Increase In Methane Yield Research Articles

Coal-straw co-digestion-induced biogenic methane production: perspectives on microbial communities and associated metabolic pathways

This study assessed the impacts of wheat straw as a cosubstrate on coal biocoverion into methane and the associated mechanism within methane metabolic pathways. Co-digestion of coal with varying wheat straw concentrations resulted in a remarkable (1246.05%) increase in methane yield compared to that of the control (CK). Moreover, microbial analysis revealed a uniform distribution of Methanosarcinaceae (51.14%) and Methanobacteriaceae (39.90%) in the co-digestion of coal and wheat straw (CWS1) at a ratio of 3:1 (w/w) compared to other treatments such as coal and wheat straw (CWS2) at a ratio of 3:0.5. In addition, Hungatieclostridiaceae and Rhodobacteriaceae were abundant in both co-digesters, whereas the bacterial communities in the CK group were significantly different and more abundant than those in the Peptostreptococcaceae and Enterobacteriaceae groups. The key enzymes related to methanogenic metabolic pathways, including EC: 1.2.99.5 and EC: 2.1.1.86 (facilitating the conversion of CO2 into methane), and EC:1.12.98.1 exhibited significant abundance within CWS1. Aromatic compounds such as 4-(2-chloroanilino)-4-oxobutanoic acid and phthalic acid were substantially more abundant in CWS1 and CWS2 than in CK, indicating the increased bioavailability of coal to microbial activities. This novel approach demonstrates that wheat straw co-digestion with coal during anaerobic digestion modulates microbial communities and their metabolic pathways to enhance methane production from complex substrates such as coal.

Investigating role of corn stover biochar supplementation on continuous pilot scale anaerobic digestion: Performance and microbial community dynamics

Biochar supplementation could facilitate microbial colonization and increase biogas and methane yield in anaerobic digestion (AD). This study investigated the impact of corn stover biochar (CSB) augmentation on the continuous pilot scale AD of rice straw. The CSB supplementation exhibited the daily average specific biogas and methane yield of 368.6 L/kg volatile solids (VS) and 230 L/kg VS, which were 35 % and 37 % higher than the control. Principle component analysis indicated that the VS reduction positively correlated with the daily average specific biogas and methane yield. Metagenomic analysis revealed that the CSB supplementation facilitated microbial colonization with the enrichment of unclassified genera from families Planococcaceae, Clostridiaceae, and Ruminococcaceae, and genus Clostridium and methanogenic archaea (Methanosarcina and Methanobacterium). The co-occurrence network revealed a notable shift in microbial interactions following the supplementation of CSB as an additive in AD. These results offer insights for enhancing the performance of the AD using CSB.

Recovering nutrients and unblocking the cake layer of an electrochemical anaerobic membrane bioreactor

The sustainable development strategy shifts water treatment from pollution removal to resource recovery. Here, an electrochemical resource-recovery anaerobic membrane bioreactor (eRAnMBR) that employed a magnesium plate and conductive membrane as dual anodes is presented and shows excellent performance in carbon, nitrogen, and phosphorus recovery, as well as 95% membrane anti-fouling. The Mg2+ released alters the physicochemical properties of sludge, unblocking the cake layer, and recovers ammonium and phosphate, yielding 60.64% purity and 0.08 g d−1 struvite deposited onto cathode to be separated from sludge. The enhanced direct interspecies electron transfer, along with hydrogen evolution and alkalinity increase due to the electrochemical reactions, significantly increase methane yield and purity (93.97%) of the eRAnMBR. This increased internal energy can cover the additional electricity and electrode consumption. This integrated eRAnMBR reactor boasts the benefits of short process, low maintenance, and low carbon footprint, introducing a concept for the next generation of wastewater treatment.

