Daily Biogas Production Research Articles

Performance Evaluation and Economic Sustainability of the PAU Model Batch Type Paddy Straw Biogas Plant

This study evaluates the performance and economic viability of the Punjab Agricultural University (PAU) Model Batch Type Paddy Straw Biogas Plant in rural India, addressing critical challenges in agricultural residue management and sustainable energy production. Data collected from two plants over four months showed an average daily biogas production of 1.46 to 3.13 m3 per day, with a total gas production of 284.8 m3 in a period of four months. Plant performance correlated moderately with ambient temperature. Economic analysis revealed annual savings of Rs. 47,600 through reduced LPG use and biogas slurry sales. The study concludes that the PAU Model is technically efficient and economically viable, offering a sustainable solution for paddy straw management and rural energy security. These findings have significant implications for policymakers and rural development practitioners in promoting sustainable agriculture and renewable energy adoption in developing regions.

Impact of lowering nitrogen content in pig manure through low crude protein diets on anaerobic digestion process stability, biogas yields, and digestate composition

Lowering crude protein in pig diets can reduce nitrogen (N) excretion and alter manure characteristics. Anaerobic digestion (AD) offers potential for converting pig manure into biogas and bio-based fertilizers (i.e., digestate). However, limited research exists on the effects of N content in pig manure on AD when pigs are fed diets with varying crude protein levels. This study investigated how lowering N content in pig manure through low crude protein diets may affect AD process stability, biogas generation, and digestate properties. Manures from different dietary treatments, named as control (CON), low N (LN), and very low N (VLN), with Total Kjeldahl Nitrogen concentrations of 5.87, 5.42, and 5.15 g/L, respectively, were investigated. Daily biogas production, composition (CH4, CO2, and H2S), and digestate properties were monitored over 13 fed-batch cycles (25 ± 4 days per cycle). The experiment was conducted at 20 ± 1 °C, a condition suited for milder climate regions, using six single-stage digesters operated in sequencing fed-batch mode. Data were analyzed by ANOVA using PROC MIXED with repeated measures. Results showed that the differences in N content in pig manure due to the three dietary treatments had a limited impact on biogas generation, with specific methane yields remaining similar over time. CH4 concentrations remained stable between 60 and 65 %, ensuring high-quality biogas despite dietary variations. Differences between treatments became more pronounced with increased organic loading rates (OLRs) due to variations in the amount of volatile solids fed. AD also remained stable (Total Volatile Fatty Acids/Total Alkalinity <0.25) even at an OLR of 2.15 g of chemical oxygen demand L−1 day−1, highlighting AD's robustness at lower temperatures. Digestate samples contained essential minerals beneficial for plant growth. More research is needed to explore varied manure compositions and feeding strategies to better understand the interactions of animal nutrition with AD.

A matheuristic applied to clustering rural properties and allocating plants for biogas generation

Establishing partnerships among agro-industrial properties and selecting ideal locations for biogas plants are crucial challenges in large-scale biogas production and can influence both operational efficiency and waste management. In this context, this research proposes a new matheuristic that addresses the problems of defining a group of properties and an optimal number of groups and identifies the best allocation to the biogas plant. The group properties were defined by hierarchical and K-means cluster algorithms. The best location for the biogas plant was determined by the proposed multiobjective mathematical model. The best cluster number was decided by two strategies: (1) one that selected the closest non-dominated solutions to the ideal solution (M1) and (2) one that favored the most environmentally friendly solution (M2). The matheuristic was tested using three real databases, which yielded strategic clusters with an average daily biogas production of 544.93 m³/day (M1 and M2) for DataBase 1, 1635,156.00 m³/day (M1) and 403,497.50 m³/day (M2) for DataBase 2, and 318,662.50 m³/day (M1) and 20,479.58 m³/day (M2) for DataBase 3. This research provides an opportunity to add value to agro-industrial properties by achieving energy security and developing new business networks.

