Maximum Biogas Production Research Articles

Evaluation of activated pyrochar for boosting anaerobic digestion: Performances and microbial community

In this study, the effects of CO2-activated/non-activated pyrochars (PCs) from cornstalk, cotton straw, and rice straw on anaerobic digestion (AD) performances and microbial characteristics were investigated. The maximum biogas production rate (2.2 L/L/d) with a methane content of 73% was obtained from the AD with CO2-activated cotton straw PC. The activated PC mainly played a strengthening role in the early and middle stages of AD. Specifically, the cornstalk PC could greatly relieve acid inhibition, and cotton straw PC had a significantly positive effect on the regulation of ammonia nitrogen concentration. The rare genera like Verrucomicrobia had obvious differences among groups of AD with PCs. Regarding differential metabolites, cornstalk PC-N2 displayed a positive correlation with isoleucyl-alanine, while exhibiting a negative correlation with deoxyinosine, and the corresponding relative expression levels were + 3.0 and −2.4, respectively. Overall, gas-activated PCs could promote methane production and affect the composition of microbial community.

Investigation of methane-rich gas production from the co-bioconversion of coal and anaerobic digestion sludge

Co-bioconversion of coal and anaerobic digestion sludge is a process that involves the simultaneous treatment of coal and sludge using microbial activity to produce methane-rich gas for energy harvest. This process has the potential to provide an innovative approach to managing these two waste materials while delivering valuable products such as biogas and biofertilizers. In this study, an experimental program is designed in three batch reactor clusters in which each batch is intended to test the biogas production with various media combinations. This study’s primary goal is to understand the coal-sludge bioconversion pathway of subbituminous coal and lignite coal with different media combinations. In all batches, control reactors without coal loading were considered blank. For each batch, two sets of coal-loaded reactors with 4 g subbituminous and lignite coals were set up in duplicate with various combinations of deionized (DI) water, formation water and nutrient solution which were added to the reactors to evaluate their impacts on biogas production behaviors. The results show that co-bioconversion of coal and sludge lead to superior biogas production and methane-rich gas in lignite, subbituminous, and blank, respectively. Utilizing formation water and nutrients in the reactors reach maximum biogas production in a short period. However, the cumulative biogas production reaches maximum volume for a long duration when coal-sludge is mixed with DI water. The optimum nutrient needs to be designed based on the coal characteristic and the microbial community within the anaerobic digestion sludge to maximize methane-rich biogas production in the co-bioconversion of coal-sludge process.

Experimental evaluation on the effect of biochar addition with anaerobic digestion of the tannery wastewater to improve biogas production

Abstract The use of biochar as an additive material in various compositions to the anaerobic digestion of the tannery wastewater was investigated. Pyrolytic biochar made from Khat waste with different compositions was added to anaerobic batch digesters in laboratory-scale experiments. Biogas digesters of 500 ml volume were used to explore the effects of biochar on anaerobic digestion in the ratios of 5, 10, 15, and 20% (w/w) at constant mesophilic temperature (38 °C). The results show that for five experimental tests in digesters (D0, D1, D2, D3, and D4), which contains 0, 5, 10, 15, and 20% of biochar, the cumulative methane and biogas yields were, respectively, 17.04, 41.2, 43.8, 51.6, 48.6% and 150, 520, 680, 760, 690ml. Compared to the cumulative methane production efficiency of the digester without biochar (D0), the addition of 5, 10, 15, and 20% biochar had more favorable effects and increased the efficiency by 58.6, 61.1, 66.98, and 64.94%, respectively. From these results, adding 15% of biochar to anaerobic digestion causes a three-fold increase in methane compared to the control and more positive effects than all other biochar compositions. According to this result, the right dose of biochar must be added to maximize biogas production.

