Showing papers on "Biogas published in 1998"
TL;DR: 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 as discussed by the authors.
1,120 citations
TL;DR: An aggressive start-up strategy was used to initiate codigestion in two anaerobic, continuously mixed bench-top reactors at mesophilic and thermophilic conditions and large fluctuations were observed in methanogenic population levels as volatile fatty acids accumulated and were subsequently consumed.
Abstract: An aggressive start-up strategy was used to initiate codigestion in two anaerobic, continuously mixed bench-top reactors at mesophilic (37 degrees C) and thermophilic (55 degrees C) conditions. The digesters were inoculated with mesophilic anaerobic sewage sludge and cattle manure and were fed a mixture of simulated municipal solid waste and biosolids in proportions that reflect U.S. production rates. The design organic loading rate was 3.1 kg volatile solids/m3/day and the retention time was 20 days. Ribosomal RNA-targeted oligonucleotide probes were used to determine the methanogenic community structure in the inocula and the digesters. Chemical analyses were performed to evaluate digester performance. The aggressive start-up strategy was successful for the thermophilic reactor, despite the use of a mesophilic inoculum. After a short start-up period (20 days), stable performance was observed with high gas production rates (1.52 m3/m3/day), high levels of methane in the biogas (59%), and substantial volatile solids (54%) and cellulose (58%) removals. In contrast, the mesophilic digester did not respond favorably to the start-up method. The concentrations of volatile fatty acids increased dramatically and pH control was difficult. After several weeks of operation, the mesophilic digester became more stable, but propionate levels remained very high. Methanogenic population dynamics correlated well with performance measures. Large fluctuations were observed in methanogenic population levels during the start-up period as volatile fatty acids accumulated and were subsequently consumed. Methanosaeta species were the most abundant methanogens in the inoculum, but their levels decreased rapidly as acetate built up. The increase in acetate levels was paralleled by an increase in Methanosarcina species abundance (up to 11.6 and 4.8% of total ribosomal RNA consisted of Methanosarcina species ribosomal RNA in mesophilic and thermophilic digesters, respectively). Methanobacteriaceae were the most abundant hydrogenotrophic methanogens in both digesters, but their levels were higher in the thermophilic digester.
392 citations
01 Jan 1998
TL;DR: In this paper, several treatment methods were tested and the best results showed an approximately 20% increase of the biogas potential with fibers smaller than 0.35 mm as measured by batch experiments and an increase was approximately 16% with fibers of size 2 mm.
Abstract: The biogas potential of manure could be significantly increased by treatment of the recalcitrant organic matter (biofibers) contained in the manure. Several treatment methods were tested. Mechanical maceration resulted in an average increase of the biogas potential of approximately 17% as shown by the continuous stirred reactor experiment. In general the smaller the fibers the higher the biogas potential was. The best results showed an approximately 20% increase of the biogas potential with fibers smaller than 0.35 mm as measured by batch experiments. The increase was approximately 16% with fibers of size 2 mm. Chemical treatment of the fibers with bases such as NaOH, NH4OH or a combination of bases also resulted in an increased methane potential. However, combination of maceration and chemical treatment did not result in a further increase of the methane potential. There was not any significant difference of the biogas potential from fibers in the range 5-20 mm. Treatment of the fibers with hemicellulolytic or cellulolytic enzymes did not result in any significant increase of the methane potential. However, biological treatment of the fibers of the manure with the hemicellulose degrading bacterium B4 resulted in a significant increase of the biogas potential of manure. An increase of approximately 30% in methane potential was achieved compared to controls.
258 citations
TL;DR: In this paper, a variable compression ratio Ricardo E6 single-cylinder spark-ignition engine operating on simulated biogas formed from different mixtures of domestic natural gas and carbon dioxide was tested.
231 citations
TL;DR: In this article, a two-cylinder, indirect-injection diesel engine of stationary type is used as the first experimental test bed in this work and the variation of quality is provided by mixing natural gas and carbon dioxide.
162 citations
TL;DR: In this article, a new solid-waste treatment process was applied to different vegetable substrates: potato peelings, green salad leaves, green peas mixed with carrots, apple pomace.