Assessing the Suitability of Animal and Food Waste Samples for Biogas Production and Fertilizer Evaluation

With increasing concerns over fossil fuel depletion and environmental pollution, research into alternative energy sources has gained significant momentum. Organic wastes, particularly from animals and food, offer a promising substrate for biogas production, providing dual benefits of energy generation and waste reduction. This study evaluates the suitability of food waste, cow regurgitates, and cow dung for biogas production through biodigestion. The objectives were to design a lab-scale biodigester, compare biomethane yields from each waste, and evaluate their effectiveness as fertilizers. The results indicate that all three samples have properties within the acceptable range for digestion. Food waste exhibited the highest methane yield with a daily biogas production of 0.4979 m³/day, corresponding to an energy content of 27,699.45 KJ/day. Cow regurgitates produced 0.2656 m³/day of biogas, yielding an energy content of 14,739.6 KJ/day. Cow dung yielded 0.3213 m³/day of biogas, translating to an energy content of 17,723.65 KJ/day. Microbial analysis indicated the presence of beneficial bacteria and fungi, such as Staphylococcus spp, Proteus vulgaris, Escherichia coli, Enterobacter aerogens, Aspergillus spp, and Mucor spp, which are advantageous for soil conditioning and nutrient cycling. The study highlights the importance of assessing physicochemical properties, nutrient content, and microbial composition to optimise biogas production and explore the potential of organic waste as a sustainable energy source and soil conditioner.

Household-scale digesters in Rwanda: Performance analysis and net-greenhouse gas effect

In view of climate change mitigation, the production of biogas through anaerobic digestion has emerged as a prominent renewable fuel source, also in developing countries. The implementation of household-scale digesters in these regions is instrumental in achieving the Sustainable Development Goal 7 of ensuring clean and affordable energy. However, a rigorous quantification of the biogas production and net-greenhouse gas effect of these household digesters, taking into account fuel use, biogas leakage and fertiliser types, is lacking. This study quantified both biogas production and net-greenhouse gas emissions, utilizing Rwanda as a reference region. Through a field survey, biogas measurements, and model simulations, the study revealed that a reference case featuring a fixed dome digester of 4 m3, fed with manure of on average 2 cows produces 0.38 m3 biogas.d−1 which meets 65% of the cooking need of an average family of 4 adults and 2 children. The addition of a toilet to the household-scale digester increased the daily biogas production by 16%. Conversely, the use of a bare soil floor in the cow shed results in a 28% reduction in biogas production, emphasizing the recommendation for a concrete floor. Net-greenhouse gas emissions from a household-scale digester, including an estimated 9% leak percentage, result in a reduction of 2.4 tCO2,eq.year−1 per household compared to wood-only cooking. Besides, using the digestate as a fertiliser further enhances the reduction to a total of 2.5 tCO2,eq.year−1. The main opportunities for minimizing emissions include optimizing temperature, manure flow and reducing leakages, which needs to be considered during design, operation, and policy formulation. In summary, household-scale digesters provide sustainable waste management, renewable energy, and significant greenhouse gas emission reduction, making them a promising technology for decentralized energy solutions in developing regions.

The Advantage of Citrus Residues as Feedstock for Biogas Production: A Two-Stage Anaerobic Digestion System

Anaerobic digestion (AD) is an important step in waste recovery. In Colombia, the production of citrus food significantly contributes to environmental impact via waste generation. In 2021, the waste produced, specifically citrus rind, amounted to 725,035 tons/year. During degradation, wastes generate leachate and greenhouse gases (GHGs), which negatively impact water sources (leachate), soil, and human and animal health. This article describes the design of a two-phase biodigestion system for the degradation of organic matter and biogas production. The system uses citrus waste to produce biogas with neutral emissions. The biodigestion process begins with the stabilization of the methanogenesis reactor (UASB), which takes approximately 19 days. During this period, the biogas produced contains approximately 60% methane by volume. Subsequently, the packed bed reactor operates for 7 days, where hydrolytic and acetogenic bacteria decompose the citrus waste, leading to the production and accumulation of volatile fatty acids. The final step involves combining the two phases for 5 days, resulting in a daily biogas production ranging from 700 to 1100 mL. Of this biogas, 54.90% is methane (CH4) with a yield of 0.51 LCH4gSV−1. This study assesses the methane production capacity of citrus waste, with the process benefiting from the pH value of the leachate, enhancing its degradability. Consequently, this approach leads to a notable 27.30% reduction in solids within the digestion system. The two-phase anaerobic biodigestion system described in this article demonstrates a promising method to mitigate the environmental impact of citrus waste while concurrently producing a renewable source of energy.

