 4} m{sup {minus}2} d{sup {minus}1}. Methane emissions from lakes were significantly higher during the high water period, again primarily due to an increase in emissions from macrophyte habitats. The data were used to calculate a seasonally weighted annual emission to the troposphere from the Amazon River main stem floodplain of 5.1 Tg yr{sup {minus}1}, which indicates the importance of the area in global atmospheric chemistry.

Devol, A.H.; Richey, J.E. (Univ. of Washington, Seattle (USA)); Forsberg, B.R. (Instituto Nacional de Pesquisas da Amazonia, Manaus (Brazil)); Martinelli, L.A. (Centro de Energia Nuclear na Agricultura, Piracicaba (Brazil))

1990-09-20

299

A new ab initio based model potential for methane  

NASA Astrophysics Data System (ADS)

We present a model potential for methane based on BSSE corrected MP3 level interaction energies of 132 methane dimers using the aug(df,pd)-6-311G** basis set (6-311G** basis set augmented with diffuse d and f functions on carbon atoms and diffuse p and d functions on hydrogen atoms). The density, heat of evaporation and self-diffusion coefficient of liquid methane obtained by an MD simulation using the model potential reproduced the experimental values considerably better than the previous model potential based on MP3/6-311G(3d,3p) level interaction energies.

Tsuzuki, Seiji; Uchimaru, Tadafumi; Tanabe, Kazutoshi

1998-05-01

300

Methane Capture: Options for Greenhouse Gas Emission Reduction.  

National Technical Information Service (NTIS)

Research on climate change has identified a wide array of sources that emit greenhouse gases (GHGs). Among the six gases that have generally been the primary focus of concern, methane is the second-most abundant, accounting for approximately 8% of total U...

D. J. Marples J. E. McCarthy J. L. Ramseur K. Bracmort P. Folger

2011-01-01

301

A model for methane production in sewers.  

PubMed

Most sewers in developing countries are combined sewers which receive stormwater and effluent from septic tanks or cesspools of households and buildings. Although the wastewater strength in these sewers is usually lower than those in developed countries, due to improper construction and maintenance, the hydraulic retention time (HRT) could be relatively long and resulting considerable greenhouse gas (GHG) production. This study proposed an empirical model to predict the quantity of methane production in gravity-flow sewers based on relevant parameters such as surface area to volume ratio (A/V) of sewer, hydraulic retention time (HRT) and wastewater temperature. The model was developed from field survey data of gravity-flow sewers located in a peri-urban area, central Thailand and validated with field data of a sewer system of the Gold Coast area, Queensland, Australia. Application of this model to improve construction and maintenance of gravity-flow sewers to minimize GHG production and reduce global warming is presented. PMID:24967565

Chaosakul, Thitirat; Koottatep, Thammarat; Polprasert, Chongrak

2014-09-19

302

Measurements of methane emissions from landfills using mobile plume method with trace gas and cavity ring-down spectroscopy  

NASA Astrophysics Data System (ADS)

Methane is emitted to the atmosphere from both anthropogenic and natural sources. One of the major anthropogenic sources is methane produced by bacteria in anaerobic environments such as rice pads and landfills. Land filling has for many years been the preferred waste disposal method, resulting in a large methane production with a large contribution to the global increase in atmospheric green house gas concentration. Several steps have been taken to reduce the emission of methane from landfills. In order to validate the effect of these steps, a measurement method is needed to quantify methane emissions with a large spatial variation. One method is to use a highly sensitive and fast analytical method, capable of measuring the atmospheric concentration methane downwind from emission areas. Combined with down-wind measurements of a trace gas, emitted at a controlled mass flow rate, the methane emission can be calculated. This method is called the mobile plume method, as the whole plume is measured by doing several transects. In the current study a methane/acetylene analyzer with cavity ring-down spectroscopy detection (Picarro, G2203) was used to estimate methane from a number of Danish landfills. We measured at both active and closed landfills and investigated the difference in methane emission. At landfills where the emissions could have more than one origin, the source strength of the different emission areas was determined by accurate trace gas positioning and choosing appropriate wind speed and measurement distance. To choose these factors, we addressed the uncertainties and limitations of the method with respect to the configuration of the trace gas bottles and the distance between the emission area and the measurement points. Composting of organic material in large piles was done at several of the investigated landfills and where possible, the methane emission from this partly anaerobic digestion was measured as a separate emission.

Mønster, J.; Kjeldsen, P.; Scheutz, C.

2012-04-01

303

First satellite measurements of carbon dioxide and methane emission ratios in wildfire plumes  

NASA Astrophysics Data System (ADS)

Using methane and carbon dioxide atmospheric mixing ratios retrieved using SWIR spectra from the Greenhouse Gases Observing SATellite (GOSAT), we report the first wildfire plume CH4 to CO2 emission ratios (ERCH4/CO2) determined from space. We demonstrate the approach's potential using forward modeling and identify a series of real GOSAT spectra containing wildfire plumes. These show significantly changed total-column CO2 and CH4 mixing ratios, and from these we calculate ERCH4/CO2 for boreal forest, tropical forest, and savanna fires as 0.00603, 0.00527, and 0.00395 mol mol-1, respectively. These ERs are statistically significantly different from each other and from the "normal" atmospheric CH4 to CO2 ratio and generally agree with past ground and airborne studies.

Ross, Adrian N.; Wooster, Martin J.; Boesch, Hartmut; Parker, Robert

2013-08-01

304

New Result on Methane Emissions from the East Siberian Arctic Shelf  

NASA Astrophysics Data System (ADS)

Methane release from thawing Arctic permafrost is one of the few carbon-climate mechanisms that could change projected climate forcing substantially in this century. Venting of methane to the atmosphere in the East Siberian Arctic Shelf, the world's largest yet shallowest shelf, was recently shown to be ubiquitous. Here we report results of multi-year investigations performed in the coastal East Siberian Arctic Shelf (ESAS), where invasion of relatively warm seawater occurred most recently. Observational data and simulation of the warming effect of seawater on subsea permafrost suggest that disintegrating subsea permafrost allows formation of migration pathways for methane bubbles released from the sea floor. Sonar data collected in the coastal area and in the mid-outer shelf area together with data, obtained using high-resolution high-speed video camera, enabled area-weighted methane fluxes to be estimated. New factors controlling spatial and temporal variability of methane fluxes on the ESAS were found. In the outer shelf, it was shown that methane releases from the seabed via strong flare-like ebullition that produces fluxes much greater than on the shallow shelf, where largely frozen sediments restrict fluxes. The coastward progression of thawing subsea permafrost in a warming Arctic could potentially result in a significant increase in methane emissions from the East Siberian Arctic Shelf.

Shakhova, N. E.; Semiletov, I. P.; Sergienko, V.; Lobkovsky, L. I.; Dmitrevsky, N.; Salyuk, A.; Yusupov, V.; Salomatin, A.; Karnaukh, V.; Chernykh, D.; Kosmach, D.; Ananiev, R.; Meluzov, A.; Nicolsky, D.; Panteleev, G.

