Inlet Biogas Research Articles

Study of On-Site Upgraded Livestock Biogas Production and Carbon Emission Reduction By Substituting Coals For Thermal Power Generation

The objective of this project is to integrate a farm-scale bio-desulfurization facility with a novel biogas hollow fibre adsorption module for biogas desulfurization and bio-natural gas production. In this study, the desulfurization experimental results showed that the bio-desulfurization system can remove 96.7 ± 6% of H2S from the biogas after an approximately two-month enrichment period. The average CH4, N2, and CO2 concentrations in raw biogas were 63.4, 15.2, and 21.1%, respectively. As for biogas upgrading experiments, the inlet biogas flow rates were applied from 5 to 20 L/min. The removal efficiency of CO2 under all biogas flow rates was 100%. Meanwhile, methane was promoted from 60% to nearly 94% (i.e. 57% increase in methane concentration). The replacement of anthracite and coking coal by upgraded biogas might reduce 44.4% and 42.5% of CO2 equivalent, respectively. The achievement of this project pursues the mitigation of carbon dioxide emissions by using upgraded pig biogas which can be enlarged and extended to all decentralized pig farms worldwide.

Study of on-site upgraded livestock biogas production and carbon emission reduction by substituting coals for thermal power generation

The objective of this project is to integrate a farm-scale bio-desulfurization facility with a novel biogas hollow fibre adsorption module for biogas desulfurization and bio-natural gas production. In this study, the desulfurization experimental results showed that the bio-desulfurization system can remove 96.7 ± 6% of H2S from the biogas after an approximately two-month enrichment period. The average CH4, N2, and CO2 concentrations in raw biogas were 63.4, 15.2, and 21.1%, respectively. As for biogas upgrading experiments, the inlet biogas flow rates were applied from 5 to 20 L/min. The removal efficiency of CO2 under all biogas flow rates was 100%. Meanwhile, methane was promoted from 60% to nearly 94% (i.e. 57% increase in methane concentration). The replacement of anthracite and coking coal by upgraded biogas might reduce 44.4% and 42.5% of CO2 equivalent, respectively. The achievement of this project pursues the mitigation of carbon dioxide emissions by using upgraded pig biogas which can be enlarged and extended to all decentralized pig farms worldwide.

Simultaneous removal of H2S and NH3 from raw biogas in hollow fibre membrane bioreactors

H 2 S and NH 3 are toxic, corrosive and odorous gases that often co-exist in gas streams emitted from industrial processes, including biogas produced in anaerobic digestion plants. A hollow fibre membrane bioreactor (HFMB) was tested for simultaneous biological removal of H 2 S and NH 3 from raw biogas. The HFMB achieved a removal efficiency (RE) > 99% for treating up to 1850, 915 and 1200 ppm v of H 2 S at an empty bed residence time (EBRT) of 187, 92 and 46 s, respectively. The RE of NH 3 was > 99% when the inlet NH 3 concentrations were up to 460, 355 and 750 ppm v at an EBRT of 187, 92 and 46 s, respectively. At an EBRT of 46 s, the RE of H 2 S and NH 3 was in the range of 85–97 and 73–95%, respectively, for inlet biogas laden with 1200–1700 ppm v of H 2 S and 750–1050 ppm v of NH 3 . The critical loading rates of H 2 S and NH 3 were about 150 and 40 g m −3 h −1 , respectively. S 0 (52%), SO 4 2 − (48%) and N 2 (92%) were the end products of the H 2 S and NH 3 bioconversion. Different sulfide oxidizers including aerobic (e.g. Smithella sp., Sulfuricurvum sp. and Thiomonas sp.) and anoxic (e.g. Rhodanobacter sp., Sulfuritalea sp. and Thiobacillus sp.) chemolithotrophs contributed to the H 2 S bioconversion. Aerobic (e.g. Pseudomonas sp., Stenotrophomonas sp. and Nitrosospira sp.) and Fe(III) dependent anaerobic (e.g. Clostridium_sensu_stricto_12 sp., Rhodoferax sp. and Dechloromonas sp.) ammonium oxidizers contributed to the NH 3 bioconversion. Denitrifiers including denitrifying phosphorus accumulating organisms (e.g Candidatus_Contendobacter sp.) contributed to the denitrification process. • Hydrophilic polyethersulfone HFMB simultaneously treated H 2 S and NH 3 from raw biogas. • Maximum H 2 S and NH 3 flux through membrane module was 1.94 and 0.55 g m -2 day -1 , respectively. • The critical loading rate of H 2 S and NH 3 was close to 150 and 40 g m -3 h -1 , respectively, at an EBRT of 46 s. • Outlet/inlet CH 4 ratio ( ∼ 0.99) confirmed low ( < 1%) biogas dilution in the HFMB. • Both aerobic and anoxic processes contributed to H 2 S and NH 3 bioconversion in the HFMB.