Peering into a Simplified Digestor for Households: Performance, Cost and Carbon-Neutral Niche

In this study, a black-shading cylindrical water tank made of high-density polyethylene was locally manufactured as a household digestor for treating cow manure in Bangladesh. Effluent slurry instead of water was reused for manure dilution under manure-to-slurry ratios of 1:2 and 1:1, to assess this small prototype’s production efficiency and feasibility. The specific biogas production at both ratios matched well, by 0.12 m3/kg VS and 0.14 m3/kg VS, respectively, while the former slurry dilution operation outperformed in daily and accumulative biogas production by 16% and 57%, correspondingly, referring to 0.49 Nm3/d on average and 8.55 Nm3 in total, potentially meeting a 2 h household cooking energy requirement. From a nationwide viewpoint, slurry dilution was proven to be a great initiative to conserve water amounting to 50,286,751 m3 for 114,810 households of 6 person-equivalents annually, while cutting chemical costs by USD 32,720,684/yr and trimming annual greenhouse gas emission by 1.8 million tons of CO2e. This study revealed that a small prototype digestor could be an alternative energy source for cost-effective and eco-friendly household applications.

Design of a prediction model based on improved BP neural network and particle swarm optimization for more accurate budget of biogas production

In order to accurately predict the daily gas production of large and medium-sized biogas projects, the improved BP neural network algorithm was used, and the PSO algorithm was introduced to optimize the parameters. According to the anaerobic fermentation mechanism and the actual engineering operation status, a prediction model was established with temperature, daily feed volume, NH3, TS concentration and pH value as input layer nodes, and daily biogas production as output layer nodes. The 116 sets of data obtained by remote data acquisition are used as training samples and test samples of the model, and the simulation is carried out by Matlab software. The results show that the PSO-LM-BP neural network has good predictive ability for the daily gas production of biogas. The established biogas daily gas production prediction model not only converges fast but also has high accuracy.

Evaluating the Potential of Renewable Energy Sources in a Full-Scale Upflow Anaerobic Sludge Blanket Reactor Treating Municipal Wastewater in Ghana

Wastewater management remains a major challenge in developing countries due to the lack of adequate infrastructure, making the need for economically viable and efficient technologies that can be sustained by emerging economies imperative. The upflow anaerobic sludge blanket (UASB) reactor represents an efficient and low-cost technology that produces by-products from which valuable resources can be recovered. This study assessed the energy recovery potential in the form of electricity from biogas and sludge by-products produced by a full-scale UASB reactor. Biogas production rate and composition were monitored to determine the biogas energy recovery potential. Dehydrated sludge from sludge drying beds was likewise quantified and characterised for its elemental composition, immediate composition, gross calorific value and net calorific value to estimate sludge energy recovery potential. The average daily biogas production was found to be 611 ± 275 Nm3/d, with 65% methane in the biogas output. Average sludge dry matter production was determined to be 358.24 TS kg/d. The net energy recovery potential was estimated to be 534.1 MWh/yr, 36% more than the yearly energy demand (392.7 MWh/yr) of the entire plant. Conservative energy recovery at a UASB-based municipal wastewater treatment facility could serve as a self-supply energy option to support its operations.