Sustainable Biomethane Production from Sewage Sludge and Wheat Straw Co-Digestion in the Presence of Polypyrrole Fe3O4 Nanoparticles and Alkaline Pretreatment: Life Cycle Assessment Point of View

Abstract Biogas production from sewage sludge can be valued in different scenarios of energy usage such as the electricity, heating, and transportation system. Improving the energy production value is the main reason for using different ways such as alkaline pretreatment and nanoparticles (NPs). This investigation uses life cycle assessment (LCA) for evaluating the biomethane production from co-digestion of sewage sludge and wheat straw in the presence of polypyrrole Fe3O4 nanoparticles (0, 20, 40, 60, and 80 mg) and NaOH alkaline pretreatment (0 and 5 mg) at mesophilic anaerobic digestion along with optimization for sustainable biomethane production. Results indicated that retention time (RT) and NaOH concentration had a significant effect on biomethane production. But, the effect of NP concentration on biomethane production was not significant. Also, the maximum biomethane production was obtained by NP40Na0 (about 50% higher than the control). On average, adding the NaOH and NPs improved the biomethane yield by about 25–40% vs in comparison with the control. The maximum biogas production yield was related to NP40Na0 with an enhancement of about 35% in comparison with the control. On average, adding nanoparticles and NaOH alkaline pretreatment improved the biogas production by about 10–20% in comparison with the control. Sustainable biomethane production can be obtained at an NP concentration of 50.24 mg and NaOH concentration of 24.04 mg, which increased the biomethane production by about 198%, and reduced human health, ecosystem quality, climate change, resources, and economic cost by about 87, 86, 92, 95, and 87%, respectively, in comparison with the control.

Treatment of Effluent with an Anaerobic Aerobic Effluent Treatment System

Today energy and clean water is a requirement in all societies worldwide to run productive processes. This affects the natural environment negatively and requires establishing more environmentally sustainable processes to decrease dependency and preserve the natural environment.
 In this research approach a laboratory anaerobic aerobic effluent treatment system was designed, built, and started up with wastewater. After start-up the system was operated with prepared milk waste, liquid cow manure and wastewater at a hydraulic retention time of 3 days and 6 days. 
 The laboratory anaerobic aerobic system was able to degrade the chemical oxygen demand, total solids and total suspended solids of all three influent liquids up to 95% and 98% for the 3-day and 6-day hydraulic retention time.
 Maximum total solids removal was 87.89% and 92.43% for the 3-day and 6-day hydraulic retention time.
 Total suspended solids removal yielded a maximum of 99.87 and 99.93% for the 3-day and 6-day hydraulic retention time.
 The anaerobic sludge blanket reactor of the system operated at a temperature of 38°C and a pH between 7.5 and 8.2 achieved a biogas CH4 content of 65% ± 5% and a maximum total biogas production of 2.23 ml/h for the milk waste at a 3-day hydraulic retention time and a minimum biogas production of 1.36 ml/h for the waste water the 3-day and 6-day HRT respectively.
 The operation of the designed laboratory anaerobic aerobic effluent treatment system showed that it is capable of reducing the effluent loading of a variety of waste streams as well as producing biogas that can be converted into bio-energy.

Anaerobic mono and co-digestion of agro-industrial waste and municipal sewage sludge: Biogas production potential, kinetic modelling, and digestate characteristics

