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EPA Science Inventory

EPA, in conjunction with ONSI Corp., embarked on a project to define, design, test, and assess a fuel cell energy recovery system for application at anaerobic digester waste water (sewage) treatment plants. Anaerobic digester gas (ADG) is produced at these plants during the proce...


Arnold Schwarzenegger ANAEROBIC DIGESTER  

E-print Network

Arnold Schwarzenegger Governor ANAEROBIC DIGESTER IMPLEMENTATION ISSUES Phase II - A Survey who took concrete steps to install an anaerobic digestion (AD) facility and documentation motivated by being able to reduce odor and use the digested solids as animal bedding. Neither


Economic viability of anaerobic digestion  

SciTech Connect

The industrial application of anaerobic digestion is a relatively new, yet proven waste treatment technology. Anaerobic digestion reduces and upgrades organic waste, and is a good way to control air pollution as it reduces methane and nitrous gas emissions. For environmental and energy considerations, anaerobic digestion is a nearly perfect waste treatment process. However, its economic viability is still in question. A number of parameters - type of waste (solid or liquid), digester system, facility size, product quality and end use, environmental requirements, cost of alternative treatments (including labor), and interest rates - define the investment and operating costs of an anaerobic digestion facility. Therefore, identical facilities that treat the same amount and type of waste may, depending on location, legislation, and end product characteristics, reveal radically different costs. A good approach for evaluating the economics of anaerobic digestion is to compare it to treatment techniques such as aeration or conventional sewage treatment (for industrial wastewater), or composting and incineration (for solid organic waste). For example, the cost (per ton of waste) of in-vessel composting with biofilters is somewhat higher than that of anaerobic digestion, but the investment costs 1 1/2 to 2 times more than either composting or anaerobic digestion. Two distinct advantages of anaerobic digestion are: (1) it requires less land than either composting or incinerating, which translates into lower costs and milder environmental and community impacts (especially in densely populated areas); and (2) it produces net energy, which can be used to operate the facility or sold to nearby industries.

Wellinger, A. [INFOENERGIE, Ettenhausen (Switzerland)



Arnold Schwarzenegger ANAEROBIC DIGESTER  

E-print Network

Arnold Schwarzenegger Governor ANAEROBIC DIGESTER IMPLEMENTATION ISSUES Phase I - A Survey of U concrete steps to install an anaerobic digestion (AD) facility and documentation of the factors to reduce odor and use the digested solids as animal bedding. Neither of these factors was a motivator


An evaluation of the social and private efficiency of adoption: Anaerobic digesters and greenhouse gas mitigation.  


Climate science has begun to recognize the important role of non-carbon dioxide greenhouse gas emissions, including methane. Given the important contribution of methane, anaerobic digesters (ADs) on dairy farms in the U.S. present an opportunity to reduce greenhouse gas (GHG) emissions. We quantify the social and private costs and benefits of ADs that have been adopted in California and find that, despite high initial costs, large reductions in GHG emissions bring significant social benefits and represent good social investments given a $36 per-ton social cost of carbon. Subsidies that lower the initial private investment cost can help align socially and privately optimal adoption decisions. PMID:25706409

Manning, D T; Hadrich, J C



Nitrogen availability and indirect measurements of greenhouse gas emissions from aerobic and anaerobic biowaste digestates applied to agricultural soils.  


Recycling biowaste digestates on agricultural land diverts biodegradable waste from landfill disposal and represents a sustainable source of nutrients and organic matter (OM) to improve soil for crop production. However, the dynamics of nitrogen (N) release from these organic N sources must be determined to optimise their fertiliser value and management. This laboratory incubation experiment examined the effects of digestate type (aerobic and anaerobic), waste type (industrial, agricultural and municipal solid waste or sewage sludge) and soil type (sandy loam, sandy silt loam and silty clay) on N availability in digestate-amended soils and also quantified the extent and significance of the immobilisation of N within the soil microbial biomass, as a possible regulatory mechanism of N release. The digestate types examined included: dewatered, anaerobically digested biosolids (DMAD); dewatered, anaerobic mesophilic digestate from the organic fraction of municipal solid waste (DMADMSW); liquid, anaerobic co-digestate of food and animal slurry (LcoMAD) and liquid, thermophilic aerobic digestate of food waste (LTAD). Ammonium chloride (NH4Cl) was included as a reference treatment for mineral N. After 48 days, the final, maximum net recoveries of mineral N relative to the total N (TN) addition in the different digestates and unamended control treatments were in the decreasing order: LcoMAD, 68%; LTAD, 37%, DMAD, 20%; and DMADMSW, 11%. A transient increase in microbial biomass N (MBN) was observed with LTAD application, indicating greater microbial activity in amended soil and reflecting the lower stability of this OM source, compared to the other, anaerobic digestate types, which showed no consistent effects on MBN compared to the control. Thus, the overall net release of digestate N in different soil types was not regulated by N transfer into the soil microbial biomass, but was determined primarily by digestate properties and the capacity of the soil type to process and turnover digestate N. In contrast to the sandy soil types, where nitrate (NO3-) concentrations increased during incubation, there was an absence of NO3- accumulation in the silty clay soil amended with LTAD and DMADMSW. This provided indirect evidence for denitrification activity and the gaseous loss of N, and the associated increased risk of greenhouse gas emissions under certain conditions of labile C supply and/or digestate physical structure in fine-textured soil types. The significance and influence of the interaction between soil type and digestate stability and physical properties on denitrification processes in digestate-amended soils require urgent investigation to ensure management practices are appropriate to minimise greenhouse gas emissions from land applied biowastes. PMID:24035244

Rigby, H; Smith, S R




EPA Science Inventory

The paper summarizes the results of a 2-year field test to assess the performance of a specially modified commercial phosphoric acid 200 kW fuel cell power plant to recover energy from anaerobic digester gas (ADG) which has been cleansed of contaminants (sulfur and halide compoun...


Meta-analysis of greenhouse gas emissions from anaerobic digestion processes in dairy farms.  


This meta-analysis quantifies the changes in greenhouse gas (GHG) emissions from dairy farms, caused by anaerobically digesting (AD) cattle manure. As this is a novel quantifiable synthesis of the literature, a database of GHG emissions from dairy farms is created. Each case in the database consists of a baseline (reference with no AD system) and an AD scenario. To enable interstudy comparison, emissions are normalized by calculating relative changes (RCs). The distributions of RCs are reported by specific GHGs and operation units. Nonparametric tests are applied to the RCs in order to identify a statistical difference of AD with respect to baseline scenarios (Wilcoxon rank test), correlations (Spearman test), and best estimation for changes in emissions (Kernel density distribution estimator). From 749 studies identified, 30 papers yield 89 independent cases. The median reductions in emissions from the baseline scenarios, according to operation units, are -43.2% (n.s.) for storage, -6.3% for field application of slurries, -11.0% for offset of energy from fossil fuel, and +0.4% (n.s.) for offset of inorganic fertilizers. The leaks from digesters are found to significantly increase the emissions from baseline scenarios (median = +1.4%). PMID:25790272

Miranda, Nicole D; Tuomisto, Hanna L; McCulloch, Malcolm D



Anaerobic digestion of cellulosic wastes  

SciTech Connect

Anaerobic digestion is a potentially attractive technology for volume reduction of cellulosic wastes. A substantial fraction of the waste is converted to off-gas and a relatively small volume of biologically stabilized sludge is produced. Process development work is underway using a 75-L digester to verify rates and conversions obtained at the bench scale, to develop start-up and operating procedures, and to generate effluent for characterization and disposal studies. Three runs using batch and batch-fed conditions have been made lasting 36, 90, and over 200 days. Solids solubilization and gas production rates and total solids destruction have met or exceeded the target values of 0.6 g cellulose per L of reactor per day, 0.5 L off-gas per L of reactor per day, and 80% destruction of solids, respectively. Successful start-up procedures have been developed, and preliminary effluent characterization and disposal studies have been done. A simple dynamic process model has been constructed to aid in further process development and for use in process monitoring and control of a large-scale digester. 7 references, 5 figures, 1 table.

Donaldson, T.L.; Lee, D.D.



Anaerobic digestion of agricultural and other substrates--implications for greenhouse gas emissions.  


The greenhouse gas (GHG) emissions, expressed in carbon dioxide equivalents (CO2-eq), of different Austrian biogas systems were analyzed and evaluated using life-cycle assessment (LCA) as part of a national project. Six commercial biogas plants were investigated and the analysis included the complete process chain: viz., the production and collection of substrates, the fermentation of the substrates in the biogas plant, the upgrading of biogas to biomethane (if applicable) and the use of the biogas or biomethane for heat and electricity or as transportation fuel. Furthermore, the LCA included the GHG emissions of construction, operation and dismantling of the major components involved in the process chain, as well as the use of by-products (e.g. fermentation residues used as fertilizers). All of the biogas systems reduced GHG emissions (in CO2-eq) compared with fossil reference systems. The potential for GHG reduction of the individual biogas systems varied between 60% and 100%. Type of feedstock and its reference use, agricultural practices, coverage of storage tanks for fermentation residues, methane leakage at the combined heat and power plant unit and the proportion of energy used as heat were identified as key factors influencing the GHG emissions of anaerobic digestion processes. PMID:23739470

Pucker, J; Jungmeier, G; Siegl, S; Pötsch, E M



Anaerobic Digestion of Primary Sewage Effluent  

E-print Network

Anaerobic Digestion of Primary Sewage Effluent: Significant Energy Savings over Traditional Activated Sludge Treatment This report presents results for an anaerobic digestion system operated;Anaerobic Digestion of Primary Sewage Effluent Prepared for the U.S. Department of Energy Office


Module 12: Biogas/Anaerobic Digesters  

NSDL National Science Digital Library

Eastern Iowa Community College provides this learning module to teach students anaerobic digester basics, the benefits of anaerobic digesters, the anaerobic digester process, and a variety of related topics. Users can download a zip file in which they will find a syllabus, student handouts, a quiz, and 55 slide PowerPoint presentation.


The Anaerobic Digestion of Organic  

E-print Network

occurs naturally in landfills that contain organic waste, such as food scraps, paper products, and yardThe Anaerobic Digestion of Organic Municipal Solid Waste in California, these energy alternatives could provide a number of benefits, including reducing the United States' dependence

Iglesia, Enrique


Integration of on-farm biodiesel production with anaerobic digestion to maximise energy yield and greenhouse gas savings from process and farm residues.  


Anaerobic co-digestion of residues from the cold pressing and trans-esterification of oilseed rape (OSR) with other farm wastes was considered as a means of enhancing the sustainability of on-farm biodiesel production. The study verified the process energy yields using biochemical methane potential (BMP) tests and semi-continuous digestion trials. The results indicated that high proportions of OSR cake in the feedstock led to a decrease in volatile solids destruction and instability of the digestion process. Co-digestion with cattle slurry or with vegetable waste led to acceptable specific and volumetric methane productions, and a digestate low in potentially toxic elements (PTE). The results were used to evaluate energy balances and greenhouse gas emissions of the integrated process compared with biodiesel production alone. Co-digestion was shown to provide energy self-sufficiency and security of supply to farms, with sufficient surplus for export as fuel and electricity. PMID:21719281

Heaven, Sonia; Salter, Andrew M; Banks, Charles J



Kinetic modeling and experimentation of anaerobic digestion  

E-print Network

Anaerobic digesters convert organic waste (agricultural and food waste, animal or human manure, and other organic waste), into energy (in the form of biogas or electricity). An added benefit to bio-digestion is a leftover ...

Rea, Jonathan (Jonathan E.)




EPA Science Inventory

The report discusses Phase I (a conceptual design, preliminary cost, and evaluation study) of a program to demonstrate the recovery of energy from waste methane produced by anaerobic digestion of waste water treatment sludge. The fuel cell is being used for this application becau...


Technical assessment of fuel cell operation on anaerobic digester gas at the Yonkers, NY, wastewater treatment plant.  


This paper summarizes the results of a 2-year field test to assess the performance of a specially modified commercial phosphoric acid 200-kW fuel cell power plant to recover energy from anaerobic digester gas (ADG) which has been cleansed of contaminants (sulfur and halide compounds) using a patented gas pretreatment unit (GPU). Specific project goals include characterization of the fuel cell power plant emissions and verification of the GPU performance for removing sulfur contaminants. To remove halide contaminants from the ADG, a halide guard, consisting of a vessel with a metal oxide supported on alumina, was incorporated into the fuel cell reactant supply. This first-of-a-kind demonstration was conducted at the Yonkers, NY, wastewater treatment plant, a sewage processing facility owned and operated by Westchester County. Results have demonstrated that the ADG fuel cell power plant can produce electrical output levels close to full power (200 kW) with negligible air emissions of CO, NO(x), and SO(2). The GPU removed virtually 100% of H(2)S and 88% of organic sulfur, bringing the overall sulfur removal efficiency of the GPU to over 99%. The halide guard removed up to 96% of the halides exiting the GPU. PMID:14522189

Spiegel, R J; Preston, J L



Anaerobic digestion of brewery byproducts  

Microsoft Academic Search

Energy recovery in the brewery industry by mesophilic anaerobic digesion of process by-products is technically feasible. The maximum achievable loading rate is 6g dry substrate\\/L-day. CH4 gas production declines as the loading rate increases in the range 2-6 g\\/L day. CH4 production increases in the range 8-15 days; optimal design criteria are a 10-day detention time with a loading rate

J. D. Keenan; I. Kormi



Anaerobic digestion of brewery byproducts  

SciTech Connect

Energy recovery in the brewery industry by mesophilic anaerobic digesion of process by-products is technically feasible. The maximum achievable loading rate is 6g dry substrate/L-day. CH4 gas production declines as the loading rate increases in the range 2-6 g/L day. CH4 production increases in the range 8-15 days; optimal design criteria are a 10-day detention time with a loading rate of 6 g dry substrate/L day.

Keenan, J.D.; Kormi, I.



Batch load anaerobic digestion of dairy manure  

E-print Network

digestion of animal manure serves two general functions, (1) partial treatment and stabilization of the waste material, and (2) energy recovery from the biomass. Although anaerobic digestion has been studied for many years, the process has not been...BATCH LOAD ANAEROBIC DIGESTION OF DAIRY MANURE A Thesis RICHARD PAUL EGG Submitted to the Graduate College of Texas ARM University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE May 1979 Major Subject...

Egg, Richard P



Anaerobic Digestion. Student Manual. Biological Treatment Process Control.  

ERIC Educational Resources Information Center

This student manual contains the textual material for a four-lesson unit on anaerobic digestion control. Areas addressed include: (1) anaerobic sludge digestion (considering the nature of raw sludge, purposes of anaerobic digestion, the results of digestion, types of equipment, and other topics); (2) digester process control (considering feeding…

Carnegie, John W., Ed.



Technology Transfer Automated Retrieval System (TEKTRAN)

Methane gas resulting from combining cotton gin trash and dairy manure in a two phase anaerobic digester is easily marketed. Digestate solids are not. This study was conducted to determine anaerobic digestate toxicity and its potential as a soil amendment. The same mixture of dairy manure and cot...


Waste-to-wheel analysis of anaerobic-digestion-based renewable natural gas pathways with the GREET model.  

SciTech Connect

In 2009, manure management accounted for 2,356 Gg or 107 billion standard cubic ft of methane (CH{sub 4}) emissions in the United States, equivalent to 0.5% of U.S. natural gas (NG) consumption. Owing to the high global warming potential of methane, capturing and utilizing this methane source could reduce greenhouse gas (GHG) emissions. The extent of that reduction depends on several factors - most notably, how much of this manure-based methane can be captured, how much GHG is produced in the course of converting it to vehicular fuel, and how much GHG was produced by the fossil fuel it might displace. A life-cycle analysis was conducted to quantify these factors and, in so doing, assess the impact of converting methane from animal manure into renewable NG (RNG) and utilizing the gas in vehicles. Several manure-based RNG pathways were characterized in the GREET (Greenhouse gases, Regulated Emissions, and Energy use in Transportation) model, and their fuel-cycle energy use and GHG emissions were compared to petroleum-based pathways as well as to conventional fossil NG pathways. Results show that despite increased total energy use, both fossil fuel use and GHG emissions decline for most RNG pathways as compared with fossil NG and petroleum. However, GHG emissions for RNG pathways are highly dependent on the specifics of the reference case, as well as on the process energy emissions and methane conversion factors assumed for the RNG pathways. The most critical factors are the share of flared controllable CH{sub 4} and the quantity of CH{sub 4} lost during NG extraction in the reference case, the magnitude of N{sub 2}O lost in the anaerobic digestion (AD) process and in AD residue, and the amount of carbon sequestered in AD residue. In many cases, data for these parameters are limited and uncertain. Therefore, more research is needed to gain a better understanding of the range and magnitude of environmental benefits from converting animal manure to RNG via AD.

Han, J.; Mintz, M.; Wang, M. (Energy Systems)



The anaerobic digestion of rice straw: A review  

Microsoft Academic Search

The anaerobic digestion of rice straw has been studied for the past century, but the renewable energy potential is barely utilized. Greenhouse gas emissions from rice fields can be substantially reduced if straw is removed. Methane yields ranging from 92 to 404 litres per kilogram of volatile solids have been achieved. Optimal digestion conditions such as pH (6.5 to 8.0),

Wendy Mussoline; Giovanni Esposito; Andrea Giordano; Piet Lens



Net greenhouse gas emissions from manure management using anaerobic digestion technology in a beef cattle feedlot in Brazil.  


As part of an agreement during the COP15, the Brazilian government is fostering several activities intended to mitigate greenhouse gas (GHG) emissions. One of them is the adoption of anaerobic digester (AD) for treating animal manure. Due to a lack of information, we developed a case study in order to evaluate the effect of such initiative for beef cattle feedlots. We considered the net GHG emissions (CH4 and N2O) from the manure generated from 140 beef heifers confined for 90 days in the scope "housing to field application" by including field measurements, literature values, and the offset generated by the AD system through the replacement of conventional sources of nitrogen (N) fertilizer and electricity, respectively. Results showed that direct GHG emissions accounted for 0.14 ± 0.06 kg of carbon dioxide equivalent (CO?eq) per kg of animal live weight gain (lwg), with ~80% originating from field application, suggesting that this emission does not differ from the conventional manure management (without AD) typically done in Brazil (0.19 ± 0.07 kg of CO?eq per kg lwg(-1)). However, 2.4 MWh and 658.0 kg of N-manure were estimated to be generated as a consequence of the AD utilization, potentially offsetting 0.13 ± 0.01 kg of CO?eq kg lwg(-1) or 95% (±45%) of total direct emissions from the manure management. Although, by replacing fossil fuel sources, i.e. diesel oil, this offset could be increased to 169% (±47%). In summary, the AD has the potential to significantly mitigate GHG emissions from manure management in beef cattle feedlots, but the effect is indirect and highly dependent on the source to be replaced. In spite of the promising results, more and continuous field measurements for decreasing uncertainties and improving assumptions are required. Identifying shortcomings would be useful not only for the effectiveness of the Brazilian government, but also for worldwide plans in mitigating GHG emissions from beef production systems. PMID:25461102

Costa Junior, Ciniro; Cerri, Carlos E P; Pires, Alexandre V; Cerri, Carlos C



Thermophilic anaerobic digestion of high strength wastewaters  

SciTech Connect

Investigations on the thermophilic anaerobic treatment of high-strength wastewaters (14-65 kg COD/mT) are presented. Vinasse, the wastewater of alcohol distilleries, was used as an example of such wastewaters. Semicontinuously fed digestion experiments at high retention times revealed that the effluent quality of digestion at 55C is comparable with that at 30C at similar loading rates. The amount of methane formed per kilogram of vinasse drops almost linearly with increasing vinasse concentrations. The treatment of vinasse was also investigated using upflow anaerobic sludge blanket (UASB) reactors.

Wiegant, W.M.; Claassen, J.A.; Lettinga, G.



Whole farm impact of anaerobic digestion and biogas use on a New York dairy farm  

Technology Transfer Automated Retrieval System (TEKTRAN)

Anaerobic digestion of manure for biogas production is one of many options for reducing the carbon footprint of milk production. This process reduces greenhouse gas emissions but increases the potential nitrogen and phosphorus losses from the farm. An anaerobic digester component was added to the In...


Pretreatment followed by anaerobic digestion of secondary sludge for reduction of sewage sludge volume.  


The influence of two pretreatment methods, thermal treatment and low-pressure wet oxidation, on the sludge digestion efficiency was examined. Batch thermophilic anaerobic digestion was used to evaluate the effectiveness of the pretreatment methods in terms of volatile suspended solids (VSS) digestion efficiency and gas production. The results showed that the gas production was not proportional to the VSS degradation efficiency of either thermal treatment or low-pressure wet oxidation. Low-pressure wet oxidation treatment at 150 °C along with 40% of the theoretical oxygen required to oxidize organic carbon gave the highest gas production and the VSS digestion efficiency of 77% at a VSS loading rate of 8 g l(-1) d(-1). The digestion efficiency was about 30% higher than that of thermophilic anaerobic digestion without sludge pretreatment. Sewage sludge could be treated effectively at a high VSS digestion efficiency with this pretreatment followed by thermophilic anaerobic digestion. PMID:23752385

Abe, Naoki; Tang, Yue-Qin; Iwamura, Makoto; Morimura, Shigeru; Kida, Kenji



Kinetics of inactivation of indicator pathogens during thermophilic anaerobic digestion  

E-print Network

Kinetics of inactivation of indicator pathogens during thermophilic anaerobic digestion Sudeep C Thermophilic anaerobic digestion Pathogen inactivation Ascaris suum Helminth eggs Poliovirus Enteric viruses a b s t r a c t Thermophilic anaerobic sludge digestion is a promising process to divert waste


Renewable methane from anaerobic digestion of biomass  

Microsoft Academic Search

Production of methane via anaerobic digestion of energy crops and organic wastes would benefit society by providing a clean fuel from renewable feedstocks. This would replace fossil fuel-derived energy and reduce environmental impacts including global warming and acid rain. Although biomass energy is more costly than fossil fuel-derived energy, trends to limit carbon dioxide and other emissions through emission regulations,

David P Chynoweth; John M Owens; Robert Legrand



Anaerobic Digestion in a Flooded Densified Leachbed  

NASA Technical Reports Server (NTRS)

A document discusses the adaptation of a patented biomass-digesting process, denoted sequential batch anaerobic composting (SEBAC), to recycling of wastes aboard a spacecraft. In SEBAC, high-solids-content biomass wastes are converted into methane, carbon dioxide, and compost.

Chynoweth, David P.; Teixeira, Arthur A.; Owens, John M.; Haley, Patrick J.



High solids digestion of municipal solid waste to methane by anaerobic digestion  

Microsoft Academic Search

One relatively simple energy alternative is the production of methane gas by anaerobic digestion. The process has received attention as a method of producing energy in the form of gaseous fuel renewable from lignocellulosic wastes. The US generates approximately 90 million tons of municipal solid waste (MSW) each year. This quantity could generate 900 billion cubic feet of methane per

G. C. Magruder; R. E. Corder; E. C. Clausen; J. L. Gaddy



Photoenhanced anaerobic digestion of organic acids  


A process is described for rapid conversion of organic acids and alcohols anaerobic digesters into hydrogen and carbon dioxide, the optimal precursor substrates for production of methane. The process includes addition of photosynthetic bacteria to the digester and exposure of the bacteria to radiant energy (e.g., solar energy). The process also increases the pH stability of the digester to prevent failure of the digester. Preferred substrates for photosynthetic bacteria are the organic acid and alcohol waste products of fermentative bacteria. In mixed culture with methanogenic bacteria or in defined co-culture with non-aceticlastic methanogenic bacteria, photosynthetic bacteria are capable of facilitating the conversion or organic acids and alcohols into methane with low levels of light energy input.

Weaver, Paul F. (Golden, CO)



Anaerobic digestion of slaughterhouse by-products  

Microsoft Academic Search

Anaerobic digestion of animal by-products was investigated in batch and semi-continuously fed, reactor experiments at 55°C and for some experiments also at 37°C. Separate or mixed by-products from pigs were tested. The methane potential measured by batch assays for meat- and bone flour, fat, blood, hair, meat, ribs, raw waste were: 225, 497, 487, 561, 582, 575, 359, 619dm3kg?1 respectively,

Anette Hejnfelt; Irini Angelidaki



Contribution of Anaerobic Digesters to Emissions Mitigation and Electricity Generation Under U.S. Climate Policy  

E-print Network

Livestock husbandry in the U.S. significantly contributes to many environmental problems, including the release of methane, a potent greenhouse gas (GHG). Anaerobic digesters (ADs) break down organic wastes using bacteria ...

Zaks, David P. M.


A mass transfer model of ammonia volatilisation from anaerobic digestate  

Microsoft Academic Search

Anaerobic digestion (AD) is becoming increasingly popular for treating organic waste. The methane produced can be burned to generate electricity and the digestate, which is high in mineral nitrogen, can be used as a fertiliser. In this paper we evaluate potential losses of ammonia via volatilisation from food waste anaerobic digestate using a closed chamber system equipped with a sulphuric

M. J. Whelan; T. Everitt; R. Villa



Ultrasonic sludge treatment for enhanced anaerobic digestion.  


Ultrasound is the term used to describe sound energy at frequencies above 20 kHz. High-powered ultrasound can be applied to a waste stream via purpose-designed tools in order to induce cavitation. This effect results in the rupture of cellular material and reduction of particle size in the waste stream, making the cells more amenable to downstream processing. sonix is a new technology utilising high-powered, concentrated ultrasound for conditioning sludges prior to further treatment. This paper presents recent results from a number of demonstration and full-scale plants treating thickened waste activated sludge (TWAS) prior to anaerobic digestion, therefore enhancing the process. The present studies have proved that the use of ultrasound to enhance anaerobic digestion can be achieved at full scale and effectively result in the TWAS (typically difficult to digest) behaving, after sonication, as if it were a "primary" sludge. The technology presents benefits in terms of increased biogas production, better solids reduction, improved dewatering characteristics of the digested sludge mixture and relatively short payback periods of two years or less subject to the site conditions and practices applicable at that time. PMID:15580991

Hogan, F; Mormede, S; Clark, P; Crane, M



Anaerobic digestion of extruded OFMSW.  


Organic fraction of municipal solid waste (OFMSW) was used to feed two pilot plants of 1000 l working in anaerobic conditions. The OFMSW had previously been treated using a system of extrusion which, due to exerted pressure, separates the undesired fractions of waste from organic waste and reduces the organic fraction in a kind of homogeneous jam. Pilot tests were performed in semi-continuous conditions with a stepwise progressive increase of the total solids content (TS) of the input material from 3% TS w/w (1.5 g VS l(-1) d(-1) organic loading rate) to 10% TS w/w (4.3 g VS l(-1) d(-1) organic loading rate) using activated sludge as diluting agent. The average specific biogas production obtained was 600 l kg(-1)VS. When the input TS content was increased to 10% w/w, the biogas average specific production went up to 800 l kg(-1)VS. The methane content in the biogas was always higher than 60% measured by volume. PMID:22074901

Novarino, Daniel; Zanetti, Maria Chiara



Balancing hygienization and anaerobic digestion of raw sewage sludge.  


The anaerobic digestion of raw sewage sludge was evaluated in terms of process efficiency and sludge hygienization. Four different scenarios were analyzed, i.e. mesophilic anaerobic digestion, thermophilic anaerobic digestion and mesophilic anaerobic digestion followed by a 60 °C or by an 80 °C hygienization treatment. Digester performance (organic matter removal, process stability and biogas yield) and the hygienization efficiency (reduction of Escherichia coli, somatic coliphages and F-specific RNA phages) were the main examined factors. Moreover, a preliminary economical feasibility study of each option was carried out throughout an energy balance (heat and electricity). The obtained results showed that both thermophilic anaerobic digestion and mesophilic anaerobic digestion followed by a hygienization step were able to produce an effluent sludge that fulfills the American and the European legislation for land application. However, higher removal efficiencies of indicators were obtained when a hygienization post-treatment was present. Regarding the energy balance, it should be noted that all scenarios have a significant energy surplus. Particularly, positive heat balances will be obtained for the thermophilic anaerobic digestion and for the mesophilic anaerobic digestion followed by 60 °C hygienization post-treatment if an additional fresh-sludge/digested sludge heat exchanger is installed for energy recovery. PMID:23063441

Astals, S; Venegas, C; Peces, M; Jofre, J; Lucena, F; Mata-Alvarez, J



Effects of turbulence modelling on prediction of flow characteristics in a bench-scale anaerobic gas-lift digester.  


Flow in a gas-lift digester with a central draft-tube was investigated using computational fluid dynamics (CFD) and different turbulence closure models. The k-? Shear-Stress-Transport (SST), Renormalization-Group (RNG) k-?, Linear Reynolds-Stress-Model (RSM) and Transition-SST models were tested for a gas-lift loop reactor under Newtonian flow conditions validated against published experimental work. The results identify that flow predictions within the reactor (where flow is transitional) are particularly sensitive to the turbulence model implemented; the Transition-SST model was found to be the most robust for capturing mixing behaviour and predicting separation reliably. Therefore, Transition-SST is recommended over k-? models for use in comparable mixing problems. A comparison of results obtained using multiphase Euler-Lagrange and singlephase approaches are presented. The results support the validity of the singlephase modelling assumptions in obtaining reliable predictions of the reactor flow. Solver independence of results was verified by comparing two independent finite-volume solvers (Fluent-13.0sp2 and OpenFOAM-2.0.1). PMID:23624047

Coughtrie, A R; Borman, D J; Sleigh, P A




EPA Science Inventory

The report discusses Phase I (a conceptual design, preliminary cost, and evaluation study) of a program to demonstrate the recovery of energy from waste methane produced by anaerobic digestion of waste water treatment sludge. he fuel cell is being used for this application becaus...


State Of The Science On Cogeneration Of Heat And Power From Anaerobic Digestion Of Municipal Biosolids  

EPA Science Inventory

This presentation will report on work underway to inventory facilities currently utilizing biogas from anaerobic digestion and speak with practitioners to learn: techniques for preparing residuals for digestion, methods to use for cleaning biogas (e.g., of siloxane), and how gas...


Anaerobic Digestion II. Sludge Treatment and Disposal Course #166. Instructor's Guide [and] Student Workbook.  

ERIC Educational Resources Information Center

This lesson is the second of a two-part series on anaerobic digestion. Topics discussed include classification of digester by function, roof design, and temperature range, mixing systems, gas system components, operational control basics, and general safety considerations. The lesson includes an instructor's guide and student workbook. The…

Arasmith, E. E.


Anaerobic digestion of municipal solid waste: Technical developments  

SciTech Connect

The anaerobic biogasification of organic wastes generates two useful products: a medium-Btu fuel gas and a compost-quality organic residue. Although commercial-scale digestion systems are used to treat municipal sewage wastes, the disposal of solid organic wastes, including municipal solid wastes (MSW), requires a more cost-efficient process. Modern biogasification systems employ high-rate, high-solids fermentation methods to improve process efficiency and reduce capital costs. The design criteria and development stages are discussed. These systems are also compared with conventional low-solids fermentation technology.

Rivard, C.J. [National Renewable Energy Lab., Golden, CO (United States)



Anaerobic Digestion of Food Waste-recycling Wastewater  

NASA Astrophysics Data System (ADS)

Food waste-recycling (FWR) wastewater was evaluated as feedstock for two-stage anaerobic digestion at different hydraulic retention times (HRTs). The FWR wastewater tested contained high concentrations of organic materials and had chemical oxygen demand (COD) >130 g/L and volatile solids (VS) >55 g/L. Two identical two-stage anaerobic digesters were operated to investigate the performance at six HRTs ranging from 10-25 days. In the acidogenic reactor, the total carbohydrate reduction efficiency and volatile fatty acid production dramatically decreased when acidogenic HRT was <2.5 days (i.e., total two-stage HRT = 15 days). High organic removal ratios of 75.5-85.9% for COD and 68.8-83.6% for VS were achieved throughout the two-stage process. Methane production rate of 1.7-3.6 L-gas/L-reactor?d was observed. These results suggested that two-stage anaerobic process was successful at the laboratory scale with FWR wastewater as feedstock.

Han, Gyuseong; Shin, Seung Gu; Lim, Juntaek; Jo, Minho; Hwang, Seokhwan



Anaerobic biodegradation of nitroglycerin by digester sludge  

SciTech Connect

Nitroglycerin (NG) is an energetic compound primarily present in gun and rocket propellants as a primary explosive. It was also abundantly found in spent wastes from several chemical or pharmaceutical industries and in the wastewater of munitions manufacturing facilities causing significant environmental pollution. Incineration, other thermal processes, and chemical treatment such as acid or alkaline hydrolysis can effectively destroy these high energy compounds but they are associated with high treatment costs. Moreover, chemical processes may generate waste streams which require further treatment prior to their discharge in the environment. There is therefore, a pressing need for the development of new technologies that can economically and effectively deal with the disposal of energetic compounds. Biological treatment of energetic compounds amenable to microbial degradation provides an alternative to costly thermal and chemical methods. NG can be aerobically biodegraded by several fungal and bacterial consortia in the presence of co-substrates. The decomposition proceeds through a number of intermediate products whose formation is catalyzed by extra-cellular enzymes. The anaerobic biodegradation of NG by a mixed bacterial culture from digester sludge was investigated in this study. the study focused on the ability of anaerobic bacteria to degrade NG and utilize it as sole carbon source, the identification of possible intermediates,and the effect of co-substrates on the rates of transformation.

Christodoulatos, C.; Pal, N.; Bhaumik, S. [Stevens Inst. of Technology, Hoboken, NJ (United States). Center for Environmental Engineering



Parasite ova in anaerobically digested sludge  

SciTech Connect

The Metropolitan Sanitary District of Greater Chicago produces anaerobically digested wastewater sludge from a 14-day continuous-flow process maintained at 35 degrees Celcius. Some of the sludge is ultimately applied to strip-mined lands in Central Illinois (Fulton County) as a soil conditioner and fertilizer. Parasitic nematode ova were isolated from freshly processed samples, as well as from samples collected from storage lagoons, using a system of continuous sucrose solution gradients. The mean number of ova per 100 g of dry sludge was 203 Ascaris spp., 173 Toxocara spp., 48 Toxascaris leonina, and 36 Trichuris spp. An assessment of the viability of these ova was determined by subjecting the ova to conditions favorable for embryonation. Recovered ova were placed in 1.5% formalin and aerated at 22 degrees Celcius for 21 to 28 days. Development of ova isolated from freshly digested sludge occurred in 64% of the Ascaris spp., 53% of the Toxocara, 63% of the Toxascaris leonina, and 20% of the Trichuris spp. Viability was also demonstrated in ova recovered from sludge samples held in storage lagoons for a period of up to 5 years; embryonation occurred in 24% of the Ascaris spp., 10% of the Toxocara spp., 43% of the Toxascaris leonina, and 6% of the Trichuris spp. (Refs. 24).

Arther, R.G.; Fitzgerald, P.R.; Fox, J.C.



Multiple-stage anaerobic digestion system  

SciTech Connect

The purpose of this study is to develop a new process for the stabilization of municipal sludge produced at the Allegheny County Sanitary Authority wastewater treatment plant in Pittsburgh, Pennsylvania. A multiple-stage digestion process is sought to provide good removal efficiency of high concentration of sludge and to perform high methane production. The process primarily consists of three stages of anaerobic digestion. Stage 1 is for hydrolysis and acidification and stage 2 is for acidification and methanation; both digesters are operated in the mesophilic temperature range. The last stage is for methanation which is controlled in the thermophilic range. The multiple-stage system (MS) was operated at different solids retention time (SRT) of 15, 9, and 20 days. For comparison to the performance of the multiple-stage system a conventional single-stage system (SS) was also operated at the same conditions. The COD removal, solids reduction, and the methane yield of the multiple-stage system were much greater than the single-stage system at all of the different SRT. Moreover, the results of the different SRT of the multiple-stage system study showed that a SRT of 15 days has the best performance. The maximum VS removal rates are 67% of MS and 50% of SS; and the methane yields are 6.72 SCF CH/sub 4//lb VS added of MS and 3.95 SCF CH/sub 4//lb VS added of SS with VS loading of 0.15 lb/ft/sup 3/-day at a 15 days SRT. These methane yields are equivalent to 89% and 67% biogas conversion from the removed VS (based on 75% of the sludge VS is biodegradable), respectively, for the multiple-stage and the single-stage systems.

Lin, L.Y.



40 CFR Table Jj-6 to Subpart Jj of... - Collection Efficiencies of Anaerobic Digesters  

Code of Federal Regulations, 2013 CFR

...Efficiencies of Anaerobic Digesters Anaerobic digester type Cover type Methane collection efficiency Covered anaerobic lagoon (biogas capture) Bank to bank, impermeable 0.975 Modular, impermeable 0.70 Complete mix, fixed film, or plug...



40 CFR Table Jj-6 to Subpart Jj of... - Collection Efficiencies of Anaerobic Digesters  

Code of Federal Regulations, 2011 CFR

...Efficiencies of Anaerobic Digesters Anaerobic digester type Cover type Methane collection efficiency Covered anaerobic lagoon (biogas capture) Bank to bank, impermeable 0.975 Modular, impermeable 0.70 Complete mix, fixed film, or plug...



40 CFR Table Jj-6 to Subpart Jj of... - Collection Efficiencies of Anaerobic Digesters  

Code of Federal Regulations, 2014 CFR

...Efficiencies of Anaerobic Digesters Anaerobic digester type Cover type Methane collection efficiency Covered anaerobic lagoon (biogas capture) Bank to bank, impermeable 0.975 Modular, impermeable 0.70 Complete mix, fixed film, or plug...



40 CFR Table Jj-6 to Subpart Jj of... - Collection Efficiencies of Anaerobic Digesters  

Code of Federal Regulations, 2012 CFR

...Efficiencies of Anaerobic Digesters Anaerobic digester type Cover type Methane collection efficiency Covered anaerobic lagoon (biogas capture) Bank to bank, impermeable 0.975 Modular, impermeable 0.70 Complete mix, fixed film, or plug...




EPA Science Inventory

The Water Environment Research Foundation (WERF) recently published a report titled ?Examination of Reactivation and Regrowth of Fecal Coliforms in Anaerobically Digested Sludges?. Seven full-scale publicly owned treatment facilities were sampled several times to determine if bac...


Economic implications of anaerobic digesters on dairy farms in Texas  

E-print Network

Effluent Storage....................................................................... 22 viii TABLE OF CONTENTS (CONTINUED) CHAPTER Page Biogas Handling and Usage ..................................................... 22 Benefits of Anaerobic... Digesters..................................................... 23 Odor Reduction........................................................................ 24 Compost, Bedding, and Fertilizer............................................. 24 Biogas Production...

Jackson, Randy Scott, Jr.



Modeling anaerobic digestion of microalgae using ADM1.  


The coupling between a microalgal pond and an anaerobic digester is a promising alternative for sustainable energy production by transforming carbon dioxide into methane using solar energy. In this paper, we demonstrate the ability of the original ADM1 model and a modified version (based on Contois kinetics for the hydrolysis steps) to represent microalgae anaerobic digestion. Simulations were compared to experimental data of an anaerobic digester fed with Chlorella vulgaris. The modified ADM1 fits adequately the data for the considered 140 day experiment encompassing a variety of influent load and flow rates. It turns out to be a reliable predictive tool for optimising the coupling of microalgae with anaerobic digestion processes. PMID:21536430

Mairet, Francis; Bernard, Olivier; Ras, Monique; Lardon, Laurent; Steyer, Jean-Philippe



Municipal Development of Anaerobic Digestion/ Combined Heat and Power in Massachusetts  

NASA Astrophysics Data System (ADS)

With a commercial food waste ban going into effect in Massachusetts in October 2014, businesses, institutions, and municipalities are considering alternatives to landfills and incinerators for organic waste. Anaerobic digestion is one such alternative. Similar to composting, but in an environment devoid of oxygen, anaerobic digestion produces byproducts such as methane (which can be burned for heat or electricity) and liquid or solid digestate (which can be used as fertilizer, cattle bedding, and more). Thus, disposal of food waste and other organic materials can become a source of revenue rather than just an expense. Municipalities interested in developing anaerobic digestion/combined heat and power (AD/CHP) facilities have the benefit of desirable options for sites, such as landfill gas facilities and wastewater treatment plants, and potential feedstocks in source-separated residential or municipal food waste or wastewater. This thesis examines the opportunities and challenges for municipal development of AD/CHP facilities in Massachusetts.

Pike, Brenda


Industrial symbiosis: corn ethanol fermentation, hydrothermal carbonization, and anaerobic digestion.  


The production of dry-grind corn ethanol results in the generation of intermediate products, thin and whole stillage, which require energy-intensive downstream processing for conversion into commercial animal feed products. Hydrothermal carbonization of thin and whole stillage coupled with anaerobic digestion was investigated as alternative processing methods that could benefit the industry. By substantially eliminating evaporation of water, reductions in downstream energy consumption from 65% to 73% were achieved while generating hydrochar, fatty acids, treated process water, and biogas co-products providing new opportunities for the industry. Processing whole stillage in this manner produced the four co-products, eliminated centrifugation and evaporation, and substantially reduced drying. With thin stillage, all four co-products were again produced, as well as a high quality animal feed. Anaerobic digestion of the aqueous product stream from the hydrothermal carbonization of thin stillage reduced chemical oxygen demand (COD) by more than 90% and converted 83% of the initial COD to methane. Internal use of this biogas could entirely fuel the HTC process and reduce overall natural gas usage. PMID:23568780

Wood, Brandon M; Jader, Lindsey R; Schendel, Frederick J; Hahn, Nicholas J; Valentas, Kenneth J; McNamara, Patrick J; Novak, Paige M; Heilmann, Steven M



Development of anaerobic digestion methods for palm oil mill effluent (POME) treatment.  


Palm oil mill effluent (POME) is a highly polluting wastewater that pollutes the environment if discharged directly due to its high chemical oxygen demand (COD) and biochemical oxygen demand (BOD) concentration. Anaerobic digestion has been widely used for POME treatment with large emphasis placed on capturing the methane gas released as a product of this biodegradation treatment method. The anaerobic digestion method is recognized as a clean development mechanism (CDM) under the Kyoto protocol. Certified emission reduction (CER) can be obtained by using methane gas as a renewable energy. This review aims to discuss the various anaerobic treatments of POME and factors that influence the operation of anaerobic treatment. The POME treatment at both mesophilic and thermophilic temperature ranges are also analyzed. PMID:18657414

Poh, P E; Chong, M F



Anaerobic digestion of sludge from intensive recirculating aquaculture systems: Review  

Microsoft Academic Search

Intensive recirculating aquaculture systems (RAS) produce high volumes of biosolid waste which is a potential source of pollution if not properly treated. A reduction in sludge-mass would therefore minimize the potential environmental hazard and economic burden stemming from its disposal. Recently, anaerobic digestion was suggested as an alternative to aquaculture sludge digestion and stabilization in RAS. This practice results not

Natella Mirzoyan; Yossi Tal; Amit Gross



Fate of 17B-estradiol in anaerobic lagoon digesters  

Technology Transfer Automated Retrieval System (TEKTRAN)

The fate of [14C]17B-estradiol ([14C]E2) was monitored for 42 d in triplicate 10 L anaerobic digesters. Total radioactive residues (TRR) decreased rapidly in the liquid layer of the digesters and reached a steady-state value of 19-24% of the initial dose after 4 days. LC/MS/MS analyses of the liqu...


Alkaline post-treatment for improved sludge anaerobic digestion.  


Alkaline post-treatment was tested in order to improve sludge anaerobic digestion. Between the 8th and the 12th hour of a 24-h digestion cycle, 5% of sludge was extracted from a semi-continuous digester with a sludge retention time of 20 days. The sludge was then disintegrated with 0.1 mol/L NaOH and returned to the digester after neutralization. The results showed that alkaline post-treatment increased the level of soluble organic substances in the extracted sludge, particularly of volatile fatty acids and polysaccharides. This process resulted in a 33% enhancement of biogas production in comparison with the control. When the ratio of the recycled sludge was further increased to 10% or 15%, the increment of biogas yield was reduced, due to excessive inactivation of anaerobic bacteria in the digester. Alkaline post-treatment had a minimal impact on the dewaterability of digested sludge. PMID:23688671

Li, Huan; Zou, Shuxin; Li, Chenchen; Jin, Yiying



Effect of alkaline pretreatment on anaerobic digestion of solid wastes  

SciTech Connect

The introduction of the anaerobic digestion for the treatment of the organic fraction of municipal solid waste (OFMSW) is currently of special interest. The main difficulty in the treatment of this waste fraction is its biotransformation, due to the complexity of organic material. Therefore, the first step must be its physical, chemical and biological pretreatment for breaking complex molecules into simple monomers, to increase solubilization of organic material and improve the efficiency of the anaerobic treatment in the second step. This paper describes chemical pretreatment based on lime addition (Ca(OH){sub 2}), in order to enhance chemical oxygen demand (COD) solubilization, followed by anaerobic digestion of the OFMSW. Laboratory-scale experiments were carried out in completely mixed reactors, 1 L capacity. Optimal conditions for COD solubilization in the first step of pretreatment were 62.0 mEq Ca(OH){sub 2}/L for 6.0 h. Under these conditions, 11.5% of the COD was solubilized. The anaerobic digestion efficiency of the OFMSW, with and without pretreatment, was evaluated. The highest methane yield under anaerobic digestion of the pretreated waste was 0.15 m{sup 3} CH{sub 4}/kg volatile solids (VS), 172.0% of the control. Under that condition the soluble COD and VS removal were 93.0% and 94.0%, respectively. The results have shown that chemical pretreatment with lime, followed by anaerobic digestion, provides the best results for stabilizing the OFMSW.

Lopez Torres, M. [National Center for Scientific Researcher (CNIC), Environmental Pollution Department (DECA), Ave. 25 y 158, Cubanacan, Playa, Havana City (Cuba)], E-mail:; Espinosa Llorens, Ma. del C. [National Center for Scientific Researcher (CNIC), Environmental Pollution Department (DECA), Ave. 25 y 158, Cubanacan, Playa, Havana City (Cuba)



Biogasification of sorghum in a novel anaerobic digester  

SciTech Connect

The Institute of Gas Technology (IGT) conducted pilot-scale anaerobic digestion experiments with ensiled sorghum in a 160 ft/sup 3/ digester at the experimental test unit (ETU) facility at the Walt Disney World Resort Complex in Florida. The study focused on improving bioconversion efficiencies and process stability by employing a novel reactor concept developed at IGT. Steady-state performance data were collected from the ETU as well as from a laboratory-scale conventional stirred tank reactor (CSTR) at loading rates of 0.25 and 0.50 lb organic matter/ft/sup 3/-day at mesophilic and thermophilic temperatures, respectively. This paper will describe the ETU facility, novel digester design and operating techniques, and the results obtained during 12 months of stable and uninterrupted operation of the ETU and the CSTR which showed that methane yields anad rates from the ETU were 20% to 50% higher than those of the CSTR. 10 refs., 7 figs., 5 tabs.

Srivastava, V.J.; Biljetina, R.; Isaacson, H.R.; Hayes, T.D.



Thermochemical liquidization of anaerobically digested and dewatered sludge and anaerobic retreatment  

Microsoft Academic Search

The pretreatment effect of thermochemical liquidization for the anaerobic retreatment of anaerobically digested and dewatered sludge was studied. The digested sludge (dry matter; 15.7%) was thermochemically liquidized at 175°C and 4 MPa with a holding time of 1 h. The liquidized sludge was separated by centrifugation to produce a supernatant of 44.7% (w\\/w) and precipitate of 52.3%. The liquidized sludge

Shigeki Sawayama; Seiichi Inoue; Kenichiro Tsukahara; Tomoko Ogi



A dispersion model of anaerobic wastewater treatment and feasibility study in anaerobic filter digester simulation  

Microsoft Academic Search

The parameters of anaerobic digestion include not only those of anaerobic biological reaction, but also those of the related operational?physical characteristics, such as dispersion, diffusion, cell accumulation and transportation. In this paper, we conduct a laboratory experiment to find out the relationship between design?operation parameters with dispersion, and combine this information with physical characteristics to set up the “dispersion model”.



Polychlorinated biphenyl concentration changes in sewage sludge and organic municipal waste mixtures during composting and anaerobic digestion.  


We determined the changes in polychlorinated biphenyl (PCB) concentrations in a mixture of sewage sludge and the organic fraction of municipal waste during composting and during anaerobic digestion. The processes were carried out on a laboratory scale. The PCBs were analyzed in the waste samples using gas chromatography-mass spectrometry. We evaluated the rates at which the PCB concentrations decreased during composting and during anaerobic digestion and compared the PCB degradation kinetics during these processes. The most important conclusion of this work is that anaerobic digestion is much more effective than composting at removing PCBs from a mixture of sewage sludge and the organic fraction of municipal waste. PMID:25618191

Siebielska, Izabela; Side?ko, Robert



Enhanced anaerobic digestion of food waste by thermal and ozonation pretreatment methods.  


Treatment of food waste by anaerobic digestion can lead to an energy production coupled to a reduction of the volume and greenhouse gas emissions from this waste type. According to EU Regulation EC1774/2002, food waste should be pasteurized/sterilized before or after anaerobic digestion. With respect to this regulation and also considering the slow kinetics of the anaerobic digestion process, thermal and chemical pretreatments of food waste prior to mesophilic anaerobic digestion were studied. A series of batch experiments to determine the biomethane potential of untreated as well as pretreated food waste was carried out. All tested conditions of both thermal and ozonation pretreatments resulted in an enhanced biomethane production. The kinetics of the anaerobic digestion process were, however, accelerated by thermal pretreatment at lower temperatures (<120 °C) only. The best result of 647.5 ± 10.6 mlCH4/gVS, which is approximately 52% higher as compared to the specific biomethane production of untreated food waste, was obtained with thermal pretreatment at 80 °C for 1.5 h. On the basis of net energy calculations, the enhanced biomethane production could cover the energy requirement of the thermal pretreatment. In contrast, the enhanced biomethane production with ozonation pretreatment is insufficient to supply the required energy for the ozonator. PMID:25169646

Ariunbaatar, Javkhlan; Panico, Antonio; Frunzo, Luigi; Esposito, Giovanni; Lens, Piet N L; Pirozzi, Francesco



Design of a municipal solid waste anaerobic digestion system at Folsom Prison  

SciTech Connect

This paper describes the design of an anaerobic digestion system for the treatment of the organic fraction of the municipal solid waste (MSW) from the city of Folsom, California. This organic fraction, estimated to be 76 tons per day, will be separated from the total waste stream (100 tons per day of MSW) at the materials recovery facility (MRF) operated by inmate labor from the Return-to-Custody (RTC) facility at Folsom Prison. The organic fraction will be shredded, the solids content will be adjusted to 30% or less using wastewater, and the resulting influent loaded into an anaerobic digester. The anaerobic fermentation treatment process will reduce the solids content of the organic fraction of the solid waste, while producing valuable methane gas for use as fuel for electrical generation. The resulting digested effluent will be aerobically composted and marketed as a soil amendment.

Williams, D.W.; Cavaletto, R. [California Polytechnic State Univ., San Luis Obispo, CA (United States); Harrison, L. [Prison Industry Authority, Folsom, CA (United States)] [and others



Effect of dietary arsonic acids on performance characteristics of swine waste anaerobic digesters  

SciTech Connect

A completely random design experiment was conducted to determine the effect of dietary arsonic acids on the performance of laboratory swine waste anaerobic digesters. Fortified corn-soybean meal diets containing no arsonic acids (control), 100 ppm arsanilic acid or 75 ppm roxarsone were fed to growing-finishing pigs. Fresh waste (including urine) from all treatments were collected daily for 74 days and loaded at a rate of 2.4 kg volatile solids/cubic meter into nine 25-L anaerobic digesters heated to 34 degrees with continuous agitation and total gas collection. After a 60-day acclimation period, daily gas production and composition and nutrient composition data were obtained from the anaerobic digesters. Inclusion of the arsonic acids in swine diets reduced dry matter and volatile solids content. Dietary arsonic acids also increased NH4+-N. Alky. was high in all the digesters; however, arsonic acids decreased alky. Dietary arsonic acids reduced the ratio of CH4 to CO2 in the gas compared to the control. Significant amounts of As accumulated in the digesters. Alcohol, ethanol, and propanol concentrations were increased by roxarsone, and arsanilic acid increased the PrCO2H concentrations over the percentage in both the roxarsone and control digesters.

Brumm, M.C.; Sutton, A.L.; Jones, D.D.



Anaerobic Digestion and Combined Heat and Power Study  

SciTech Connect

One of the underlying objectives of this study is to recover the untapped energy in wastewater biomass. Some national statistics worth considering include: (1) 5% of the electrical energy demand in the US is used to treat municipal wastewater; (2) This carbon rich wastewater is an untapped energy resource; (3) Only 10% of wastewater treatment plants (>5mgd) recover energy; (4) Wastewater treatment plants have the potential to produce > 575 MW of energy nationwide; and (5) Wastewater treatment plants have the potential to capture an additional 175 MW of energy from waste Fats, Oils and Grease. The WSSC conducted this study to determine the feasibility of utilizing anaerobic digestion and combined heat and power (AD/CHP) and/or biosolids gasification and drying facilities to produce and utilize renewable digester biogas. Digester gas is considered a renewable energy source and can be used in place of fossil fuels to reduce greenhouse gas emissions. The project focus includes: (1) Converting wastewater Biomass to Electricity; (2) Using innovative technologies to Maximize Energy Recovery; and (3) Enhancing the Environment by reducing nutrient load to waterways (Chesapeake Bay), Sanitary Sewer Overflows (by reducing FOG in sewers) and Greenhouse Gas Emissions. The study consisted of these four tasks: (1) Technology screening and alternative shortlisting, answering the question 'what are the most viable and cost effective technical approaches by which to recover and reuse energy from biosolids while reducing disposal volume?'; (2) Energy recovery and disposal reduction potential verification, answering the question 'how much energy can be recovered from biosolids?'; (3) Economic environmental and community benefit analysis, answering the question 'what are the potential economic, environmental and community benefits/impacts of each approach?'; and (4) Recommend the best plan and develop a concept design.