Comparative functional microbiome profiling of various animal manures during their anaerobic digestion in biogas production processes

Anaerobic digestion (AD) for bio-methane production continues to be plagued by major problems such as acidification, ammonia inhibition, long reaction periods, and expensive biogas upgrading. In this study, the authors suggest that intrinsic microbial roles during AD have previously been understudied yet they are the basis for discovery of effective and substrate-specific strategies for biogas process improvement. A comparison of the functional microbiome profiling of fresh cow, horse, pig, and chicken manures sourced from seven farms around Gauteng in South Africa was done. Correlation of profiles of the daily and cumulative biogas and bio-methane production determined in an automatic methane potential system (AMPTS), six intermediate AD compounds (propionate, butyrate, formic acid, lactic acid, ethanol, and acetate) observed using a modular Thermo Scientific Vanquish Core high performance liquid chromatography (HPLC) system, and active microbiome observed through Illumina 16S rDNA high-throughput sequencing suggests that cow manure AD went through 2 quick and efficient phases while horse manure showed 3 phases with hydrolysis being the rate limiting step, pig manure showed 4 phases and was dominated with hydrogenotrophic methanogenesis, and chicken manure had 2 phases affected by ammonia inhibition. It was inferred from the findings, that co-digestion of the horse manure within the first 9 days with cow manure, manipulation of Methanococcus hydrogenotrophs from pig manure AD in 2 stage reactor co-digestion systems, introduction of Methanococcus-rich inoculum from a pig manure AD system (between Day 15 & Day 24) as well as trace nutrient supplementation to boost SAOB, are strategies that can improve hydrolysis & methanogenesis in horse manure AD, upgrade biogas quality from various substrates, counter ammonia inhibition in chicken manure AD as well as in other similar substrates respectively.

Assessment of the Potential for Greenhouse Gas Emission Mitigation by the Methanization of Slaughterhouse Waste in the District of Abidjan (Côte d'Ivoire)

Abattoirs are a source of huge waste that contributes to global greenhouse gas (GHG) emissions and, thus, to global warming and climate change. This study aimed to evaluate the GHG emission mitigation potential of a biodigester to be installed at the abattoir of Port-Bouët in the District of Abidjan. Mathematical methods developed by Hashimoto, Gwogon, and Amahrouch and an empirical method were used to assess this mitigation potential. The results showed that regardless of the methods, biogas volumes increased from 2013 to 2017 and decreased in 2018. The highest daily biogas production was obtained in 2017 for all the methods. According to Hashimoto's method, the biogas volume was 564.50 m3 in a biodigester of 2792.64 m3. Gwogon's method led to a biogas volume of 724.15 m3 for a 2228.14 m3 biodigester. The calculated volume of biogas with the Amahrouch method was 557.03 m3 for a 2785.17 m3 biodigester. The empirical method showed a maximum biogas volume of 631.31 m3. The amount of CO2 avoided per kilogram of dung ranged from 41579.88 to 71561.17 kg CO2e, 41643.46 to 71670.58 kg CO2e, 41689.19 to 71749.30 kg CO2e for Gwogon, empirical and Hashimoto methods, respectively. The values ranged from 41694.30 to 71758.10 kg CO2e for the Amahrouch method. These results show a biodigester's tremendous environmental and economic potential for treating the waste of the slaughterhouse of Port-Bouët.

Assessment of the Potential for Greenhouse Gas Emission Mitigation by the Methanization of Slaughterhouse Waste in the District of Abidjan (Côte d'Ivoire)