Lignocellulosic substrates, including wastes generated from agro-industrial activities, are bio-residues evaluated to put an end to the energy needs and sustainable waste disposal problems that the world is trying to deal with today. However, the slow rate of hydrolysis of such lignocellulosic wastes limits the biogas production efficiency with the mono-anaerobic digestion (AD) process. Therefore, anaerobic co-digestion (AnCoD) of such wastes with secondary raw materials rich in microorganisms and various nutrients, such as sewage sludge, is an economical and useful method for both enhancing biogas production and disposal of more waste. In this study, AD and AnCoD processes for biogas and methane production were investigated on okra waste (OW) and municipal sewage sludge (MSS) by using cattle manure as inoculation, which constitutes only 8% of the total working volume. Five different substrate mixing ratios (100%OW, 75%OW-25%MSS, 50%OW-50%MSS, 25%OW-75%MSS, and 100MSS%) were prepared to observe the effect of C/N ratio, maximum biogas production potential, methane content, and organic matter removal efficiency on AD and AnCoD processes. All bioreactors were operated in a batch process with 8% TS in mesophilic temperature for 25 days. The amount of biogas produced in the 100%OW experimental set for the AD process was 44% more than 100%MSS. However, the AnCoD process was more efficient than AD, and biogas and methane production increased by up to 66% and 112%, respectively, compared to the mono-substrate experimental set. The highest biogas production value was 1060 mL (375 mL/gVSremoved) with 60% methane content in the bioreactor consisting of 25%OW-75%MSS. As a result of AD and AnCoD process, soluble carbohydrate, protein and COD removal for all bioreactors were between 62% and 79%, 28%-68% and 54%-70%, respectively. The FT-IR peaks seen in digestates were consistent with the presence of functional groups formed as a result of AnCoD. Monod, Cone, Transference function, and Logistic function kinetic models were used for the estimation of cumulative biogas production efficiency. In addition, the energy potential of the methane produced as a result of the AD and AnCoD processes and the financial gain that can be obtained from its direct sale were evaluated.

Effect of chemical and biological additives on production of biogas from coffee pulp silage

Energy is the foundation of the global economy and is essential to human survival. Nevertheless, more than 60% of it comes from fossil fuels. That is not a replenished and scarce source. However, a sizable amount of organic waste is generated every minute throughout the world and can be used as a raw material to produce renewable energy. Among them, Coffee processing generates a huge amount of solid and liquid waste that is organic and can serve as raw material for biofuel production. Since coffee beans and powder are Ethiopia’s main exports, coffee pulp is easily accessible. Therefore, the main goal of this project is to convert this waste, which largely consists of organic materials, into a valuable product called Methane. The purity and yield of methane productivity are significantly influenced by the type of additives we use. This work systematically investigates the effect of chemical and biological additives on the productivity and purity of the Biogas from the coffee pulp silage in batch systems under mesophilic temperature (38 °C) for different ensiling periods and additive proportions. The chemical additives recorded the maximum biogas production (2980 ml) at an ensiling period of 40 days with high purity of about 70% biogas. The minimum Biogas was recorded at the ensiling period of 10 days by the control (T1) treatments, which was 634 ml. This work proves that biological additives produced the highest quality and quantity of Biogas from coffee silage.

Two-stage (liquid-solid) anaerobic mono-digestion of ammonia-rich chicken manure at low-temperature: Operational strategy and techno-economic assessment

This study investigated mono-digestion of ammonia-rich chicken manure (CM) in a high-solids anaerobic-digester (HSAD) at low-temperature (20±1°C) adopting the recirculation-percolation mode of operation using liquid-inoculum. HSAD was operated for about 282 days in batch-runs under different organic loading rates (4.3-8.7 gVS/L.d), total solids (65-70%) and total kjeldahl nitrogen (TKN) (23.3- 32.8 g/L) concentrations. It was noted that acclimation of the liquid inoculum to a high concentration of TKN (6.9 g/L) facilitated CM digestion, thereby reducing the start-up phase. The maximum cumulative biogas production rate and specific methane yield were found to be 20 L/d and 0.80±0.12 LCH4g/VSfed, respectively with a methane content over 60% without any signs of inhibition. Operating HSAD at low temperature prevented the accumulation of free-ammonia, which is toxic to methanogens. A techno-economic analysis was also conducted as part of this study to determine the profitability of the system and a 9-year tentative payback period was estimated.