Frank J. Hartz; Rob Taylor; Grant Davies



Energetic and biochemical valorization of cork boiling wastewater by anaerobic digestion  

PubMed Central

Background In addition to energy benefits, anaerobic digestion offers other interesting advantages. The cork industry is of great environmental, economic and social significance in the western Mediterranean region, with Portugal being the world-leading producer and exporter. Cork boiling wastewater (CBW) is a toxic and recalcitrant organic effluent produced by this sector, which constitutes a serious environmental hazard. However, there is no documented research on anaerobic treatment/valorization performed with this effluent. The work presented here was developed with the aim to use the anaerobic digestion process to convert the CBW polluting organic load into an energy carrier gas and valuable molecules for industry. Results No lag phases were observed and a methane yield of 0.126 to 0.142 m3 kg-1 chemical oxygen demand (COD)added was registered in the mesophilic consortium experiments carried out in batch flasks at 37?±?1°C. Anaerobic digestion can be advantageously connected to ultrafiltration or electrochemical processes, due to the following: 1) reduction of ellagic acid content and consequent decrease of CBW viscosity; and 2) increase in conductivity after the anaerobic process, avoiding the electrolyte application of the electrochemical process. The improvement of several CBW biochemical features shows that anaerobic digestion may provide additionally useful molecules. The rise in concentration of some of these compounds, belonging to the benzoic acid family (gallic, protocatechuic, vanillic and syringic acids), is responsible for the increase of antiradical activity of the phenolic fraction. Additionally, some enzymatic activity was also observed and while the laccase activity increased in the digested effluent by anaerobiosis, xylanase was formed in the process. Conclusions The multidisciplinary approach adopted allowed the valorization of CBW in terms of energy and valuable biomolecules. By exploiting the anaerobic digestion process potential, a novel methodology to toxic and recalcitrant cork processing wastewater was developed. PMID:24847378



Anaerobic co-digestion of dairy manure and potato waste  

NASA Astrophysics Data System (ADS)

Dairy and potato are two important agricultural commodities in Idaho. Both the dairy and potato processing industries produce a huge amount of waste which could cause environmental pollution. To minimize the impact of potential pollution associated with dairy manure (DM) and potato waste (PW), anaerobic co-digestion has been considered as one of the best treatment process. The purpose of this research is to evaluate the anaerobic co-digestion of dairy manure and potato waste in terms of process stability, biogas generation, construction and operating costs, and potential revenue. For this purpose, I conducted 1) a literature review, 2) a lab study on anaerobic co-digestion of dairy manure and potato waste at three different temperature ranges (ambient (20-25°C), mesophilic (35-37°C) and thermophilic (55-57°C) with five mixing ratios (DM:PW-100:0, 90:10, 80:20, 60:40, 40:60), and 3) a financial analysis for anaerobic digesters based on assumed different capital costs and the results from the lab co-digestion study. The literature review indicates that several types of organic waste were co-digested with DM. Dairy manure is a suitable base matter for the co-digestion process in terms of digestion process stability and methane (CH4) production (Chapter 2). The lab tests showed that co-digestion of DM with PW was better than digestion of DM alone in terms of biogas and CH4 productions (Chapter 3). The financial analysis reveals DM and PW can be used as substrate for full size anaerobic digesters to generate positive cash flow within a ten year time period. Based on this research, the following conclusions and recommendations were made: ? The ratio of DM:PW-80:20 is recommended at thermophilic temperatures and the ratio of DM:PW-90:10 was recommended at mesophilic temperatures for optimum biogas and CH4 productions. ? In cases of anaerobic digesters operated with electricity generation equipment (generators), low cost plug flow digesters (capital cost of 600/cow) operating at thermophilic temperatures are recommended. • The ratio of DM:PW-90:10 or 80:20 is recommended while operating low cost plug flow digesters at thermophilic temperatures. ? In cases of anaerobic digesters operated without electricity generation equipment (generators), completely mixed or high or low cost plug flow digesters can be used. • The ratio of DM:PW-80:20 is recommended for completely mixed digesters operated at thermophilic temperatures; • The ratio of DM:PW-90:10 or 80:20 is recommended for high cost plug flow digesters (capital cost of 1,000/cow) operated at thermophilic temperatures; • All of the four co-digested mixing ratios (i.e. DM:PW-90:10 or 80:20 or 60:40 or 40:60) are good for low cost plug flow digesters (capital cost of $600/cow) operated at thermophilic temperatures. The ratio of DM:PW-90:10 is recommended for positive cash flow within the ten year period if the low cost plug flow digesters are operated at mesophilic temperatures.

Yadanaparthi, Sai Krishna Reddy


Animal digestive strategies versus anaerobic digestion bioprocesses for biogas production from lignocellulosic biomass  

Microsoft Academic Search

Herbivorous mammals and wood-eating insects are fairly effective in the digestion of plant polymers, such as lignocellulosics.\\u000a In order to improve methane production from the lignocellulosic biomass, several kinds of anaerobic digestion processes derived\\u000a from animal models have been devised. However, the rates of biodegradation occurring in the anaerobic bioreactors still remain\\u000a lower than in animal guts. The effectiveness of

Ali Bayané; Serge R. Guiot




EPA Science Inventory

Methane gas produced by anaerobic digestion of wastewater sludge can be upgraded to pipeline quality and sold to a public utility for injection into a natural gas distribution system. Upgrading the gas typically involves treatment for removal of carbon dioxide and hydrogen sulfid...


Biogas by semi-continuous anaerobic digestion of food waste.  


The semi-continuous anaerobic digestion of food waste was investigated in 1-L and 20-L continuously stirred tank reactors (CSTRs), to identify the optimum operation condition and the methane production of the semi-continuous anaerobic process. Results from a 1-L digester indicated that the optimum organic loading rate (OLR) for semi-continuous digestion is 8 g VS/L/day. The corresponding methane yield and chemical oxygen demand (COD) reduction were 385 mL/g VS and 80.2 %, respectively. Anaerobic digestion was inhibited at high OLRs (12 and 16 g VS/L/day), due to volatile fatty acid (VFA) accumulation. Results from a 20-L digester indicated that a higher methane yield of 423 mL/g VS was obtained at this larger scale. The analysis showed that the methane production at the optimum OLR fitted well with the determined kinetics equation. An obvious decrease on the methane content was observed at the initial of digestion. The increased metabolization of microbes and the activity decrease of methanogen caused by VFA accumulation explained the lower methane content at the initial of digestion. PMID:25773980

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



Anaerobic digestion as a waste disposal option for American Samoa  

SciTech Connect

Tuna sludge and municipal solid waste (MSW) generated on Tutuila Island, American Samoa, represent an ongoing disposal problem as well as an emerging opportunity for use in renewable fuel production. This research project focuses on the biological conversion of the organic fraction of these wastes to useful products including methane and fertilizer-grade residue through anaerobic high solids digestion. In this preliminary study, the anaerobic bioconversion of tuna sludge with MSW appears promising.

Rivard, C



Design of a large-scale anaerobic digestion facility for the recovery of energy from municipal solid waste  

SciTech Connect

The California Prison Industry Authority, in conjunction with the City of Folsom, operates a 100 ton/d municipal solid waste (MSW) recovery facility using inmate labor. Through manual sorting, all useful organic and inorganic materials are recycled for marketing. The remaining organic material will be further processed to remove hazardous and inert material and prepared as a feedstock for an anaerobic digestion process. The clean organic waste (approximately 78 ton/d) will then be shredded and completely mixed with sewage water prior feeding to the digester. Off gas from the digester will be collected as a fuel for the steam boiler or combusted in a waste gas burner. Steam will be injected directly into the digester for heating. The anaerobically digested material will be moved to compost area where it will be mixed with wood faction of yard waste and processed aerobically for the production of compost material as a soil amendment. Anaerobic digesters will be constructed in two phases. The first phase consists of the construction of one 26 ton/d digester to confirm the suitability of feeding and mixing equipment. Modifications will be made to the second and third digesters, in the second phase, based on operating experience of the first digester. This paper discusses important design features of the anaerobic digestion facility.

Kayhanian, M. [Univ. of California, Davis, CA (United States); Jones, D. [CH2M Hill, Sacramento, CA (United States)



Detoxifying CO2 capture reclaimer waste by anaerobic digestion.  


The decrease in toxicity of carbon capture reclaimer monoethanolamine (MEA) waste (MEAw) during anaerobic degradation of such waste together with easily degradable organics was investigated. Samples were collected from a bioreactor at steady state with 86 % organic chemical oxygen demand removal at room temperature, which had been running on MEAw for 2 years. The toxicity of the digester effluents were 126, 42 and 10 times lower than that of the MEAw to the tested freshwater trophic groups of Pseudokirchneriella subcapitata, Daphnia magna and embryos of Danio rerio, respectively. The toxicity of the tested taxonomic groups after anaerobic digestion was mainly attributed to the ammonia generated by the degradation of MEAw. PMID:24122630

Wang, Shuai; Hovland, Jon; Brooks, Steven; Bakke, Rune



Modified Anaerobic Digestion Model No.1 for dry and semi-dry anaerobic digestion of solid organic waste.  


The role of total solids (TS) content in anaerobic digestion of selected complex organic matter, e.g. rice straw and food waste, was investigated. A range of TS from wet (4.5%) to dry (23%) was evaluated. A modified version of the Anaerobic Digestion Model No.1 for a complex organic substrate is proposed to take into account the effect of the TS content on anaerobic digestion. A linear function that correlates the kinetic constants of three specific processes (i.e. disintegration, acetate and propionate up-take) was included in the model. Results of biomethanation and volatile fatty acids production tests were used to calibrate the proposed model. Model simulations showed a good agreement between numerical and observed data. PMID:25311887

Liotta, Flavia; Chatellier, Patrice; Esposito, Giovanni; Fabbricino, Massimiliano; Frunzo, Luigi; van Hullebusch, Eric D; Lens, Piet N L; Pirozzi, Francesco



Anaerobically digested poultry slaughterhouse wastes as fertiliser in agriculture  

Microsoft Academic Search

Chemical and physical analysis, 27-d plant growth assays with carrot (Daucus carota) and Chinese cabbage (Brassica campestris var. chinensis), and 5-d phytotoxicity assays with Chinese cabbage and perennial ryegrass (Lolium perenne) were used to investigate the suitability of anaerobically digested poultry slaughterhouse waste for fertiliser in agriculture and the effect of aerobic post-treatment on the properties of the digested material.The

E Salminen; J Rintala; J Härkönen; M Kuitunen; H Högmander; A Oikari



Anaerobic digestion and wastewater treatment systems  

Microsoft Academic Search

Upflow Anaerobic Sludge Bed (UASB) wastewater (pre-)treatment systems represent a proven sustainable technology for a wide range of very different industrial effluents, including those containing toxic\\/inhibitory compounds. The process is also feasible for treatment of domestic wastewater with temperatures as low as 14–16° C and likely even lower. Compared to conventional aerobic treatment systems the anaerobic treatment process merely offers

G. Lettinga



Labscale Evaluation of Biomass-Derived Elements Used in Anaerobic Digestion  

E-print Network

Labscale Evaluation of Biomass-Derived Elements Used in Anaerobic Digestion This report presents performance data for an anaerobic digestion system (at a 10-liter scale) utilizing corncob biochar as biofilm support. The system operated on grease-trap wastewater and high-rate anaerobic digestion of this material



Microsoft Academic Search

The anaerobic digestion of solid wastes is now a widely- used technology in Europe with more than 50 full- scale plants operating. However, anaerobic solid waste digestion is still used to only a limited extent in North America with only three facilities in Canada. Because of the expected importance of anaerobic digestion in the future for energy recovery, reliable tools

Mariana Chavez-Vazquez; David M. Bagley


Rapid fluorescence-based measurement of toxicity in anaerobic digestion.  


A rapid fluorescence measurement based on resazurin reduction was developed and applied for the detection of toxicants/inhibitors to anaerobic digestion metabolism. By initially using a pure facultative anaerobic strain, Enterococcus faecalis as a model organism, this technique proved to be fast and sensitive when detecting the model toxicant, pentachlorophenol (PCP). The technique revealed significant metabolic changes in Enterococcus faecalis with a PCP spike ranging from 0.05 to 100 mg/L, and could detect PCP's toxicity to E. faecalis at a concentration of only 0.05 mg/L in 8 min. Furthermore, by extending this technique to a mixed anaerobic sludge, not only could the effect of 0.05-100 mg/L PCP be determined on anaerobic digestion metabolism within 10 min, but also its rate of biogas production. These results suggest that a resazurin-based fluorescence measurement can potentially be incorporated into a microfluidic system to develop a biosensor for the real-time monitoring, control and early warning of toxicant/inhibitor loads in the influent to an anaerobic digestion system. PMID:25768985

Chen, Jian Lin; Ortiz, Raphael; Xiao, Yeyuan; Steele, Terry W J; Stuckey, David C



Intermediate-scale high-solids anaerobic digestion system operational development  

SciTech Connect

Anaerobic bioconversion of solid organic wastes represents a disposal option in which two useful products may be produced, including a medium Btu fuel gas (biogas) and a compost-quality organic residue. The application of high-solids technology may offer several advantages over conventional low-solids digester technology. Operation of the anaerobic digestion process at high solids reduces the level of process water and thereby the size and capital costs for the digester system. In addition, by virtue of the lack of available water, the microbial catalysts are more productive in feedstock polymer hydrolysis. The National Renewable Energy Laboratory (NREL) has developed a unique digester system capable of uniformly mixing high-solids materials at low cost. Information gained from laboratory-scale digester research was used to develop die intermediate-scale digester system. This system represents a 50-fold scale-up of the original digester system and includes continuous feed addition and computer monitoring and control. During the first 1.15 years of operation, a variety of modifications and improvements were instituted to increase the safety, reliability, and performance of the system. Those improvements -- which may be critical in further scale-up efforts using the NREL high-solids digester design -- are detailed in this report.

Rivard, C.J.



Anaerobic Digestion. Instructor's Guide. Biological Treatment Process Control.  

ERIC Educational Resources Information Center

This instructor's guide contains materials needed to teach a four-lesson unit on anaerobic digestion control. These materials include: (1) unit overview; (2) lesson plans; (3) lecture outlines; (4) student worksheets for each lesson (with answers); and (5) two copies of a final quiz (with and without answers). Lesson 1 is a review of the theory of…

Carnegie, John W., Ed.


Anaerobic Digestion Analysis. Training Module  

ERIC Educational Resources Information Center

This document is an instructional module package prepared in objective form for use by an instructor familiar with alkalinity, volatile acids and carbon dioxide determinations for an anaerobic sludge digester. Included are objectives, instructor guides, student handouts and transparency masters. This module considers total and bicarbonate…

Kirkwood Community Coll., Cedar Rapids, IA.



EPA Science Inventory

A field-scale research project was conducted in 2004-2005 to evaluate land application of anaerobically digested biosolids at agronomic levels. Biosolids had not been applied to this land previously. For this study, biosolids wee applied in a 100-m diameter circle by a side dis...


Biogas energy production from tropical biomass wastes by anaerobic digestion  

Technology Transfer Automated Retrieval System (TEKTRAN)

Anaerobic digestion (AD) is an attractive technology in tropical regions for converting locally abundant biomass wastes into biogas which can be used to produce heat, electricity, and transportation fuels. However, investigations on AD of tropical forestry wastes, such as albizia biomass, and food w...


Biogas production from anaerobic digestion of Spirulina maxima algal biomass  

Microsoft Academic Search

The photosynthetic spectrum of solar energy could be exploited for the production of chemical energy of methane through the combined algal-bacterial process. In this process, the algae are mass produced from light and from carbon in the first step. The algal biomass is then used as a nutrient for feeding the anaerobic digester, in the second step, for the production

Rejean Samson; Anh LeDuy



Anaerobic Co-Digestion on Dairies in Washington State  

E-print Network

as food-processing wastes) to increase biogas productivity, improve digester performance, and increase in manure and other feedstock to methane-rich biogas, a source of renewable energy (US-EPA 2006) (Figure 1-EPA 2005; US-EPA 2008). In addition to biogas, AD generates fiber and Figure 1. Overview of anaerobic

Collins, Gary S.


Anaerobic digestion and digestate use: accounting of greenhouse gases and global warming contribution.  


Anaerobic digestion (AD) of source-separated municipal solid waste (MSW) and use of the digestate is presented from a global warming (GW) point of view by providing ranges of greenhouse gas (GHG) emissions that are useful for calculation of global warming factors (GWFs), i.e. the contribution to GW measured in CO(2)-equivalents per tonne of wet waste. The GHG accounting was done by distinguishing between direct contributions at the AD facility and indirect upstream or downstream contributions. GHG accounting for a generic AD facility with either biogas utilization at the facility or upgrading of the gas for vehicle fuel resulted in a GWF from -375 (a saving) to 111 (a load) kg CO(2)-eq. tonne(-1) wet waste. In both cases the digestate was used for fertilizer substitution. This large range was a result of the variation found for a number of key parameters: energy substitution by biogas, N(2)O-emission from digestate in soil, fugitive emission of CH( 4), unburned CH(4), carbon bound in soil and fertilizer substitution. GWF for a specific type of AD facility was in the range -95 to -4 kg CO(2)-eq. tonne(-1) wet waste. The ranges of uncertainty, especially of fugitive losses of CH(4) and carbon sequestration highly influenced the result. In comparison with the few published GWFs for AD, the range of our data was much larger demonstrating the need to use a consistent and robust approach to GHG accounting and simultaneously accept that some key parameters are highly uncertain. PMID:19748957

Møller, Jacob; Boldrin, Alessio; Christensen, Thomas H



Anaerobic digestion of microalgal biomass after ultrasound pretreatment.  


High rate algal ponds are an economic and sustainable alternative for wastewater treatment, where microalgae and bacteria grow in symbiosis removing organic matter and nutrients. Microalgal biomass produced in these systems can be valorised through anaerobic digestion. However, microalgae anaerobic biodegradability is limited by the complex cell wall structure and therefore a pretreatment step may be required to improve the methane yield. In this study, ultrasound pretreatment at a range of applied specific energy (16-67 MJ/kg TS) was investigated prior to microalgae anaerobic digestion. Experiments showed how organic matter solubilisation (16-100%), hydrolysis rate (25-56%) and methane yield (6-33%) were improved as the pretreatment intensity increased. Mathematical modelling revealed that ultrasonication had a higher effect on the methane yield than on the hydrolysis rate. A preliminary energy assessment indicated that the methane yield increase was not high enough as to compensate the electricity requirement of ultrasonication without biomass dewatering (8% VS). PMID:25002372

Passos, Fabiana; Astals, Sergi; Ferrer, Ivet



Inactivation of Selected Bacterial Pathogens in Dairy Cattle Manure by Mesophilic Anaerobic Digestion (Balloon Type Digester)  

PubMed Central

Anaerobic digestion of animal manure in biogas digesters has shown promise as a technology in reducing the microbial load to safe and recommended levels. We sought to treat dairy manure obtained from the Fort Hare Dairy Farm by investigating the survival rates of bacterial pathogens, through a total viable plate count method, before, during and after mesophilic anaerobic digestion. Different microbiological media were inoculated with different serial dilutions of manure samples that were withdrawn from the biogas digester at 3, 7 and 14 day intervals to determine the viable cells. Data obtained indicated that the pathogens of public health importance were 90%–99% reduced in the order: Campylobacter sp. (18 days) < Escherichia coli sp. (62 days) < Salmonella sp. (133 days) from a viable count of 10.1 × 103, 3.6 × 105, 7.4 × 103 to concentrations below the detection limit (DL = 102 cfu/g manure), respectively. This disparity in survival rates may be influenced by the inherent characteristics of these bacteria, available nutrients as well as the stages of the anaerobic digestion process. In addition, the highest p-value i.e., 0.957 for E. coli showed the statistical significance of its model and the strongest correlation between its reductions with days of digestion. In conclusion, the results demonstrated that the specific bacterial pathogens in manure can be considerably reduced through anaerobic digestion after 133 days. PMID:25026086

Manyi-Loh, Christy E.; Mamphweli, Sampson N.; Meyer, Edson L.; Okoh, Anthony I.; Makaka, Golden; Simon, Michael



Pathogen survival during anaerobic digestion: Fatty acids inhibit anaerobic growth of Escherichia coli  

Microsoft Academic Search

Summary The fate of pathogens in anaerobic digesters has been studied in a laboratory model system in which glucose-nutrient broth cultures of genetically-defined strains ofEscherichia coli received additions of fatty acids at concentrations similar to those attained during anaerobic treatment of farm wastes. Marked concentration-dependent inhibition of growth was observed for both antibiotic resistant and sensitive strains, and the effects

Pirshing Abdul; David Lloyd




Technology Transfer Automated Retrieval System (TEKTRAN)

Anaerobic digestion of three different organic solid wastes was investigated with a two-phase pilot-scale anaerobic digestion (AD) system. The wastes were cow manure (CM), organic fraction of municipal solid waste (OFMSW), and cotton gin waste (CGW). The OFMSW and CM were digested as single wastes...


Factors controlling pathogen destruction during anaerobic digestion of biowastes  

SciTech Connect

Anaerobic digestion is the principal method of stabilising biosolids from urban wastewater treatment in the UK, and it also has application for the treatment of other types of biowaste. Increasing awareness of the potential risks to human and animal health from environmental sources of pathogens has focused attention on the efficacy of waste treatment processes at destroying pathogenic microorganisms in biowastes recycled to agricultural land. The degree of disinfection achieved by a particular anaerobic digester is influenced by a variety of interacting operational variables and conditions, which can often deviate from the ideal. Experimental investigations demonstrate that Escherichia coli and Salmonella spp. are not damaged by mesophilic temperatures, whereas rapid inactivation occurs by thermophilic digestion. A hydraulic, biokinetic and thermodynamic model of pathogen inactivation during anaerobic digestion showed that a 2 log{sub 10} reduction in E. coli (the minimum removal required for agricultural use of conventionally treated biosolids) is likely to challenge most conventional mesophilic digesters, unless strict maintenance and management practices are adopted to minimise dead zones and by-pass flow. Efficient mixing and organic matter stabilisation are the main factors controlling the rate of inactivation under mesophilic conditions and not a direct effect of temperature per se on pathogenic organisms.

Smith, S.R. [Centre for Environmental Control and Waste Management, Department of Civil and Environmental Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom)]. E-mail:; Lang, N.L. [Centre for Environmental Control and Waste Management, Department of Civil and Environmental Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom); Cheung, K.H.M. [Centre for Environmental Control and Waste Management, Department of Civil and Environmental Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom); Spanoudaki, K. [Centre for Environmental Control and Waste Management, Department of Civil and Environmental Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ (United Kingdom)



Anaerobic digestion of yard waste with hydrothermal pretreatment.  


The digestibility of lignocellulosic biomass is limited by its high content of refractory components. The objective of this study is to investigate hydrothermal pretreatment and its effects on anaerobic digestion of sorted organic waste with submerged fermentation. Hydrothermal pretreatment (HT) was performed prior to anaerobic digestion, and three agents were examined for the HT: hot compressed water, alkaline solution, and acidic solution. The concentrations of glucose and xylose were the highest in the sample pretreated in acidic solution. Compared with that of the untreated sample, the biogas yields from digesting the samples pretreated in alkaline solution, acidic solution, and hot water increased by 364, 107, and 79%, respectively. The decrease of chemical oxygen demand (COD) in liquid phase followed the same order as for the biogas yield. The initial ammonia content of the treated samples followed the order sample treated in acidic solution > sample treated in alkaline solution > sample treated in hot water. The concentrations of volatile fatty acids (VFAs) were low, indicating that the anaerobic digestion process was running at continuously stable conditions. PMID:24425302

Li, Wangliang; Zhang, Guangyi; Zhang, Zhikai; Xu, Guangwen



Anaerobic Digestion I. Sludge Treatment and Disposal Course #166. Instructor's Guide [and] Student Workbook.  

ERIC Educational Resources Information Center

This lesson is the first of a two-part series on anaerobic digestion. Topics discussed include the five basic functions of an anaerobic digester, basic theory of the biological processes involved, basic equipment necessary for digestion, and the products of digestion. The lesson includes an instructor's guide and student workbook. The instructor's…

Arasmith, E. E.


Anaerobic digestion: concepts, limits and perspectives  

Microsoft Academic Search

Anaerobic degradation processes are faced with limitations with respect to reaction energetics and reaction kinetics. The small amount of energy available in methanogenic degradation of complex organic compounds allows in most cases only the conservation of minimum amounts of energy in the lowest range of energy exploitable by biochemical reactions for ATP-synthesis. This limit has to be defined in the

B. Schink



Early warning indicators for monitoring the process failure of anaerobic digestion system of food waste.  


To determine reliable state parameters which could be used as early warning indicators of process failure due to the acidification of anaerobic digestion of food waste, three mesophilic anaerobic digesters of food waste with different operation conditions were investigated. Such parameters as gas production, methane content, pH, concentrations of volatile fatty acid (VFA), alkalinity and their combined indicators were evaluated. Results revealed that operation conditions significantly affect the responses of parameters and thus the optimal early warning indicators of each reactor differ from each other. None of the single indicators was universally valid for all the systems. The universally valid indicators should combine several parameters to supply complementary information. A combination of total VFA, the ratio of VFA to total alkalinity (VFA/TA) and the ratio of bicarbonate alkalinity to total alkalinity (BA/TA) can reflect the metabolism of the digesting system and realize rapid and effective early warning. PMID:25218457

Li, Lei; He, Qingming; Wei, Yunmei; He, Qin; Peng, Xuya



Anaerobic digestion of stillage to produce bioenergy in the sugarcane-to-ethanol industry.  


Stillage is the main wastewater from ethanol production, containing a high chemical oxygen demand in addition to acidic and corrosive characteristics. Though stillage may be used as a soil fertilizer, its land application may be considered problematic due its high polluting potential. Anaerobic digestion represents an effective alternative treatment to reduce the pollution load of stillage. In addition, the methane gas produced within the process may be converted to energy, which can be directly applied to the treatment plant. The objective of this paper was to investigate the energetic potential of anaerobic digestion applied to stillage in the sugarcane ethanol industry. An overall analysis of the results indicates energy recovery capacity (ERC) values for methane ranging from 3.5% to 10%, respectively, for sugarcane juice and molasses. The processes employed to obtain the fermentable broth, as well as the distillation step, represent the main limiting factors to the energetic potential feasibility. Considering financial aspects the annual savings could reach up to US$ 30 million due to anaerobic digestion of stillage in relatively large-scale distilleries (365,000 m3 of ethanol per year). The best scenarios were verified for the association between anaerobic digestion of stillage and combustion of bagasse. In this case, the fossil fuels consumption in distilleries could be fully ceased, such the ERC of methane could reach values ranging from 140% to 890%. PMID:24600872

Fuess, Lucas Tadeu; Garcia, Marcelo Loureiro



Counteracting ammonia inhibition in anaerobic digestion by removal with a hollow fiber membrane contactor.  


The aim of the current study was to investigate the feasibility of membrane contactors for continuous ammonia (NH?-N) removal in an anaerobic digestion process and to counteract ammonia inhibition. Two laboratory anaerobic digesters were fed slaughterhouse wastes with ammonium (NH??) concentrations ranging from 6 to 7.4 g/L. One reactor was used as reference reactor without any ammonia removal. In the second reactor, a hollow fiber membrane contactor module was used for continuous ammonia removal. The hollow fiber membranes were directly submerged into the digestate of the anaerobic reactor. Sulfuric acid was circulated in the lumen as an adsorbent solution. Using this set up, the NH??-N concentration in the membrane reactor was significantly reduced. Moreover the extraction of ammonia lowered the pH by 0.2 units. In combination that led to a lowering of the free NH?-N concentration by about 70%. Ammonia inhibition in the reference reactor was observed when the concentration exceeded 6 g/L NH??-N or 1-1.2 g/L NH?-N. In contrast, in the membrane reactor the volatile fatty acid concentration, an indicator for process stability, was much lower and a higher gas yield and better degradation was observed. The chosen approach offers an appealing technology to remove ammonia directly from media having high concentrations of solids and it can help to improve process efficiency in anaerobic digestion of ammonia rich substrates. PMID:22763291

Lauterböck, B; Ortner, M; Haider, R; Fuchs, W



Extracellular polymeric substances and dewaterability of waste activated sludge during anaerobic digestion.  


Anaerobic digestion of waste activated sludge was conducted to gain insight into the mechanisms underlying change in sludge dewaterability during its anaerobic digestion. Unexpectedly, the results indicated that sludge dewatering properties measured by capillary suction time only deteriorated after 10 days of anaerobic digestion, after which dewaterability recovered and remained stable. The loosely bound extracellular polymeric substance (LB-EPS) content increased three-fold after 20 days of anaerobic digestion, and did not change significantly during the remaining 30 days. The tightly bound EPS (TB-EPS) content reduced slightly after 20 days of anaerobic digestion, and stabilized during the last 30 days. Polysaccharides (PS) and proteins (PN) content in LB-EPS increased after 10 days of anaerobic digestion. However, PS and PN contents in TB-EPS decreased slightly. The relationship analysis showed that only LB-EPS correlated with dewaterability of the sludge during anaerobic digestion. PMID:25401321

Ye, Fenxia; Liu, Xinwen; Li, Ying



Toxicity of heavy metals to thermophilic anaerobic digestion  

Microsoft Academic Search

The effects of heavy metals on the thermophilic digestion of sewage sludge was studied in three semicontinuous digesters step-fed with cadmium, copper and nickel, respectively. The daily gas production, gas composition, the quantitative accumulation of volatile fatty acids, and the distribution of the heavy metals were measured. The fermentations were carried out at 58°C with a retention time of 10

B. K. Ahring; P. Westermann



A mass transfer model of ammonia volatilisation from anaerobic digestate  

SciTech Connect

Anaerobic digestion (AD) is becoming increasingly popular for treating organic waste. The methane produced can be burned to generate electricity and the digestate, which is high in mineral nitrogen, can be used as a fertiliser. In this paper we evaluate potential losses of ammonia via volatilisation from food waste anaerobic digestate using a closed chamber system equipped with a sulphuric acid trap. Ammonia losses represent a pollution source and, over long periods could reduce the agronomic value of the digestate. Observed ammonia losses from the experimental system were linear with time. A simple non-steady-state partitioning model was developed to represent the process. After calibration, the model was able to describe the behaviour of ammonia in the digestate and in the trap very well. The average rate of volatilisation was approximately 5.2 g N m{sup -2} week{sup -1}. The model was used to extrapolate the findings of the laboratory study to a number of AD storage scenarios. The simulations highlight that open storage of digestate could result in significant losses of ammonia to the atmosphere. Losses are predicted to be relatively minor from covered facilities, particularly if depth to surface area ratio is high.

Whelan, M.J., E-mail: [School of Applied Sciences, Cranfield University, College Road, Cranfield, Bedfordshire, MK43 0AL (United Kingdom); Everitt, T.; Villa, R. [School of Applied Sciences, Cranfield University, College Road, Cranfield, Bedfordshire, MK43 0AL (United Kingdom)



Study of Resource Recovery and Epidemiology in an Anaerobic Digester  

NASA Technical Reports Server (NTRS)

Three 4-liter packed bed anaerobic digesters were fabricated and operated at 35 degrees C, pH around 7, and hydraulic retention time (HRT) of 20, 10 and 5 days to study the resource recovery and epidemiology in a controlled ecological life support system (CELSS). A simulated wastewater, consisted of shower water, clothwash water, dishwasher water, handwash water, and urine flush water was used as the feeding solution. Under steady-state operation, chemical oxygen demand (COD), total organic carbon (TOC), pH, nitrogen, phosphorus, and potassium wer monitored in the digester input and output solutions. The volume and the CH4/CO2 ratios in the biogas produced from the anaerobic digesters were measured. The results indicate about 90 percent of TOC is converted while only 5-8 percent of N-P-K are consumed in the digester. A multi-drug resistant strain of Salmonella choleraesuis was used as the indicator bacterium in the epidemiology study. The levels of Salmonella choleraesuis in the influent and the effluent wer determined and decimal decay rate constants, k(d), were estimated. The k(d) values were greater at higher initial doses than lower doses for the same HR, and greater for batch digestion (7.89/d) than for continuous digestion (4.28, 3.82, and 3.82/d for 20, 10, and 5 d HRT, respectively).

Li, K. Y.; Cao, Song; Hunt, M. D.; Fu, Xuping



Development of a new genetic algorithm to solve the feedstock scheduling problem in an anaerobic digester  

NASA Astrophysics Data System (ADS)

As worldwide environmental awareness grow, alternative sources of energy have become important to mitigate climate change. Biogas in particular reduces greenhouse gas emissions that contribute to global warming and has the potential of providing 25% of the annual demand for natural gas in the U.S. In 2011, 55,000 metric tons of methane emissions were reduced and 301 metric tons of carbon dioxide emissions were avoided through the use of biogas alone. Biogas is produced by anaerobic digestion through the fermentation of organic material. It is mainly composed of methane with a rage of 50 to 80% in its concentration. Carbon dioxide covers 20 to 50% and small amounts of hydrogen, carbon monoxide and nitrogen. The biogas production systems are anaerobic digestion facilities and the optimal operation of an anaerobic digester requires the scheduling of all batches from multiple feedstocks during a specific time horizon. The availability times, biomass quantities, biogas production rates and storage decay rates must all be taken into account for maximal biogas production to be achieved during the planning horizon. Little work has been done to optimize the scheduling of different types of feedstock in anaerobic digestion facilities to maximize the total biogas produced by these systems. Therefore, in the present thesis, a new genetic algorithm is developed with the main objective of obtaining the optimal sequence in which different feedstocks will be processed and the optimal time to allocate to each feedstock in the digester with the main objective of maximizing the production of biogas considering different types of feedstocks, arrival times and decay rates. Moreover, all batches need to be processed in the digester in a specified time with the restriction that only one batch can be processed at a time. The developed algorithm is applied to 3 different examples and a comparison with results obtained in previous studies is presented.

Cram, Ana Catalina


Dynamic simulation model for anaerobic digestion of cellulose  

SciTech Connect

A simple yet useful dynamic simulator for the anaerobic digestion of cellulosic feedstock has been developed. The incentive for this simulator is a need for guidance in design and optimization of an anaerobic digestin process for volume reduction and stabilization of low-level radioactive wastes generated at Oak Ridge National Laboratory. These wastes are primarily blotter and other paper and cotton/polyester clothing. Anaerobic digestion will convert a substantial mass (and hence volume) of waste to gaseous products which can be flared or simply released. The remaining sludge will contain the radionuclides and is expected to have only 5 to 10% of the original waste volume. This stabilized sludge will be more suitable for disposal by shallow land burial than is the original untreated waste. The liquid effluent will go to existing treatment facilities for hot liquids at Oak Ridge National Laboratory (ORNL). An anaerobic digestion process can be scaled to handle small or modest quantities of waste and is expected to be vastly superior to incineration in this regard.

Lee, D.D.; Donaldson, T.L.



Survival of multidrug-resistant bacteria in thermophilic and mesophilic anaerobic co-digestion of dairy manure and waste milk.  


Anaerobic digestion is considered as a promising method to manage animal waste with antibiotic-resistant bacteria. Current research was conducted to investigate the survival of multidrug-resistant bacteria (MDRB) resistant to three groups of antibiotics: (i) cefazolin, neomycin, vancomycin, kanamycin (group 1); (ii) penicillin, oxytetracycline, ampicillin, streptomycin (group 2); and (iii) cefazolin, neomycin, vancomycin, kanamycin, penicillin, oxytetracycline, ampicillin, streptomycin (group 3), in anaerobic digestion of dairy manure and co-digestion of dairy manure and waste milk at 37°C and 55°C for 22 days, respectively. The population densities of three groups of MDRB on peptone, tryptone, yeast and glucose agar plates incubated at 30°C for 7 days before and after digestion showed 100% destruction in both digestates at thermophilic temperature. Overall reduction of more than 90% of three groups of MDRB was observed in mesophilic digestion with no significant differences (P?>?0.05) between manure and milk mixture. Co-digestion of dairy manure and waste milk always produced significantly (P?gas and methane gas than digestion of manure alone at both temperatures. Gas production in each case was significantly (P?digestion than in mesophilic digestion. The results demonstrate that thermophilic co-digestion of dairy manure and waste milk offers more benefits in terms of the environment and economy. PMID:23607603

Beneragama, Nilmini; Iwasaki, Masahiro; Lateef, Suraju A; Yamashiro, Takaki; Ihara, Ikko; Umetsu, Kazutaka



Anaerobic digestion for energy production and environmental protection  

SciTech Connect

Anaerobic digestion is the decomposition of complex molecules into simpler substances by micro-organisms in the absence of oxygen. Anaerobic digestion processes can be employed for resource conservation, for the production of biogas and other useful end products from biomass, and for environmental protection through waste and wastewater treatment. Modern high-rate anaerobic wastewater-treatment processes can effectively remove organic pollutants from wastewater at a cost far below that of conventional aerobic processes. These anaerobic wastewater treatment processes can also be profitably applied for the generation of biogas from energy crops such as sugarcane. In fact, these methods might even be an attractive alternative for the alcohol fermentation extensively employed in Brazil for the production of fuel alcohol from sugarcane. The potential of modern anaerobic processes for this purpose has not yet been widely recognized. This paper describes the principles and use of these processes and demonstrates their prospects for producing energy from sugarcane (1) by treating vinasse, the wastewater generated during the production of ethanol from sugarcane, and (2) as a direct method for producing biogas from sugarcane juice.

Lettinga, G. [Agricultural Univ., Wageningen (Netherlands); Haandel, A.C. Vaan [Federal Univ. of Paraiba, Campina Grande (Brazil)



Electrochemical mineralization of anaerobically digested olive mill wastewater.  


A novel approach was developed for the energetic valorisation and treatment of olive mill wastewater (OMW), combining anaerobic digestion and electrochemical oxidation. The electrochemical treatment was proposed as the final step to mineralize the remaining OMW fraction from the anaerobic reactor. The electrooxidation of anaerobically digested OMW was investigated over dimensionally stable anodes (DSAs). RuO(2) based anode was significantly more efficient than IrO(2)-type DSA, mainly for the COD removal. IrO(2) based anode promoted a selective oxidation of phenols and colour removal. For instance, after an electrolysis charge of 10.4 × 10(4) C L(-1), COD removals of 14 and 99%, phenols removals of 91 and 100% and colour removals of 85 and 100% were obtained for IrO(2) and RuO(2) DSAs-type, respectively. The electrochemical post-treatment was effectively performed without using a supporting electrolyte and in the presence of the solids that remained from the anaerobic process. The achievement of the required effluent quality for sewer systems disposal depends on the operating conditions of the anaerobic process. Consequently, special care must be taken with the chloride and nitrogen levels that may surpass the legal discharge limits. The electrochemical oxidation over RuO(2) based DSA is an appropriate second-step treatment for OMW disposal, after the recovery of its energetic potential. PMID:22687524

Gonçalves, M R; Marques, I P; Correia, J P



Anaerobic digestion of pulp and paper mill wastewater and sludge.  


Pulp and paper mills generate large amounts of waste organic matter that may be converted to renewable energy in form of methane. The anaerobic treatment of mill wastewater is widely accepted however, usually only applied to few selected streams. Chemical oxygen demand (COD) removal rates in full-scale reactors range between 30 and 90%, and methane yields are 0.30-0.40 m(3) kg(-1) COD removed. Highest COD removal rates are achieved with condensate streams from chemical pulping (75-90%) and paper mill effluents (60-80%). Numerous laboratory and pilot-scale studies have shown that, contrary to common perception, most other mill effluents are also to some extent anaerobically treatable. Even for difficult-to-digest streams such as bleaching effluents COD removal rates range between 15 and 90%, depending on the extent of dilution prior to anaerobic treatment, and the applied experimental setting. Co-digestion of different streams containing diverse substrate can level out and diminish toxicity, and may lead to a more robust microbial community. Furthermore, the microbial population has the ability to become acclimated and adapted to adverse conditions. Stress situations such as toxic shock loads or temporary organic overloading may be tolerated by an adapted community, whereas they could lead to process disturbance with an un-adapted community. Therefore, anaerobic treatment of wastewater containing elevated levels of inhibitors or toxicants should be initiated by an acclimation/adaptation period that can last between a few weeks and several months. In order to gain more insight into the underlying processes of microbial acclimation/adaptation and co-digestion, future research should focus on the relationship between wastewater composition, reactor operation and microbial community dynamics. The potential for engineering and managing the microbial resource is still largely untapped. Unlike in wastewater treatment, anaerobic digestion of mill biosludge (waste activated sludge) and primary sludge is still in its infancy. Current research is mainly focused on developing efficient pretreatment methods that enable fast hydrolysis of complex organic matter, shorter sludge residence times and as a consequence, smaller sludge digesters. Previous experimental studies indicate that the anaerobic digestibility of non-pretreated biosludge from pulp and paper mills varies widely, with volatile solids (VS) removal rates of 21-55% and specific methane yields ranging between 40 and 200 mL g(-1) VS fed. Pretreatment can increase the digestibility to some extent, however in almost all reported cases, the specific methane yield of pretreated biosludge did not exceed 200 mL g(-1) VS fed. Increases in specific methane yield mostly range between 0 and 90% compared to non-pretreated biosludge, whereas larger improvements were usually achieved with more difficult-to-digest biosludge. Thermal treatment and microwave treatment are two of the more effective methods. The heat required for the elevated temperatures applied in both methods may be provided from surplus heat that is often available at pulp and paper mills. Given the large variability in specific methane yield of non-pretreated biosludge, future research should focus on the links between anaerobic digestibility and sludge properties. Research should also involve mill-derived primary sludge. Although biosludge has been the main target in previous studies, primary sludge often constitutes the bulk of mill-generated sludge, and co-digestion of a mixture between both types of sludge may become practical. The few laboratory studies that have included mill primary sludge indicate that, similar to biosludge, the digestibility can range widely. Long-term studies should be conducted to explore the potential of microbial adaptation to lignocellulosic material which can constitute more than half of the organic matter in pulp and paper mill sludge. PMID:25150519

Meyer, Torsten; Edwards, Elizabeth A



Anaerobic digestion of livestock manures: A current opportunities casebook  

SciTech Connect

Growth and concentration of the livestock industry creates new opportunities for proper disposal of the large quantities of manures generated at dairy, swine, and poultry farms. One manure management system provides not only pollution prevention but also converts a problem into a new profit center. Economic evaluations and case studies of operating systems indicate that the anaerobic digestion of livestock manures is a commercially-available bioconversion technology with considerable potential for providing profitable co-products, including a renewable fuel. An introduction to the engineering economies of these technologies is provided, based on estimates of digesters that generate electricity from the recovered methane. Regression models used to estimate digester cost and internal rate of return are developed from the evaluations. Case studies of operating digesters, including project and maintenance histories, and the operator`s {open_quotes}lessons learned{close_quotes}, are provided as a reality check.

Lusk, P.D.



Biogas plasticization coupled anaerobic digestion: the anaerobic pump stoichiometry.  


This paper presents the stoichiometry section of a bioenergetics investigation into the biogas plasticization of wastewater sludge using the Anaerobic Pump (TAP). Three residue samples, an input substrate and two residual products, were collected from two side by side operated AD systems, a conventional continuous flow and stirred reactor, and TAP, and submitted for elemental and calorimetric analyses. The elemental compositions of the residues were fitted to a heterotrophic metabolism model [1] for both systems. To facilitate balanced stoichiometric models, a simple "cell" correction computation separates measured residual composites into "real" residual composition and cell growth (C5H7NO2) components. The elemental data and model results show that the TAP stage II residual composition (C1H0.065O0.0027N0.036) was nearly devoid of hydrogen and oxygen, leaving only fixed carbon and cells grown as the composition of the remaining mass. This quantitative evidence supports prior measurements of very high methane yields from TAP stage II reactor during steady-state experiments [2]. All performance parameters derived from the stoichiometric model(s) showed good agreement with measured steady-state averaged values. These findings are strong evidence that plasticization-disruption (TAP) cycle is the mechanism responsible for the observed increases in methane yield. The accuracy achieved by the stoichiometry models qualifies them for thermodynamic analysis to obtain potentials and bioconversion efficiencies. How applied pressure causes matrix conformation changes triggered by a functional consequence (plasticization and disruption) is this study's essential focus. PMID:24347158

Schimel, Keith A



Improving thermophilic anaerobic digestion of swine manure  

Microsoft Academic Search

Thermophilic (55°C) anaerobic degradation of swine manure was found possible even at an ammonia content of 6g-N\\/l, with a low methane yield of only 67ml CH4\\/g-VS and a high concentration of volatile fatty acids (11.5g acetate\\/l). Several methods were tested in order to increase the methane yield. Addition of 1.5% (w\\/w) activated carbon, 10% (w\\/w) glauconite or 1.5% (w\\/w) activated

Kaare Hvid Hansen; Irini Angelidaki; Birgitte KiÆr Ahring



Cogeneration using methane from sewage treatment waste digester gas  

SciTech Connect

This paper describes the efforts undertaken at the Joint Meeting of Essex and Union Counties sewage treatment plant in Elizabeth, New Jersey, to generate electricity using the gas generated by anaerobic sludge digestion. The approach taken for the Joint Meeting Plant was to design a digester-gas-fired cogeneration system using internal combustion engines with waste heat recovery systems. This paper also describes the anaerobic sludge digestion process, waste gas characteristics, previous practices for disposal and use of waste gas, a discussion of why the selected cogeneration technology was chosen, and a discussion of the environmental effects and permitting requirements of the project. Finally, initial operating results of the cogeneration system are discussed.

Johnsen, H.L.; Greenway, A.R.



The effects of digestion temperature and temperature shock on the biogas yields from the mesophilic anaerobic digestion of swine manure  

Microsoft Academic Search

In order to obtain basic design criteria for anaerobic digesters of swine manure, the effects of different digesting temperatures, temperature shocks and feed loads, on the biogas yields and methane content were evaluated. The digester temperatures were set at 25, 30 and 35°C, with four feed loads of 5%, 10%, 20% and 40% (feed volume\\/digester volume). At a temperature of

K. J. Chae; Am Jang; S. K. Yim; In S. Kim



The action of antibiotics on the anaerobic digestion process  

Microsoft Academic Search

Antibiotics can disturb the production of biogas during anaerobic digestion. This study shows a systematic approach to understanding\\u000a how the different bacterial populations involved in the final conversion of organic matter into methane are inhibited by 15\\u000a antimicrobial agents with different specificities and modes of action. The results obtained show the following trends: (i)\\u000a some inhibitors, such as the macrolide

J. L. Sanz; N. Rodríguez; R. Amils



Anaerobic Digestion for Mitigation of Biodiesel Production Byproducts  

NSDL National Science Digital Library

The Advanced Technology Environmental and Energy Center (ATEEC) provides this document, which was part of a workshop held on anaerobic digestion for mitigation of biodiesel production byproducts. It would be useful for instructors looking to develop their own curriculum on biofuels and biodiesel byproducts. Users must download this resource for viewing, which requires a free log-in. There is no cost to download the item.


Cellulosic waste degradation by rumen-enhanced anaerobic digestion.  


Anaerobic digestion of lignocellulosic material is carried out effectively in many natural microbial ecosystems including the rumen. A rumen-enhanced anaerobic sequencing batch reactor was used to investigate cellulose degradation to give analysis of overall process stoichiometry and rates of hydrolysis. The reactor achieved VFA production rates of 207-236 mg COD/L/h at a loading rate of 10 g/L/d. Overloading of the reactor resulted in elevated production of propionic acid, and on occasion, the presence of succinic acid. With improvements in mixing and solids wasting, the anaerobic sequencing batch reactor system could enable full-scale application of the process for treatment of cellulosic waste material. PMID:14531434

Barnes, S P; Keller, J



Relating methanogen community structure and anaerobic digester function.  


Much remains unknown about the relationships between microbial community structure and anaerobic digester function. However, knowledge of links between community structure and function, such as specific methanogenic activity (SMA) and COD removal rate, are valuable to improve anaerobic bioprocesses. In this work, quantitative structure-activity relationships (QSARs) were developed using multiple linear regression (MLR) to predict SMA using methanogen community structure descriptors for 49 cultures. Community descriptors were DGGE demeaned standardized band intensities for amplicons of a methanogen functional gene (mcrA). First, predictive accuracy of MLR QSARs was assessed using cross validation with training (n = 30) and test sets (n = 19) for glucose and propionate SMA data. MLR equations correlating band intensities and SMA demonstrated good predictability for glucose (q(2) = 0.54) and propionate (q(2) = 0.53). Subsequently, data from all 49 cultures were used to develop QSARs to predict SMA values. Higher intensities of two bands were correlated with higher SMA values; high abundance of methanogens associated with these two bands should be encouraged to attain high SMA values. QSARs are helpful tools to identify key microorganisms or to study and improve many bioprocesses. Development of new, more robust QSARs is encouraged for anaerobic digestion or other bioprocesses, including nitrification, nitritation, denitrification, anaerobic ammonium oxidation, and enhanced biological phosphorus removal. PMID:25562581

Bocher, B T W; Cherukuri, K; Maki, J S; Johnson, M; Zitomer, D H



Biogasification of rice straw with an anaerobic-phased solids digester system  

Microsoft Academic Search

Rice straw was converted into biogas using a high-rate anaerobic digestion system, anaerobic-phased solids digester system (APS-digester system). The system was stable and, with proper design, could become a space-efficient, high-rate solids digestion system. Ammonia is used as a supplemental nitrogen source for rice straw digestion. The effects of different pretreatment methods, physical (mechanical), thermal and chemical (ammonia) treatment, on

Ruihong Zhang; Zhiqin Zhang



Temperature phased anaerobic digestion increases apparent hydrolysis rate for waste activated sludge  

Microsoft Academic Search

It is well established that waste activated sludge with an extended sludge age is inherently slow to degrade with a low extent of degradation. Pre-treatment methods can be used prior to anaerobic digestion to improve the efficiency of activated sludge digestion. Among these pre-treatment methods, temperature phased anaerobic digestion (TPAD) is one promising method with a relatively low energy input

Huoqing Ge; Paul D. Jensen; Damien J. Batstone



Department of Agricultural and Biological Engineering Fall 2011 Small Scale Anaerobic Digestion by PENERGY Solutions  

E-print Network

Digestion by PENERGY Solutions Overview For most farmers in Pennsylvania, the growing season ends by wood-fired boilers. By generating biogas through anaerobic digestion of swine manure, fuel can: A mechanical anaerobic digester to handle organic farm waste. A complete biogas collection system with hook

Demirel, Melik C.


The Effect of Enzyme Addition on Anaerobic Digestion of Jose Tall Wheat Grass  

Technology Transfer Automated Retrieval System (TEKTRAN)

The effects of the addition of enzyme products containing cellulase, hemicellulase, and Beta-glucosidase to anaerobic digestion systems were studied. Anaerobic digestion tests were performed using batch reactors operated at 35°C. The application of enzyme products in three digestion configurations w...


Impact of physical pre-treatment of source-sorted organic fraction of municipal solid waste on greenhouse-gas emissions and the economy in a Swedish anaerobic digestion system.  


Several methods for physical pre-treatments of source sorted organic fraction of municipal solid waste (SSOFMSW) before for anaerobic digestion (AD) are available, with the common feature that they generate a homogeneous slurry for AD and a dry refuse fraction for incineration. The selection of efficient methods relies on improved understanding of how the pre-treatment impacts on the separation and on the slurry's AD. The aim of this study was to evaluate the impact of the performance of physical pre-treatment of SSOFMSW on greenhouse-gas (GHG) emissions and on the economy of an AD system including a biogas plant with supplementary systems for heat and power production in Sweden. Based on the performance of selected Swedish facilities, as well as chemical analyses and BMP tests of slurry and refuse, the computer-based evaluation tool ORWARE was improved as to accurately describe mass flows through the physical pre-treatment and anaerobic degradation. The environmental and economic performance of the evaluated system was influenced by the TS concentration in the slurry, as well as the distribution of incoming solids between slurry and refuse. The focus to improve the efficiency of these systems should primarily be directed towards minimising the water addition in the pre-treatment provided that this slurry can still be efficiently digested. Second, the amount of refuse should be minimised, while keeping a good quality of the slurry. Electricity use/generation has high impact on GHG emissions and the results of the study are sensitive to assumptions of marginal electricity and of electricity use in the pre-treatment. PMID:25661691

Carlsson, My; Holmström, David; Bohn, Irene; Bisaillon, Mattias; Morgan-Sagastume, Fernando; Lagerkvist, Anders



Anaerobic digestion for treatment of stillage from cellulosic bioethanol production.  


Thermophilic anaerobic digestion of stillage from a cellulosic ethanol process that uses sugarcane bagasse as feedstock was investigated. A biochemical methane potential (BMP) of 200 ml CH4 at STP (g VS)(-1) was obtained. The whole stillage was separated into two fractions: a fraction retained on 0.5 mm screen called residue and a fraction passing through 0.5 mm screen called filtrate. About 70% of total methane yield of stillage was produced from the filtrate. The filtrate was anaerobically digested in a 15 L semi-continuously fed digester operated for 91 days at HRTs of 21 and 14 days and organic loading rate (OLR) of 1.85 and 2.39 g COD L(-1) d(-1). The methane yield from the stillage from the digester was about 90% of the yield from the BMP assays. The influent soluble COD (sCOD) was reduced from between 35.4 and 38.8 g COD (L(-1)) to between 7.5 and 8 g COD (L(-1)). PMID:23892147

Tian, Zhuoli; Mohan, Gayathri Ram; Ingram, Lonnie; Pullammanappallil, Pratap



Anaerobic digestion performance of vinegar residue in continuously stirred tank reactor.  


Anaerobic digestion (AD) of vinegar residue was investigated in continuously stirred tank reactor (CSTR). The influence of organic loading rate (OLR) and effluent recirculation on AD performance of vinegar residue was tested. Five OLRs, 1.0, 1.5, 2.0, 2.5, and 3.0gvsL(-1)d(-1), were used. The highest volumetric methane productivity of 581.88mLL(-1) was achieved at OLR of 2.5gvsL(-1)d(-1). Effluent reflux ratio was set as 50%, the results showed that effluent recirculation could effectively neutralize the acidity of vinegar residue, raise the pH of the feedstock, and enhance the buffering capacity of the AD system. Anaerobic digestion of vinegar residue could be a promising way not only for converting this waste into gas energy but also alleviating environmental pollution which might be useful for future industrial application. PMID:25838040

Li, Lin; Feng, Lu; Zhang, Ruihong; He, Yanfeng; Wang, Wen; Chen, Chang; Liu, Guangqing



Anaerobic digestion of cassava wastewater pre-treated by fungi.  