Abattoirs are source of huge amounts of waste that contribute to global greenhouse gas (GHG) emissions and thus, to the global warming and climate change. Treating these was with biodigester technology could be a suitable alternative to GHG emission mitigation. The objective of this study is to evaluate the potential for GHG emission mitigation by a biodigester to be installed at the abattoir of Port-Bouët in the District of Abidjan as a pilot project. More specifically, it aims to: (i) estimate the daily biogas production from 2013 to 2018 according to the mathematical methods of Hashimoto, Gwogon, and Amahrouch, and an empirical method, (ii) evaluate the environmental benefits of the biodigester by estimating the avoided GHG emissions according to the methods mentioned above.The mathematical methods used are those of Hashimoto, Gwogon and Amahrouch. In addition, the empirical method was also used. The results showed that regardless of the method, the amount of biogas increased from 2013 to 2017 and decreased in 2018. The highest daily biogas productions are obtained in 2017 for all methods. Thus, the biogas volumes are 564.50 m3 in a biodigester of 2792.64 m3 according to the Hashimoto method, 724.15 m3 for the biodigester of 2228.14 m3 with the Gwogon method and 557.03 m3 for digesters of volumes 2785.17 m3 calculated with the Amahrouch method. According to the empirical method, the maximum volume of biogas is 631.31 m3. Regarding the amount of CO2 avoided per kilogram of dung, the values ranged from 41579.88 to 71561.17 kg CO2e for the Gwogon method, 41643.46 to 71670.58 kg CO2e for the empirical method, 41689.19 to 71749.30 kg CO2e for the Hashimoto method, and 41694.30 to 71758.10 kg CO2e for the Amahrouch method. These results show a great environmental and economic potential of the installation of a biodigester for the treatment of the waste of the slaughterhouse of Port-Bouët. The choice of the anaerobic digestion process was a continuous mixed biodigester where the substrate is introduced daily with liquid.

Kinetics evaluation of a pilot scale anaerobic biofilm digester treating leachate from a municipal solid waste transfer station

In this study, leachate from municipal solid waste (MSW) transfer station was treated in a pilot scale anaerobic biofilm digester (ABD) system under 30, 25, 20 and 10-day HRT. The maximum COD concentration entering the reactor was 46,944 mg/L and the reactor was under full operation for 163 days. The results showed that COD removal efficiency was above 95 % throughout the operation and measurement of the average daily biogas production yielded a value of 25 ± 1 m3/day with a composition of 57 ± 12 % methane and 26 ± 6 % carbon dioxide. In comparison to the Monod and modified Stover–Kincannon (MSK) models, the second-order Grau model presented the best fit as a substrate-removal kinetic model for this ABD system with its R2, 0.999; while the MSK model for gas generation was proven to be a better fit than the Van der Meer and Heertjes model in predicting the amount of biogas and methane gas produced from leachate treatment via a pilot scale ABD.

A rumen based anaerobic digestion approach for lignocellulosic biomass using barley straw as feedstock

The use of rumen-based anaerobic digestion (RUBAD) has been shown to have a high rate of biogas production and can lead to a lower retention time to digest lignocellulose biomass. Albeit the use of rumen fluid in anaerobic digestion is proven to increase the rate of digestion, there is a lack of literature focused on finding the optimal organic loading of barley straw biomass when using rumen fluid as an inoculum. Therefore, this study aimed to use rumen fluid as an inoculum to test different organic loadings (OLs) of barley straw on biogas production in batch mode and using a locally designed semi-continuous rumen digester. Batch digestions in 120 mL reactor volume were carried out in triplicates to test the effect of different concentrations of barley straw ranging between 2.03 gVS/L and 24.41 gVS/L. The locally designed digester functioned like the rumen simulation technique (RUSITEC) system with a total volume of 2 L inoculum. It was fed daily with 20 g (wet weight) barley straw contained in a nylon bag (20 µm pore size) to determine the daily biogas production. Results from the batch experiment showed the biogas yield increased with an increase in organic loading (OL). Most of the OLs have a biogas yield between 250 mL/gVSadded and 270 mL/gVSadded with a methane content of 22%. The OL of 16.24 gVS/L had the highest biogas yield of 269 ± 2 NmL/gVSadded while a further increase in OL to 24.41 gVS/L led to a 19% decrease in biogas yield (226 NmL/gVS added). The designed rumen reactor had a daily biogas production of 12.63 ml/gVS/day and had a stable pH between 6.8 and 7.4 for 15 days. However, only 37.74% and 48.40% of the total solids were digested after two days of solid retention time. More than half of the barley straw feedstock remained undigested, and therefore, would require a longer retention time to complete the digestion. This study demonstrates the importance of finding the optimal organic load for different feedstocks and led to a 43.78% increase in biogas yield under the same conditions. The use of rumen fluid as inoculum can significantly lower the volume of digesters required and lower the retention times for biogas production vital to the anaerobic digestion industry.