2013-12-01

305

On the detection of strong emissions of methane in the Arctic using spectral measurements from IASI and GOSAT  

NASA Astrophysics Data System (ADS)

Boreal ecosystems store significant quantities of organic carbon (C) for thousands of years. Most are presently sequestered in permafrost. In recent years, several studies highlighted that climate warming and thawing of permafrost in the Arctic acts on the mobilization of old stored carbon (c) and contribute to a sustained release of methane (CH4) to the atmosphere [1],[2],[3]. Because methane is an important greenhouse gas, it is necessary to estimate his sources and sinks in the Arctic. The objective of this study is to evaluate and quantify methane strong emission in this region of the globe using spectral measurements from two satellite instruments: IASI-MetOp and TANSO-FTS. The Infrared Atmospheric Sounding Interferometer (IASI) is a Fourier transform spectrometer coupled with an integrated imaging system that observes and measures infrared radiation emitted by the Earth and the atmosphere in the spectral range 645-2760cm-1, which covered the methane ?4 and ?3 absorption band[4]. IASI provides global Earth's coverage twice a day and delivers about 1 300 000 spectra per day[5]. The second instrument which we will use in this study is the Thermal And Near-infrared Sensor for Carbon Observation-Fourier Transform Spectrometer (TANSO-FTS), it has a wide TIR band (5,5-14,3?m)which contain the methane ?4absorption band.TANSO-FTS completes one revolution in about 100 minutes and it comes back to the same location in 3 days period. Over these 3 days, FTS takes 56 000 measurements covering the entire globe[6]. To have a good estimation of methane emission above the Arctic, we must exploit a vast amount of spectral information from IASI and TANSO-FTS. But it is well known that performing line-by-line radiative transfer model is a time-consuming process. So, if we need to exploit large data we have to look fast method. In this work, we will use a simple approach based on the Singular Value Decomposition (SVD) to identify spectra over large source of methane. A more accurate algorithm will be used next to perform an accurate retrieval of methane vertical column. References [1] N. Shakhova, I. Semiletov, A. Salyuk, V. Yusupov, D. Kosmach, O.Gustafsson.: Extensive Methane venting to the atmosphere from sediments of the East Siberian Arctic shelf, SCIENCE 5 March 2010, Vol 327. [2] K. Negandhi, I. Laurion, M. J. Whiticar, P. E. Galand, X. X. Connie Lovejoy.: Small thaw ponds: An unaccounted source of methane in the canadian high Arctic, PLOS ONE november 2013/ vol 8/issue 11/e78204. [3] J. T. Crawford, R. G. Striegl, K. P. Wickland, M . Dornblaser, and E. Stanley.: Emissions of carbon dioxide and methane from a headwater stream network of interior Alaska, Journal of Giophysical Recherch : Biogeosciences, VOL, 118, 482-494, doi:10.1002/jgrg,20034, 2013. [4] A. Razavi, C. Clerbaux, C. Wespes, L. Clarisse, D. Hurtmans, S. Payan, C. Camy-Peyret and P.F. Coheur.: Characterization of methane retrievals from the IASI space-borne sounder , Atmos. Chem. Phys., 9,7889-7899, 2009. [5] C. Clerbaux, A. Boynard, L. Clarisse, M. George, J. Hadji-Lazaro, H. Herbin, D. Hurtmans, M. Pommier, A. Razavi, S. Turquety, C. Wespes and P.-F. Coheur.: Monitoring of atmospheric composition using the thermal infrared IASI/MetOp sounder, Atmos. Chem. Phys., 9, 6041-6054, 2009. [6] T . Yokota, Y. Yoshida, N. Eguchi, Y. Ota, T. Tanaka, H. Watanabe and S. Makasyutov.: Global concentrations of CO2 and CH4 retrieved from GOSAT : First Preliminary Results, SOLA, 2009, Vol. 5, 160-163, doi:10.2151/sola.2009-041.

Bourakkadi, Zakia; Payan, Sébastien; Bureau, Jérôme

2014-05-01

306

NATURAL EMISSIONS OF NON-METHANE VOLATILE ORGANIC COMPOUNDS, CARBON MONOXIDE, AND OXIDES OF NITROGEN FROM NORTH AMERICA. (R825259)  

EPA Science Inventory

Abstract The magnitudes, distributions, controlling processes and uncertainties associated with North American natural emissions of oxidant precursors are reviewed. Natural emissions are responsible for a major portion of the compounds, including non-methane volatile o...

307

NATURAL EMISSIONS OF NON-METHANE VOLATILE ORGANIC COMPOUNDS, CARBON MONOXIDE, AND OXIDES OF NITROGEN FROM NORTH AMERICA  

EPA Science Inventory

The magnitudes, distributions, controlling processes and uncertainties associated with North American natural emissions of oxidant precursors are reviewed. Natural emissions are repsonsible for a major portion of the compounds, including non-methane volatile organic compounds (N...

308

GOOD WIL ‘O THE WISP HUNTING! MEASURING AND MODELING PEATLAND METHANE BUBBLE BUILDUP AND EBULLITION  

NASA Astrophysics Data System (ADS)

Northern peatlands are the largest natural source of atmospheric methane, and it is important to understand the mechanisms of methane loss from these peatlands so that future rates of methane emission can be predicted. Methane is lost to the atmosphere from peatlands by diffusion, by plant transport, and as bubbles (ebullition). We argue that ebullition has not been accounted for properly in many previous studies, both in terms of measurement and the conceptualization of the mechanisms involved. We present a new conceptual model of bubble buildup and release that emphasizes the importance of near-surface peat as a source of atmospheric methane. We also propose a new reduced-complexity approach that conceptualizes bubble buildup and release as broadly similar to an upside down sandpile. Our model allows bubbles to accumulate at different depths within the peat profile according to peat structure, yet it retains the simplicity of many cellular (including cellular automata) models. Comparison of the results from one prototype of our model with data from a laboratory experiment suggests that the model captures some of the key dynamics of ebullition in that it reproduces well observed frequency-magnitude relationships. We outline ways in which the model may be further developed to improve its predictive capabilities.

Waddington, J. M.; Baird, A. J.; Coulthard, T. J.; Ramirez, J.

2009-12-01

309

Effect of plant harvest on methane emission from two constructed wetlands designed for the treatment of wastewater  

Microsoft Academic Search

The emission of methane from two constructed wetlands [a free water surface flow system (FWS) and a subsurface flow system (SF)], constructed for the treatment of waste water, was evaluated at different sites inhabited by reeds (Phragmites communis), to test the effects of plant harvest. High methane emission was recorded immediately after harvesting in both wetlands. Several days after harvesting,

Nanwen Zhu; Ping An; B. Krishnakumar; Ling Zhao; Liwei Sun; Motoyuki Mizuochi; Yuhei Inamori

2007-01-01

310

The response of atmospheric methane concentrations to meteorological forcings of wetland distribution and extent  

NASA Astrophysics Data System (ADS)

Both wetland extent and distribution across the globe are estimated on seasonal and inter-annual timescales in the Simple Biosphere Model. The method is presented and the results are compared with estimates of inundated extent from remote sensing. A model of methane production and consumption is parameterized with data from eddy-covariance measurements of surface methane exchange. Scaled by modeled wetland areas, global patterns of methane emission from wetlands are produced. Modeled methane emissions, along with EDGAR inventories of anthropogenic methane emissions and GFED estimates of methane emissions from biomass burning, drive the GEOS-Chem chemical transport model; producing estimates of atmospheric methane concentrations.

Kraus, P. M.; Denning, A.