Synchronously improving intracellular electron transfer in electron-donating bacteria and electron-accepting methanogens for facilitating direct interspecies electron transfer during anaerobic digestion of kitchen wastes

Two major issues generally limit the effectiveness of direct interspecies electron transfer (DIET) during anaerobic digestion: 1) lack of essential electrical connection component, electrically conductive pili (e-pili) or multi-heme c-type cytochrome (MHC); 2) the thermodynamic limitations of combining electrons with protons for reducing carbon dioxide to methane. To address both issues, a strategy for facilitating DIET via combining ethanol-type fermentation pretreatment (EFP) with NaCl addition during anaerobic digestion of kitchen wastes was proposed. Combining EFP with NaCl addition dramatically increased methane yield rates (531.3 ± 11.4 vs 410.5 ± 8.7 mL/gVSadded/d) and efficiencies of conversion of organic substrates to methane (571.2 ± 13.8 vs 488.7 ± 11.7 mL/gVSremoval). The increased performances by combining EFP with NaCl addition were higher than that by independent EFP or NaCl addition. Paludibacter sp., Petrimonas sp. and Syntrophomonas wolfei were the predominant and metabolically active electron-donating bacteria, and their expression of genes for e-pili/MHCs by combining EFP with NaCl addition was higher than that by independent EFP or NaCl addition. Methanothrix soehngenii and Methanoculleus bourgensis were the predominant and metabolically active electron-accepting methanogens, and their expression of genes for carbon dioxide reduction pathway for methanogenesis by combining EFP with NaCl addition was higher than that by independent EFP or NaCl addition. In addition, EFP specifically increased the transcript abundance of genes for NAD+/NADH transformation closely associated with the formation of e-pili/MHCs, while NaCl addition specifically increased the transcript abundance of genes for coenzyme F420/F420H2 transformation known to participate in reduction of carbon dioxide to methane.

Anaerobic co-digestion of winery wastewater with sewage sludge for methane production: Complementary feedstocks and potential direct interspecies electron transfer

Combining winery wastewater (WW) with sewage sludge (SS) in anaerobic co-digestion (AcoD) presents a promising approach for effective waste management and enhanced energy recovery. This study aimed to evaluate the efficiency and changes in microbial communities during the AcoD of WW with SS at 35 °C, using a mix of batch and semi-continuous testing methods. In the batch experiments, the highest hydrolysis rate (0.19 day−1) and methane production (285.61 ± 4.83 mL/g VS) were achieved at a WW:SS ratio of 3:2, exceeding those of SS mono-digestion by 126 % and 113 %, respectively. Furthermore, the semi-continuous experiments revealed a significant 30.0 % boost in the electron transport system activity and a notable 25.8 % increase in coenzyme F420 activity within the AcoD of WW with SS. Microbial analysis illustrated that AcoD of WW with SS significantly enriched the prevalence of potential genera associated with direct interspecies electron transfer (DIET), such as Longilinea, Bellilinea (genus of Chloroflexi), Syntrophomonas, Pseudomonas, Methanosarcina, and Methanobacterium species. Additionally, semi-continuous experiments demonstrated that AcoD facilitated interspecies hydrogen transfer between syntrophic bacteria and hydrogenotrophic methanogens, resulting in increased methane yield. Co-digestion of WW with SS is a more economical strategy that significantly enhances the stability of microbial communities through the use of complementary feedstocks. These results may offer valuable guidance for the efficient resource utilization of co-digestion processes involving WW and SS.

Effects of nano-bubble water on anaerobic co-digestion of cabbage waste and cow manure under mesophilic and thermophilic conditions