Determining the appropriate mixing ratio in a multi-substrate anaerobic digestion of organic solid wastes employing Taguchi method.

The current research proposed a method for optimally combining feed input ratios in order to improve the quantity and quality of daily biogas production through optimizing the variable response level in the Taguchi method. The anaerobic digestion (AD) process of an existing plant in Iran was simulated through a set of two-stage pilot reactors under mesophilic temperature conditions in order to achieve optimal operational performance. Three common substrates (organic fraction of municipal solid wastes, fruit and vegetable wastes, and horse manure) along with two recirculated materials; the post-digestion sludge and the secondary digester slurry, were investigated in 16 experimental runs based on four different pre-surface hypotheses. Comparison of the results of daily biogas energy (J/d/g-VS) in Run#9, to which the actual yield of hydrogen sulfide was minimal in parallel to a methane yield above 100 mL/g-VS, with the result of the optimal run with the ratios provided by the model, showed that the daily biogas energy was improved by 50% comparing to the control Run that had similar conditions to which was being applied in the full-scale existing AD plant.

Biogas Production Potential of Thermophilic Anaerobic Biodegradation of Organic Waste by a Microbial Consortium Identified with Metagenomics.

Anaerobic digestion (AD) is a widespread biological process treating organic waste for green energy production. In this study, wheat straw and corn stalks without any harsh preliminary treatment were collected as a renewable source to be employed in a laboratory-scale digester to produce biogas/biomethane. Processes parameters of temperature, pH, total solids, volatile solid, concentration of volatile fatty acids (VFA), and cellulose concentration, were followed. The volume of biogas produced was measured. The impact of organic loading was stated, showing that the process at 55 °C tolerated a higher substrate load, up to 45 g/L. Further substrate increase did not lead to biogas accumulation increase, probably due to inhibition or mass transfer limitations. After a 12-day anaerobic digestion process, cumulative volumes of biogas yields were 4.78 L for 1 L of the bioreactor working volume with substrate loading 30 g/L of wheat straw, 7.39 L for 40 g/L and 8.22 L for 45 g/L. The degree of biodegradation was calculated to be 68.9%, 74% and 72%, respectively. A fast, effective process for biogas production was developed from native wheat straw, with the highest quantity of daily biogas production occurring between day 2 and day 5. Biomethane concentration in the biogas was 60%. An analysis of bacterial diversity by metagenomics revealed that more than one third of bacteria belonged to class Clostridia (32.9%), followed by Bacteroidia (21.5%), Betaproteobacteria (11.2%), Gammaproteobacteria (6.1%), and Alphaproteobacteria (5%). The most prominent genera among them were Proteiniphilum, Proteiniborus, and Pseudomonas. Archaeal share was 1.37% of the microflora in the thermophilic bioreactor, as the genera Methanocorpusculum, Methanobacterium, Methanomassiliicoccus, Methanoculleus, and Methanosarcina were the most abundant. A knowledge of the microbiome residing in the anaerobic digester can be further used for the development of more effective processes in conjunction with theidentified consortium.

Novel seedling substrate made by different types of biogas residues: Feasibility, carbon emission reduction and economic benefit potential

High-value utilization of biogas residue is essential to drive the development of the biogas industry. This study investigated the feasibility of total or partial replacement for peat (100%, 75%, 50%, 25% and 0%) by corn straw biogas residue and dairy manure biogas residue in growth media for tomato and pepper seedlings. The experiment was arranged in a completely-randomized design, tomato and pepper seeds were sown into each media and grown under commercial nursery conditions until they reached commercial transplant size. The results showed that growth of tomato and pepper was reduced in media containing corn straw biogas residue. However, tomato and pepper seedlings growing in a media of 50% dairy manure biogas residue were considered to be the most satisfactory. The results of the bacterial community analysis showed that the highest abundance of Anaerolineaceae was found in CS100 that meaning immaturity. Furthermore, for a biogas plant with a daily biogas production of 10,000 m3, biogas energy utilization and biogas residue substitution for peat could reduce 439,437 kg/year of CO2 equivalent emissions and arouse 3300,000￥benefit per year by replacing peat. Thus, partial replacement of peat by dairy manure biogas residue as a growth media could be promoted for its wide environmental and economic benefits.