2013-12-01

311

Use of multi-transition-metal-ion-exchanged zeolite 13X catalysts in methane emissions abatement  

SciTech Connect

Methane is a potent greenhouse gas. It has a global warming potential (GWP) 23 times greater than carbon dioxide. Reducing methane emissions would lead to substantial economic and environmental benefits. This study investigated the performance of multi-transition-metal-(Cu, Cr, Ni, and Co)-ion-exchanged zeolite 13X catalysts in methane emissions abatement. The catalytic activity in methane combustion using multi-ion-exchanged catalysts was studied with different parameters including the molar percentage of metal loading, the space velocity, and the inlet methane concentration under atmospheric pressure and at a relatively low reaction temperature of 500 C. The performance of the catalysts was determined in terms of the apparent activation energy, the number of active sites of the catalyst, and the BET surface area of the catalyst. This study showed that multi-ion-exchanged catalysts outperformed single-ion-exchanged and acidified 13X catalysts and that lengthening the residence time led to a higher methane conversion percentage. The enhanced catalytic activity in the multi-ion-exchanged catalysts was attributed to the presence of exchanged transition ions instead of acid sites in the catalyst. The catalytic activity of the catalysts was influenced by the metal loading amount, which played an important role in affecting the apparent activation energy for methane combustion, the active sites, and the BET surface area of the catalyst. Increasing the amount of metal loading in the catalyst decreased the apparent activation energy for methane combustion and also the BET surface area of the catalyst. An optimized metal loading amount at which the highest catalytic activity was observed due to the combined effects of the various factors was determined. (author)

Hui, K.S.; Chao, C.Y.H.; Kwong, C.W.; Wan, M.P. [Department of Mechanical Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong (China)

2008-04-15

312

40 CFR Table W - 5 of Subpart W of Part 98-Default Methane Emission Factors for Liquefied Natural Gas (LNG) Storage  

Code of Federal Regulations, 2013 CFR

...Methane Emission Factors for Liquefied Natural Gas (LNG) Storage W Table W...GREENHOUSE GAS REPORTING Petroleum and Natural Gas Systems Definitions. Pt...Methane Emission Factors for Liquefied Natural Gas (LNG) Storage LNG...

2013-07-01

313

Relative contributions of hypoxia and natural gas extraction to atmospheric methane emissions from Lake Erie  

NASA Astrophysics Data System (ADS)

Reduced oxygen availability in lakes due to summer stratification can create conditions suitable for methanogenic activity, which ultimately contributes to atmospheric methane emissions. Lake Erie has persistent low oxygen conditions in bottom waters during summer, which contributes to methane production through anaerobic organic matter respiration. Lake Erie also has substantial subsurface natural gas deposits that are currently being extracted in Canadian waters. We hypothesized that the lake would be a source of methane to the atmosphere in late summer, prior to fall turnover, and that natural gas wells and pipelines would contribute to additional methane emissions from resource extraction areas in Canadian waters. Initial sampling was conducted at a total of 20 sites in central and western Lake Erie during early September 2012. Sites were selected to collect samples from a wide range of environmental conditions in order to better establish the baseline flux from these areas. We selected an array of sites in the offshore environment, sites from a very shallow bay and sites within the Canadian gas fields. Air samples were gathered using floating flux chambers tethered to the research vessel. Dissolved gas water samples were collected using a Van Dorn bottle. We found a consistent positive flux of methane throughout the lake during late summer, with flux rates adjacent to natural gas pipelines up to an order of magnitude greater than elsewhere. Stable isotope analysis yielded results that were not entirely expected. The ?13C of surface samples from areas of fossil fuel extraction and suspected biogenic sources were very similar, likely due to oxidation of methane in the water column. Additional sampling occurred during 2012 and 2013 concentrating on bottom waters and surface fluxes which should allow us to further constrain sources of CH4 from Lake Erie. This project is an effort to constrain the global warming potential of hypoxia in the Great Lakes, and secondly it is an attempt to constrain fugitive emissions of methane from resource extraction areas within Lake Erie. These two sources of methane may contribute to increased greenhouse gas emission rates regionally. In addition, constraining fugitive methane emissions will be an important part of assessing the climate impacts of the coal-to-gas transition.

Disbennett, D. A.; Townsend-Small, A.; Bourbonniere, R.; Mackay, R.

2013-12-01

314

Speciated non-methane organic compounds emissions from food cooking in Mexico  

NASA Astrophysics Data System (ADS)

Non-methane organic compound (NMOC) emissions from different sorts of food preparation sites, were quantified for the first time in Mexico, in order to develop emission profiles for further application in the chemical mass balance receptor model (CMB). Restaurants using charcoal grills and LP gas stoves, "tortiller?´as", food frying places and rotisseries were sampled using SUMMA ® stainless-steel canisters to analyse NMOC by high-resolution gas chromatography. The results obtained show that profiles determined from food cooking processes have similarities to those found in LP gas combustion, which is the most common fuel in Mexico used for this purpose, although there were differences in the relative composition of propane and butane in both cases. This suggests that, the rates of combustion of propane and butane are different. It has also been detected that propene, a reactive olefin is produced during the combustion process. The obtained profiles of restaurants, rotisseries and fried food show an important contribution of two carbon compounds (ethane, ethylene and acetylene) that can be attributed to the complex process of grease and meat cooking. The presence of these compounds cannot be attributed to vehicular sources since the concentrations are higher than in ambient air. These were also determined from aromatic compounds such as benzene, toluene and xylene in the combustion of vegetal charcoal. The measured concentrations indicate that NMOC emissions from cooking may become an important indoor source of NMOC under crowded conditions in closed places.

Mugica, V.; Vega, E.; Chow, J.; Reyes, E.; Sánchez, G.; Arriaga, J.; Egami, R.; Watson, J.

315

Methane emissions along a salt marsh salinity gradient  

Microsoft Academic Search

The seasonal flux of methane to the atmosphere was measured at three salt marsh sites along a tidal creek. Average soil salinities at the sites ranged from 5 to 17 ppt and fluxes ranged from below detection limits (less than 0.3 mgCH4 m-2 d-1) to 259 mgCH4 m-2 d-1. Annual flux to the atmosphere was 5.6 gCH4 m-2 from the

Karen B. Bartlett; David S. Bartlett; Robert C. Harriss; Daniel I. Sebacher

1987-01-01

316

Monitoring methane emission of mud volcanoes by seismic tremor measurements: a pilot study  

NASA Astrophysics Data System (ADS)

A new approach for estimating methane emission at mud volcanoes is here proposed based on measurements of the seismic tremor on their surface. Data obtained at the Dashgil mud volcano in Azerbaijan reveal the presence of energy bursts characterized by well-determined features (i.e. waveforms, spectra and polarization properties) that can be associated with bubbling at depth. Counting such events provides a possible tool for monitoring gas production in the reservoir, thus minimizing logistic troubles and representing a cheap and effective alternative to more complex approaches. Specifically, we model the energy bursts as the effect of resonant gas bubbles at depth. This modelling allows to estimate the dimension of the bubbles and, consequently, the gas outflow from the main conduit in the assumption that all emissions from depth occur by bubble uprising. The application of this model to seismic events detected at the Dashgil mud volcano during three sessions of measurements carried out in 2006 and 2007 provides gas flux estimates that are in line with those provided by independent measurements at the same structure. This encouraging result suggests that the one here proposed could be considered a new promising, cheap and easy to apply tool for gas flux measurements in bubbling gas seepage areas.

Albarello, D.; Palo, M.; Martinelli, G.

2012-12-01

317

Shock-tube and modeling study of methane pyrolysis and oxidation  

SciTech Connect

Methane pyrolysis and oxidation were studied behind reflected shock waves in the temperature range 1350--2400 K at pressures of 1.6 to 4.4 atm. Methane decay in both the pyrolysis and oxidation reactions was measured by using time-resolved infrared (IR) laser absorption at 3.39 {micro}m. CO{sub 2} production was also measured by time-resolved IR emission at 4.24 {micro}m. The production yields were also studied using a single-pulse method. The pyrolysis and oxidation of methane were modeled using a kinetic reaction mechanism including the most recent mechanism for formaldehyde, ketene, acetylene, ethylene, and ethane oxidations. The present and earlier shock tube data is reproduced by the proposed mechanism with 157 reaction steps and 48 species. The reactions and the rate constants, which were important to predict these and earlier shock tube data for methane pyrolysis and the oxidation with mixtures of wide composition from methane-rich to methane-lean, are discussed in detail.

