Biogas Quality Research Articles

Exploring biogas production from Nile perch (Lates niloticus) fish byproducts

Biogas, a renewable energy source, has the potential to reduce reliance on fossil fuels while addressing waste management issues. The current study explored biogas production from various parts of fish waste fractions including head, skin, offal, and skeleton, and their mixtures through anaerobic digestion. The biogas quantity and methane content were measured using the water displacement method. Results revealed the biogas yield in the 858.33–2381.67 mL range, with methane content ranging from 35 to 55%. The highest biogas yield of 2381.67 mL was obtained from a mixture of fish wastes, followed by 1390 mL from the head, 1110 mL from the skin, 895 mL from the offal, and 858.33 mL from the skeleton. The highest biogas quality of 55% CH4 was achieved from the head, followed by a mixture of fish wastes and skin, 49%, skeleton, 41%, and offal, 35% methane. The fish waste, head and skin gave a promising quantity of biogas with the recommended methane content of 45–75%. Further studies are suggested on the co-digestion of fish waste with other organic wastes, including seeding the fish waste with animal droppings.

Evaluation of additive effecton anaerobic sewage sludge digestion

An additive based on iron oxides was applied to reduce the amount of produced sludge and to increase the production and quality of biogas. The C/N ratio was 11.0–11.3 and the pH of the sludge mixture was 7.3 before the anaerobic digestion. The determined optimal dose of the additive was 0.35 g/g of sludge dry matter over 20 days. This allowed a reduction in the sludge retention time up to 6–11 days. Consequently, maximum biogas production was reached on average 1.6 times faster, volatile solids degradation increased by 56.7%, biogas production increased by 75%, specific biogas production increased by 11.5%, and methane concentration in the biogas increased by 8.4%–18.2%. When the additive was applied, the quantity of phosphate phosphorus in the supernatant was reduced by up to 19%, and hydrogen sulfide reduction efficiency in the biogas ranged between 55% and 62%. In sludge treatment facilities, using an iron oxide-based additive could reduce the dewatering and drying costs for digested sludge by up to 35% .

Strategi Pemberdayaan Petenak melalui Program Pemanfaatan Biogas dalam Mewujudkan Desa Mandiri Energi di Kecamatan Musuk Kabupaten Boyolali

ABSTRACT The research aims to identify strategies for empowering farmers through biogas utilization programs in realizing Energy Independent Villages. This research was carried out in Sruni Village, Musuk District, Boyolali Regency, in March-April 2024. The method is a survey, the data collection technique in this study uses the Participatory Rural Appraisal (PRA) technique. Data from this study was collected through observation, interviews, and Focus Group Discussions (FGD). The sampling of this study was determined by a census of 45 people. The research data obtained was analyzed using SWOT analysis. The strength factors in this development program are the economic value of biogas is higher than other fuels, the value of biogas benefits is higher, the role of biogas in the value of environmental pollution The role of the government in the development of biogas. The weak factors in this business are the installation of biogas pipes that are easily clogged, and the maintenance of livestock is part-time. The opportunity factor of this program is to become a place of education and encourage the progress of the livestock sector. Threat factors such as perishable biogas installations and high gas pressure temperatures can cause explosions. The empowerment strategy of livestock farmer groups in Sruni Village, Musuk District, Boyolali Regency includes efforts to develop the creative economy, efforts to improve the quality of biogas, efforts to develop biogas installation technology, efforts to strengthen farmer members with groups, efforts to improve livestock business management, efforts to rehabilitate biogas as alternative energy. Keywords: biogas, energy independent villages, focus group discussion (FGD), participatory rural appraisal (PRA), empowerment strategy.

Enhanced propionate degradation and CO2 electromethanogenesis in an up-flow dual-chamber electrocatalytic anaerobic bioreactor (UF-DC-EAB): Leveraging DIET-mediated syntrophy for microbial stability.