An innovative integrated CCHP system with water scrubbing‐based biogas upgrading unit and molten carbonate fuel cell

AbstractThe main purpose of this study is to develop an integrated structure of simultaneous generation of electricity and refrigeration as the main product and hot water as a by‐product. This proposed structure consists of a water scrubbing biogas upgrading process, molten carbonate fuel cell (MCFC) unit, gas/steam power (GSP) cycle, and absorption refrigeration (AR) system. In this regard, 10.71 kg/s untreated biogas enters the integrated system and 158,351 kW net power is produced. Wasted heat of the structure is utilized to generate cooling of 253.9 kW at a temperature of 243.6 K by applying the AR system and the rest of the heat is used to generate 8.391 kg/s hot water as the system byproducts. The process integration between the different parts has led to an increase in the thermal efficiency of the whole system so that the electrical and overall efficiencies are 78.68% and 79.86%, respectively. The investigation of the exergy study demonstrates that the exergy destruction of the entire structure is 71,859 kW, of which the turbine/compressor/pump section with 24,700 kW (with a share of 34.37% of the total) and MCFC/reformer section with 22,285 kW (with a share of 31.01% of the total) have the most irreversibility. The exergy efficiency of the hybrid structure is 71.06%. Through a parametric study, the present integrated system in various conditions is assessed. One of the results of main outcomes is the increase of overall efficiency up to 83.39% due to the reduction of inlet biogas methane mole content up to 50%. Rising the methane in inlet biogas, although leading to more production of system products, reduces the efficiencies of various parts of the system, including the MCFC unit and GSP cycle, as well as integrated system total efficiency.

Study of livestock biogas upgrading using a pilot-scale photocatalytic desulphurizer followed by a hollow fibre carbon dioxide adsorption module

AbstractThe objective of this project is to integrate a domestic photocatalytic desulphurization facility with a biogas upgrading module and try to develop a system for biogas desulphurization and upgrading under ambient conditions. Four photocatalytic desulphurization reactors (PDRs) and one activated carbon reactor (ACR) were applied for biogas desulphurization and filtration under ambient conditions. Moreover, a hollow fibre carbon dioxide (CO2) adsorption module was applied for biogas upgrading. The operation pressure of the PDR and ACR was under ambient pressure. Results showed that hydrogen sulphide removal efficiency of the photocatalytic desulphurizer was about 0.99–1.00 (v/v) under the inlet biogas flow less than 5 litres/min and the concentration of inlet hydrogen sulphide was lower than 5600 mg/m3. For desulphurized biogas upgrading, the removal efficiency of CO2 was higher than 0.90 (v/v) under the outlet biogas flow was 1 litre/min (i.e. inlet biogas flow was about 2 litres/min). However, the ratio of methane in the upgrading biogas was lower than 0.90 (v/v). Thus, nitrogen gas removal cartridges will be integrated with the biogas upgrading module to promote methane concentration in the upgraded biogas.

Cryogenic biogas upgrading process using solar energy (process integration, development, and energy analysis)

Biogas upgrading is a process that increases methane content to an acceptable percentage is compared with natural gas and reduces impurities such as CO2 and H2S in the biogas. Several methods for biogas upgrading are used. The selection of biogas upgrading methods depends on the type of biogas and the facilities’ requirement according to local circumstances. This paper presents a study on an integrated process of cryogenic biogas upgrading by using renewable energy resources for sustainable development. Parabolic trough solar collector (PTC), organic Rankine cycle (ORC) power system and absorption refrigeration cycle are used in this process to separate the impurity of raw biogas. PTC supplies the required heat for the ORC, and absorption refrigeration cycles. Inlet biogas contains 61.10%, 36.93% and 0.01% (mole percent) CH4, CO2 and H2S. After purification, upgraded biogas contains 92.67% CH4 and 4% CO2. The results of the exergy analysis of the process show that the overall exergy efficiency of the integrated process and solar collector are 71.62% and 51.37% respectively. Also, the cryogenic heat exchangers have the highest exergy efficiency while the most exergy destruction occurs in the solar collector and afterward in the column. Sensitivity analysis on the effective parameters such as wind speed, ambient temperature, and auxiliary energy ratio is investigated.