ABSTRACT The impact of four nano-bubble water (NBW) additions on the hydrolysis rate, methane yield, and microbial community of co-digestion of cabbage waste (CW) and cow manure (CM) under mesophilic and thermophilic conditions were investigated. Adding NBW under mesophilic conditions promoted hydrolysis, and the highest soluble chemical oxygen demand of the mesophilic digesters with the addition of CO2-NBW increased by 15.86%. Methane yield in the mesophilic digesters with Air-NBW and CO2-NBW increased by 17.54% and 14.72%, respectively. Moreover, the addition of NBW further accelerated the methane yield rate under mesophilic conditions. Due to the influence of thermophilic temperature, the impact of NBW addition on hydrolysis, methane yield, and methane yield rate in the thermophilic digesters did not differ significantly from the control. The addition of Air-NBW and N2-NBW in the thermophilic digesters resulted in only marginal increases in methane yield, by 1.09% and 5.61%, respectively. NBW addition enhanced both the abundance and diversity of microbial communities in both mesophilic and thermophilic digesters. The addition of NBW represents a promising technological advancement for enhancing the efficiency of anaerobic co-digestion of CW and CM.

Enhancing methane yield and shifting microbial communities in anaerobic reactors treating lipid-rich dairy wastewater through exogenous lipase addition

This study explores a novel enzymatic pretreatment approach in anaerobic reactors for dairy wastewater, using lipase AY Amano to enhance methane production and modify microbial and archaeal community composition. Batch and semi-batch reactors with a total volume of 2000 mL were used to treat dairy wastewater with initial COD of 2000 and 15,000 mg L−1, respectively. In a new novel approach, the semi-batch reactors underwent a three-phase operation: 30 days of acclimation, 30 days of rest, and 30 days of active operation. Adding lipase (0.05% wv−1) as a pretreatment significantly increased methane yield over the 90 days by 135–138% compared with the control (without enzyme addition). The organic loading rate reached 0.22 g COD day−1 L−1. Furthermore, 30 days after the end of the semi-batch reactor approach (120 days from the start), reusing sludge in batch reactors increased methane yield by 114–122% compared to the control. This increase was linked to the emergence and shift of new methanogenic communities within the sludge. Integrating hydrolytic enzymes into the anaerobic treatment enhances performance and sustainability by fostering methanogen-enriched microbial communities. This is crucial for maximizing methane production but may increase costs, requiring further economic feasibility research.

Enhancing methane production in anaerobic digestion of waste activated sludge by combined thermal hydrolysis and photocatalysis pretreatment

Thermal hydrolysis (TH) is promising for sludge pretreatment, but the refractory substances generated at high temperatures inhibit anaerobic digestion. In this study, a novel combined TH and photocatalytic pretreatment method was proposed to improve the anaerobic digestion performance of waste activated sludge. The results showed that the combined pretreatment (170 °C, 0.5 g/L TiO2) increased methane yield by 66 % from 111 ± 5 m L/g VS to 185 ± 5 m L/g VS. After TH pretreatment, photocatalysis further promoted sludge solubilization by destroying extracellular polymeric substances, resulting in an increase in released soluble organic matter from 292 ± 16 mg/L to 4,091 ± 85 mg/L. In addition, photocatalysis improved the biodegradability of sludge by reducing the melanoidin and humic acid contents by 26 % and 20 %, respectively. The proposed novel pretreatment method effectively overcomes the bottleneck of TH technology and provides an alternative pretreatment technology for improving sludge resource recovery.

Biochar accelerates methane production efficiency from Baijiu wastewater: Some viewpoints considering direct interspecies electron transfer

The low pH of Maotai-flavor Baijiu wastewater (MFBW) adversely affects its anaerobic digestion (AD) performance, resulting in low AD efficiency. Here, coconut shell was used to produce biochar. The characteristics of biochar were regulated through acid, alkali, and magnetic modification, respectively. Biochar and modified biochars were applied to assist the AD of MFBW. The results showed that biochar could significantly increase methane yield by 220.8 %–241.7 % with the corresponding soluble chemical oxygen demand (sCOD) degradation increasing by 52.3 %–57.5 % (p < 0.05). Joint modification could significantly enhance the electron donating capacity from 0.0042 to 0.0095 mmol e−1/g (p < 0.05). The combined modification with magnetic alkali had the best stimulating effect on the AD process, which might be related to the conductive particles (Fe3O4) formed during magnetization processes. The modified biochar featured a high degree of surface roughness, a relatively large aperture, and strong electron donating ability, all of which were beneficial to the colonization and microbial growth. Supplementation with biochar resulted in the enrichment of Proteobacteria, Firmicutes, and Actinobacteria, especially for Syntrophomonas (rising from 0.013 % to 6.74 %–10.93 % of relative abundance). These microorganisms are related to the hydrolysis, acidification, and extracellular electron transfer. The enrichment of electroactive microorganism is a prerequisite for improving the direct interspecies electron transfer pathway. This study provides theoretical support for efficient MFBW treatment.