Anaerobic digestion faces numerous challenges, including high CO2 content in biogas and volatile fatty acids (such as propionate) accumulation in digestate. To address these issues, an up-flow dual-chamber electrocatalytic anaerobic bioreactor (UF-DC-EAB) was developed to enhance propionate degradation through microbial symbiosis while improving biogas quality via CO2 electromethanogenesis. Under the extreme conditions with propionate as the primary carbon source at 6-h HRT, the UF-DC-EAB achieved a propionate removal efficiency of 72.1 ± 9.4 % and a faradaic efficiency of 25.5 ± 5.1 %. Microbial community analysis revealed an enrichment of acetoclastic methanogens (Methanosarcinales, 5.4 %) and syntrophic propionate-oxidizing bacteria (Syntrophobacterales, 13.9 %) in the anode, which facilitated propionate degradation. In the cathode, hydrogenotrophic methanogens (Methanobacterium, 13.6 %) and electroactive bacteria (Geobacter, 6.2 %) were predominant, further promoting CO2 electromethanogenesis and biogas upgrading. Co-occurrence network and structural equation modeling indicated that the electrocatalytic regulation roused the intrinsic capability of the microbial community to oxidize propionate and provoked the occurrence of direct interspecies electron transfer (DIET) among the enriched functional microorganisms, by regulating the synthesis of key molecules like F420 and cytochrome c in response to propionate-induced changes. The DIET-mediated syntropy increased the net energy output by 212.5 %. This study presents a novel electrochemical system combining CO2 electromethanogenesis with propionate-rich digestate degradation, offering an efficient approach for anaerobic post-treatment.

The effects of influent 5-Deoxystrigol concentrations on integral biogas upgrading and nutrient removal by different algal-fungal-bacterial consortium

The low quality of biogas and the difficulties in treating biogas slurry are important bottlenecks that limit the development of the fermentation industry. The effects of 5-deoxystrigol (5DS) on the growth rate, daily productivity, and photosynthetic performance of different algal-fungal-bacterial consortia were investigated, and the auxiliary activities of endophytic bacteria (S395–2), Ganoderma lucidum (G. lucidum), Bacillus licheniformis (B. licheniformis), and activated sludge in these systems were examined. The consortium Chlorella vulgaris (C. vulgaris) + G. lucidum + S395–2 was found to be the most effective combination for both biogas upgrading and nutrient removal. Removal efficiencies of chemical oxygen demand (COD), total nitrogen (TN), and total phosphorous (TP) were approximately 82.94 ± 7.88 %, 81.36 ± 7.79 %, and 83.27 ± 8.09 %, respectively, and the CO2 removal efficiency was observed to be about 69.89 ± 6.57 % at the optimum 5DS concentration of 10−11 M. On day 7 of the treatment, the CH4 content was elevated from 66.07 ± 4.84 % to 86.24 ± 8.44 %. The effect of 5DS treatments in different algal-fungal-bacterial consortia was positive in terms of growth performance and photosynthetic rate. The present study provides a framework for efficient biogas upgrading and nutrient removal by the three-phase symbionts.

A preliminary report of integrating sheep farming in combination with adopting biogas technology in organic rice farming systems in upland areas in Indonesia