Desulfurization of Biogas from a Closed Landfill under Acidic Conditions Deploying an Iron-Redox Biological Process

Desulfurization processes play an important role in the use of biogas in the emerging market of renewable energy. In this study, an iron-redox biological process was evaluated at bench scale and pilot scale to remove hydrogen sulfide (H2S) from biogas. The pilot scale system performance was assessed with real biogas emitted from a closed landfill to determine the desulfurization capacity under outdoor conditions. The system consisted of an Absorption Bubble Column (ABC) and a Biotrickling Filter (BTF) with useful volumes of 3 L and 47 L, respectively. An acidophilic mineral-oxidizing bacterial consortium immobilized in polyurethane foam was utilized to regenerate Fe(III) ion, which in turn accomplished the continuous H2S removal from inlet biogas. The H2S removal efficiencies were higher than 99.5% when H2S inlet concentrations were 120–250 ppmv, yielding a treated biogas with H2S &lt; 2 ppmv. The ferrous iron oxidation rate (0.31 g·L−1·h−1) attained when the system was operating in natural air convection mode showed that the BTF can operate without pumping air. A brief analysis of the system and the economic aspects are briefly analyzed.

Theoretical evaluation and optimization of a cryogenic technology for carbon dioxide separation and methane liquefaction from biogas

The transport sector represents one of the major cause of air pollution and greenhouse gases emissions. For this reason, several measures have been taken: penalty and incentive schemes have been introduced worldwide to increase renewable energy sources and alternative fuels use. It is widely accepted that natural gas (NG) is a good alternative fuel, especially in its liquid form (LNG), and it can be produced using biogas as methane source to obtain renewable liquefied biogas (LBG). However raw biogas contains several impurities and it needs to be pre-treated. At present, several technologies allow biogas purification. In particular cryogenic separation represents a promising solution for simultaneous purification and liquefaction. It can achieve impurities removal and methane liquefaction by means of a single plant. In this work, a novel cryogenic separation process, based on CO2 cold recovery, is presented. The proposed plant is optimized and a sensitivity analysis is also performed. Results indicate that the proposed plant represents a valid option for LBG production. Indeed the specific energy consumption is 1.574 kWh kg−1 for a CO2 content in inlet biogas of 50%. Furthermore the energy use and operative costs are compared with those of standard technologies and they result respectively 23% and 22% lower, taking into account the influence of CO2 as by-product.

Methanol Synthesis: a Distributed Production Concept Based on Biogas Plants

Today biogas produced from anaerobic digestion is used mainly for thermic and electric energy production. Its use as raw material for syngas production and further upgrading to chemical products like methanol (MeOH), dimethyl ether (DME) or acetic acid could be an interesting option as process intensification. In this work the sustainability of a Biogas-to-MeOH (BtoMeOH) or Biogas-to-DME (BtoDME) process was studied. The biogas feedstock of the Combined Heat, Power and Chemicals (CHPC) is equivalent to the production of 1 MWe in a Combined Heat and Power Plant (CHP). Biogas is converted using a reformer into syngas to produce methanol. The plant was designed considering mild conditions for chemical production and the energy necessary to reactors was generated using a fraction of the inlet biogas. This process was studied using the Simulation Suite PRO/II® by Schneider-Electric Simulation Science. The reformer and the methanol reactorproductivity were evaluated with the experimental data obtained through bench scale plants. An economicanalysis was performed to assess the sustainability of these new processes, capital and operative costs of the plants were evaluated using the Guthrie’s method. The Biogas-to-MeOH process can produce up to 297 kg h-1 of methanol with recycle. The biogas necessary to supply the energy demand of the plant is 192 kg h-1, a third of the inlet feedstock. For the Biogas-to-DME process the energy demand is similar while the DME production is 173 kg h-1. The preliminary economic evaluation shows that the main item for the capital costs are reactors and compressors and the breakeven point of both processes is 3 years. Despite the lower productivity, DME process is more convenient due to a higher market value.