Hidaka, Yoshiaki; Sato, Kazutaka; Henmi, Yusuke; Tanaka, Hiroya; Inami, Koji [Ehime Univ., Matsuyama (Japan). Dept. of Chemistry] [Ehime Univ., Matsuyama (Japan). Dept. of Chemistry

1999-08-01

318

Methane and carbon monoxide emissions from asphalt pavement: Measurements and estimates of their important to global budgets  

SciTech Connect

The authors measured emissions of methane from asphalt surfaces used in pavement for roadways. Maximum emissions were 22 mg/m{sup 2}/hr for 1- to 4-week-old pavement during maximum sunlight intensity. Emissions were much smaller at low sunlight intensity and dropped off to negligible amounts at night. Smaller emissions were observed for asphalt pavement of 2.5 to 3 years approximate age under similar conditions. Comparison measurements of carbon monoxide emissions resulted in maximum emissions of about 2.6 mg/m{sup 2}hr for 1-week-old pavement. These findings indicate that emissions of CH{sub 4} and CO are a function of both sunlight and temperature. Based on these results, methane emissions from asphalt pavement cannot be a significant source of atmospheric methane as compared to other identified methane sources. Therefore, although asphalt methane emissions are a form of fossil fuel methane, they cannot explain the relatively high fraction of {sup 14}C-depleted methane in the atmosphere.

Tyler, S.C.; Dlugokencky, E.; Zimmerman, P.R.; Cicerone, R.J. (National Center for Atmospheric Research, Boulder, CO (USA)); Lowe, D.C. (Institute of Nuclear Sciences, Lower Hutt (New Zealand))

1990-08-20

319

Verification of German methane emission inventories and their recent changes based on atmospheric observations  

NASA Astrophysics Data System (ADS)

Continuous methane concentration records and stable isotope observations measured in the suburbs of Heidelberg, Germany, are presented. While ?13C-CH4 shows a significant trend of -0.14‰ per year, toward more depleted values, no trend is observed in the concentration data. Comparison of the Heidelberg records with clean air observations in the North Atlantic at Izaña station (Tenerife) allows the determination of the continental methane excess at Heidelberg, decreasing by 20% from 190 ppb in 1992 to 150 ppb in 1997. The isotope ratio which is associated with this continental methane pileup in the Heidelberg catchment area shows a significant trend to more depleted values from ?13Csource = -47.4 ± 1.2‰ in 1992 to -52.9 ± 0.4‰ in 1995/1996, pointing to a significant change in the methane source mix. Total methane emissions in the Heidelberg catchment area are estimated using the 222radon (222Rn) tracer method: from the correlations of half-hourly 222Rn and CH4 mixing ratios from 1995 to 1997, and the mean 222Rn exhalation rate from typical soils in the Rhine valley, a mean methane flux of 0.24 ± 0.5 g CH4 km-2 s-1 is derived. For the Heidelberg catchment area with an estimated radius of approximately 150 km, Core Inventories Air 1990 (CORINAIR90) emission estimates yield a flux of 0.47 g CH4 km-2 s-1, which is about 40% higher than the 222Rn-derived number if extrapolated to 1990. The discrepancy can be explained by overestimated emissions from waste management in the CORINAIR90 statistical assessment. The observed decrease in total emissions can be accounted for by decreasing contributions from fossil sources (mainly coal mining) and from cattle breeding. This finding is also supported by the observed decrease in mean source isotopic signatures.

Levin, Ingeborg; Glatzel-Mattheier, Holger; Marik, Thomas; Cuntz, Matthias; Schmidt, Martina; Worthy, Douglas E.

1999-02-01

320

Methane emissions to the troposphere from the Amazon floodplain  

NASA Technical Reports Server (NTRS)

The magnitudes of CH4 emissions to the troposphere from the Amazon River floodplain and the mechanism of these emissions were investigated using the data of 94 individual flux measurements made along a 1700-km stretch of the river during July/August 1985. The overall average rate of CH4 emission from wetlands was found to be 390 mg CH4/sq m per day, with the highest emissions (590 mg CH4/sq m per day) attributed to the water surfaces covered by aquatic macrophytes. Ebullition was the dominant mechanism of emission, accounting for 85 percent of the total. Surface-water CH4 concentrations were highly supersaturated, averaging 6.4 micromolar. The annual emission of CH4 from the Amazon Basin to the troposphere, estimated from the area and the known emission rate, is about 10 CH4 Tg/yr, indicating the importance of the area in the global atmospheric CH4 cycle.

Devol, Allen H.; Richey, Jeffrey E.; Clark, Wayne A.; King, Stagg L.; Martinelli, Luiz A.

1988-01-01

321

Development of equations for predicting methane emissions from ruminants.  

PubMed

Ruminants contribute to global warming by releasing methane (CH4) gas by enteric fermentation. This has increased interest among animal scientists to develop and improve equations predicting CH4 production. The objectives of the current study were to collect a data set from respiration studies and to evaluate the effects of dietary and animal factors on CH4 production from diets that can safely be fed to dairy cows, using a mixed model regression analysis. Therefore, diets containing more than 75% concentrate on a dry matter (DM) basis were excluded from the analysis. The final data set included a total of 298 treatment means from 52 published papers with 207 cattle and 91 sheep diets. Dry matter intake per kilogram of body weight (DMIBW), organic matter digestibility estimated at the maintenance level of feeding (OMDm), and dietary concentrations of neutral detergent fiber (NDF), nonfiber carbohydrates (NFC), and ether extract (EE) were the variables of the best-fit equation predicting CH4 energy (CH4-E) as a proportion of gross energy intake (GE): CH4-E/GE (kJ/MJ)=-0.6 (±12.76) - 0.70 (±0.072) × DMIBW (g/kg) + 0.076 (±0.0118) × OMDm (g/kg) - 0.13 (±0.020) × EE (g/kg of DM) + 0.046 (±0.0097) × NDF (g/kg of DM) + 0.044 (±0.0094) × NFC (g/kg of DM), resulting in the lowest root mean square error adjusted for random study effect (adj. RMSE=3.26 kJ/MJ). Total CH4 production (L/d) in the cattle data set was closely related to DM intake. However, further inclusion of other variables improved the model: CH4 (L/d)=-64.0 (±35.0) + 26.0 (±1.02) × DM intake (kg/d) - 0.61 (±0.132) × DMI(2)(centered) + 0.25 (±0.051) × OMDm (g/kg) - 66.4 (±8.22) × EE intake (kg of DM/d) - 45.0 (±23.50) × NFC/(NDF + NFC), with adj. RMSE of 21.1 L/d. Cross-validation of the CH4-E/GE equation [observed CH4-E/GE=0.96 (±0.103) × predicted CH4-E/GE + 2.3 (±7.05); R(2)=0.85, adj. RMSE=3.38 kJ/MJ] indicated that differences in CH4 production between the diets could be predicted accurately. We conclude that feed intake is the main determinant of total CH4 production and that CH4-E/GE is negatively related to feeding level and dietary fat concentration and positively to diet digestibility, whereas dietary carbohydrate composition has only minor effects. PMID:23403199

Ramin, M; Huhtanen, P

2013-04-01

322

Encapsulated fumaric acid as a feed ingredient to decrease ruminal methane emissions  

Microsoft Academic Search

Decreasing methanogenesis in ruminants would benefit the agricultural industry because it would lead to lower energy losses from the animals as well as being beneficial for the environment in decreasing emissions of a greenhouse gas. Fumaric acid (FA) as a feed supplement has the potential to decrease methane production as well as increase glucogenesis and hence milk yield, but the

T. A. Wood; R. J. Wallace; A. Rowe; J. Price; D. R. Yáñez-Ruiz; P. Murray; C. J. Newbold

2009-01-01

323

Methane Emissions from Four Working Places in the Beckley Mine, Raleigh County, W. Va.  