Acclimatizing waste activated sludge in a thermophilic anaerobic fixed-bed biofilm reactor to maximize biogas production for food waste treatment at high organic loading rates

Thermophilic anaerobic digestion (TAD) provides a promising solution for sustainable high-strength waste treatment due to its enhanced methane-rich biogas recovery. However, high organic loading rates (OLR) exceeding 3.0 kgCOD/m3/day and short hydraulic retention times (HRT) below 10 days pose challenges in waste-to-energy conversion during TAD, stemming from volatile fatty acids (VFAs) accumulation and methanogenesis failure. In this study, we implemented a stepwise strategy for acclimatizing waste activated sludge (WAS) in a thermophilic anaerobic fixed-bed biofilm reactor (TA-FBBR) to optimize methanogen populations, thereby enhancing waste-to-energy efficiencies under elevated OLRs in food waste treatment. Results showed that following stepwise acclimatization, the TA-FBBR achieved stable methane production of approximately 5.8 L/L-reactor/day at an ultrahigh OLR of ∼20 kgCOD/m3/day and ∼15 kgVS/m3/day at 6-day HRT in food waste treatment. The average methane yield reached 0.45 m3/kgCODremoval, attaining the theoretical production in TAD. Moreover, VFA concentrations were stabilized below 1000 mg/L at the ultrahigh OLR under 6-day HRT, while maintaining an acetate/propionate ratio of > 1.8 and a VFA/TAK ratio of < 0.3 serving as effective indicators of system stability and methane yield potential. The microbial community analysis revealed that the WAS acclimatization strategy fostered the microbial diversity and abundance of Methanothermobacter and Methanosarcina. Methanosarcina in the biofilm were observed to be twice as abundant as Methanothermobacter, indicating a potential preference for biofilm existence among methanogens. The findings demonstrated an effective strategy, specifically the stepwise acclimatization of WAS in a thermophilic fixed-bed biofilm reactor, to enhance the food waste treatment performance at high OLRs, contributing valuable mechanistic and technical insights for future sustainable high-strength waste management.

The Potential of Recycling Used Engine Oil for Biogas Generation by Co-Digestion with Animals’ Manure: Experimental and Kinetic Study

This study investigates the potential of biogas recovery from used engine oil (UEO) by co-digestion with animals’ manure, including cow dung (CD), poultry manure (PM), and cattle manure (CM). The experimental work was carried out in anaerobic biodigesters at mesophilic conditions (37°C). Two groups of biodigesters were prepared. Each group consisted of 4 digesters. UEO was the main component in the first group of biodigesters with and without inoculum, whereby a mix of UEO and petroleum refinery oily sludge (ROS) was the component in the second group of biodigesters. The results revealed that for UEO-based biodigesters, maximum biogas production was 0.98, 1.23, 1.93, and 0 ml/g VS from UEO±CD, UEO±CM, UEO±PM, and UEO, respectively, whereby, for the UEO=ROS-based biodigesters, maximum biogas production was 3.49, 2.47, 3.64 and 2.44 ml/g VS from UEO+ROS±CD, UEO+ROS±CM, UEO+ROS±PM, and UEO+ROS, respectively. These results indicated that UEO was not feasible and efficient for biogas recovery since biogas production was very low in the first group of biodigesters compared to its recovery in the second group. A modified Gompertz model was applied to study the kinetics of the bio-digestion process. Measured and predicted values of biogas generation were fitted well with determination coefficients higher than 0.92.

An Initial Proteomic Analysis of Biogas-Related Metabolism of Euryarchaeota Consortia in Sediments from the Santiago River, México.

In this paper, sediments from the Santiago River were characterized to look for an alternative source of inoculum for biogas production. A proteomic analysis of methane-processing archaea present in these sediments was carried out. The Euryarchaeota superkingdom of archaea is responsible for methane production and methane assimilation in the environment. The Santiago River is a major river in México with great pollution and exceeded recovery capacity. Its sediments could contain nutrients and the anaerobic conditions for optimal growth of Euryarchaeota consortia. Batch bioreactor experiments were performed, and a proteomic analysis was conducted with current database information. The maximum biogas production was 266 NmL·L-1·g VS-1, with 33.34% of methane, and for proteomics, 3206 proteins were detected from 303 species of 69 genera. Most of them are metabolically versatile members of the genera Methanosarcina and Methanosarcinales, both with 934 and 260 proteins, respectively. These results showed a diverse euryarcheotic species with high potential to methane production. Although related proteins were found and could be feeding this metabolism through the methanol and acetyl-CoA pathways, the quality obtained from the biogas suggests that this metabolism is not the main one in carbon use, possibly the sum of several conditions including growth conditions and the pollution present in these sediments.