Simulation of Electricity Generation from Biogas for Ugandan Rural Community

One of Uganda’s greatest hindrances to development is lack of access to energy. In rural areas where about 84% of the population lives, access to electricity is less than 2% a situation that lives rural communities to continue depending on biomass based fuels in forms of firewood and charcoal. This paper proposes the utilization of biogas to generate off-grid electricity for the rural community. A simulation of electricity generation from biogas for Ugandan rural community using Aspen HYSYS V8.8 for computational modeling was developed on thermodynamic concepts. Two systems were considered; a gas-turbine (GT) only system and a GT-with steam turbine (ST) in the bottom cycle, based on 71% methane - 29% carbon dioxide as inlet biogas composition. The results obtained showed that it is possible to obtain 2.5MW of electricity using a gas turbine (GT) only system and an additional 1MW when a combined cycle system (GT-ST) is considered. An analysis of the exhaust gases showed that there are negligible amounts of gaseous pollutant though not in amounts that could constitute environmental threats when disposed to the atmosphere. In order to meet the system’s need, a cattle head count of 13740 is estimated to be maintained for a daily supply of 670 tons of cow manure.

Efficiency Evaluation of Biofilter for Hydrogen Sulfide Removal from Palm Oil Mill Biogas

Hydrogen sulfide (H2S) is one of the most problematic contaminants in biogas. The removal of H2S from biogas is necessary in order to clean biogas and prevent gas engine. The efficiency evaluation on H2S removal from palm oil mill biogas by biofilter was investigated. Eight sludge samples from biofilter systems of palm oil mill biogas were tested for H2S removal by grown in thiosulfate mineral medium under an anaerobic condition at atmospheric pressure. Analytical data demonstrated that average amounts of CH4, CO2, and H2S in inlet biogas were 62%, 35%, and 0.95%, respectively. The highest H2S removal rate of 0.35 g/L/d was found sludge A (Asian palm oil company). It also found that the major product for sludge A was elemental sulfur of 13,650 mg/L and could produce the highest sulfate concentration of 300 mg/L. In contrast, sludge I (Thai Indo palm oil factory) has the lowest H2S removal with rate (0.09 g/L/d.) Microbial activity for H2S removal was increased with the decrease in pH from 7.12 to 6.40 due to H2S dissolved medium. The suitable condition for the growth of sulfur oxidizing bacteria affected on H2S removal efficiency from palm oil mill biogas by biofilter systems.

Microbial electrochemical separation of CO2 for biogas upgrading

Biogas upgrading to natural gas quality has been under focus the recent years for increasing the utilization potential of biogas. Conventional methods for CO2 removal are expensive and have environmental challenges, such as increased emissions of methane in the atmosphere with serious greenhouse impact. In this study, an innovative microbial electrochemical separation cell (MESC) was developed to in-situ separate and regenerate CO2 via alkali and acid regeneration. The MESC was tested under different applied voltages, inlet biogas rates and electrolyte concentrations. Pure biomethane was obtained at 1.2V, inlet biogas rate of 0.088mL/h/mL reactor and NaCl concentration of 100mM at a 5-day operation. Meanwhile, the organic matter of the domestic wastewater in the anode was almost completely removed at the end. The study demonstrated a new sustainable way to simultaneously upgrade biogas and treat wastewater which can be used as proof of concept for further investigation.

Biogas Upgrading Using Ash from Combustion of Wood Fuels: Laboratory Experiments

The value of biogas produced at small scale facilities, such as farm scale biogas plants, can increase by upgrading it to vehicle fuel quality. However, commercial upgrading technologies available today are very costly for small scale applications. Ash from combustion of wood fuels has a high content of Ca, which indicates favourable conditions for a high CO2 uptake capacity from biogas. The objective of this study was to assess the CO2 uptake capacity of ash from combusted wood pellets and wood chips in a laboratory scale solid bed reactor using an inlet gas mixture of CO2 and CH4 with the aim to reach &gt; 97 % CH4 in the outlet gas. A gas with a defined composition of 65 % CH4 and 35 % CO2 was passed through a moisturised solid ash bed in an up-flow manner. The gas quality in the outlet gas and the CO2 uptake capacity of the ash was assessed. Bottom ash from combusted wood pellets showed the best uptake capacity of 0.20 g CO2/g dry ash, which is 4-8 higher than studies where municipal solid waste incineration bottom ash was tested. The outlet gas from the ash reactor contained high concentrations of methane (up to 99.6 %) and the gas contained no CO2 until CO2 breakthrough occurred in the ash bed. Furthermore, the pH of the ash was reduced by 2 to 3 units due to the carbonation, which improves the prerequisites for recycling the ash to forestry. It was concluded that an ash bed with Ca rich wood ash has the ability to reach vehicle fuel quality regarding CH4 concentration. Based on the results, a biogas plant of 1 GWh (3.6 TJ) per year would require approx. 650 tonnes of dry wood ash a year with an uptake of 0.20 g CO2/g dry ash and an inlet biogas composition of 60 % CH4 and 40 % CO2.