Mechanism underlying the sustained stimulatory effects of energization on biomethane recovery from food waste post-energization cessation

Microbial electrolysis cell-assisted anaerobic digestion represents a promising approach for enhancing methanogenesis. This study investigated the impact of varying energy levels followed by long-term open circuit on biogas recovery from food waste.The results demonstrated that a mild voltage of 0.4 V resulted in 61.7% increase in methane yield, with a methane composition reaching 78.89% vol and a remarkable reduction in digestion time by 8 days. Additionally, the facilitated effects remained after prolonged periods of open-circuit. In-depth study revealed that energization significantly enhanced organic hydrolysis, redox proteins secretion and sludge electro-activity. Microbial communities showed that the ever-present energization enriched the hydrolytic bacterium and electrophiles. Subsequent investigations also revealed the upgradation of enzyme-encoding genes associated with hydrolysis and the synthesis of flavin and its homologs (i.e. ribE, ssuE and nfrA2). These findings collectively demonstrated the enduring benefits of energization were linked to the enhanced hydrolysis and regulated mediator-mediated electron transfer pathway.

Pelletized Straw for Biogas Production—Substrate Characterization and Methane Formation Potential

The use of agricultural residues in biogas plants is becoming increasingly important, as they represent an efficient and sustainable substrate alternative. Pelletizing straw can have positive effects on transportation, handling, and biogas production. In this study, different grain straw pellets from mobile and stationary pelleting plants in Germany as well as the corresponding untreated straw were characterized and investigated for their suitability for anaerobic digestion (AD). Therefore, tests on the biochemical methane potential (BMP) and the chemical–physical characterization of unpelletized straw and straw pellets were carried out. The characterization of the pellets and the straw revealed a high average total solid content of 91.8% for the industrially produced straw pellets and of 90.8% for the straw. The particle size distribution within the tested pellet samples varied greatly depending on the pelleting process and the pre-treatment of the straw. In addition, a high C/N ratio of 91:1 on average was determined for the straw pellets, whereas the average higher heating value (HHV) content of the pellets was 17.58 MJ kg−1. In the BMP tests, the methane production yields ranged from 260–319 normal liter (NL) CH4 kg−1 volatile solids (VS) for the straw pellets and between 262 and 289 NL CH4 kg−1 VS for the unpelletized straw. Overall, pelleting increases the methane yield on average from 274 to 286 NL CH4 kg−1 VS, which corresponds to an increase in methane yield of 4.3%. Based on the results, the feasibility of using straw pellets for AD could be confirmed, which can facilitate the possibility of increased biogas production from agricultural residues such as straw pellets and thus make the substrate supply more sustainable.

Enhanced anaerobic digestion of waste-activated sludge by thermal-alkali pretreatment: a pilot-scale study.

The composition of waste-activated sludge (WAS) is complex, containing a large amount of harmful substances, which pose a threat to the environment and human health. The reduction and resource utilization of sludge has become a development demand in sludge treatment and disposal. Based on the technical bottlenecks in the practical application of direct anaerobic digestion technology, this study adopted two different thermal and thermal-alkali hydrolysis technologies to pretreat sludge. A pilot-scale experiment was conducted to investigate the experimental conditions, parameters, and effects of two hydrolysis technologies. This study showed that the optimal hydrolysis temperature was 70 °C, the hydrolysis effect and pH can reach equilibrium with the hydrolysis retention time was 4-8 h, and the optimal alkali concentration range was 0.0125-0.015 kg NaOH/kg dry-sludge. Thermal-alkali combination treatment greatly improved the performance of methane production, the addition of NaOH increased methane yield by 31.2% than that of 70 °C thermal hydrolysis. The average energy consumption is 75 kWh/m3 80% water-content sludge during the experiment. This study provides a better pretreatment strategy for exploring efficient anaerobic digestion treatment technologies suitable for southern characteristic sewage sludge.

