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This study investigates the potential of co-digesting sewage sludge and food waste for biogas production. Several options for renewable energy have been suggested, and one of them is the production of biogas using biomass. Biomass energy has been used in various applications due to its availability and environmental benefits. Co-digestion, which involves the mixing of two or more substrates, has been carried out to enhance the biogas production process. To evaluate the performance of anaerobic digestion, key parameters such as organic loading rate, potential of hydrogen, temperature, hydraulic retention time, and methane content were analyzed. The correlation between these variables was investigated using data from peer-reviewed articles published between 2010 and 2020. From these analyses, a positive correlation was identified between temperature and potential of hydrogen. Additionally, negative correlations were observed between organic loading rate and potential of hydrogen, temperature and organic loading rate, organic loading rate, and hydraulic retention time, as well as between organic loading rate and methane content, and potential of hydrogen and methane content. Principal component analysis was employed to assess the impact of operational variables on methane production. Our findings revealed that the key operational factors include hydraulic retention time, organic loading rate, and temperature. These findings provide valuable insights into the factors influencing biogas production from sewage sludge and food waste through anaerobic digestion and can be used to optimize the process. In conclusion, biomass energy has shown great potential for biogas production, and co-digestion has emerged as a promising strategy to enhance the process. [ABSTRACT FROM AUTHOR]

Agribusiness ranks second as the sector with the highest greenhouse gas emissions linked to methane, constituting a crucial challenge for global sustainability. Although its impact on climate change is considerable, small rural farmers do not have effective technologies to manage the organic waste derived from their daily activities. In this context, anaerobic digestion is an innovative solution that converts waste into biogas and biofertilizers, promoting a sustainable and circular approach. However, its implementation faces significant barriers due to inadequate designs and poor operational practices, which makes its adoption difficult in rural areas. This applied theoretical research seeks to overcome these barriers by improving the design and operation of small-scale biogas plants. The system studied operates at 70% of its capacity, with a hydraulic retention time of 20 days and a feed of 4 kg organic matter. The substrates considered were 30% organic waste and 70% bovine manure, achieving an average production of 63.75 L CH4/kg of organic matter, which exceeded the usual yields of small biodigesters. A mathematical model was created and applied to the case study with an R2 correlation of 98% and a pseudo-R2 of 89.5%, evidencing a remarkable predictive capacity. This biogas plant model is efficient and sustainable, and it is presented as a viable solution for small rural farmers. [ABSTRACT FROM AUTHOR]

This study examines the co‐digestion of landfill leachate (LFL) with pineapple peel, focusing on biogas production. The study was conducted with a lab‐scale batch anaerobic digester using a 30 L working volume batch completely mixed reactor at 35 °C to investigate the monodigestion of leachate and of pineapple peel and their co‐digestion with three different mixing ratios. The results of all of the experiments in the study were fitted with first‐order kinetic models to compare the behavior of different batches through rate constants (k). As expected, the anaerobic digestion of 25 L leachate achieved a biogas yield of 38 L kg−1 volatile solids (VS)consumed and a VS removal efficiency of 30%, both markedly lower than those achieved with 3 kg VS pineapple peel per m3 in 25 L tap water (513 L kg−1 VSconsumed biogas yield and 80% VS removal efficiency). The leachate, which had a fixed volume of 25 L, was mixed with 1, 2, and 3 kg VS pineapple peel m−3. The results showed that co‐digestion with 2 kg VS pineapple peel m−3 achieved the highest biogas yield of 431 L kg−1 VSconsumed and approximately 80% VS and 90% chemical oxygen demand (COD) removal efficiency with stable conditions in the reactor. The first‐order kinetics equation was selected to characterize the anaerobic digestion and was able to describe and compare the anaerobic digestion processes of the experiments. The rate constants (k) were 0.25, 0.22, and 0.18 day−1 for co‐digestion with 1, 2, and 3 kg VS pineapple peel m−3. [ABSTRACT FROM AUTHOR]