Application of multi-heteroatom doping biochar in a newly proposed mechanism of electron transfer in biogas production

Although it was suggested that adding biochar to an anaerobic reactor may aid in digestion, its function has not been formally established. It has been suggested that anaerobic digestion (AD) is dominated and participated in by direct interspecies electron transfer (DIET). This study assessed the efficiency of S-modified biochar (WPB-S) and N-modified biochar (WPB-T) using Triethylenetetramine (TETA) derived from watermelon peels biomass as an additive for the production of biogas from brown algae cystoceira myrica (C. myrica) either co-digested or individually with WPB-S or WPB-T. BET, FTIR, TGA, XRD, XPS, SEM, and EDX were used to characterize the prepared biochars. FTIR analysis confirmed the establishment of S and N groups on the surface of biochar. The modified Gompertz kinetic model fits the investigational data satisfactorily, with R2 ranging between 0.907 and 0.990. Adding WPB-S at doses of 50 mg/L to C. myrica considerably enlarged the biogas yield (623 mL/g VS) compared to all other treatments. Finally, according to RSM study, the maximum biogas production (585.53 mL/g VS) was achieved for C. myrica and WPB-S treatment after 48 days of contact time using 50 mg/L WPB-S dose. The mechanism of DIET has been studied in detail, confirming that WPB-S can support electron transfer and conversion of CO to CH4. DIET mechanism could be explained in new ways depending on the conductivity, XPS, FTIR and BET findings which confirm that S-functional groups, S% in the surface of WPB-S and smaller total pore volume are the main reason for higher biogas production.

ANAEROBIC DIGESTION OF BREWER’S SPENT GRAIN WITH BIOCHAR – BIOGAS PRODUCTION KINETICS AND PROCESS EFFICIENCY

Biochars made from brewer’s spent grain were added to the anaerobic digestion of brewer’s spent grain to enhance the methane fermentation process and improve biogas production. In research, the effect of biochars made at 300, 450, and 600 °C and doses of 1-8% added to anaerobic digestion was tested. The biochemical biogas potential tests in mesophilic conditions were performed. The tests took 28 days, the biogas yield for each reactor varied from 500-650 ml×gVS-1, and around 60% substrate degradation was obtained. For each test, the kinetics parameters using the first-order model were determined. The constant biogas production rate (k), and the biogas production rate (r) varied from 0.05-0.08 d−1, and 42-60 ml×(gVS×d)−1 respectively. Though the differences in biogas production turned out to be statistically insignificant (p&lt;0.05) due to the high disappearance in obtained data and conflicting effects, the response surface area analysis showed that biochar made at 450 °C at the share of 1-4% could be used to maximize biogas production. Nevertheless, supplementation with biochar needs to be done carefully since in many cases, a reduction in biogas production was observed

Characteristics of Biogas Production and Synergistic Effect of Primary Sludge and Food Waste Co-Digestion.

The online version contains supplementary material available at 10.1007/s12155-023-10620-8.

Thermodynamic method for analyzing and optimizing pretreatment/anaerobic digestion systems