This study aims to understand the preliminary results of integrating sheep farming in combination with adopting biogas technology in organic rice farming (ORF) systems in upland areas. The research was conducted in upland areas in Grabag Subdistrict Magelang Regency, Central Java Province (UPL1) and Kertasari Subdistrict, Tasikmalaya Regency, West Java Province (UPL2), Indonesia. At each upland area, a demo plot with a 17 m3 digester has been established, and 120 sheep were introduced. A combination of sheep and beef cattle manure was used as a biogas substrate. The soil sample of one and three-year conversion of ORF was collected, and macro and micro minerals were analyzed. The biogas quality was analyzed, including dry matter (DM), nitrogen (N), carbon (C) and nitrogen-ammonia (N-NH3). The greenhouse (GHG) emissions, including methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O), were measured. The results indicated that C-organic content at three-year conversions of ORF in UPL1 was much lower (P<0.05) than the one-year conversion. The average CH4, CO2, and N2O contents in UPL1 were 661, 477.3, and 0.16 mg/m2/day, respectively. The average CH4, CO2, and N2O contents in UPL2 were 3328, 3038 and 2.42 mg/m2/day, respectively. In UPL1, the proportion of CH4 was 52.5 %, CO2 was 47.4 %, and N2O was 0.01 % while the proportion of CH4 was 57.9 %, CO2 was 42.0 %, and N2O was 0.01 % in UPL2. To conclude, integrating sheep farming in combination with adopting biogas technology in the ORF system improves manure management and provides organic fertilizer, which subsequently reduces the use of artificial fertilizer and avoids GHG emissions.v

Sewage sludge thermal hydrolysis impact on the quality of biogas in anaerobic digestion process – siloxanes and VOCs studies

This paper presents the results of a study of biogas from the anaerobic digestion (AD) process of municipal sewage sludge (SS) under 43–48oC temperature conditions, using the example of a wastewater treatment plant (WWTP) in Tarnów (Poland). In the case in question, the AD of SS is preceded by a 165oC thermal hydrolysis process (THP) using Cambi THP® technology. The study of biogas concerned the basic parameters: temperature, relative humidity, content of CH4, CO2, O2, H2, N2, H2S, CO.Similar studies can be found in the literature, but they concern classical methane fermentation without considering the THP process. The present study comprehensively describes the relationship between the THP process and AD and the quality of biogas. The content of siloxanes and volatile organic compounds (VOCs) in biogas was also examined, including concentrations of Tetramethylsilane, Trimethylsilanol, L2, D3, L3, D4, L4, D5, D6, as well as toluene, benzene, xylenes and other VOCs. The results showed high concentrations of these compounds in raw biogas up to 42 mg/Nm3 in total siloxanes and 15.8 mg/Nm3 in total silicon, as well as the efficiency of biogas purification in an activated carbon filter with results of total siloxanes <0.31 mg/Nm3 and total silicon <0.11 mg/Nm3.

Biochars from waste as an additive material in anaerobic co-digestion: Characterization and application in batch and semi-continuous systems

The conversion of organic waste into energy through anaerobic digestion (AD) is a profitable and environmentally friendly strategy. Enhancing the process is crucial for optimizing and maximizing biogas and methane production. To achieve this, various strategies can be employed, such as anaerobic co-digestion (co-AD) and the use of biochar. Biochar aids in process stability, provides buffering capacity, mitigates inhibitory toxins, immobilizes microorganisms, facilitates microbial colonization, and accelerates electron transfer between microorganisms. This study aimed to produce biochar from different wastes and pyrolysis temperatures and to investigate its use as an additive material in the co-AD of fruit and vegetable waste (FVW) and laying chicken manure (LCM) in batch and semi-continuous systems. Thermogravimetric analysis (TGA) and differential scanning calorimetry were performed to determine the pyrolysis temperature for biochar production, defining temperatures of 450 and 550 °C. A biochemical methane potential (BMP) test was conducted in 120 mL reactors (working volume) with the addition of 10 g/L of biochar from FVW, LCM, and wood pruning waste (WPW). WPW450 biochar showed the highest fixed carbon content, rough surface, and deep porous structure, factors that contributed to a 28 % increase in methane production compared to the control. Semi-continuous tests were conducted in 50 L reactors (working volume) using a reduced dosage (1 g/L) of WPW450 biochar, providing process stability and better biogas quality, resulting in a 31 % increase in methane production. The reduction in biochar dosage did not negatively impact the semi-continuous system, which showed a 74 % higher methane yield compared to the batch system. The results of this study highlight the importance of biochar addition to increase methane production in the co-AD of FVW and LCM at different scales, as well as the study of different biomasses and temperatures for biochar production.