Indiscriminate disposal of crop and animal wastes has grown in acceptance across the globe as an environmentally hazardous practice. This study used a 225L polyethylene digester that was specially made to produce biogas from anaerobic co-digestion of palm oil sludge, cassava peels, and cow dung using ground eggshells for pH stabilization and a greenhouse for temperature control. Cassava peels, palm oil sludge, cow dung, and water were combined in a ratio of 1:1:2:5.3, respectively, and 1.3 kilograms of crushed eggshells were added. The bio-digestion system generated 650.60 L of cumulative biogas throughout the 30-day sludge retention period. The pH averaged 6.0, and the slurry temperature averaged 34.76oC during digestion, which is favorable for the production of biogas since microbial populations thrive under hospitable conditions. The biogas produced after a hydraulic retention time (HRT) of over 20 days had the highest methane concentration of 60%, while days under 10 HRT had the lowest methane content of 45.5%. On the 13th day of anaerobic digestion, biogas output peaked at 34.90L, and pH and temperature were maintained at 6.5 and 35.0°C, respectively, the ideal ranges for a healthy process. An efficient technique for producing energy in the form of biogas was shown by optimized anaerobic co-digestion of animal and crop waste utilizing ground eggshells and a greenhouse for pH and temperature control. Future research should focus on developing more efficient, cheaper microbial agents, such as enzymes for biological pre-treatment of palm oil sludge to reduce lignin, which negatively impacts biogas generation. [ABSTRACT FROM AUTHOR]

The brewery industry generates a huge quantity of brewers' spent grain (BSG) which can pose waste disposal and pollution problems. Anaerobic digestion of BSG, a recalcitrant lignocellulosic waste, is slow but can be enhanced by bioaugmentation, biostimulation and co-digestion to obtain a higher biogas yield. Hence, the effect of inoculum from brewery wastewater sludge (BWWS), iron (III) chloride (FeCl3) and co-digestion with poultry manure (PM) on the production of biogas from BSG was investigated. Cumulative biogas and biomethane yields of 588.19 NL/kgVS and 400.34 NLCH4/kgVS, respectively, were obtained from a slurry consisting of a blend of 60% BSG and 40% PM plus 15 mg L-1 FeCl3 in BWWS, after 30 day retention time at 37 oC. However, mono-digestion of BSG in only water yielded 402.17 NLbiogas/kgVS and 262.86 NLCH4/kgVS. The synergistic effects of inoculum from BWWS, FeCl3 and poultry manure on anaerobic digestion of BSG resulted in 46% and 52% increases in biogas and methane yields, respectively, compared with BSG mono-digestion. The biogas and biomethane production kinetics were well described by the dual pooled first order, logistic and modified Gompertz models. [ABSTRACT FROM AUTHOR]

Background: The high cost of fossil fuels has driven the exploration of renewable energy alternatives. This study investigates the anaerobic co-digestion of waterleaf, cow dung, and food waste to optimize biogas production. Methods: Four co-digestion experiments were performed using a prototype plastic bio-digester over 50 days. The combinations tested were: waterleaf with cow dung, waterleaf with food waste, food waste with cow dung, and a mix of all three feedstocks. Results: Co-digestion of waterleaf and food waste yielded an average biogas output of 25%, with a pH of 7.2 and a carbon-to-nitrogen (C/N) ratio of 28. Combining waterleaf and cow dung produced a 31% yield, a pH of 7.2, and a C/N ratio of 29. The mixture of food waste and cow dung resulted in a 34% biogas yield, with a pH of 7.1 and a C/N ratio of 30. The highest yield, 46%, was achieved by co-digesting waterleaf, cow dung, and food waste, with a pH of 7 and a C/N ratio of 32. All feedstock combinations maintained neutral pH levels, benefiting from the unique properties of each component: waterleaf provided vitamins A and C, food waste supplied carbohydrates and proteins, and cow dung contributed anaerobic microbes essential for digestion. Additionally, temperature was a significant factor influencing biogas production. Conclusion: Co-digesting waterleaf, cow dung, and food waste maximized biogas production, demonstrating the potential for enhanced renewable energy generation through optimized anaerobic digestion processes.