Advancing Thermophilic Anaerobic Digestion of Corn Whole Stillage: Lignocellulose Decomposition and Microbial Community Characterization

Converting corn grains into bioethanol is an expanding practice for sustainable fuel production, but this is accompanied by the production of large quantities of by-products such as whole stillage. In the present study, the influence of advanced wet oxidation and steam explosion (AWOEx) pretreatment on biogas production and lignocellulose decomposition of corn whole stillage (CWS) was evaluated using semi-continuous thermophilic reactors. The digestion of the CWS was shown to be feasible with an organic loading rate (OLR) of 1.12 ± 0.03 kg VS/m3 day and a hydraulic retention time (HRT) of 30 days, achieving a methane yield of 0.75 ± 0.05 L CH4/g VSfed for untreated stillage and 0.86 ± 0.04 L CH4/g VSfed for pretreated stillage, corresponding with an increase in methane yield of about 15%. However, the reactors showed unstable performance with the highest investigated OLRs and shortest HRTs. Under optimal conditions, the conversion efficiencies of COD, cellulose, hemicellulose, and lignin were 88, 95, 97, and 59% for pretreated CWS, and 86, 94, 95, and 51% for untreated CWS, respectively. Microbial community analysis showed that Proteiniphilum, MBA03, and Acetomicrobium were the dominant genera in the digestate and were likely responsible for the conversion of proteins and volatile fatty acids in CWS.

Impact of tannery wastes on anaerobic co-digestion: enhancing biogas production and process efficiency

The study investigates the potential of anaerobic co-digestion (AcoD) as a sustainable solution for managing putrescible organic waste generated by leather processing. Three experiments were conducted to assess the impact of various tannery wastes, pretreatment methods, and waste combinations on methane production. Experiment 1 demonstrated that co-digesting tannery wastewater primary sludge (TWPS) and fleshings significantly increased methane yield compared to digesting TWPS alone, though the addition of chromium- and vegetable-tanned leather wastes decreased yield. Experiment 2 explored TWPS pretreatment methods and found that ultrasonic pretreatment increased soluble chemical oxygen demand (SCOD) but did not significantly improve methane yield, suggesting that pretreatment may not be necessary. Experiment 3 revealed that increasing the proportion of fleshings to TWPS resulted in higher methane yield, ranging from 226.52 mL/gVS with 6% fleshings to 395.71 mL/gVS and 538.34 mL/gVS with 12% and 20% of fleshings, respectively. Additionally, this increase in fleshings also led to a reduction in digester volume. These findings highlight the importance of AcoD in addressing both environmental and economic challenges in the leather industry.Graphical

Enhancing the efficiency of high solid anaerobic digestion of empty fruit bunches under thermophilic conditions by particle size reduction and co-digestion with palm oil mill effluent