128 citations
TL;DR: The simulative results indicate that the leachate recycle for the LFBR resulted in a more rapid methane production from the consumption of the carbohydrate but in less rapid production from that of the protein and lipid.
Abstract: A mathematical model for the development of methane production from a landfill bioreactor (LFBR) treating the organic fraction of municipal solid wastes was developed from the Gompertz equation. The model incorporates three biokinetic parameters: methane production lag phase time, rate, and potential. The methane converting capacity test experiment was conducted to monitor the specific methane production rate consuming anaerobic fermentative intermediates, including carbohydrates, proteins, and lipids. The model developed in this study can be used to predict methane production based on the chemical nature and the decomposition characteristics of the organic fraction of municipal solid wastes. The simulative results indicate that the leachate recycle for the LFBR resulted in a more rapid methane production from the consumption of the carbohydrate but in less rapid production from that of the protein and lipid. Moreover, the same specific methane production rate of 2.6 mL/g volatile solid (VS) per day occurred at the LFBR with/without leachate recycle; however, a sharp drop in methane production lag phase time, from 125 to 25 days, was obtained at the LFBR incubated with leachate recycle.
120 citations
TL;DR: In this paper, it was demonstrated that biogas could provide power equivalent to hydrogen, even when the methane content was reduced below the value at which normal combustion could occur, but carbon deposition was a problem.
117 citations
TL;DR: A two-stage rumen-derived anaerobic digestion process was tested for the conversion of water hyacinth shoots and a mixture of the shoots with cowdung into biogas, and 100% conversion efficiency of the VFA intoBiogas with a methane content of 80% was achieved.
Abstract: A two-stage rumen-derived anaerobic digestion process was tested for the conversion of water hyacinth shoots and a mixture of the shoots with cowdung (7:3) into biogas. Under conditions similar to those of the rumen and loading rates (LR) in the range of 11.6–19.3g volatile solids (VS) l−1d−1 in the rumen reactor, the degradation efficiencies were 38% for the shoots and 43% for the mixture. The major fermentation products were volatile fatty acids (VFA) with a maximum yield of 7.92mmolg−1 VS digested, and biogas with a yield of 0.2lg−1 VS digested. The effect of varying LR, solid retention time (SRT) and dilution rates on the extent of degradation of the water hyacinth–cowdung mixture was examined. Overall conversion of the substrate was highest at the loading rate of 15.4gVS.l−1d−1. Varying the retention times between 60 and 120h had no effect on the degradation efficiency, but a decrease was observed at retention times below 60h. The overall performance of the reactor was depressed by changing the dilution rate from 0.5 to 0.34h−1. By applying a LR of 15.4VS. l−1d−1, a SRT of 90h and a dilution rate of 0.5h−1 in the rumen reactor, and connecting it to a methanogenic reactor of the upflow anaerobic sludge blanket type, 100% conversion efficiency of the VFA into biogas with a methane content of 80% was achieved. The average methane gas yield was 0.44lg−1 VS digested.
87 citations
Patent•
20 Feb 1998
TL;DR: In this article, a method and plant for the treatment of an organic waste material in liquid form, e.g. liquid manure from livestock, is described, which is the method comprising filtering fibres and particles from the liquid, subjecting the liquid to anaerobic fermentation in a biogas reactor, separating a substantially sterile and particle-free permeate stream from the Biogas Reactor, i.e., using ultra-filtration, subjected the permeate streams to treatment with an ammonia stripper at an elevated temperature and preferably at reduced pressure to remove
Abstract: A method and plant for the treatment of an organic waste material in liquid form, e.g. liquid manure from livestock, the method comprising filtering fibres and particles from the liquid, subjecting the liquid to anaerobic fermentation in a biogas reactor, separating a substantially sterile and particle-free permeate stream from the biogas reactor, e.g. using ultrafiltration, subjecting the permeate stream to treatment with an ammonia stripper at an elevated temperature and preferably at reduced pressure to remove substantially all ammonia and carbon dioxide and to result in an ammonia fraction and a nutrient salt fraction, and separating the nutrient salt fraction into a fertiliser concentrate fraction and a water fraction, e.g. using reverse osmosis. The end products of the method are clean water, ammonia concentrate, fertiliser concentrate containing salts of P and K, compost and high-quality biogas with a high methane content.