Valorization of MSWI bottom ash for biogas desulfurization: Influence of biogas water content

In this study an alternative valorization of Municipal Solid Waste Incineration (MSWI) Bottom Ash (BA) for H2S elimination from landfill biogas was evaluated. Emphasis was given to the influence of water content in biogas on H2S removal efficiency by BA. A small-scale pilot was developed and implemented in a landfill site located in France. A new biogas analyzer was used and allowed real-time continuous measurement of CH4, CO2, O2, H2S and H2O in raw and treated biogas. The H2S removal efficiency of bottom ash was evaluated for different inlet biogas humidities: from 4 to 24gwater/m3. The biogas water content was found to greatly affect bottom ash efficiency regarding H2S removal. With humid inlet biogas the H2S removal was almost 3 times higher than with a dry inlet biogas. Best removal capacity obtained was 56gH2S/kgdryBA. A humid inlet biogas allows to conserve the bottom ash moisture content for a maximum H2S retention.

Methane production from a field-scale biofilter designed for desulfurization of biogas stream

The development of a simple and low maintenance field-scale biotrickling filter (BTF) for desulfurization of swine wastewater-derived biogas stream that was also capable of increasing biomethane concentrations was investigated. BTF was continuously fed with wastewater effluent from an air sparged nitrification-denitrification bioreactor installed downgradient from an UASB-type digester. BTF maximum removal efficiency (RE) of 99.8% was achieved with a maximum elimination capacity (EC) of 1,509 g H2S m−3 h−1. Average EC obtained with inlet biogas flow rates of 0.024, 0.036 and 0.048 m3 h−1 was 718, 1,013 and 438 g H2S m−3 h−1, respectively. SO4−2 and S0 were the major metabolites produced from biological conversion of H2S. Additionally to the satisfactory biodesulfurization capacity, an average increase in methane concentration of ≅ 3.8 ± 1.68 g m−3 was measured in the filtered gas stream throughout 200 days of BTF operation. RT-PCR analyses of archaea communities in the biofilm confirmed dominance of hydrogenotrophic methanogens thus corroborating with the observed strong correlation between CO2 removal and CH4 production. Among the three major archaea orders investigated (i.e., Methanosarcinales, Methanobacteriales, and Methanomicrobiales), Methanobacteriales were encountered at highest concentrations (1.9 × 1011 gene copies mL−1). The proposed BTF was robust efficiently removing H2S from biogas stream while concomitantly enhancing the concentration of valuable methane as source of renewable fuel.

Biofiltration of methane emissions from a dairy farm effluent pond

Dairy farm effluent ponds are a source of methane (CH4), a potent greenhouse gas. Biofiltration, whereby CH4 is oxidised by methanotrophic bacteria, is a potentially cost-effective CH4 mitigation technology. We report on the performance of a field-scale biofilter treating dairy farm effluent pond CH4 emissions for 16 months. This study is the first to report on the feasibility of using biofiltration to mitigate dairy waste CH4 emissions. The 70-L filter comprised a 1:1 volumetric mixture of volcanic soil from a landfill and perlite. Biogas collected in a floating cover on a 4-m2 section of the pond was directed through the biofilter's base. Air was pumped through the filter to supply oxygen to the methanotrophs. The filter's maximum CH4 removal rate was 16gm−3h−1 (or 53μgg−1h−1), which is high compared with literature landfill soil oxidation rates (typically <1 to 40μgg−1h−1). At the trial's conclusion, the filter experienced acid accumulation, due to oxidation of H2S in the inlet biogas (evidenced by low pH [3.9] and high sulphate-S [1079mg−1kg−1] at the base of the filter compared with the top [pH=4.6, sulphate-S=369mg−1kg−1]). Nonetheless, the filter's oxidation rate peaked at the end of the experiment indicating negligible H2S impact on overall performance over the 16-month period. The results showed that a 50-m3 filter would be needed to offset CH4 emissions (approximately 720gh−1) from a typical 1000-m2 dairy effluent pond. As this calculation is based on the efficiency of a single experimental filter, field testing of replicate biofilters is needed to accurately establish full-scale filter sizing. Nonetheless, this study has shown that biofilter technology is feasible to mitigate dairy effluent pond CH4 emissions. Current research is underway to make the filter more economically viable through design optimisation.