This study investigates the impact of thermophilic high solid anaerobic digestion (HS-AD) on biogas production from empty fruit bunches (EFB), focusing on the effects of total solids (TS) loading (5–40 %), particle size reduction (0.5, 3.25, and 6 cm), and co-digestion with palm oil mill effluent (POME) (10–30 % VS basis). The HS-AD at a 15–20 % TS loading has a methane yield of 103.4–105.3 mL CH4/g-VS with 24.6–25.1 % biodegradability. Particle size reduction to 0.5 cm enhanced methane yield by 54–61 % and improved hydrolysis rates by 45 % compared to the untreated EFB (6 cm) at a 15–20 % TS loading. Co-digestion of EFB with POME at a ratio of 31:1 based on VS basis led to a synergistic effect of 17.77 mL CH4/g-VS, increasing methane yield by 24–46.5 % and improving process stability, as evidenced by a 22.8–38.1 % reduction in volatile fatty acids (VFAs) accumulation. Microbial community analysis showed a 2-fold increase in the relative abundance of hydrogenotrophic methanogens (Methanothermobacter sp. and Methanoculleus sp.) during co-digestion, while the abundance of key cellulolytic bacteria (Clostridium sp. and Fibrobacter sp.) increased by 1.5-fold. The optimized HS-AD process achieved a maximum methane yield of 287.77 mL CH4/g-VS and a biodegradability of 61.2 % under thermophilic conditions, with a 20 % POME co-digestion addition (31:1 VS ratio) and 0.5 cm particle size. These findings demonstrate the potential of thermophilic HS-AD for the sustainable management of EFB and highlight the importance of process optimization and co-digestion strategies for enhanced biogas production from EFB.

Thermophilic-mesophilic temperature phase anaerobic co-digestion compared with single phase co-digestion of sewage sludge and food waste

Anaerobic co-digestion is an effective method for addressing the issue of a single substrate not being able to achieve optimal conditions for anaerobic digestion. By adjusting the mixture ratio of sewage sludge and food waste to achieve the optimal carbon to nitrogen ratio, the effectiveness of thermophilic–mesophilic temperature phase anaerobic co-digestion (TPAcD) was evaluated in comparison to single phase mesophilic anaerobic co-digestion (MAcD) and thermophilic anaerobic co-digestion (TAcD). The results indicated that TPAcD increased methane yield by 50.3% and 32.7% compared to MAcD and TAcD, respectively. The variation in VFA, pH, and ammonia nitrogen levels demonstrated that TPAcD combines the advantages of both MAcD and TAcD, with a higher hydrolysis rate in the early stage under thermophilic conditions (55 °C) and a suitable environment in the later stage under mesophilic conditions (35 °C). The kinetic parameters of anaerobic co-digestions also demonstrated that TPAcD performs better. Therefore, further research on TPAcD of sewage sludge and food waste is warranted due to its significant improvements in methane production rate, total methane yield, and system stability. Additionally, TPAcD contributes to reducing carbon emissions and supports the realization of “carbon neutrality”.

New insight of combined hydrothermal and ultrasonic pretreatment for methane production from anaerobic digestion of food waste

ABSTRACT Food waste (FW) biotransformation into bioenergy has garnered a lot of scientific interest as a way to address the energy crisis and trash disposal issues. FW is converted into biogas, a gaseous combination of biomethane and carbon dioxide. In order to valorize FW, anaerobic digestion (AD) with combined pretreatment (hydrothermal (HT) and ultrasonic (US)) is used as a potential method. Three digesters were investigated: the control (unpretreated), HT(121°C) + US, and HT(134°C) + US, respectively. Based on changes in the combined pretreatment conditions, the paper assessed the methane productivity. Furthermore, kinetic modeling was evaluated with six kinetic models. The results show that the HT pretreatment at 121°C combined with US improves the volatile solid (VS) removal to 73 ± 5% and the methane yield to 529.7 ± 11 NmL/gVS. Both the Transference model and the first order have the greatest fits in terms of R2, and they also have the best fits in terms of relative errors, and methane production rate, respectively. The combined pretreatment has a positive impact on increasing methane yield as well as stabilizing the anaerobic digestion process.