The recovery of energy potential through anaerobic digestion is a widely used method for treating biodegradable waste. However, challenges related to operational issues, waste characterization, and process instability hinder its widespread application and result in low methane yields. This review aims to organize and analyze the static and dynamic parameters that influence biogas yield in order to optimize its production. Biogas typically consists of 50–70% methane (CH4) and 30–50% carbon dioxide (CO2) along with traces of other gases. The paper highlights various solutions to enhance CH4 production, including substrate pre-treatment, co-digestion, Fe0 powder addition, anaerobic fungi, multi-stage biodigester design, and controlling factors influencing anaerobic digestion. These factors primarily include methanogenic potential, C/N ratio, digestion temperature, pH, reactor tightness, and Pressure. However, the use of bioreactors faces technical, socio-economic, and environmental constraints that vary between developed and less developed countries, as discussed in the paper. Through an analysis of over 30 substrate types, the optimum ratios for certain substrates to achieve higher biogas yields were identified. For cow manure mixed with other materials, the yield increases within a C/N ratio of 20–30 and decreases at a ratio of 35. In the case of poultry droppings mixed with other substrates, the yield increases within a C/N ratio of 18–22. Food waste yield, on the other hand, varies significantly due to the differing characteristics of food waste sources. In summary, this study emphasizes the importance of optimizing biogas production through understanding and controlling the influencing factors. It provides insights into potential solutions and optimum substrate ratios for improved biogas yield. [ABSTRACT FROM AUTHOR]

The global shift towards sustainable waste management has led to an intensified exploration of co-digestion and co-treatment of sewage and organic waste using anaerobic reactors. This review advocates for an integrated approach where organic waste is treated along with the sewage stream, as a promising solution to collect, treat, and dispose of organic waste, thereby reducing the environmental and economic burden on municipalities. Various efforts, ranging from laboratory to full-scale studies, have been undertaken to assess the feasibility and impacts of co-digestion or co-management of sewage and organic waste, using technologies such as up-flow anaerobic sludge blankets or anaerobic membrane bioreactors. However, there has been no consensus on a standardized definition of co-digestion, nor a comprehensive understanding of its impacts. In this paper, we present a comprehensive review of the state-of-the-art in liquid anaerobic co-digestion systems, which typically operate at 1.1% total solids. The research aims to investigate how the integration of organic waste into mainstream anaerobic-based sewage treatment plants has the potential to enhance the sustainability of both sewage and organic waste management. In addition, utilizing the surplus capacity of existing anaerobic reactors leads to significant increases in methane production ranging from 190 to 388% (v/v). However, it should be noted that certain challenges may arise, such as the necessity for the development of tailored strategies and regulatory frameworks to enhance co-digestion practices and address the inherent challenges. [ABSTRACT FROM AUTHOR]

Slaughterhouse waste (SW) poses significant environmental challenges due to its complex composition, but anaerobic digestion offers a way to recover valuable biogas from SW. This study investigated the anaerobic co-digestion of beef cattle slaughterhouse waste (BCSW) with either cattle feces (CF) or swine slurry (SS). The biomethane potential, maximum methane yield (Mmax), lag phase duration, and effective digestion time (Teff) for the individual substrates and the combinations were analyzed. BCSW alone exhibited Mmax of 578.5 Nml CH4/g VSadded with a lag phase of 11 days, while CF and SS alone exhibited Mmax of 397.2 and 289.8 Nml CH4/g VSadded, respectively. Co-digestion of BCSW and SS resulted in Mmax increase of 48–75.5%, with negligible effects on Teff compared to solitary SS digestion. Similarly, co-digestion of BCSW and CF increased Mmax by 6.2–40.4%, with no significant impact on Teff compared to solitary CF digestion. However, both co-digestions led to a reduction in Mmax (12.1–27%) when compared to BCSW digestion alone. Co-digestion with SS shortened the lag phase duration by 2.8–7.8 days and accelerated Teff by 5.8–8.3 days due to SS's high concentrations of essential micronutrients like cobalt and nickel which aid digestion. This study concluded that co-digestion of BCSW with SS is an effective strategy for enhancing methane production and digestion efficiency, offering a viable approach for proper disposal of BCSW while improving biogas output. [ABSTRACT FROM AUTHOR]