Cassava wastewater (cww) contains high concentrations of easily acidifying compounds, requiring a buffered system to allow a stable operation during anaerobic digestion (AD). The possibility to include a preliminary one-step fungi treatment aimed at raising the pH and buffering the cww prior to AD was studied. Preliminary tests were performed with a naturally grown fungal mixed culture, under aerated (AE), non-aerated (NAE) and initially oxygen-deprived (IOD) conditions. The cww was pre-treated by the NAE condition, until reaching a soluble chemical oxygen demand (COD) of 10 g?L(-1) and pH 6.4 (batch A) and pH 5.7 (batch B). The fungal mixed culture showed ability to biodegrade the cww with initial pH of 4.4 and 14,500 mg COD?L(-1), raising the pH over 8.5, with only 13 % of COD remaining within 27 days for both AE and NAE condition. The fungal pre-treated-cww (FPTcww) was subjected to anaerobic digestion under different buffered (CaCO3 and NaHCO3) and non-buffered conditions. The FPTcww with initial pH at 6.4 provided stability during the anaerobic biodegradability tests, showing the possibility of system operation without buffer addition, with final pH around 7. The application of a fungal pre-treatment can be a promising strategy to permit the anaerobic digestion of carbohydrate-rich wastewaters. PMID:23456279

Paulo, Paula Loureiro; Colman-Novaes, Thais Adriana; Obregão, Laynara Dayene Soares; Boncz, Marc Árpád



Growth and anaerobic digestion characteristics of microalgae cultivated using various types of sewage.  


Microalgal cultivation combined with anaerobic digestion at wastewater treatment plants is promising to recover energy. This study investigated the growth and anaerobic digestion characteristics of microalgae cultivated using nutrients in sewage. Microalgae were cultivated using primary effluent, secondary effluent, and dewatering filtrate. Microscopic observation indicated that Chlorella was cultivated using dewatering filtrate of anaerobic digestion without controlling the type of species. Batch anaerobic digestion experiments with digested sludge showed that the methane conversion ratio of the cultivated mixture was approximately 40-65%. Different cultivation time did not affect the microalgal contents. Methane recovery mass was 0.13NL-methane/L-cultivation liquor. The C/N ratio of the cultivated mixture was approximately 3-5, but the apparent ammonia release ratio was smaller than that of sewage sludge during digestion. These results proved the applicability of methane recovery from microalgae cultivated using nutrients included in anaerobically digested sludge. PMID:25127007

Hidaka, Taira; Inoue, Kenichiro; Suzuki, Yutaka; Tsumori, Jun



Digesters and demographics: identifying support for anaerobic digesters on dairy farms.  


The dairy industry in the United States is amidst a long-running trend toward fewer, larger dairy farms. This development has created a backlash in some communities over concerns such as odor, waste management, and environmental degradation. Separately, anaerobic digestion has advanced as a waste management technology that potentially offers solutions to some of these issues, providing odor control and a combustible biogas among other things. These digesters require significant capital investments. Voluntary consumer premiums for the renewable energy produced have been used in some instances as a means to move adoption of such systems toward financial feasibility. This project employed a survey to measure Ohio consumers' willingness to pay a premium for renewable energy produced by anaerobic digesters on dairy farms. Cluster analysis was used to segment consumers by willingness to pay, age, education, income, self-identified political inclination, and a composite variable that served as a proxy for respondents' environmental stewardship. Four distinctive groups emerged from the data. Older, less educated respondents were found to have the least amount of support for digesters on dairy farms, whereas politically liberal, environmentally proactive respondents demonstrated the strongest support. Well-educated, affluent respondents and young respondents fell between these 2 groups. Most large dairy farms are generally met with fairly negative responses from their local communities; in contrast, this research finds some popular support for anaerobic digestion technology. Going forward, establishing a positive link between support for anaerobic digesters and for their use on large dairies could open up a new route for less-contested large dairy farm developments. Evaluation of community demographics could become an important part of finding an optimal location for a large dairy farm. PMID:20965366

Sanders, D J; Roberts, M C; Ernst, S C; Thraen, C S



Optimizing the logistics of anaerobic digestion of manure.  


Electrical power production from the combustion of biogas from anaerobic digestion (AD) of manure is a means of recovering energy from animal waste. We evaluate the lowest cost method of moving material to and from centralized AD plants serving multiple confined feeding operations. Two areas are modeled, Lethbridge County, Alberta, Canada, an area of concentrated beef cattle feedlots, and Red Deer County, Alberta, a mixed-farming area with hog, dairy, chicken and beef cattle farms, and feedlots. We evaluate two types of AD plant: ones that return digestate to the source confined feeding operation for land spreading (current technology), and ones that process digestate to produce solid fertilizer and a dischargeable water stream (technology under development). We evaluate manure and digestate trucking, trucking of manure with return of digestate by pipelines, and pipelining of manure plus digestate. We compare the overall cost of power from these scenarios to farm or feedlot-based AD units. For a centralized AD plant with digestate return for land spreading the most economical transport option for manure plus digestate is by truck for the mixed-farming area and by pipelines for the concentrated feedlot area. For a centralized AD plant with digestate processing, the most economical transport option is trucking of manure for both cases.However, for the concentrated feedlot area, pipeline transport of manure is close in cost to trucking, and the impact of truck congestion would likely lead to selection of pipeline transport. For the mixed-farming area, centralized AD is more economical than for any individual farm or feedlot unit. For the concentrated feedlot area, a centralized AD plant is less economical than a feedlot-based AD unit more than 55,000 head (digestate return) and 300,000 head (digestate processing). The study demonstrates the viability of centralized AD plants vs farm-based units in most farming environments, and that careful analysis of the cost of pipeline vs truck transport of manure and digestate is required on a case-by-case basis. PMID:18478421

Ghafoori, Emad; Flynn, Peter C



Microbial Ecology of Anaerobic Digesters: The Key Players of Anaerobiosis  

PubMed Central

Anaerobic digestion is the method of wastes treatment aimed at a reduction of their hazardous effects on the biosphere. The mutualistic behavior of various anaerobic microorganisms results in the decomposition of complex organic substances into simple, chemically stabilized compounds, mainly methane and CO2. The conversions of complex organic compounds to CH4 and CO2 are possible due to the cooperation of four different groups of microorganisms, that is, fermentative, syntrophic, acetogenic, and methanogenic bacteria. Microbes adopt various pathways to evade from the unfavorable conditions in the anaerobic digester like competition between sulfate reducing bacteria (SRB) and methane forming bacteria for the same substrate. Methanosarcina are able to use both acetoclastic and hydrogenotrophic pathways for methane production. This review highlights the cellulosic microorganisms, structure of cellulose, inoculum to substrate ratio, and source of inoculum and its effect on methanogenesis. The molecular techniques such as DGGE (denaturing gradient gel electrophoresis) utilized for dynamic changes in microbial communities and FISH (fluorescent in situ hybridization) that deal with taxonomy and interaction and distribution of tropic groups used are also discussed. PMID:24701142

Ali Shah, Fayyaz; Mahmood, Qaisar; Maroof Shah, Mohammad; Pervez, Arshid; Ahmad Asad, Saeed



Ultrasound pre-treatment for anaerobic digestion improvement.  


Prior research indicates that ultrasounds can be used in batch reactors as pre-treatment before anaerobic digestion, but the specific energy required at laboratory-scale is too high. This work evaluates both the continuous ultrasound device performance (efficiency and solubilisation) and the operation of anaerobic digesters continuously fed with sonicated sludge, and presents energy balance considerations. The results of sludge solubilisation after the sonication treatment indicate that, applying identical specific energy, it is better to increase the power than the residence time. Working with secondary sludge, batch biodegradability tests show that by applying 30 kWh/m3 of sludge, it is possible to increase biogas production by 42%. Data from continuous pilot-scale anaerobic reactors (V=100 L) indicate that operating with a conventional HRT=20 d, a reactor fed with pre-treated sludge increases the volatile solids removal and the biogas production by 25 and 37% respectively. Operating with HRT=15 d, the removal efficiency is similar to the obtained with a reactor fed with non-hydrolysed sludge at HTR=20 d, although the specific biogas productivity per volume of reactor is higher for the pretreated sludge. Regarding the energy balance, although for laboratory-scale devices it is negative, full-scale suppliers state a net generation of 3-10 kW per kW of energy used. PMID:19759455

Pérez-Elvira, S; Fdz-Polanco, M; Plaza, F I; Garralón, G; Fdz-Polanco, F



Optimization of solid state anaerobic digestion of the OFMSW by digestate recirculation: A new approach.  


Dry anaerobic digestion (AD) of OFMSW was optimized in order to produce biogas avoiding the use of solid inoculum. Doing so the dry AD was performed irrigating the solid waste with liquid digestate (flow rate of 1:1.18-1:0.9 w/w waste/digestate; 21d of hydraulic retention time - HRT) in order to remove fermentation products inhibiting AD process. Results indicated that a high hydrolysis rate of organic matter (OM) and partial biogas production were obtained directly during the dry AD. Hydrolysate OM was removed from digester by the percolate flow and it was subsequently used to feed a liquid anaerobic digester. During dry AD a total loss of 36.9% of total solids was recorded. Methane balance indicated that 18.4% of potential methane can be produced during dry AD and 49.7% by the percolate. Nevertheless results obtained for liquid AD digestion indicated that only 20.4% and 25.7% of potential producible methane was generated by adopting 15 and 20 days of HRT, probably due to the AD inhibition due to high presence of toxic ammonia forms in the liquid medium. PMID:25305682

Michele, Pognani; Giuliana, D'Imporzano; Carlo, Minetti; Sergio, Scotti; Fabrizio, Adani



Psychrophilic anaerobic digestion biotechnology for swine mortality disposal.  


The objective of this study was to investigate the feasibility of using psychrophilic anaerobic digestion in sequencing batch reactors (PADSBRs) to co-digest grinded swine carcasses and swine manure slurry at 20 degrees C and 25 degrees C. The PADSBRs were operated on two-week and four-week treatment cycle lengths, which included the fill, react, and draw phases. Two carcass loading rates (CLRs) were tested, that is 20 and 40g of carcass per litre of manure, which were equivalent to 4 and 8 times, respectively, the normal mortality rate on commercial farms. The PADSBR performance was compared to that of PADSBRs operated at 25 degrees C and fed manure only. The addition of swine carcass to PADSBR feed did not affect the stability of the bioreactors at both CLRs. The performance of the PADSBRs co-digesting swine carcasses was not statistically different from the control in terms of biogas production and quality. There was no accumulation of volatile fatty acids in the bioreactors at the end of the treatment cycle. The mixed-liquor pH and alkalinity remained within acceptable ranges for the anaerobic microflora. Also, there was no operational problem caused by the formation of foam and scum in the system. PMID:18325763

Massé, D I; Masse, L; Hince, J F; Pomar, C



Cogeneration with digester gas  

Microsoft Academic Search

The current electrical power demands at the County Sanitation Districts of Los Angeles County Joint Water Pollution Control Plant (JWPCP) will triple with the addition of Federally mandated secondary treatment facilities. The paper describes the power demands and the proposed cogeneration facilities. In light of the stringent California air emission rules and economic considerations, combined cycle turbines, using pretreated digester

J. D. Eppich; G. M. Adams; W. E. Garrison; J. C. Gratteau



Feasibility and strategies for anaerobic digestion of solid waste for energy production in Dar es Salaam city, Tanzania  

Microsoft Academic Search

In Tanzania, the most serious solid waste management problem currently is disposal, but since the largest fraction of the waste is organics which are amenable to anaerobic digestion and composting, it makes environmental and economic sense to explore these options. This prompted the conception of the Taka (waste) Gas Project which is meant to utilise organic solid waste from Dar

Stephen E Mbuligwe; Gabriel R Kassenga



Psychrophilic anaerobic digestion of guinea pig manure in low-cost tubular digesters at high altitude.  


Guinea pig is one of the most common livestock in rural communities of the Andes. The aim of this research was to study the anaerobic digestion of guinea pig manure in low-cost unheated tubular digesters at high altitude. To this end, the performance of two pilot digesters was monitored during 7 months; and two greenhouse designs were compared. In the dome roof digester the temperature and biogas production were significantly higher than in the shed roof digester. However, the biogas production rate was low (0.04 m(biogas)(3)m(digester)(-3) d(-1)), which is attributed to the low organic loading rate (0.6 kg(VS)m(digester)(-3)d(-1)) and temperature (23°C) of the system, among other factors. In a preliminary fertilization study, the potato yield per hectare was increased by 100% using the effluent as biofertilizer. Improving manure management techniques, increasing the organic loading rate and co digesting other substrates may be considered to enhance the process. PMID:21450457

Garfí, Marianna; Ferrer-Martí, Laia; Villegas, Vidal; Ferrer, Ivet



Evaluation of an electronic nose for the early detection of organic overload of anaerobic digesters.  


This study aimed at analysing the utilization of an electronic nose (e-nose) to serve as a specific monitoring tool for anaerobic digestion process, especially for detecting organic overload. An array of non specific metal oxide semiconductor gas sensors were used to detect process faults due to organic overload events in twelve 1.8-L anaerobic semi-continuous reactors. Three different load strategies were followed: (1) a cautious organic load (1.3 gVS L(-1) day(-1)); (2) an increasing load strategy (1.3-5.3 gVS L(-1) day(-1)) and (3) a cautious organic load with load pulses of up to 12 gVS L(-1) day(-1). A first monitoring campaign was conducted with three different substrates: sucrose, maize oil and a mix of sucrose/oil during 60 days. The second campaign was run with dry sugar beet pulp for 45 days. Hotelling's T(2) value and upper control limit to a reference set of digesters fed with a cautious OLR (1.3 gVS L(-1) day(-1)) was used as indirect state variable of the reactors. Overload situations were identified by the e-nose apparatus with Hotelling's T(2) values at least four times higher in magnitude than the upper control limit of 23.7. These results confirmed that the e-nose technology appeared promising for online detection of process imbalances in the domain of anaerobic digestion. PMID:22644064

Adam, Gilles; Lemaigre, Sébastien; Romain, Anne-Claude; Nicolas, Jacques; Delfosse, Philippe



The role of anaerobic sludge recycle in improving anaerobic digester performance.  


Solids retention time (SRT) is a critical parameter for the performance of anaerobic digesters (AD) in wastewater treatment plants. AD SRT should increase when active biomass is input to the AD by recycling anaerobic sludge via the wastewater-treatment tanks, creating a hybrid aerobic/anaerobic system. When 85% of the flow through the AD was recycled in pilot-scale hybrid systems, the AD SRT increased by as much as 9-fold, compared to a parallel system without anaerobic-sludge recycle. Longer AD SRTs resulted in increased hydrolysis and methanogenesis in the AD: net solids yield decreased by 39-96% for overall and 23-94% in the AD alone, and AD methane yield increased 1.5- to 5.5-fold. Microbial community assays demonstrated higher, more consistent Archaea concentrations in all tanks in the wastewater-treatment system with anaerobic-sludge recycle. Thus, multiple lines of evidence support that AD-sludge recycle increased AD SRT, solids hydrolysis, and methane generation. PMID:23265819

Young, Michelle N; Krajmalnik-Brown, Rosa; Liu, Wenjun; Doyle, Michael L; Rittmann, Bruce E



Intermediate-Scale High-Solids Anaerobic Digestion System Operational Development  

SciTech Connect

Anaerobic bioconversion of solid organic wastes represents a disposal option in which two useful products may be produced, including a medium Btu fuel gas (biogas) and a compost-quality organic residue. The application of high-solids technology may offer several advantages over conventional low-solids digester technology. The National Renewable Energy Laboratory (NREL) has developed a unique digester system capable of uniformly mixing high-solids materials at low cost. During the first 1.5 years of operation, a variety of modifications and improvements were instituted to increase the safety, reliability, and performance of the system. Those improvements, which may be critical in further scale-up efforts using ,the NREL high-solids digester design are detailed in this report.

Rivard, C. J.




SciTech Connect

GEW has been operating the first fuel cell in Europe producing heat and electricity from digester gas in an environmentally friendly way. The first 9,000 hours in operation were successfully concluded in August 2001. The fuel cell powered by digester gas was one of the 25 registered ''Worldwide projects'' which NRW presented at the EXPO 2000. In addition to this, it is a key project of the NRW State Initiative on Future Energies. All of the activities planned for the first year of operation were successfully completed: installing and putting the plant into operation, the transition to permanent operation as well as extended monitoring till May 2001.

Dr.-Eng. Dirk Adolph; Dipl.-Eng. Thomas Saure



Investigation of Poultry Waste for Anaerobic Digestion: A Case Study  

NASA Astrophysics Data System (ADS)

Anaerobic Digestion (AD) is a biological conversion technology which is being used to produce bioenergy all over the world. This energy is created from biological feedstocks, and can often use waste products from various food and agricultural processors. Biogas from AD can be used as a fuel for heating or for co-generation of electricity and heat and is a renewable substitute to using fossil fuels. Nutrient recycling and waste reduction are additional benefits, creating a final product that can be used as a fertilizer in addition to energy benefits. This project was conducted to investigate the viability of three turkey production wastes as AD feedstock: two turkey litters and a material separated from the turkey processing wastewater using dissolved air flotation (DAF) process. The DAF waste contained greases, oils and other non-commodity portions of the turkey. Using a variety of different process methods, types of bacteria, loading rates and food-to-microorganism ratios, optimal loading rates for the digestion of these three materials were obtained. In addition, the co-digestion of these materials revealed additional energy benefits. In this study, batch digestion tests were carried out to treat these three feedstocks, using mesophilic and thermophilic bacteria, using loading rates of 3 and 6 gVS/L They were tested separately and also as a mixture for co-digestion. The batch reactor used in this study had total and working volumes of 1130 mL and 500 mL, respectively. The initial organic loading was set to be 3 gVS/L, and the food to microorganism ratio was either 0.6 or 1.0 for different treatments based on the characteristics of each material. Only thermophilic (50 +/- 2ºC) temperatures were tested for the litter and DAF wastes in continuous digestion, but mesophilic and thermophilic batch digestion experiments were conducted. The optimum digestion time for all experiments was 14 days. The biogas yields of top litter, mixed litter, and DAF waste under mesophilic batch conditions all at 3 gVS/L loading were determined to be 148.6 +/- 7.82, 176.5 +/- 11.1 and 542.0 +/- 37.9 mL/ gVS, respectively and were 201.9 +/- 10.0, 210.4 +/- 29.3, and 419.3 +/- 12.1 mL/gVS, respectively, for initial loading of 6 gVS/L. Under thermophilic batch conditions, the top litter, mixed litter, and DAF waste had the biogas yields of 255.3 +/- 7.9, 313.4 +/- 30.1and 297.4 +/- 33.8 mL/gVS for loading rate of 3 gVS/L and 233.8 +/- 45.3, 306.5 +/- 11.8 and 185.1 +/- 0.85 mL/gVS for loading rate of 6 gVS/L. The biogas yields from co-digestion of the mixed litter and DAF waste at 3 gVS/L were 461.8 +/- 41.3 mL/gVS under thermophilic conditions. The results from batch anaerobic digestion tests were then used for designing continuous digestion experiments. All the continuous digestion experiments were conducted by using an Anaerobic Phase Solids (APS) digester system operated at a thermophilic temperature. The total volume of the continuous digester system was 4.8 L and the working volume was around 4.4 L. The APS digester system had two hydrolysis reactors and one biogasification reactor. Feedstock was loaded into the hydrolysis reactors in batches. The feedstock digestion time was 14 days and the average organic loading rate (OLR) of the system was 3 gVS/L/day. The experiment has three distinct feedstock stages, first with turkey litter waste, a co-digestion of DAF and turkey litter waste, followed by DAF waste. The biogas yields were determined to be 305.2 +/- 70.6 mL/gVS/d for turkey mixed litter, 455.8 +/- 77.2 mL/gVS/d during the mixture of mixed litter and DAF waste, and 382.0 +/- 39.6 mL/gVS for DAF waste. The biogas yields from the thermophilic batch test yields compare with that of the continuous digester yields. For experiments utilizing turkey litter, batch tests yielded 313.4 +/- 30.1mL/gVS biogas and 305.2 +/- 70.6 mL/gVS/d for continuous experiments. For experiments using codigestion of turkey litter and DAF waste, batches yielded 461.8 +/- 41.3 mL/gVS biogas comparing well to continuous digester operation that yielded 455.8 +/- 77.

Salam, Christopher R.


Household anaerobic digester for bioenergy production in developing countries: opportunities and challenges.  


Access to clean and affordable energy is vital for advancing development objectives, particularly in rural areas of developing countries. There are some three billion people in these regions, however, who lack consistent access to energy and rely on traditional solid fuels such as firewood, cattle manure, and crop residues for meeting cooking and heating needs. Excessive use of such highly polluting resources creates serious environmental, social and public health issues. In this context, household digesters (which convert readily available feedstocks such as cattle manure, human excreta, and crop residues into biogas) have the potential to play a significant role in supplying methane as a clean, renewable energy resource for remote geographies. In addition to bioenergy production, the slurry generated from anaerobic digestion is rich in nutrients and can improve the physical, chemical, and biological attributes of soil when applied to agricultural land. This type of approach has the potential to significantly reduce greenhouse gas emissions while simultaneously improving the quality of life. Despite a long history of research and innovation for the development and optimization of household digesters, little is known and has been reported for the application of these systems in decentralized communities. The primary purpose of this paper seeks to review the dearth of literature pertaining to small-scale anaerobic digesters in remote geographies and in regions where much of the world's population reside. PMID:24350427

Surendra, K C; Takara, Devin; Jasinski, Jonas; Khanal, Samir Kumar



The fate of crop nutrients during digestion of swine manure in psychrophilic anaerobic sequencing batch reactors  

Microsoft Academic Search

The objectives of the study were to measure the levels of manure nutrients retained in psychrophilic anaerobic sequencing batch reactors (PASBRs) digesting swine manure, and to determine the distribution of nutrients in the sludge and supernatant zones of settled bioreactor effluent. Anaerobic digestion reduced the total solids (TS) concentration and the soluble chemical oxygen demand (SCOD) of manure by 71.4%

D. I. Massé; F. Croteau; L. Masse



Evaluation of biogas production by dry anaerobic digestion of switchgrass-animal manure mixtures  

Technology Transfer Automated Retrieval System (TEKTRAN)

Anaerobic digestion is a biological method used to convert organic wastes into a stable product for land application without adverse environmental effects. The biogas produced can be used as an alternative renewable energy source. Dry anaerobic digestion (> 15% TS; total solid) has an advantage ov...


Aeration of anaerobically digested sewage sludge for COD and nitrogen removal: optimization at large-scale  

Microsoft Academic Search

The paper will report about the experiences matured at an Austrian large wastewater treatment plant of 720.000 population equivalents, where anaerobically digested sewage sludge is further stabilised under aerobic conditions. Enhanced stabilisation of the anaerobically digested sludge was required at the plant in order to get a permit for landfill disposal of the dewatered stabilized sludge. By implementing a post-aeration

V. Parravicini; K. Svardal; R. Hornek; H. Kroiss



Anaerobic Co-digestion of Brown Water and Food Waste for Energy Recovery  

E-print Network

LIM J.W. Anaerobic Co-digestion of Brown Water and Food Waste for Energy Recovery Jun Wei LIM plants for treatment, which consumes too much unnecessary energy and water. An alternative approach would, Singapore 639798 (E-mail: Abstract The anaerobic digestion of brown water (BW), food

Paris-Sud XI, Université de


Repeated pulse feeding induces functional stability in anaerobic digestion  

PubMed Central

Summary Anaerobic digestion is an environmental key technology in the future bio-based economy. To achieve functional stability, a minimal microbial community diversity is required. This microbial community should also have a certain ‘elasticity’, i.e. the ability to rapidly adapt to suboptimal conditions or stress. In this study it was evaluated whether a higher degree of functional stability could be achieved by changing the feeding pattern, which can change the evenness, dynamics and richness of the bacterial community. The first reactor (CSTRstable) was fed on daily basis, whereas the second reactor (CSTRdynamic) was fed every 2 days. Average biogas production was 0.30?l CH4 l?1 day?1 in both reactors, although daily variation was up to four times higher in the CSTRdynamic compared with the CSTRstable during the first 50 days. Bacterial analysis revealed that this CSTRdynamic had a two times higher degree of bacterial community dynamics. The CSTRdynamic also appeared to be more tolerant to an organic shock load of 8?g COD l?1 and ammonium levels up to 8000?mg TAN l?1. These results suggest that the regular application of a limited pulse of organic material and/or a variation in the substrate composition might promote higher functional stability in anaerobic digestion. PMID:23302421

De Vrieze, Jo; Verstraete, Willy; Boon, Nico



Integration of pyrolysis and anaerobic digestion - Use of aqueous liquor from digestate pyrolysis for biogas production.  


Anaerobic digestion of aqueous pyrolysis liquor derived from pyrolysis of solid digestate was tested in batch mode using an un-adapted inoculum. Three pyrolysis liquors produced at 330°C, 430°C and 530°C in four COD-based concentrations of 3, 6, 12 and 30gL(-1) were investigated. The three lower concentrations showed considerable biogas production, whereas the 30gL(-1) dosage caused process inhibition. The highest methane yield of 199.1±18.5mLgCOD(-1) (COD removal: 56.9±5.3%) was observed for the 330°C pyrolysis liquor, followed by the 430°C sample with only slightly lower values. The 530°C sample dropped to a yield of 129.3±19.7mLgCOD(-1) (COD removal: 36.9±5.6%). Most VOCs contained in the pyrolysis liquor (i.e. furfural, phenol, catechol, guaiacol, and levoglucosan) were reduced below detection limit (cresol by 10-60%). Consequently, integrated pyrolysis and anaerobic digestion in addition to thermochemical conversion of digestate also promises bioconversion of pyrolysis liquors. PMID:25725406

Hübner, Tobias; Mumme, Jan



Survival rates of parasite eggs in sludge during aerobic and anaerobic digestion.  

PubMed Central

The effects of mesothermic anaerobic or aerobic sludge digestion on survival of eggs from the roundworms Ascaris suum, toxocara canis, Trichuris vulpis, and Trichuris suis and from the rat tapeworm Hymenolepis diminuta were studied. Destruction of eggs throughout a 15-day treatment period, as well as their viabilities after reisolation, was analyzed. The laboratory model digesters used in this study were maintained at a 15-day retention schedule, partially simulating a continuously operating system. Ascaris eggs were destroyed in the anaerobic (23%) or aerobic (38%) digesters, and 11% Trichuris eggs were destroyed in the aerobic digesters. Trichuris eggs in anaerobic digesters and Toxocara eggs in either anaerobic or aerobic digesters were not destroyed. Destruction of eggs in digesters was correlated with the state of the eggs before subjection to the treatment processes; i.e., some Ascaris and Trichuris eggs were already embryonated in host intestinal contents or feces and hence past their most resistant stage. The viabilities of Ascaris and Toxocara eggs that survived the digestion processes were greater in anaerobically treated than in aerobically treated material. Eggs from Hymenolepis were nonviable before use in the experiments. However, they were more effectively destroyed in aerobic digesters than in anaerobic digesters. PMID:6891199

Black, M I; Scarpino, P V; O'Donnell, C J; Meyer, K B; Jones, J V; Kaneshiro, E S



Biogas energy production from tropical biomass wastes by anaerobic digestion.  


Anaerobic digestion (AD) is an attractive technology in tropical regions for converting locally abundant biomass wastes into biogas which can be used to produce heat, electricity, and transportation fuels. However, investigations on AD of tropical forestry wastes, such as albizia biomass and food wastes, such as taro, papaya, and sweet potato, are limited. In this study, these tropical biomass wastes were evaluated for biogas production by liquid AD (L-AD) and/or solid-state AD (SS-AD), depending on feedstock characteristics. When albizia leaves and chips were used as feedstocks, L-AD had greater methane yields (161 and 113 L kg(-1)VS, respectively) than SS-AD (156.8 and 59.6 L kg(-1)VS, respectively), while SS-AD achieved 5-fold higher volumetric methane productivity than L-AD. Mono-digestion and co-digestion of taro skin, taro flesh, papaya, and sweet potato achieved methane yields from 345 to 411 L kg(-1)VS, indicating the robustness of AD technology. PMID:25022835

Ge, Xumeng; Matsumoto, Tracie; Keith, Lisa; Li, Yebo



Evaluation of Biogas Production Potential by Dry Anaerobic Digestion of Switchgrass–Animal Manure Mixtures  

Microsoft Academic Search

Anaerobic digestion is a biological method used to convert organic wastes into a stable product for land application with\\u000a reduced environmental impacts. The biogas produced can be used as an alternative renewable energy source. Dry anaerobic digestion\\u000a [>15% total solid (TS)] has an advantage over wet digestion (<10% TS) because it allows for the use of a smaller volume of

H. K. Ahn; M. C. Smith; S. L. Kondrad; J. W. White



Anaerobic digestion of organic solid wastes. An overview of research achievements and perspectives  

Microsoft Academic Search

The technology of anaerobic digestion of organic solid wastes is, in many aspects, mature. Topics such as fundamentals (kinetics, modelling, etc.), process aspects (performance, two- and single-phase systems, wet and dry technologies), digestion enhancement (several pre-treatments), co-digestion with other substrates and its relation to composting technology are examined in this review. Special attention is paid to the advantages of anaerobic

J Mata-Alvarez; S Macé; P Llabrés



Microalgae to biofuels: life cycle impacts of methane production of anaerobically digested lipid extracted algae.  


This study presents experimental measurements of the biochemical methane production for whole and lipid extracted Nannochloropsis salina. Results show whole microalgae produced 430 cm(3)-CH4 g-volatile solids(-1) (g-VS) (?=60), 3 times more methane than was produced by the LEA, 140 cm(3)-CH4 g-VS(-1) (?=30). Results illustrate current anaerobic modeling efforts in microalgae to biofuel assessments are not reflecting the impact of lipid removal. On a systems level, the overestimation of methane production is shown to positively skew the environmental impact of the microalgae to biofuels process. Discussion focuses on a comparison results to those of previous anaerobic digestion studies and quantifies the corresponding change in greenhouse gas emissions of the microalgae to biofuels process based on results from this study. PMID:25181698

Quinn, Jason C; Hanif, Asma; Sharvelle, Sybil; Bradley, Thomas H



Anaerobic digestion of autoclaved and untreated food waste  

SciTech Connect

Highlights: • Autoclaving decreased the formation of NH4-N and H{sub 2}S during food waste digestion. • Stable digestion was achieved with untreated and autoclaved FW at OLR 6 kg VS/m{sup 3}day. • Use of acclimated inoculum allowed very rapid increases in OLR. • Highest CH{sub 4} yields were observed at OLR 3 kg VS/m{sup 3}day with untreated FW. • Autoclaved FW produced highest CH{sub 4} yields during OLR 4 kgVS/m{sup 3}day. - Abstract: Anaerobic digestion of autoclaved (160 °C, 6.2 bar) and untreated source segregated food waste (FW) was compared over 473 days in semi-continuously fed mesophilic reactors with trace elements supplementation, at organic loading rates (OLRs) of 2, 3, 4 and 6 kg volatile solids (VS)/m{sup 3} d. Methane yields at all OLR were 5–10% higher for untreated FW (maximum 0.483 ± 0.013 m{sup 3} CH{sub 4}/kg VS at 3 kg VS/m{sup 3} d) than autoclaved FW (maximum 0.439 ± 0.020 m{sup 3} CH{sub 4}/kg VS at 4 kg VS/m{sup 3} d). The residual methane potential of both digestates at all OLRs was less than 0.110 m{sup 3} CH{sub 4}/kg VS, indicating efficient methanation in all cases. Use of acclimated inoculum allowed very rapid increases in OLR. Reactors fed on autoclaved FW showed lower ammonium and hydrogen sulphide concentrations, probably due to reduced protein hydrolysis as a result of formation of Maillard compounds. In the current study this reduced biodegradability appears to outweigh any benefit due to thermal hydrolysis of ligno-cellulosic components.

Tampio, Elina, E-mail: [Bioenergy and Environment, MTT Agrifood Research Finland, FI-31600 Jokioinen (Finland); Ervasti, Satu; Paavola, Teija [Bioenergy and Environment, MTT Agrifood Research Finland, FI-31600 Jokioinen (Finland); Heaven, Sonia; Banks, Charles [University of Southampton, Faculty of Engineering and the Environment, Southampton SO17 1BJ (United Kingdom); Rintala, Jukka [Bioenergy and Environment, MTT Agrifood Research Finland, FI-31600 Jokioinen (Finland)



Data summary of municipal solid waste management alternatives. Volume 10, Appendix H: Anaerobic digestion of MSW  

SciTech Connect

While municipal solid waste (MSW) thermoconversion and recycling technologies have been described in Appendices A through E, this appendix addresses the role of bioconversion technologies in handling the organic fraction in MSW and sewage sludge. Much of the organic matter in MSW, consisting mainly of paper, food waste, and yard waste, has potential for conversion, along with sewage sludge, through biochemical processes to methane and carbon dioxide providing a measurable, renewable energy resource potential. The gas produced may be treated for removal of carbon dioxide and water, leaving pipeline quality gas. The process also has the potential for producing a stabilized solid product that may be suitable as a fuel for combustion or used as a compost fertilizer. Anaerobic digestion can occur naturally in an uncontrolled environment such as a landfill, or it can occur in a controlled environment such as a confined vessel. Landfill gas production is discussed in Appendix F. This appendix provides information on the anaerobic digestion process as it has been applied to produce methane from the organic fraction of MSW in enclosed, controlled reactors.




Solubilization of particulate organic carbon during the acid phase of anaerobic digestion  

Microsoft Academic Search

Hydrolysis of particulates to soluble substrates rather than bacterial growth was the rate-limiting step during the acid phase of anaerobic digestion of sewage sludge, and pH had a greater effect on the process than did influent solids concentrations, suggesting that digestability can be improved for highly variable feed sludges by separate phase digestion for acid production and CHâ production. Carbohydrates

J. A. Eastman; J. F. Ferguson



Anaerobic digestion of municipal wastewater sludges using anaerobic fluidized bed bioreactor.  


The anaerobic digestion of primary sludge (PS) and thickened waste activated sludge (TWAS) using an anaerobic fluidized bed bioreactor (AnFBR) employing zeolite particles as the carrier media was investigated at different organic loading rates (OLRs). PS was tested at OLRs from 4.2 to 39kgCOD/m(3)-d corresponding to hydraulic retention times (HRTs) from 1.0 to 8.9days. The highest COD removal and VSS destruction efficiencies for primary sludge of 85% and 88%, respectively, were achieved at an HRT of 8.9days and OLR of 4.2kgCOD/m(3)-d. For TWAS, VSS destruction efficiencies varied from 42% at an HRT of 2.6days and OLR of 13.1kgCOD/m(3)-d to 69% at an HRT of 8.8days and an OLR of 4.2kgCOD/m(3)-d. The first-order COD biodegradation rates in the AnFBR for PS and TWAS were 0.4d(-1) and 0.1d(-1), respectively, almost double the rates in conventional high-rate digesters. PMID:25280599

Mustafa, Nizar; Elbeshbishy, Elsayed; Nakhla, George; Zhu, Jesse



Microbial kinetic for In-Storage-Psychrophilic Anaerobic Digestion (ISPAD).  


In-Storage-Psychrophilic-Anaerobic-Digestion (ISPAD) is a wastewater storage tank converted into an anaerobic digestion (AD) system by means of an airtight floating geo-membrane. For process optimization, ISPAD requires modelling with well-established microbial kinetics coefficients. The present objectives were to: obtain kinetics coefficients for the modelling of ISPAD; compare the prediction of the conventional and decomposition fitting approach, an innovative fitting technique used in other fields of science, and; obtain equations to predict the maximum growth rate (?max) of microbial communities as a function of temperature. The method consisted in conducting specific Substrate Activity Tests (SAT) using ISPAD inoculum to monitor the rate of degradation of specific substrates at 8, 18 and 35 °C. Microbial kinetics coefficients were obtained by fitting the Monod equations to SAT. The statistical procedure of Least Square Error analysis was used to minimize the Sum of Squared Errors (SSE) between the measured ISPAD experimental data and the Monod equation values. Comparing both fitting methods, the decomposition approach gave higher correlation coefficient (R) for most kinetics values, as compared to the conventional approach. Tested to predict ?max with temperature, the Square Root equation better predicted temperature dependency of both acidogens and propionate degrading acetogens, while the Arrhenius equation better predicted that of methanogens and butyrate degrading acetogens. Increasing temperature from 18 to 35 °C did not affect butyrate degrading acetogens, likely because of their dominance, as demonstrated by microbial population estimation. The estimated ISPAD kinetics coefficients suggest a robust psychrophilic and mesophilic coexisting microbial community demonstrating acclimation to ambient temperature. PMID:25156266

Madani-Hosseini, Mahsa; Mulligan, Catherine N; Barrington, Suzelle



Investigation of Non-Newtonian Flow in Anaerobic Digesters  

NASA Astrophysics Data System (ADS)

This thesis examines how the non-Newtonian characteristics of liquid hog manure affect the flow conditions within a steady-flow anaerobic digester. There are three main parts to this thesis. In the first part of this thesis, the physical properties of liquid hog manure and their variation with temperature and solids concentration are experimentally determined. Naturally-settled manure sampled from an outdoor storage lagoon is studied, and density, viscosity, and particle size distribution are measured. Hog manure with total solids concentrations of less than 3.6% exhibits Newtonian behaviour; manure between 3.6% and 6.5% total solids is pseudoplastic, and fits the power law; manure with more than 6.5% total solids exhibits non-Newtonian and time-dependent characteristics. The second part of this thesis investigates the flow of Newtonian and non-Newtonian fluids---represented by tap water and xanthan gum solution, respectively---within four lab-scale reactor geometries, using residence time distribution (RTD) experiments. The effect of reactor geometry, flow rate, and fluid viscosity are evaluated. In the third part of this thesis, flow conditions within lab-scale and pilot-scale anaerobic digester reactors are simulated using three-dimensional modeling techniques. The RTDs of lab-scale reactors as predicted by the 3D numerical models compare well to the experimental results. The 3D models are also validated using data from particle image velocimetry (PIV) experiments. Finally, the viscous properties of liquid hog manure at 3% and 8% total solids are incorporated into the models, and the results are evaluated.

Langner, Jeremy M.


Thermophilic anaerobic digestion of sewage sludge with high solids content.  


The treatment performance of thermophilic anaerobic digestion (AD) of sewage sludge with high solids content was investigated with two laboratory-scale thermophilic anaerobic reactors (R1 and R2) with a feeding of pre-centrifuged sewage sludge. Reactor R1 was fed with sludge of 3.7% total solids (TS). The volatile solids (VS) removal ratio and methane yield in the stable state were 54.9% and 0.29 NL CH(4)/g VS(added), respectively. For reactor R2, when the TS content of fed sludge was 7.4%, the VS removal ratio and methane yield in the stable state were 73.2% and 0.38 NL CH(4)/g VS(added), respectively. When the TS content was increased to 9.5%, the VS removal ratio and methane yield slightly decreased to 69.3% and 0.32 NL CH(4)/g VS(added), respectively, but the reactor was stably operated. An increase of ammonia concentration was observed, but it was in the safe range without severe inhibition on the methane production. The result indicated that thermophilic AD could support sewage sludge with high TS content (9.5%) without abrupt deterioration of the treatment performance. The high-solids AD process is an economical method for centralized sewage sludge treatment with lower transport cost. PMID:24804672

Wang, Feng; Hidaka, Taira; Uchida, Tsutomu; Tsumori, Jun



Anaerobic digestion of wheat straw--performance of continuous solid-state digestion.  


In this study the upflow anaerobic solid-state (UASS) reactor was operated at various conditions to optimize the process parameters for anaerobically digesting wheat straw in a continuous process. Additionally, particle size effects have been studied in the operation at 55 and 60°C. Moreover, the incremental effect of the organic loading rate (OLR) to the system was examined from 2.5 to 8 gVS L(-1) d(-1). It was found that the UASS operating at 60 °C with a small OLR yields highest methane production, but the advantage over thermophilic operation is negligible. The rise in OLR reduces the systems yields, as expected. From OLR=8 gVS L(-1) d(-1) a second stage is necessary to circumvent volatile fatty acids accumulation. PMID:23954246

Pohl, Marcel; Heeg, Kathrin; Mumme, Jan



Enhancing the quality of bio-oil and selectivity of phenols compounds from pyrolysis of anaerobic digested rice straw.  


This study investigated the thermal decomposition characteristics and pyrolytic products of anaerobic digested rice straw (ADRS) by thermogravimetric (TG) and pyrolysis-gas chromatograph/mass spectrometry (Py-GC/MS) analysis. Compared with the raw rice straw (RS), the thermal decomposition temperature of ADRS was shifted to higher temperature zone and the second decomposition zone of cellulose (Toffset(c)-Tpeak) became narrower (14°C less), which indicated that the composition of rice straw were changed significantly by the anaerobic digestion pretreatment. Py-GC/MS analysis showed that the quality of the bio-oil and the selectivity of pyrolytic products could be obviously improved by anaerobic digestion. The total yields of alcohols, acids, aldehydes, furans, anhydrosugars, and ketones pyrolysis substances decreased, while the yield of phenols increased. The yield of 4-Vinylphenol (4-VP) increased from 29.33%, 8.21% and 5.76% to 34.93%, 12.46% and 7.68% at 330, 450 and 650°C, respectively, after anaerobic digestion. PMID:25647031

Liang, Jiajin; Lin, Yunqin; Wu, Shubin; Liu, Chao; Lei, Ming; Zeng, Chao



CFD simulation of mixing for high-solids anaerobic digestion.  


A computational fluid dynamics (CFD) model that simulates mechanical mixing for high-solids anaerobic digestion was developed. Numerical simulations of mixing manure slurry which exhibits non-Newtonian pseudo-plastic fluid behavior were performed for six designs: (i) one helical ribbon impeller; (ii) one anchor impeller; (iii) one curtain-type impeller; (iv) three counterflow (CF-2) impellers; (v) two modified high solidity (MHS 3/39°) impellers; and (vi) two pitched blade turbine impellers. The CFD model was validated against measurements for mixing a Herschel-Bulkley fluid by ribbon and anchor impellers. Based on mixing time with respect to mixing energy level, three impeller types (ribbon, CF-2, and MHS 3/39°) stand out when agitating highly viscous fluids, of these mixing with two MHS 3/39° impellers requires the lowest power input to homogenize the manure slurry. A comparison of digestion material demonstrates that the mixing energy varies with manure type and total solids concentration to obtain a given mixing time. Moreover, an in-depth discussion about the CFD strategy, the influences of flow regime and impeller type on mixing characteristics, and the intrinsic relation between mixing and flow field is included. PMID:22422446

Wu, Binxin



Modeling temperature variations in a pilot plant thermophilic anaerobic digester.  


A model that predicts temperature changes in a pilot plant thermophilic anaerobic digester was developed based on fundamental thermodynamic laws. The methodology utilized two simulation strategies. In the first, model equations were solved through a searching routine based on a minimal square optimization criterion, from which the overall heat transfer coefficient values, for both biodigester and heat exchanger, were determined. In the second, the simulation was performed with variable values of these overall coefficients. The prediction with both strategies allowed reproducing experimental data within 5% of the temperature span permitted in the equipment by the system control, which validated the model. The temperature variation was affected by the heterogeneity of the feeding and extraction processes, by the heterogeneity of the digestate recirculation through the heating system and by the lack of a perfect mixing inside the biodigester tank. The use of variable overall heat transfer coefficients improved the temperature change prediction and reduced the effect of a non-ideal performance of the pilot plant modeled. PMID:21120536

Valle-Guadarrama, Salvador; Espinosa-Solares, Teodoro; López-Cruz, Irineo L; Domaschko, Max



Anaerobic digestion of autoclaved and untreated food waste.  


Anaerobic digestion of autoclaved (160°C, 6.2 bar) and untreated source segregated food waste (FW) was compared over 473 days in semi-continuously fed mesophilic reactors with trace elements supplementation, at organic loading rates (OLRs) of 2, 3, 4 and 6 kg volatile solids(VS)/m(3)d. Methane yields at all OLR were 5-10% higher for untreated FW (maximum 0.483±0.013 m(3) CH4/kg VS at 3 kg VS/m(3) d) than autoclaved FW (maximum 0.439±0.020 m(3) CH4/kg VS at 4 kg VS/m(3) d). The residual methane potential of both digestates at all OLRs was less than 0.110 m(3) CH4/kg VS, indicating efficient methanation in all cases. Use of acclimated inoculum allowed very rapid increases in OLR. Reactors fed on autoclaved FW showed lower ammonium and hydrogen sulphide concentrations, probably due to reduced protein hydrolysis as a result of formation of Maillard compounds. In the current study this reduced biodegradability appears to outweigh any benefit due to thermal hydrolysis of ligno-cellulosic components. PMID:24238799

Tampio, Elina; Ervasti, Satu; Paavola, Teija; Heaven, Sonia; Banks, Charles; Rintala, Jukka



Efficiency of the anaerobic digestion of amine wastes.  


Laboratory-scale anaerobic degradation of monoethanolamine waste (MEAw) with co-substrate organics was conducted at room temperature and organic loading rates from 0.19 to 5.03 kg COD/m(3) day for 486 days in a hybrid digester. 90 % feed COD conversion to methane was obtained at the lower loads and only 45 % at the highest MEA waste/COD ratio (MEAwr) of 0.62 due to inhibition of methanogenesis. Inhibition at comparable loads decreased with time, implying that the culture adapted to the challenging feed. Methane yield was negatively correlated to MEAwr applied and inhibition avoided at MEAwr <0.5. Acetate accumulation implies inhibition of acetoclastic methanogenesis that can be caused by ammonia, a product of MEAw degradation. Moderate total ammonia nitrogen and free ammonia nitrogen accumulation, maximum 2.2 g N/l and 90 mg N/l, respectively suggests, however, that other components of MEAw, and/or degradation products of such, also inhibit methanogenesis, disturbing the digester performance. PMID:23912885

Wang, Shuai; Hovland, Jon; Bakke, Rune



Assessing solid digestate from anaerobic digestion as feedstock for ethanol production.  


Ethanol production using solid digestate (AD fiber) from a completely stirred tank reactor (CSTR) anaerobic digester was assessed comparing to an energy crop of switchgrass, and an agricultural residue of corn stover. A complete random design was fulfilled to optimize the reaction conditions of dilute alkali pretreatment. The most effective dilute alkali pretreatment conditions for raw CSTR AD fiber were 2% sodium hydroxide, 130 °C, and 3 h. Under these pretreatment conditions, the cellulose concentration of the AD fiber was increased from 34% to 48%. Enzymatic hydrolysis of 10% (dry basis) pretreated AD fiber produced 49.8 g/L glucose, while utilizing 62.6% of the raw cellulose in the AD fiber. The ethanol fermentation on the hydrolysate had an 80.3% ethanol yield. The cellulose utilization efficiencies determined that the CSTR AD fiber was a suitable biorefining feedstock compared to switchgrass and corn stover. PMID:20971637

Teater, Charles; Yue, Zhengbo; MacLellan, James; Liu, Yan; Liao, Wei



Anaerobic digestion of alkaline bleaching wastewater from a kraft pulp and paper mill using UASB technique.  


Anaerobic digestion of alkaline kraft elemental chlorine-free bleaching wastewater in two mesophilic, lab-scale upflow anaerobic sludge bed reactors resulted in significantly higher biogas production (250?±?50 vs. 120?±?30 NmL g [Formula: see text]) and reduction of filtered total organic carbon (fTOC) (60?±?5 vs. 43?±?6%) for wastewater from processing of hardwood (HW) compared with softwood (SW). In all cases, the gas production was likely underestimated due to poor gas separation in the reactors. Despite changes in wastewater characteristics, a stable anaerobic process was maintained with hydraulic retention times (HRTs) between 7 and 14?h. Lowering the HRT (from 13.5 to 8.5?h) did not significantly affect the process, and the stable performance at 8.5?h leaves room for further decreases in HRT. The results show that this type of wastewater is suitable for a full-scale implementation, but the difference in methane potential between SW and HW is important to consider both regarding process dimensioning and biogas yield optimization. PMID:25441833

Larsson, Madeleine; Truong, Xu-Bin; Björn, Annika; Ejlertsson, Jörgen; Bastviken, David; Svensson, Bo H; Karlsson, Anna



Life-Cycle Analysis of Energy and Greenhouse Gas Emissions from Anaerobic Biodegradation of Municipal Solid Waste  

Microsoft Academic Search

Energy requirements and greenhouse gas GHG emissions for current landfilling of municipal solid waste MSW was compared to potential biodegradation of MSW in anaerobic digesters AD throughout the United States. A hybrid life-cycle analysis was completed to assess the potential for anaerobic biodegradation of MSW to methane, a valuable energy source. Conversion of MSW to methane in AD would generate

Thomas D. DiStefano



Pretreatment of sludge with microwaves for pathogen destruction and improved anaerobic digestion performance.  


A new way of generating Class A sludge using microwaves was evaluated through a series of laboratory-scale experiments. Microwaves provide rapid and uniform heating throughout the material. Other benefits of microwave treatment include instant and accurate control and selective and concentrated heating on materials, such as sludge, that have a high dielectric loss factor. Sludge was irradiated with 2450-MHz microwaves, and fecal coliforms were counted. Fecal coliforms were not detected at 65 degrees C for primary sludge and anaerobic digester sludge and at 85 degrees C for waste activated sludge when sludge was irradiated with 2450-MHz microwaves. During the bench-scale anaerobic digester operation, the highest average log reduction of fecal coliforms was achieved by the anaerobic digester fed with microwave-pretreated sludge (> or = 2.66 log removal). The anaerobic digester fed with microwave-irradiated sludge was more efficient in inactivation of fecal coliforms than the other two digesters fed with raw sludge and externally heated sludge, respectively. It took more than three hydraulic retention times for a bench-scale mesophilic anaerobic digester to meet Class A sludge requirements after feeding microwave-irradiated sludge. Class A sludge can be produced consistently with a continuously fed mesophilic anaerobic digester if sludge is pretreated with microwaves to reach 65 degrees C. PMID:16553169

Hong, Seung M; Park, Jae K; Teeradej, N; Lee, Y O; Cho, Y K; Park, C H



Anaerobic Co-digestion of Chicken Processing Wastewater and Crude Glycerol from Biodiesel  

E-print Network

The main objective of this thesis was to study the anaerobic digestion (AD) of wastewater from a chicken processing facility and of crude glycerol from local biodiesel operations. The AD of these substrates was conducted in bench-scale reactors...

Foucault, Lucas Jose




EPA Science Inventory

In raw sludges and in mesophilically and thermophilically digested anaerobic sludges, large variations in numbers of viruses occurred over narrow ranges of numbers of fecal coliforms, total coliforms, and fecal streptococci, demonstrating that the bacteria are poor quantitative r...


Anaerobic digestion of selected Italian agricultural and industrial residues (grape seeds and leather dust): combined methane production and digestate characterization.  


A combined experimental evaluation of methane production (obtained by anaerobic digestion) and detailed digestate characterization (with physical-chemical, thermo-gravimetric and mineralogical approaches) was conducted on two organic substrates, which are specific to Italy (at regional and national levels). One of the substrates was grape seeds, which have an agricultural origin, whereas the other substrate was vegetable-tanned leather dust, which has an industrial origin. Under the assumed experimental conditions of the performed lab-scale test series, the grape seed substrate exhibited a resulting net methane production of 175.0 NmL g volatile solids (VS)(-1); hence, it can be considered as a potential energy source via anaerobic digestion. Conversely, the net methane production obtained from the anaerobic digestion of the vegetable-tanned leather dust substrate was limited to 16.1 NmL gVS(-1). A detailed characterization of the obtained digestates showed that there were both nitrogen-containing compounds and complex organic compounds present in the digestate that was obtained from the mixture of leather dust and inoculum. As a general perspective of this experimental study, the application of diversified characterization analyzes could facilitate (1) a better understanding of the main properties of the obtained digestates to evaluate their potential valorization, and (2) a combination of the digestate characteristics with the corresponding methane productions to comprehensively evaluate the bioconversion process. PMID:24191456

Caramiello, C; Lancellotti, I; Righi, F; Tatàno, F; Taurino, R; Barbieri, L



Continuous anaerobic digestion of food waste and design of digester with lipid removal.  


Separation of municipal solid waste has been implemented in many cities in China. As a major component of municipal solid waste, food waste can be treated by anaerobic digestion (AD) for energy production. To provide reference data for disposing of food waste through engineering applications, continuous AD was carried out under various organic loading rates (OLRs) at 27 +/- 2 degrees C in the laboratory. The anaerobic reactor was stable with pH 7.0-7.1, total volatile fatty acid (VFA) concentrations of 206-746 mg/L, and NH4+ -N concentrations of 525-1293 mg/L when the OLR was 1.118-5.588 kg volatile solids (VS)/m(3) x d. The maximum volumetric biogas production rate was 4.41 L/L x d when the OLR was increased to 5.588 kg VS/m(3) x d with a hydraulic retention time of 30 d. When the OLR was increased to 6.706 and 8.382 kg VS/m(3) x d, biogas production was seriously inhibited by VFAs, with maximum total VFA and propionate concentrations of 8738 mg/L and 2864 mg/L, respectively. Due to the incomplete degradation of lipids, the specific methane production rate of 353-488 L/kg VS accounted for 55.2-76.3% of the theoretical methane potential calculated based on the component composition. A retrofitted anaerobic digester with lipid removal was designed to improve the efficiency. PMID:24350467

Li, Dong; Sun, Yongming; Guo, Yanfeng; Yuan, Zhenhong; Wang, Yao; Zhen, Feng



Anaerobic Digesters: From Waste to Energy Crops as an Alternative Energy Source  

Microsoft Academic Search

The main objective of the present study is to investigate the integrated organic waste-anaerobic digester-energy crop production system as a eco-agricultural system and to use anaerobically digested cattle slurry as fertilizer for safflower production. The value of slurry as fertilizer for growing safflower was compared with commercial organic and chemical fertilizers. According to the results of this study, higher yields

G. Kocar



Phylogenetic and functional diversity of propionate-oxidizing bacteria in an anaerobic digester sludge  

Microsoft Academic Search

The phylogenetic and functional diversity of syntrophic propionate-oxidizing bacteria (POB) present in an anaerobic digester\\u000a was investigated by microautoradiography combined with fluorescent in situ hybridization (MAR–FISH) that can directly link\\u000a 16S rRNA phylogeny with in situ metabolic function. The syntrophic POB community in the anaerobic digester sludge consisted\\u000a of at least four phylogenetic groups: Syntrophobacter, uncultured short rod Smithella (Smithella

Herto Dwi Ariesyady; Tsukasa Ito; Kazumi Yoshiguchi; Satoshi Okabe



Biodegradability of wastewater and activated sludge organics in anaerobic digestion.  