This paper builds a quantitative thermodynamic model for the microbial hydrolysis process (MHP, which uses Caldicellulosiruptor bescii at 75°C for pre-digestion) for producing biogas from a 5-10% aqueous suspension of dairy manure (naturally buffered near pH 7.8 by ammonium bicarbonate) by anaerobic digestion with a mix of acetoclastic and syntrophic methanogenesis. Standard Gibbs energy changes were calculated for the major reactions in pre-digestion, for reactions producing H2, acetate, and CO2 in the digester, and for methanogenesis reactions in the digester. The available data limit the study to analyzing reactions in the digester to reactions of short-chain volatile fatty acids anions. Results are presented as curves of ΔrxnG (Gibbs energy change) vs. acetate concentration. The H2(aq) concentration must be above 1.2×10-9 M to get significant syntrophic methanogenesis, i.e., for ΔrxnG to be negative. The results show syntrophic methanogenesis of propionate, butyrate, and valerate slows as acetate concentration increases because hydrogen production also decreases, and consequently, biogas production from syntrophic methanogenesis slows as acetate increases. Bicarbonate also inhibits both acetoclastic and syntrophic methanogenesis but is necessary to prevent acidification (souring) of the digester. At identical steady-state conditions, acetoclastic methanogenesis runs about 1.4 times faster than syntrophic methanogenesis. Because syntrophic methanogenesis produces acetate catabolized by acetoclastic methanogens, both types of methanogens are necessary to maximize biogas production. The culture in the digester is predicted to evolve to optimize the ratio of acetoclastic methanogens to syntrophic methanogens, a condition signaled by a constant, low acetate concentration in the digester effluent. Obtaining volatile solids reduction as high as 75% with MHP requires a feedstock with less than 25% lignin and a culture of acetoclastic methanogens and syntrophic methanogens and their symbiotic bacteria.

Novel Intelligent System Based on Automated Machine Learning for Multiobjective Prediction and Early Warning Guidance of Biogas Performance in Industrial-Scale Garage Dry Fermentation

Industrial-scale garage dry fermentation systems are extremely nonlinear, and traditional machine learning algorithms have low prediction accuracy. Therefore, this study presents a novel intelligent system that employs two automated machine learning (AutoML) algorithms (AutoGluon and H2O) for biogas performance prediction and Shapley additive explanation (SHAP) for interpretable analysis, along with multiobjective particle swarm optimization (MOPSO) for early warning guidance of industrial-scale garage dry fermentation. The stacked ensemble models generated by AutoGluon have the highest prediction accuracy for digester and percolate tank biogas performances. Based on the interpretable analysis, the optimal parameter combinations for the digester and percolate tank were determined in order to maximize biogas production and CH4 content. The optimal conditions for the digester involve maintaining a temperature range of 35–38 °C, implementing a daily spray time of approximately 10 min and a pressure of 1000 Pa, and utilizing a feedstock with high total solids content. Additionally, the percolate tank should be maintained at a temperature range of 35–38 °C, with a liquid level of 1500 mm, a pH range of 8.0–8.1, and a total inorganic carbon concentration greater than 13.8 g/L. The software developed based on the intelligent system was successfully validated in production for prediction and early warning, and MOPSO-recommended guidance was provided. In conclusion, the novel intelligent system described in this study could accurately predict biogas performance in industrial-scale garage dry fermentation and guide operating condition optimization, paving the way for the next generation of intelligent industrial systems.

Optimizing biogas production from palm oil mill effluent utilizing integrated machine learning and response surface methodology framework

This study presents a novel approach to optimize the anaerobic digestion of palm oil mill effluent (POME) for maximum biogas production on an industrial scale. Unlike most optimization studies which are limited to laboratory scale, this study utilized data from a real-world industrial setting to simulate the anaerobic digestion (AD) process. The processes include feedstock pre-treatment, biogas scrubbing, wastewater treatment, and sludge handling. The impact of process conditions such as hydraulic retention time (HRT), organic loading time (OLR), anaerobic sludge recycling ratio (RRAS), treatment effluent recycling ratio (RRTE), and reaction temperature on chemical oxygen demand (COD) removal and methane yield was analysed. An integration of response surface methodology (RSM) and artificial neural network (ANN) is applied to predict the optimal values for the process conditions. The results showed that the optimal values for HRT, temperature, OLR, RRAS, and RRTE are 38.58 days, 45 °C, 1.033 g COD/(L∙day), 0.052, and 0.95, respectively. The optimization improves the COD removal efficiency, SS removal efficiency, and biogas production by 7.38%, 8.37% and 16.18%, respectively when processing 24,134 L/h of POME feed. The optimized AD process is economically viable with a payback period of 5.34 years and a net present value (NPV) of $5,079,000.