Integrating Anaerobic Digestion With Struvite Production for Enhanced Nutrient Recovery, Pathogen Reduction, and Circularity in Manure Management

ABSTRACTIntroductionAnaerobic digestion (AD) is essential for manure management, generating biogas and nutrient‐rich digestate for organic fertilizer. However, improper digestate use can pose environmental risks. Recovering struvite, a magnesium ammonium phosphate (MAP) compound, from digestate provides a sustainable, controlled‐release fertilizer, supporting a circular economy in agriculture.Materials and MethodsThe study employed a two‐stage (liquid–solid) AD process using poultry, dairy, and swine manures, along with wasted corn silage. Digestates were sampled for physicochemical and biogas quality analyses, with feedstocks categorized into D1 and D2, and a composite (D3) formed for struvite characterization. Microbial populations were enumerated on selective media, and struvite mineral content was analysed via argon plasma emission spectrometry.ResultsThe digesters processing feedstock mixtures D1 and D2 achieved specific methane yields of 1.26 L/g CODs fed and 1.49 L/g CODs fed, with cumulative biogas production of 374 and 369 L, respectively, over four 77‐day cycles. The two‐stage AD process significantly reduced antibiotic‐resistant, Enterobacteriaceae and Enterococcus spp. Total ammoniacal nitrogen (TAN) recovery rates were high at 98%–99%, with a consistent struvite crystal mass of 0.67 g/10 mL, indicating the efficiency of this integrated process. The agronomic value of struvite was determined, indicating its potential utility as a fertilizer, and scanning electron microscopy analysis revealed diverse crystal structures, warranting further investigation into their implications for usage and storage.ConclusionThe results suggests that the two‐stage AD process efficiently transforms organic waste into high‐quality biogas, reduces antibiotic‐resistant bacteria, and facilitates nutrient recovery through struvite precipitation. This approach supports co‐digestion of multi‐substrates and promotes circular economy principles, with potassium or sodium phosphate enhancing struvite recovery for sustainable agriculture.

Goat Manure Potential as a Substrate for Biomethane Production—An Experiment for Photofermentation

This article presents the current state of biogas (biomethane) production technology—an example of the use of goat manure in terms of photofermentation efficiency. The theoretical and experimental potential of biomethane using biodegradability for anaerobic fermentation of goat manure was indicated. Goat manure was tested for its elemental composition to determine the suitability of this raw material for biogas production. The quality of biogas produced under atmospheric conditions from goat manure placed in a reactor (photodigester) was assessed. An attempt was made to determine the process conditions for immobilization on a goat manure bed (depending on the research material collected), which allows for demonstrating the activity of the fermentation bacterial flora, thus influencing the amount of biogas (biomethane) produced in the reactor. A mechanism for the photofermentation process involving the production of biomethane was developed. The novelty of this article is the development of the use of goat manure in an innovative way, pointing to the development of the biomethane industry. When comparing goat manure, active group (compact bed), it should be noted that K 3.132%, Na 0.266%, Ca 1.909% and Mg 0.993% are lower values compared to the material with values of K 3.397%, Na 0.284%, Ca 1.813% and Mg 0.990% which are higher. This is undoubtedly due to the presence of nutrients in the deposit that support the biomethane production process. The active group (compact bed) material A shows a dynamic increase in biomethane production with lower nutrient values. However, material B, having a higher percentage of ingredients, shows stabilization of biomethane production after the sixth month of the process. Technological trends and future prospects for the biomethane sector were initiated.