The investigation provides experimental evidence that the unbiodegradable particulate organics fractions of primary sludge and waste activated sludge calculated from activated sludge models remain essentially unbiodegradable in anaerobic digestion. This was tested by feeding the waste activated sludge (WAS) from three different laboratory activated sludge (AS) systems to three separate anaerobic digesters (AD). Two of the AS systems were Modified Ludzack - Ettinger (MLE) nitrification-denitrification (ND) systems and the third was a membrane University of Cape Town (UCT) ND and enhanced biological P removal system. One of the MLE systems and the UCT system were fed the same real settled wastewater. The other MLE system was fed raw wastewater which was made by adding a measured constant flux (gCOD/d) of macerated primary sludge (PS) to the real settled wastewater. This PS was also fed to a fourth AD and a blend of PS and WAS from settled wastewater MLE system was fed to a fifth AD. The five ADs were each operated at five different sludge ages (10-60d). From the measured performance results of the AS systems, the unbiodegradable particulate organic (UPO) COD fractions of the raw and settled wastewaters, the PS and the WAS from the three AS systems were calculated with AS models. These AS model based UPO fractions of the PS and WAS were compared with the UPO fractions calculated from the performance results of the ADs fed these sludges. For the PS, the UPO fraction calculated from the AS and AD models matched closely, i.e. 0.30 and 0.31. Provided the UPO of heterotrophic (OHO, fE_OHO) and phosphorus accumulating (PAO, fE_PAO) biomass were accepted to be those associated with the death regeneration model of organism "decay", the UPO of the WAS calculated from the AS and AD models also matched well - if the steady state AS model fE_OHO = 0.20 and fE_PAO = 0.25 values were used, then the UPO fraction of the WAS calculated from the AS models deviated significantly from those calculated with the AD models. Therefore in plant wide wastewater treatment models the characterization of PS and WAS as defined by the AS models can be applied without modification in AD models. The observed rate limiting hydrolysis/acidogenesis rates of the sludges are listed. PMID:24699419

Ikumi, D S; Harding, T H; Ekama, G A



Biogas plasticization coupled anaerobic digestion: continuous flow anaerobic pump test results.  


In this investigation, the Anaerobic Pump (TAP) and a conventional continuous flow stirred tank reactor (CFSTR) were tested side by side to compare performance. TAP integrates anaerobic digestion (AD) with biogas plasticization-disruption cycle to improve mass conversion to methane. Both prototypes were fed a "real world" 50:50 mixture of waste-activated sludge (WAS) and primary sludge and operated at room temperature (20 degrees Celsius). The quantitative results from three steady states show TAP peaked at 97% conversion of the particulate COD in a system hydraulic residence time (HRT) of only 6 days. It achieved a methane production of 0.32 STP cubic meter CH(4) per kilogram COD fed and specific methane yield of 0.78 m(3) CH(4) per cubic meter per day. This was more than three times the CFSTR specific methane yield (0.22 m(3) CH(4) per cubic meter per day) and more than double the CFSTR methane production (0.15 m(3) CH(4) per kilogram COD fed). A comparative kinetics analysis showed the TAP peak substrate COD removal rate (R (o)) was 2.24 kg COD per cubic meter per day, more than three times the CFSTR substrate removal rate of 0.67 kg COD per cubic meter per day. The three important factors contributing to the superior TAP performance were (1) effective solids capture (96%) with (2) mass recycle and (3) stage II plasticization-disruption during active AD. The Anaerobic Pump (TAP) is a high rate, high efficiency-low temperature microbial energy engine that could be used to improve renewable energy yields from classic AD waste substrates like refuse-derived fuels, treatment plant sludges, food wastes, livestock residues, green wastes and crop residuals. PMID:19455433

Schimel, Keith A; Boone, David R



Modelling anaerobic digestion acclimatisation to a biodegradable toxicant: application to cyanide  

Microsoft Academic Search

The observed acclimatisation to biodegradable toxicants in anaerobic cassava wastewater treatment is explained by modelling anaerobic cyanide degradation. A complete degradation pathway is proposed for cyanide. Cyanide degradation is modelled as enzymatic hydrolysis to formate and ammonia. Ammonia is added to the inorganic nitrogen content of the digester while formate is degraded by the hydrogenotrophic methanogens. Cyanide irreversible enzyme inhibition

U. Zaher; M. S. Moussa; I. N. Widyatmika; P. van Der Steen; H. J. Gijzen; P. A. Vanrolleghem



Assessing the Fate of Ascaris suum Ova during Mesophilic Anaerobic Digestion.  


There is limited knowledge about the survival of geohelminths, which are soil-transmitted human pathogens, in mesophilic anaerobic digestion processes. This study examined the fate of embryonated and unembryonated Ascaris suum ova in six laboratory-scale mesophilic (35 °C) anaerobic digesters processing swine manure to identify their survival strategies and investigate potential mechanisms to enhance their destruction. There was no significant difference in inactivation of Ascaris suum ova in digesters operated at different solids residence times (SRT) or feeding frequencies. Ova exposed to an anaerobic environment became dormant, or remained unembryonated throughout their residence in the reactors. Approximately 65% of ova were able to retain their viability for up to 16 days, after which the rate of inactivation increased until nearly all ova were nonviable by day 24. In contrast, ova exposed to aerobic conditions did not become dormant and progressed through several developmental stages until day 16, after which nearly all ova were observed to be nonviable. In addition, only 35% of fully developed ova exposed to the anaerobic environment retained their viability by day 16 compared to 65% for dormant ova. Results suggest that some ova are physically destroyed during digestion and ova can be inactivated faster if their development cycle is aerobically triggered before entering the anaerobic digestion process. Results also suggest that transfer of resource recovery technologies such as mesophilic anaerobic digestion to developing world settings must account for local climatic and health conditions so mutually beneficial outcomes can be attained. PMID:25679819

Manser, Nathan D; Wald, Ileana; Ergas, Sarina J; Izurieta, Ricardo; Mihelcic, James R



Comparative performance of anaerobic digesters operating on ice-cream wastewater  

Microsoft Academic Search

Pilot-scale anaerobic digesters were operated on ice-cream wastewater for over three years. The performance of four reactor designs, an anaerobic filter, contact process and UASB of capacity 5 m3, and a 0.5 m3 fluidised bed, was compared. The anaerobic filter, with a 3.3 m3 Pall ring bed, operated stably at organic loading rates (Bv) around 6 kg COD m?3d?1, giving

Freda R. Hawkes; T. Donnelly; G. K. Anderson



Supercritical Fluid Extraction of Bacterial and Archaeal Lipid Biomarkers from Anaerobically Digested Sludge  

PubMed Central

Supercritical fluid extraction (SFE) was used in the analysis of bacterial respiratory quinone (RQ), bacterial phospholipid fatty acid (PLFA), and archaeal phospholipid ether lipid (PLEL) from anaerobically digested sludge. Bacterial RQ were determined using ultra performance liquid chromatography (UPLC). Determination of bacterial PLFA and archaeal PLEL was simultaneously performed using gas chromatography-mass spectrometry (GC-MS). The effects of pressure, temperature, and modifier concentration on the total amounts of RQ, PLFA, and PLEL were investigated by 23 experiments with five settings chosen for each variable. The optimal extraction conditions that were obtained through a multiple-response optimization included a pressure of 23.6 MPa, temperature of 77.6 °C, and 10.6% (v/v) of methanol as the modifier. Thirty nine components of microbial lipid biomarkers were identified in the anaerobically digested sludge. Overall, the SFE method proved to be more effective, rapid, and quantitative for simultaneously extracting bacterial and archaeal lipid biomarkers, compared to conventional organic solvent extraction. This work shows the potential application of SFE as a routine method for the comprehensive analysis of microbial community structures in environmental assessments using the lipid biomarkers profile. PMID:22489140

Hanif, Muhammad; Atsuta, Yoichi; Fujie, Koichi; Daimon, Hiroyuki



Mechanisms of floc destruction during anaerobic and aerobic digestion and the effect on conditioning and dewatering of biosolids  

Microsoft Academic Search

Laboratory anaerobic and aerobic digestion studies were conducted using waste activated sludges from two municipal wastewater treatment plants in order to gain insight into the mechanisms of floc destruction that account for changes in sludge conditioning and dewatering properties when sludges undergo anaerobic and aerobic digestion. Batch digestion studies were conducted at 20°C and the dewatering properties, solution biopolymer concentration

John T. Novak; Mary E. Sadler; Sudhir N. Murthy



Anaerobic digestion of giant reed for methane production.  


As a fast growing plant, giant reed has good potential to be used as a feedstock for methane production via anaerobic digestion (AD). The effect of total solids (TS) content, an AD operating parameter, was studied. Results showed that increasing TS from 8% to 38% decreased methane yield, due to the inhibition of volatile fatty acids (VFAs) and total ammonia nitrogen (TAN); while the maximum volumetric methane production was obtained at 20-23% TS. Comparison of solid-state AD (SS-AD) at 20% TS and liquid AD (L-AD) at 8% TS was conducted at feedstock to effluent (F/E) ratios of 2.0, 3.5, and 5.0. The best performance was achieved at an F/E of 2.0, with methane yields of 129.7 and 150.8L-CH4/kg-VS for SS-AD and L-AD, respectively. Overall organic components were degraded by 17.7-28.5% and 24.0-26.6% in SS-AD and L-AD, respectively; among which cellulose showed the highest degradation rate and the highest contribution to methane production. PMID:25203231

Yang, Liangcheng; Li, Yebo



Anaerobic digestibility of marine microalgae Phaeodactylum tricornutum in a lab-scale anaerobic membrane bioreactor.  


The biomass of industrially grown Phaeodactylum tricornutum was subjected in a novel way to bio-methanation at 33°C, i.e., in an anaerobic membrane bioreactor (AnMBR) at a hydraulic retention time of 2.5 days, at solid retention times of 20 to 10 days and at loading rates in the range of 2.6-5.9 g biomass-COD L(-1) day(-1) with membrane fluxes ranging from 1 to 0.8 L m(-2) h(-1). The total COD recovered as biogas was in the order of 52%. The input suspension was converted to a clear effluent rich in total ammonium nitrogen (546 mg TAN L(-1)) and phosphate (141 mg PO(4)-P L(-1)) usable as liquid fertilizer. The microbial community richness, dynamics, and organization in the reactor were interpreted using the microbial resource management approach. The AnMBR communities were found to be moderate in species richness and low in dynamics and community organization relative to UASB and conventional CSTR sludges. Quantitative polymerase chain reaction analysis revealed that Methanosaeta sp. was the dominant acetoclastic methanogen species followed by Methanosarcina sp. This work demonstrated that the use of AnMBR for the digestion of algal biomass is possible. The fact that some 50% of the organic matter is not liquefied means that the algal particulates in the digestate constitute a considerable fraction which should be valorized properly, for instance as slow release organic fertilizer. Overall, 1 kg of algae dry matter (DM) could be valorized in the form of biogas ( euro 2.07), N and P in the effluent (euro 0.02) and N and P in the digestate (euro 0.04), thus totaling about euro 2.13 per kilogram algae DM. PMID:22005739

Zamalloa, Carlos; De Vrieze, Jo; Boon, Nico; Verstraete, Willy



Modeling the anaerobic digestion of cane-molasses vinasse: Extension of the Anaerobic Digestion Model No. 1 (ADM1) with sulfate reduction for a very high strength and sulfate rich wastewater.  


This research presents the modeling of the anaerobic digestion of cane-molasses vinasse, hereby extending the Anaerobic Digestion Model No. 1 with sulfate reduction for a very high strength and sulfate rich wastewater. Based on a sensitivity analysis, four parameters of the original ADM1 and all sulfate reduction parameters were calibrated. Although some deviations were observed between model predictions and experimental values, it was shown that sulfates, total aqueous sulfide, free sulfides, methane, carbon dioxide and sulfide in the gas phase, gas flow, propionic and acetic acids, chemical oxygen demand (COD), and pH were accurately predicted during model validation. The model showed high (±10%) to medium (10%-30%) accuracy predictions with a mean absolute relative error ranging from 1% to 26%, and was able to predict failure of methanogenesis and sulfidogenesis when the sulfate loading rate increased. Therefore, the kinetic parameters and the model structure proposed in this work can be considered as valid for the sulfate reduction process in the anaerobic digestion of cane-molasses vinasse when sulfate and organic loading rates range from 0.36 to 1.57 kg [Formula: see text]  m(-3) d(-1) and from 7.66 to 12 kg COD m(-3) d(-1), respectively. PMID:25589435

Barrera, Ernesto L; Spanjers, Henri; Solon, Kimberly; Amerlinck, Youri; Nopens, Ingmar; Dewulf, Jo



Advanced controlling of anaerobic digestion by means of hierarchical neural networks.  


In this work several feed-forward back propagation neural networks (FFBP) were trained in order to model, and subsequently control, methane production in anaerobic digesters. To produce data for the training of the neural nets, four anaerobic continuous stirred tank reactors were operated in steady-state conditions at organic loading rates (Br) of about 2 kg m(-3) d(-1) chemical oxygen demand, and disturbed by pulse-like increase of the organic loading rate. For the pulses additional carbon sources like flour, sucrose, 1,2-diethylen glycol or vegetable oil were added to the basic feed, which consisted of surplus and primary sludge of a local waste-water treatment plant, to increase the chemical oxygen demand. Measured parameters were: gas composition, methane production rate, volatile fatty acid concentration, pH, redox potential, volatile suspended solids and chemical oxygen demand of feed and effluent. A hierarchical system of nets was developed and embedded in a decision support system to find out which is the best feeding profile for the next time steps in advance. A 3-3-1 FFBP simulated the pH with a regression coefficient of 0.82. A 9-3-3 FFBP simulated the volatile fatty acid concentration in the sludge with a regression coefficient of 0.86. And a 9-3-2 FFBP simulated the gas production and gas composition with a regression coefficient of 0.90 and 0.80, respectively. A lab-scale anaerobic continuous stirred tank reactor controlled by this tool was able to maintain a methane concentration of about 60% at a rather high gas production rate of between 5 and 5.6 m3 m(-3) d(-1). PMID:12153025

Holubar, Peter; Zani, Loredana; Hager, Michael; Fröschl, Walter; Radak, Zorana; Braun, Rudolf



Anaerobic digestibility of beef hooves with swine manure or slaughterhouse sludge.  


Anaerobic digestion is an effective method for treating animal by-products, generating at the same time green energy as methane (CH4). However, the methods and mechanisms involved in anaerobic digestion of ?-keratin wastes like hair, nails, horns and hooves are still not clear. In this study we investigated the feasibility of anaerobically co-digesting ground beef hooves in the presence of swine manure or slaughterhouse sludge at 25°C using eight 42-L Plexiglas lab-scale digesters. Our results showed addition of beef hooves statistically significantly increased the rate of CH4 production with swine manure, but only increased it slightly with slaughterhouse sludge. After 90-day digestion, 73% of beef hoof material added to the swine manure-inoculated digesters had been converted into CH4, which was significantly higher than the 45% level achieved in the slaughterhouse sludge inoculated digesters. BODIPY-Fluorescent casein staining detected proteolytic bacteria in all digesters with and without added beef hooves, and their relative abundances corresponded to the rate of methanogenesis of the digesters with the different inocula. Fluorescence in situ hybridization in combination with BODIPY-Fluorescent casein staining identified most proteolytic bacteria as members of genus Alkaliphilus in the subfamily Clostridiaceae 2 of family Clostridiaceae. They thus appear to be the bacteria mainly responsible for digestion of beef hooves. PMID:25595391

Xia, Yun; Wang, Ding-Kang; Kong, Yunhong; Ungerfeld, Emilio M; Seviour, Robert; Massé, Daniel I



The effects of sludge rheology on mixing in the anaerobic digestion process  

Microsoft Academic Search

A review of the literature indicated that the understanding of the mixing process in anaerobic digesters is limited. Also indicated was the fact that the ability to measure digester mixing characteristics was lacking and that the rheological characteristics of the sludge have been largely ignored. The need for a more thorough understanding of fundamental mixing relationships and the ability to



Biogas Crops - Part I: Specifications and Suitability of Field Crops for Anaerobic Digestion  

Microsoft Academic Search

In Germany, the growing number of agricultural biogas plants causes an increasing demand for crops as a feedstock in both mono- and co-digestion processes. Laboratory scale batch anaerobic digestion tests under mesophilic conditions according to the German Standard Procedure VDI 4630 were conducted to investigate the suitability of different plant species like barley (Hordeum vulgare), rye (Secale cereale), triticale (X

M. Heiermann; M. Plöchl; B. Linke; H. Schelle; C. Herrmann




EPA Science Inventory

A study was conducted of the relative performance of anaerobic digestion systems under mesophilic and thermophilic conditions. Fifty liter laboratory scale digesters were fed primary sludge from the Allentown, PA Waste Water Treatment Plant. Long-term, steady-state performance da...


Anaerobic digestion of chicken feather with swine manure or slaughterhouse sludge for biogas production  

Microsoft Academic Search

Biogas production from anaerobic digestion of chicken feathers with swine manure or slaughterhouse sludge was assessed in two separate experiments. Ground feathers without any pre-treatment were added to 42-L digesters inoculated with swine manure or slaughterhouse sludge, representing 37% and 23% of total solids, respectively and incubated at 25°C in batch mode. Compared to the control without feather addition, total

Yun Xia; Daniel I. Massé; Tim A. McAllister; Carole Beaulieu; Emilio Ungerfeld



EPA Science Inventory

A technological and socioeconomic assessment of anaerobic digester feasibility for small to mid-size livestock operations was undertaken. Three full scale digesters and one pilot scale facility were under various degrees of monitoring and evaluation to assess design and operation...


Pilot plant study of the effects of quebracho and wattle on anaerobic digestion  

SciTech Connect

Quebracho and wattle tannin adversely affected the operational control required for the systems as well as CH4 production. The anaerobic organisms however degraded the tannins and the characteristic red color was effectively removed from the supernatant (liquid phase of digested sludge) during digestion.

Eye, J.D.; Ficker, C.F.



Microbial-chemical indicator for anaerobic digester performance assessment in full-scale wastewater treatment plants for biogas production.  


Anaerobic digestion was introduced into wastewater treatment plants several years ago, but anaerobic digestion performance has not yet been achieved. The variability of the microbial community in digesters is poorly understood, and despite the crucial role of anaerobic digestion reactors, the microbial equilibrium that yields the best performance in these reactors has only recently been hypothesised. In this study, two full-scale continuous anaerobic reactors, placed in Torino's main wastewater treatment plant in northern Italy, were followed to develop a summary indicator for measuring anaerobic digestion performance. A total of 100 sludge samples were collected. The samples were characterised chemically and physically, and microbial groups were quantified by qRT-PCR. A chemical biological performance index strictly correlated to specific biogas production (rho=0.739, p<0.01) is proposed. This approach will produce new management tools for anaerobic digestion in wastewater treatment plants. PMID:25817028

Traversi, Deborah; Romanazzi, Valeria; Degan, Raffaella; Lorenzi, Eugenio; Carraro, Elisabetta; Gilli, Giorgio



Biohydrogen production from dual digestion pretreatment of poultry slaughterhouse sludge by anaerobic self-fermentation  

Microsoft Academic Search

Poultry slaughterhouse sludge from chicken processing wastewater treatment plant was tested for their suitability as a substrate and inoculum source for fermentation hydrogen production. Dual digestion of poultry slaughterhouse sludge was employed to produce hydrogen by batch anaerobic self-fermentation without any extra-seeds. The sludge (5% TS) was dual digested by aerobic thermophilic digestion at 55 °C with the varying retention time

Sureewan Sittijunda; Alissara Reungsang; Sompong O-thong



Anaerobic co-digestion of dairy manure with mulched switchgrass for improvement of the methane yield  

Microsoft Academic Search

The owners of farm-scale anaerobic digesters are relying on off-farm wastes or energy crops as a co-digestion feedstock with\\u000a animal manure in order to increase their production of methane and thus revenues. Switchgrass represents an interesting feedstock\\u000a for Canadian digesters owners as it is a high-yielding low-maintenance perennial crop, well adapted to northern climate. Methane\\u000a potential assays in batch tests

Jean-Claude Frigon; Caroline Roy; Serge R. Guiot


Effect of seasonal changes in quantities of biowaste on full scale anaerobic digester performance  

SciTech Connect

A 750,000 l digester located in Roppen/Austria was studied over a 2-year period. The concentrations and amounts of CH{sub 4}, H{sub 2}, CO{sub 2} and H{sub 2}S and several other process parameters like temperature, retention time, dry weight and input of substrate were registered continuously. On a weekly scale the pH and the concentrations of NH{sub 4}{sup +}-N and volatile fatty acids (acetic, butyric, iso-butyric, propionic, valeric and iso-valeric acid) were measured. The data show a similar pattern of seasonal gas production over 2 years of monitoring. The consumption of VFA and not the hydrogenotrophic CH{sub 4} production appeared to be the limiting factor for the investigated digestion process. Whereas the changes in pH and the concentrations of most VFA did not correspond with changes in biogas production, the ratio of acetic to propionic acid and the concentration of H{sub 2} appeared to be useful indicators for reactor performance. However, the most influential factors for the anaerobic digestion process were the amount and the quality of input material, which distinctly changed throughout the year.

Illmer, P. [University of Innsbruck, Institute of Microbiology, Technikerstr. 25, A-6020 Innsbruck (Austria)], E-mail:; Gstraunthaler, G. [Abfallbeseitigungsverband Westtirol, Breite Mure, A-6426 Roppen (Austria)



Ammonia and temperature determine potential clustering in the anaerobic digestion microbiome.  


Anaerobic digestion is regarded as a key environmental technology in the present and future bio-based economy. The microbial community completing the anaerobic digestion process is considered complex, and several attempts already have been carried out to determine the key microbial populations. However, the key differences in the anaerobic digestion microbiomes, and the environmental/process parameters that drive these differences, remain poorly understood. In this research, we hypothesized that differences in operational parameters lead to a particular composition and organization of microbial communities in full-scale installations. A total of 38 samples were collected from 29 different full-scale anaerobic digestion installations, showing constant biogas production in function of time. Microbial community analysis was carried out by means of amplicon sequencing and real-time PCR. The bacterial community in all samples was dominated by representatives of the Firmicutes, Bacteroidetes and Proteobacteria, covering 86.1 ± 10.7% of the total bacterial community. Acetoclastic methanogenesis was dominated by Methanosaetaceae, yet, only the hydrogenotrophic Methanobacteriales correlated with biogas production, confirming their importance in high-rate anaerobic digestion systems. In-depth analysis of operational and environmental parameters and bacterial community structure indicated the presence of three potential clusters in anaerobic digestion. These clusters were determined by total ammonia concentration, free ammonia concentration and temperature, and characterized by an increased relative abundance of Bacteroidales, Clostridiales and Lactobacillales, respectively. None of the methanogenic populations, however, could be significantly attributed to any of the three clusters. Nonetheless, further experimental research will be required to validate the existence of these different clusters, and to which extent the presence of these clusters relates to stable or sub-optimal anaerobic digestion. PMID:25819618

De Vrieze, Jo; Saunders, Aaron Marc; He, Ying; Fang, Jing; Nielsen, Per Halkjaer; Verstraete, Willy; Boon, Nico



Thermal wet oxidation improves anaerobic biodegradability of raw and digested biowaste.  


Anaerobic digestion of solid biowaste generally results in relatively low methane yields of 50-60% of the theoretical maximum. Increased methane recovery from organic waste would lead to reduced handling of digested solids, lower methane emissions to the environment, and higher green energy profits. The objective of this research was to enhance the anaerobic biodegradability and methane yields from different biowastes (food waste, yard waste, and digested biowaste already treated in a full-scale biogas plant (DRANCO, Belgium)) by assessing thermal wet oxidation. The biodegradability of the waste was evaluated by using biochemical methane potential assays and continuous 3-L methane reactors. Wet oxidation temperature and oxygen pressure (T, 185-220 degrees C; O2 pressure, 0-12 bar; t, 15 min) were varied for their effect on total methane yield and digestion kinetics of digested biowaste. Measured methane yields for raw yard waste, wet oxidized yard waste, raw food waste, and wet oxidized food waste were 345, 685, 536, and 571 mL of CH/g of volatile suspended solids, respectively. Higher oxygen pressure during wet oxidation of digested biowaste considerably increased the total methane yield and digestion kinetics and permitted lignin utilization during a subsequent second digestion. The increase of the specific methane yield for the full-scale biogas plant by applying thermal wet oxidation was 35-40%, showing that there is still a considerable amount of methane that can be harvested from anaerobic digested biowaste. PMID:15260343

Lissens, Geert; Thomsen, Anne Belinda; De Baere, Luc; Verstraete, Willy; Ahring, Birgitte K



Feasibility and interest of the anammox process as treatment alternative for anaerobic digester supernatants in manure processing--an overview.  


Completely autotrophic nitrogen removal (ANR) is based on the combination of partial nitritation (PN) and anaerobic ammonium oxidation (anammox). It is a promising alternative for the subsequent treatment of biogas digester supernatants in livestock manure processing and nitrogen surplus scenarios. However, as no full-scale experiences in the treatment of manure digestates by ANR have been published to date, future field studies addressing treatment of this kind of effluent would be of great interest. Some topics to be considered in these studies would be coupling anaerobic digestion and ANR, analysis of the factors that affect the process, comparing reactor configurations, microbial ecology, gas emissions, and achieving robust performance. This paper provides an overview of published studies on ANR. Specific issues related to the applicability of the process for treating manure digestates are discussed. The energy requirements of ANR are compared with those of other technological alternatives aimed at recovering nitrogen from digester supernatants. The results of the assessment were shown to depend on the composition of the supernatant. In this regard, the PN-anammox process was shown to be more competitive than other alternatives particularly at concentrations of up to 2 kg NH4(+)-N m(-3). PMID:24161806

Magrí, Albert; Béline, Fabrice; Dabert, Patrick



Anaerobic digestion of macroalgae: methane potentials, pre-treatment, inhibition and co-digestion.  


In the present study we tested four macroalgae species--harvested in Denmark--for their suitability of bioconversion to methane. In batch experiments (53 degrees C) methane yields varied from 132 ml g volatile solids(-1) (VS) for Gracillaria vermiculophylla, 152 mi gVS(-1) for Ulva lactuca, 166 ml g VS(-1) for Chaetomorpha linum and 340 ml g VS(-1) for Saccharina latissima following 34 days of incubation. With an organic content of 21.1% (1.5-2.8 times higher than the other algae) S. latissima seems very suitable for anaerobic digestion. However, the methane yields of U. lactuca, G. vermiculophylla and C. linum could be increased with 68%, 11% and 17%, respectively, by pretreatment with maceration. U. lactuca is often observed during 'green tides' in Europe and has a high cultivation potential at Nordic conditions. Therefore, U. lactuca was selected for further investigation and co-digested with cattle manure in a lab-scale continuously stirred tank reactor. A 48% increase in methane production rate of the reactor was observed when the concentration of U. lactuca in the feedstock was 40% (VS basis). Increasing the concentration to 50% had no further effect on the methane production, which limits the application of this algae at Danish centralized biogas plant. PMID:22335117

Nielsen, H B; Heiske, S



Relationship between anaerobic digestion of biodegradable solid waste and spectral characteristics of the derived liquid digestate.  


The evolution of spectral properties during anaerobic digestion (AD) of 29 types of biodegradable solid waste was investigated to determine if spectral characteristics could be used for assessment of biological stabilization during AD. Biochemical methane potential tests were conducted and spectral indicators (including the ratio of ultraviolet-visible absorbance at 254nm to dissolved organic carbon concentration (SUVA254), the ratio of ultraviolet-visible absorbance measured at 465nm and 665nm (E4/E6), and the abundance of fluorescence peaks) were measured at different AD phases. Inter-relationship between organic degradation and spectral indicators were analyzed by principle component analysis. The results shows that from methane production phase to the end of methane production phase, SUVA254 increased by 0.16-10.93 times, the abundance of fulvic acid-like compounds fluorescence peak increased by 0.01-0.54 times, the abundance of tyrosine fluorescence peak decreased by 0.03-0.64 times. Therefore, these indicators were useful to judge the course of mixed waste digestion. PMID:24686373

Zheng, Wei; Lü, Fan; Phoungthong, Khamphe; He, Pinjing



The effects of sludge rheology on mixing in the anaerobic digestion process  

SciTech Connect

A review of the literature indicated that the understanding of the mixing process in anaerobic digesters is limited. Also indicated was the fact that the ability to measure digester mixing characteristics was lacking and that the rheological characteristics of the sludge have been largely ignored. The need for a more thorough understanding of fundamental mixing relationships and the ability to measure these relationships in the anaerobic digester was recognized. The measurement of mixing characteristics in two laboratory-scale, impeller mixed, anaerobic digesters was based on the concepts of Circulation Time Distribution theory. Circulation time was measured directly from a continuous recording of the change in conductivity following a pulse injection of an ionic tracer. Mean circulation time values were used to derive impeller discharge and pumping flow rates. Impeller flow rates were determined in water and in digesting sludge for comparison. The determination of digesting sludge rheological properties was based on a simple viscometric method, using a Brookfield Model RVT viscometer. The viscometer data were converted to shear stress and shear rate values using conversion factors obtained from the literature. Viscosity functions were derived for the digesting sludge at various levels of total suspended solids. Tests for thixotropy were also conducted on the digesting sludge. The results of this study indicated that the rheological properties of digesting sludge have significant effects on the anaerobic digester mixing process. The Circulation Time Distribution method provided the ability to detect these effects. Additional studies are needed to extend the use of the CTD method and to better define its potential as a tool for designing digester mixing systems.

Baxter, T.E.



Anaerobic digestion as a sustainable solution for biosolids management by the Montreal metropolitan community.  


The Quebec Waste Management Policy (1998-2008) is requesting that the municipalities prepare a waste management plan, including a global objective of 60% of these wastes to be diverted from landfill sites by reduction, re-usage, recycling and valorization. Around 5.8 million tons of wastes were generated on the territory of the Montreal Metropolitan Community in 2001 for a population of about 3.5 millions citizens. In this paper, we present different management scenarios in which anaerobic digestion was used as a valorization step, focusing on the energetic value of the methane produced and the reduction in greenhouse gas (GHG) emissions. The four scenarios prepared cover the valorization of the organic fraction of municipal solid wastes, green wastes and excess sludge and showed potential methane generation of 17-140 Mm3 with a GHG reduction of 62,000-500,000 tons of CO2-equivalents. PMID:16180478

Frigon, J C; Guiot, S R



Increasing biogas production from sewage sludge anaerobic co-digestion process by adding crude glycerol from biodiesel industry.  


In an effort to convert waste streams to energy in a green process, glycerol from biodiesel manufacturing has been used to increase the gas production and methane content of biogas within a mesophilic anaerobic co-digestion process using primary sewage sludge. Glycerol was systematically added to the primary digester from 0% to 60% of the organic loading rate (OLR). The optimum glycerol loading range was from 25% to 60% OLR. This resulted in an 82-280% improvement in specific gas production. Following the feeding schedule described, the digesters remained balanced and healthy until inhibition was achieved at 70% glycerol OLR. This suggests that high glycerol loadings are possible if slow additions are upheld in order to allow the bacterial community to adjust properly. Waste water treatment plant operators with anaerobic digesters can use the data to increase loadings and boost biogas production to enhance energy conversion. This process provides a safe, environmentally friendly method to convert a typical waste stream to an energy stream of biogas. PMID:25249492

Nartker, Steven; Ammerman, Michelle; Aurandt, Jennifer; Stogsdil, Michael; Hayden, Olivia; Antle, Chad



Navigating wastewater energy recovery strategies: a life cycle comparison of anaerobic membrane bioreactor and conventional treatment systems with anaerobic digestion.  


The objective of this study was to evaluate emerging anaerobic membrane bioreactor (AnMBR) technology in comparison with conventional wastewater energy recovery technologies. Wastewater treatment process modeling and systems analyses were combined to evaluate the conditions under which AnMBR may produce more net energy and have lower life cycle environmental emissions than high rate activated sludge with anaerobic digestion (HRAS+AD), conventional activated sludge with anaerobic digestion (CAS+AD), and an aerobic membrane bioreactor with anaerobic digestion (AeMBR+AD). For medium strength domestic wastewater treatment under baseline assumptions at 15 °C, AnMBR recovered 49% more energy as biogas than HRAS+AD, the most energy positive conventional technology considered, but had significantly higher energy demands and environmental emissions. Global warming impacts associated with AnMBR were largely due to emissions of effluent dissolved methane. For high strength domestic wastewater treatment, AnMBR recovered 15% more net energy than HRAS+AD, and the environmental emissions gap between the two systems was reduced. Future developments of AnMBR technology in low energy fouling control, increased flux, and management of effluent methane emissions would make AnMBR competitive with HRAS+AD. Rapid advancements in AnMBR technology must continue to achieve its full economic and environmental potential as an energy recovery strategy for domestic wastewater. PMID:24742289

Smith, Adam L; Stadler, Lauren B; Cao, Ling; Love, Nancy G; Raskin, Lutgarde; Skerlos, Steven J



Growth of Chlorella vulgaris on sugarcane vinasse: the effect of anaerobic digestion pretreatment.  


Microalgae farming has been identified as the most eco-sustainable solution for producing biodiesel. However, the operation of full-scale plants is still limited by costs and the utilization of industrial and/or domestic wastes can significantly improve economic profits. Several waste effluents are valuable sources of nutrients for the cultivation of microalgae. Ethanol production from sugarcane, for instance, generates significant amounts of organically rich effluent, the vinasse. After anaerobic digestion treatment, nutrient remaining in such an effluent can be used to grow microalgae. This research aimed to testing the potential of the anaerobic treated vinasse as an alternative source of nutrients for culturing microalgae with the goal of supplying the biodiesel industrial chain with algal biomass and oil. The anaerobic process treating vinasse reached a steady state at about 17 batch cycles of 24 h producing about 0.116 m(3)CH4 kgCODvinasse (-1). The highest productivity of Chlorella vulgaris biomass (70 mg l(-1) day(-1)) was observed when using medium prepared with the anaerobic digester effluent. Lipid productivity varied from 0.5 to 17 mg l(-1) day(-1). Thus, the results show that it is possible to integrate the culturing of microalgae with the sugarcane industry by means of anaerobic digestion of the vinasse. There is also the advantageous possibility of using by-products of the anaerobic digestion such as methane and CO2 for sustaining the system with energy and carbon source, respectively. PMID:24013860

Marques, Sheyla Santa Isabel; Nascimento, Iracema Andrade; de Almeida, Paulo Fernando; Chinalia, Fábio Alexandre



[Enhancement for anaerobic digestion of sewage sludge pretreated by microwave and its combined processes ].  


To improve anaerobic digestion and dewatering of sludge, impacts of sludge pretreated by microwave (MW) and its combined processes on sludge anaerobic digestion and dewatering were investigated. The results showed that microwave and its combined processes could effectively enhance anaerobic sludge digestion. Not only the cumulative methane production in the test of the MW-H2O2-alkaline (0. 2) was increased by 13. 34% compared with the control, but also its methane production rate was much higher than that of the control. Compared with the single MW process, the addition of both H2O2 and alkaline enhanced the solubilization of particle COD( >0. 45 micron) , indicating that synergistically generated soluble organics were faster to biodegrade which resulted in the enhancement of anaerobic digestion. The MW-acid process was effective in improving sludge dewaterability, e. g. , Capillary Suction Time (CST) at only 9. 85 s. The improvement of sludge dewatering was significantly correlated with sludge physical properties such as zeta potential, surface charge density and particle size. Under different sludge pretreatment conditions, the sludge dewatering after anaerobic digestion was similar, though the difference of sludge dewatering to some degrees was observed for pretreated sludge. PMID:25518665

Liu, Ji-bao; Ni, Xiao-tang; Wei, Yuan-song; Tong, Juan; Wang, Ya-wei



Long-term anaerobic digestion of food waste stabilized by trace elements  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Korean food waste was found to contain low level of trace elements. Black-Right-Pointing-Pointer Stable anaerobic digestion of food waste was achieved by adding trace elements. Black-Right-Pointing-Pointer Iron played an important role in anaerobic digestion of food waste. Black-Right-Pointing-Pointer Cobalt addition further enhanced the process performance in the presence of iron. - Abstract: The purpose of this study was to examine if long-term anaerobic digestion of food waste in a semi-continuous single-stage reactor could be stabilized by supplementing trace elements. Contrary to the failure of anaerobic digestion of food waste alone, stable anaerobic digestion of food waste was achieved for 368 days by supplementing trace elements. Under the conditions of OLR (organic loading rates) of 2.19-6.64 g VS (volatile solid)/L day and 20-30 days of HRT (hydraulic retention time), a high methane yield (352-450 mL CH{sub 4}/g VS{sub added}) was obtained, and no significant accumulation of volatile fatty acids was observed. The subsequent investigation on effects of individual trace elements (Co, Fe, Mo and Ni) showed that iron was essential for maintaining stable methane production. These results proved that the food waste used in this study was deficient in trace elements.

Zhang Lei, E-mail: [Key Laboratory of Industrial Ecology and Environmental Engineering, School of Environmental Science and Technology, Dalian University of Technology, Linggong Road 2, Dalian 116024 (China); Jahng, Deokjin, E-mail: [Department of Environmental Engineering and Biotechnology, Myongji University, San 38-2, Namdong, Cheoin-Gu, Yongin, Gyeonggi-Do 449-728 (Korea, Republic of)



Effect of solids retention time on the bioavailability of organic carbon in anaerobically digested swine waste.  


Anaerobic digestion (AD) can be used to stabilize and produce energy from livestock waste; however, digester effluents may require further treatment to remove nitrogen. This paper quantifies the effects of varying solids retention time (SRT) methane yield, volatile solids (VS) reduction and organic carbon bioavailability for denitrification during swine waste AD. Four bench-scale anaerobic digesters, with SRTs of 14, 21, 28 and 42 days, operated with swine waste feed. Effluent organic carbon bioavailability was measured using anoxic microcosms and respirometry. Excellent performance was observed for all four digesters, with >60% VS removal and CH4 yields between 0.1 and 0.3(m(3)CH4)/(kg VS added). Organic carbon in the centrate as an internal organic carbon source for denitrification supported maximum specific denitrification rates between 47 and 56(mg NO3(-)-N)/(g VSS h). The digester with the 21-day SRT had the highest CH4 yield and maximum specific denitrification rates. PMID:24736207

Kinyua, Maureen N; Cunningham, Jeffrey; Ergas, Sarina J



Low-heat, mild alkaline pretreatment of switchgrass for anaerobic digestion.  


This study examines the effectiveness of alkaline pretreatment under mild heat conditions (100°C or 212°F) on the anaerobic co-digestion of switchgrass. The effects of alkaline concentration, types of alkaline, heating time and rinsing were evaluated. In addition to batch studies, continuous-feed studies were performed in triplicate to identify potential digester operational problems caused by switchgrass co-digestion while accounting for uncertainty due to digester variability. Few studies have examined anaerobic digestion of switchgrass or the effects of mild heating to enhance alkaline pretreatment prior to biomass digestion. Results indicate that pretreatment can significantly enhance digestion of coarse-ground (? 0.78 cm particle size) switchgrass. Energy conversion efficiency as high as 63% was observed, and was comparable or superior to fine-grinding as a pretreatment method. The optimal NaOH concentration was found to be 5.5% (wt/wt alkaline/biomass) with a 91.7% moisture level. No evidence of operational problems such as solids build-up, poor mixing, or floating materials were observed. These results suggest the use of waste heat from a generator could reduce the concentration of alkaline required to adequately pretreat lignocellulosic feedstock prior to anaerobic digestion. PMID:24410687

Jin, Guang; Bierma, Tom; Walker, Paul M




EPA Science Inventory

As part of studies undertaken to investigate the pathogen reducing capabilities of conventional sludge stabilization procedures, microbial reductions produced by mesophilic and thermophilic digestion at the Los Angeles Hyperion Plant were examined. Samples from the digester feed ...


Economic and environmental analysis of four different configurations of anaerobic digestion for food waste to energy conversion using LCA for: a food service provider case study.  


The US disposes of more than 34 million tons of food waste in landfills per year. As this food waste decomposes it generates methane gas and negatively contributes to global warming. Diverting theses organic food wastes from landfills and to emerging technologies will prevent these wastes and greenhouse gas emissions while at the same time generating a source renewable energy by collecting the emitted gases. From a waste prevention standpoint, instead of the food waste decomposing at local landfills, it is being converted into an energy source and the by-product may be used as a fertilizer (Fine and Hadas, 2012). The purpose of this study was to compare four different configurations of anaerobic digestion of organic waste to energy technologies from an economic, energy, and emissions standpoint using LCA via a case study at a large food services provider in Northwest Ohio, USA. The technologies studied included two-stage anaerobic digestion system using ultrasound pre-treating, two stage continuous combined thermophilic acidogenic hydrogenesis and mesophilic with recirculation of the digested sludge, long-term anaerobic digestion of food waste stabilized by trace elements, and single stage anaerobic digestion. Using LCA, these scenarios were compared to landfill disposal of the food waste. The findings from the case study indicated that implementing on-site waste to energy systems will result in lower operation costs and lower environmental impacts. In addition, a standardized environmental and economic comparison of competing food waste to energy technologies is provided. PMID:23583791

Franchetti, Matthew



Anaerobic digestion and gasification coupling for wastewater sludge treatment and recovery.  


Sewage sludge management is an energy intensive process. Anaerobic digestion contributes to energy efficiency improvement but is limited by the biological process. A review has been conducted prior to experimentation in order to evaluate the mass and energy balances on anaerobic digestion followed by gasification of digested sludge. The purpose was to improve energy recovery and reuse. Calculations were based on design parameters and tests that are conducted with the anaerobic digester of a local wastewater treatment plant and a small commercial gasification system. Results showed a very significant potential of energy recovery. More than 90% of the energy content from sludge was extracted. Also, approximately the same amount of energy would be transferred in both directions between the digester (biogas) and the gasifier (thermal energy). This extraction resulted in the same use of biogas as the reference scenario but final product was a totally dry biochar, which represented a fraction of the initial mass. Phosphorus was concentrated and significantly preserved. This analysis suggests that anaerobic digestion followed by dehydration, drying and gasification could be a promising and viable option for energy and nutrient recovery from municipal sludge in replacement of conventional paths. PMID:24972600

Lacroix, Nicolas; Rousse, Daniel R; Hausler, Robert



Comparative metagenomic analysis of bacterial populations in three full-scale mesophilic anaerobic manure digesters.  


While the use of anaerobic digestion to generate methane as a source of bioenergy is increasing worldwide, our knowledge of the microbial communities that perform biomethanation is very limited. Using next-generation sequencing, bacterial population profiles were determined in three full-scale mesophilic anaerobic digesters operated on dairy farms in the state of Vermont (USA). To our knowledge, this is the first report of a metagenomic analysis on the bacterial population of anaerobic digesters using dairy manure as their main substrate. A total of 20,366 non-chimeric sequence reads, covering the V1-V2 hypervariable regions of the bacterial 16S rRNA gene, were assigned to 2,176 operational taxonomic units (OTUs) at a genetic distance cutoff value of 5 %. Based on their limited sequence identity to validly characterized species, the majority of OTUs identified in our study likely represented novel bacterial species. Using a naïve Bayesian classifier, 1,624 anaerobic digester OTUs could be assigned to 16 bacterial phyla, while 552 OTUs could not be classified and may belong to novel bacterial taxonomic groups that have yet to be described. Firmicutes, Bacteroidetes, and Chloroflexi were the most highly represented bacteria overall, with Bacteroidetes and Chloroflexi showing the least and the most variation in abundance between digesters, respectively. All digesters shared 132 OTUs, which as a "core" group represented 65.4 to 70.6 % of sequences in individual digesters. Our results show that bacterial populations from microbial communities of anaerobic manure digesters can display high levels of diversity despite sharing a common core substrate. PMID:24085391

St-Pierre, Benoit; Wright, André-Denis G



Pharmaceutically active compounds in sludge stabilization treatments: anaerobic and aerobic digestion, wastewater stabilization ponds and composting.  


Sewage sludge disposal onto lands has been stabilized previously but still many pollutants are not efficiently removed. Special interest has been focused on pharmaceutical compounds due to their potential ecotoxicological effects. Nowadays, there is scarce information about their occurrence in different sludge stabilization treatments. In this work, the occurrence of twenty-two pharmaceutically active compounds has been studied in sludge from four sludge stabilization treatments: anaerobic digestion, aerobic digestion, composting and lagooning. The types of sludge evaluated were primary, secondary, anaerobically-digested and dehydrated, composted, mixed, aerobically-digested and dehydrated and lagoon sludge. Nineteen of the twenty-two pharmaceutically active compounds monitored were detected in sewage sludge. The most contaminated samples were primary sludge, secondary sludge and mixed sludge (the average concentrations of studied compounds in these sludges were 179, 310 and 142 ?g/kg dm, respectively) while the mean concentrations found in the other types of sewage sludge were 70 ?g/kg dm (aerobically-digested sludge), 63 ?g/kg dm (lagoon sludge), 12 ?g/kg dm (composted sludge) and 8 ?g/kg dm (anaerobically-digested sludge). The antibiotics ciprofloxacin and norfloxacin were found at the highest concentration levels in most of the analyzed sludge samples (up to 2660 and 4328 ?g/kg dm, respectively). Anaerobic-digestion treatment reduced more considerably the concentration of most of the studied compounds than aerobic-digestion (especially in the case of bezafibrate and fluoroquinolones) and more than anaerobic stabilization ponds (in the case of acetaminophen, atenolol, bezafibrate, carbamazepine, 17?-ethinylestradiol, naproxen and salicylic acid). Ecotoxicological risk assessment, of sludge application onto soils, has also been evaluated. Risk quotients, expressed as the ratio between the predicted environmental concentration and the predicted non-effect concentration, were lower than 1 for all the pharmaceutically active compounds so no significant risks are expected to occur due to the application of sewage sludge onto soils, except for 17?-ethinylestradiol when chronic toxicity was considered. PMID:24909712

Martín, Julia; Santos, Juan Luis; Aparicio, Irene; Alonso, Esteban



Treatment of municipal landfill leachate using a combined anaerobic digester and activated sludge system  

SciTech Connect

The main objective of this study was to assess the feasibility of treating sanitary landfill leachate using a combined anaerobic and activated sludge system. A high-strength leachate from Shiraz municipal landfill site was treated using this system. A two-stage laboratory-scale anaerobic digester under mesophilic conditions and an activated sludge unit were used. Landfill leachate composition and characteristics varied considerably during 8 months experiment (COD concentrations of 48,552-62,150 mg/L). It was found that the system could reduce the COD of the leachate by 94% at a loading rate of 2.25 g COD/L/d and 93% at loading rate of 3.37 g COD/L/d. The anaerobic digester treatment was quite effective in removing Fe, Cu, Mn, and Ni. However, in the case of Zn, removal efficiency was about 50%. For the rest of the HMs the removal efficiencies were in the range 88.8-99.9%. Ammonia reduction did not occur in anaerobic digesters. Anaerobic reactors increased alkalinity about 3.2-4.8% in the 1st digester and 1.8-7.9% in the 2nd digester. In activated sludge unit, alkalinity and ammonia removal efficiency were 49-60% and 48.6-64.7%, respectively. Methane production rate was in the range of 0.02-0.04, 0.04-0.07, and 0.02-0.04 L/g COD{sub rem} for the 1st digester, the 2nd digester, and combination of both digesters, respectively; the methane content of the biogas varied between 60% and 63%.

Kheradmand, S. [Department of Civil and Environmental Engineering, University of Shiraz, Shiraz 7134851156 (Iran, Islamic Republic of); Karimi-Jashni, A., E-mail: [Department of Civil and Environmental Engineering, University of Shiraz, Shiraz 7134851156 (Iran, Islamic Republic of); Sartaj, M. [Department of Civil Engineering, Isfahan University of Technology, Isfahan 841568311 (Iran, Islamic Republic of)



Blending anaerobic co-digestates: synergism and economics.  


Co-digestion is the process in which wastes from various sources are treated together. Therefore, more organic carbon is added to make efficient use of existing digesters. The objectives of this study were to compare potential co-digestates, determine synergistic and antagonistic co-digestion outcomes and estimate economic benefits for preliminary screening. Over 80 wastes were identified from 54 facilities within 160 km of an existing municipal digester. Synergistic, antagonistic and neutral co-digestion outcomes were observed for the various wastes. A simple economic comparison resulted in the greatest potential benefits for four co-digestates: yeast flavorings production waste, meat production dissolved air flotation float, acid whey from cheese production and thin stillage from corn ethanol production. Performance was investigated using bench-scale digesters receiving primary sludge with and without co-digestates. Methane production rates were 105 and 66% higher when co-digestates were present, but were anticipated to increase only 57 and 23% due to the additional chemical oxygen demand. Therefore, significant synergistic outcomes were observed during co-digestion. Co-digestion of the most promising wastes with primary sludge in full scale was estimated to generate enough electricity to power more than 2,500 houses. PMID:22049719

Navaneethan, N; Topczewski, P; Royer, S; Zitomer, D



Occurrence and reactivation of viable but non-culturable E. coli in sewage sludge after mesophilic and thermophilic anaerobic digestion.  


The occurrence and reactivation of viable but non-culturable (VBNC) Escherichia coli after different anaerobic digestions and the subsequent dewatering and storage were evaluated and compared. Culturable E. coli in digested sludge increased by two to four orders of magnitudes immediately after dewatering. However, counts of both the total and viable E. coli indicated that the increase of E. coli was attributed to its reactivation from the VBNC state to the culturable state. The VBNC pathogen incidences of thermophilic digestion were two to three orders of magnitude higher than those of mesophilic digestion. Accordingly, culturable E. coli in thermophilic, digested sludge after storage were one order of magnitude higher than mesophilic digestion. Anaerobic digestion thus mainly alters the culturable state of pathogens rather than killing them; therefore the biological safety of digested sludge, especially temperature-phased anaerobic digestion, should be carefully assessed. PMID:24101245

Fu, Bo; Jiang, Qian; Liu, Hongbo; Liu, He



Enhanced stabilization of digested sludge during long-term storage in anaerobic lagoons.  


The goal of this work was to study changes in anaerobically stored digested sludge under different lengths of storage time to evaluate the quality of final product biosolids. The analyses of collected data suggest the organic matter degradation occurrence in the anaerobic environment of the lagoon approximately within the first year. After that, the degradation becomes very slow, which is likely caused by unfavorable environmental conditions. The performance of lagoon aging of digested sludge was also compared to the performance of lagoon aging of anaerobically digested and dewatered sludge. It was concluded that both of these processes result in biosolids of comparative quality and that the former provides more economical solution to biosolids handling by eliminating the need for mechanical dewatering. PMID:24851324

Lukicheva, Irina; Pagilla, Krishna; Tian, Guanglong; Cox, Albert; Granato, Thomas



Monitoring bacterial community structure and variability in time scale in full-scale anaerobic digesters.  


Using a high-throughput pyrosequencing technology, this study assessed bacterial community structure and time-scale variability in great detail in seven full-scale anaerobic digesters operated variously in terms of influent substrate, digestion temperature, and reactor configuration. Pyrosequencing generated a total of 83,774 sequence reads from 40 digester sludge samples collected monthly for six months. The highest number of sequence reads were detected within Proteobacteria (20.5%), followed by those within Bacteroidetes (19.7%), Firmicutes (17.8%), and Chloroflexi (4.8%). The relative composition of bacterial populations was varied within the digesters as well as between the digesters, and the bacterial community structures were mainly influenced by digestion temperature. Detailed bacterial community structures were assessed by analyzing the operational taxonomic units (OTUs) based on 97% sequence similarity, which resulted in a total of 9051 OTUs. Among these, a total of 31 core OTUs were analyzed and inferred phylogenetically, which enabled us to classify the sequences within an unclassified phylum. Unclassified sequences were mostly affiliated with the sequences within Spirochaetes and Firmicutes. Interestingly, numerically dominant novel phylotypes (18% of the total sequence reads) presumably involved in anaerobic digestion within Spirochaetes were identified. Temporal variability was further explored using a non-metric multidimensional scaling ordination which demonstrated that the variability of the bacterial community within the digesters was smaller than between digesters. Correlation analysis demonstrated that digester performance and operational conditions affected the pattern of bacterial community in the ordination. Additionally, a multi-response permutation procedure revealed that the bacterial communities within the digesters were more similar than those belonging to other digesters statistically, demonstrating a patchiness of the digesters in the distribution of bacterial populations. Overall, this study revealed the correlation of bacterial community structure and time-scale variability with digester performance and operating conditions. PMID:22426622

Lee, Sang-Hoon; Kang, Hyun-Jin; Lee, Young Haeng; Lee, Taek Jun; Han, Keumsuk; Choi, Youngjun; Park, Hee-Deung



Anaerobic digestion for simultaneous sewage sludge treatment and CO biomethanation: process performance and microbial ecology.  


Syngas is produced by thermal gasification of both nonrenewable and renewable sources including biomass and coal, and it consists mainly of CO, CO2, and H2. In this paper we aim to bioconvert CO in the syngas to CH4. A novel technology for simultaneous sewage sludge treatment and CO biomethanation in an anaerobic reactor was presented. Batch experiments showed that CO was inhibitory to methanogens, but not to bacteria, at CO partial pressure between 0.25 and 1 atm under thermophilic conditions. During anaerobic digestion of sewage sludge supplemented with CO added through a hollow fiber membrane (HFM) module in continuous thermophilic reactors, CO did not inhibit the process even at a pressure as high as 1.58 atm inside the HFM, due to the low dissolved CO concentration in the liquid. Complete consumption of CO was achieved with CO gas retention time of 0.2 d. Results from high-throughput sequencing analysis showed clear differences of the microbial community structures between the samples from liquid and biofilm on the HFM in the reactor with CO addition. Species close to Methanosarcina barkeri and Methanothermobacter thermautotrophicus were the two main archaeal species involved in CO biomethanation. However, the two species were distributed differently in the liquid phase and in the biofilm. Although the carboxidotrophic activities test showed that CO was converted by both archaea and bacteria, the bacterial species responsible for CO conversion are unknown. PMID:23952148

Luo, Gang; Wang, Wen; Angelidaki, Irini



Should We Build “Obese” or “Lean” Anaerobic Digesters?  