79 citations
TL;DR: In this paper, the Gompertz equation was used to describe the growth data of the bacterial population in a landfill bioreactor, and the specific methanogenic activity (SMA) on degrading butyrate, propionate, acetate and formate.
TL;DR: In this paper, a laboratory-scale anaerobic reactor, in which the bottom two-thirds were occupied by a sludge blanket and the upper one-third by submerged small cubes of polyurethane foam, was evaluated for the treatment of slaughterhouse wastewater.
TL;DR: Empirical models were developed based on alkaline dose, feed total solids concentration and particle size for biogas production and removal of TS and VS and all three experimental factors were found to be significant with respect to the response variables studied.
TL;DR: In this paper, a bench-scale membrane pilot plant for upgrading biogas generated at a municipal wastewater treatment plant was constructed and operated for extended periods of time, with two identical hollow-fiber modules for periods of over 1000h (41 days) with each module.
TL;DR: Methanogenic cultures were acclimatized to operate at low pHs and the efficiency of methane production at pH 5.0, 4.5 and 4.0 was 67, 37 and 34% respectively, compared to biomethanation at pH 7.0 (100% yield) with 55–65% methane in the biogas composition.
Abstract: Methanogenic cultures were acclimatized to operate at low pHs and the efficiency of methane production at pH 5.0, 4.5 and 4.0 was 67, 37 and 34% respectively, compared to biomethanation at pH 7.0 (100% yield) with 55–65% methane in the biogas composition. Above pH 5.0, the efficiency of methane production was more than 75%. The data for most of the experiments are based on the observations carried out for more than 60 and 100 days. The control experiments of direct pH shock of 4.5 and 4.0 did not show any gas production and even at pH 5.5 production of methane was marginal.
TL;DR: In this paper, a plug-flow digestor was proposed to circumvent the problems associated with floating of biomass feedstocks and enable a semi-continuous operation of biogas plants using mixed green leaf biomass feedstock.
Abstract: The low, family level availability of animal dung in rural Indian families restricts the spread of biogas technology This has warranted the design and development of novel biogas plants for other biomass feedstocks The plug-flow digestors discussed in this paper circumvent the problems associated with floating of biomass feedstocks and enable a semi-continuous operation The long term operation of such biogas plants using a mixed green leaf biomass feedstock is reported along with its design features Results show that during long term operation, such biogas plants have the ability to produce up to $05 \hspace{2mm} m^3\hspace{2mm} gas/m^3$ reactor/day (ambient conditions) at specific conversion rates ranging between 180 and 360 1 biogas/kg TS (total solids) at a 35 day retention time
Journal Article•
TL;DR: Two phase anaerobic digestion of artificially prepared MSW was carried out by coupling a solid-phase acidogenic system with an upflow fixed film reactor and also a suspended growth methanogenic reactor separately to accelerate the bioleachate formation.
Abstract: Two phase anaerobic digestion of artificially prepared MSW was carried out by coupling a solid-phase acidogenic system with an upflow fixed film reactor and also a suspended growth methanogenic reactor separately. The specially developed acidogenic culture was added to solid-bed and recycled back to the same to accelerate the bioleachate formation. A part of the Volatile Fatty Acids (VFA) bearing leachate from the acidogenic reactor was fed to the methanogenic reactor for methane production. Maximum cumulative VFA production was observed after 40 days of fermentation which corresponds to 73.45% of volatile solids reduction of MSW. However, maximum VFA concentration was about 11100 mg/l as acetic acid. The performance of free cell reactor was compared with that of fixed film for the biomethanation of VFA. Fixed film reactor was found superior with respect to both BOD reduction and rate of gas production. In the fixed film reactor, 88.3% of BOD removal was observed at a loading rate of 1.48 Kg.BOD/cu.m-day.
TL;DR: In this article, various steps involving hydrogen production from biogas, its storage and transportation, and its marketing as a commodity have been reviewed, and design and cost relationships have been developed for feasible alternatives.
TL;DR: In this article, the effects of landfill inputs on hydrogen sulfide production and competition between methane production and sulfate reduction during refuse decomposition were evaluated in four-liter reactors that contained residential municipal waste; decomposed refuse as a seed; and various mixtures of anaerobically digested polymer-treated sludge, anaerobic digested lime-stabilized sludge and wallboard (calcium sulfate) simulating construction and demolition waste.