H2S mitigation for biogas upgrading in a full-scale anaerobic digestion process by using artificial neural network modeling

Biogas production by anaerobic digestion (AD) has emerged as a prominent bio-renewable energy source in recent years. However, the process also produces undesirable by-products, including H2S, thereby negatively impacting the biogas quality. This study focused on mitigating H2S in a full-scale AD located at a wastewater treatment plant (WWTP) by controlling the internal operational parameters by using an artificial neural network (ANN) model. Data from 54 days of AD operation were used to train and validate a structured ANN with a 5-3-1 topology. To minimize the H2S content, optimum values for dry solid (DS), volatile solid (VS), pH, temperature, and primary sludge fraction (PS) were determined to be 6.2 %, 63 %, 7.7, 35.6 °C, and 67.6 %, respectively, using the particle swarm optimization (PSO) algorithm. This optimization indicated a 49 % reduction in the average H2S concentration, from 6117 ppm to 3107 ppm. The analysis of relative importance (RI) showed that the pH (RI = −29.5) and PS (RI = −28.7) were the most critical factors affecting biogas quality. Additionally, several solutions derived from the optimization results were practically implemented in the Qom WWTP to achieve optimal conditions, and the outcomes were discussed.

External ceramic membrane contactor for in-situ H2 assisted biogas upgrading

Biological H2-assisted biogas upgrading has gained significant attention as an environmentally friendly substitute to common physico-chemical upgrading techniques, but is largely limited by the low solubility of H2. This study evaluated the design of a ceramic membrane contactor module for H2 injection. H2 dissolution was maintained at high efficiency by controlling gas supply and sludge recirculation rate, achieving a biogas quality of average 98.8% CH4 during the stable operation phase with a 108% increase in the CH4 production rate. This also outperforms conventional H2 injection using diffuser sparging which could only achieve a biogas quality of 84% CH4 content. Microbial community analysis found high Methanobacterium spp. abundance within the archaea at 95.2% at the end of the operation, allowing the dominance of the hydrogenotrophic methanogenesis pathway for high upgrading efficiencies. The system is a high-performance external membrane connector module coupled to common anaerobic digestion systems for biogas upgrading.

Enhancing biogas quality: An experimental investigation of CO2 and H2S removal techniques

Enhancing biogas quality: An experimental investigation of CO2 and H2S removal techniques

Fuzzy-decision tree modeling for H2S production management in an industrial-scale anaerobic digestion process

H2S is a byproduct in anaerobic digesters (ADs), causing significant challenges due to its negative impact on biogas quality and equipment corrosion. As a solution, previous researchers developed complex mechanistic models that are computationally expensive due to solving equations with many variables. These models were only tested within normal H2S ranges. This research introduces a novel hybrid fuzzy-decision tree (F-DT) model to predict H2S production from primary/secondary sludge ratio (P/S), dry solids (DS), and volatile solid (VS) reduction parameters in the Qom wastewater treatment plant in Iran. Notably, the H2S concentrations in this facility consistently surpass the acceptable thresholds reaching levels as high as 6500 ppm, in contrast to the designed accepted limit of 3000 ppm. The process involved collecting and pre-processing data, creating a decision tree classifier for rule generation, developing a fuzzy model suited for complex systems like AD, and optimizing it with a genetic algorithm. The analysis of the final model revealed that the P/S ratio significantly influences elevated H2S levels, indicating that maintaining a P/S ratio > 1.2 holds promise as an effective strategy. The model is both simple and interpretable, with decent accuracy in predicting H2S compared to previous models. This study not only introduces a useful method for optimizing industrial-scale ADs, but also aims to uncover the reasons behind high H2S levels.