PubMed Central

Conventional anaerobic digesters (ADs) treating dairy manure are fed with raw or fermented manure rich in volatile fatty acids (VFAs). In contrast, pre-fermented AD (PF-AD) is fed with the more recalcitrant, fiber-rich fraction of manure that has been pre-fermented and depleted of VFAs. Thus, the substrate of PF-AD may be likened to a lean diet rich in fibers while the pre-fermentation stage fermenter is fed a relatively rich diet containing labile organic substances. Previous results have shown that conventional and pre-fermented ADs fed with raw or pre-fermented manure, respectively, produced comparable methane yields. The primary objective of this study was to characterize, using next-generation DNA sequencing, the bacterial communities in various bioreactors (pre-fermentation stage fermenter; various operational arrangements PF-AD; conventional single-stage AD; and a full scale AD) and compare the Firmicutes to Bacteroidetes (F/B) ratios in these different systems. Firmicutes and Bacteroidetes constituted the two most abundant phyla in all AD samples analyzed, as well as most of the samples analyzed in the fermenters and manure samples. Higher relative abundance of Bacteroidetes, ranging from 26% to 51% of bacteria, tended to be associated with PF-AD samples, while the highest relative abundance of Firmicutes occurred in the fermenter (maximum of 76% of bacteria) and manure (maximum of 66% of bacteria) samples. On average, primary stage fermenters exhibited microbiological traits linked to obesity: higher F/B ratios and a ‘diet’ that is less fibrous and more labile compared to that fed to PF-AD. On the other hand, microbial characteristics associated with leanness (lower F/B ratios combined with fibrous substrate) were associated with PF-AD. We propose that bacterial communities in AD shift depending on the quality of substrate, which ultimately results in maintaining VFA yields in PF-AD, similar to the role of bacterial communities and a high fiber diet in lean mice. PMID:24831948

Briones, Aurelio; Coats, Erik; Brinkman, Cynthia



Performance of a two-phase anaerobic digestion system when treating dairy wastewater  

Microsoft Academic Search

Performance of a laboratory-scale two-phase anaerobic digestion system treating dairy wastewater was investigated using the pre-determined operating criteria for the anaerobic acidification reactor. The results, obtained from a 9month operation, showed that overall, 90% COD and 95% BOD removal efficiencies at an organic loading rate (OLR) of 5kg COD\\/m3d and a hydraulic retention time (HRT) of 2days were achieved. The

O. Ince



Potential errors in the quantitative evaluation of biogas production in anaerobic digestion processes.  


Errors that are commonly made in the quantification of biogas from anaerobic digestion experiments were investigated. For liquid displacement gasometers where a barrier solution separates the biogas and the atmosphere, inaccuracy due to gas diffusion was examined experimentally. Acidified saturated saline solution was the most suitable barrier solution, as biogas characteristics changed least with time. Using acidified or tap water caused considerable biogas losses and should therefore be avoided where biogas is stored before measurement. Errors associated with volume calculation from three common liquid displacement gasometer types were investigated theoretically. Corrections that must be made to obtain gas volumes at standard temperature and pressure when using this equipment are discussed. Regarding experimental errors, gasometer designs where displaced liquid is weighed to determine the volume are the most versatile since errors depend mainly upon balance sensitivity. Using liquid heights to calculate volume requires appropriate sizing of the gasometer relative to the volume of gas measured. The calibration of a low flow gas meter was investigated and an approximately linear variation with flow rate was found; hence in situ calibration is advised for this type of instrument. Correction for atmospheric conditions should be performed in real time to reduce errors. PMID:19660937

Walker, Mark; Zhang, Yue; Heaven, Sonia; Banks, Charles



Differences in volatile methyl siloxane (VMS) profiles in biogas from landfills and anaerobic digesters and energetics of VMS transformations.  


The objectives of this study were to compare the types and levels of volatile methyl siloxanes (VMS) present in biogas generated in the anaerobic digesters and landfills, evaluate the energetics of siloxane transformations under anaerobic conditions, compare the conditions in anaerobic digesters and municipal solid waste (MSW) landfills which result in differences in siloxane compositions. Biogas samples were collected at the South District Wastewater Treatment Plant and South Dade Landfill in Miami, Florida. In the digester gas, D4 and D5 comprised the bulk of total siloxanes (62% and 27%, respectively) whereas in the landfill gas, the bulk of siloxanes were trimethylsilanol (TMSOH) (58%) followed by D4 (17%). Presence of high levels of TMSOH in the landfill gas indicates that methane utilization may be a possible reaction mechanism for TMSOH formation. The free energy change for transformation of D5 and D4 to TMSOH either by hydrogen or methane utilization are thermodynamically favorable. Either hydrogen or methane should be present at relatively high concentrations for TMSOH formation which explains the high levels present in the landfill gas. The high bond energy and bond distance of the Si-O bond, in view of the atomic sizes of Si and O atoms, indicate that Si atoms can provide a barrier, making it difficult to break the Si-O bonds especially for molecules with specific geometric configurations such as D4 and D5 where oxygen atoms are positioned inside the frame formed by the large Si atoms which are surrounded by the methyl groups. PMID:25160660

Tansel, Berrin; Surita, Sharon C



Acute toxicity of pharmaceutical wastewaters containing antibiotics to anaerobic digestion treatment.  


In the present study, a method for prediction of the toxicity of pharmaceutical wastewaters containing antibiotics to microbial communities in anaerobic digestion treatment was developed. Luminescent bacterium assay was carried out with Vibrio fischeri as indicator. The individual and joint toxicities of antibiotics and anaerobic digestion metabolites were investigated by using the 15-min half inhibitory concentration (15 min-IC50) at pH 7.00±0.05. The results showed that the 15 min-IC50 of Amoxicillin, Kanamycin, Lincomycin and Ciprofloxacin were 3.99, 5.11, 4.32 and 5.63 g L(-1) respectively, and the toxicity descended in the order of Amoxicillin, Lincomycin, Kanamycin and Ciprofloxacin. Using equitoxic ratio mixing method, the joint toxicities of four anaerobic digestion intermediates, the four intermediates together with Amoxicillin, Ciprofloxacin, Kanamycin or Lincomycin were determined, which displayed that their interactions were additive, additive, synergistic, synergistic and synergistic respectively. Finally the joint effect of all intermediates and antibiotics was synergistic. The method has promising applications in evaluating the joint toxicity of anaerobic digestion intermediates and antibiotics, and has laid the foundations for assessing the feasibility of anaerobic treatment of pharmaceutical wastewater containing antibiotics. PMID:23415489

Ji, Jun-Yuan; Xing, Ya-Juan; Ma, Zi-Tao; Zhang, Meng; Zheng, Ping



Review of composting and anaerobic digestion of municipal solid waste and a methodological proposal for a mid-size city  

E-print Network

Review of composting and anaerobic digestion of municipal solid waste and a methodological proposal-Milwaukee, Milwaukee, WI, USA ABSTRACT: Composting industry is a progressive and innovative industry that has been and processes on composting and anaerobic digestion are compiled, showing the versatility and multivariable

Wisconsin-Milwaukee, University of



EPA Science Inventory

With the aim of the Phase I project to develop an innovative anaerobic co-digestion design for the treatment of dairy manure and poultry waste, our Phase I team has evaluated the technical and economic feasibility of the anaerobic co-digestion design concept with a thorough in...


Inoculum selection is crucial to ensure operational stability in anaerobic digestion.  


Anaerobic digestion is considered a key technology for the future bio-based economy. The microbial consortium carrying out the anaerobic digestion process is quite complex, and its exact role in terms of "elasticity", i.e., the ability to rapidly adapt to changing conditions, is still unknown. In this study, the role of the initial microbial community in terms of operational stability and stress tolerance was evaluated during a 175-day experiment. Five different inocula from stable industrial anaerobic digesters were fed a mixture of waste activated sludge and glycerol. Increasing ammonium pulses were applied to evaluate stability and stress tolerance. A different response in terms of start-up and ammonium tolerance was observed among the different inocula. Methanosaetaceae were the dominant acetoclastic methanogens, yet, Methanosarcinaceae increased in abundance at elevated ammonium concentrations. A shift from a Firmicutes to a Proteobacteria dominated bacterial community was observed in failing digesters. Methane production was strongly positively correlated with Methanosaetaceae, but also with Bacteria related to Anaerolinaceae, Clostridiales, and Alphaproteobacteria. Volatile fatty acids were strongly positively correlated with Betaproteobacteria and Bacteroidetes, yet ammonium concentration only with Bacteroidetes. Overall, these results indicate the importance of inoculum selection to ensure stable operation and stress tolerance in anaerobic digestion. PMID:25261127

De Vrieze, Jo; Gildemyn, Sylvia; Vilchez-Vargas, Ramiro; Jáuregui, Ruy; Pieper, Dietmar H; Verstraete, Willy; Boon, Nico



Contribution of Anaerobic Digesters to Emissions Mitigation and Electricity Generation Under U.S. Climate Policy  

PubMed Central

Livestock husbandry in the U.S. significantly contributes to many environmental problems, including the release of methane, a potent greenhouse gas (GHG). Anaerobic digesters (ADs) break down organic wastes using bacteria that produce methane, which can be collected and combusted to generate electricity. ADs also reduce odors and pathogens that are common with manure storage and the digested manure can be used as a fertilizer. There are relatively few ADs in the U.S., mainly due to their high capital costs. We use the MIT Emissions Prediction and Policy Analysis (EPPA) model to test the effects of a representative U.S. climate stabilization policy on the adoption of ADs which sell electricity and generate methane mitigation credits. Under such policy, ADs become competitive at producing electricity in 2025, when they receive methane reduction credits and electricity from fossil fuels becomes more expensive. We find that ADs have the potential to generate 5.5% of U.S. electricity. PMID:21761880



Phase distribution and removal of pharmaceuticals and personal care products during anaerobic sludge digestion.  


The fate and removal of 48 pharmaceuticals and personal care products (PPCPs) during anaerobic digestion of sewage sludge were investigated in four full-scale sewage treatment plants (STPs). We measured concentrations in both the liquid and solid phases of the sludge to compare the distribution ratios (Kd) between phases before and after digestion. The results showed changes in Kd values of PPCPs with carboxyl or amino functional groups, probably due to a shift of dissociation equilibrium with the increase in pH. Sulfamethoxazole and trimethoprim were almost completely degraded (>90%); triclosan, triclocarban, and ofloxacin were moderately degraded (around 30-50%); but carbamazepine was not eliminated. To our knowledge, this is the first report that shows (i) the occurrence and removal of several tens of PPCPs by anaerobic sludge digestion in full-scale municipal STPs and (ii) the change of distribution between the liquid and solid phases during digestion. PMID:23774781

Narumiya, Masanori; Nakada, Norihide; Yamashita, Naoyuki; Tanaka, Hiroaki



Biodegradation of pulp and paper mill effluent using anaerobic followed by aerobic digestion.  


An experimental study was carried to find out the degradability of black liquor of pulp and paper mill wastewater for biomethanogenesis in continuous stirred tank reactor (CSTR) and followed by activated sludge process (ASP). Continuous stirred tank reactor was used in present study for anaerobic digestion of black liquor, while completely mixed activated sludge system was used for aerobic digestion. A maximum methane production was found up to 430 ml/day, chemical oxygen demand was reduced up to 64% and total volatile fatty acid increased up to 1500 mg/l from 975 mg/l at 7.3 pH, 37 degrees C temperature and 8 days hydraulic retention time during anaerobic digestion. In activated sludge process (aerobic digestion) chemical oxygen demand and biological oxygen demand reduction were 81% and 86% respectively at 72 hr hydraulic retention time. PMID:17436533

Bishnoi, Narsi R; Khumukcham, R K; Kumar, Rajender



Continuous thermal hydrolysis and anaerobic digestion of sludge. Energy integration study.  


Experimental data obtained from the operation in a pilot plant are used to perform mass and energy balances to a global process combining units of thermal hydrolysis (TH) of secondary sludge, anaerobic digestion (AD) of hydrolysed secondary sludge together with fresh primary sludge, and cogeneration from biogas by using a gas engine in which the biogas produces electricity and heat from the exhaust gases. Three scenarios were compared, corresponding to the three digesters operated: C (conventional AD, 17 days residence time), B (combined TH + AD, same time), and A (TH + AD at half residence time). The biogas production of digesters B and A was 33 and 24% better, respectively when compared with C. In the case of the combined TH + AD process (scenarios A and B), the key factors in the energy balance were the recovery of heat from hot streams, and the concentration of sludge. The results of the balances showed that for 8% DS concentration of the secondary sludge tested in the pilot plant, the process can be energetically self-sufficient, but a fraction of the biogas must by-pass the gas engine to be directly burned. From an economic point of view, scenario B is more profitable in terms of green energy and higher waste removal, while scenario A reduces the digester volume required by a half. Considering a population of 100,000 inhabitants, the economic benefit is 87,600 €/yr for scenario A and 132,373 €/yr for B. This value can be increased to 223,867 €/yr by increasing the sludge concentration of the feeding to the TH unit to a minimum value that allows use of all the biogas to produce green energy. This concentration is 13% DS, which is still possible from a practical point of view. Additional benefits gained with the combined TH + AD process are the enhancement of the digesters rheology and the possibility of getting Class A biosolids. The integration study presented here set the basis for the scale-up to a demonstration plant. PMID:22546800

Pérez-Elvira, S I; Fdz-Polanco, F



Impact of alkaline-hydrolyzed biosolids (Lystek) addition on the anaerobic digestibility of TWAS in lab--and full-scale anaerobic digesters.  


The effect of different Lystek biosolids doses on the anaerobic digestability of thickened waste activated sludge (TWAS) was evaluated in a lab- and full-scale anaerobic digester. The overall findings of this study emphasize the beneficial impact of Lystek addition to the lab- and full-scale anaerobic digesters in terms of enhanced biogas production and increased volatile suspended solids reduction (VSSR) efficiency. Lystek added at 4% by volume to TWAS increased the methane yield from 0.22 to 0.26 L CH4/g VSSadded at an solids retention time (SRT) of 10 days, and from 0.27 to 0.29 L CH4/g VSS(added) at an SRT of 15 days. Furthermore, the VSSRs of 37% and 47% were observed for the TWAS, and the TWAS with 4% Lystek, while at an SRT of 15 days, the observed VSSR were 49% and 58%, respectively. The lab-scale study showed that the influence of Lystek addition on methane yield and solids destruction efficiencies was more pronounced at the shorter SRT, 20% enhancement (SRT of 10d) vs. 9% enhancement (SRT of 15 d) for methane yield, and 27% (SRT of 10d) vs. 22% (SRT of 15 d) for VSS destruction efficiency improvement. Furthermore, addition of 4% of Lystek to the feed of the full-scale anaerobic digester at St. Marys wastewater treatment plant (WWTP) resulted in a 50% increase in the average specific methanogenic activity and 23% increase in methane yield of the biochemical methane potential tests after eight months. The results showed that Lystek degradation kinetics were 40% faster than the TWAS, as reflected by first order kinetic coefficients of 0.053 d(-1) and 0.073 d(-1) for TWAS and Lystek at an SRT of 10 days. PMID:25154917

Elbeshbishy, Elsayed; Aldin, Saad; Nakhla, George; Singh, Ajay; Mullin, Bill



Comparison of different liquid anaerobic digestion effluents as inocula and nitrogen sources for solid-state batch anaerobic digestion of corn stover  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Compared methane production of solid AD inoculated with different effluents. Black-Right-Pointing-Pointer Food waste effluent (FWE) had the largest population of acetoclastic methanogens. Black-Right-Pointing-Pointer Solid AD inoculated with FWE produced the highest methane yield at F/E ratio of 4. Black-Right-Pointing-Pointer Dairy waste effluent (DWE) was rich of cellulolytic and xylanolytic bacteria. Black-Right-Pointing-Pointer Solid AD inoculated with DWE produced the highest methane yield at F/E ratio of 2. - Abstract: Effluents from three liquid anaerobic digesters, fed with municipal sewage sludge, food waste, or dairy waste, were evaluated as inocula and nitrogen sources for solid-state batch anaerobic digestion of corn stover in mesophilic reactors. Three feedstock-to-effluent (F/E) ratios (i.e., 2, 4, and 6) were tested for each effluent. At an F/E ratio of 2, the reactor inoculated by dairy waste effluent achieved the highest methane yield of 238.5 L/kgVS{sub feed}, while at an F/E ratio of 4, the reactor inoculated by food waste effluent achieved the highest methane yield of 199.6 L/kgVS{sub feed}. The microbial population and chemical composition of the three effluents were substantially different. Food waste effluent had the largest population of acetoclastic methanogens, while dairy waste effluent had the largest populations of cellulolytic and xylanolytic bacteria. Dairy waste also had the highest C/N ratio of 8.5 and the highest alkalinity of 19.3 g CaCO{sub 3}/kg. The performance of solid-state batch anaerobic digestion reactors was closely related to the microbial status in the liquid anaerobic digestion effluents.

Xu Fuqing; Shi Jian [Department of Food, Agricultural and Biological Engineering, Ohio State University, Ohio Agricultural Research and Development Center, 1680 Madison Ave., Wooster, OH 44691 (United States); Lv Wen; Yu Zhongtang [Department of Animal Sciences, Ohio State University, Columbus, OH 43210 (United States); Li Yebo, E-mail: [Department of Food, Agricultural and Biological Engineering, Ohio State University, Ohio Agricultural Research and Development Center, 1680 Madison Ave., Wooster, OH 44691 (United States)



Recovery of energy from Taro ( Colocasia esculenta) with solid-feed anaerobic digesters (SOFADs)  

Microsoft Academic Search

We present studies on solid-feed anaerobic digesters (SOFADs) in which chopped Colocasia esculenta was fed without any other pretreatment, in an attempt to develop an efficient means of utilizing the semi-aquatic weed that is otherwise an environmental nuisance.Two types of SOFADs were studied. The first type had a single vessel with two compartments. The lower portion of the digester, 25%

T. Bindu; E. V. Ramasamy



A hybrid anaerobic membrane bioreactor coupled with online ultrasonic equipment for digestion of waste activated sludge  

Microsoft Academic Search

Anaerobic membrane bioreactor and online ultrasonic equipment used to enhance membrane filtration were coupled to form a hybrid system (US-AnMBR) designed for long-term digestion of waste activated sludge. The US-AnMBR was operated under volatile solids loading rates of 1.1–3.7gVS\\/L·d. After comprehensive studies on digestion performance and membrane fouling control in the US-AnMBR, the final loading rate was determined to be

Meilan Xu; Xianghua Wen; Zhiyong Yu; Yushan Li; Xia Huang



[Research advances in anaerobic co-digestion of biogas fermentation substrates].  


With global climate change, more and more attention has been paid to the development of bio-energy. Biogas fermentation, as a fairly mature technology of bio-matter energy transformation, has received considerable attention and experienced much development. How to improve the efficiency of biogas fermentation and promote its industrialization is a pressing issue. Anaerobic co-digestion is a simple, low-cost, and high-efficiency method for enhancing the efficiency of biogas fermentation, and received increasing attention from related researchers. This paper summarized the characteristics of various fermentation substrates, reviewed the research advances in the co-digestion of animal manure, sewage sludge, and industrial waste, with the focus on the advantages of co-digestion and the factors affecting the rate and efficiency of co-digestion, and prospected the future research of co-digestion and its application, aimed to provide theoretical guidance for the promotion and application of co-digestion techniques. PMID:23173482

Dong, Fei-Qing; Li, Xia; Lu, Jian-Bo




EPA Science Inventory

This report describes the successful operation of a new and novel approach to digestion of sludge at the Hagerstown wastewater treatment plant. The process, known as dual digestion, involved the coupling of a full-scale experimental aerobic reactor to an existing full-scale anaer...


Lignocellulolytic enzyme activity, substrate utilization, and mushroom yield by Pleurotus ostreatus cultivated on substrate containing anaerobic digester solids  

Microsoft Academic Search

Solid waste from anaerobic digestion of litter from the commercial production of broiler chickens has limited use as fertilizer.\\u000a Its disposal is a major problem for digester operators who are seeking alternative use for anaerobic digester solids, also\\u000a referred to as solid waste (SW). The use of SW as substrates for the cultivation of Pleurotus ostreatus strain MBFBL400 was investigated.

Omoanghe S. Isikhuemhen; Nona A. Mikiashvilli



Principles and potential of the anaerobic digestion of waste-activated sludge  

Microsoft Academic Search

When treating municipal wastewater, the disposal of sludge is a problem of growing importance, representing up to 50% of the current operating costs of a wastewater treatment plant. Although different disposal routes are possible, anaerobic digestion plays an important role for its abilities to further transform organic matter into biogas (60–70vol% of methane, CH4), as thereby it also reduces the

Lise Appels; Jan Baeyens; Jan Degrève; Raf Dewil



Wastewater polishing by a channelized macrophyte-dominated wetland and anaerobic digestion of the harvested phytomass  

Technology Transfer Automated Retrieval System (TEKTRAN)

: Constructed wetlands (CW) offer a mechanism to meet regulatory standards for wastewater treatment while minimizing energy inputs. To optimize CW wastewater polishing activities and investigate integration of CW with energy production from anaerobic digestion we constructed a pair of three-tier ch...


Anaerobic digestion of saline creeping wild ryegrass for biogas production and pretreatment of particleboard material  

Microsoft Academic Search

The objective of this research was to develop an integrated process to produce biogas and high-quality particleboard using saline creeping wild ryegrass (CWR), Leymus triticoides through anaerobic digestion (AD). Besides producing biogas, AD also serves as a pretreatment method to remove the wax layer of CWR for improving binding capability and then the residue is used to produce high-quality particleboard.

Yi Zheng; Zhongli Pan; Ruihong Zhang; Hamed M. El-Mashad; Jinming Pan; Bryan M. Jenkins




Technology Transfer Automated Retrieval System (TEKTRAN)

The performance of continuously mixed anaerobic digesters was evaluated in the laboratory for treating manure, food waste and their mixtures at 35 ± 2oC and a hydraulic retention time of 20 days. The first mixture was composed of 32% and 68%, and the second was composed of 48% and 52% food waste and...


Evaluation of biochar-anaerobic potato digestate mixtures as renewable components of horticultural potting media  

Technology Transfer Automated Retrieval System (TEKTRAN)

Various formulations are used in horticultural potting media, with sphagnum peat moss, vermiculite and perlite currently among the most common components. We are examining a dried anaerobic digestate remaining after the fermentation of potato processing wastes to replace organic components such as p...


Anaerobic Digestion. Selected Instructional Activities and References. Instructional Resources Monograph Series.  

ERIC Educational Resources Information Center

Focusing specifically on the wastewater treatment process of anaerobic digestion, this document identifies instructional and reference materials for use by professionals in the field in the development and implementation of new programs or in the updating of existing programs. It is designed to help trainers, plant operators, educators, engineers,…

Townsend, Robert D., Comp.



EPA Science Inventory

The study evaluates the effects of enzyme augmentation on municipal wastewater (MWW) sludge anaerobic digestion. The primary objective was to examine the impact of using enzymes to enhance the degradation of the cellulosic and the oil- and grease-rich sludge fractions. The additi...


Anaerobic digestion potential for ecological and decentralised sanitation in urban areas.  


The potential of anaerobic digestion in ecological and decentralised sanitation has been investigated in this research. Different anaerobic digestion systems were proposed for the treatment of sewage, grey water, black water and faeces. Moreover, mathematical models based on anaerobic digestion model no.1 (ADM1) were developed for determination of a suitable design for each system. For stable performance of an upflow anaerobic sludge blanket (UASB) reactor treating sewage, the model results indicated that optimisation of wastewater conversion to biogas (not COD removal) should be selected for determination of the hydraulic retention time (HRT) of the reactor. For the treatment of sewage or black water in a UASB septic-tank, the model results showed that the sludge removal period was the main parameter for determination of the HRT. At such HRT, both COD removal and wastewater conversion are also optimised. The model results demonstrated that for treatment of faeces in an accumulation (AC) system at temperature > or = 25 degrees C, the filling period of the system should be higher than 60 days. For maximisation of the net biogas production (i.e. reduction of biogas losses as dissolved in the effluent), the separation between grey water, urine and faeces and reduction of water consumption for faeces flushing are required. Furthermore, the faeces and kitchen organic wastes and grey water are digested in, respectively, an AC system and UASB reactor, while the urine is stored. PMID:16841726

Elmitwalli, Tarek; Feng, Yucheng; Behrendt, Joachim; Otterpohl, Ralf



Minimisation of excess sludge production in a WWTP by coupling thermal hydrolysis and rapid anaerobic digestion.  


In many cases, reducing sludge production could be the solution for wastewater treatment plants (WWTP) that here difficulty evacuating the residuals of wastewater treatment. The aim of this study was to test the possibility of minimising the excess sludge production by coupling a thermal hydrolysis stage and an anaerobic digestion with a very short HRT. The tests were carried out on a 2,500 p.e. pilot plant installed on a recycling loop between the clarifier and the actived sludge basin. The line equipped with the full scale pilot plant produced 38% TSS less than the control line during a 10 week period. Moreover, the rapid anaerobic digestion removed, on average, more than 50% of the total COD load with a hydraulic retention time (HRT) of 3 days. Lastly, the dryness of the remaining excess sludge, sanitised by the thermal hydrolysis, was more than 35% with an industrial centrifuge. This combination of thermal hydrolysis and rapid anaerobic digestion equally permits a significant gain of compactness compared to traditional anaerobic digesters. PMID:16459799

Chauzy, J; Graja, S; Gerardin, F; Crétenot, D; Patria, L; Fernandes, P



Siting analysis of farm-based centralized anaerobic digester systems for distributed generation using GIS  

Microsoft Academic Search

There is growing interest in installing anaerobic digesters (ADs) on farms to use animal wastes as a biomass resource for both economic value and environmental benefit. This potential expansion prompts the need for land suitability assessment. In this paper, a GIS model is proposed for land-suitability assessment of potential energy systems featuring an AD coupled with an energy generator. A

Jianguo Ma; Norman R. Scott; Stephen D. DeGloria; Arthur J. Lembo



Performance of temperature-phased anaerobic digestion (TPAD) system treating dairy cattle wastes  

Microsoft Academic Search

The performance of temperature-phased anaerobic digestion (TPAD) system in the stabilization of dairy cattle wastes at high solids concentrations has never been evaluated, though the process has been established as a feasible alternative to conventional mesophilic processes for the treatment of municipal wastewater sludges. In this study, the TPAD system operating at a retention time of 14 days was subjected

Shihwu Sung; Harikishan Santha



Video Article Continuously-Stirred Anaerobic Digester to Convert Organic Wastes into  

E-print Network

Video Article Continuously-Stirred Anaerobic Digester to Convert Organic Wastes into Biogas: System, Bioenergy, Biogas, Methane, Organic Waste, Methanogenesis, Energy Crops, Date Published: // Citation: Usack Wastes into Biogas: System Setup and Basic Operation. J. Vis. Exp. (), e3978, DOI : 10

Angenent, Lars T.


Anaerobic Digestion of Saline Creeping Wild Ryegrass for Biogas Production and Pretreatment of Particleboard Material  

Technology Transfer Automated Retrieval System (TEKTRAN)

The objective of this research was to develop an integrated process to produce biogas and high-quality particleboard using saline creeping wild ryegrass (CWR), Leymus triticoides through anaerobic digestion (AD). Besides producing biogas, AD also serves as a pretreatment method to remove the wax la...


Testing the profitability of Anaerobic Digestion in a large-scale UK dairy farm   

E-print Network

Anaerobic Digestion (AD) consists in the transformation of any organic non-woody material by micro-organisms into biogas. This biogas, composed of approximately 60 per cent methane can be further burnt and converted into electricity and heat. The UK...

Coz Leniz, Luis Fernando



Improvement of anaerobic digester performance by wastewater recirculation through an aerated membrane.  

Technology Transfer Automated Retrieval System (TEKTRAN)

Swine wastewater from an anaerobic digester was recirculated through a silicone hose located in an external aeration chamber to determine its effect on wastewater malodorants and biogas composition. The silicone hose acted as a semipermeable membrane for the passage of small molecules. In the first...


Fungal pretreatment of albizia chips for enhanced biogas production by solid-state anaerobic digestion  

Technology Transfer Automated Retrieval System (TEKTRAN)

Albizia biomass is a forestry waste, and holds a great potential in biogas production by solid-state anaerobic digestion (SS-AD). However, low methane yields from albizia chips were observed due to their recalcitrant structure. In this study, albizia chips were pretreated by Ceriporiopsis subvermisp...


Anaerobic digestion of semi-solid organic waste: biogas production and its purification  

Microsoft Academic Search

The main objective of the present experimental investigation was to evaluate the effects of using different bacteria inoculums at identical technical settings on the anaerobic digestion process for the treatment of semi-solid organic waste available from the orthofruit market. As a possible means to improve the biogas production, as well as reduce their pollution potential, the idea of using recycled

G. Lastella; C. Testa; G. Cornacchia; M. Notornicola; F. Voltasio; Vinod Kumar Sharma



Test/QA Plan For Verification Of Anaerobic Digester For Energy Production And Pollution Prevention  

EPA Science Inventory

The ETV-ESTE Program conducts third-party verification testing of commercially available technologies that improve the environmental conditions in the U.S. A stakeholder committee of buyers and users of such technologies guided the development of this test on anaerobic digesters...


Utilization of Re-processed Anaerobically Digested Fiber from Dairy Manure as a Container Media Substrate  

Technology Transfer Automated Retrieval System (TEKTRAN)

The solid fraction (fiber) from the effluent of the anaerobic digestion of dairy manure by plug flow technology yields material that has consistent physical properties (total porosity, air filled porosity at saturation, and water holding capacity) to perform satisfactorily as a plant growth media su...


Water as a leaching medium for hydrolysis of sorghum in anaerobic digestion systems  

SciTech Connect

Laboratory experiments were conducted to determine the effect of using water to leach hydrolysis products from sorghum used as an anaerobic digestion feedstock. The pH of the leachate had no effect on the cumulative COD measured in the leachate. Milling the sorghum with a three roll mill prior to leaching appeared to slightly increase the hydrolysis of structural carbohydrates in the sorghum.

Egg, R.; Coble, C.G.



Optimizing the anaerobic digestion of microalgae in a coupled Terence Bayen  

E-print Network

of an optimal control problem governed by a system describing the coupling of a culture of micro-algae limited by light and an anaerobic digester. The mathematical model for the dynamics of the reactors takes into account a periodic day-night model of the light in the culture of micro-algae and a chemostat model

Paris-Sud XI, Université de


Performance evaluation of an anaerobic/aerobic landfill-based digester using yard waste for energy and compost production.  


The objective of this study was to evaluate a new alternative for yard waste management by constructing, operating and monitoring a landfill-based two-stage batch digester (anaerobic/aerobic) with the recovery of energy and compost. The system was initially operated under anaerobic conditions for 366 days, after which the yard waste was aerated for an additional 191 days. Off gas generated from the aerobic stage was treated by biofilters. Net energy recovery was 84.3MWh, or 46kWh per million metric tons of wet waste (as received), and the biochemical methane potential of the treated waste decreased by 83% during the two-stage operation. The average removal efficiencies of volatile organic compounds and non-methane organic compounds in the biofilters were 96-99% and 68-99%, respectively. PMID:22317795

Yazdani, Ramin; Barlaz, Morton A; Augenstein, Don; Kayhanian, Masoud; Tchobanoglous, George



Anaerobic digestion of municipal solid waste: Utility of process residues as a soil amendment  

SciTech Connect

Tuna processing wastes (sludges high in fat, oil, and grease [FOG]) and municipal solid waste (MSW) generated on Tutuila Island, American Samoa, represent an ongoing disposal challenge. The biological conversion of the organic fraction of these wastes to useful products, including methane and fertilizer-grade residue, through anaerobic high-solids digestion is currently in scale-up development. The suitability of the anaerobic digestion residues as a soil amendment was evaluated through extensive chemical analysis and greenhouse studies using corn as an indicator crop. Additionally, native Samoan soil was used to evaluate the specific application rates for the compost. Experiments established that anaerobic residues increase crop yields in direct proportion to increases in the application rate. Additionally, nutrient saturation was not demonstrated within the range of application rates evaluated for the Samoan soil. Beyond nutrient supplementation, organic residue amendment to Samoan soil imparts enhanced water and nutrient-binding capacities.

Rivard, C.J.; Nagle, N.J.; Kay, B.D. [National Renewable Energy Labs., Golden, CO (United States)] [and others



Thermophilic anaerobic digestion of livestock waste: the effect of ammonia  

Microsoft Academic Search

Ammonia concentrations of 4 g N\\/l or more inhibited thermophilic digestion of cattle manure. A stable digestion of cattle manure could be maintained with ammonia concentrations up to 6 g N\\/l after 6 months of operation. However, the methane yield was reduced and the concentration of volatile fatty acids increased from 1 to 3 g\\/l as acetate, compared to controls

I. Angelidaki; B. K. Ahring



Characterization and single-stage denitrification anaerobic digestion of spent stream from the hydrolysis-fermentation-combustion process  

NASA Astrophysics Data System (ADS)

The demand for ethanol as an oxygenate and octane booster in automobile fuel is growing. A number of processes are being investigated for conversion of biomass to ethanol. The Hydrolysis-Fermentation-Combustion (HFC) process for fuel ethanol production developed at the University of California Forest Products Laboratory, Richmond, California is at the stage of technology transfer following over two decades of research and development. This study addresses the technology to be used in treatment of spent streams to be discharged from this process. The treatment design combines a single stage denitrification and anaerobic digestion (SSDAD) for the biological treatment of a representative stream from this process. A typical spent stream contained a wide range of soluble organic materials including: unfermented sugars, components of the feedstocks solubilized in the hydrolysis, acid degradation products of carbohydrates, cleavage products of lignin, water-soluble extractives and phenolics, terpenes and other unfermented organic material, and nitrate ion from the nitric acid used as a catalyst in the hydrolysis reaction. Three sets of experiments were conducted in laboratory scale anaerobic digesters. Commonly available anaerobic sludge from local sewage treatment plants was used as a starter seed and was successfully acclimated to the high nitrate substrate leading to enrichment of denitrifiers. Necessary nutrients and trace elements were identified and supplied to satisfy the obligatory requirements of different groups of bacterial groups present. A major finding was the unique role of ammonium hydroxide in controlling pH leading to steady-state operation of the digester. At steady state operation the reduction in COD was 65%, the nitrate reduction was 88% and the nitrite reduction was 100%. Nitrate was reduced to safe nitrogen gas without buildup of any intermediate products. Organic material was converted to useful methane gas and carbon dioxide. The SSDAD system was shown to be effective in treating spent streams having high COD and nitrate concentrations.

Singh, Ramnik


[Effect of NaOH-treatment on dry-thermophilic anaerobic digestion of Spartina alterniflora].  


In order to improve the biotransformation rate of lignocellulosic materials, sodium hydroxide (NaOH) was widely used to pretreat lignocellulosic materials. Effect of NaOH-treatment on dry-thermophilic anaerobic digestion of Spartina alternflora was studied by batch model under the temperature of 55 degrees C +/- 1 degrees C, at the initial total solid loading (TSL) of 20%. The results indicated that biogas production was inhibited by NaOH-treatment and improved by NaOH-treatment with water washed. The cumulative biogas yield of control (CK), NaOH-treated and NaOH-treated with water washed (NaOH + water) were 268.35 mL/g, 205.76 mL/g and 299.97 mL/g, respectively. The methane content of CK and NaOH + water treatments kept stable while fluctuation of NaOH-treated treatment during anaerobic digestion process was observed. Compared with CK and NaOH + water treatments, methane content of NaOH-treated treatment was improved by 5.30%. The content of hemi-cellulose and cellulose of S. alternifora decreased while content of lignin of S. alterniflora increased after 51-day anaerobic digestion. The crystallinity of cellulose of S. alterniflora increased after NaOH-treatment which was consistent to the result of FTIR. The lignocellulosic structure was destroyed and the biodegradability of S. alterniflora was increased by NaOH pretreatment. However, the amount of Na+ was taken into the anaerobic system, besides the high Na+ content in the plant itself which inhibited the anaerobic microorganisms. Therefore, NaOH-treatment is considered to be unsuitable for the anaerobic digestion of S. alterniflora. PMID:21922846

Chen, Guang-Yin; Zheng, Zheng; Chang, Zhi-Zhou; Ye, Xiao-Mei; Luo, Yan




E-print Network

. The nutrients in anaerobically digested manure are sufficient for yeast fermentation, which means that the cost digested manure are sufficient for yeast fermentation, which means that the cost of SSF can be reduced digested manure could instead be a cheap medium for bioethanol fermentation in combination with suitable


Anaerobic digestion of ice-cream wastewater: A comparison of single and two-phase reactor systems  

SciTech Connect

The anaerobic digestion of ice-cream wastewater, a complex substrate which includes milk proteins, carbohydrates, and lipids, has received little attention. Work using an aerobic contact system showed that at a 7.5-d hydraulic retention time (HRT), with an organic loading rate of 1.7 g COD/Ld and influent TSS (total suspended solids) of 5870 mg/L, the effluent COD was 628 mg/L, BOD was 91 mg/L and TSS was 674. Anaerobic filters have also been used at organic loadings of 6 kg COD/m{sup 3}d applied at a HRT of 0.42 day, with COD removals of 80%. Goodwing showed that this waste was capable of being treated by the UASB process with granulation commencing after 60-70 days, and gas production ranging between 0.73 and 0.93 L CH{sub 4}/g COD removed with loading rates between 0.7 and 3.0 g TOC/Ld. Two-phase anaerobic digestion is an innovative fermentation mode that has recently received increased attention. The kinetically dissimilar fermentation phases, hydrolysis-acidification and acetogenesis-methanation are operated in two separate reactors; the first of which is maintained at a very short HRT. The effluent from the first, acid-forming, phase is used as the substrate for the methane-phase reactor which has a longer HRT or cell immobilization. The aim of this work was to compare the methane production capability and performance of a single-phase upflow fixed bed reactor with a two-phase digestion system. The two-phase digestion system consists of a completely mixed reactor for the acidogenic reaction and an upflow fixed bed reactor for the methanogenic reaction. Because of the high lipid content and COD of ice cream wastewater off site disposal has proved to be both expensive and poses problems to the receiving effluent treatment plant. For this reason the potential for a rapid anaerobic stabilization of the waste, with energy recovery in the form of methane gas, has been investigated in an attempt to minimize plant size and maximize gas production. 9 refs., 2 tabs.

Borja, R. [Institute of Fat and Its Derivatives (C.S.I.C.), Sevilla (Spain); Banks, C.J. [Environmental Technology Centre, Manchester (United Kingdom)



Anaerobic co-digestion of chicken manure and corn stover in batch and continuously stirred tank reactor (CSTR).  


Anaerobic co-digestion of chicken manure and corn stover in batch and CSTR were investigated. The batch co-digestion tests were performed at an initial volatile solid (VS) concentration of 3gVS/L, carbon-to-nitrogen (C/N) ratio of 20, and retention time of 30d. The methane yield was determined to be 281±12mL/gVSadded. Continuous reactor was carried out with feeding concentration of 12% total solids and C/N ratio of 20 at organic loading rates (OLRs) of 1-4gVS/L/d. Results showed that at OLR of 4gVS/L/d, stable and preferable methane yield of 223±7mL/gVSadded was found, which was equal to energy yield (EY) of 8.0±0.3MJ/kgVSadded. Post-digestion of digestate gave extra EY of 1.5-2.6MJ/kgVSadded. Pyrolysis of digestate provided additional EY of 6.1MJ/kgVSadded. Pyrolysis can be a promising technique to reduce biogas residues and to produce valuable gas products simultaneously. PMID:24531118

Li, Yeqing; Zhang, Ruihong; He, Yanfeng; Zhang, Chenyu; Liu, Xiaoying; Chen, Chang; Liu, Guangqing



Microbial Ecology in Anaerobic Digestion at Agitated and Non-Agitated Conditions  

PubMed Central

To investigate the distribution and dynamics of microbial community in anaerobic digestion at agitated and non-agitated condition, 454 pyrosequencing of 16s rRNA was conducted. It revealed the distinct community compositions between the two digesters and their progressive shifting over time. Methanogens and syntrophic bacteria were found much less abundant in the agitated digester, which was mainly attributed to the presence of bacterial genera Acetanaerobacterium and Ruminococcus with relatively high abundance. The characterization of the microbial community corroborated the digestion performance affected at the agitated condition, where lower methane yield and delayed methane production rate were observed. This was further verified by the accumulation of propionic acid in the agitated digester. PMID:25313520

Tian, Zhuoli; Cabrol, Léa; Ruiz-Filippi, Gonzalo; Pullammanappallil, Pratap



Controlling the pH of acid cheese whey in a two-stage anaerobic digester with sodium hydroxide  

SciTech Connect

Anaerobic digestion of cheese whey offers a two-fold benefit: pollution potential reduction and biogas production. The biogas, as an energy source, could be used to reduce the consumption of traditional fuels in the cheese plant. However, as a result of little or no buffering capacity of whey, the pH of the anaerobic digester drops drastically and the process is inhibited. In this study, the effect of controlling the pH of the second chamber of a two-stage, 150 L anaerobic digester operating on cheese whey on the quality and quantity of biogas and the pollution potential reduction, was investigated using sodium hydroxide. The digester was operated at a temperature of 35 C and a hydraulic retention time of 15 days for three runs (no pH control, pH control with no reseeding, and ph control with reseeding) each lasting 50 days. The results indicated that operating the digester without pH control resulted in a low pH (3.3) which inhibited the methanogenic bacteria. The inhibition was irreversible and the digester did not recover (no methane production) when the pH was restored to 7.0 without reseeding, as the observed increased gas production was a false indication of recovery because the gas was mainly carbon dioxide. The addition of base resulted in a total alkalinity of 12,000 mg/L as CaCO{sub 3}. When the system was reseeded and the pH controlled, the total volatile acid concentration was 15,100 mg/L (as acetic acid), with acetic (28%), propionic (21%), butyric (25%), valeric (8%), and caproic (15%) acids as the major constituents. The biogas production was 62.6 L/d (0.84 m{sup 3}/m{sup 3}/d) and the methane content was 60.7%. Reductions of 27.3, 30.4 and 23.3% in the total solids, chemical oxygen demand and total kjeldahl nitrogen were obtained, respectively. The ammonium nitrogen content increased significantly (140%).

Ghaly, A.E.; Ramkumar, D.R. [Dalhousie Univ., Halifax, Nova Scotia (Canada). Biological Engineering Dept.



Model-based predictions of anaerobic digestion of agricultural substrates for biogas production.  


A modified Anaerobic Digestion Model No. 1 (ADM1), calibrated on a laboratory digester with a feeding mix of 30% weight of cow manure and 70% weight of corn silage, was implemented, showing its performances of simulation as a decision-making and planning-supporting tool for the anaerobic digestion of agricultural substrates. The virtual fermenter obtained was used to conduct simulations with different feeding compositions and loading rates of cow manure, corn silage, grass silage and rape oil. All simulations were started at the same initial state which was represented by a steady state with an organic loading rate of 2.5 kg ODM/(mdigester3?d). The effects of the different feeding combinations on biogas composition and biogas yield were predicted reasonably, and partly verified with the available literature data. Results demonstrated that the simulations could be helpful for taking decisions on agricultural biogas plant operation or experimental set-ups, if used advisedly. PMID:21974886

Zhou, Haidong; Löffler, Daniel; Kranert, Martin



Anaerobic digestion of municipal solid waste: Analysis of cellulose biodegradative power  

SciTech Connect

Anaerobic digestion of municipal solid waste (MSW) represents a waste disposal option which results in the production of a gaseous fuel (methane) and an organic residue suitable for use as a soil amendment. The rate limiting step in this process is the hydrolysis of polymeric substrates such as cellulose. Analysis of digester sludge resident cellulase enzyme activity will be discussed. Cellulase enzyme activities are removed from sludge solids by a detergent extraction protocol. The analysis of discrete cellulase activities was accomplished using non-denaturing gel electrophoresis and Zymogram activity staining for CMC activity. Preliminary isolations of discrete cellulase activities from anaerobic digester sludge was performed by preparation isoelectric focussing using the Rainin RF-3 system.

Rivard, C.J.; Nagle, N.J.; Nieves, R.A.; Himmel, M.E. [National Renewable Energy Lab., Golden, CO (United States)



Benefits of supplementing an industrial waste anaerobic digester with energy crops for increased biogas production  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer This study demonstrates the feasibility of co-digestion food industrial waste with energy crops. Black-Right-Pointing-Pointer Laboratory batch co-digestion led to improved methane yield and carbon to nitrogen ratio as compared to mono-digestion of industrial waste. Black-Right-Pointing-Pointer Co-digestion was also seen as a means of degrading energy crops with nutrients addition as crops are poor in nutrients. Black-Right-Pointing-Pointer Batch co-digestion methane yields were used to predict co-digestion methane yield in full scale operation. Black-Right-Pointing-Pointer It was concluded that co-digestion led an over all economically viable process and ensured a constant supply of feedstock. - Abstract: Currently, there is increasing competition for waste as feedstock for the growing number of biogas plants. This has led to fluctuation in feedstock supply and biogas plants being operated below maximum capacity. The feasibility of supplementing a protein/lipid-rich industrial waste (pig manure, slaughterhouse waste, food processing and poultry waste) mesophilic anaerobic digester with carbohydrate-rich energy crops (hemp, maize and triticale) was therefore studied in laboratory scale batch and continuous stirred tank reactors (CSTR) with a view to scale-up to a commercial biogas process. Co-digesting industrial waste and crops led to significant improvement in methane yield per ton of feedstock and carbon-to-nitrogen ratio as compared to digestion of the industrial waste alone. Biogas production from crops in combination with industrial waste also avoids the need for micronutrients normally required in crop digestion. The batch co-digestion methane yields were used to predict co-digestion methane yield in full scale operation. This was done based on the ratio of methane yields observed for laboratory batch and CSTR experiments compared to full scale CSTR digestion of industrial waste. The economy of crop-based biogas production is limited under Swedish conditions; therefore, adding crops to existing industrial waste digestion could be a viable alternative to ensure a constant/reliable supply of feedstock to the anaerobic digester.

Nges, Ivo Achu, E-mail: [Department of Biotechnology, Lund University, P.O. Box 124, SE 221 00 Lund (Sweden); Escobar, Federico; Fu Xinmei; Bjoernsson, Lovisa [Department of Biotechnology, Lund University, P.O. Box 124, SE 221 00 Lund (Sweden)



Modeling of simultaneous denitrification--anaerobic digestion--organic matter aerobic oxidation and nitrification in an anoxic-anaerobic-aerobic compact filter reactor.  


A mathematical model was developed for a compact anoxic-anaerobic-aerobic filter reactor with liquid recirculation for the treatment of fishing effluents. The model includes denitrification, anaerobic digestion, aerobic carbon oxidation and nitrification steps, as well as an evaluation of the liquid gas mass transfer and pH. The model was calibrated using one experimental condition at a recycling ratio (R)=10, and was validated with R equal to 2 and 0, with an organic concentration of 554±24 mg TOCL(-1), salinity of 24 g L(-1) and hydraulic retention time (HRT) of 2 d. Carbon total removal is higher than 98%, while maximum nitrogen removal is 62% using total nitrification in the aerobic zone, due to a higher quantity of NO(x) produced which were recirculated to the anoxic zone. In the aerobic zone, simultaneous nitrification and denitrification processes occur, because the diffusion limitations cause a low oxygen penetration in the biofilm. In the anoxic-anaerobic zone, denitrification or methanogenesis inhibition by DO (caused by the recycled oxygen) is not observed. PMID:22475573

Moya, Jaime; Huiliñir, César; Peredo, Karol; Aspé, Estrella; Roeckel, Marlene



Anaerobic digester foaming in full-scale cylindrical digesters--effects of organic loading rate, feed characteristics, and mixing.  


Cylindrical anaerobic digesters (AD) were investigated to determine the causes and contributors of AD foaming due to the following: organic loading rate (OLR) and mixing effects, waste activated sludge (WAS) storage effects and foam suppression mixing at the surface of AD, and the effects of primary sludge (PS) solids fraction in the feed sludge. No foaming was observed over the duration of the study, indicating absence of a primary foaming cause even though the suspected contributors to AD foaming were present. Total solids and temperature profiles showed that reducing mixing frequency did not significantly impact digester performance or the homogeneity of the digester contents. The results showed that high organic loading rates, reduced mixing, and feed sludge storage by themselves do not cause foaming in most ADs when the primary foaming cause is absent. Reduced mixing and surface sludge sprays are practical strategies to control AD foaming. PMID:24650532

Subramanian, Bhargavi; Pagilla, Krishna R



Impact of PCB-118 and transformer oil toxicity on anaerobic digestion of sludge: anaerobic toxicity assay results.  


In this study, possible toxicity of increasing doses of PCB-118 and transformer oil (TO) on anaerobic sludge digestion was investigated. For this purpose, five different sets of reactors were prepared in which four different PCB-118 concentration (1, 10, 20, and 30mgL(-1)) and three different TO concentration (0.38, 0.76, and 1.52gL(-1)) were applied. Throughout the study, biogas production and composition, pH, TS, VS, and COD as well as PCB concentration were monitored. Toxicity was investigated by anaerobic toxicity assay (ATA) evaluating the reduction in methane production. A notable inhibition was observed mostly in 30mgL(-1) PCB reactors. A negative influence of PCB-118 and TO was observed on COD and solids removal. A maximum of 26.5% PCB-118 removal was attained. PMID:23683868

Kaya, Devrim; Imamoglu, Ipek; Dilek Sanin, F




EPA Science Inventory

The objectives of this laboratory investigation were to gain an understanding of the decomposition of milled refuse under anaerobic conditions, the rates of decomposition, and the gas production and composition. The rates of decomposition of cellulose and cellulosic materials, ga...


The effectiveness of anaerobic digestion in removing estrogens and nonylphenol ethoxylates.  


The fate and behaviour of two groups of endocrine disrupting chemicals, steroid estrogens and nonylphenol ethoxylates, have been evaluated during the anaerobic digestion of primary and mixed sewage sludge under mesophilic and thermophilic conditions. Digestion occurred over six retention times, in laboratory scale reactors, treating sludges collected from a sewage treatment works in the United Kingdom. It has been established that sludge concentrations of both groups of compounds demonstrated temporal variations and that concentrations in mixed sludge were influenced by the presence of waste activated sludge as a result of transformations during aerobic treatment. The biodegradation of total steroid estrogens was >50% during primary sludge digestion with lower removals observed for mixed sludge, which reflected bulk organic solids removal efficiencies. The removal of nonylphenol ethoxylates was greater in mixed sludge digestion (>58%) compared with primary sludge digestion and did not reflect bulk organic removal efficiencies. It is apparent that anaerobic digestion reduces the concentrations of these compounds, and would therefore be expected to confer a degree of protection against exposure and transfer of both groups of compounds to the receiving/re-use environment. PMID:22119197

Paterakis, N; Chiu, T Y; Koh, Y K K; Lester, J N; McAdam, E J; Scrimshaw, M D; Soares, A; Cartmell, E




Microsoft Academic Search

A stable anaerobic degradation of swine manure with ammonia concentration of 6 g-N\\/litre was obtained in continuously stirred tank reactors with a hydraulic retention time of 15 days, at four different temperatures. Methane yields of 188, 141, 67 and 22 ml-CH4\\/g-VS were obtained at 37, 45, 55 and 60°C, respectively. The yields were significantly lower than the potential biogas yield




Chemically pretreating slaughterhouse solid waste to increase the efficiency of anaerobic digestion.  


The combined effect of temperature and pretreatment of the substrate on the anaerobic treatment of the organic fraction of slaughterhouse solid waste was studied. The goal of the study was to evaluate the effect of pretreating the waste on the efficiency of anaerobic digestion. The effect was analyzed at two temperature ranges (the psychrophilic and the mesophilic ranges), in order to evaluate the effect of temperature on the performance of the anaerobic digestion process for this residue. The experiments were performed in 6 L batch reactors for 30 days. Two temperature ranges were studied: the psychrophilic range (at room temperature, 18°C average) and the mesophilic range (at 37°C). The waste was pretreated with NaOH before the anaerobic treatment. The result of pretreating with NaOH was a 194% increase in the soluble chemical oxygen demand (COD) with a dose of 0.6 g NaOH per g of volatile suspended solids (VSS). In addition, the soluble chemical oxygen demand/total chemical oxygen demand ratio (sCOD/tCOD) increased from 0.31 to 0.7. For the anaerobic treatment, better results were observed in the mesophilic range, achieving 70.7%, 47% and 47.2% removal efficiencies for tCOD, total solids (TS), and volatile solids (VS), respectively. PMID:24794850

Flores-Juarez, Cyntia R; Rodríguez-García, Adrián; Cárdenas-Mijangos, Jesús; Montoya-Herrera, Leticia; Godinez Mora-Tovar, Luis A; Bustos-Bustos, Erika; Rodríguez-Valadez, Francisco; Manríquez-Rocha, Juan




Technology Transfer Automated Retrieval System (TEKTRAN)

Laboratory-scale digesters were operated to study the effect of mixing (via biogas recirculation, impeller mixing, and slurry recirculation) on biogas production. Three sets of experiments were performed using cow manure slurry feed with either 50, 100, or 150 g/L total solids (TS) concentrations (r...


Semi-continuous anaerobic co-digestion of cow manure and steam-exploded Salix with recirculation of liquid digestate.  


The effects of recirculating the liquid fraction of the digestate during mesophilic anaerobic co-digestion of steam-exploded Salix and cow manure were investigated in laboratory-scale continuously stirred tank reactors. An average organic loading rate of 2.6 g VS L(-1) d(-1) and a hydraulic retention time (HRT) of 30 days were employed. Co-digestion of Salix and manure gave better methane yields than digestion of manure alone. Also, a 16% increase in the methane yield was achieved when digestate was recirculated and used instead of water to dilute the feedstock (1:1 dilution ratio). The reactor in which the larger fraction of digestate was recirculated (1:3 dilution ratio) gave the highest methane yields. Ammonia and volatile fatty acids did not reach inhibitory levels, and some potentially inhibitory compounds released during steam explosion (i.e., furfural and 5-hydroxy methyl furfural) were only detected at trace levels throughout the entire study period. However, accumulation of solids, which was more pronounced in the recycling reactors, led to decreased methane yields in those systems after three HRTs. Refraining from the use of fresh water to dilute biomass with a high-solids content and obtaining a final digestate with increased dry matter content might offer important economic benefits in full-scale processes. To ensure long-term stability in such an approach, it would be necessary to optimize separation of the fraction of digestate to be recirculated and also perform proper monitoring to avoid accumulation of solids. PMID:24534902

Estevez, Maria M; Sapci, Zehra; Linjordet, Roar; Schnürer, Anna; Morken, John



Evaluation of Integrated Anaerobic Digestion and Hydrothermal Carbonization for Bioenergy Production  

PubMed Central

Lignocellulosic biomass is one of the most abundant yet underutilized renewable energy resources. Both anaerobic digestion (AD) and hydrothermal carbonization (HTC) are promising technologies for bioenergy production from biomass in terms of biogas and HTC biochar, respectively. In this study, the combination of AD and HTC is proposed to increase overall bioenergy production. Wheat straw was anaerobically digested in a novel upflow anaerobic solid state reactor (UASS) in both mesophilic (37 °C) and thermophilic (55 °C) conditions. Wet digested from thermophilic AD was hydrothermally carbonized at 230 °C for 6 hr for HTC biochar production. At thermophilic temperature, the UASS system yields an average of 165 LCH4/kgVS (VS: volatile solids) and 121 L CH4/kgVS at mesophilic AD over the continuous operation of 200 days. Meanwhile, 43.4 g of HTC biochar with 29.6 MJ/kgdry_biochar was obtained from HTC of 1 kg digestate (dry basis) from mesophilic AD. The combination of AD and HTC, in this particular set of experiment yield 13.2 MJ of energy per 1 kg of dry wheat straw, which is at least 20% higher than HTC alone and 60.2% higher than AD only. PMID:24962786

Reza, M. Toufiq; Werner, Maja; Pohl, Marcel; Mumme, Jan



Methane and nitrous oxide emissions following anaerobic digestion of sludge in Japanese sewage treatment facilities.  