National Technical Information Service (NTIS)

The Beckley Mine is one of five new mines in a heretofore unmined portion of the Beckley coalbed. The remoteness of these new mines from prior mining and their greater overburden preclude applying methane emission experience obtained in the old mines. Fou...

P. W. Jeran D. H. Lawhead M. C. Irani

1977-01-01

324

Methane emission from natural wetlands: interplay between emergent macrophytes and soil microbial processes. A mini review  

Microsoft Academic Search

Background: According to the Intergovernmental Panel on Climate Change (IPCC) 2007, natural wetlands contribute 20–39 % to the global emission of methane. The range in the estimated percentage of the contribution of these systems to the total release of this greenhouse gas is large due to differences in the nature of the emitting vegetation including the soil microbiota that interfere

H. J. Laanbroek

2010-01-01

325

MTBE, methane, ethylene and regulated exhaust emissions from vehicles with deactivated catalytic converters  

Microsoft Academic Search

In the present work, the effect of the gradual deactivation of a three-way catalytic converter on the exhaust emissions was studied. The exhaust gases were analyzed for CO, HC (i.e. total unburned organic compounds), MTBE, methane and ethylene, before and after their catalytic treatment, in a wide range of engine operating conditions. The thermal aging of the catalytic converter resulted

S. G. Poulopoulos; C. J. Philippopoulos

2004-01-01

326

Methane emissions measured at two California landfills by OTM-10 and an acetylene tracer method  

EPA Science Inventory

Methane emissions were measured at two municipal solid waste landfills in California using static flux chambers, an optical remote sensing approach known as vertical radial plume mapping (VRPM) using a tunable diode laser (TDL) and a novel acetylene tracer method. The tracer meth...

327

Global impacts of sulfate deposition from acid rain on methane emissions from natural wetlands  

Microsoft Academic Search

Natural wetlands form the largest methane (CH_4) source to the atmosphere. A collection of recent field and laboratory studies point to an anthropogenic control on CH_4 emissions from these systems: acid rain sulfate (SO_42-) deposition. These studies ranging from the UK, USA, Canada, Sweden and Czech Republic demonstrate that low rates of SO_42- deposition, within the range commonly experienced in

V. Gauci

2003-01-01

328

Ultraviolet-Visible and Infrared Emission Spectra of Propagating Methane-Coal-Dust Inhibitor Flames.  

National Technical Information Service (NTIS)

Ultraviolet-visible and infrared emission spectra from propagating methane-coal-dust-inhibitor mixtures have been obtained in a 0.2-by 0.2-by 5.3-m vertical duct over a range of flame speeds from 2 to 100 m/sec. Results serve as a basis for the design and...

Z. J. Fink L. E. Dalverny J. Grumer

1974-01-01

329

METHOD 25 - DETERMINATION OF TOTAL GASEOUS NON-METHANE ORGANIC EMISSIONS AS CARBON FROM STATIONARY SOURCES  

EPA Science Inventory

Section 3.17 describes the procedures and specifications for determining volatile organic compounds as total gaseous non-methane organics from stationary sources. n emission sample is withdrawn from the stack at a constant rate through a heated filter and a chilled condensate tra...

330

Impact of phosphorus supply on root exudation, aerenchyma formation and methane emission of rice plants  

Microsoft Academic Search

This study evaluated the impact of P supply on rice plant development and the methane budget of rice fields by 2 different approaches: (1) root growth, exudation and aerenchyma formation were recorded in an experiment with hydroponic solution; (2) dissolved CH4 concentration and CH4 emission were investigated in a pot experiment. In both approaches, we used three different cultivars and

Y. Lu; R. Wassmann; H. U. Neue; C. Huang

1999-01-01

331

Methane emission from fixed dome biogas plants in hilly and plain regions of northern India  

Microsoft Academic Search

Methane emissions from the slurry displacement chambers of different fixed dome type biogas plants (Capacity 2 m3) installed in hilly and plain regions of northern India were quantitatively estimated. The slurry temperature in the biogas plants in the hilly areas of Himachal Pradesh at an altitude of 1300 m above mean sea level remains below the lower mesophilic range (16–25

R. S Khoiyangbam; Sushil Kumar; M. C Jain; Navindu Gupta; Arun Kumar; Vinod Kumar

2004-01-01

332

Deglacial methane emission signals in the carbon isotopic record of Lake Baikal  

Microsoft Academic Search

Changes in the concentrations of atmospheric greenhouse gases constitute an important part of global climate forcing. Here we present the first continental evidence for climatically caused changes in a methane gas hydrate reservoir. The organic carbon stable isotope record from Lake Baikal during the past 130?000 years registers regular emissions of isotopically light carbon by the occurrence of distinct negative

Alexander A. Prokopenko; Douglas F. Williams

2004-01-01

333

Atmospheric methane observed from space over the Asian monsoon: implications for emission from Asian rice paddies  

NASA Astrophysics Data System (ADS)

More than 40% of anthropogenic emissions of methane, the second most important greenhouse gas, is estimated to be from agricultural sources, including rice cultivation. Unfortunately, the strength of individual sources of methane remains uncertain, despite the importance of its effect in global warming. Here we focus on the Asian monsoon region to improve our understanding of methane emission from rice paddy fields. This region contains about 90% of the world’s rice fields. We analyze the temporal and spatial distribution of atmospheric methane concentrations observed from space and compare it with ground-based measurements and bottom-up emission inventory data coupled with rice field maps. Recently, Frankenberg et al. [2008] derived an updated version of methane concentration from the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY: SCIA hereafter) instrument onboard ENVISAT. This showed a clear signature of methane enhancement over the Asian monsoon. As SCIA retrievals include all involve column densities, we carefully examined potential biases and variability due to the gradient of methane concentration over source regions by comparing these data with ground-based measurements at 53 stations of the WDCGG network. After evaluating the bias and variability of methane concentration over the source regions, we examined selected areas where rice paddies were highly concentrated, and the methane emission inventories were estimated to be large. The sampled areas were North and South India, Bangladesh, Myanmar, Thailand, South China, and the Sichuan Basin. All of these are known to be major rice cultivation areas. The time series of monthly mean SCIA retrievals were compared with the emission inventory data for rice cultivation archived in the GISS dataset and Yan et al. [2009], as well as with precipitation data (Huffman et al., 1997). The phase of seasonal variation of SCIA retrievals corresponded closely to those of emission inventories. High methane concentrations were observed in the later period of the rainy season for each area. The amplitude of seasonal variation was large compared with the possible bias over the source regions, demonstrating the reliability of the analysis. We are planning to extend the analysis to the methane data observed by the Thermal And Near infrared Sensor for carbon Observations Fourier Transform Spectrometer (TANSO-FTS) onboard the Greenhouse gases Observing SATellite (GOSAT). GOSAT was launched successfully on January 23, 2009, and has been operating continuously since then. The TANSO-FTS will provide important information on methane emission from rice paddies with good spatial resolution (10 km in diameter). Preliminary results from this instrument will also be presented. References: Frankenberg, et al. (2008), Geophys. Res. Lett., 35, doi:10.1029/2008GL034300. Huffman et al. (1997), Bull. Am. Meteorol. Soc. Vol. 78, 5-20. Yan et al., (2009), Global Biogeochem. Cycles, 23, GB2002, doi:10.1029 /2008GB003299.