Growing demand for alternative sources of energy that are renewable has emerged from the extensive use of fossilized resources of energy and associated problems related to their disproportionate consumption. A key strategy for achieving the world's renewable energy goals is the utilization of waste materials which are biodegradable for the generation of biogas. The primary objective of the present research investigation aimed to determine how adding different amounts of banana stem juice (BSJ) influence the yield kinetics and the generation of biogas during the anaerobic decomposition of chicken feather (CF). The aforementioned investigation used five distinct batch digestion units (designated A-E). Digester A had only CF, while the digester E contained only BSJ. The remaining digesters comprised different mass fractions of CF and BSJ (i.e., 75% CF:25% BSJ, 50% CF:50% BSJ, and 25% CF:75% BSJ). The cumulative biogas generated from the digesters with the corresponding mixtures 100% CF:0% BSJ, 75% CF:25% BSJ, 50% CF:50% BSJ, 25% CF:75% BSJ, and 0% CF:100% BSJ are 224, 560, 572, 622, and 152 ml/20 g of feeding substrates, respectively. The modified Gompertz model revealed that the anaerobic co-digestion of waste CF with BSJ improved the amount of biogas produced (A), the optimal specific production of biogas (휇m), and the latency (λ) compared to untreated CF by 161.01%, 147.30%, and 2.53%, respectively. The experimental studies confirmed that co-digesting BSJ and CF during the biogas generation process led to a considerable reduction in COD (chemical oxygen demand) and an increase in biogas yield. [ABSTRACT FROM AUTHOR]

This study explores the potential of biochar derived from microwave-assisted catalytic pyrolysis of solid digestate as an additive to enhance the stability and performance of the anaerobic digestion process. The focus was placed on the effects of biochar dosage, pyrolysis temperature, and pyrolysis catalyst on methane production. Biochemical methane potential (BMP) tests using synthetic food waste as the substrate revealed a dosage-dependent relationship with specific methane yield (SMY). At a low biochar dosage of 0.1 g/g total solids (TS), improvement in methane (CH4) production was marginal, whereas a high dosage of 0.6 g/g TS increased CH4 content by at least 10% and improved yield by 35–52%. ANOVA analysis indicated that biochar dosage level significantly influenced CH4 yield, while pyrolysis temperature (400 °C vs. 500 °C) and catalyst (20 wt% K3PO4 vs. 10 wt% K3PO4/10 wt% clinoptilolite) did not lead to significant differences in CH4 yield between the treatments. Correlation analysis results suggested that biochar's most impactful properties on methane yield would be dosage-adjusted specific surface area (or total surface area per unit volume of substrate) and aromaticity index. The findings underscore the potential of solid-digestate-derived biochar as a beneficial additive for anaerobic digestion and hence the sustainability of food waste management system. [ABSTRACT FROM AUTHOR]

Anaerobic co-digestion (AcoD) of fish sludge (FS) with food waste (FW), and fruit and vegetable waste (FVW) for biogas and methane production was optimised in small-scale bioreactors, and batch and semi-continuous pilot-scale digesters, under mesophilic (37 ℃) conditions. An experimental mixture design was first applied to small-scale biomethane potential (BMP) tests, to determine the optimal mixture proportions of the AcoD of FS, FW, and FVW that maximise the specific methane yield (SMY in NmLCH4 gVS−1). The optimal mixture proportion was 67%FS:18%FW:19%FVW (w/w), producing 401 mLCH4 gVS−1, which was 8 times higher than the SMY when FS was mono-digested (48 mLCH4 gVS−1). The SMY achieved in batch pilot-scale digesters were 70–82% of methane yields obtained in BMP tests under the same operating conditions, with stable biogas production and no apparent inhibition during the batch run. Semi-continuous operation of the pilot-scale digester was undertaken with organic loading rates (OLRs) of 1, 2, and 3 g V S L - 1 d - 1 , provided intermittently. However, the digester did not achieve stable biogas production at all of the evaluated OLRs, due to the intermittent feeding and accumulation of volatile fatty acids (VFAs): Improved process stability was achieved at an OLR of 2 g V S L - 1 d - 1 , compared to OLRs of 1 and 3 g V S L - 1 d - 1 . Optimisation of the AcoD process resulted in attractive biomethane yields from FS with FW and FVW co-feeds, indicating that producing biogas from co-digestion of FS with relevant substrates is a valuable managing tool for FS, while simultaneously providing renewable energy. The work provides novel data that elucidated optimal proportions in which to combine FS, FW and FVW to obtain optimal biogas production, and provided important new information relevant for the scale up and continuous operation of an AD process for treating FS. [ABSTRACT FROM AUTHOR]