Maximizing the value of liquid products and minimizing carbon loss in hydrothermal processing of biomass: an evolution from carbonization to humification

Hydrothermal carbonization (HTC) converts wet biomass into hydrochar and a process liquid, but aromatic compounds in the products have been reported as a roadblock for soil applications as they can inhibit germination, plant growth, and soil microbial activity. Here, we compared HTC and hydrothermal humification (HTH) of cow manure digestate while varying the initial alkaline content by adding KOH. HTH converted 37.5 wt% of the feedstock to artificial humic acids (A-HAs) found in both solid and liquid, twice that of HTC. HTH reduced phenolic and furanic aromatic compounds by over 70% in solids and 90% in liquids. The A-HAs in HTH resemble natural humic acids (N-HA), based on FTIR, UV–vis spectra, and CHN and XRD analysis. The HTH liquid possesses 60% higher total organic carbon (TOC) than HTC. Although one-third of TOC can be precipitated as A-HA, a high TOC concentration remains in the liquid, which is shown to be mainly organic acids. Therefore, we also evaluated the HTC and HTH liquids for anaerobic biomethane production, and found that compared to the original cow manure digestate, the HTH liquids increased methane yield by 110.3 to 158.6%, a significant enhancement relative to the 17.2% increase seen with HTC liquid. The strong reduction in organic acids during biogas production from HTH liquid indicates the potential for converting soluble byproducts into methane, while maintaining high A-HAs levels in the solid product.Graphical

Comprehensive insights into the effects of acidogenic off-gas utilization on successive biogas production, microbial community structure and metabolite distribution during two-stage anaerobic digestion

Although two-stage anaerobic digestion (TSAD) technology has been investigated, the mechanisms regarding the impact of acidogenic off-gas (AOG) on successive methane production have not been well addressed. In this study, a novel TSAD system was designed. Food waste, as the main substrate, was co-digested with chicken manure and corn straw. The acidogenic gas beyond atmospheric pressure was introduced into the bottom of the methanogenesis reactor through a stainless steel diffuser. Results showed the addition of AOG increased the methane yield from 435.2 to 597.1 mL/g VSin in successive methanogenesis stage, improved by 37.2 %, and increased the energy yield from 9.0 to 11.3 kJ/g VSsubstrate. However, the theoretical contribution of hydrogenotrophic methanogenesis using H2 contained in AOG was only 15.2 % of the increased methane yield. After the addition of AOG, the decreased levels of ammonia nitrogen and butyrate indicate that the stability of the AD system was improved. The electron transfer system and co-enzyme F420 activity were enhanced; however, the decrease in acetate kinase activity indicates aceticlastic methanogenesis may have been weakened. The microbial diversity and species richness were improved by the added AOG. Methanosarcina was more competitive than Methanothermobacter, enhancing the syntrophic effect. The relative abundance of protein degradation bacteria norank_f_Anaerolineaceae and lipid degradation bacteria Syntrophomonas was increased. Metabolite analysis confirmed that the addition of AOG promoted amino acid metabolism, the biosynthesis of other secondary metabolism and lipid metabolism. The improved degradation of recalcitrant organic components (lipids and proteins) in food waste was responsible for the increased methane yield. This study provides an in-depth understanding of the impact of AOG utilization on successive methane production and has practical implications for the treatment of food waste.

Enhancing biogas production through photocatalytic pretreatment of rice straw co-digested with cow dung and food waste using a novel g-C3N4/SiO2/bentonite catalyst

This study investigates the application of a novel composite photocatalyst, g-C3N4/SiO2/ Bentonite, for rice straw pretreatment, aiming to enhance biogas production in anaerobic digestion. The photocatalytic pretreatment disrupts rice straw's lignin and hemicellulose structures, reducing silica content for improved microbial degradation. Five 2 L anaerobic digesters were employed with rice straw as the substrate and co-digestion materials, including cow dung and food waste. Rice straw treated with the g-C3N4/7.5% SiO2/5% Bentonite catalyst exhibited a remarkable 37% increase in methane yield compared to untreated rice straw. This photocatalytic process led to a 31% increase in cellulose content and a 30% reduction in lignin after 6 hours of pretreatment. Simultaneously, silica content in the rice straw decreased to 6.4% after 6 hours, resulting in a 48% increase in the carbon proportion. These findings underscore the potential of integrated photocatalysts for significantly enhancing biogas production efficiency through the pretreatment of lignocellulosic biomass.