Methane (CH4) and nitrous oxide (N2O) are potent greenhouse gases with global warming potentials (expressed in terms of CO2-equivalents) of 28 and 265, respectively. When emitted to the atmosphere, they significantly contribute to climate change. It was previously suggested that in wastewater treatment facilities that apply anaerobic sludge digestion, CH4 continues to be emitted from digested sludge after leaving the anaerobic digester. This paper studies the CH4 and N2O emissions from anaerobically digested sludge in the subsequent sludge treatment steps. Two full-scale treatment plants were monitored over a 1-year period. Average emissions of CH4 and N2O were 509±72 mg/m(3)-influent (wastewater) and 7.1±2.6 mg/m(3)-influent, respectively. These values accounted for 22.4±3.8% of the indirect reduction in CO2-emissions when electricity was generated using biogas. They are considered to be significant. PMID:25194911

Oshita, Kazuyuki; Okumura, Takuya; Takaoka, Masaki; Fujimori, Takashi; Appels, Lise; Dewil, Raf



Effect of the chlortetracycline addition method on methane production from the anaerobic digestion of swine wastewater.  


Effects of antibiotic residues on methane production in anaerobic digestion are commonly studied using the following two antibiotic addition methods: (1) adding manure from animals that consume a diet containing antibiotics, and (2) adding antibiotic-free animal manure spiked with antibiotics. This study used chlortetracycline (CTC) as a model antibiotic to examine the effects of the antibiotic addition method on methane production in anaerobic digestion under two different swine wastewater concentrations (0.55 and 0.22mg CTC/g dry manure). The results showed that CTC degradation rate in which manure was directly added at 0.55mg CTC/g (HSPIKE treatment) was lower than the control values and the rest of the treatment groups. Methane production from the HSPIKE treatment was reduced (p<0.05) by 12% during the whole experimental period and 15% during the first 7days. The treatments had no significant effect on the pH and chemical oxygen demand value of the digesters, and the total nitrogen of the 0.55mg CTC/kg manure collected from mediated swine was significantly higher than the other values. Therefore, different methane production under different antibiotic addition methods might be explained by the microbial activity and the concentrations of antibiotic intermediate products and metabolites. Because the primary entry route of veterinary antibiotics into an anaerobic digester is by contaminated animal manure, the most appropriate method for studying antibiotic residue effects on methane production may be using manure from animals that are given a particular antibiotic, rather than adding the antibiotic directly to the anaerobic digester. PMID:25288543

Huang, Lu; Wen, Xin; Wang, Yan; Zou, Yongde; Ma, Baohua; Liao, Xindi; Liang, Juanboo; Wu, Yinbao



Anaerobic Digester Systems for Mid-Sized Dairy FarmsEXECUTIVE SUMMARY  

E-print Network

Six options for anaerobic digestion of animal manure on mid-sized dairy farms in Minnesota have been presented to provide dairy farm operators with information needed to make decisions about odor control and manure management technology. Information for each option is presented with schematics of the system, an explanation of how the system functions, the environmental benefits and lessons learned from other similar digesters. Capital costs for the installation of the digesters and yearly costs are presented. The expected benefits from odor control and use of separated solids are presented for a 100-cow dairy. Scale up information for 200-cow and 300-cow dairies are included as a multiplier factor. There are also answers to the questions “who should consider a system like this? ” and “why would a farmer install this digester? ” Resources are provided with who to contact about similar digesters and additional references relevant to each design. The generation of energy is discussed in a separate section. The six options applied to mid-sized farms do not produce excess energy beyond the energy needed to heat the digester during the winter months. Adding capacity and electrical generators would be an upgrade to the digester after experience was gained with the digestion system.

unknown authors


Foam formation in biogas plants caused by anaerobic digestion of sugar beet.  


The use of sugar beet in anaerobic digestion (AD) during biogas production can lead to process upsets such as excessive foaming in fermenters. In the present study, foam formation in sugar beet-fed digestates was studied in foaming tests. The increasing disintegration grade of sugar beet was observed to have a promoting effect on foaming in the digestate but did not affect the biogas yield. Chemical analysis of foam and digestate from sugar beet silage AD showed high concentrations of pectin, other carbohydrates and N-containing substances in the foam. Both pectin and sucrose showed little foaming in AD. Nevertheless, sucrose and calcium chloride had a promoting effect on foaming for pectin AD. Salts of divalent ions also enhanced the foam intensity in the case of sugar beet silage AD, whereas ammonium chloride and urea had a lessening effect on sugar beet-based foaming. PMID:25446785

Moeller, Lucie; Lehnig, Marcus; Schenk, Joachim; Zehnsdorf, Andreas



Comparison of mechanical pretreatment methods for the enhancement of anaerobic digestion of pulp and paper waste activated sludge.  


The conventional anaerobic digestion process, requiring long solids retention times (SRTs) to digest solids, is currently viewed as impractical for the pulp and paper industry because of high capital costs associated with the construction of new digesters. Recent developments in sludge solubilization technology could be promising in reducing digester size, which also allows for the potential use of decommissioned tanks, both of which can reduce the capital cost. Three pretreatment technologies for use with anaerobic digestion were tested on laboratory-scale to investigate their feasibility. The SRTs in all three digesters systematically decreased from 20 to 3 days. The reference digester was fed waste activated sludge (WAS) to serve as the control at the same SRTs. The other digesters were fed WAS that had been preconditioned using mechanical shearing, sonication, or high-pressure homogenization technology. Anaerobic digestion with high-pressure homogenization produced as much methane at 3-day mean SRT as that from the reference digester operated at 20-day SRT. Therefore, a new digester can theoretically be 85% smaller than a conventional digester. An added benefit of WAS to methane conversion is the recovery of nutrients nitrogen and phosphorus. PMID:22866390

Elliott, Allan; Mahmood, Talat



Enhanced methane production from Taihu Lake blue algae by anaerobic co-digestion with corn straw in continuous feed digesters.  


Anaerobic digestion of Taihu blue algae was tested in laboratory scale, continuous feed digesters (hydraulic retention time 10 days) at 35°C and various organic loading rates (OLR). The methane production and biomass digestion performed well at OLR below 4.00 gVSL(-1)d(-1) but deteriorated as OLR increased due to the increased ammonia concentration, causing inhibition mainly to acetate and propionate degradation. Supplementing corn straw as co-feedstock significantly improved the digestion performance. The optimal C/N ratio for the co-digestion was 20:1 at OLR of 6.00 gVSL(-1) d(-1). Methane yield of 234 mL CH4 gVS(-1) and methane productivity of 1404 mL CH4 L(-1) d(-1) were achieved with solid removal of 63%. Compared with the algae alone, the methane productivity was increased by 46% with less accumulation of ammonia and fatty acids. The reactor rate-limiting step was acetate and propionate degradation. PMID:23506978

Zhong, Weizhang; Chi, Lina; Luo, Yijing; Zhang, Zhongzhi; Zhang, Zhenjia; Wu, Wei-Min



Co-digestion of kitchen waste and fruit-vegetable waste by two-phase anaerobic digestion.  


The high salinity and fat contents of kitchen waste (KW) inhibits the effect of two-phase anaerobic digestion system. This research introduces fruit-vegetable waste (FVW) to alleviate the inhibition effect caused by salinity and fat concentrations, and tries to achieve an optimal addition ratio of FVW, an optimal hydraulic remain time (HRT) of acidogenic-phase reactor and methanogenic-phase reactor. A two-phase anaerobic digestion (AD) system was developed to co-dispose KW and FVW. Four sets of experiments were run with different mass proportions between KW and FVW (25-75, 50-50, 75-25, and 100-0% m/m). Considering the biodegradation rate and the acidification degree, the system with 25% KW had the best performance during the acidogenic phase. When the system was run with 50% KW, it not only had the best stability performance but also had a bigger capacity to treat KW than the system with 25% KW. The system with 50% KW was the best ratio in this two-phase AD system. Co-digestion of KW and FVW by two-phase AD is feasible. The addition of FVW can reduce the inhibition effect caused by salinity and fat concentrations, reduce the HRT, and lead to a higher degree of acidification. PMID:23288673

Yang, Yu-Qiang; Shen, Dong-Sheng; Li, Na; Xu, Dong; Long, Yu-Yang; Lu, Xuan-Yu



Reduction of volatile fatty acids and odor offensiveness by anaerobic digestion and solid separation of dairy manure during manure storage.  


Volatile fatty acids (VFA) play an important role in the biodegradation of organic wastes and production of bioenergy under anaerobic digestion, and are related to malodors. However, little is known about the dynamics of VFA during dairy manure storage. This study evaluated the characteristics of VFA in dairy manure before and after anaerobic co-digestion in a laboratory experiment using eight lab-scale reactors. The reactors were loaded with four different types of dairy manure: (1) liquid dairy manure from a freestall barn, (2) mixture of dairy manure and co-digestion food processing wastes at the inlet of an anaerobic digester, (3) effluent from the digester outlet, and (4) the liquid fraction of effluent from a solid separator. Four VFA (acetic, propionic, butyric, and 2-methylbutyric acids) were identified and quantified in weekly manure samples from all reactors. Results showed that the dominant VFA was acetic acid in all four manure sources. The off-farm co-digestion wastes significantly increased the total VFA concentrations and the proportions of individual VFA in the influent. The dairy manure under storage demonstrated high temporal and spatial variations in pH and VFA concentrations. Anaerobic digestion reduced the total VFA by 86%-96%; but solid-liquid separation did not demonstrate a significant reduction in total VFA in this study. Using VFA as an indicator, anaerobic digestion exhibited an effective reduction of dairy manure odor offensiveness. PMID:25617873

Page, Laura H; Ni, Ji-Qin; Zhang, Hao; Heber, Albert J; Mosier, Nathan S; Liu, Xingya; Joo, Hung-Soo; Ndegwa, Pius M; Harrison, Joseph H



Modelling of the temperature-phased batch anaerobic digestion of raw sludge from an urban wastewater treatment plant.  


The disposal of excess sludge from wastewater treatment plants is a serious problem that needs to be addressed. Temperature-phased anaerobic digestion (TPAD) which combines thermophilic and mesophilic processes in one, brings together the advantages of both systems. The aim of the present work was to develop a simple kinetic model to describe the TPAD of sewage sludge in batch completely stirred tank reactors (CSTRs) and to determine the kinetic parameters of both thermophilic and mesophilic stages. A zero-order kinetic equation described the thermophilic step after 2, 4 and 6 days of digestion time (experiment 1, 2 and 3, respectively), yet a first-order equation was found to be adequate to correlate the methane gas accumulated with time in the mesophilic step, the kinetic constant being 0.21 days(-1). The methane yield coefficient obtained was found to be almost proportional to the digestion time used in the thermophilic step with values of 0.067, 0.132 and 0.193 L CH(4) STP/g VS(added) for experiments 1, 2 and 3, respectively. By contrast, the kinetic constant of the mesophilic stage was not influenced by the digestion time used in the thermophilic phase. PMID:22242874

Riau, Víctor; De la Rubia, M Angeles; Pérez, Montserrat; Martín, Antonio; Borja, Rafael



Preliminary experimental results of Sewage Sludge (SS) Co-digestion with Palm Oil Mill Effluent (POME) for Enhanced Biogas Production in Laboratory Scale Anaerobic Digester  

NASA Astrophysics Data System (ADS)

An investigation on the feasibility of co-digesting Sewage Sludge with Palm Oil Mill Effluent for enhancing the biogas production and the corresponding effect of the co-digestion substrate ratio on the biogas production has been evaluated. Anaerobic co-digestion of POME with SS was performed at ratios of 100:0, 70:30, 60:40 and 0:100 to find the optimum blend required for enhanced waste digestion and biogas production. Single stage batch digestion was carried out for 12 days in a laboratory scale anaerobic digester. Co-digestion of sludge's at the 70:30 proportion resulted in optimal COD and C: N ratio which subsequently recorded the highest performance with regards to biogas production at 28.1 L's compared to the 1.98 L's of biogas produced from digestion of SS alone. From the results obtained, it is evident that co-digestion of POME and SS is an attractive option to be explored for enhancement of biogas production in anaerobic digesters.

Sivasankari, R.; Kumaran, P.; Normanbhay, Saifuddin; Halim Shamsuddin, Abd




EPA Science Inventory

The Water Environment Research Foundation (WERF) recently published a report titled Examination of Reactivation and Regrowth of Fecal Coliforms in Anaerobically Digested Sludges. Seven full-scale publicly owned treatment facilities were sampled several times to determine if bacte...


Effect of moisture of municipal biowaste on start-up and efficiency of mesophilic and thermophilic dry anaerobic digestion.  


Methane production from biowaste with 20-30% dry matter (DM) by box-type dry anaerobic digestion and contributing bacteria were determined for incubation at 20, 37 and 55 °C. The same digestion efficiency as for wet anaerobic digestion of biowaste was obtained for dry anaerobic digestion with 20% DM content at 20, 37 and 55 °C and with 25% DM content at 37 and 55 °C. No or only little methane was produced in dry anaerobic reactors with 30% DM at 20, 37 or 55 °C. Population densities in the 20-30% DM-containing biowaste reactors were similar although in mesophilic and thermophilic biowaste reactors with 30% DM content significantly less but phylogenetically more diverse archaea existed. Biogas production in the 20% and 25% DM assays was catalyzed by Methanosarcinales and Methanomicrobiales. In all assays Pelotomaculum and Syntrophobacter species were dominant propionate degraders. PMID:24656488

Li, Chaoran; Mörtelmaier, Christoph; Winter, Josef; Gallert, Claudia



A hybrid anaerobic membrane bioreactor coupled with online ultrasonic equipment for digestion of waste activated sludge.  


Anaerobic membrane bioreactor and online ultrasonic equipment used to enhance membrane filtration were coupled to form a hybrid system (US-AnMBR) designed for long-term digestion of waste activated sludge. The US-AnMBR was operated under volatile solids loading rates of 1.1-3.7 gVS/L·d. After comprehensive studies on digestion performance and membrane fouling control in the US-AnMBR, the final loading rate was determined to be 2.7 gVS/L·d with 51.3% volatile solids destruction. In the US-AnMBR, the improved digestion was due to enhanced sludge disintegration, as indicated by soluble matter comparison in the supernatant and particle size distribution in the digested sludge. Maximum specific methanogenic activity revealed that ultrasound application had no negative effect on anaerobic microorganisms. Furthermore, implementing ultrasound effectively controlled membrane fouling and successfully facilitated membrane bioreactor operation. This lab-scale study demonstrates the potential feasibility and effectiveness of setting up a US-AnMBR system for sludge digestion. PMID:21421308

Xu, Meilan; Wen, Xianghua; Yu, Zhiyong; Li, Yushan; Huang, Xia



Greenhouse and laboratory studies on the effects of an anaerobic digester sludge on growth and nutrient uptake of sorghum  

E-print Network

GREENHOUSE AND LABORATORI STUDIES ON THE EFFECTS OF AN ANAEROBIC DIGESTER SLUDGE ON GROWTH AND NUTRIENT UPTAKE OF SORGHUM A Thesis By John Cooper Vincent Submitted to the Office of Graduate Studies Texas A&M University in partial fulfillment... of the requirements for the degree of MASTER OF SCIENCE December 1989 Major Subject: Agronomy GREENHOUSE AND LABORATORy STUDIES ON THE EFFECTS OF AN ANAEROBIC DIGESTER SLUDGE ON GROWTH AND NUTRIENT UPTAKE OF SORGHUM A Thesis by John Cooper Vincent Approved...

Vincent, John Cooper



Characterization and environmental studies of Pompano Beach anaerobic digestion facility. Annual report  

SciTech Connect

Municipal solid wastes contain numerous substances of potential environmental concern. While some understanding of the composition of raw municipal waste and its leachate products is available, no information regarding characteristics of solid, liquid and gaseous outputs from anaerobic digestion exists. If centralized anaerobic digestion plants are to be environmentally viable, the characteristics and environmental effects of effluents from these plants must be acceptable. The environmental concerns are particularly acute where ground water supplies are precariously low and the water table is high, South Florida is such a location. A characterization and environmental study was initiated by the Resource Recovery Group on August 1978. The specific objectives are: (1) systematic characterization of solid, liquid and gaseous inputs and outputs; (2) investigations of leaching characteristic of output solid and liquid effluents, and the transport of pollutants to and through ground water systems; and (3) analysis of environmental and process parameters to obtain causal relationships.

Sengupta, S; Gerrish, H P; Wong, K F; Nemerow, N; Daly, Jr, E L; Farooq, S; Chriswell, C



Low-cost additive improved silage quality and anaerobic digestion performance of napiergrass.  


Effects of molasses-alcoholic wastewater on the ensiling quality of napiergrass were investigated at ambient temperature, and its anaerobic digestion performance was assessed at mesophilic temperature. Results showed that the molasses-alcoholic wastewater had positive effect on silage quality and anaerobic digestion performance. Lower pH values of 5.20-5.28, lower NH3-N contents of 32.65-36.60 g/kg and higher lactic acid contents of 56-61 mg/kg FM were obtained for the silage samples with molasses-alcoholic wastewater addition. Higher specific biogas yield of 273 mL/g VS was obtained for the sample with 11% molasses-alcoholic wastewater added. Therefore 11% molasses-alcoholic wastewater addition was recommended. PMID:25443806

Lianhua, Li; Feng, Zhen; Yongming, Sun; Zhenhong, Yuan; Xiaoying, Kong; Xianyou, Zhou; Hongzhi, Niu



Anaerobic co-digestion of swine and poultry manure with municipal sewage sludge.  


The anaerobic digestion of municipal sewage sludge (SS) with swine manure (SM) and poultry manure (PM) was undertaken. It was found that a mixture of sewage sludge with a 30% addition of swine manure gave around 400 dm(3)/kg VS of biogas, whereas the maximal biogas yield from ternary mixture (SS:SM:PM=70:20:10 by weight) was only 336 dm(3)/kg VS. An inhibition of methanogenesis by free ammonia was observed in poultry manure experiments. The anaerobic digestion was inefficient in pathogen inactivation as the reduction in the number of E. coli an Enterobacteriaceae was only by one logarithmic unit. A substantial portion of pathogens was also released into the supernatant. PMID:24280622

Borowski, Sebastian; Doma?ski, Jaros?aw; Weatherley, Laurence



Using feature objects aided strategy to evaluate the biomethane production of food waste and corn stalk anaerobic co-digestion.  


Feature objects aided strategy was used to predict and evaluate the biomethane production of food waste and corn stalk anaerobic co-digestion. The kinetics of co-digestion and mono-digestion of food waste and/or corn stalk was also analyzed. The results indicated that the compositions of food waste and corn stalk were significantly different. The anaerobic digestion of three feature objects at different mixing ratios showed the different biomethane yields and kinetic constants. Food waste and corn stalk co-digestion enhanced the digestion rate and achieved 22.48% and 41.55% higher biomethane production than those of food waste and corn stalk mono-digestion, respectively. PMID:25575585

Zhou, Qi; Yuan, Hairong; Liu, Yanping; Zou, Dexun; Zhu, Baoning; Chufo, Wachemo A; Jaffar, Muhammad; Li, Xiujin



Effect of silver nanoparticles and antibiotics on antibiotic resistance genes in anaerobic digestion.  


Water resource recovery facilities have been described as creating breeding ground conditions for the selection, transfer, and dissemination of antibiotic resistance genes (ARGs) among various bacteria. The objective of this study was to determine the effect of direct addition of antibiotic and silver nanoparticles (Ag NPs, or nanosilver) on the occurrence of ARGs in thermophilic anaerobic digesters. Test thermophilic digesters were amended with environmentally-relevant concentrations of Ag NP (0.01, 0.1, and 1.0 mg-Ag/L; corresponding to approximately 0.7, 7.0, and 70 mg-Ag/kg total solids) and sulfamethoxazole (SMX) that span susceptible to resistant classifications (1, 5, and 50 mg/L) as potential selection pressures for ARGs. Tetracycline (tet(O), tet(W)) and sulfonamide (sulI, sulII) ARGs and the integrase enzyme gene (intI1) associated with Class 1 integrons were measured in raw sludge, test thermophilic digesters, a control thermophilic digester, and a control mesophilic digester. There was no apparent effect of Ag NPs on thermophilic anaerobic digester performance. The maximum SMX addition (50 mg/L) resulted in accumulation of volatile fatty acids and low pH, alkalinity, and volatile solids reduction. There was no significant difference between ARG gene copy numbers (absolute or normalized to 16S rRNA genes) in amended thermophilic digesters and the control thermophilic digester. Antibiotic resistance gene copy numbers in digested sludge ranged from 10(3) to 10(6) copies per microL (approximately 8 x10(1) to 8 x 10(4) copies per microg) of sludge as result of a 1-log reduction of ARGs (2-log reduction for intI1). Quantities of the five ARGs in raw sludge ranged from 10(4) to 10(8) copies per microL (approximately 4 x 10(2) to 4 x 10(6) per microg) of sludge. Test and control thermophilic digesters (53 degrees C, 12-day solids retention time [SRT]) consistently reduced but did not eliminate levels of all analyzed genes. The mesophilic digester (37 degrees C, 20-day SRT) also reduced levels of sulI, sulII, and intI1 genes, but levels of tet(O) and tet(W) were the same or higher than in raw sludge. Antibiotic resistance gene reductions remained constant despite the application of selection pressures, which suggests that digester operating conditions are a strong governing factor of the bacterial community composition and thus the prevalence of ARGs. PMID:23789571

Miller, Jennifer H; Novak, John T; Knocke, William R; Young, Katherine; Hong, Yanjuan; Vikesland, Peter J; Hull, Matthew S; Pruden, Amy



Effects of microbial and non-microbial factors of liquid anaerobic digestion effluent as inoculum on solid-state anaerobic digestion of corn stover.  


The microbial activity of the inoculum (liquid anaerobic digestion effluent) was altered by autoclaving part of the effluent to study the effect of feedstock to active effluent ratio (F/Ea, 2.2-6.6) and the feedstock to total effluent ratio (F/Et, 2.2 and 4.4) on reactor performance in solid state anaerobic digestion (SS-AD) of corn stover. When the F/Ea ratio was increased from 2.2 to 6.6, methane yield was not significantly reduced; however, reactors became acidified when the F/Et ratio was increased from 2.2 to 4.4. It was concluded that F/Et had a greater effect on methane yields than F/Ea for the range studied in this paper. As analyzed by denaturing gradient gel electrophoresis using PCR amplified 16S rRNA genes, the microbial community underwent dynamic shifts under acidified conditions over 38days of SS-AD. These shifts reflected the acclimation, both adaptive selection and diversification, of the initial inoculated microbial consortia. PMID:24556372

Shi, Jian; Xu, Fuqing; Wang, Zhongjiang; Stiverson, Jill A; Yu, Zhongtang; Li, Yebo



Effects of ionic strength and ion pairing on (plant-wide) modelling of anaerobic digestion.  


Plant-wide models of wastewater treatment (such as the Benchmark Simulation Model No. 2 or BSM2) are gaining popularity for use in holistic virtual studies of treatment plant control and operations. The objective of this study is to show the influence of ionic strength (as activity corrections) and ion pairing on modelling of anaerobic digestion processes in such plant-wide models of wastewater treatment. Using the BSM2 as a case study with a number of model variants and cationic load scenarios, this paper presents the effects of an improved physico-chemical description on model predictions and overall plant performance indicators, namely effluent quality index (EQI) and operational cost index (OCI). The acid-base equilibria implemented in the Anaerobic Digestion Model No. 1 (ADM1) are modified to account for non-ideal aqueous-phase chemistry. The model corrects for ionic strength via the Davies approach to consider chemical activities instead of molar concentrations. A speciation sub-routine based on a multi-dimensional Newton-Raphson (NR) iteration method is developed to address algebraic interdependencies. The model also includes ion pairs that play an important role in wastewater treatment. The paper describes: 1) how the anaerobic digester performance is affected by physico-chemical corrections; 2) the effect on pH and the anaerobic digestion products (CO2, CH4 and H2); and, 3) how these variations are propagated from the sludge treatment to the water line. Results at high ionic strength demonstrate that corrections to account for non-ideal conditions lead to significant differences in predicted process performance (up to 18% for effluent quality and 7% for operational cost) but that for pH prediction, activity corrections are more important than ion pairing effects. Both are likely to be required when precipitation is to be modelled. PMID:25540837

Solon, Kimberly; Flores-Alsina, Xavier; Mbamba, Christian Kazadi; Volcke, Eveline I P; Tait, Stephan; Batstone, Damien; Gernaey, Krist V; Jeppsson, Ulf



High rate anaerobic digestion of a petrochemical wastewater using biomass support particles  

Microsoft Academic Search

Anaerobic digestion of wastewater from a dimethyl terephthalate plant was studied in continuously stirred tank reactors with plastic net biomass support particles (BSP) at a level of 20% (v\\/v). The experimental results showed that the BSP system could treat the wastewater at a hydraulic retention time as low as 1.5 d, organic loading as high as 20 kg COD\\/m3\\/d and

C. Ramakrishna; J. D. Desai



Advanced techniques for characterization of organic matter from anaerobically digested grapemarc distillery effluents and amended soils  

Microsoft Academic Search

The effects of grapemarc distillery effluents on the quality of soil organic matter is extremely important to ensure the environmentally-safe\\u000a and agronomically efficient use of these materials as organic amendment. In this work, the effects of the application of untreated\\u000a (UG) and anaerobically digested grapemarc distillery effluents, either added with (AGM) or without mycorrhiza (AG), on soil\\u000a humic acid (HA)

Gennaro Brunetti; Karam Farrag; Cesar Plaza; Nicola Senesi


Agricultural potential of anaerobically digested industrial orange waste with and without aerobic post-treatment  

Microsoft Academic Search

The potential of anaerobically digested orange waste with (AAD) and without (AD) aerobic post-treatment for use in agriculture was evaluated through chemical analyses, short-term phytotoxicity and long-term plant assays. Chemical analyses showed that AD contained ammonia and organic acids, and aerobic post-treatment did not significantly remove these phytotoxins. The N:P2O5:K2O ratio in AD was 1:0.26:0.96 and aerobic post-treatment did not

Prasad Kaparaju; Jukka Rintala; Aimo Oikari



A kinetic study of the anaerobic digestion of ice-cream wastewater  

Microsoft Academic Search

The process kinetics of the mesophilic (35°C) anaerobic digestion of ice-cream wastewater was investigated. The Monod equation and the Contois equation were used to develop two basic steady-state models. The kinetic parameters required for the application for the steady-state models were determined using a laboratory-scale continuously stirred tank reactor (5 l) fed with a synthetic ice-cream wastewater at a range

W. C Hu; K Thayanithy; C. F Forster



Mechanism of inhibition caused by long-chain fatty acids in anaerobic digestion process  

Microsoft Academic Search

The inhibitory effect of long-chain fatty acids on the anaerobic digestion process was examined in batch experiments using synthetic substrates. The addition of long-chain fatty acids caused the appearance of the lag period in the methane production from acetate and in the degradation of both long-chain fatty acids and n-butyrate. Methane production from hydrogen proceeded without lag period although its

Keisuke Hanaki; Tomonori Matsuo; Michihiko Nagase



Effects of lipids on thermophilic anaerobic digestion and reduction of lipid inhibition upon addition of bentonite  

Microsoft Academic Search

The effect of bentonite-bound oil on thermophilic anaerobic digestion of cattle manure was investigated. In digestor experiments, addition of oil was found to be inhibitory during start-up and the inhibitory effect was less pronounced when the oil was added in the form of bentonite-bound oil compared to when the oil was added alone. After adaption of the digestors, very rapid

I. Angelidaki; S. P. Petersen; B. K. Ahring



Bacteria and archaea involved in anaerobic digestion of distillers grains with solubles  

Microsoft Academic Search

Cereal distillers grains, a by-product from bioethanol industry, proved to be a suitable feedstock for biogas production in\\u000a laboratory scale anaerobic digesters. Five continuously stirred tank reactors were run under constant conditions and monitored\\u000a for biogas production and composition along with other process parameters. Iron additives for sulfide precipitation significantly\\u000a improved the process stability and efficiency, whereas aerobic pretreatment of

Ayrat M. Ziganshin; Thomas Schmidt; Frank Scholwin; Olga N. Il’inskaya; Hauke Harms; Sabine Kleinsteuber



Designs of anaerobic digesters for producing biogas from municipal solid-waste  

Microsoft Academic Search

The production of biogas is of growing interest as fossil-fuel reserves decline. However, there exists a dearth of literature on the design considerations that would lead to process optimization in the development of anaerobic digesters aimed at creating useful commodities from the ever-abundant municipal solid-waste. Consequently, this paper provides a synthesis of the key issues and analyses concerning the design

A. Hilkiah Igoni; M. J. Ayotamuno; C. L. Eze; S. O. T. Ogaji; S. D. Probert



Inactivation of virus during anaerobic digestion of manure in laboratory scale biogas reactors  

Microsoft Academic Search

Reduction of porcine parvovirus, bovine enterovirus and faecal enterococci were measured in biogas reactors continuously run\\u000a on manure and manure supplemented with household waste at 35°C and 55°C and in batch test run at 70°C. The aim of the experiments\\u000a was to study the sanitation effect of anaerobic digestion and to evaluate the use of faecal enterococci as an indicator

Bente Lund; Vibeke Frøkjær Jensen; Per Have; Birgitte Ahring



Zinc and copper distribution in swine wastewater treated by anaerobic digestion.  


Swine wastewater contain high levels of metals, such as copper and zinc, which can cause a negative impact on the environment. Anaerobic digestion is a process commonly used to remove carbon, and can act on metal availability (e.g., solubility or oxidation state). The present study aimed to evaluate the influence of anaerobic digestion on total Zn and Cu contents, and their chemical fractioning due to the biodegradation of the effluent over different hydraulic retention times (HRTs). The sequential extraction protocol proposed by the Community Bureau of Reference (BCR), plus two additional fractions, was the method chosen for this study of Cu and Zn distribution evaluation in swine wastewater. The Zn and Cu concentrations in raw swine manure were 63.58 ± 27.72 mg L(-1) and 8.98 ± 3.99 mg L(-1), respectively. The metal retention capacity of the bioreactor decreased when the HRT was reduced from 17.86 d to 5.32 d. Anaerobic digestion had a direct influence on zinc and copper distribution when raw manure (RM) and digested manure (DM) were compared. The reducible fraction showed a reduction of between 3.17% and 7.84% for Zn and between 2.52% and 11.92% for Cu when DM was compared with RM. However, the metal concentration increased in the oxidizable fraction of DM, viz. from 3.01% to 10.64% for Zn and from 4.49% to 16.71% for Cu, thus demonstrating the effect of anaerobic conditions on metal availability. PMID:24794386

Cestonaro do Amaral, André; Kunz, Airton; Radis Steinmetz, Ricardo Luís; Justi, Karin Cristiane



Anaerobic digestion for global warming control and energy generation—An overview  

Microsoft Academic Search

Anaerobic digestion often generates ‘biogas’ – an approximately 3:1 mixture of methane and carbon dioxide – which has been known to be a ‘clean’ fuel since the late 19th century. But a great resurgence of interest in biogas capture – hence methane capture – has occurred in recent years due to the rapidly growing spectre of global warming. Anthropogenic causes

Tasneem Abbasi; S. M. Tauseef; S. A. Abbasi



Chlorella pyrenoidosa cultivation using anaerobic digested starch processing wastewater in an airlift circulation photobioreactor.  


To explore the integration of microalgae cultivation and anaerobic processing for wastewater treatment, we utilized an airlift circulation photobioreactor and a dynamic membrane reactor for microalgae cultivation in combination with an upflow anaerobic sludge bed (UASB) reactor for starch processing wastewater (SPW) treatment. Chlorella pyrenoidosa completely adapted to the digested SPW without any chemical additives, and it grew normally under a wide temperature range in different seasons. C. pyrenoidosa was always the dominant microorganism in the photobioreactors although bacteria and some wild type microalgae were observed. Optimal biomass growth and pollutants removal was achieved at temperatures between 35 and 38°C in summer, removing 65.99% of COD, 83.06% of TN, 96.97% of TP and a biomass productivity of 0.37gL(-1)d(-1). Temperature fluctuation significantly influenced lipid contents and FAMEs compositions in biomass. The results demonstrate the successful integration of microalgae biomass production and anaerobic processing for wastewater treatment. PMID:25164347

Tan, Xiaobo; Chu, Huaqiang; Zhang, Yalei; Yang, Libin; Zhao, Fangchao; Zhou, Xuefei



Anaerobic digestion of slaughterhouse waste: main process limitations and microbial community interactions.  


Fresh pig/cattle slaughterhouse waste mixtures, with different lipid-protein ratios, were characterized and their anaerobic biodegradability assessed in batch tests. The resultant methane potentials were high (270-300 L(CH4) kg(-1)(COD)) making them interesting substrates for the anaerobic digestion process. However, when increasing substrate concentrations in consecutive batch tests, up to 15 g(COD) kg(-1), a clear inhibitory process was monitored. Despite the reported severe inhibition, related to lipid content, the system was able to recover activity and successfully degrade the substrate. Furthermore, 16SrRNA gene-based DGGE results showed an enrichment of specialized microbial populations, such as ?-oxidizing/proteolitic bacteria (Syntrophomonas sp., Coprothermobacter sp. and Anaerobaculum sp.), and syntrophic methanogens (Methanosarcina sp.). Consequently, the lipid concentration of substrate and the structure of the microbial community are the main limiting factors for a successful anaerobic treatment of fresh slaughterhouse waste. PMID:21030248

Palatsi, J; Viñas, M; Guivernau, M; Fernandez, B; Flotats, X



Effect of Increasing Total Solids Contents on Anaerobic Digestion of Food Waste under Mesophilic Conditions: Performance and Microbial Characteristics Analysis  

PubMed Central

The total solids content of feedstocks affects the performances of anaerobic digestion and the change of total solids content will lead the change of microbial morphology in systems. In order to increase the efficiency of anaerobic digestion, it is necessary to understand the role of the total solids content on the behavior of the microbial communities involved in anaerobic digestion of organic matter from wet to dry technology. The performances of mesophilic anaerobic digestion of food waste with different total solids contents from 5% to 20% were compared and the microbial communities in reactors were investigated using 454 pyrosequencing technology. Three stable anaerobic digestion processes were achieved for food waste biodegradation and methane generation. Better performances mainly including volatile solids reduction and methane yield were obtained in the reactors with higher total solids content. Pyrosequencing results revealed significant shifts in bacterial community with increasing total solids contents. The proportion of phylum Chloroflexi decreased obviously with increasing total solids contents while other functional bacteria showed increasing trend. Methanosarcina absolutely dominated in archaeal communities in three reactors and the relative abundance of this group showed increasing trend with increasing total solids contents. These results revealed the effects of the total solids content on the performance parameters and the behavior of the microbial communities involved in the anaerobic digestion of food waste from wet to dry technologies. PMID:25051352

Jin, Jingwei; Dai, Xiaohu



Digest Your Food!  

NSDL National Science Digital Library

In a multi-week experiment, student teams gather biogas data from the mini-anaerobic digesters that they build to break down different types of food waste with microbes. Using plastic soda bottles for the mini-anaerobic digesters and gas measurement devices, they compare methane gas production from decomposing hot dogs, diced vs. whole. They monitor and measure the gas production, then graph and analyze the collected data. Students learn how anaerobic digestion can be used to biorecycle waste (food, poop or yard waste) into valuable resources (nutrients, biogas, energy).

Membrane Biotechnology Laboratory,


Start-Up of an Anaerobic Dynamic Membrane Digester for Waste Activated Sludge Digestion: Temporal Variations in Microbial Communities  

PubMed Central

An anaerobic dynamic membrane digester (ADMD) was developed to digest waste sludge, and pyrosequencing was used to analyze the variations of the bacterial and archaeal communities during the start-up. Results showed that bacterial community richness decreased and then increased over time, while bacterial diversity remained almost the same during the start-up. Proteobacteria and Bacteroidetes were the major phyla. At the class level, Betaproteobacteria was the most abundant at the end of start-up, followed by Sphingobacteria. In the archaeal community, richness and diversity peaked at the end of the start-up stage. Principle component and cluster analyses demonstrated that archaeal consortia experienced a distinct shift and became stable after day 38. Methanomicrobiales and Methanosarcinales were the two predominant orders. Further investigations indicated that Methanolinea and Methanosaeta were responsible for methane production in the ADMD system. Hydrogenotrophic pathways might prevail over acetoclastic means for methanogenesis during the start-up, supported by specific methanogenic activity tests. PMID:24695488

Yu, Hongguang; Wang, Qiaoying; Wang, Zhiwei; Sahinkaya, Erkan; Li, Yongli; Ma, Jinxing; Wu, Zhichao



Electrical energy production from biosolids: a comparative study between anaerobic digestion and ultra-high-temperature gasification.  


Biosolids management is one of the most expensive and complicated processes in sanitation engineering. Anaerobic digestion (AD) is often employed for the stabilization ofbiomass and for energy production, as approximately 50% of the carbon entering the anaerobic digester is recovered as methane (CH4). Gasification has been used recently for the thermal reformation of biosolids to synthesis gas (syngas), which primarily consists ofcarbon monoxide (CO) and hydrogen (H2). In the present work, the net electrical energy production from biosolids has been calculated, for a typical activated sludge wastewater treatment plant, with an inlet flow rate of 75,708 m3/d (equal to 20 Mgd). The calculations suggest that the ultra-high-temperature gasification (UHTG) system can achieve a net electrical energy output of about 15.40 MJ/kg (dry biosolids), whereas the AD system can achieve values between 8.45 MJ/kg(dry biosolids). The latter values correspond to approximate net electrical energy power of 18.8 kW for UHTG, versus 9.9 kW for AD, for a wastewater treatment plant with capacity of 1000 m3/d; thus, the UHTG process yields approximately 190% of the energy that may be produced by the AD process. PMID:25145165

Gikas, Petros



Performance evaluation of an anaerobic/aerobic landfill-based digester using yard waste for energy and compost production  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Biochemical methane potential decreased by 83% during the two-stage operation. Black-Right-Pointing-Pointer Net energy produced was 84.3 MWh or 46 kWh per million metric tons (Mg). Black-Right-Pointing-Pointer The average removal efficiency of volatile organic compounds (VOCs) was 96-99%. Black-Right-Pointing-Pointer The average removal efficiency of non-methane organic compounds (NMOCs) was 68-99%. Black-Right-Pointing-Pointer The two-stage batch digester proved to be simple to operate and cost-effective. - Abstract: The objective of this study was to evaluate a new alternative for yard waste management by constructing, operating and monitoring a landfill-based two-stage batch digester (anaerobic/aerobic) with the recovery of energy and compost. The system was initially operated under anaerobic conditions for 366 days, after which the yard waste was aerated for an additional 191 days. Off gas generated from the aerobic stage was treated by biofilters. Net energy recovery was 84.3 MWh, or 46 kWh per million metric tons of wet waste (as received), and the biochemical methane potential of the treated waste decreased by 83% during the two-stage operation. The average removal efficiencies of volatile organic compounds and non-methane organic compounds in the biofilters were 96-99% and 68-99%, respectively.

Yazdani, Ramin, E-mail: [Yolo County Planning and Public Works Department, Division of Integrated Waste Management, Woodland, CA 95776 (United States); Civil and Environmental Engineering, University of California, One Shields Avenue, Ghausi Hall, Davis, CA 95616 (United States); Barlaz, Morton A., E-mail: [Department of Civil, Construction, and Environmental Engineering, North Carolina State University, Raleigh, NC 27695 (United States); Augenstein, Don, E-mail: [Institute for Environmental Management, Inc., Palo Alto, CA 94306 (United States); Kayhanian, Masoud, E-mail: [Civil and Environmental Engineering, University of California, One Shields Avenue, Ghausi Hall, Davis, CA 95616 (United States); Tchobanoglous, George, E-mail: [Civil and Environmental Engineering, University of California, One Shields Avenue, Ghausi Hall, Davis, CA 95616 (United States)



Modelling anaerobic digestion acclimatisation to a biodegradable toxicant: application to cyanide.  


The observed acclimatisation to biodegradable toxicants in anaerobic cassava wastewater treatment is explained by modelling anaerobic cyanide degradation. A complete degradation pathway is proposed for cyanide. Cyanide degradation is modelled as enzymatic hydrolysis to formate and ammonia. Ammonia is added to the inorganic nitrogen content of the digester while formate is degraded by the hydrogenotrophic methanogens. Cyanide irreversible enzyme inhibition is modelled as an inhibition factor to acetate uptake processes. Cyanide irreversible toxicity is modelled as a decay factor to the acetate degraders. Cyanide as well as added phosphorus buffer solution were considered in the chemical equilibrium calculations of pH. The observed reversible effect after acclimatisation of sludge is modelled by a population shift between two aceticlastic methanogens that have different tolerance to cyanide toxicity. The proposed pathway is added to the IWA Anaerobic Digestion Model no.1 (ADM1). The ADM1 model with the designed extension is validated by an experiment using three lab-scale upflow anaerobic sludge bed reactors which were exposed to different cyanide loadings. PMID:17037178

Zaher, U; Moussa, M S; Widyatmika, I N; van Der Steen, P; Gijzen, H J; Vanrolleghem, P A



Recent development of anaerobic digestion processes for energy recovery from wastes.  


Anaerobic digestion leads to the overall gasification of organic wastewaters and wastes, and produces methane and carbon dioxide; this gasification contributes to reducing organic matter and recovering energy from organic carbons. Here, we propose three new processes and demonstrate the effectiveness of each process. By using complete anaerobic organic matter removal process (CARP), in which diluted wastewaters such as sewage and effluent from a methane fermentation digester were treated under anaerobic condition for post-treatment, the chemical oxygen demand (COD) in wastewater was decreased to less than 20 ppm. The dry ammonia-methane two-stage fermentation process (Am-Met process) is useful for the anaerobic treatment of nitrogen-rich wastes such as waste excess sludge, cow feces, chicken feces, and food waste without the dilution of the ammonia produced by water or carbon-rich wastes. The hydrogen-methane two-stage fermentation (Hy-Met process), in which the hydrogen produced in the first stage is used for a fuel cell system to generate electricity and the methane produced in the second stage is used to generate heat energy to heat the two reactors and satisfy heat requirements, is useful for the treatment of sugar-rich wastewaters, bread wastes, and biodiesel wastewaters. PMID:17368391

Nishio, Naomichi; Nakashimada, Yutaka



Anaerobic co-digestion of aquatic flora and quinoa with manures from Bolivian Altiplano.  


Quinoa stalk (Chenopodium quinoa Willd.) from agricultural crop residue, totora (Schoenoplectus tatora) and o-macrophytes (aquatic flora) from Lake Titicaca (on the Bolivian Altiplano) were studied in a wet anaerobic co-digestion process together with manure from llama, cow and sheep. Anaerobic semi-continuous experiments were performed in (10) 2-l reactors at a temperature of 25 degrees C with 30 days of hydraulic retention time (HRT) and an organic loading rate (OLR) of 1.8 kg VS m(-3) d(-1). Totora was found to be the best co-substrate. In mixture ratios of 1:1 (VS basis), it increased the biogas productivity by 130% for llama manure, 60% for cow manure, and 40% for sheep manure. It was possible to use up to 58% (VS basis) of totora in the substrate. Higher concentrations (including pure totora) could not be digested, as that caused acidification problems similar to those caused by other lignocellulosic materials. When quinoa and o-macrophytes were used as co-substrates, the increase in biogas productivity was slightly less. However, these co-substrates did not cause any operational problems. An additional advantage of quinoa and o-macrophytes was that they could be used in any proportion (even in pure form) without causing any destabilization problems in the anaerobic digestion process. PMID:18155895

Alvarez, René; Lidén, Gunnar



Anaerobic co-digestion of aquatic flora and quinoa with manures from Bolivian Altiplano  

SciTech Connect

Quinoa stalk (Chenopodium quinoa Willd.) from agricultural crop residue, totora (Schoenoplectus tatora) and o-macrophytes (aquatic flora) from Lake Titicaca (on the Bolivian Altiplano) were studied in a wet anaerobic co-digestion process together with manure from llama, cow and sheep. Anaerobic semi-continuous experiments were performed in (10) 2-l reactors at a temperature of 25 deg. C with 30 days of hydraulic retention time (HRT) and an organic loading rate (OLR) of 1.8 kg VS m{sup -3} d{sup -1}. Totora was found to be the best co-substrate. In mixture ratios of 1:1 (VS basis), it increased the biogas productivity by 130% for llama manure, 60% for cow manure, and 40% for sheep manure. It was possible to use up to 58% (VS basis) of totora in the substrate. Higher concentrations (including pure totora) could not be digested, as that caused acidification problems similar to those caused by other lignocellulosic materials. When quinoa and o-macrophytes were used as co-substrates, the increase in biogas productivity was slightly less. However, these co-substrates did not cause any operational problems. An additional advantage of quinoa and o-macrophytes was that they could be used in any proportion (even in pure form) without causing any destabilization problems in the anaerobic digestion process.

Alvarez, Rene [IIDEPROQ, UMSA, Plaza del Obelisco 1175, La Paz (Bolivia)], E-mail:; Liden, Gunnar [Department of Chemical Engineering, Lund University, P.O. Box 124, 221 00 Lund (Sweden)



Changes in bacterial communities from anaerobic digesters during petroleum hydrocarbon degradation.  


Anaerobic biodegradation of petroleum hydrocarbons (PHC) to methane has been recognized to occur in oil reservoirs and contaminated surface sites alike. This process could be employed efficiently for the treatment of contaminated materials, including petrochemical wastes and PHC-contaminated soil, since no external electron acceptor is required. Moreover, the controlled production of methane in digestion plants, similarly to the anaerobic digestion (AD) of energy crops or organic residues, would enable for energy recovery from these wastes. At present, little is known about the bacterial communities involved in and responsible for hydrocarbon fermentation, the initial step in PHC conversion to methane. In the present study, the fate of two different methanogenic communities derived from the AD of wastewater (WWT) and of biowaste, mixed with PHC-contaminated soil (SWT), was monitored during incubation with PHC using denaturing gradient gel electrophoresis (DGGE) of 16S rDNA genes amplified with Bacteria-specific primers. During 11 months of incubation, slight but significant degradation of PHC occurred in both sludges and distinct bacterial communities were developing. In both sludges, Bacteroidetes were found. In addition, in WWT, the bacterial community was found to be dominated by Synergistetes and Proteobacteria, while Firmicutes and unidentified members were abundant in SWT. These results indicate that bacterial communities from anaerobic digesters can adapt to and degrade petroleum hydrocarbons. The decontamination of PHC-containing waste via fermentative treatment appears possible. PMID:21939698

Scherr, Kerstin E; Lundaa, Tserennyam; Klose, Viviana; Bochmann, Günther; Loibner, Andreas P



Evaluation of a Ca-modified porphyritic andesite for ammonium removal in the anaerobic digestion process.  


In this study, a Ca-modified porphyritic andesite (wheat-rice-stone (WRS)) was developed for the anaerobic digestion of ammonium-rich wastes. The Ca-modified WRS was obtained with integrated Ca-salt treatment and calcination. Scanning electron microscope and Brunauer-Emmett-Teller surface area analyses were performed to characterize the Ca-modified WRS, and adsorption isotherms and kinetics were investigated to clarify the adsorption mechanism. The ammonium adsorption process was explained well with a pseudo-second-order kinetic model. The specific surface area of the Ca-modified WRS was determined to be 4.56 sq. m/g, and the maximum NH4(+)-N adsorption capacity was determined to be 45.45 mg/g. These values are improvements over those of natural WRS. The ammonium adsorption capacity remained constant at a pH range from 5.0 to 9.0, which indicates that Ca-modified WRS is a promising material for various applications. The methane-production and chemical oxygen demand-removal aspects of anaerobic digestion were much improved with the addition of Ca-modified WRS. Therefore, Ca-modified WRS could be developed into a viable ammonium adsorbent for the anaerobic digestion of ammonium-rich wastes. PMID:23837319

Wang, Qinghong; Yang, Yingnan; Li, Dawei; Zhang, Zhenya



Life cycle assessment of energy from waste via anaerobic digestion: a UK case study.  


Particularly in the UK, there is potential for use of large-scale anaerobic digestion (AD) plants to treat food waste, possibly along with other organic wastes, to produce biogas. This paper presents the results of a life cycle assessment to compare the environmental impacts of AD with energy and organic fertiliser production against two alternative approaches: incineration with energy production by CHP and landfill with electricity production. In particular the paper investigates the dependency of the results on some specific assumptions and key process parameters. The input Life Cycle Inventory data are specific to the Greater London area, UK. Anaerobic digestion emerges as the best treatment option in terms of total CO2 and total SO2 saved, when energy and organic fertiliser substitute non-renewable electricity, heat and inorganic fertiliser. For photochemical ozone and nutrient enrichment potentials, AD is the second option while incineration is shown to be the most environmentally friendly solution. The robustness of the model is investigated with a sensitivity analysis. The most critical assumption concerns the quantity and quality of the energy substituted by the biogas production. Two key issues affect the development and deployment of future anaerobic digestion plants: maximising the electricity produced by the CHP unit fuelled by biogas and to defining the future energy scenario in which the plant will be embedded. PMID:24112851

Evangelisti, Sara; Lettieri, Paola; Borello, Domenico; Clift, Roland



Do anaerobic digestates promote dispersion, acidification and water repellency in soils?  

NASA Astrophysics Data System (ADS)

Digestates are used as organic fertilizer on agricultural land due to their high amounts of nutrients (e.g. potassium, sodium). It is commonly expected that the application of sludge derived from anaerobic digestion can influence the soil structure and soil stability. Due to the fact that digestates contain large quantities of monovalent salts and long-chained fatty acids, the consequence of sludge amendment can be soil degradation caused by acidification, dispersion and increased water-repellency. Thus, water infiltration can be impeded which results in a preservation of stable soil aggregates. However, a diminished water infiltration can support water erosion and preferential flow of easy soluble nutrients into the groundwater. Our research was conducted with different digestates derived from maize, wheat and sugar beet to examine occurring processes in soils of two different textures after the application of anaerobic sludges. Particularly, we focused on the wetting properties of the soil. For this purpose, the wetting behavior was investigated by determining the sorptivity-based Repellency Index with moist samples and the contact angle with homogenized, air-dried soil material. Further surveys were carried out to assess the flow behavior of digestates application and the deformation of the particle-to-particle association by microscaled shearing. Additionally, the acidification process in the soil as a result of sludge application was investigated. To account for the dispersive impact of digestates, the turbidity of soil suspensions was ascertained. We summarize from the results that the digestates have a clear impact on the water repellency of the soil. We recognized a shift to more hydrophobic conditions. Partially, the pH remains on a high level due to the alkaline digestate, but several samples show a decline of pH, depending on the soil texture, respectively. However, soil structure was weakened as was shown by an increase of turbidity. As a conclusion, we point out the necessity to take into account the impact which anaerobic digestates might have on soil structure and stability in addition to their fertilizing effect to sustain the soil in a good state.

Voelkner, Amrei; Holthusen, Dörthe; Horn, Rainer



Net energy production associated with pathogen inactivation during mesophilic and thermophilic anaerobic digestion of sewage sludge.  


The potential for anaerobic digester energy production must be balanced with the sustainability of reusing the resultant biosolids for land application. Mesophilic, thermophilic, temperature-phased, and high temperature (60 or 70 °C) batch pre-treatment digester configurations have been systematically evaluated for net energy production and pathogen inactivation potential. Energy input requirements and net energy production were modeled for each digester scheme. First-order inactivation rate coefficients for Escherichia coli, Enterococcus faecalis and bacteriophage MS-2 were measured at each digester temperature and full-scale pathogen inactivation performance was estimated for each indicator organism and each digester configuration. Inactivation rates were found to increase dramatically at temperatures above 55 °C. Modeling full-scale performance using retention times based on U.S. EPA time and temperature constraints predicts a 1-2 log inactivation in mesophilic treatment, and a 2-5 log inactivation in 50-55 °C thermophilic and temperature-phased treatments. Incorporating a 60 or 70 °C batch pre-treatment phase resulted in dramatically higher potency, achieving MS-2 inactivation of 14 and 16 logs respectively, and complete inactivation (over 100 log reduction) of E. coli and E. faecalis. For temperatures less than 70 °C, viability staining of thermally-treated E. coli showed significantly reduced inactivation relative to standard culture enumeration. Due to shorter residence times in thermophilic reactors, the net energy production for all digesters was similar (less than 20% difference) with the 60 or 70 °C batch treatment configurations producing the most net energy and the mesophilic treatment producing the least. Incorporating a 60 or 70 °C pre-treatment phase can dramatically increase pathogen inactivation performance without decreasing net energy capture from anaerobic digestion. Energy consumption is not a significant barrier against improving the pathogen quality of biosolids. PMID:21764416

Ziemba, Christopher; Peccia, Jordan



Impacts of microwave pretreatments on the semi-continuous anaerobic digestion of dairy waste activated sludge  

SciTech Connect

Highlights: ? Microwave pretreatment of dairy WAS was studied. ? MW pretreatment at 70% intensity for 12 min, COD solubilization was 18.6%. ? Biogas production and SS reduction was 35% and 14% higher than control. ? In digester at 15 days SRT with medium OLR, SS and VS reduction was 67% and 64%. ? Biogas and methane production was 57% and 49% higher than control, in digesters. - Abstract: Microwave (MW) irradiation is one of the new and possible methods used for pretreating the sludge. Following its use in different fields, this MW irradiation method has proved to be more appropriate in the field of environmental research. In this paper, we focused on the effects of MW irradiation at different intensities on solubilization, biodegradation and anaerobic digestion of sludge from the dairy sludge. The changes in the soluble fractions of the organic matter, the biogas yield, the methane content in the biogas were used as control parameters for evaluating the efficiency of the MW pretreatment. Additionally, the energetic efficiency was also examined. In terms of an energetic aspect, the most economical pretreatment of sludge was at 70% intensity for 12 min irradiation time. At this, COD solubilization, SS reduction and biogas production were found to be 18.6%, 14% and 35% higher than the control, respectively. Not only the increase in biogas production was investigated, excluding protein and carbohydrate hydrolysis was also performed successfully by this microwave pretreatment even at low irradiation energy input. Also, experiments were carried out in semi continuous anaerobic digesters, with 3.5 L working volume. Combining microwave pretreatment with anaerobic digestion led to 67%, 64% and 57% of SS reduction, VS reduction and biogas production higher than the control, respectively.