A method to increase methane production in dairy cow manure (DCM) is to co-digest DCM with nutritious biomass. This study aimed to determine the methane yield during the anaerobic co-digestion of DCM and carica seeds meal (CSM). Four continuous stirred tank reactors were operated with treatments P0 (100% DCM), P1 (98% DCM and 2% CSM), P2 (96% DCM and 4% CSM), and P3 (94% DCM and 6% CSM). The results demonstrated that the presence of CSM as a co-substrate of DCM significantly increased (p

Biogas is an important renewable energy resource that has been considered as carbon neutral. The advantage that it can also reduce volumes of biowaste makes it an attractive option for secondary source of energy. In this scenario, large amounts of banana wastes are observed around the world with minimum work in anaerobic digestion. Hence, the present study demonstrates the anaerobic digestion of banana pseudo stem (BP) and cow dung (CD) feedstock by co-digesting them in different proportions (5 levels of BP – 0%, 30%, 50%, 70%, and 100%) and varying digester temperatures (3 levels: 42.5 °C, 45 °C, and 47.5 °C). Batch scale 1 liter feedstocks are prepared and digested for a period of 30 days. Initial studies suggested that the optimal temperature for digesting BP is between 40 and 50 °C which falls in the transition of mesophilic and thermophilic range. At all the digester temperatures, pure BP feedstock produced an average of 74% lower biogas as compared to CD feedstock. However, co-digesting CD with about 30% BP had a negligible loss in biogas production (1.2%). Further experimental data was subjected to regression, ANOVA, and optimization analyses. The optimization study results reveal that more than 5000 ml/liter of feedstock can be obtained for BP feedstock within 30-40% proportions if the temperature is maintained between 45 to 47 °C.

Anaerobic digestion (AD) offers a sustainable solution for clean energy production, with the potential for significant revenue enhancement through enhanced decision-making. However, the complexity and limited flexibility of AD systems pose challenges in developing reliable optimisation methods. Changing feeding strategies provides opportunities for efficient feedstock utilisation and optimal gas production, especially in volatile gas markets.To provide better decision-making tools in AD for energy production, we propose an integrated site model for the dynamic behaviour of the AD process in a biomethane-to-grid system and optimise production based on predicted gas prices. The model includes methods for optimal feed co-digestion strategies and integrates these results into a scheduling model to identify the optimal feedstock acquisition, feeding pattern, and potential gas storage operation considering feedstock availability, properties, sustainability, and fluctuating gas demand under different pricing variations.The methodology was tested on a 150 tonnes per day farm-scale AD plant in the UK, processing energy crops and manure considering both environmental (global warming potential) and economic objectives. The results showed strong adaptability of the proposed feeding schedule to the general trend of gas prices over time. To address the challenge of immediate price peaks, typically unattainable due to the system's sluggish behaviour and high retention times, the impacts of on-site storage were explored, leading to annual revenue increases ranging from 2 % to 7.4 %, depending on the pricing scheme, which translates to a significant boost in terms of revenue.

Study’s Novelty/Excerpt • This study uniquely evaluates the biogas optimization potential of various locally sourced substrates, including cow dung, poultry dung, human, and pig manure, through a comparative analysis over a 15-day period using custom-made biodigesters. • The research reveals that poultry dung yields the highest gas production, significantly outperforming other substrates with a gas production ratio of 0.20 on day 15, indicating its superior effectiveness. • These findings contribute valuable insights into substrate efficiency for biogas production, suggesting poultry dung as a highly effective substrate and proposing co-digestion strategies to further enhance biogas yields. Full Abstract This research aimed to investigate the utilization of various locally sourced substrates in the biogas optimization process and compare the gas yield to determine the most efficient domestic substrate. The samples tested included cow dung, poultry dung, human, and pig manure. A comparative analysis of gas production over a 15-day period was carried out at 3-day intervals using four custom-made biodigesters with batch culture fermentation. The findings revealed that digester 4, utilizing poultry dung, exhibited the highest gas output. The gas production ratios for human, cow, pig, and poultry dung on day 15 were 0.10:0.11:0.12:0.20, equating to percentages of 18.86%, 20.78%, 22.64%, and 37.73% respectively. The notably higher percentage for poultry dung suggests its superior effectiveness as a substrate for biogas production. Alternatively, the co-digestion of cow and/or poultry dung could be considered as a strategy to enhance biogas production.

