Showing papers on "Biogas published in 1996"
TL;DR: In this article, a continuous production of hydrogen from sugary wastewater by anaerobic microflora in chemostat culture was examined as a function of hydraulic retention time (HRT) in the reactor.
327 citations
TL;DR: In this article, the effect of variations of carbon dioxide in biogas on the performance of the engine was examined to simulate the engine running with different sources (varying proportion of methane and carbon dioxide).
128 citations
Book•
01 Jan 1996
TL;DR: In this article, the authors present a case study of gas migration, emissions and safety aspects in the context of gas generation and composition, extraction and transportation, and treatment of gas.
Abstract: Introduction. Gas generation and composition. Environmental aspects. Gas production. Extraction and transportation. Gas treatment. Gas utilisation. Gas migration, emissions and safety aspects. Case studies. Index.
106 citations
TL;DR: In this article, the performance of a two-stage, two-phase, unmixed anaerobic digester of 155 l working volume operating on acid cheese whey and dairy manure at various temperatures and hydraulic retention times was investigated.
101 citations
TL;DR: In this paper, the anaerobic digestion of waste water containing significant levels of coffee grounds was assessed in mesophilic and thermophilic batch studies and CSTRs fed daily.
96 citations
TL;DR: It was concluded that the mesophilic co-digestion process is applicable with potentialities of around 30% of the present SS flow-rate and Thermophilic digestion is not possible, because of the inhibition of methanogens probably due to the activity of sulphate-reducers.
Abstract: Possibilities of co-digestion of sewage sludge (SS) with other organic wastes are examined in this paper. Anaerobic co-digestion of macroalgae of the Venice lagoon (A) with SS, in wastewater treatment plants is studied in detail. This approach can contribute to the solution of the final disposal of the 50 000 m 3 of macrophytes harvested each season. These are mainly Ulva rigida and Gracilaria confervoides . In the experiments A and SS were mixed at different ratios (20–40% algae, TS basis) and fed to mesophilic (37°C) and thermophilic (55°C) digesters which operated at 11- to 15-day hydraulic retention times and 1.7–4.4 kgTVS/m 3 /day organic loading rates. It was concluded that the mesophilic co-digestion process is applicable with potentialities of around 30% of the present SS flow-rate. Thermophilic digestion is not possible, because of the inhibition of methanogens probably due to the activity of sulphate-reducers.
88 citations
TL;DR: It is found that during both the intense and stable methanogenic (but not the acidogenic) phases, the microoganisms in the samples had the potential to transform PA, indicating an increased capacity to degrade PA during the aging phases of the municipal solid waste in landfills.
Abstract: Anaerobic microorganisms in municipal solid waste samples from laboratory-scale landfill reactors and a pilot-plant biogas digestor were investigated with the aim of assessing their ability to transform four commercially used phthalic acid esters (PAEs) and phthalic acid (PA). The PAEs studied were diethyl phthalate (DEP), butylbenzyl phthalate (BBP), dibutyl phthalate (DBP) and bis(2-ethylhexyl) phthalate (DEHP). No biological transformation of DEHP could be detected in any of the experiments. Together with waste samples from the simulated landfilling conditions, the PAEs (except DEHP) were hydrolytically transformed to their corresponding monoesters. These accumulated as end products, and in most cases they were not further degraded. During incubation with waste from the biogas digestor, the PAEs (except DEHP) were completely degraded to methane and carbon dioxide. The influence of the landfill development phase on the transformations was investigated utilizing PA and DEP as model substances. We found that during both the intense and stable methanogenic (but not the acidogenic) phases, the microorganisms in the samples had the potential to transform PA. A shorter lag phase was observed for the PA transformation in the samples from the stable methanogenic phase as compared with earlier phases. This indicates an increased capacity to degrade PA during the aging phases of the municipal solid waste in landfills. No enhancement of the DEP transformation could be observed as conditions in the methanogenic landfill model changed over a year's time. The results indicate that microorganisms developing in a methanogenic landfill environment have a substantially lower potential to degrade compared with those developing in a biogas reactor.
83 citations
TL;DR: In this paper, gas chromatography on a fused-silca column using flame ionization detection (GC/FID) was used to determine volatile cyclic organic siloxanes in the biogas of digested sludge.