Abstract: The objective of this research was to evaluate the effects of a number of landfill inputs on hydrogen sulfide production and on competition between methane production and sulfate reduction during refuse decomposition. Tests were conducted in four-liter reactors that contained residential municipal waste; decomposed refuse as a seed; and various mixtures of anaerobically digested polymer-treated sludge, anaerobically digested lime-stabilized sludge, and wallboard (calcium sulfate) simulating construction and demolition waste. Tests demonstrated that wallboard was the major cause of hydrogen sulfide production and that methanogenesis and sulfate reduction occur concurrently during refuse decomposition. Additionally, both polymer- and lime-treated sludge enhanced refuse decomposition. Despite the presence of excess sulfate, 2.9 to 7.0 times more organic carbon was biodegraded through methanogenesis than through sulfate reduction.
Journal Article•
TL;DR: In this paper, domestic waste water from the city of A Coruna (NW Spain) was treated anaerobically in a laboratory-scale upflow anaerobic sludge blanket (UASB) digester, at 20°C, at hydraulic retention times (HRTs) of longer than 24 h, the COD and SS removal efficiencies remained practically constant and higher than 85%.
Abstract: Domestic waste water from the city of A Coruna (NW Spain) was treated anaerobically in a laboratory-scale upflow anaerobic sludge blanket (UASB) digester, at 20°C, at hydraulic retention times (HRTs) of longer than 24 h, the COD and SS removal efficiencies remained practically constant and higher than 85%. When reducing the HRT from 24 to 5 h, the COD removal decreased from 85% to 53% and the SS removal from 89% to 63%. The methane recovered in the biogas ranged from 25% to 30% of the influent COD, increasing slightly with the operational time. Methanogenic activities greater than 0.1 g CH 4-COD·g -1 VSS·d -1 were found for the sludge from the lower part of the UASB digester. The average methanogenic activity of the sludge decreased from 0.32 at the start-up to about 0.03 g CH4-COD·g -1 VSS·d -1 at the end of operation, while the average sludge concentration was in the range of 8 to 10 g VSS· l -1 . The amount and the methanogenic activity of the developed anaerobic sludge appeared to be the main efficiency-limiting factor of th e UASB performance. The removal efficiencies were increased by about 5% when the UASB digester was used in combination with a completely mixed sludge digester (CMSD) system for the external digestion and stabilisation of the accumulated solids into the UASB. This also led to the increase of the biomass concentration and uniformisation of the UASB sludge bed, but the average methanogenic activity remained low.
TL;DR: An experimental small scale partial recirculating system for rainbow trout was assembled and the anaerobic digester was able to significantly reduce VS and SS content of wastewater and the zeolite ion-exchange column significantly improved water quality of effluent produced by the digester.
TL;DR: A 3 m3 fixed dome Janata biogas plant installed in the hilly conditions of Himachal Pradesh was evaluated for its gas production efficiency for nearly 10 years as mentioned in this paper.
TL;DR: In this article, horse mixed with cattle dung in the ratios 0:1, 1:4, 2:3, 2.7, 4.7 and 4.4% less biogas were produced.
TL;DR: Results indicated that the continuous addition of active methanogenic population from the anaerobic digester rather than simple leachate recycle was effective for the rapid and significant CH 4 recovery from solid wastes.
TL;DR: In this paper, experiments were conducted using one-litre anaerobic batch bioreactors operated mesophilically and fed a mixture of primary sludge, thickened waste activated sludge (TWAS), and simulated organic municipal solid waste (MSW).
Abstract: Experiments were conducted using one-litre anaerobic batch bioreactors operated mesophilically (37 °C) and fed a mixture of primary sludge (RAW), thickened waste activated sludge (TWAS) and simulated organic municipal solid waste (MSW). A mixture of 25% MSW and 75% sewage sludge (60% RAW, 40% TWAS) yielded the highest biogas production. Based on biogas production, the most anaerobically biodegradable components were the white paper and grass components of the MSW. The TWAS and the newspaper components of the MSW were found to be the least biodegradable components. Both particle size and total solids concentration of the feed had a significant impact on the performance of the process. Over the operating region studied, the optimal operating conditions in terms of biogas production and volatile solids removal were at small particle sizes (0.85 mm, the smallest studied) and high total solids concentrations (22.1%, the highest studied).