Bioplastics have garnered substantial interest as alternatives to conventional petroleum-based plastics. However, their management and conversion to biogas continues to be significantly challenging. In this study, we evaluated the suitability of various plastics for hydrolysis at 160 °C for 12 h using different solvents. The biogas yield (BGY) of the monomers constituting these plastics and the obtained plastic hydrolyzates was comprehensively evaluated. When water was used as a solvent, 100 % hydrolysis of polylactic acid (PLA) and polybutylene succinate (PBS) was observed. When polybutylene adipate co-terephthalate (PBAT) and polyhydroxybutyrate (PHB) were hydrolyzed with water, the degradation ratio was approximately 30 %; however, using an aqueous lactic acid solution as a solvent improved the degradation ratio to 78 % and 100 %, respectively. In the BGY test of the plastic hydrolyzates, the biogas volumes derived from the hydrolyzates were 563, 461, 337, and 573 mL/g COD-added for PLA, PBS, PBAT, and PHB, respectively. With 1,160 gCOD/L waste PLA hydrolyzate, continuous co-digestion of sewage sludge and the hydrolyzate was conducted. Organic loading rates of sewage sludge and the hydrolyzate were 2.3 and 2.4 gCOD/L/d, respectively. The operation was stable and the methane production volume from the PLA hydrolyzate was 414 L/kgCOD-added. Using highly concentrated PLA hydrolyzate, the hydraulic retention time was 19.3 days, which was only 0.7 days shorter than that of anaerobic digestion of sewage sludge only (20 days). Therefore, highly concentrated PLA hydrolyzate maintains the retention time of normal sewage sludge digestion. Conclusively, the present study has crucial practical implications for plastic waste management.

The rise of the global population and improving living standards have increased food demand, imposing significant pressure on agricultural systems. As a result, substantial quantities of organic by-products rich in lignocellulose, termed organic agricultural biomass (OAB), are produced. These materials, rich in cellulose, hemicellulose, and lignin, provide environmental and economic difficulties if not treated properly. Conventional animal feed cannot adequately digest OAB owing to its structural complexity, restricting its effectiveness. Pretreatment strategies have become vital for altering the lignocellulosic structure of OAB, improving enzymatic hydrolysis, and transforming complicated polysaccharides into fermentable sugars. These techniques-physical, chemical, physico-chemical, and biological enhance fibre degradation, promote nutrient extraction, and adhere to circular economy principles. Recently, black soldier fly larvae (BSFL, Hermetia illucens L.) have shown potential as a recycling agent, particularly within EU regulatory frameworks, for converting agri-food by-products into nutrient-rich feed for livestock. This research examines the integration of pretreatment techniques with BSFL technology to recycle lignocellulose-rich by-products, highlighting the creativity in merging these methods to enhance nutrient conversion. The results indicate a sustainable approach to waste valorisation, mitigating the environmental effects of lignocellulosic by-product management while providing economic advantages. This interdisciplinary approach shows potential for sustainable agriculture and bio-economies, enhancing resource recovery via nature-based, circular solutions. Future research should concentrate on pretreatment methods for various biomass compositions and developing BSFL-rearing substrates as a viable recycling agent.