Uma Rani, R.; Adish Kumar, S. [Department of Civil Engineering, Regional Centre of Anna University, Tirunelveli 627 007, Tamil Nadu (India); Kaliappan, S. [Department of Civil Engineering, Ponjesly College of Engineering, Nagercoil 629 003, Tamil Nadu (India); Yeom, IckTae [Department of Civil and Environmental Engineering, Sungkyunkwan University (Korea, Republic of); Rajesh Banu, J., E-mail: [Department of Civil Engineering, Regional Centre of Anna University, Tirunelveli 627 007, Tamil Nadu (India)



Anaerobic digestibility of marine microalgae Phaeodactylum tricornutum in a lab-scale anaerobic membrane bioreactor  

Microsoft Academic Search

The biomass of industrially grown Phaeodactylum tricornutum was subjected in a novel way to bio-methanation at 33A degrees C, i.e., in an anaerobic membrane bioreactor (AnMBR) at a hydraulic retention time of 2.5 days, at solid retention times of 20 to 10 days and at loading rates in the range of 2.6-5.9 g biomass-COD L(-1) day(-1) with membrane fluxes ranging

C. Zamalloa; J. De Vrieze; N. Boon; W. Verstraete



Anaerobic co-digestion of pig manure and algae: Impact of intracellular algal products recovery on co-digestion performance.  


This paper investigates anaerobic co-digestion of pig manure and algae (Scenedesmus sp.) with and without extraction of intracellular algal co-products, with views towards the development of a biorefinery concept for lipid, protein and/or biogas production. Protein and/or lipids were extracted from Scenedesmus sp. using free nitrous acid pre-treatments and solvent-based Soxhlet extraction, respectively. Processing increased algae methane yield between 29% and 37% compared to raw algae (VS basis), but reduced the amount of algae available for digestion. Co-digestion experiments showed a synergy between pig manure and raw algae that increased raw algae methane yield from 0.163 to 0.245m(3)CH4kg(-1)VS. No such synergy was observed when algal residues were co-digested with pig manure. Finally, experimental results were used to develop a high-level concept for an integrated biorefinery processing pig manure and onsite cultivated algae, evaluating methane production and co-product recovery per mass of pig manure entering the refinery. PMID:25643955

Astals, S; Musenze, R S; Bai, X; Tannock, S; Tait, S; Pratt, S; Jensen, P D



Is phytoremediation without biomass valorization sustainable? - comparative LCA of landfilling vs. anaerobic co-digestion.  


This study examines the sustainability of phytoremediation for soils contaminated with heavy metals, especially the influence of management of the produced metal-enriched biomass on the environmental performance of the complete system. We examine a case study in Asturias (north of Spain), where the land was polluted with Pb by diffuse emissions from an adjacent steelmaking factory. A Phytoremediation scenario based on this case was assessed by performing a comparative life cycle assessment and by applying the multi-impact assessment method ReCiPe. Our Baseline scenario used the produced biomass as feedstock for an anaerobic digester that produces biogas, which is later upgraded cryogenically. The Baseline scenario was compared with two alternative scenarios: one considers depositing the produced biomass into landfill, and the other considers excavating the contaminated soil, disposing it in a landfill, and refilling the site with pristine soil. A sensitivity analysis was performed using different yields of biomass and biogas, and using different distances between site and biomass valorization/disposal center. Our results show that the impacts caused during agricultural activities and biomass valorization were compensated by the production of synthetic natural gas and the avoided impact of natural gas production. In addition, it was found that if the produced biomass was not valorized, the sustainability of phytoremediation is questionable. The distance between the site and the biomass processing center is not a major factor for determining the technology's sustainability, providing distances are less than 200-300 km. However, distance to landfill or to the source of pristine soil is a key factor when deciding to use phytoremediation or other ex-situ conventional remediation techniques. PMID:25461087

Vigil, Miguel; Marey-Pérez, Manuel F; Martinez Huerta, Gemma; Álvarez Cabal, Valeriano



Continuously-stirred Anaerobic Digester to Convert Organic Wastes into Biogas: System Setup and Basic Operation  

PubMed Central

Anaerobic digestion (AD) is a bioprocess that is commonly used to convert complex organic wastes into a useful biogas with methane as the energy carrier 1-3. Increasingly, AD is being used in industrial, agricultural, and municipal waste(water) treatment applications 4,5. The use of AD technology allows plant operators to reduce waste disposal costs and offset energy utility expenses. In addition to treating organic wastes, energy crops are being converted into the energy carrier methane 6,7. As the application of AD technology broadens for the treatment of new substrates and co-substrate mixtures 8, so does the demand for a reliable testing methodology at the pilot- and laboratory-scale. Anaerobic digestion systems have a variety of configurations, including the continuously stirred tank reactor (CSTR), plug flow (PF), and anaerobic sequencing batch reactor (ASBR) configurations 9. The CSTR is frequently used in research due to its simplicity in design and operation, but also for its advantages in experimentation. Compared to other configurations, the CSTR provides greater uniformity of system parameters, such as temperature, mixing, chemical concentration, and substrate concentration. Ultimately, when designing a full-scale reactor, the optimum reactor configuration will depend on the character of a given substrate among many other nontechnical considerations. However, all configurations share fundamental design features and operating parameters that render the CSTR appropriate for most preliminary assessments. If researchers and engineers use an influent stream with relatively high concentrations of solids, then lab-scale bioreactor configurations cannot be fed continuously due to plugging problems of lab-scale pumps with solids or settling of solids in tubing. For that scenario with continuous mixing requirements, lab-scale bioreactors are fed periodically and we refer to such configurations as continuously stirred anaerobic digesters (CSADs). This article presents a general methodology for constructing, inoculating, operating, and monitoring a CSAD system for the purpose of testing the suitability of a given organic substrate for long-term anaerobic digestion. The construction section of this article will cover building the lab-scale reactor system. The inoculation section will explain how to create an anaerobic environment suitable for seeding with an active methanogenic inoculum. The operating section will cover operation, maintenance, and troubleshooting. The monitoring section will introduce testing protocols using standard analyses. The use of these measures is necessary for reliable experimental assessments of substrate suitability for AD. This protocol should provide greater protection against a common mistake made in AD studies, which is to conclude that reactor failure was caused by the substrate in use, when really it was improper user operation 10. PMID:22824993

Usack, Joseph G.; Spirito, Catherine M.; Angenent, Largus T.



Feasibility of anaerobic co-digestion of poultry blood with maize residues.  


The potential of anaerobic digestion for the treatment of poultry blood was evaluated in batch assays at laboratory scale and in a mesophilic semi-continuously fed digester. The biodegradability test performed on poultry blood waste showed a strong inhibition. Maize residues were used as co-substrate to overcome inhibition thanks to nitrogen dilution. Under batch operation, increasing the maize concentration from 15% to 70% (volatile solids (VS) basis) provided an increase of biogas from 130±31 to 188±21 L CH4/kg VS. In the semi-continuous mesophilic anaerobic digester, the biogas yield was 165±17 L CH4/kg VS fed, as a result of strong volatile fatty acid (VFA) accumulation. Although physical modifications of maize particles were observed by Scanning Electron Microscopy (SEM), an incomplete degradation was confirmed from analysis of digestates. Furthermore, Fourier Transform Infrared (FTIR) spectroscopy analysis demonstrated that along with VFA build-up, an accumulation of non-degraded materials took place. PMID:23899572

Cuetos, M J; Gómez, X; Martínez, E J; Fierro, J; Otero, M



Performance of methanogenic reactors in temperature phased two-stage anaerobic digestion of swine wastewater.  


The present study investigated the shifts in the chemical profiles of a two-phase anaerobic digestion system in methanogenic and acidogenic reactors for the treatment of swine wastewater. Acidogenic and methanogenic digesters were used with overall HRTs ranging from 27 to 6 d. In the optimized thermophilic/acidogenic phase throughout the entire experimental period, VS was reduced by 13.8% (1.6%); however, COD hardly decreased because of the thermophilic hydrolysis of organic materials, such as carbohydrates, proteins, and lipids, without any significant consumption of volatile fatty acids. In the methanogenic/mesophilic phase, COD was reduced by 65.8 (1.1)% compared to a 47.4 (2.9)% reduction in VS reduction efficiency with the gradual increase in methane production during a methanogenic HRT between 25 and 10 d. A high protein degradation rate was observed in the optimized acidogenic phase, which is assumed to be due to the low content of carbohydrates in raw swine wastewater as well as the readily thermophilic hydrolysis of proteins. Two-phase systems of anaerobic digestion consisting of optimized thermophilic and mesophilic methanogenic digesters showed a stable performance with respect to VS reduction efficiency with OLRs less than 3 g VS/L·d, in other words, more than 10 days of methanogenic HRT in this study. PMID:23041140

Kim, Woong; Shin, Seung Gu; Cho, Kyungjin; Lee, Changsoo; Hwang, Seokhwan



Pharmaceutical residues in sewage sludge: Effect of sanitization and anaerobic digestion.  


The fate of pharmaceutical residues in treatment of WWTP sludge was evaluated during mesophilic anaerobic digestion (AD) and six sanitization technologies (pasteurization, thermal hydrolysis, advanced oxidation processes using Fenton's reaction, ammonia treatment, thermophilic dry digestion, and thermophilic anaerobic digestion). Sludge spiked with a selection of 13 substances was used and in total 23 substances were detected. A correlation between substance lipophilicity and sludge partitioning was found after sample centrifugation, with e.g., SSRI drugs (90-99%) and estrogens (96-98%) mainly found in the solid phase. A correlation between lipophilicity and persistence of pharmaceutical residues during AD was also detected, indicating that hydrophobic substances are less available to degrading microorganisms. Overall, AD was found to be the most effective technology in reducing a wide spectrum of organic substances (in average ca 30% reduction). Similar effects were obtained for both AD treatments, suggesting that temperature (mesophilic or thermophilic) is less important for micropollutant reduction. Advanced oxidation processes using Fenton's reaction also affected several compounds, including substances showing general stability over the range of treatments such as carbamazepine, propranolol, and sertraline. Pasteurization, ammonia treatment, and thermophilic dry digestion exhibited relatively modest reductions. Interestingly, only thermal hydrolysis efficiently removed the ecotoxicologically potent estrogenic compounds from the sludge. PMID:25645950

Malmborg, Jonas; Magnér, Jörgen



Influence of hydrothermal pretreatment on microalgal biomass anaerobic digestion and bioenergy production.  


Microalgal biomass grown in wastewater treatment raceway ponds may be valorised producing bioenergy through anaerobic digestion. However, pretreatment techniques seem to be necessary for enhancing microalgae methane yield. In this study, hydrothermal pretreatment was studied prior to batch and continuous reactors. The pretreatment increased organic matter solubilisation (8-13%), anaerobic digestion rate (30-90%) and final methane yield (17-39%) in batch tests. The highest increase was attained with the pretreatment at 130 °C for 15 min, which was attested in a laboratory-scale continuous reactor operated at a hydraulic retention time of 20 days with an average organic loading rate of 0.7 g VS/L·day. The methane yield increased from 0.12 to 0.17 L CH?/g VS (41%) in the pretreated digester as compared to the control. Microscopic images of microalgal biomass showed that pretreated cells had unstructured organelles and disrupted cell wall external layer, which may enhance the hydrolysis. Indeed, images of the pretreated reactor digestate showed how cells were more degraded than in the control reactor. PMID:25462743

Passos, Fabiana; Ferrer, Ivet



Biological nutrients removal from the supernatant originating from the anaerobic digestion of the organic fraction of municipal solid waste.  


This study critically evaluates the biological processes and techniques applied to remove nitrogen and phosphorus from the anaerobic supernatant produced from the treatment of the organic fraction of municipal solid waste (OFMSW) and from its co-digestion with other biodegradable organic waste (BOW) streams. The wide application of anaerobic digestion for the treatment of several organic waste streams results in the production of high quantities of anaerobic effluents. Such effluents are characterized by high nutrient content, because organic and particulate nitrogen and phosphorus are hydrolyzed in the anaerobic digestion process. Consequently, adequate post-treatment is required in order to comply with the existing land application and discharge legislation in the European Union countries. This may include physicochemical and biological processes, with the latter being more advantageous due to their lower cost. Nitrogen removal is accomplished through the conventional nitrification/denitrification, nitritation/denitritation and the complete autotrophic nitrogen removal process; the latter is accomplished by nitritation coupled with the anoxic ammonium oxidation process. As anaerobic digestion effluents are characterized by low COD/TKN ratio, conventional denitrification/nitrification is not an attractive option; short-cut nitrogen removal processes are more promising. Both suspended and attached growth processes have been employed to treat the anaerobic supernatant. Specifically, the sequencing batch reactor, the membrane bioreactor, the conventional activated sludge and the moving bed biofilm reactor processes have been investigated. Physicochemical phosphorus removal via struvite precipitation has been extensively examined. Enhanced biological phosphorus removal from the anaerobic supernatant can take place through the sequencing anaerobic/aerobic process. More recently, denitrifying phosphorus removal via nitrite or nitrate has been explored. The removal of phosphorus from the anaerobic supernatant of OFMSW is an interesting research topic that has not yet been explored. At the moment, standardization in the design of facilities that treat anaerobic supernatant produced from the treatment of OFMSW is still under development. To move toward this direction, it is first necessary to assess the performance of alternative treatment options. It study concentrates existing data regarding the characteristics of the anaerobic supernatant produced from the treatment of OFMSW and from their co-digestion with other BOW. This provides data documenting the effect of the anaerobic digestion operating conditions on the supernatant quality and critically evaluates alternative options for the post-treatment of the liquid fraction produced from the anaerobic digestion process. PMID:23808751

Malamis, S; Katsou, E; Di Fabio, S; Bolzonella, D; Fatone, F



Anaerobic co-digestion of table olive debittering & washing effluent, cattle manure and pig manure in batch and high volume laboratory anaerobic digesters: effect of temperature.  


The prospective of table olive debittering & washing Effluent (DWE) as feed stock wastewater for anaerobic digestion (AD) systems was investigated in batch and continuous systems together with cattle and pig manures. While DWE considered unsuitable for biological treatment methods due to its unbalanced nature, the co-digestion of the wastewaters resulted in a 50% increase in the methane production/gram volatile solids(added) (CH(4)/gVS(added)), accompanied by 30% phenol reduction and 80% total organic carbon removal (TOC). pH increase during the co-digestion period was not identified as an inhibitory factor and all reactors were able to withstand this operational condition change. Moreover, no volatile fatty acid (VFA) accumulation was observed, indicating that the reactors were not operating under stress-overloading state. Under thermophilic conditions a 7% increase on the TOC removal efficiency was achieved when compared to the mesophilic systems while, under mesophilic conditions phenolic compounds reduction was 10% higher compared to the thermophilic systems. PMID:21334877

Zarkadas, Ioannis S; Pilidis, George A



Effect of microwave hydrolysis on transformation of steroidal hormones during anaerobic digestion of municipal sludge cake.  


Fate and removal of 16 steroidal (estrogenic, androgenic and progestogenic) hormones were studied during advanced anaerobic digestion of sludge cake using microwave (MW) pretreatment. Effect of pretreatment temperature (80, 120, 160 °C), operating temperature (mesophilic at 35 ± 2 °C, thermophilic at 55 ± 2 °C) and sludge retention time (SRT: 20, 10, 5 days) were studied employing eight lab-scale semi-continuously fed digesters. To determine the potential effect of MW hydrolysis, hormones were quantified in total (sorbed + soluble) and supernatant (soluble) phases of the digester influent and effluent streams. Seven of 16 hormones were above the method reporting limit (RL) in one or more of the samples. Hormone concentrations in total phase of un-pretreated (control) and pretreated digester feeds ranged in <157-2491 ng/L and <157-749 ng/L, respectively. The three studied factors were found to be statistically significant (95% confidence level) in removal of one or more hormones from soluble and/or total phase. MW hydrolysis of the influent resulted in both release (from sludge matrix) and attenuation of hormones in the soluble phase. Accumulation of estrone (E1) as well as progesterone (Pr) and androstenedione (Ad) in most of the digesters indicated possible microbial transformations among the hormones. Compared to controls, all pretreated digesters had lower total hormone concentrations in their influent streams. At 20 days SRT, highest total removal (E1+E2+Ad +Pr) was observed for the thermophilic control digester (56%), followed by pretreated mesophilic digesters at 120 °C and 160 °C with around 48% efficiency. In terms of conventional performance parameters, relative (to control) improvements of MW pretreated digesters at a 5-d SRT ranged in 98-163% and 57-121%, for volatile solids removal and methane production, respectively. PMID:23866136

Hamid, Hanna; Eskicioglu, Cigdem



Potential use of duckweed based anaerobic digester effluent as a feed source for heterotrophic growth of micro-algae  

NASA Astrophysics Data System (ADS)

Finding an alternative source of energy for the growing world's demand is a challenging task being considered by many scientists. Various types of renewable energy alternatives are being investigated by researchers around the world. The abundance of duckweed (i.e., Lemna and Wolfia sp.) in wetlands and wastewater lagoons, their rapid growth, and their capacity for nutrient, metal and other contaminant removal from wastewater suggests their potential as an inexpensive source of biomass for biofuel production. Another source of biomass for biofuel and energy production is micro-algae. The large-scale growth of micro-algae can potentially be achieved in a smaller footprint and at a higher rate and lower cost via heterotrophic growth compared to autotrophic growth for specific species that can grow under both conditions. Here we describe two types of research. First, two lab-scale, 5 L anaerobic digesters containing municipal raw wastewater that were set up, maintained and monitored over the course of 6 months using duckweed as the feed source. The pH, salinity, amount of gas production and gas composition were measured on a daily basis. The results from these measurements show that duckweed can be used as a good source of biofuel production in the form of methane gas. The second set of reactors consisted of two 1 L batch fed reactors containing algae (Chlorella vulgaris) grown in the lab environment heterotrophically. The pH and DO were monitored on a daily basis in order to investigate their effect on algae growth. Lipid analysis of the harvested algal biomass was done to investigate the efficiency of harvestable biofuel products. A nutrient solution containing glucose as an energy source was used as the initial feed solution, and the potential substitution of the glucose solution with the organic carbon residue from the duckweed digester effluent was investigated. Methane production, carbon stabilization, and gas composition results from the duckweed fed anaerobic digesters, and the growth and biolipid production of heterotrophic micro-algae fed pure substrate versus residual digester effluent carbon are discussed in detail in this study.

Ahmadi, L.; Dupont, R.



Impact of pretreatment on solid state anaerobic digestion of yard waste for biogas production.  


Solid state anaerobic digestion, as a safe and environment-friendly technology to dispose municipal solid wastes, can produce methane and reduce the volume of wastes. In order to raise the digestion efficiency, this study investigated the pretreatment of yard waste by thermal or chemical method to break down the complex lignocellulosic structure. The composition and structure of pretreated yard waste were analyzed and characterized. The results showed that the pretreatment decreased the content of cellulose and hemicelluloses in yard waste and in turn improved the hydrolysis and methanogenic processes. The thermal pretreatment sample (P1) had the highest methane yield, by increasing 88% in comparison with digesting the raw material. The maximum biogas production reached 253 mL/g volatile solids (VS). The largest substrate mass reduction was obtained by the alkaline pretreatment (P5). The VS of the alkaline-treated sample decreased about 60% in comparison with the raw material. PMID:23996635

Zhang, Zhikai; Li, Wangliang; Zhang, Guangyi; Xu, Guangwen



Co-occurence of Crenarchaeota, Thermoplasmata and methanogens in anaerobic sludge digesters.  


16S rRNA Crenarchaeota and Thermoplasmata sequences retrieved from 22 anaerobic digesters were analysed. 4.8 and 0.53 % of archaeal sequences were simultaneously affiliated to these lineages. A core of 2 operational taxonomic units (OTUs) representing 0.6 to -33.6 % of all archaeal sequences were defined for the Crenarchaeotes and identified to already known but not yet cultivable organisms in almost half of the digesters sampled. For the Thermoplasmata, apparently less abundant with 0.7 to -4.7 % of the archaeal sequences, 3 OTUs were identified. We showed here that Crenarchaeotes coexist with methanogens and are particularly abundant when Arch I lineage (also called WSA2 by Hugenholtz) is dominant in digesters. Moreover, Thermoplasmata were detected when Crenarchaeota were present. Interactions between methanogens, Crenarchaeotea and Thermoplamata were thus discussed. PMID:25739565

Chouari, Rakia; Guermazi, Sonda; Sghir, Abdelghani



Removal of heavy metals from aqueous solution by biochars derived from anaerobically digested biomass.  


This study examined the ability of two biochars converted from anaerobically digested biomass to sorb heavy metals using a range of laboratory sorption and characterization experiments. Initial evaluation of DAWC (digested dairy waste biochar) and DWSBC (digested whole sugar beet biochar) showed that both biochars were effective in removing a mixture of four heavy metals (Pb(2 +), Cu(2+), Ni(2+), and Cd(2+)) from aqueous solutions. Compared to DAWC, DWSBC demonstrated a better ability to remove Ni and Cd. Further investigations of lead sorption by the two biochars indicated that the removal was mainly through a surface precipitation mechanism, which was confirmed by batch sorption experiments, mathematical modeling, and examinations of lead-laden biochars samples using SEM-EDS, XRD, and FTIR. The lead sorption capacity of the two biochars was close to or higher than 200mmol/kg, which is comparable to that of commercial activated carbons. PMID:22325901

Inyang, Mandu; Gao, Bin; Yao, Ying; Xue, Yingwen; Zimmerman, Andrew R; Pullammanappallil, Pratap; Cao, Xinde



Green job bio-aerosol exposure during anaerobic digestion for biomass energetic valorisation.  


The continued expansion of the green economy increases the risk profile for green occupational jobs. One of the broadest green sectors in terms of growth is the anaerobic digestion of biomasses. In recent years, this development has also interested Italian regions. The management of biomass includes biological risk and the risk of particulate and endotoxin exposure. In the present study, we evaluated airborne exposure for anaerobic digestion workers at two real-scale plants. Digested biomass has different origins, ranging from cattle sludge and manure to poultry manure to agricultural harvesting or processing residues, particularly from maize and fruits. Two sampling points were chosen: at the first, the input biomasses were stored, and the hopper was loaded; at the second, the digested sludge exited the digester. The microbiological parameters, assessed using an active sampler and cultural method, were the total bacteria counts (at 22, 37, and 55°C), yeasts, fungi, Pseudomonaceae, Clostridia spp., Enterobacteriaceae and Actinomycetes. Moreover, at the same sampling points, we evaluated six PM10 fraction levels (10.0-7.2, 7.2-3.0, 3.0-1.5, 1.5-0.95, 0.95-0.49, and <0.49µm) and the endotoxin content of each fraction. In this investigation, the microbe contamination of the air varied from low to high levels, while the PM10 and endotoxin levels were limited, reaching rural environmental levels (61.40µg/m(3) and 18.88EU/m(3), respectively). However, contamination and occupational risk must be evaluated individually for each plant because numerous variables influence the risk magnitude, particularly digested sludge treatments, such as input biomass nature, storage, movement conditions, building configuration and technological processes. PMID:25791865

Traversi, Deborah; Gorrasi, Ilaria; Bonetta, Sara; Leinardi, Riccardo; Pietrangeli, Biancamaria; Carraro, Elisabetta; Gilli, Giorgio



Digestion of frozen/thawed food waste in the hybrid anaerobic solid-liquid system  

SciTech Connect

The hybrid anaerobic solid-liquid (HASL) system, which is a modified two-phase anaerobic digester, is to be used in an industrial scale operation to minimize disposal of food waste at incineration plants in Singapore. The aim of the present research was to evaluate freezing/thawing of food waste as a pre-treatment for its anaerobic digestion in the HASL system. The hydrolytic and fermentation processes in the acidogenic reactor were enhanced when food waste was frozen for 24 h at -20 deg. C and then thawed for 12 h at 25 deg. C (experiment) in comparison with fresh food waste (control). The highest dissolved COD concentrations in the leachate from the acidogenic reactors were 16.9 g/l on day 3 in the control and 18.9 g/l on day 1 in the experiment. The highest VFA concentrations in the leachate from the acidogenic reactors were 11.7 g/l on day 3 in the control and 17.0 g/l on day 1 in the experiment. The same volume of methane was produced during 12 days in the control and 7 days in the experiment. It gave the opportunity to diminish operational time of batch process by 42%. The effect of freezing/thawing of food waste as pre-treatment for its anaerobic digestion in the HASL system was comparable with that of thermal pre-treatment of food waste at 150 deg. C for 1 h. However, estimation of energy required either to heat the suspended food waste to 150 deg. C or to freeze the same quantity of food waste to -20 deg. C showed that freezing pre-treatment consumes about 3 times less energy than thermal pre-treatment.

Stabnikova, O. [School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore)], E-mail:; Liu, X.Y.; Wang, J.Y. [School of Civil and Environmental Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore)



Enhanced anaerobic treatment of CSTR-digested effluent from chicken manure: The effect of ammonia inhibition  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Enhanced anaerobic treatment of CSTR-digested effluent from chicken manure. Black-Right-Pointing-Pointer The SCOD/TAN (soluble COD/total ammonia nitrogen) ratio was key controlling factor. Black-Right-Pointing-Pointer The threshold of the SCOD/TAN ratio was 2.4 at an influent pH of 8.5-9. - Abstract: The effect of ammonia inhibition was evaluated during the enhanced anaerobic treatment of digested effluent from a 700 m{sup 3} chicken-manure continuous stirred tank reactor (CSTR). A 12.3 L internal circulation (IC) reactor inoculated with an anaerobic granular sludge and operated at 35 {+-} 1 Degree-Sign C was employed for the investigation. With a corresponding organic loading rate of 1.5-3.5 kg-COD/m{sup 3} d over a hydraulic retention time of 1.5 d, a maximum volumetric biogas production rate of 1.2 m{sup 3}/m{sup 3} d and TCOD (total COD) removal efficiency ranging from 70% to 80% was achieved. However, the continual increase in the influent TAN content led to ammonia inhibition in the methanogenesis system. The SCOD/TAN (soluble COD/total ammonia nitrogen) ratio was presented to be the key controlling factor for the anaerobic treatment of semi-digested chicken manure, and further validation through shock loading and ammonia inhibition experiments was conducted. The threshold value of the SCOD/TAN ratio was determined to be 2.4 (corresponding to a TAN of 1250 mg/L) at an influent pH of 8.5-9.

Liu Zhanguang; Zhou Xuefei [Key Laboratory of Yangtze Water Environment of Ministry of Education, State Key Laboratory of Pollution and Resource Reuse, Tongji University, Shanghai 200092 (China); Zhang Yalei, E-mail: [Key Laboratory of Yangtze Water Environment of Ministry of Education, State Key Laboratory of Pollution and Resource Reuse, Tongji University, Shanghai 200092 (China); Zhu Hongguang [Institute of Modern Agricultural Science and Engineering, National Engineering Research Center of Protected Agriculture, Tongji University, Shanghai 200092 (China)



Effect of sulfate on low-temperature anaerobic digestion.  


The effect of sulfate addition on the stability of, and microbial community behavior in, low-temperature anaerobic expanded granular sludge bed-based bioreactors was investigated at 15°C. Efficient bioreactor performance was observed, with chemical oxygen demand (COD) removal efficiencies of >90%, and a mean SO(2-) 4 removal rate of 98.3%. In situ methanogensis appeared unaffected at a COD: SO(2-) 4 influent ratio of 8:1, and subsequently of 3:1, and was impacted marginally only when the COD: SO(2-) 4 ratio was 1:2. Specific methanogenic activity assays indicated a complex set of interactions between sulfate-reducing bacteria (SRB), methanogens and homoacetogenic bacteria. SO(2-) 4 addition resulted in predominantly acetoclastic, rather than hydrogenotrophic, methanogenesis until >600 days of SO(2-) 4-influenced bioreactor operation. Temporal microbial community development was monitored by denaturation gradient gel electrophoresis (DGGE) of 16S rRNA genes. Fluorescence in situ hybridizations (FISH), qPCR and microsensor analysis were combined to investigate the distribution of microbial groups, and particularly SRB and methanogens, along the structure of granular biofilms. qPCR data indicated that sulfidogenic genes were present in methanogenic and sulfidogenic biofilms, indicating the potential for sulfate reduction even in bioreactors not exposed to SO(2-) 4. Although the architecture of methanogenic and sulfidogenic granules was similar, indicating the presence of SRB even in methanogenic systems, FISH with rRNA targets found that the SRB were more abundant in the sulfidogenic biofilms. Methanosaeta species were the predominant, keystone members of the archaeal community, with the complete absence of the Methanosarcina species in the experimental bioreactor by trial conclusion. Microsensor data suggested the ordered distribution of sulfate reduction and sulfide accumulation, even in methanogenic granules. PMID:25120534

Madden, Pádhraig; Al-Raei, Abdul M; Enright, Anne M; Chinalia, Fabio A; de Beer, Dirk; O'Flaherty, Vincent; Collins, Gavin



SHORT COMMUNICATION Gas-Phase Separations of Protease Digests  

E-print Network

SHORT COMMUNICATION Gas-Phase Separations of Protease Digests Stephen J. Valentine, Anne E University, Bloomington, Indiana, USA A mixture of peptides from a complete tryptic digest of ubiquitin has and identify peptides from a tryptic digest of ubiquitin. The mixture was electrosprayed into the gas phase

Clemmer, David E.


Anaerobic co-digestion of cattle manure with rice straw: economic & energy feasibility.  


Rice straw (RS) is one of the most abundant wastes generated in Valencia (Spain). Traditional waste disposal methods are harmful to the environment. The straw burning emits large amounts of toxic air pollutants and the straw burying produces uncontrolled anaerobic fermentation in the soil. The aim of this research was to evaluate the feasibility of cow manure anaerobic co-digestion with RS in a semi-continuous plug flow pilot-scale reactor. Three different periods of co-digestion were carried out as the RS dose was increased. When the addition of RS was 1, 2 and 5% (on weight basis) the biogas productivity increased by 4, 28 and 54% respectively. Furthermore, economic and energy feasibility were analysed considering the logistics cost of the RS (baling, collection, crushing and transportation). Two different scenarios were analysed. In scenario 1, the anaerobic co-digestion process was considered that take place in a new biogas installation, and in scenario 2 the process was considered that take place in a biogas plant already in operation. In scenario 1, the cow manure co-digestion with 2% of RS in a biogas installation of 500 kW showed the best economic analysis (net present value of 13.23%). In scenario 2, the results showed that the maximum distance between the rice field and the biogas plant that produces a positive economic balance was less than 95 km (2% RS) and 74 km (5% RS). In the case of the addition of 1% RS the economic balance is negative. Energy balance is positive in the three mixtures analysed. PMID:23306251

Silvestre, G; Gómez, M P; Pascual, A; Ruiz, B



Evaluation of the biomethane potential from multiple waste streams for a proposed community scale anaerobic digester.  


This paper examines the biomethane potential from organic waste for a proposed community scale anaerobic digester in a rural town. The biomethane potential test is used to assess the suitability of waste streams for biomethane production and to examine the variation in biomethane potential between waste sub-streams. A methodology for accurately estimating the biomethane potential from multiple heterogeneous organic waste substrates is sought. Five main waste streams were identified as possible substrates for biogas production, namely Abattoir waste (consisting of paunch and de-watered activated sludge); cheese factory effluent; commercial and domestic food waste; pig slurry and waste water treatment sludge. The biomethane potential of these waste streams ranged from as low as 99 L CH4 kg VS(-1) for pig slurry to as high as 787 L CH4 kg VS(-1) for dissolved air floatation (DAF) sludge from a cheese effluent treatment plant. The kinetic behaviour of the biomethane production in the batch test is also examined. The objective of the paper is to suggest an optimum substrate mix in terms of biomethane yield per unit substrate for the proposed anaerobic digester. This should maximize the yield of biomethane per capital investment. Food waste displayed the highest biomethane yield (128 m(n)(3) t(-1)) followed by cheese waste (38 m(n)(3) t(-1)) and abattoir waste (36 m(n)(3) t(-1)). It was suggested that waste water sludge (16 m(n)(3) t(-1)) and pig slurry (4 m(n)(3) t(-1)) should not be digested. However, the biomethane potential test does not give information on the continuous operation of an anaerobic digester. PMID:24350456

Browne, James D; Allen, Eoin; Murphy, Jerry D



Dynamics of biofilm formation during anaerobic digestion of organic waste.  


Biofilm-based reactors are effectively used for wastewater treatment but are not common in biogas production. This study investigated biofilm dynamics on biofilm carriers incubated in batch biogas reactors at high and low organic loading rates for sludge from meat industry dissolved air flotation units. Biofilm formation and dynamics were studied using various microscopic techniques. Resulting micrographs were analysed for total cell numbers, thickness of biofilms, biofilm-covered surface area, and the area covered by extracellular polymeric substances (EPS). Cell numbers within biofilms (10(11) cells ml(-1)) were up to one order of magnitude higher compared to the numbers of cells in the fluid reactor content. Further, biofilm formation and structure mainly correlated with the numbers of microorganisms present in the fluid reactor content and the organic loading. At high organic loading (45 kg VS m(-3)), the thickness of the continuous biofilm layer ranged from 5 to 160 ?m with an average of 51 ?m and a median of 26 ?m. Conversely, at lower organic loading (15 kg VS m(-3)), only microcolonies were detectable. Those microcolonies increased in their frequency of occurrence during ongoing fermentation. Independently from the organic loading rate, biofilms were embedded completely in EPS within seven days. The maturation and maintenance of biofilms changed during the batch fermentation due to decreasing substrate availability. Concomitant, detachment of microorganisms within biofilms was observed simultaneously with the decrease of biogas formation. This study demonstrates that biofilms of high cell densities can enhance digestion of organic waste and have positive effects on biogas production. PMID:24342346

Langer, Susanne; Schropp, Daniel; Bengelsdorf, Frank R; Othman, Maazuza; Kazda, Marian



Kinetics and dynamic modelling of batch anaerobic digestion of municipal solid waste in a stirred reactor  

SciTech Connect

A series of batch, slurry anaerobic digestion experiments were performed where the soluble and insoluble fractions, and unwashed MSW were separately digested in a 200 l stirred stainless steel vessel at a pH of 7.2 and a temperature of 38 deg. C. It was found that 7% of the total MSW COD was readily soluble, of which 80% was converted to biogas; 50% of the insoluble fraction was solubilised, of this only 80% was converted to biogas. The rate of digesting the insoluble fraction was about four times slower than the rate of digesting the soluble fraction; 48% of the total COD was converted to biogas and 40% of the total nitrogen was converted to ammonia. Soluble and insoluble fractions were broken down simultaneously. The minimum time to convert 95% of the degradable fraction to biogas was 20 days. The lag phase for the degradation of insoluble fraction of MSW can be overcome by acclimatising the culture with the soluble fraction. The rate of digestion and the methane yield was not affected by particle size (within the range of 2-50 mm). A dynamic model was developed to describe batch digestion of MSW. The parameters of the model were estimated using data from the separate digestion of soluble and insoluble fractions and validated against data from the digestion of unwashed MSW. Trends in the specific aceticlastic and formate-utilising methanogenic activity were used to estimate initial methanogenic biomass concentration and bacterial death rate coefficient. The kinetics of hydrolysis of insoluble fraction could be adequately described by a Contois equation and the kinetics of acidogenesis, and aceticlastic and hydrogen utilising methanogenesis by Monod equations.

Nopharatana, Annop [Division of Environmental of Engineering, The University of Queensland, Brisbane, Qld. 4072 (Australia); Pilot Plant Development and Training Institute, King Mongkut's University of Technology, Thonburi, Bangkok 10150 (Thailand); Pullammanappallil, Pratap C. [Division of Environmental of Engineering, The University of Queensland, Brisbane, Qld. 4072 (Australia); Department of Agricultural and Biological Engineering, University of Florida, Gainesville, FL 32611 (United States); Clarke, William P. [Division of Environmental of Engineering, The University of Queensland, Brisbane, Qld. 4072 (Australia)], E-mail:



Two-phase thermophilic anaerobic digestion process for biohythane production treating biowaste: preliminary results.  


This paper deals with the optimization of a two-phase anaerobic process treating biowaste for hydrogen and methane production. Neither physical nor chemical pre-treatments were used to optimize the process. The work was carried out at pilot scale, using two CSTRs (200 and 380 L working volume respectively) both maintained at thermophilic temperature (55 C) and fed semi-continuously with biowaste. The experiment was divided into three periods; during the first two periods the organic loading rate was maintained at 20 kg TVS/m3 d and the hydraulic retention time was changed from 6.6 to 3.3 days, while in the last period the digestate of the second reactor was recirculated to the first reactor in order to buffer the system and control pH at levels around 5. The HRT was maintained at 3.3 days and the OLR was decreased at 16.5 kg TVS/m3 d. The best yield was obtained in the last period where a specific hydrogen production of 50.9 L/kg VSfed was reached, with a H2 content in biogas from the first reactor of 36%. The methanogenic stage after the hydrogen conversion reached a specific biogas production of 0.62 m3/kg VSfed and an overall organic removal above 70%, without any stability problem. The overall biogas production was some 1.5 m3 per day with a gas composition of 10% H2 and 50% CH4. PMID:22097052

Cavinato, C; Bolzonella, D; Fatone, F; Giuliano, A; Pavan, P



Archaeal community composition affects the function of anaerobic co-digesters in response to organic overload.  


Microbial community diversity in two thermophilic laboratory-scale and three full-scale anaerobic co-digesters was analysed by genetic profiling based on PCR-amplified partial 16S rRNA genes. In parallel operated laboratory reactors a stepwise increase of the organic loading rate (OLR) resulted in a decrease of methane production and an accumulation of volatile fatty acids (VFAs). However, almost threefold different OLRs were necessary to inhibit the gas production in the reactors. During stable reactor performance, no significant differences in the bacterial community structures were detected, except for in the archaeal communities. Sequencing of archaeal PCR products revealed a dominance of the acetoclastic methanogen Methanosarcina thermophila, while hydrogenotrophic methanogens were of minor importance and differed additionally in their abundance between reactors. As a consequence of the perturbation, changes in bacterial and archaeal populations were observed. After organic overload, hydrogenotrophic methanogens (Methanospirillum hungatei and Methanoculleus receptaculi) became more dominant, especially in the reactor attributed by a higher OLR capacity. In addition, aggregates composed of mineral and organic layers formed during organic overload and indicated tight spatial relationships between minerals and microbial processes that may support de-acidification processes in over-acidified sludge. Comparative analyses of mesophilic stationary phase full-scale reactors additionally indicated a correlation between the diversity of methanogens and the VFA concentration combined with the methane yield. This study demonstrates that the coexistence of two types of methanogens, i.e. hydrogenotrophic and acetoclastic methanogens is necessary to respond successfully to perturbation and leads to stable process performance. PMID:22192420

Lerm, S; Kleyböcker, A; Miethling-Graff, R; Alawi, M; Kasina, M; Liebrich, M; Würdemann, H



Archaeal community composition affects the function of anaerobic co-digesters in response to organic overload  

SciTech Connect

Highlights: Black-Right-Pointing-Pointer Two types of methanogens are necessary to respond successfully to perturbation. Black-Right-Pointing-Pointer Diversity of methanogens correlates with the VFA concentration and methane yield. Black-Right-Pointing-Pointer Aggregates indicate tight spatial relationship between minerals and microorganisms. - Abstract: Microbial community diversity in two thermophilic laboratory-scale and three full-scale anaerobic co-digesters was analysed by genetic profiling based on PCR-amplified partial 16S rRNA genes. In parallel operated laboratory reactors a stepwise increase of the organic loading rate (OLR) resulted in a decrease of methane production and an accumulation of volatile fatty acids (VFAs). However, almost threefold different OLRs were necessary to inhibit the gas production in the reactors. During stable reactor performance, no significant differences in the bacterial community structures were detected, except for in the archaeal communities. Sequencing of archaeal PCR products revealed a dominance of the acetoclastic methanogen Methanosarcina thermophila, while hydrogenotrophic methanogens were of minor importance and differed additionally in their abundance between reactors. As a consequence of the perturbation, changes in bacterial and archaeal populations were observed. After organic overload, hydrogenotrophic methanogens (Methanospirillum hungatei and Methanoculleus receptaculi) became more dominant, especially in the reactor attributed by a higher OLR capacity. In addition, aggregates composed of mineral and organic layers formed during organic overload and indicated tight spatial relationships between minerals and microbial processes that may support de-acidification processes in over-acidified sludge. Comparative analyses of mesophilic stationary phase full-scale reactors additionally indicated a correlation between the diversity of methanogens and the VFA concentration combined with the methane yield. This study demonstrates that the coexistence of two types of methanogens, i.e. hydrogenotrophic and acetoclastic methanogens is necessary to respond successfully to perturbation and leads to stable process performance.

Lerm, S.; Kleyboecker, A. [International Centre for Geothermal Research (ICGR), GFZ German Research Centre for Geosciences, 14473 Potsdam (Germany); Miethling-Graff, R. [International Centre for Geothermal Research (ICGR), GFZ German Research Centre for Geosciences, 14473 Potsdam (Germany); Johann Heinrich von Thuenen Institut, Bundesforschungsinstitut fuer Laendliche Raeume, Wald und Fischerei Institut fuer Biodiversitaet, 38116 Braunschweig (Germany); Alawi, M.; Kasina, M.; Liebrich, M. [International Centre for Geothermal Research (ICGR), GFZ German Research Centre for Geosciences, 14473 Potsdam (Germany); Wuerdemann, H., E-mail: [International Centre for Geothermal Research (ICGR), GFZ German Research Centre for Geosciences, 14473 Potsdam (Germany)



Application of urea dosing for alkalinity supply during anaerobic digestion of vinasse.  


Pushed by demand for renewable energy, the ethanol industry in Brazil is expanding. However, production of 1 m(3) of ethanol generates around 13 m(3) of liquid residues (vinasse), so this expansion results in an increasing need for a more adequate destination of these residues. Nowadays the vinasse is dispersed on the sugar cane fields in the practice of fertirrigation, but anaerobic digestion of this residue may be a better solution, additionally offering an alternative source of energy, able to complement hydroelectric power supply in the dry season. However, when trying to digest vinasse at reduced hydraulic retention times, complications arise from its strong tendency toward acidification, upsetting the fragile balance of transformations normally occurring under anaerobic conditions. For successful operation of an anaerobic treatment process with acceptable hydraulic residence times, increasing alkalinity levels inside the reactor is neces-sary. In the present work we show that pH regulation by means of urea dosing, in spite of the risk posed by ammonia toxicity towards methanogenic biomass, can be a viable alternative to avoid vinasse acidification. The ammonia formed in urea conversion remains in solution, rather than escaping to the biogas, and so its use as fertiliser can offset its cost of application in the process. PMID:23032778

Boncz, M A; Formagini, E L; Santos, L da S; Marques, R D; Paulo, P L



The efficiency of concentration methods used to detect enteric viruses in anaerobically digested sludge  

PubMed Central

The presence of enteric viruses in biosolids can be underestimated due to the inefficient methods (mainly molecular methods) used to recover the viruses from these matrices. Therefore, the goal of this study was to evaluate the different methods used to recover adenoviruses (AdV), rotavirus species A (RVA), norovirus genogroup II (NoV GII) and the hepatitis A virus (HAV) from biosolid samples at a large urban wastewater treatment plant in Brazil after they had been treated by mesophilic anaerobic digestion. Quantitative polymerase chain reaction (PCR) was used for spiking experiments to compare the detection limits of feasible methods, such as beef extract elution and ultracentrifugation. Tests were performed to detect the inhibition levels and the bacteriophage PP7 was used as an internal control. The results showed that the inhibitors affected the efficiency of the PCR reaction and that beef extract elution is a suitable method for detecting enteric viruses, mainly AdV from biosolid samples. All of the viral groups were detected in the biosolid samples: AdV (90%), RVA, NoV GII (45%) and HAV (18%), indicating the viruses' resistance to the anaerobic treatment process. This is the first study in Brazil to detect the presence of RVA, AdV, NoV GII and HAV in anaerobically digested sludge, highlighting the importance of adequate waste management. PMID:23440119

Prado, Tatiana; Guilayn, Wilma de Carvalho Pereira Bonet; Gaspar, Ana Maria Coimbra; Miagostovich, Marize Pereira



The efficiency of concentration methods used to detect enteric viruses in anaerobically digested sludge.  


The presence of enteric viruses in biosolids can be underestimated due to the inefficient methods (mainly molecular methods) used to recover the viruses from these matrices. Therefore, the goal of this study was to evaluate the different methods used to recover adenoviruses (AdV), rotavirus species A (RVA), norovirus genogroup II (NoV GII) and the hepatitis A virus (HAV) from biosolid samples at a large urban wastewater treatment plant in Brazil after they had been treated by mesophilic anaerobic digestion. Quantitative polymerase chain reaction (PCR) was used for spiking experiments to compare the detection limits of feasible methods, such as beef extract elution and ultracentrifugation. Tests were performed to detect the inhibition levels and the bacteriophage PP7 was used as an internal control. The results showed that the inhibitors affected the efficiency of the PCR reaction and that beef extract elution is a suitable method for detecting enteric viruses, mainly AdV from biosolid samples. All of the viral groups were detected in the biosolid samples: AdV (90%), RVA, NoV GII (45%) and HAV (18%), indicating the viruses' resistance to the anaerobic treatment process. This is the first study in Brazil to detect the presence of RVA, AdV, NoV GII and HAV in anaerobically digested sludge, highlighting the importance of adequate waste management. PMID:23440119

Prado, Tatiana; Guilayn, Wilma de Carvalho Pereira Bonet; Gaspar, Ana Maria Coimbra; Miagostovich, Marize Pereira



Effect of potassium inhibition on the thermophilic anaerobic digestion of swine waste.  


The inhibition effects of high potassium concentration on thermophilic anaerobic digestion of swine waste were studied. A continuous stirred tank reactor (CSTR), operated at a hydraulic retention time of 10 days and chemical oxygen demand loading of 7.2 to 7.5 g/L/d, was used to digest swine waste and cultivate thermophilic anaerobic microorganisms. To evaluate the toxicity of potassium, batch inhibition tests were also conducted. Without acclimation to potassium, the inhibition threshold beyond which methane production decreased significantly was 3 g K+/L. Volatile fatty acids accumulation was observed during the decline of methane production. Propionic acid was the dominant fatty acid, indicating that propionic acid utilizers were more sensitive to potassium inhibition than acetoclastic methanogens. To test the effect of acclimation on potassium inhibition, the potassium concentration in the CSTR was increased to 6 and 9 g K+/L. Acclimation to 6 g K+/L increased the tolerance of anaerobic inocula to potassium inhibition without significantly reducing the methanogenic activity. The inhibition threshold was increased from 3 g K+/L for unacclimated inocula, to 6 g K+/L for inocula acclimated to 6 g/L of potassium. Acclimation of inocula to 9 g/L potassium further increased the inhibition threshold to 7.5 g K+/L. However, the overall methanogenic activity in the last case was lower than that of unacclimated and 6 g K+/L acclimated inocula. PMID:17605335

Chen, Ye; Cheng, Jay J



Psychrophilic dry anaerobic digestion of dairy cow feces: long-term operation.  


This paper reports experimental results which demonstrate psychrophilic dry anaerobic digestion of cow feces during long-term operation in sequence batch reactor. Cow feces (13-16% total solids) has been anaerobically digested in 12 successive cycles (252 days) at 21 days treatment cycle length (TCL) and temperature of 20 °C using psychrotrophic anaerobic mixed culture. An average specific methane yield (SMY) of 184.9 ± 24.0, 189.9 ± 27.3, and 222 ± 27.7 (N)L CH4 kg(-1) of VS fed has been achieved at an organic loading rate of 3.0, 4.0, and 5.0 g TCOD kg(-1) inoculum d(-1) and TCL of 21 days, respectively. The corresponding substrate to inoculum ratio (SIR) was 0.39 ± 0.06, 0.48 ± .02, 0.53 ± 0.05, respectively. Average methane production rate of 10 ± 1.4(N)L CH4 kg(-1) VS fed d(-1) has been obtained. The low concentration of volatile fatty acids indicated that hydrolysis was the reaction limiting step. PMID:25434732

Massé, Daniel I; Cata Saady, Noori M



Evaluation of single vs. staged mesophilic anaerobic digestion of kitchen waste with and without microwave pretreatment.  


Effects of single and dual stage (acidogenic-methanogenic) mesophilic anaerobic digestion (AD) of kitchen waste (KW) was evaluated at hydraulic retention times (HRTs) of 20, 15, 12 and 9 d with and without thermal microwave (MW) pretreatment (145 °C). Anaerobic acidification in terms of acid accumulation was superior compared to microaerophilic acidification. Maximum anaerobic acidification of KW was determined to occur with an HRT of 2 d which was then selected for the acidification stage. The dual stage AD system fed with untreated KW produced the maximum biogas and volatile solids (VS) stabilization efficiencies at the shortest HRT of 9 d. Conversely, for free liquid resulting from MW pretreatment of KW the two stage reactor at 20 d HRT produced three fold more methane compared with the untreated free liquid control. However, MW pretreatment and AD of the free liquid fraction only, was not a sustainable treatment option. For KW, staging of the AD process had a greater positive impact on waste stabilization and methane yield compared to single stage reactors or MW pretreatment. KW can be characterized as being a readily biodegradable solid waste; concomitantly it is recommended that digester staging without MW pretreatment be employed to maximize methane yield and production. PMID:23648266

Shahriari, Haleh; Warith, Mostafa; Hamoda, Mohamed; Kennedy, Kevin



Valorisation of biodiesel production wastes: Anaerobic digestion of residual Tetraselmis suecica biomass and co-digestion with glycerol.  


One of the principal opportunity areas in the development of the microalgal biodiesel industry is the energy recovery from the solid microalgal biomass residues to optimise the fuel production. This work reports the cumulative methane yields reached from the anaerobic digestion of the solid microalgal biomass residues using different types of inocula, reporting also the improvement of biogas production using the co-digestion of microalgal biomass with glycerol. Results demonstrate that the solid microalgal biomass residues showed better biogas production using a mesophilic inoculum, reaching almost two-fold higher methane production than under thermophilic conditions. Furthermore, the solid microalgal biomass residues methane production rate showed an increase from 173.78 ± 9.57 to 438.46 ± 40.50?mL of methane per gram of volatile solids, when the co-digestion with glycerol was performed. These results are crucial to improve the energy balance of the biodiesel production from Tetraselmis suecica, as well as proposing an alternative way to treat the wastes derived from the microalgae biodiesel production. PMID:25737140

Santos-Ballardo, David U; Font-Segura, Xavier; Ferrer, Antoni Sánchez; Barrena, Raquel; Rossi, Sergio; Valdez-Ortiz, Angel



Modeling a solar-heated anaerobic digester for the developing world using system dynamics  

NASA Astrophysics Data System (ADS)

Much of the developing world lacks access to a dependable source of energy. Agricultural societies such as Mozambique and Papua New Guinea could sustain a reliable energy source through the microbacterial decomposition of animal and crop waste. Anaerobic digestion produces methane, which can be used directly for heating, cooking, and lighting. Adding a solar component to the digester provides a catalyst for bacteria activity, accelerating digestion and increasing biogas production. Using methane decreases the amount of energy expended by collecting and preparing firewood, eliminates hazardous health effects linked to inhalation of particles, and provides energy close to where it is needed. The purpose of this work is two fold: initial efforts focus on the development and validation of a computer-based system dynamics model that combines elements of the anaerobic digestion process in order to predict methane output; second, the model is flexed to explore how the addition of a solar component increases robustness of the design, examines predicted biogas generation as a function of varying input conditions, and determines how best to configure such systems for use in varying developing world environments. Therefore, the central components of the system: solar insolation, waste feedstock, bacteria population and consumption rates, and biogas production are related both conceptually and mathematically through a serious of equations, conversions, and a causal loop and feedback diagram. Given contextual constraints and initial assumptions for both locations, it was determined that solar insolation and subsequent digester temperature control, amount of waste, and extreme weather patterns had the most significant impact on the system as a whole. Model behavior was both reproducible and comparable to that demonstrated in existing experimental systems. This tool can thus be flexed to fit specific contexts within the developing world to improve the standard of living of many people, without significantly altering everyday activities.

Bentley, Johanna Lynn


Electrokinetic removal of Cu and Zn in anaerobic digestate: Interrelation between metal speciation and electrokinetic treatments.  


In recent years, a potential controversy has arisen that whether the metal speciation in solid matrix determined its electrokinetic (EK) removal efficiency or by contrast. In present study, Cu and Zn in anaerobic digestate were selected as candidates to investigate the relation between the species of metal and EK treatment. The obtained results show that the removal efficiency for each fraction decreased in the order as follows: exchangeable?bound to carbonates>bound to Fe-Mn oxides>bound to organic matters>residual. For both Cu and Zn, their total removal performance was dependent on their dominant fraction in the digestate. A constant pH maintenance around the digestate via circulation of acid electrolyte is an optional operation because a strong acid atmosphere (pH<2) around the digestate can be formed automatically as EK time elapses. Despite that many reactions occurred during EK process, the species distribution of Cu and Zn in the digestate determined their total EK removal efficiency essentially. PMID:25562809

Zhu, Neng-Min; Chen, Mengjun; Guo, Xu-Jing; Hu, Guo-Quan; Yu-Deng



Winery waste recycling through anaerobic co-digestion with waste activated sludge.  