Hayashida, S.; Yoshizaki, S.; Frankenberg, C.; Yan, X.

2010-12-01

334

Methane emissions from the natural gas industry. Report for May-December 1992  

SciTech Connect

The paper discusses a project to quantify methane (CH4) emissions from the U.S. natural gas industry. The study will measure or calculate all gas industry CH4 emissions--from production at the wellhead, through the system, to the customer's meter. Emissions downstream of the consumer's meter, such as the end-user's burner emissions, are not included. When these data are combined with data from other studies, a definite comparison of the relative environmental impact of using natural gas versus other fuels will be possible. The study will also provide data that can be used by the industry to identify cost-effective mitigation techniques to reduce losses.

Harrison, M.R.; Cowgill, R.M.; Campbell, L.M.; Lott, R.A.

1993-01-01

335

Remote Sensing of Nitrous Oxide and Methane Using Emission Lines of a CO Overtone Laser  

NASA Astrophysics Data System (ADS)

We have conducted laboratory experiments on remote sensing of methane in the 3.440 ?m region and nitrous oxide in the 3.877 ?m region, using emission lines of a CO overtone laser in the differential absorption method. We present the results of measurements of absorption and extinction of the emission lines from an CO overtone laser in the region of selected sensing wavelengths in mixtures with the analyte gases for different experimental configurations.

Ionin, A. A.; Klimachev, Yu. M.; Kozlov, A. Yu.; Kotkov, A. A.; Romanovskii, O. A.; Kharchenko, O. V.; Yakovlev, S. V.

2014-05-01

336

Ion beam emission in a low energy plasma focus device operating with methane  

Microsoft Academic Search

An investigation of ion beam emission from a low energy plasma focus (PF) device operating with methane is reported. Graphite collectors, operating in the bias ion collector mode, are used to estimate the energy spectrum and ion flux along the PF axis, using the time-of-flight technique. The ion beam signals are time correlated with the emission of soft x-ray pulses

H. Bhuyan; H. Chuaqui; M. Favre; I. Mitchell; E. Wyndham

2005-01-01

337

Processes involved in formation and emission of methane in rice paddies  

Microsoft Academic Search

The seasonal change of the rates of production and emission of methane were determined under in-situ conditions in an Italian rice paddy in 1985 and 1986. The contribution to total emission of CH4 of plant-mediated transport, ebullition, and diffusion through the flooding water was quantified by cutting the plants and by trapping emerging gas bubbles with funnels. Both production and

Helmut Schütz; Wolfgang Seiler; Ralf Conrad

1989-01-01

338

Detection of H alpha emission in a methane (T type) brown dwarf  

NASA Technical Reports Server (NTRS)

We report the detection of H alpha emission in the T dwarf (methane brown dwarf) 2MASSW J1237392 + 652615 over three days using the Keek Low esolution Imaging Spectrograph. The measured line flux, log (L-H alpha/L-bol) = -4.3, is roughly consistent with early M dwarf activity levels and inconsistent with decreasing activity trends in late M and L dwarfs. Similar emission is not seen in two other T dwarfs.

Burgasser, A.; Kirkpatrick, J.; Reid, I.; Liebert, J.; Gizis, J.; Brown, M.

2000-01-01

339

Voyager 1 imaging and IRIS observations of Jovian methane absorption and thermal emission: Implications for cloud structure  

NASA Technical Reports Server (NTRS)

Images from three filters of the Voyager 1 wide angle camera are used to measure the continuum reflectivity and spectral gradient near 6000 A and the 6190 A band methane/continuum ratio for a variety of cloud features in Jupiter's atmosphere. The dark barge features in the North Equatorial Belt have anomalously strong positive continuum spectral gradients suggesting unique composition. Methane absorption is shown at unprecedented spatial scales for the Great Red Spot and its immediate environment, for a dark barge feature in the North Equatorial Belt, and for two hot spot and plume regions in the North Equatorial Belt. Methane absorption and five micrometer emission are correlated in the vicinity of the Great Red Spot but are anticorrelated in one of the plume hot spot regions. Methane absorption and simultaneous maps of five micrometer brightness temperature is quantitatively compared to realistic cloud structure models which include multiple scattering at five micrometer as well as in the visible. Variability in H2 quadrupole lines are also investigated.

West, R. A.; Kupferman, P. N.; Hart, H.

1984-01-01

340

Toward a better understanding and quantification of methane emissions from shale gas development.  

PubMed

The identification and quantification of methane emissions from natural gas production has become increasingly important owing to the increase in the natural gas component of the energy sector. An instrumented aircraft platform was used to identify large sources of methane and quantify emission rates in southwestern PA in June 2012. A large regional flux, 2.0-14 g CH4 s(-1) km(-2), was quantified for a ? 2,800-km(2) area, which did not differ statistically from a bottom-up inventory, 2.3-4.6 g CH4 s(-1) km(-2). Large emissions averaging 34 g CH4/s per well were observed from seven well pads determined to be in the drilling phase, 2 to 3 orders of magnitude greater than US Environmental Protection Agency estimates for this operational phase. The emissions from these well pads, representing ? 1% of the total number of wells, account for 4-30% of the observed regional flux. More work is needed to determine all of the sources of methane emissions from natural gas production, to ascertain why these emissions occur and to evaluate their climate and atmospheric chemistry impacts. PMID:24733927

Caulton, Dana R; Shepson, Paul B; Santoro, Renee L; Sparks, Jed P; Howarth, Robert W; Ingraffea, Anthony R; Cambaliza, Maria O L; Sweeney, Colm; Karion, Anna; Davis, Kenneth J; Stirm, Brian H; Montzka, Stephen A; Miller, Ben R

2014-04-29

341

Methane-Cycling Microbial Communities and Methane Emission in Natural and Restored Peatlands  

PubMed Central

We addressed how restoration of forestry-drained peatlands affects CH4-cycling microbes. Despite similar community compositions, the abundance of methanogens and methanotrophs was lower in restored than in natural sites and correlated with CH4 emission. Poor establishment of methanogens may thus explain low CH4 emissions on restored peatlands even 10 to 12 years after restoration.

Hynninen, Anu; Nieminen, Mika; Tuomivirta, Tero T.; Tuittila, Eeva-Stiina; Nousiainen, Hannu; Kell, Dana K.; Yrjala, Kim; Tervahauta, Arja; Fritze, Hannu

2012-01-01

342

One year of continuous measurements constraining methane emissions from the Baltic Sea to the atmosphere using a ship of opportunity  

NASA Astrophysics Data System (ADS)

Methane and carbon dioxide were measured with an autonomous and continuous running system on a ferry line crossing the Baltic Sea on a 2-3 day interval from the Mecklenburg Bight to the Gulf of Finland in 2010. Surface methane saturations show great seasonal differences in shallow regions like the Mecklenburg Bight (103-507%) compared to deeper regions like the Gotland Basin (96-161%). The influence of controlling parameters like temperature, wind, mixing depth and processes like upwelling, mixing of the water column and sedimentary methane emissions on methane oversaturation and emission to the atmosphere are investigated. Upwelling was found to influence methane surface concentrations in the area of Gotland significantly during the summer period. In February 2010, an event of elevated methane concentrations in the surface water and water column of the Arkona Basin was observed, which could be linked to a wind-derived water level change as a potential triggering mechanism. The Baltic Sea is a source of methane to the atmosphere throughout the year, with highest fluxes during the winter season. Stratification was found to intensify the formation of a methane reservoir in deeper regions like Gulf of Finland or Bornholm Basin, which leads to long lasting elevated methane concentrations and enhanced methane fluxes, when mixed to the surface during mixed layer deepening in autumn and winter. Methane concentrations and fluxes from shallow regions like the Mecklenburg Bight are rather controlled by sedimentary production and consumption of methane, wind events and the change in temperature-dependent solubility of methane in the surface water. Methane fluxes vary significantly in shallow regions (e.g. Mecklenburg Bight) and regions with a temporal stratification (e.g. Bornholm Basin, Gulf of Finland). On the contrary, areas with a permanent stratification like the Gotland Basin show only small seasonal fluctuations in methane fluxes.