The global dependency on the depleted fossil fuels has led to the quest for acquiring alternative energy sources. Different types of waste material are generated at a high rate and tapping into their use for greener, alternative energy production is an option. The mesophilic anaerobic co-digestion of fruit and vegetable waste and wastewater treatment plant sewage sludge experiments were conducted using ultrasonic pretreated substrates. Sonication exposure times from 0 to 45 min were selected for the experiments. An automatic methane potential test system (BMP) was used to determine the production rate of biomethane of the fruit and vegetables waste containing 60% fruit and 40% vegetables. The highest cumulative methane production of 238 mL g−1 VS was achieved at sonication time exposure of 45 min. It was observed that an increase in ultrasonic sonication exposure time, improved methane yield. The resulting experimental data was fitted with the modified Gompertz, co-digestion modified Gompertz, original Richards, modified Richards and co-digestion modified Richards models. IBM SPSS Statistics software was used for curve fitting and the estimation of the models' kinetic parameters. The modified Gompertz and Richards models showed higher goodness fit, both with R2 of 0.93 and modified Richards models did not produce a good fit for the data, with R2 of 0.7. The developed co-digestion models considered a combination of substrates that were easily digested as well as complex substrates that required multiple steps of digestion. The results show that the co-digestion modified Gompertz model had a goodness of fit of 0.98. Co-digestion modified Richard's model perfectly fit the experimental data, with R2 of 1. Both the co-digestion modified models are recommended due to their fitting performance. Fruit and vegetable waste comprise multiple substrates including simple sugars that digest readily and much more complex cellulose substrates that require more steps to digest and requiring the second step of digestion after undergoing hydrolysis. Both models took that into account. The aim of this study was to evaluate the suitability of the Gompertz and Richards model in the co-digestion of fruit and vegetables waste with sludge, as well as to develop co-digestion models for the substrates at hand. [ABSTRACT FROM AUTHOR]

Anaerobic co‐digestion using an anaerobic dynamic membrane bioreactor (AnDMBR) can separate the sludge retention time and hydraulic retention time, retaining the biomass for efficient degradation and the use of less expensive large pore‐size membrane materials and more sustainable dynamic membranes (DMs). Therefore, anaerobic co‐digestion of toilet blackwater (BW) and kitchen waste (KW) using an AnDMBR was hypothesized to increase the potential for co‐digestion. Here, the efficiency and stability of AnDMBR in anaerobic co‐digestion of toilet BW and KW were investigated. DM morphology and structural characteristics, filtration properties, and composition, as well as membrane contamination and membrane regeneration mechanisms, were investigated. Average daily biogas yields of the reactor in two membrane cycles before and after cleaning were 788.67 and 746.09 ml/g volatile solids, with average methane content of 66.64% and 67.27% and average COD removal efficiencies of 82.03% and 80.96%, respectively. The results showed that the bioreactor obtained good performance and stability. During the stabilization phase of the DM operation, the flux was maintained between 43.65 and 65.15 L/m2/h. DM was mainly composed of organic and inorganic elements. Off‐line cleaning facilitated DM regulation and regeneration, restoring new Anaerobic morphology and structure. Practitioner Points: High efficiency co‐digestion of BW and KW was realized in the DMBR system.Average daily biogas yields before and after membrane cleaning were 788.67 and 746.09 ml/g volatile solids.Off‐line cleaning facilitated DM regulation and regeneration as well as system stability.The flux was maintained between 43.65 and 65.15 L/m2/h during operation. [ABSTRACT FROM AUTHOR]

[Display omitted] • Using statistics provided best anaerobic digestion conditions for cattle manure. • The most effective pretreatment was thermal treatment at 129.3℃ for 49.6 min. • Optimal mixing ratio of cattle manure, food waste, and pig manure was 30.5:42.5:27. • The ideal co-digestion condition substantially improves synergy effect and stability. This study investigated the optimal pretreatment condition and mixture ratio of cattle manure (CM) for its efficient anaerobic co-digestion (AcoD) with food waste (FW) and pig manure (PM). The pretreatment performances of thermal (TM), microwave (MW), and ultrasound (US) technologies and the AcoD performance were statistically and experimentally evaluated at various mixture ratios of CM, FW, and PM. The results revealed that the most effective pretreatment condition with the TM, MW, and US pretreatments was 129.3 °C for 49.6 min, 824.2 W for 7.3 min, and 418.0 W for 36.3 min, respectively. The best AcoD performance of optimally pretreated CM (PCM) was achieved when 30.5 % PCM was mixed with 42.5 % FW and 27.0 % PM. A long-term evaluation showed that the start-up rate for the anaerobic mono-digestion of PCM was 2.3 times faster than that of CM and the amount of methane produced was 4.7 times higher; process stability was thus preferentially maintained under a higher organic loading rate (OLR) (2.0 kg-VS/m3∙d). The start-up rate for the AcoD of PCM with FW and PM was 1.2 times higher than that of the AcoD of CM with FW and PM. Although the performance gap between the AcoD reactors after steady state was not significantly different, the PCM AcoD reactor provided a more stable operation under a higher OLR (5.0 kg-VS/m3∙d). This study demonstrates that the pretreatment and co-digestion of CM could significantly enhance the production of biogas and improve process stability. [ABSTRACT FROM AUTHOR]