TL;DR: In this paper, the anaerobic treatment of liquid fraction of hen manure was studied in two parallel laboratory 2·6 l UASB reactors at 35°C, and the results showed optimal stability with treatment efficiencies on total COD reduction of 70-75%.
TL;DR: It is shown that the reactor performance can be affected by 10% to 15%, depending on the mode of operation and recycle ratio used, at high organic loading rates, reactor performance is particularly sensitive to gas effervescence effects.
Abstract: The influence of mixing and phase hold-ups on gas-producing fluidized-bed reactors was investigated and compared with an ideal flow reactor performance (CSTR). The liquid flow in the anaerobic fluidized bed reactor could be described by the classical axially dis- persed plug flow model according to measurements of residence time distribution. Gas effervescence in the flu- idized bed was responsible for bed contraction and for important gas hold-up, which reduced the contact time between the liquid and the bioparticles. These results were used to support the modeling of large-scale fluid- ized-bed reactors. The biological kinetics were deter- mined on a 180-L reactor treating wine distillery waste- water where the overall total organic carbon uptake ve- locity could be described by a Monod model. The outlet concentration and the concentration profile in the reactor appeared to be greatly influenced by hydrodynamic limi- tations. The biogas effervescence modifies the mixing characteristics and the phase hold-ups. Bed contraction and gas hold-up data are reported and correlated with liquid and gas velocities. It is shown that the reactor per- formance can be affected by 10% to 15%, depending on the mode of operation and recycle ratio used. At high organic loading rates, reactor performance is particularly sensitive to gas effervescence effects. © 1998 John Wiley &
TL;DR: In this paper, the authors studied the optimal conditions of hydrogen-rich biogas production in a batch of fuel cells and verified the optimal working conditions for each stack of the above mentioned fuel cells.
Abstract: One of the best and cleanest systems to produce electric energy is represented by fuel cells, whose natural fuel is hydrogen. In this paper, the production of hydrogen rich biogas is studied. This process contributes to create a system for biomass recovery, which eliminates organic pollutants and produces energy with high efficiency without atmospheric emissions. The study has been based on Escherichia coli and Enterobacter aerogenes strains. The research deals with batch reactors and verification of optimal conditions of hydrogen production. The realization of the optimal working conditions would conduce to the realization of a reactor suitable to feed a stack of the above mentioned fuel cells. In view of industrial applications, some different ways have been considered to greatly enhance the process performance, in terms of rate of hydrogen production, efficiency of hydrogen utilization and/or biosynthesis of valuable subproducts.
TL;DR: In this paper, the needs and problems existing in the field of cultivation systems and waste management concerning elements and energy, as well as pollution, health, environment, and economy are described.
Abstract: The needs and problems existing in the field of cultivation systems and waste management concerning elements and energy, as well as pollution, health, environment, and economy are described. The lack of reproducible biofertilisers of high quality calls for an efficient use of organic waste as a renewable raw material. Each 100 000 inhabitants in Sweden generate organic waste with considerable economic values in terms of nitrogen, phosphorus, and potassium; US$ 600 000 from the organic fraction of municipal solid waste and US$ 900 000 from human excreta as liquid organic waste, meanwhile only US$ 160 000 is recovered from the sewage sludge after the wastewater has passed the wastewater treatment plants. Most of the existing systems for handling solid and liquid waste are of old-fashioned design and cause large losses of nutrient elements. Therefore, pollution of air, water, soil, and vegetation, mainly by emissions from organic uaste, continues. Bioconversion is microbial transformation and upgrading of various organic wastes to products of high value. The elements can be efficiently recycled in completely closed local bioconversion systems with subsystems for collection, pre-processing, processing, and application of end-products. Solid and liquid organic waste from the municipality can provide renewable raw material for manufacturing of reproducible biofertilisers and of biogas. Suggestions are made on how to improve the present situation by the re-orientation of technology. A scenario for bioconversion by the year 2010 is presented.