Recovering biogas and nutrients via novel anaerobic co-digestion of pre-treated water hyacinth for the enhanced biogas production

The present investigation explores the feasibility of generating biogas from water hyacinth (WH) through a pretreatment process. The WH samples were subjected to a high concentration of H2SO4 pretreatment to enhance biogas production. The H2SO4 pretreatment aids in breaking down the lignocellulosic materials found in the WH. Additionally, it helps modify the cellulose, hemicellulose, and lignin, which assists in the anaerobic digestion process. The samples underwent pretreatment with 5% v/v H2SO4 for 60 min. Biogas production was conducted for both untreated and pretreated samples. Furthermore, sewage sludge and cow dung were used as inoculants to promote fermentation in the absence of oxygen. The results of this study demonstrate that the pretreatment of water hyacinth with 5% v/v H2SO4 for 60 min considerably enhances biogas production through the anaerobic co-digestion process. The maximum biogas production was recorded by T. Control-1, with a production rate of 155 mL on the 15th day compared to all other controls. All the pretreated samples showed the highest biogas production on the 15th day, which is comparatively five days earlier than the untreated samples. In terms of CH4 production, the maximum yield was observed between the 25th and 27th days. These findings suggest that water hyacinth is a viable source of biogas production, and the pretreatment method significantly improves biogas yield. This study presents a practical and innovative approach to biogas production from water hyacinth and highlights the potential for further research in this area.

Biomethane production and microbial strategies corresponding to high organic loading treatment for molasses wastewater in an upflow anaerobic filter reactor.

Molasses wastewater contains high levels of organic compounds, cations, and anions, causing operational problems for anaerobic biological treatment. In this study, an upflow anaerobic filter (UAF) reactor was employed to establish a high organic loading treatment system for molasses wastewater and further investigated the microbial community dynamics in response to this stressful operation. The biogas production increased with an increase in total organic carbon (TOC) loading rate from 1.0 to 14g/L/day, and then it decreased with further TOC loading rate addition until 16g/L/day. The UAF reactor achieved a maximum biogas production of 6800mL/L/day with a TOC removal efficiency of 66.5% at a TOC loading rate of 14g/L/day. Further microbial analyses revealed that both the bacterial and archaeal communities developed multiple strategies to maintain stable operation of the reactor at high organic loading (e.g., Proteiniphilum and Defluviitoga maintained high abundances throughout the operation; Tissierella temporarily dominated the bacterial community at TOC loading rates of 8.0 to 14g/L/day; and multi-trophic Methanosarcina shifted as the dominant methanogen at the TOC loading rates of 8.0 to 16g/L/day). This study presents insights into a high organic loading molasses wastewater treatment system and the microbial flexibility in methane fermentation in response to process disturbances.

Optimizing food waste biodigestion: pre-selection of microbial groups and isolated enzymes using the plackett-burman experimental design

This study investigated the use of anaerobic biodigestion as an ecological technique for treating organic waste in urban solid waste. Biogas production is carried out through the action of microorganisms, and the use of enzymatic hydrolysis can increase biogas production, although it presents economic challenges. The aim of the study was to pre-select microbiological groups and enzymes to optimize the process and increase biogas production using statistical tools. Organic waste from a restaurant and sludge from a sewage treatment plant in Brazil were used, and three bacterial strains and 12 groups of microorganisms, as well as commercial enzymes, were evaluated. The study was divided into four stages to reduce the number of independent variables and increase the accuracy of methane and biogas production results. The results indicated that careful selection of microbial groups had a significant positive impact on biogas and methane production. The interaction between pre-selected groups of microorganisms and enzymes resulted in significant positive effects on cumulative biogas and biometane production. The study concluded that careful selection of microbial groups is essential to maximize biogas production and the efficiency of the anaerobic digestion process. Further, a more detailed identification of microorganisms and their interactions is needed to further optimize biogas production. In general, the appropriate choice of microbial groups is fundamental to the success of anaerobic digestion and biogas production.