The Impact of Biostarter Em-4 and Buffalo Feces on The Quality of Biogas Created from Sugarcane Bagasse Fiber

Energy is one of the most important needs in life. That’s because all human activities require energy to live. New breakthroughs need to be made to overcome the energy crisis, one of which is biogas by utilizing waste. Waste that can be used is sugarcane bagasse and buffalo feces, which have the potential to produce biogas. The purpose of this study was to determine the effect of a mixture of bagasse fiber and buffalo manure with the addition of EM-4 biostarter and without EM-4 biostarter that has the potential to produce biogas. Variations in the composition of AT and buffalo feces in this study were 50%SB: 50%BF, 40%SB:60%BF and 30%SB:70%BF without using the EM-4 biostarter. batch-type digester reactor type. The method used is the experimental method. The results showed that biogas production from the composition of a mixture of bagasse fiber with buffalo feces has an influence. Where the more buffalo feces added, the more gas produced. Then for the biogas production process using EM-4 biostarter and without EM-4 biostarter, it was found that the best in producing gas was using EM-4 biostarter, this was due to the function of biostarter which accelerates biogas fermentation so that the influence on biogas production was to use EM-4 biostarter

Methane production from sugarcane vinasse: The alkalinizing potential of fermentative-sulfidogenic processes in two-stage anaerobic digestion

The two-stage anaerobic digestion (2st-AD) of sugarcane vinasse is widely studied and well-known for improving the energy recovery potential in sugarcane biorefineries. Maintaining enhanced substrate acidification in a separate (first stage) reactor directly improves the performance of methanogenesis (second stage). However, problems derived from the presence of sulfate (SO42−) and the subsequent sulfide formation in the second stage are not prevented in conventional 2st-AD systems. In addition, high costs related to reactor alkalinization still represent significant drawbacks in that configuration. The energy recovery potential via methanogenesis was assessed from acidified sugarcane vinasse samples collected from different dark fermentative systems, namely: V1 (subjected to NaOH+NaHCO3 dosing), V2 (subjected to NaOH dosing) and V3 (subjected to no pH control). Despite the harmfulness of sulfide, the enhanced production of acetate from the incomplete oxidation of organic matter in sulfidogenesis can benefit methanogens. The highest methane yield (296.3 NmL-CH4 g-COD−1) and global energy recovery potential (354,603 GWh per season) were obtained from the lactate and SO42−rich vinasse (V2). Nevertheless, from a technological perspective, the methanogenesis of vinasses subjected to the fermentative-sulfidogenic process (V1) provided a higher quality biogas due to a higher calorific power (26.4-27.0 MJ Nm−3) and decreased H2S content in the biogas. Finally, the fermentative-sulfidogenic process as an alkalinizing strategy was demonstrated to be the best economic approach for scaling up the 2st-AD of sugarcane vinasse, overcoming the main economic drawback of this configuration.

Fulvic acid-mediated efficient anaerobic digestion for kitchen wastewater: Electrochemical and biochemical mechanisms

Fulvic acid, prevalent in humus derived from the anaerobic digestion of kitchen wastewater, is crucial in organic matter transformation. However, its effects and underlying mechanisms remain unclear. In this study, the fate of anaerobic digestion of artificial and kitchen wastewater with different fulvic acid contents was investigated. The results showed that 125 mg/L fulvic acid resulted in a 64.02 and 51.72 % increase in methane production in synthetic and kitchen wastewater, respectively. Fulvic acid acted as an electron mediator and increased substrate oxidation by boosting NAD and ATP levels, thereby increasing microbial metabolic rates and ensuring an adequate substrate for methane generation. Isotope analysis suggested that fulvic acid boosts the conversion of volatile fatty acids to methane via the interspecies electron transfer pathway. Gene expression analysis revealed that cytochrome c, FAD, and other electron transport coenzymes were upregulated by fulvic acid, thereby enhancing substrate utilisation and biogas quality. Fulvic acid presented a dual stimulatory and inhibitory effect on anaerobic digestion, with concentrations over 125 mg/L diminishing its positive impact. This dual effect may stem from the properties and concentrations of fulvic acid. This study revealed the effect mechanism of fulvic acid and provided insights into the humus performance in anaerobic digestion

The feasibility of using biogas generated from livestock manure as an alternative energy source: A South African perspective