Abstract: Volatile cyclic organic siloxanes in the biogas of digested sludge can shorten the life time of gas engines producing energy from the biogas. These siloxanes have been determined by gas chromatography on a fused-silca column using flame ionization detection (GC/FID). To extract siloxanes from biogas, spiked biogas or spiked carbon dioxide XAD resins, activated carbon, polyurethane foam and tetradecane have been tested. Adsorption from the gas have been accomplished successfully with XAD resins, activated carbon and tetradecane, but quantitative recoveries from the adsorbens have been achieved only using XAD and ultra sonification. Determinations from waste water, activated or digested sludge could be carried out successfully after stripping the siloxanes from these samples by helium and adsorption on XAD. Elimination from biogas was possible by adsorption or degradation. XAD adsorption eliminated siloxanes quantitatively but the regeneration of the resins was necessary. Aqueous sodium hydroxide solutions at 20 or 60°C have proven as ineffective in degradation whereas concentrated sulfuric acid at a temperature of 60°C eliminated siloxanes quantitatively.
82 citations
Patent•
16 Jan 1996
TL;DR: Waste landfill gases are treated and separated by a combination of gas cleaning, gas compression, gas cooling, and gas absorption processes to produce high quality liquefied natural gas, liquid carbon dioxide and compressed natural gas products as mentioned in this paper.
Abstract: Waste landfill gases are treated and separated by a combination of gas cleaning, gas compression, gas cooling, and gas absorption processes to produce high quality liquefied natural gas, liquefied carbon dioxide and compressed natural gas products.
76 citations
TL;DR: In this paper, a mathematical model for codigesting piggery, olive-mill and dairy wastewaters was developed based on batch kinetic experiments, and an organic loading rate of 3.84 g COD/l·d was found to be safe for a digester operating on a year-round basis.
62 citations
TL;DR: In this article, the authors evaluated the performance of an up-flow type reactor working in series with a fixed-bed-type reactor, which was used as a complementary treatment.
TL;DR: In this paper, the authors evaluated the performance of psychrophilic anaerobic digestion in sequencing batch reactors (SBRs) under operating strategies that would optimize process performance and stability while minimizing the interference of the bioreactor operation with regular farm activities.
Abstract: The objective of this study was to evaluate the performance of psychrophilic anaerobic digestion in sequencing batch reactors (SBRs) under operating strategies that would optimize process performance and stability while minimizing the interference of the bioreactor operation with regular farm activities. Process performance was evaluated on (i) reduction in pollution potential; (ii) energy recovery; and (iii) odour reduction. Experiments were carried out in twelve 40-L SBRs. Experimental results indicated that psychrophilic anaerobic digestion of swine manure slurry at 20 °C in an intermittently fed SBR (i) reduced the pollution potential of swine manure slurry by removing 84 – 93% of the soluble chemical oxygen demand and 41 – 83% of total chemical oxygen demand; (ii) produced biogas at rates exceeding 0.48 L of CH4 per gram of volatile solids fed; and (iii) successfully reduced odours. Other findings were that (i) for all experimental runs, psychrophilic anaerobic digestion of swine manure slurry in SBR...
TL;DR: In this paper, the authors describe a digester design which can make this waste-to-energy conversion process possible, made possible by an integration of modern industrial digestion processes, and low-technology digestion concepts as seen in rural Chinese and Indian digesters.
Journal Article•
TL;DR: In this paper, the main streams, produced in the cooking of mussel or tuna and in the manufacture of fish-meal, were treated individually or in combination at an industrial pilot plant, with an anaerobic central activity digester of 15 m 3, for two years.
Abstract: Fish and shellfish canning industries produce waste waters whose characteristics depend upon the raw material processed which, in turn, varies throughout the year. Some production lines operate simultaneously, although it is possible to segregate or combine streams in order to optimise the treatment process. The main streams, produced in the cooking of mussel or tuna and in the manufacture of fish-meal, were treated individually or in combination at an industrial pilot plant, with an anaerobic central activity digester (CAD) of 15 m 3 , for two years. The most noticeable characteristics of wastes are their high organic load (COD 20 to 90 g/l) and the salinity (up to 14 g/l of Cl - ). Another problem is the high ammonia content, up to 4.5 g/l, produced after the degradation of proteins. A strategy for adapting sludges to the salinity and to the ammonia content was followed and specific methanogenic activities of 0.7 kg COD/kg VSS.d were achieved, with chloride, sodium and ammonia concentrations of up to 15.5, 9.7 and 3.5 g/l, respectively. COD reductions, applied OLR and HRT ranged between 70 and 90%, 5 to 6 kg COD/m 3 .d and 4.5 to 5 d, respectively. During the entire experimental period, nutrients addition was not necessary and pH remained neutral due to the high buffering capacity of the process (3 to 4 g CaCO 3 /l. Sudden changes in the influent composition did not affect the stability of the process, except when high suspended solids mixtures were treated. The biomass content in the digester varied around 11 g VSS/l and the mean specific methane production was 301 l/kg COD removed (15°C, 1 atm), with a biogas content of 60 to 65%. Hydrogen sulphide in biogas ranged from I to 4%. The mean anaerobic biodegradability was calculated for the main influents treated, being 84.9% for tuna-cooking effluents, 92.7% for mussel-cooking effluents, 79.4% for mixtures of tuna and mussel effluents and 71.4% for the tuna/mussel/fish-meal mixtures.