Gülzow, W.; Rehder, G.; Deimling, J. Schneider v.; Seifert, T.; Tóth, Zs.

2012-08-01

343

One year of continuous measurements constraining methane emissions from the Baltic Sea to the atmosphere using a ship of opportunity  

NASA Astrophysics Data System (ADS)

Methane and carbon dioxide were measured with an autonomous and continuous running system on a ferry line crossing the Baltic Sea on a 2-3 day interval from the Mecklenburg Bight to the Gulf of Finland in 2010. Surface methane saturations show great seasonal differences in shallow regions like the Mecklenburg Bight (103-507%) compared to deeper regions like the Gotland Basin (96-161%). The influence of controlling parameters like temperature, wind, mixing depth and processes like upwelling, mixing of the water column and sedimentary methane emissions on methane oversaturation and emission to the atmosphere are investigated. Upwelling was found to influence methane surface concentrations in the area of Gotland significantly during the summer period. In February 2010, an event of elevated methane concentrations in the surface water and water column of the Arkona Basin was observed, which could be linked to a wind-derived water level change as a potential triggering mechanism. The Baltic Sea is a source of methane to the atmosphere throughout the year, with highest fluxes occurring during the winter season. Stratification was found to promote the formation of a methane reservoir in deeper regions like Gulf of Finland or Bornholm Basin, which leads to long lasting elevated methane concentrations and enhanced methane fluxes, when mixed to the surface during mixed layer deepening in autumn and winter. Methane concentrations and fluxes from shallow regions like the Mecklenburg Bight are predominantly controlled by sedimentary production and consumption of methane, wind events and the change in temperature-dependent solubility of methane in the surface water. Methane fluxes vary significantly in shallow regions (e.g. Mecklenburg Bight) and regions with a temporal stratification (e.g. Bornholm Basin, Gulf of Finland). On the contrary, areas with a permanent stratification like the Gotland Basin show only small seasonal fluctuations in methane fluxes.

Gülzow, W.; Rehder, G.; Deimling, J. Schneider v.; Seifert, T.; Tóth, Z.

2013-01-01

344

LANDFILL OPERATION FOR CARBON SEQUESTRATION AND MAXIMUM METHANE EMISSION CONTROL  

SciTech Connect

The work described in this report, to demonstrate and advance this technology, has used two demonstration-scale cells of size (8000 metric tons [tonnes]), sufficient to replicate many heat and compaction characteristics of larger ''full-scale'' landfills. An enhanced demonstration cell has received moisture supplementation to field capacity. This is the maximum moisture waste can hold while still limiting liquid drainage rate to minimal and safely manageable levels. The enhanced landfill module was compared to a parallel control landfill module receiving no moisture additions. Gas recovery has continued for a period of over 4 years. It is quite encouraging that the enhanced cell methane recovery has been close to 10-fold that experienced with conventional landfills. This is the highest methane recovery rate per unit waste, and thus progress toward stabilization, documented anywhere for such a large waste mass. This high recovery rate is attributed to moisture, and elevated temperature attained inexpensively during startup. Economic analyses performed under Phase I of this NETL contract indicate ''greenhouse cost effectiveness'' to be excellent. Other benefits include substantial waste volume loss (over 30%) which translates to extended landfill life. Other environmental benefits include rapidly improved quality and stabilization (lowered pollutant levels) in liquid leachate which drains from the waste.

Don Augenstein

2001-02-01

345

NEW ESTIMATE OF METHANE EMISSIONS FROM THE HUDSON BAY LOWLANDS USING AIRCRAFT OBSERVATIONS FROM THE ARCTAS AND PRE-HIPPO AIRBORNE CAMPAIGNS  

NASA Astrophysics Data System (ADS)

Boreal wetlands are a large natural source of global atmospheric methane. We use measurements from the ARCTAS and pre-HIPPO aircraft campaigns over Canada in April-July 2008, interpreted with the GEOS-Chem chemical transport model, to better constrain emissions from the Hudson Bay Lowlands (HBL). Data from ARCTAS in July show ~100 ppbv methane enhancements in the boundary layer over the HBL below 2 km. This is consistent with the wetlands emission scheme used in GEOS-Chem and implies a regional wetland emission estimate of 3 - 5 Tg C yr-1, significantly higher than previous estimates (1 - 2 Tg C yr-1). The pre-HIPPO data (May-June) show no significant methane enhancements over the HBL, consistent with the model. Together the airborne datasets suggest an onset of methane emissions in the beginning of July. To further investigate this seasonal onset in wetland emissions, we compare model seasonal trends to 2005-2007 observations at two Canadian surface sites: Fraserdale (neighboring the HBL) and Alert (background High Arctic). The model is consistent with the observed seasonal cycle at Alert, exhibiting a seasonal minimum between mid-July and mid-August due to chemical loss. . At Fraserdale, by contrast, the model shows a seasonal rise from HBL wetland emissions starting in April; in the observations this seasonal rise is delayed until early June. We discuss these apparently conflicting results in the seasonal transition of wetland emissions. Model seasonality in wetland emissions is primarily driven by surface temperature. However, other mechanisms instead need to be brought into play such as seasonal dynamics of the surrounding permafrost, soil temperature and water table.

Pickett-Heaps, C.; Jacob, D. J.; Wecht, K.; Drevet, J.; Diskin, G. S.; Wofsy, S.; Worthy, D.; Kort, E. A.; Jimenez, R.; Daube, B.; Park, S.

2009-12-01

346

Modeling of catalytic coupling of methane  

Microsoft Academic Search

Catalytic oxidative coupling to ethane or ethylene is an appealing, direct route to utilization of otherwise low value natural gas located in remote sites. Researchers have focused on oxidative coupling of methane for about 15 years, using metal oxide catalysts to facilitate the reaction. Despite intensive efforts, the best yields to C2 hydrocarbons have been in the 20 to 30%

L. M. Hair; W. J. Pitz; M. W. Droege; C. K. Westbrook

1991-01-01

347

Impact of coal output concentration on methane emission to longwall faces / Wp?yw koncentracji wydobycia na wydzielanie metanu do wyrobisk ?cianowych  

NASA Astrophysics Data System (ADS)