Electricity usage has risen tremendously over the years, as has its price. This resulted in an increase in the quest for less expensive, viable, and ecologically acceptable means of producing energy for electricity. Currently, the primary source of power in South Africa is sourced from fossil fuels, which have negative environmental consequences. The use of biogas as an alternative can mitigate the impacts of using fossil fuels to generate power. This study has examined the availability and accessibility of waste that may be utilized to generate biogas using common South African livestock excrement. A typical South African home uses 31 kWh of power daily, which equates to 111.6 MJ of energy. According to calculations, about 30 m3 of biogas is needed to produce enough energy to power a household. For the generation of mono-digestion biogas, 12 beef cows, 8 dairy cows, 3898 chickens, 156 pigs, 281 sheep and 300 goats would be needed to meet this need. Moreover, the livestock dung required to meet the daily requirement of 31 kWh is 713 kg for beef and dairy cows, 390 kg for chickens, 468 kg for pigs, 506 kg for sheep and 466 kg for goats. Co-digestion of various wastes is nonetheless a viable and advised method for enhancing the amount and quality of biogas.

Enhancing biogas production from palm oil mill effluent through the synergistic application of surfactants and iron supplements

In this study, the effects of various surfactants on the soluble chemical oxygen demand (COD) fraction and biogas production from palm oil mill effluent (POME) were investigated. A cationic surfactant (cetyltrimethylammonium bromide, CTAB) and a nonionic surfactant (Tween 80; TW80) were found to adsorb onto the particulate matter from POME, markedly reducing the soluble COD, unlike an anionic surfactant (sodium dodecyl sulfate, SDS). The mechanism underlying this phenomenon might be the adsolubilization of oil on particulate matter induced by the adsorbed surfactants. In terms of biogas production, 0.1 % w/v SDS and CTAB dramatically reduced the biogas yield, while 0.1 % w/v TW80 did not have this negative effect. A synergistic effect was observed when TW80 (0.1 % w/v) was combined with FeSO4 (400 mg/L), resulting in a 17 % greater biogas yield than that achieved with treatments using TW80 or FeSO4 alone. Moreover, the combination of TW80 and FeSO4 increased the biogas production rate. Surprisingly, the water-soluble iron fraction remained consistent across all treatments, suggesting that the adsorption of TW80 on particulate matter may limit micelle formation. Importantly, the proportion of methane in the generated biogas remained stable in all the treatments. Microbial community analysis revealed that the introduction of TW80 and FeSO4 had no discernible impact on the microbial community of the system. Pretreatment with TW80 and an iron supplement significantly enhanced biogas production and reduced the retention time of the anaerobic digestion (AD) system while maintaining the biogas quality and microbial community stability.

Valorisation of biogas for market development and remission of environmental nuisance in Uganda

In Uganda, biogas is a low-value product considered a pro-poor renewable energy source. Farmers with excess biogas release it into the atmosphere, contributing to global warming. This study used mixed data sources and methods to explore how biogas can be valorised to become a valued commercial energy source in Uganda and reduce greenhouse gas emissions. The results reveal the inefficiency of current biogas purification processes: the concentration of methane (CH4) in the upgraded gas was only 58 %, far below the standard specification of 98 %. The pilot production process never came close to even the lower specification level of 95 % for upgraded methane and the upper specification level of 5 % for carbon dioxide (CO2). The presence of traces of H2S, water and oxygen could lead to the corrosion of storage equipment and complicate the use of the gas. The study also found that small-scale biogas producers with excess gas have a high desire to sell it but have currently no clear idea of how to valorise it to reach the market. Our market analysis revealed three promising customer segments: bioenergy entrepreneurs, gas companies and electricity suppliers. Taken together, our findings imply that to become a commercially viable energy source, the quality of biogas needs to be improved using valorisation strategies like monitoring gas quality, shaping the market, market research and certification and controls. The national bioenergy policy could consider subsidising valorisation technologies to make them affordable for farmers and thus support a more climate-smart biogas commercialisation process.