TL;DR: In this paper, the authors give an overview of the energy demands in Tanzania, and highlight the current serious shortage of electricity, highlighting the current government strategy to alleviate the problem include exploitation of the country's big natural gas reserves for power generation, and utilization of the renewable energies such as solar, wind and biogas.
TL;DR: In this article, the methane production characteristics of a full scale anaerobic biogas digester processing the putrescible fraction of municipal solid waste (PFMSW) and sewage sludge (SS) were studied by using the operation data of the digester and laboratory experiments.
TL;DR: In this paper, the effect of temperature and retention period on biogas production from lignooellulosic material, hereafter referred to as cow dung, was studied and the results showed that gas production was qotimum at 4th and 7th weeks of production.
TL;DR: The solubilization rates of some organic residues during anaerobic biomethanation have been studied and rate equations developed and the effects of selected variables on the solubILization rate have been determined.
TL;DR: In this paper, the effect of controlling the refuse bacterial content as a management practice to enhance methane yield was evaluated using a gas generation-microbial growth model that is based on the sequential degradation of organic materials in anaerobic systems.
Abstract: Methane gas is an energy source that can be produced from the decomposition of organic materials in municipal solid waste landfills. The feasibility of exploiting this source of energy is continually increasing due to continuing trends in population increase and urbanization resulting in significant increases in solid waste production and potential methane generation. Indeed, during the last decade, there has been considerable growth in the number of landfill gas recovery and utilization systems. This paper describes estimation methods used in assessing methane yield and generation rates from municipal solid waste landfills. Parameters affecting methane generation rates and models used to predict these rates are described. The effect of controlling the refuse bacterial content as a management practice to enhance methane yield was evaluated using a gas generation-microbial growth model that is based on the sequential degradation of organic materials in anaerobic systems.
TL;DR: In this article, a bench-scale experimental study was carried out to investigate the overall performance of a combined anaerobic reactor for treating pre-settled municipal wastewater at ambient temperature in terms of substrate removal efficiencies, biogas, methane production, volatile fatty acid (VFA) profiles, etc.
Abstract: A bench-scale experimental study was carried out to investigate the overall performance of a combined anaerobic reactor for treating pre-settled municipal wastewater at ambient temperature (18–28°C) in terms of substrate removal efficiencies, biogas, methane production, volatile fatty acid (VFA) profiles and effluent suspended solids (SS) concentration, etc The tested reactor was a modified anaerobic baffled reactor (ABR) The second and third compartments were partly packed with supporting media The experimental results were similar to, or compared favourably with, other anaerobic reactor systems for municipal wastewater treatment at ambient temperature and proved the technical feasibility of this compartmentalised reactor Considering its simple structure and operation, it could be considered a potential reactor system for treating municipal and domestic wastewaters in tropical and sub-tropical areas of developing countries
Patent•
17 Dec 1996
TL;DR: In this article, an original and profitable industrial method was described to process garbage, in which were included: a) separation of written paper on the incoming garbage mechanically or manually which is deinked and pulped to chemical pulp; b) cutting the garbages to 3-5 cm and subjecting them to water flotation in a canal slowly running water in which are separated floating light products processed to separate polymers and to produce pulp, heavy precipitating products processing to separate iron metals, soft metals and glass and suspended organic mass which is further processed.