Roadmap from Microbial Communities to Individuality Modeling for Anaerobic Digestion of Sewage Sludge.

Biological models describing anaerobic digestion (AD) of sewage sludge have been widely applied to test various control and operation strategies. Anaerobic digestion model 1 (ADM1) provides a generic platform that includes the main processes of AD, excluding homoacetogenesis and the microbial structure. Homoacetogenic bacteria have been identified as important competitors for hydrogen consumption and acetate production. Although recent advances in meta-omics techniques have improved our characterization of AD microbial communities, conventional models treat functional groups as homogeneous and overlook the physiology and behavior of microbial individuality, limiting insights into mechanisms governing process performance. A novel microbial individuality model (MIM) that integrates kinetics, energetics, and agent-based modeling to describe a microbiome's behavior as heterogenic populations, including homoacetogenesis, was developed. The MIM was validated with two datasets from previous studies through daily biogas production, methane content, compound concentrations, and microbial relative abundance changes. The MIM identified the emergence of Methanosaeta at low concentrations of acetate. Moreover, this simulation supports experimental studies confirming that the overlooked homoacetogenesis is an important hydrogen sink in AD. Validated MIMs are expected to provide insights into syntrophic and competitive interactions among microbiomes in AD systems while testing different operational parameters in a virtual environment. The MIM offers a methodological framework to other biological treatment systems and their microbial community dynamics.

Start-up of co-digestion of poultry litter and wheat straw in anaerobic sequencing batch reactor by gradually increasing organic loading rate: Methane production and microbial community analysis

Anaerobic co-digestion (ACoD) of poultry litter (PL) and wheat straw (WS) in an anaerobic sequencing batch reactor (ASBR) for continuous bio-energy generation was started up for the first time by gradually increasing the organic loading rate (OLR). A steady-state was reached with a daily biogas production of (13.06 ± 0.21) L and methane content of (54.38 ± 0.53) %. The subsequent regular operation achieved a daily methane yield of (100.41–188.65) mL CH4/g VS added and a total chemical oxygen demand (tCOD) removal rate of (70.3–85.9) % in the effluent under different operating parameters. The overall microbial community became more uniform, and the dominant aceticlastic methanogen of Methanosaeta was enriched after the start-up. While the microbial community was largely stable in the overall structure since the regular operation. Therefore, the start-up of the ACoD of PL and WS was successful with stable and continuous methane production.

Modeling Anaerobic Co-Digestion of Corn Stover Hydrochar and Food Waste for Sustainable Biogas Production

Despite the importance of the biodegradability of lignocellulose biomass, few studies have evaluated the lignocellulose biomass digestion kinetics and modeling of the process. Anaerobic digestion (AD) is a mature energy production technique in which lignocellulose biomass is converted into biogas. However, using different organic waste fractions in AD plants is challenging. In this study, lignocellulose biomass (corn stover hydrochar) obtained from hydrothermal carbonization at a temperature, residential time, and biomass/water ratio of 215 °C, 45 min, and 0.115, respectively, was added to the bioreactor as a substrate inoculated with food waste and cow dung to generate biogas. A state–space AD model containing one algebraic equation and two differential equations was constructed. All the parameters used in the model were dependent on the AD process conditions. An adaptive identifier system was developed to automatically estimate parameter values from input and output data. This made it possible to operate the system under different conditions. Daily cumulative biogas production was predicted using the model, and goodness-of-fit analysis indicated that the predicted biogas production values had accuracies of &gt;90% during both model construction and validation. Future work will focus on the application of modeling predictive control into an AD system that would comprise both models and parameters estimation.