An increase in concentration of coal output in Polish hard coal mines contributes to a significant increase in absolute methane-bearing capacity in mining areas. Measurements of methane concentration were taken in selected longwall faces in order to estimate the influence of coal output on methane hazard. The measurements were taken from 2006 to 2008 in 8 longwalls in mines with high methane hazard. The parameters for longwalls where measurements were taken are presented in table 1. Average daily output ranged from 1380 to 2320 Mg: however the maximum daily output amounted to 5335 Mg. Absolute methane-bearing capacity ranged from 4.44 to 56.41 m3/min. Longwalls were ventilated with a U and Y system and their ventilation schemes are presented in figure 1. The period of measurements ranged from 29 to 384 days. The results obtained were used to determine the influence of changes in output on methane hazard. For each longwall under research statistical estimation of parameters, such as: ventilation air methane (VAM) emission, amount of methane captured by a drainage system, absolute methane-bearing capacity and an advance of longwall face was conducted. In order to determine the influence of a longwall face advance on methane-bearing capacity the probabilistic model of the distribution of those parameters on the basis of the measurement results was used. In order to determine the dependence between ventilation air methane emission, methane drainage, absolute methane-bearing capacity and longwall advance, the distribution of analysed variables was checked by means of Kolmogorow-Smirnov normality test. The results of this test are presented in table 2. Table 3 presents values for correlation co-efficient r(x,y). When analyzing the results presented in table 3 it must be observed that in case of most longwalls there is a high correlation between ventilation air methane emission, absolute methane-bearing capacity and longwall advance. However, in longwalls N-10 i W-5 the correlation between methane drainage capture and longwall advance is equally strong. In all other longwalls the correlation is average. In all cases the correlations were positive, which means that together with an increase in advance, there is also an increase in ventilation air methane emission, methane drainage capture and absolute methane-bearing capacity On the basis of determination co-efficient it can be concluded that in cases under consideration at least half (about 50%) of results, ventilation air methane emission, methane drainage capture and absolute methane-bearing capacity can be explained linearly by an influence of longwall advance, while this statement can be assumed with the probability close to 100%. It should also be added that the lack of very high or full correlations means that examined parameters do not fully show linear dependence; however there might be other functional correlations. Because of a complex character of phenomena happening during mining it is not possible to determine full correlations. However, the interpretation of results allows us to claim that an influence of wall advance on methane emission amounts to 30 to 70% depending on a given case. Therefore, other factors, for example geological ones, which were not taken into consideration, will contribute to the level of methane hazard. Table 4 presents determined co-efficients of linear regression. On the basis of the data in table 4, an equation describing the dependence of absolute methane-bearing capacity in a longwall on a longwall advance in the form (11) can be formed. Table 5 presents determined co-efficients of non-linear regression. On the basis of the data in table 5, an equation describing the dependence of absolute methane-bearing capacity in a longwall on a longwall advance in the form (13) can be formed. When comparing co-efficient R2 of the contribution of the explained variance in tables 4 and 5 it can be obcserved that non-linear dependence explains better the results of mining measurements. The similar dependence presenting methane emission as dependent on

Szl?zak, Nikodem; Kubaczka, Czes?aw

2012-10-01

348

A global model of natural volatile organic compound emissions  

Microsoft Academic Search

Numerical assessments of global air quality and potential changes in atmospheric chemical constituents require estimates of the surface fluxes of a variety of trace gas species. We have developed a global model to estimate emissions of volatile organic compounds from natural sources (NVOC). Methane is not considered here and has been reviewed in detail elsewhere. The model has a highly

Alex Guenther; C. Nicholas Hewitt; David Erickson; Ray Fall; Chris Geron; Tom Graedel; Peter Harley; Lee Klinger; Manuel Lerdau; W. A. McKay; Tom Pierce; Bob Scholes; Rainer Steinbrecher; Raja Tallamraju; John Taylor; Pat Zimmerman

1995-01-01

349

A Geochemical Model for the Origin of Methane on Titan  

NASA Astrophysics Data System (ADS)

The existence of methane in Titan's atmosphere has been a mystery for years [1]. The short photochemical lifetime of methane in the atmosphere suggests that methane is replenished from the interior. Observations by Cassini-Huygens have offered new insights into the origin of methane on Titan. These data have confirmed that Titan's methane is endogenic [2], consistent with geophysical models [3]. Today, an issue is the origin of methane on Titan in general. Why does Titan have methane in the first place? Here, we show that methane formation would have been unavoidable on early Titan. It is likely that Titan accreted materials similar to carbonaceous chondrites and comets, except for extreme volatiles in comets, such as carbon monoxide. Thus, we assume that Titan started with Fe-Ni metals and sulfides, silicates and oxides of the rock-forming elements, organic matter, carbon dioxide, methanol, and ammonia. After accretion, radiogenic heat would have melted ice, facilitating water-rock separation and interaction. Mineral dissolution and precipitation, along with acid-base reactions, would have been facile throughout differentiation, despite the low temperature. In contrast, most redox reactions, notably organic matter decomposition, would have been slow in cold aqueous solution. Eventually, the interior would have segregated into a muddy core, covered by a high-pressure ice layer, overlain by a salty ocean, capped by an ice shell [3]. The primordial muddy core would have been composed of phyllosilicates, organic matter, carbonates, sulfides, and presumably, metals. The early salty ocean would have been rich in sodium chloride and bicarbonate, in addition to methanol and ammonium salts. Methane would not have formed in hydrothermal systems at the ocean floor because the high-pressure ice layer would have inhibited hydrothermal circulation. Instead, we propose that methane is a byproduct of the thermal evolution of the core. Specifically, our core devolatilization hypothesis states that high temperatures driven by radioactive decay [4] changed the chemistry of the core via metamorphism. Preliminary calculations indicate that hydrous minerals recrystallize into anhydrous minerals by releasing water, which oxidizes Fe metal, producing dihydrogen (i.e., reducing conditions). In response, organic matter in the core is broken down into carbon-bearing solids, liquids, and gases, including methane. In time, methane can migrate into the ocean, where it can be trapped in clathrate hydrates and subsequently released into the atmosphere [3]. References: [1] Owen T.C. (2000) P&SS 48, 747-752. [2] Niemann H.B. et al. (2005) Nature 438, 779-784. [3] Tobie G. et al. (2006) Nature 440, 61-64. [4] Grasset O. et al. (2000) P&SS 48, 617-636.

Glein, C. R.; Shock, E. L.

2007-12-01

350

LOX/Methane Main Engine Igniter Tests and Modeling  

NASA Technical Reports Server (NTRS)

The LOX/methane propellant combination is being considered for the Lunar Surface Access Module ascent main engine propulsion system. The proposed switch from the hypergolic propellants used in the Apollo lunar ascent engine to LOX/methane propellants requires the development of igniters capable of highly reliable performance in a lunar surface environment. An ignition test program was conducted that used an in-house designed LOX/methane spark torch igniter. The testing occurred in Cell 21 of the Research Combustion Laboratory to utilize its altitude capability to simulate a space vacuum environment. Approximately 750 ignition test were performed to evaluate the effects of methane purity, igniter body temperature, spark energy level and frequency, mixture ratio, flowrate, and igniter geometry on the ability to obtain successful ignitions. Ignitions were obtained down to an igniter body temperature of approximately 260 R with a 10 torr back-pressure. The data obtained is also being used to anchor a CFD based igniter model.

Breisacher, Kevin J.; Ajmani, Kumund

2008-01-01

351

Atmospheric controls on methane emissions from a subarctic bog in northern Quebec, Canada, using an open-path eddy covariance system  

NASA Astrophysics Data System (ADS)

Wetlands are the largest natural source of atmospheric methane, a powerful greenhouse gas. Over such environments, methane fluxes are traditionally quantified with static or dynamic chambers and gas chromatography. Although inexpensive and portable, this method does not allow for continuous measurements besides not capturing the effect of atmospheric turbulence on methane emissions. An alternative is closed-path eddy covariance systems, but these usually require high power consumption and regular maintenance, both of which are difficult to supply in hi