This study focused on determining the effect of the inoculum to substrate ratio (ISR) on biogas production efficiency from the anaerobic co-digestion of two substrates: synthetic food waste and common reeds (Phragmites australis) that were ground and pre-treated using sodium hydroxide at a concentration of 2% to increase access to their cellulose. It also studied the role of different mixing ratios of the two substrates in improving the stability of the digestion process and increasing biogas production. A series of batch tests were carried out under mesophilic conditions using three ratios of ISR: 1:4, 1:2, and 1:1, and five substrate mixing ratios (synthetic food waste: pre-treated P. australis): 25:75, 50:50, 75:25, 100:0, and 0:100. The results showed low biogas production at the ISR 1:4 (21.58±0.00–44.46±0.01 mL/g volatile solid (VS) added), and the reactors suffered from acidification at the different substrates mixing ratios, while the biogas production increased at an ISR of 1:2, where the reactors with the substrate mixing ratio of 25:75 presented the highest biogas production (82.17±0.62 mL/g VS added), and the digestion process was stable. However, the reactors with substrate mixing ratios of 50:50, 75:25, and 100:0 suffered from acidification effects at this ISR. In contrast, at ISR of 1:1, the reactors did not expose to acidification inhibition at all the substrates mixing ratios, and the highest biogas production was found at synthetic food waste: pre-treated P. australis mixing ratios of 75:25 and 100:0 (76.15±1.85 and 82.47±1.85 mL/g VS added, respectively). [ABSTRACT FROM AUTHOR]

The European Union's energy policy favors increasing the share of renewable energy in total energy production. In this context, the co-digestion of various waste streams seems an interesting option. This study aimed to determine the effect of selected pretreatment methods on the efficiency and kinetics of the co-digestion process of poultry manure with sewage sludge and organic waste. This research was carried out in four stages: (1) the selection of the third component of the co-digestion mixture; (2) the determination of the most favorable inoculum-to-substrate ratio for the co-digestion mixture; (3) the selection of the most favorable pretreatment parameters based on changes in volatile fatty acids, ammonium nitrogen, extracellular polymers substances (EPS) and non-purgeable organic carbon (NPOC); and (4) the evaluation of anaerobic co-digestion based on the result of the BMP tests and kinetic studies. All the pretreatment methods increased the degree of organic matter liquefaction as measured by the NPOC changes. Waste with a high fat content showed the highest methane potential. The addition of grease trap sludge to feedstock increased methane yield from 320 mL/g VSadd to 340 mL/g VSadd. An optimal inoculum-to-substrate ratio was 2. The pretreatment methods, especially the thermochemical one with NaOH, increased the liquefaction of organic matter and the methane yield, which increased from 340 mL/g VSadd to 501 mL/g VSadd (trial with 4.5 g/L NaoH). [ABSTRACT FROM AUTHOR]

This study focuses on converting fruit waste into usable clean energy by an innovative, cost-effective anaerobic biodigester. The biodigester is designed to anaerobically digest various fruit wastes and starter inoculums of cow dung that are locally obtained. A batch vertical digester of 1000 liters capacity built of fiber with a phonematic agitator positioned in the center is used to improve mixing. The retention time is 30 days with a substrate of banana peels co-digested with mango and papaya peels individually in the ratio of 50:50. The combined wastes generated the biogas and the total quantity of biogas generated for all combined wastes over 21 days varies between 530L/day and 480L/day respectively. In this work, banana and mango peel (waste/water) split 50:50 gives a peak yield of 530L/day. The average ambient temperatures are kept in the range of 25°C to 35°C (i.e., mesophilic range). The pH range of 6.4 to 7.8 is consistently maintained and seems to be stable. Therefore, this proposed anaerobic digester would reduce the disposal of solid waste, and it is cost-effective. After cleaning, it is observed that the combined peels of bananas and papaya contained 91.95% of the estimated biogas and methane, which can be used to solve energy issues such as electricity production and cooking purposes. [ABSTRACT FROM AUTHOR]