In this study biogas and high quality digestate were recovered from winery waste (wine lees) through anaerobic co-digestion with waste activated sludge both in mesophilic and thermophilic conditions. The two conditions studied showed similar yields (0.40 m(3)/kgCODfed) but different biological process stability: in fact the mesophilic process was clearly more stable than the thermophilic one in terms of bioprocess parameters. The resulting digestates showed good characteristics for both the tested conditions: heavy metals, dioxins (PCDD/F), and dioxin like bi-phenyls (PCBs) were concentred in the effluent if compared with the influent because of the important reduction of the solid dry matter, but remained at levels acceptable for agricultural reuse. Pathogens in digestate decreased. Best reductions were observed in thermophilic condition, while at 37°C the concentration of Escherichia coli was at concentrations level as high as 1000 UFC/g. Dewatering properties of digestates were evaluated by means of the capillary suction time (CST) and specific resistance to filtration (SRF) tests and it was found that a good dewatering level was achievable only when high doses of polymer (more than 25 g per kg dry solids) were added to sludge. PMID:25151445

Da Ros, C; Cavinato, C; Pavan, P; Bolzonella, D



Effect of anaerobic digestion at 35, 55 and 60 °C on pharmaceuticals and organic contaminants.  


The application of treated sewage sludge on farmland is a suggested method for recycling nutrients and reducing demand for commercial fertilizer. However, sludge needs to be safe from possible contaminants which can cause acute and long-term health and environmental problems. Residual pharmaceuticals and organic contaminants are mentioned as emerging threats since wastewater treatment plants are not designed to degrade these substances. The aim of this study was to screen and evaluate the presence, and reduction, of pharmaceuticals and polycyclic aromatic hydrocarbons (PAHs) during anaerobic digestion of mixed primary and waste-activated sludge at 35, 55 and 60 °C and during pasteurization at 70 °C. The study showed the difficulty of analysing pharmaceutical compounds in low concentrations in the sludge matrix. No general reduction of these compounds was seen during treatment, but for individual substances some reduction occurred. The PAHs were generally not reduced during digestion or pasteurization, but for three substances (indeno[1,2,3-cd]pyrene and dibenzo[a,h]anthracene (analysed together) and benzo[g,h,i]perylene) reduction (up to 60%) during digestion was seen. Digestion at 35 and 55 °C resulted in about the same order of reduction of the three individual PAHs, which was higher than for digestion at 60 °C. PMID:24647195

Davidsson, A; Kjerstadius, H; Haghighatafshar, S; Fick, J; Olsson, M; Wachtmeister, H; Eriksson, E; la Cour Jansen, J



A modified anaerobic digestion process with chemical sludge pre-treatment and its modelling.  


Activated Sludge Models (ASMs) assume an unbiodegradable organic particulate fraction in the activated sludge, which is derived from the decay of active microorganisms in the sludge and/or introduced from wastewater. In this study, a seasonal change of such activated sludge constituents in a municipal wastewater treatment plant was monitored for 1.5 years. The chemical oxygen demand ratio of the unbiodegradable particulates to the sludge showed a sinusoidal pattern ranging from 40 to 65% along with the change of water temperature in the plant that affected the decay rate. The biogas production in a laboratory-scale anaerobic digestion (AD) process was also affected by the unbiodegradable fraction in the activated sludge fed. Based on the results a chemical pre-treatment using H2O2 was conducted on the digestate to convert the unbiodegradable fraction to a biodegradable one. Once the pre-treated digestate was returned to the digester, the methane conversion increased up to 80% which was about 2.4 times as much as that of the conventional AD process, whilst 96% of volatile solids in the activated sludge was digested. From the experiment, the additional route of the organic conversion processes for the inert fraction at the pre-treatment stage was modelled on the ASM platform with reasonable simulation accuracy. PMID:24901631

Hai, N M; Sakamoto, S; Le, V C; Kim, H S; Goel, R; Terashima, M; Yasui, H



Comparison of Seven Chemical Pretreatments of Corn Straw for Improving Methane Yield by Anaerobic Digestion  

PubMed Central

Agriculture straw is considered a renewable resource that has the potential to contribute greatly to bioenergy supplies. Chemical pretreatment prior to anaerobic digestion can increase the anaerobic digestibility of agriculture straw. The present study investigated the effects of seven chemical pretreatments on the composition and methane yield of corn straw to assess their effectiveness of digestibility. Four acid reagents (H2SO4, HCl, H2O2, and CH3COOH) at concentrations of 1%, 2%, 3%, and 4% (w/w) and three alkaline reagents (NaOH, Ca(OH)2, and NH3·H2O) at concentrations of 4%, 6%, 8%, and 10% (w/w) were used for the pretreatments. All pretreatments were effective in the biodegradation of the lignocellulosic straw structure. The straw, pretreated with 3% H2O2 and 8% Ca(OH)2, acquired the highest methane yield of 216.7 and 206.6 mL CH4 g VS ?1 in the acid and alkaline pretreatments, which are 115.4% and 105.3% greater than the untreated straw. H2O2 and Ca(OH)2 can be considered as the most favorable pretreatment methods for improving the methane yield of straw because of their effectiveness and low cost. PMID:24695485

Song, Zilin; GaiheYang; Liu, Xiaofeng; Yan, Zhiying; Yuan, Yuexiang; Liao, Yinzhang



A sustainable pathway of cellulosic ethanol production integrating anaerobic digestion with biorefining.  


Anaerobic digestion (AD) of animal manure is traditionally classified as a treatment to reduce the environmental impacts of odor, pathogens, and excess nutrients associated with animal manure. This report shows that AD also changes the composition of manure fiber and makes it suitable as a cellulosic feedstock for ethanol production. Anaerobically digested manure fiber (AD fiber) contains less hemicellulose (11%) and more cellulose (32%) than raw manure, and has better enzymatic digestibility than switchgrass. Using the optimal dilute alkaline pretreatment (2% sodium hydroxide, 130 degrees C, and 2 h), enzymatic hydrolysis of 10% (dry basis) pretreated AD fiber produces 51 g/L glucose at a conversion rate of 90%. The ethanol fermentation on the hydrolysate has a 72% ethanol yield. The results indicate that 120 million dry tons of cattle manure available annually in the U.S. can generate 63 million dry tons of AD fiber that can produce more than 1.67 billion gallons of ethanol. Integrating AD with biorefining will make significant contribution to the cellulosic ethanol production. PMID:19998279

Yue, Zhengbo; Teater, Charles; Liu, Yan; Maclellan, James; Liao, Wei



Biochar Produced from Anaerobically Digested Fiber Reduces Phosphorus in Dairy Lagoons  

SciTech Connect

This study evaluated the use of biochar produced from anaerobic digester dairy fiber (ADF) to sequester phosphorus (P) from dairy lagoons. The ADF was collected from a plugged flow digester, air-dried to <8% water content, and pelletized. Biochar was produced by slow pyrolysis in a barrel retort. The potential of biochar to reduce P in the anaerobic digester effluent (ADE) was assessed in small-scale filter systems through which the effluent was circulated. Biochar sequestered an average of 381 mg L?1 P from the ADE, and 4 g L?1 ADF was captured as a coating on the biochar. There was an increase of total (1.9 g kg?1), Olsen (763 mg kg?1), and water-extractable P (914 mg kg?1) bound to the biochar after 15 d of filtration. This accounted for a recovery of 32% of the P in the ADE. The recovered P on the biochar was analyzed using 31P nuclear magnetic resonance for P speciation, which confirmed the recovery of inorganic orthophosphate after liquid extraction of the biochar and the presence of inextractable Ca-P in the solid state. The inorganic phosphate was sequestered on the biochar through physical and weak chemical bonding. Results indicate that biochar could be a beneficial component to P reduction in the dairy system.

Streubel, Jason D.; Collins, Harold P.; Tarara, Julie M.; Cochran, Rebecca L.



A perspective on the prevalence of DNA enteric virus genomes in anaerobic-digested biological wastes.  


The major goal of this study is to gain a perspective on the prevalence of DNA enteric virus genomes in mesophilic anaerobic-digested (MAD) sewage sludge and manure by comparing their quantitative PCR (qPCR) concentrations and removals with traditional fecal indicators (Escherichia coli, enterococci, and Bacteroidetes). In addition, relationships between qPCR and culture measurements of fecal indicators (FIs) were determined. There was no significant difference between the qPCR concentrations of human adenovirus and E. coli/enterococci in MAD sewage sludge; however, the qPCR concentrations of bovine adenovirus were significantly lower than FIs and bovine polyomavirus (BPyV) in MAD manure. The qPCR concentrations of human polyomavirus were slightly lower than E. coli and enterococci (p? ?? 0.05), but no significant difference was observed between the qPCR concentrations of BPyV and FIs. The digestion treatment achieved higher genome removal of bovine DNA enteric viruses than FIs (p ??? 0.05). Significant correlations were observed between qPCR and culture measurements of FIs, but the concentrations and removals of FIs determined by qPCR assays were still significantly different than those determined by culture assays. Overall, we determined that the prevalence of DNA enteric virus genomes in MAD biological wastes was high due to their comparable in qPCR concentrations to FIs, indicating that mesophilic anaerobic digestion treatment alone may not be effective enough to remove DNA viral pathogens in biological wastes. PMID:21931949

Wong, Kelvin; Xagoraraki, Irene



Influence of different natural zeolite concentrations on the anaerobic digestion of piggery waste.  


The effect of different natural zeolite concentrations on the anaerobic digestion of piggery waste was studied. Natural zeolite doses in the range 0.2-10 g/l of wastewater were used in batch experiments, which were carried out at temperatures between 27 degrees C and 30 degrees C. Total chemical oxygen demand (COD), total and volatile solids, ammonia and organic nitrogen, pH, total volatile fatty acids (TVFA), alkalinity (Alk) and accumulative methane production were determined during 30 days of digestion. The anaerobic digestion process was favored by the addition of natural zeolite at doses between 2 and 4 g/l and increasingly inhibited at doses beyond 6 g/l. A first-order kinetic model of COD removal was used to determine the apparent kinetic constants of the process. The kinetic constant values increased with the zeolite amount up to a concentration of 4 g/l. The values of the maximum accumulative methane production (Gm) increased until zeolite concentrations of 2-4 g/l. The addition of zeolite reduced the values of the TVFA/ Alk ratio while increasing the pH values, and these facts could contribute to the process failure at zeolite doses of 10 g/l. PMID:11554599

Milán, Z; Sánchez, E; Weiland, P; Borja, R; Martín, A; Ilangovan, K



Digestion and dewatering characteristics of waste activated sludge treated by an anaerobic biofilm system.  


Immobilization of microorganisms for sludge anaerobic digestion was investigated in this study. The effects of filler properties on anaerobic digestion and dewaterability of waste activated sludge were assessed at mesophilic temperature in batch mode. The results showed that the duration of the methanogenic stage of reactors without filler, with only filler, and with pre-incubated filler was 39days, 19days and 13days, respectively, during which time the protein was degraded by 45.0%, 29.4% and 30.0%, and the corresponding methane yield was 193.9, 107.2 and 108.2mL/g volatile suspended solids added, respectively. On day 39, the final protein degradation efficiency of the three reactors was 45.0%, 40.9% and 42.0%, respectively. The results of normalized capillary suction time and specific resistance to filtration suggested that the reactor incorporating pre-incubated filler could improve the dewaterability of digested sludge, while the effect of the reactor incorporating only filler on sludge dewaterability was uncertain. PMID:24355503

Wang, Tianfeng; Shao, Liming; Li, Tianshui; Lü, Fan; He, Pinjing



Effects of lactone, ketone, and phenolic compounds on methane production and metabolic intermediates during anaerobic digestion.  


Fruit waste is a potential feedstock for biogas production. However, the presence of fruit flavors that have antimicrobial activity is a challenge for biogas production. Lactones, ketones, and phenolic compounds are among the several groups of fruit flavors that are present in many fruits. This work aimed to investigate the effects of two lactones, i.e., ?-hexalactone and ?-decalactone; two ketones, i.e., furaneol and mesifurane; and two phenolic compounds, i.e., quercetin and epicatechin on anaerobic digestion with a focus on methane production, biogas composition, and metabolic intermediates. Anaerobic digestion was performed in a batch glass digester incubated at 55 °C for 30 days. The flavor compounds were added at concentrations of 0.05, 0.5, and 5 g/L. The results show that the addition of ?-decalactone, quercetin, and epicathechin in the range of 0.5-5 g/L reduced the methane production by 50 % (MIC50). Methane content was reduced by 90 % with the addition of 5 g/L of ?-decalactone, quercetin, and epicathechin. Accumulation of acetic acid, together with an increase in carbon dioxide production, was observed. On the contrary, ?-hexalactone, furaneol, and mesifurane increased the methane production by 83-132 % at a concentration of 5 g/L. PMID:25416476

Wikandari, Rachma; Sari, Noor Kartika; A'yun, Qurrotul; Millati, Ria; Cahyanto, Muhammad Nur; Niklasson, Claes; Taherzadeh, Mohammad J



An integrated approach to energy recovery from biomass and waste: Anaerobic digestion-gasification-water treatment.  


The article investigates the performance of an integrated system for the energy recovery from biomass and waste based on anaerobic digestion, gasification and water treatment. In the proposed system, the organic fraction of waste of the digestible biomass is fed into an anaerobic digester, while a part of the combustible fraction of the municipal solid waste is gasified. Thus, the obtained biogas and syngas are used as a fuel for running a cogeneration system based on an internal combustion engine to produce electric and thermal power. The waste water produced by the integrated plant is recovered by means of both forward and inverse osmosis. The different processes, as well as the main components of the system, are modelled by means of a lumped and distributed parameter approach and the main outputs of the integrated plant such as the electric and thermal power and the amount of purified water are calculated. Finally, the implementation of the proposed system is evaluated for urban areas with a different number of inhabitants and the relating performance is estimated in terms of the main outputs of the system. PMID:24946772

Milani, M; Montorsi, L; Stefani, M



Energy recovery from the effluent of plants anaerobically digesting urban solid waste  

NASA Astrophysics Data System (ADS)

The parameters of concentration, time, temperature, and pH to find optimum conditions for enzymatically converting unreacted cellulose in the effluent of an anaerobic digester to glucose for ultimate conversion to methane, and then to project the economics to a 100 tons per day plant was studied. The amount of cellulose hydrolysis for enzyme concentrations from 5 to 1000 CIU/gram of substrate using either filter paper or anaerobically digested municipal solid waste (MSW) reacted over periods of time of from 0 to 72 hours is illustrated. The feasibility of recycling enzymes by ultrafilter capture was studied and it is shown that the recovered enzyme is not denatured by any of several possible enzyme loss mechanisms chemical, physical, or biological. Although rather stable enzyme substrate complexes seem to be formed, various techniques permit a 55% enzyme recovery. Posttreatment of digested MSW by cellulase enzymes produces nearly a threefold increase in biomethanation. The value of the additional methane produced in the process is not sufficient to support the cost of enzymes.



Biomass retention on electrodes rather than electrical current enhances stability in anaerobic digestion.  


Anaerobic digestion (AD) is a well-established technology for energy recovery from organic waste streams. Several studies noted that inserting a bioelectrochemical system (BES) inside an anaerobic digester can increase biogas output, however the mechanism behind this was not explored and primary controls were not executed. Here, we evaluated whether a BES could stabilize AD of molasses. Lab-scale digesters were operated in the presence or absence of electrodes, in open (no applied potential) and closed circuit conditions. In the control reactors without electrodes methane production decreased to 50% of the initial rate, while it remained stable in the reactors with electrodes, indicating a stabilizing effect. After 91 days of operation, the now colonized electrodes were introduced in the failing AD reactors to evaluate their remediating capacity. This resulted in an immediate increase in CH4 production and VFA removal. Although a current was generated in the BES operated in closed circuit, no direct effect of applied potential nor current was observed. A high abundance of Methanosaeta was detected on the electrodes, however irrespective of the applied cell potential. This study demonstrated that, in addition to other studies reporting only an increase in methane production, a BES can also remediate AD systems that exhibited process failure. However, the lack of difference between current driven and open circuit systems indicates that the key impact is through biomass retention, rather than electrochemical interaction with the electrodes. PMID:24576697

De Vrieze, Jo; Gildemyn, Sylvia; Arends, Jan B A; Vanwonterghem, Inka; Verbeken, Kim; Boon, Nico; Verstraete, Willy; Tyson, Gene W; Hennebel, Tom; Rabaey, Korneel



Energy recovery from the effluent of plants anaerobically digesting urban solid waste  

SciTech Connect

The program objective was to study the parameters of concentration, time, temperature, and pH to find optimum conditions for enzymatically converting unreacted cellulose in the effluent of an anaerobic digester to glucose for ultimate conversion to methane, and then to project the economics to a 100-tons-per-day plant. The data presented illustrate the amount of cellulose hydrolysis (in percent solubilized mass) for enzyme concentrations from 5 to 1000 C/sub 1/U/gram of substrate using either filter paper or anaerobically digested municipal solid waste (MSW) reacted over periods of time of from 0 to 72 hours. With an active bacterial culture present, the optimum temperature for the hydrolysis reaction was found to be 40/sup 0/C. The feasibility of recycling enzymes by ultrafilter capture was studied and shows that the recovered enzyme is not denatured by any of several possible enzyme loss mechanisms - chemical, physical, or biological. Although rather stable enzyme-substrate complexes seem to be formed, various techniques permit a 55% enzyme recovery. Posttreatment of digested MSW by cellulase enzymes produces nearly a threefold increase in biomethanation. However, the value of the additional methane produced in the process as studied is not sufficient to support the cost of enzymes. The feasibility of enzymatic hydrolysis as a biomethanation process step requires further process optimization or an entirely different process concept.

Not Available



Evaluation of the anaerobic co-digestion of sewage sludge and tomato waste at mesophilic temperature.  


Sewage sludge is a hazardous waste, which must be managed adequately. Mesophilic anaerobic digestion is a widely employed treatment for sewage sludge involving several disadvantages such as low methane yield, poor biodegradability, and nutrient imbalance. Tomato waste was proposed as an easily biodegradable co-substrate to increase the viability of the process in a centralized system. The mixture proportion of sewage sludge and tomato waste evaluated was 95:5 (wet weight), respectively. The stability was maintained within correct parameters in an organic loading rate from 0.4 to 2.2 kg total volatile solids (VS)/m(3) day. Moreover, the methane yield coefficient was 159 l/kg VS (0 °C, 1 atm), and the studied mixture showed a high anaerobic biodegradability of 95 % (in VS). Although the ammonia concentration increased until 1,864 ± 23 mg/l, no inhibition phenomenon was determined in the stability variables, methane yield, or kinetics parameters studied. PMID:24682875

Belhadj, Siham; Joute, Yassine; El Bari, Hassan; Serrano, Antonio; Gil, Aida; Siles, José A; Chica, Arturo F; Martín, M Angeles



Effects of lipid concentration on anaerobic co-digestion of municipal biomass wastes  

SciTech Connect

Highlights: • Lipid in municipal biomass would not inhibited the anaerobic digestion process. • A lipid concentration of 65% of total VS was the inhibition concentration. • The amount of Brevibacterium decreased with the increasing of the lipid contents. • Long chain fatty acids stacked on the methanogenic bacteria and blocked the mass transfer process. - Abstract: The influence of the lipid concentration on the anaerobic co-digestion of municipal biomass waste and waste-activated sludge was assessed by biochemical methane potential (BMP) tests and by bench-scale tests in a mesophilic semi-continuous stirred tank reactor. The effect of increasing the volatile solid (VS) concentration of lipid from 0% to 75% was investigated. BMP tests showed that lipids in municipal biomass waste could enhance the methane production. The results of bench-scale tests showed that a lipids concentration of 65% of total VS was the inhibition concentration. Methane yields increased with increasing lipid concentration when lipid concentrations were below 60%, but when lipid concentration was set as 65% or higher, methane yields decreased sharply. When lipid concentrations were below 60%, the pH values were in the optimum range for the growth of methanogenic bacteria and the ratios of volatile fatty acid (VFA)/alkalinity were in the range of 0.2–0.6. When lipid concentrations exceeded 65%, the pH values were below 5.2, the reactor was acidized and the values of VFA/alkalinity rose to 2.0. The amount of Brevibacterium decreased with increasing lipid content. Long chain fatty acids stacked on the methanogenic bacteria and blocked the mass transfer process, thereby inhibiting anaerobic digestion.

Sun, Yifei, E-mail: [School of Chemistry and Environment, Beihang University, Beijing 100191 (China); Wang, Dian; Yan, Jiao [School of Chemistry and Environment, Beihang University, Beijing 100191 (China); Qiao, Wei [College of Chemical Science and Engineering, China University of Petroleum, Beijing 102249 (China); Wang, Wei [School of Environment, Tsinghua University, Beijing 100084 (China); Zhu, Tianle [School of Chemistry and Environment, Beihang University, Beijing 100191 (China)



Comparative mesophilic and thermophilic anaerobic digestion of palm oil mill effluent using upflow anaerobic sludge blanket.  


The effects of organic loading rate and operating temperature on the microbial diversity and performances of upflow anaerobic sludge blanket (UASB) reactors treating palm oil mill effluent (POME) were investigated. The following two UASB reactors were run in parallel for comparison: (1) under a mesophilic condition (37 degrees C) and (2) under a mesophilic condition in transition to a thermophilic condition (57 degrees C). A polymerase chain reaction (PCR)-based denaturing gradient gel electrophoresis (DGGE) analysis showed that the microbial population profiles significantly changed with the organic loading rate (OLR) and the temperature transition from the mesophilic to the thermophilic condition. Significant biomass washout was observed for the mesophilic UASB when operating at a high organic loading rate (OLR) of 9.5 g chemical oxygen demand (COD)/L.d. In contrast, the thermophilic UASB can be operated at this OLR and at a temperature of 57 degrees C with satisfactory COD removal and biogas production. The PCR-based DGGE analysis suggested that the thermophilic temperature of 57 degrees C was suitable for a number of hydrolytic, acidogenic, and acetogenic bacteria. PMID:22876480

Khemkhao, Maneerat; Nuntakumjorn, Boonyarit; Techkarnjanaruk, Somkiet; Phalakornkule, Chantaraporn



Treatment of anaerobic digestion effluent of sewage sludge using soilless cultivation  

NASA Astrophysics Data System (ADS)

Soilless cultivation was carried out using anaerobic digestion effluent of sewage sludge as liquid fertilizer, with a preparation which cultures microorganisms in nutrient solution. As a result, ammonium ions contained in the effluent were nitrified into nitrate ions by the microorganisms. And then, Japanese mustard spinach (Brassica rapa var. perviridis) was cultivated by soilless cultivation system. The plants were grown well using microbial nutrient solution, which similar to the plants using conventional inorganic nutrient solution. In contrast, the plants were grown poorly using the effluent as liquid fertilizer without microorganisms.

Uchimura, Koki; Sago, Yuki; Kamahara, Hirotsugu; Atsuta, Yoichi; Daimon, Hiroyuki



Prediction of trace compounds in biogas from anaerobic digestion using the MATLAB Neural Network Toolbox  

Microsoft Academic Search

Abstract The outlook,to apply the highly energetic biogas,from,anaerobic,digestion into fuel cells will result in a significantly higher electrical efficiency and,can contribute,to an increase of renewable,energy,production. The practical bottleneck is the fuel cell poisoning,caused,by several gaseous,trace compounds,like hydrogen,sulfide and,ammonia.,Hence artificial neural networks,were developed,to predict these trace compounds.,The experiments,concluded,that ammonia,in biogas,can indeed,be present up to 93 ppm. Hydrogen,sulfide and ammonia,concentrations,in biogas were

David P. B. T. B. Strik; Alexander M. Domnanovich; Loredana Zani; Rudolf Braun; Peter Holubar



A pilot study of anaerobic membrane digesters for concurrent thickening and digestion of waste activated sludge (WAS).  


The increased interest in biomass energy provides incentive for the development of efficient and high throughput digesters such as anaerobic membrane bioreactors (AnMBRs) to stabilize waste activated sludge (WAS). This paper presents the results of a pilot and short term filtration study that was conducted to assess the performance of AnMBRs when treating WAS at a 15 day hydraulic retention time (HRT) and 30 day sludge retention time (SRT) in comparison to two conventional digesters running at 15 (BSR-15) and 30 days (BSR-30) HRT/SRT. At steady state, the AnMBR digester showed a slightly higher volatile solids (VS) destruction of 48% in comparison to 44% and 35.3% for BSR-30 and BSR-15, respectively. The corresponding values of specific methane production were 0.32, 0.28 and 0.21 m(3) CH(4)/kg of VS fed. Stable membrane operation at an average flux of 40+/-3.6 LM(-2 )H(-1) (LMH) was observed when the digester was fed with a polymer-dosed thickened waste activated sludge (TWAS) and digester total suspended solids (TSS) concentrations were less than 15 gL(-1). Above this solids concentration a flux decline to 24.1+/-2.0 LM(-2) H(-1) was observed. Short term filtration tests conducted using sludge fractions of a 9.7 and 17.1 gL(-1) TSS sludge indicated 84 and 70% decline in filtration performance to be associated with the supernatant fraction of the sludge. At a higher sludge concentration, the introduction of unique fouling control strategy to tubular membranes, a relaxed mode of operation (i.e. 5 minutes permeation and 1 minute relaxation by) significantly increased the flux from 23.8+/-1.1 to 37.8+/-2.3 LMH for a neutral membrane and from 25.7+/-1.1 to 44.9+/-2.9 LMH for a negatively charged membrane. The study clearly indicates that it is technically feasible to employ AnMBRs to achieve a substantial reduction in digester volumes. PMID:20351424

Dagnew, Martha; Parker, Wayne J; Seto, Peter



Anaerobic digestion of acidified slurry fractions derived from different solid-liquid separation methods.  


Batch assays investigating the ultimate methane yields (B(0)) of acidified slurry fractions produced with different solid-liquid slurry separation techniques were done. The result showed that the anaerobic digestion (AD) process was inhibited when raw and liquid fractions of sow, pig and dairy cow acidified slurry are digested, but AD treating solid fractions (SF) acidified slurry showed no sulphide inhibition. The B(0) of SF acidified sow slurry increased significantly with increasing screen size in the screw press. No significant effect of acidification processes on B(0) of SF dairy cow slurry (DCS) was observed. The ultimate methane yields of SF acidified DCS and SF non acidified DCS were 278±13 and 289±1LkgVS(-1), while in term of fresh weigh substrate were 59±2.8 and 59±0.3Lkgsubstrate(-1), respectively. PMID:23313767

Sutaryo, Sutaryo; Ward, Alastair James; Møller, Henrik Bjarne



Improved utilization of fish waste by anaerobic digestion following omega-3 fatty acids extraction.  


Fish waste is a potentially valuable resource from which high-value products can be obtained. Anaerobic digestion of the original fish waste and the fish sludge remaining after enzymatic pre-treatment to extract fish oil and fish protein hydrolysate was evaluated regarding the potential for methane production. The results showed high biodegradability of both fish sludge and fish waste, giving specific methane yields of 742 and 828 m(3)CH(4)/tons VS added, respectively. However, chemical analysis showed high concentrations of light metals which, together with high fat and protein contents, could be inhibitory to methanogenic bacteria. The feasibility of co-digesting the fish sludge with a carbohydrate-rich residue from crop production was thus investigated, and a full-scale process outlined for converting odorous fish waste to useful products. PMID:22784804

Nges, Ivo Achu; Mbatia, Betty; Björnsson, Lovisa



Effects of thermobarical pretreatment of cattle waste as feedstock for anaerobic digestion.  


Lab-scale experiments were conducted to assess the impact of thermobarical treatment of cattle waste on anaerobic digestion. Treatment was at temperatures of 140-220°C in 20K steps for a 5-min duration. Methane yields could be increased by up to 58% at a treatment temperature of 180°C. At 220°C the abundance of inhibitors and other non-digestible substances led to lower methane yields than those obtained from untreated material. In an extended analysis it could be demonstrated that there is a functional correlation between the methane yields after 30 days and the formation rate and methane yield in the acceleration phase. It could be proved in a regression of these correlation values that the optimum treatment temperature is 164°C and that the minimum treatment temperature should be above 115°C. PMID:24238801

Budde, Jörn; Heiermann, Monika; Quiñones, Teresa Suárez; Plöchl, Matthias



Continuous high-solids anaerobic co-digestion of organic solid wastes under mesophilic conditions  

SciTech Connect

Highlights: > High-solids (dry) anaerobic digestion is attracting a lot of attention these days. > One reactor was fed with food waste (FW) and paper waste. > Maximum biogas production rate of 5.0 m{sup 3}/m{sup 3}/d was achieved at HRT 40 d and 40% TS. > The other reactor was fed with FW and livestock waste (LW). > Until a 40% LW content increase, the reactor exhibited a stable performance. - Abstract: With increasing concerns over the limited capacity of landfills, conservation of resources, and reduction of CO{sub 2} emissions, high-solids (dry) anaerobic digestion of organic solid waste (OSW) is attracting a great deal of attention these days. In the present work, two dry anaerobic co-digestion systems fed with different mixtures of OSW were continuously operated under mesophilic conditions. Dewatered sludge cake was used as a main seeding source. In reactor (I), which was fed with food waste (FW) and paper waste (PW), hydraulic retention time (HRT) and solid content were controlled to find the maximum treatability. At a fixed solid content of 30% total solids (TS), stable performance was maintained up to an HRT decrease to 40 d. However, the stable performance was not sustained at 30 d HRT, and hence, HRT was increased to 40 d again. In further operation, instead of decreasing HRT, solid content was increased to 40% TS, which was found to be a better option to increase the treatability. The biogas production rate (BPR), CH{sub 4} production yield (MPY) and VS reduction achieved in this condition were 5.0 m{sup 3}/m{sup 3}/d, 0.25 m{sup 3} CH{sub 4}/g COD{sub added}, and 80%, respectively. Reactor (II) was fed with FW and livestock waste (LW), and LW content was increased during the operation. Until a 40% LW content increase, reactor (II) exhibited a stable performance. A BPR of 1.7 m{sup 3}/m{sup 3}/d, MPY of 0.26 m{sup 3} CH{sub 4}/g COD{sub added}, and VS reduction of 72% was achieved at 40% LW content. However, when the LW content was increased to 60%, there was a significant performance drop, which was attributed to free ammonia inhibition. The performances in these two reactors were comparable to the ones achieved in the conventional wet digestion and thermophilic dry digestion processes.

Kim, Dong-Hoon [Wastes Energy Research Center, Korea Institute of Energy Research, 102, Gajeong-ro, Yuseong-gu, Daejeon 305-343 (Korea, Republic of); Oh, Sae-Eun, E-mail: [Department of Environmental Engineering, Hanbat National University, San 16-1, Duckmyoung-dong, Yuseong-gu, Daejeon (Korea, Republic of)



Anaerobic slurry co-digestion of poultry manure and straw: effect of organic loading and temperature  

PubMed Central

In order to obtain basic design criteria for anaerobic digestion of a mixture of poultry manure and wheat straw, the effects of different temperatures and organic loading rates on the biogas yield and methane contents were evaluated. Since poultry manure is a poor substrate, in term of the availability of the nutrients, external supplementation of carbon has to be regularly performed, in order to achieve a stable and efficient process. The complete-mix, pilot-scale digester with working volume of 70 L was used. The digestion operated at 25°C, 30°C and 35°C with organic loading rates of 1.0, 2.0, 2.5, 3.0, 3.5 and 4.0 kg Volatile solid/m3d and a HRT of 15 days. At a temperature of 35°C, the methane yield was increased by 43% compared to 25°C. Anaerobic co-digestion appeared feasible with a loading rate of 3.0 kg VS/m3d at 35°C. At this state, the specific methane yield was calculated about 0.12 m3/kg VS with a methane content of 53–70.2% in the biogas. The volatile solid (VS) removal was 72%. As a result of volatile fatty acid accumulation and decrease in pH, when the loading rate was less than 1 or greater than 4 kg VS/m3d, the process was inhibited or overloaded, respectively. Both the lower and higher loading rates resulted in a decline in the methane yield. PMID:24502409



A new multiple-stage electrocoagulation process on anaerobic digestion effluent to simultaneously reclaim water and clean up biogas.  


A new multiple-stage treatment process was developed via integrating electrocoagulation with biogas pumping to simultaneously reclaim anaerobic digestion effluent and clean up biogas. The 1st stage of electrocoagulation treatment under the preferred reaction condition led to removal efficiencies of 30%, 81%, 37% and >99.9% for total solids, chemical oxygen demand, total nitrogen and total phosphorus, respectively. Raw biogas was then used as a reactant and pumped into the effluent to simultaneously neutralize pH of the effluent and remove H2S in the biogas. The 2nd stage of electrocoagulation treatment on the neutralized effluent showed that under the selected reaction condition, additional 60% and 10% of turbidity and chemical oxygen demand were further removed. The study concluded a dual-purpose approach for the first time to synergistically combine biogas purification and water reclamation for anaerobic digestion system, which well addresses the downstream challenges of anaerobic digestion technology. PMID:25540943

Liu, Zhiguo; Stromberg, David; Liu, Xuming; Liao, Wei; Liu, Yan



Effect of alkaline addition on anaerobic sludge digestion with combined pretreatment of alkaline and high pressure homogenization.  


To improve anaerobic digestion efficiency, combination pretreatment of alkaline and high pressure homogenization was applied to pretreat sewage sludge. Effect of alkaline dosage on anaerobic sludge digestion was investigated in detail. SCOD of sludge supernatant significantly increased with the alkaline dosage increase after the combined pretreatment because of sludge disintegration. Organics were significantly degraded after the anaerobic digestion, and the maximal SCOD, TCOD and VS removal was 73.5%, 61.3% and 43.5%, respectively. Cumulative biogas production, methane content in biogas and biogas production rate obviously increased with the alkaline dosage increase. Considering both the biogas production and alkaline dosage, the optimal alkaline dosage was selected as 0.04 mol/L. Relationships between biogas production and sludge disintegration showed that the accumulative biogas was mainly enhanced by the sludge disintegration. The methane yield linearly increased with the DDCOD increase as Methane yield (ml/gVS)=4.66 DDCOD-9.69. PMID:24703958

Fang, Wei; Zhang, Panyue; Zhang, Guangming; Jin, Shuguang; Li, Dongyi; Zhang, Meixia; Xu, Xiangzhe



Multiple approaches to characterize the microbial community in a thermophilic anaerobic digester running on swine manure: a case study.  


In this study, the first survey of microbial community in thermophilic anaerobic digester using swine manure as sole feedstock was performed by multiple approaches including denaturing gradient gel electrophoresis (DGGE), clone library and pyrosequencing techniques. The integrated analysis of 21 DGGE bands, 126 clones and 8506 pyrosequencing read sequences revealed that Clostridia from the phylum Firmicutes account for the most dominant Bacteria. In addition, our analysis also identified additional taxa that were missed by the previous researches, including members of the bacterial phyla Synergistetes, Planctomycetes, Armatimonadetes, Chloroflexi and Nitrospira which might also play a role in thermophilic anaerobic digester. Most archaeal 16S rRNA sequences could be assigned to the order Methanobacteriales instead of Methanomicrobiales comparing to previous studies. In addition, this study reported that the member of Methanothermobacter genus was firstly found in thermophilic anaerobic digester. PMID:24629524

Tuan, Nguyen Ngoc; Chang, Yi-Chia; Yu, Chang-Ping; Huang, Shir-Ly



Dry anaerobic co-digestion of cow dung with pig manure for methane production.  


The performance of dry anaerobic digestions of cow dung, pig manure, and their mixtures into different ratios were evaluated at 35?±?1 °C in single-stage batch reactors for 63 days. The specific methane yields were 0.33, 0.37, 0.40, 0.38, 0.36, and 0.35 LCH4/gVSr for cow dung to pig manure ratios of 1:0, 4:1, 3:2, 2:3, 1:4, and 0:1, respectively, while volatile solid (VS) and chemical oxygen demand (COD) removal efficiencies were 48.59, 50.79, 53.20, 47.73, 46.10, and 44.88 % and 55.44, 57.96, 60.32, 56.96, 53.32, and 50.86 %, respectively. The experimental results demonstrated that the co-digestions resulted in 5.10-18.01 % higher methane yields, 2.03-12.95 % greater VS removals, 2.98-12.52 % greater COD degradation and so had positive synergism. The various mixtures of pig manure with cow dung might persuade a better nutrient balance and dilution of high ammonia concentration in pig manure and therefore enhanced digester performance efficiency and higher biogas yields. The dry co-digestion of 60 % cow dung and 40 % pig manure achieved the highest methane yield and the greatest organic materials removal efficiency than other mixtures and controls. PMID:24818871

Li, Jianzheng; Jha, Ajay Kumar; Bajracharya, Tri Ratna



Effect of different pH-values on process parameters in two-phase anaerobic digestion of high-solid substrates.  


In many publications, primary fermentation is described as a limiting step in the anaerobic digestion of fibre-rich biomass [Eastman JA, Ferguson JF. Solubilization of particulacte carbon during the anaerobic digeston. J WPCF. 1981;53:352-366; Noike T, Endo G, Chang J, Yaguchi J, Matsumoto J. Characteristics of carbohydrate degradation and the rate-limiting step in anaerobic digestion. Biotechnol Bioeng. 1985;27:1482-1489; Arntz HJ, Stoppok E, Buchholz K. Anaerobic hydroysis of beet pulp-discontiniuous experiments. Biotechnol Lett. 1985;7:113-118]. The microorganisms of the primary fermentation process differ widely from the methanogenic microorganisms [Pohland FG, Ghosh S. Developments in anaerobic stabilization of organic wastes-the two-phase concept. Environ Lett. 1971;1:255-266]. To optimize the biogas process, a separation in two phases is suggested by many authors [Fox P, Pohland GK. Anaerobic treatment applications and fundamentals: substrate specificity during phase separation. Water Environ Res. 1994;66:716-724; Cohen A, Zoetemeyer RJ, van Deursen A, van Andel JG. Anaerobic digestion of glucose with separated acid production and methane formation. Water Res. 1979;13:571-580]. To carry out the examination, a two-phase laboratory-scale biogas plant was established, with a physical phase separation. In previous studies, the regulation of the pH-value during the acid formation was usually carried out by the addition of sodium hydroxide [Cohen A, Zoetemeyer RJ, van Deursen A, van Andel JG. Anaerobic digestion of glucose with separated acid production and methane formation. Water Res. 1979;13:571-580; Ueno Y, Tatara M, Fukui H, Makiuchi T, Goto M, Sode K. Production of hydrogen and methane from organic solid wastes by phase separation of anaerobic process. Bioresour Technol. 2007;98:1861-1865; Zoetemeyer RJ, van den Heuvel JC, Cohen A. pH influence on acidogenic dissimilation of glucose in an anaerobic digestor. Water Res. 1982;16:303-311]. A new technology without the use of additives was developed in which the pH-regulation is executed by the pH-dependent recycling of effluent from the anaerobic filter into the acidification reactor. During this investigation, the influence of the different target pH-values (5.5, 6.0, 7.0 and 7.5) on the degradation rate, the gas composition and the methane yield of the substrate maize silage was determined. With an increase in the target pH-value from 5.5 to 7.5, the acetic acid equivalent decreased by 88.1% and the chemical oxygen demand-concentration by 18.3% in the hydrolysate. In response, there was a 58% increase in the specific methane yield of the overall system. Contrary to earlier studies, a marked increase in biogas production and in substrate degradation was determined with increasing pH-values. However, these led to a successive approximation of a single-phase process. Based on these results, pH-values above 7.0 seem to be favourable for the digestion of fibre-rich substrates. PMID:25413114

Lindner, Jonas; Zielonka, Simon; Oechsner, Hans; Lemmer, Andreas



Effects of different SRT on anaerobic digestion of MSW dosed with various MSWI ashes.  


This study investigated different solid retention time (SRT) on municipal solid waste (MSW) anaerobic digestion with various MSW incinerator fly ash (FA) and bottom ash (BA) addition. Results showed that biogas production rates (BPRs, ? 200 to ? 400 mL/gVS) with organic loading rate of ? 0.053 gVS/gVS(reactor) (Day 1-435, SRT 20 days, SRT20) at FA 1g/d (FA1), BA 12 g/d (BA12) and BA 24 g/d (BA24) dosed bioreactors increased after adaptation. BPRs with SRT10 and SRT5 decreased while BPRs with SRT40 showed to increase compared to initial BPRs (? 200 mL/gVS) with SRT20. SRT5 operation reduced the BPRs (? 10 - ? 90 mL/gVS) significantly and only BA12 and BA24 dosed bioreactors could recover the BPRs (? 100 - ? 200 mL/gVS) after SRT20 operation (Day 613-617) compared to FA1 and FA3 and control. Released levels of Co, Mo and W at BA12 and BA24 dosed bioreactors showed most potential to improve MSW anaerobic digestion. PMID:23026339

Lo, H M; Chiu, H Y; Lo, S W; Lo, F C



Continuous mesophilic anaerobic digestion of manure and rape oilcake - Experimental and modelling study.  


Rape oilcake is a by-product formed after the removal of oil from rapeseed. Due to the high content of organic matter rape oilcake seems a good substrate for anaerobic digestion when it cannot be used as fodder. The aim of this work was to optimise the parameters used in a mathematical model of anaerobic digestion for rapeseed oilcake and cattle manure. The composition of these substrates was determined in order to estimate model inputs. Optimised kinetic constants of hydrolysis and decomposition for oilcake (Kdis=0.77, KhydCH=0.55, khydPr=0.57, khydLi=0.30) were estimated based on batch fermentation. The accuracy of the model with improved input parameters was confirmed by continuous fermentation. The average concentration of methane in biogas was about 50%. The biogas production efficiency from organic matter (defined as volatile solids) was 0.42m(3)kg(-1) with an organic substrate loading rate equal to 3.18 kgm(-3)d(-1). The fermentation process demonstrated good stability and efficiency. The accuracy of the optimised model seems sufficient for use in modelling of a full scale process. PMID:25318701

Jab?o?ski, S?awomir J; Biernacki, Piotr; Steinigeweg, Sven; ?ukaszewicz, Marcin



Deterministic processes guide long-term synchronised population dynamics in replicate anaerobic digesters.  


A replicate long-term experiment was conducted using anaerobic digestion (AD) as a model process to determine the relative role of niche and neutral theory on microbial community assembly, and to link community dynamics to system performance. AD is performed by a complex network of microorganisms and process stability relies entirely on the synergistic interactions between populations belonging to different functional guilds. In this study, three independent replicate anaerobic digesters were seeded with the same diverse inoculum, supplied with a model substrate, ?-cellulose, and operated for 362 days at a 10-day hydraulic residence time under mesophilic conditions. Selective pressure imposed by the operational conditions and model substrate caused large reproducible changes in community composition including an overall decrease in richness in the first month of operation, followed by synchronised population dynamics that correlated with changes in reactor performance. This included the synchronised emergence and decline of distinct Ruminococcus phylotypes at day 148, and emergence of a Clostridium and Methanosaeta phylotype at day 178, when performance became stable in all reactors. These data suggest that many dynamic functional niches are predictably filled by phylogenetically coherent populations over long time scales. Neutral theory would predict that a complex community with a high degree of recognised functional redundancy would lead to stochastic changes in populations and community divergence over time. We conclude that deterministic processes may play a larger role in microbial community dynamics than currently appreciated, and under controlled conditions it may be possible to reliably predict community structural and functional changes over time. PMID:24739627

Vanwonterghem, Inka; Jensen, Paul D; Dennis, Paul G; Hugenholtz, Philip; Rabaey, Korneel; Tyson, Gene W



Promoting anaerobic biogasification of corn stover through biological pretreatment by liquid fraction of digestate (LFD).  


A new biological pretreatment method by using liquid fraction of digestate (LFD) was advanced for promoting anaerobic biogasification efficiency of corn stover. 17.6% TS content and ambient temperature was appropriate for pretreatment. The results showed that C/N ratio decreased to about 30, while total lignin, cellulose, and hemicellulose (LCH) contents were reduced by 8.1-19.4% after pretreatment. 3-days pretreatment was considered to be optimal, resulting in 70.4% more biogas production, 66.3% more biomethane yield and 41.7% shorter technical digestion time compared with the untreated stover. The reductions on VS, cellulose, and hemicellulose were increased by 22.1-35.9%, 22.3-35.4%, and 19.8-27.2% for LFD-treated stovers. The promoted anaerobic biogasification efficiency was mainly attributed to the improved biodegradability due to the pre-decomposition role of the bacteria in LFD. The method proved to be an efficient and low cost approach for producing bioenergy from corn stover, meanwhile, reducing LFD discharge and minimizing its potential pollution. PMID:25459818

Hu, Yun; Pang, Yunzhi; Yuan, Hairong; Zou, Dexun; Liu, Yanping; Zhu, Baoning; Chufo, Wachemo Akiber; Jaffar, Muhammad; Li, Xiujin



Comparative performance of mesophilic and thermophilic anaerobic digestion for high-solid sewage sludge.  


In local cities, many small sewage and waste treatment facilities are operated independently. To encourage processing by anaerobic digestion at a centralized sewage treatment plant (STP), high-solid sewage sludge is helpful because it reduces the energy and cost required for transporting the sludge from other STPs. Mesophilic and thermophilic anaerobic digestion of sewage sludge at total solids concentrations (TS) of 7.5% and 10% were evaluated using laboratory-scale continuous reactors. Under the mesophilic condition, sewage sludge of 10% TS was successfully treated. Under the thermophilic condition, sewage sludge of 7.5% TS was not successfully treated when the total ammonia concentration was over 2000 mg N/L. Batch experiments showed that it takes a few weeks for the methane fermentation activity to recover after being inhibited. The effectiveness of adding easily biodegradable organic matter was confirmed. These results show that high-solid sewage sludge is suitable for small facilities by controlling the operating conditions. PMID:24096284

Hidaka, Taira; Wang, Feng; Togari, Taketo; Uchida, Tsutomu; Suzuki, Yutaka



Effect of different livestock dungs as inoculum on food waste anaerobic digestion and its kinetics.  


The aim of this study was to evaluate the effect of different livestock inoculums on the anaerobic digestion of food waste (FW). Five different livestock dungs i.e., poultry dung (PD), goat dung (GD), cow dung (CD), piggery dung (PGD) and rhinoceros dung (RD) were utilized as inoculums and their effects were valued in various food to microorganism (F/M) ratios in batch reactors. Different livestock dungs achieved higher methane production and volatile solids (VS) reduction in different F/M ratios such as PD, GD, CD, PGD and RD achieved at F/M ratio maintained at 1.5, 2, 2, 1.5 and 1.5, respectively. The results indicated that CD and PGD inoculum were more suitable for the anaerobic digestion of FW than other livestock dungs. Reactors inoculated with CD achieved higher methane production (227mLg(-1)VS degraded) and volatile solids degradation (54.58%) at F/M ratio maintained at 2. PMID:25616237

Dhamodharan, Kondusamy; Kumar, Vikas; Kalamdhad, Ajay S



A critical review on inhibition of anaerobic digestion process by excess ammonia.  


Ammonia plays a vital role in the performance and stability of anaerobic digestion (AD) of N-rich organic-feedstock. Several research works were carried-out to study the effect of ammonia on the efficiency of AD of agro-food, industrial and livestock wastes/wastewater. However, excess ammonia remains a critical hitch in AD process. The mechanism of ammonia-inhibition has also been studied and there is no simple strategy available to mitigate ammonia-toxicity, when it exceeds threshold inhibition-level. For successful operation of AD systems at higher ammonia-level, adequate choice of temperature, control of pH and C/N ratio, and utilization of acclimatized-microflora to higher ammonia concentrations may ensure a stable and undisturbed digestion. This review provides a critical summary of earlier and recent research conducted on ammonia-inhibition during the anaerobic degradation of organic substrates, especially, at high ammonia concentrations. This article emphasizes that more profound knowledge on parameters influencing ammonia-inhibition is needed to apply appropriate control strategies. PMID:23835276

Rajagopal, Rajinikanth; Massé, Daniel I; Singh, Gursharan



Utilisation of wastewater nutrients for microalgae growth for anaerobic co-digestion.  


The feasibility of growing microalgae in natural light using wastewater high in nutrients (N & P) for the production of more bioenergy was examined. The main retrofitting unit would be a photobioreactor for wastewater treatment plants (wwtp) having anaerobic digesters in close proximity. Theoretical microalgae production rates from different wastewater sources (municipal wwtp, source separation of human and animal wastewaters) were estimated using mass balance. Mass and energy balances for a conventional wwtp using chemically enhanced primary treatment was investigated for microalgae growth for a situation limited by availability of carbon dioxide (CO2) generated onsite and where additional CO2 was imported from outside source. Reject water from dewatering of anaerobically digested sludge from four wwtp around Oslo region were pretreated for improved light penetration and examined for microalgae growth. Several pre-treatment methods were investigated. Pretreatment using flocculation + settling + anthracite filtration yielded high light transmittance. A maximum microalgae growth rate of 13 g TSS/m(2)-d was achieved using this pretreated reject water. The challenges of integrating photobioreactors with existing units have been highlighted. PMID:23570973

Sahu, Ashish K; Siljudalen, Jon; Trydal, Tina; Rusten, Bjørn



Coupling of the hydrogen and polyhydroxyalkanoates (PHA) production through anaerobic digestion from Taihu blue algae.  


Coupling bio-production of hydrogen and polyhydroxyalkanoates (PHA) from Taihu blue algae through metabolites circulation was investigated. It was found that the pH adjustment, especially basification was more practical and efficient than other methods for the pretreatment of blue algae before anaerobic digestion. On this occasion, SCOD, biogas accumulation and hydrogen content reached 26 mg/gTS, 500 mL and 37.2%, and which were 4.3, 1.3 and 14.4 times of those of the control group, respectively. Secondly, amounts of both butyric acid and hydrogen could be further increased when blue algae was alkali pretreated at pH 13, as the accumulation of butyric acid, acetic acid and hydrogen reached 1.7, 1.4 and 3.8 times compared to those of the control, respectively. Finally, the coupling bio-production of hydrogen and PHA was conducted through pumping organic residues into PHA fermenter from anaerobic digester. Remarkably, it was found that the larger the pumping rate of carbon and nitrogen sources supply, the higher the yield of DCW and PHA could be expected by Bacillus cereus. PMID:20153165

Yan, Qun; Zhao, Minxing; Miao, Hengfeng; Ruan, Wenquan; Song, Rentao



Effect of limited air exposure and comparative performance between thermophilic and mesophilic solid-state anaerobic digestion of switchgrass.  


Switchgrass is an attractive feedstock for biogas production via anaerobic digestion (AD). Many studies have used switchgrass for liquid anaerobic digestion (L-AD), but few have used switchgrass for solid-state anaerobic digestion (SS-AD). Limited air exposure to the reactor headspace has been adopted in commercial scale anaerobic digesters for different applications. However, little research has examined the effect of limited air exposure on biogas production during SS-AD. In this study, the effects of air exposure and total solids (TS) content on SS-AD performance were evaluated under mesophilic (36±1°C) and thermophilic (55±0.3°C) conditions. Limited air exposure did not significantly influence the methane yield during SS-AD. Thermophilic SS-AD had greater methane yields (102-145LCH4kg(-1)VSadded) than mesophilic SS-AD (88-113LCH4kg(-1)VSadded). Both mesophilic SS-AD (73-136GJ) and thermophilic SS-AD (2-95GJ) produced positive net energy based on a theoretical 'garage-type' SS-AD digester operating in a temperate climate. PMID:25618499

Sheets, Johnathon P; Ge, Xumeng; Li, Yebo



Lignocellulolytic enzyme activity, substrate utilization, and mushroom yield by Pleurotus ostreatus cultivated on substrate containing anaerobic digester solids.  


Solid waste from anaerobic digestion of litter from the commercial production of broiler chickens has limited use as fertilizer. Its disposal is a major problem for digester operators who are seeking alternative use for anaerobic digester solids, also referred to as solid waste (SW). The use of SW as substrates for the cultivation of Pleurotus ostreatus strain MBFBL400 was investigated. Lignocellulolytic enzymes activity, substrate utilization, and mushroom yield were evaluated in ten different substrate combinations (SCs) containing varying amounts of solid waste, wheat straw, and millet. Nutritional content of mushrooms produced on the different substrates was also determined. Substrates containing 70-80% wheat straw, 10-20% SW, and 10-20% millet were found to produce the highest mushroom yield (874.8-958.3 g/kg). Loss of organic matter in all SCs tested varied from 45.8% to 56.2%, which had positive correlation with the biological efficiency. Laccase, peroxidase, and carboxymethylcellulase (CMCase) activities were higher before fruiting, whereas xylanase showed higher activities after mushroom fruiting. SW increased the nutritional content in mushrooms harvested, and the combination of wheat straw and SW with millet significantly improved mushroom yield. Our findings demonstrated the possibility of utilizing anaerobic digester solids in mushroom cultivation. The application of SW as such could improve the financial gains in the overall economy of anaerobic digester plants. PMID:19618225

Isikhuemhen, Omoanghe S; Mikiashvilli, Nona A



Microbial trophic interactions and mcrA gene expression in monitoring of anaerobic digesters  

PubMed Central

Anaerobic digestion (AD) is a biological process where different trophic groups of microorganisms break down biodegradable organic materials in the absence of oxygen. A wide range of AD technologies is being used to convert livestock manure, municipal and industrial wastewaters, and solid organic wastes into biogas. AD gains importance not only because of its relevance in waste treatment but also because of the recovery of carbon in the form of methane, which is a renewable energy and is used to generate electricity and heat. Despite the advances on the engineering and design of new bioreactors for AD, the microbiology component always poses challenges. Microbiology of AD processes is complicated as the efficiency of the process depends on the interactions of various trophic groups involved. Due to the complex interdependence of microbial activities for the functionality of the anaerobic bioreactors, the genetic expression of mcrA, which encodes a key enzyme in methane formation, is proposed as a parameter to monitor the process performance in real time. This review evaluates the current knowledge on microbial groups, their interactions, and their relationship to the performance of anaerobic biodigesters with a focus on using mcrA gene expression as a tool to monitor the process. PMID:25429286

Alvarado, Alejandra; Montañez-Hernández, Lilia E.; Palacio-Molina, Sandra L.; Oropeza-Navarro, Ricardo; Luévanos-Escareño, Miriam P.; Balagurusamy, Nagamani



Anaerobic digestion as a core technology in sustainable management of organic matter.  


In the past decades, anaerobic digestion (AD) has steadily gained importance. However, the technology is not regarded as a top priority in science policy and in industrial development at present. In order for AD to further develop, it is crucial that AD profits from the current fuel issues emerging in the international arena. AD can provide low-cost treatment of sewage and solid domestic wastes, which represents a vast application potential that should be promoted in the developing world. Furthermore, the developments in the last decades in the domain of anaerobic microbiology and technology have generated some interesting niches for the application of AD, such as anaerobic nitrogen removal and the treatment of ch