Abstract: An original and profitable industrial method is described to process garbage, in which are included: a) separation of written paper on the incoming garbage mechanically or manually which is deinked and pulped to chemical pulp; b) cutting the garbages to 3-5 cm and subjecting them to water flotation in a canal slowly running water in which are separated floating light products processed to separate polymers and to produce pulp, heavy precipitating products processed to separate iron metals, soft metals and glass and suspended organic mass which is further processed; c) utilisation of suspended organic mass after further purification and after prehydrolysis to produce digestible lignocellulosics in anaerobic digestion in the thermophilic region to yield high amounts of biogas, 85 % in methane content, utilised to produce electric energy at high yield; d) utilisation of the anaerobically digested sludge in the production of mixed fertilisers humic-chemical-organic after co-composting treatment in the thermophilic region. That way the garbage is utilised fully and nothing is rejected so that landfilling is not needed.
TL;DR: In this article, the authors describe the enhancement of biogas production in laboratory-scale anaerobic digesters (with batch and semi-continuous operation) using iron-enriched duckweed as a supplement to the digestion of feedstock.
Abstract: This paper describes the enhancement of biogas production in laboratory-scale anaerobic digesters (with batch and semi-continuous operation) using iron-enriched duckweed as a supplement to the digestion of feedstock. The relationship between the level of enhancement achieved and the retention period of the digesters was also investigated. The trials demonstrated that, in batch digesters, iron-enriched duckweed significantly improved the rate of microbial succession. Batch digesters receiving no duckweed took 40 days to reach peak methane production compared to 15 days when duckweed was added. In the semi-continuous digesters, an increase in gas production of about 44% was observed.
TL;DR: The results show a clear effect of mixing on digester operation and the importance of mixing and its critical role in design of large scale anaerobic digesters.
Abstract: Manure waste from dairy farms has been used for methane production for decades, however, problems such as digester failure are routine. The problem has been investigated in small scale (1–2 L) digesters in the laboratory; however, very little scale-up to intermediate scales are available. We report production of methane in a 100-L digester and the results of an investigation into the effect of partial mixing induced by gas upflow/recirculation in the digester. The digester was operated for a period of about 70 d (with 16-d hydraulic retention time) with and without the mixing induced by gas recirculation through an internal draft tube. The results show a clear effect of mixing on digester operation. Without any mixing, the digester performance deteriorated within 30–50 d, whereas with mixing continuous production of methane was observed. This study demonstrates the importance of mixing and its critical role in design of large scale anaerobic digesters.
TL;DR: In this article, the kinetics of anaerobic digestion of cane molasses distillery slops were investigated using a continuous-flow bioreactor which contained waste tyre rubber as support, to which the microorganisms became immobilized.
Abstract: The kinetics of anaerobic digestion of cane molasses distillery slops was investigated using a continuous-flow bioreactor which contained waste tyre rubber as support, to which the microorganisms became immobilized. Hydraulic retention times (HRT) ranging from 1 to 10 days were investigated at an average influent chemical oxygen demand (COD) concentration of 47.7 g/l. The maximum substrate utilization rate, k, and half saturation coefficient, K
L, were determined to be 1.82 kg CODremoved/kg VSS day and 0.33 kg COD/kg VSS day. The yield coefficient, Y, and sludge decay rate coefficient, K
d, were also determined to be 0.06 kg VSS/kg CODremoved and 0.05 day-1, respectively. Methane production was maximum (6.75 l/l day) at a 2 day HRT corresponding to a biomass loading rate of 2.578 kg COD/kg VSS day. Biogas yield ranged between 0.51 l/g COD (HRT=2 days) and 0.25 l/g COD (HRT=1 day). In addition, the methane percentage in the biogas varied between 70.5% (HRT=10 days) and 47.5% (HRT=1 day). The close relationship between biomass loading rate and specific substrate utilization rate supported the use of Monod equations. Finally, the experimental values of effluent substrate concentration were reproduced with deviations equal to or less than 10% in every case.
Patent•
13 Sep 1996
TL;DR: Anaerobic digestion of wastewaters can be made more effective by introducing propane gas from an external source in order to strip gas produced by the anaerobic fermentation from the biomass system as mentioned in this paper.
Abstract: Anaerobic digestion of wastewaters can be made more effective by introducing propane gas from an external source therein in order that the propane gas strips gas produced by the anaerobic digestion (eg, methane, carbon dioxide, etc) from the biomass system
TL;DR: In this article, stable isotope ratios for improving the understanding of methane and carbon dioxide generation in landfills were evaluated using a large dataset of approximately 130 landfill gas samples from across the U.S.
TL;DR: In this paper, the present state of municipal solid waste (MSW) disposal in Argentina, focusing on the particular situation of the city of Salta, and suggests the future trend of the anaerobic treatment of this residue.