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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]

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]

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]

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]

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.

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]

[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]

Today, the transition to renewable energy from conventional energy practices is more important than ever to establish energy security and mitigate climate change. The wastewater treatment plants (WWTP) consume a remarkable amount of energy and cause significant greenhouse gas emissions. The energy balance of WWTP can be improved by implementing energy-efficient applications such as anaerobic digestion. However, most of the existing WWTPs utilize only sewage sludge in conventional anaerobic digesters (CAD) which results in low biogas generation. Generally, co-digestion is indicated as an effective solution for the low biogas generation faced in mono-digestion. Moreover, recently, anaerobic membrane bioreactors (AnMBR) have been promoted as a prominent alternative to CADs. This paper overviews the current situation of co-digestion applications by AnMBRs for municipal WWTPs. Furthermore, the environmental and economic aspects of these applications were reviewed. Lastly, challenges and future perspectives related to the co-digestion applications by AnMBR were thoroughly discussed. [ABSTRACT FROM AUTHOR]

Methane production from co-substrate (CS) bio-digestion of cow, poultry and hog manure (CM: PM: HM) can be a potential energy alternative supply. The effect of the co-digestion of these CSs on biogas and methane yield was investigated in this study. Using the Taguchi fractional factorial design (TFFD) method, twenty-eight experiments with varying CSs mix ratios (CMR) were prepared including three experiments made up of the three individual substrates (ISs). Under mesophilic temperature conditions, controlled volatile solid concentration, and a thirty-day hydraulic retention time with all other physicochemical conditions kept unconstrained, the daily cumulative biogas and methane yields were collected and evaluated. Using these, the ultimate methane yields (Vmi∞p) were predicted using Richard's kinetic model. The relative Vmi∞p of the CSs with those of the ISs was compared to establish the synergistic properties of the CSs. The effects of the CSs interactions were also assessed using a quartic polynomial regression model. Furthermore, the optimal CMR necessary for producing the maximum methane yield was also predicted using the TFFD analysis. The Vmi∞ p range for the CMRs and ISs was (0.93-1.97) and (0.55-1.31) litres respectively indicating that higher methane yield production is possible with the use of CSs. However, to achieve this, the CMRs have to be carefully chosen. The relative Vmi∞ p was also found to be higher for all the CMRs further indicating the superiority of co-digesting the substrate rather than mono-digestion. The CSs interactions model showed that the addition of HM and PM produced the best and worst synergistic effects respectively. The TFFD analysis revealed an optimal CMR for CM: PM: HM to be 5:1:5. [ABSTRACT FROM AUTHOR]

The mushroom agroindustry generates a huge amount of waste from mushroom production (WMP). The composition of WMP is not standardized but differs mainly in terms of organic matter (OM) content and OM biodegradability. This makes WMP management, including anaerobic digestion (AD), a significant challenge. A potential solution could be co-digestion of WMP with municipal sewage sludge (SS), especially SS generated in small rural wastewater treatment plants (WWTPs). Therefore, this study investigated mesophilic methane production (MP) from WMP, SS, and mixtures of SS and WMP at ratios of 70:30, 50:50, and 30:70 (w/w OM). Even though the maximum cumulative MP from WMP was relatively low (approx. 60 NL/kg OM), co-digesting WMP with SS increased both MP and the methane content of the biogas: with 30%, 50%, and 70% shares of SS, MP increased almost 2, 2.5, and 3.3 times, and the methane content increased to 61%, 62%, and 64%, respectively. As the SS content was increased, the kinetic coefficients of MP and OM removal decreased (from 0.211 to 0.146 d−1 and from 0.215 to 0.152 d−1), whereas the initial rate of MP and of OM removal increased (from 12.5 to 36.8 NL/(kg OM·d) and from 0.51 kg OM/(m3·d) to 0.59 kg OM/(m3·d), respectively). The effectiveness of OM removal (EOMrem) was lowest with WMP only, at 46.6%. When the SS content of the mixtures was increased to 30%, 50%, and 70%, EOMrem also increased to 55.3%, 60.1%, and 64.9%, respectively. The relationship between maximal MP and the overall OM removed was such that both increased simultaneously. The higher values of EOMrem and, consequently, the lower final contents of OM with more effective MP indicate that the organics were degraded more efficiently. These results suggest that co-digestion may be a profitable solution for simultaneously utilizing both of these waste products, increasing the efficiency of biogas production to such an extent that it would be profitable to conduct AD on mushroom farms. This is a flexible approach that allows varying proportions of WMP and SS to be used, depending on the availability of both substrates and the energy needs of the mushroom farm. However, it should be borne in mind that a higher share of WMP results in lower gas productivity. [ABSTRACT FROM AUTHOR]

The purpose of the study was twofold. The first was to study the anaerobic digestibility and the biochemical methane potential (BMP) of brown grease (BG)- fats and oils collected from restaurants and similar food production facilities. The second objective was to investigate the effects of adding dry, food waste derived hydrochar to enhance the digestion process, specifically as a possible in situ agent to improve biogas quality. The BMP tests involved various BG loadings between 3 and 30 g BG/L. The results indicate that BG is highly digestible under anaerobic conditions with 354 mL CH4/g COD equivalent of BG at 1 atm and 35°C testing conditions, which translates into 28 million gasoline gallon equivalent (GGE) potential energy that could be recovered by anaerobically digesting or codigesting BG. The particular hydrochar investigated in this study did not show any potential to increase biogas CH4 content. [ABSTRACT FROM AUTHOR]

Brewery (BW) and dairy (DW) wastewater are two types of agro-industrial wastewater that are generated in large amounts and, therefore, should be treated effectively and in an environmentally beneficial manner. Both these wastewater types are characterized by a high COD, BOD5, and nutrient content, and conventional wastewater treatment methods such as an activated sludge process may prove to be inefficient due to the possibility of foaming, large biomass production, low activity at low temperatures, and risk of overloading the reactor with a load of organic pollutants. In the context of the described difficulties, anaerobic processes seem to be the best alternative. An interesting research area is the co-digestion of these wastewaters. However, this research direction, so far, has not been frequently reported. Given the gap in the current knowledge, this literature review aims to assess the possibility of BW and DW digestion in anaerobic reactors and provide up-to-date data on the post-treatment methods of effluent generated after the anaerobic digestion process. Despite numerous advantages, anaerobic treatment often requires post-effluent treatment to complete the treatment cycle. [ABSTRACT FROM AUTHOR]

This review paper delves into the intricate challenge of transforming microalgal biomass into biofuel through anaerobic digestion, elucidating its significance for sustainable energy production and waste management. Despite the promise anaerobic digestion holds, obstacles like inhibitory substances, process stability issues, and residue management complexities persist. Microalgal biomass, characterized by high biogas yields and carbon sequestration potential, emerges as a viable solution to enhance anaerobic digestion efficiency. Employing a comprehensive literature selection process, the review synthesizes recent studies to shed light on breakthroughs and pinpoint areas for future investigation. Key findings underscore advancements in microalgal biomass utilization, with strategic strain selection and innovative pretreatment methods resulting up to 25% increase in biogas production. Additionally, the assimilation of co-digestion techniques yields enhanced overall process efficiency. Microalgal biomass demonstrates remarkable carbon sequestration capabilities, sequestering up to 60% of CO2 during the anaerobic digestion process. Furthermore, the analysis reveals that despite inhibitory substances posing challenges, innovative approaches have reduced inhibition by 15%, promoting more stable and efficient digestion. Implications of the review findings stress the need to scale laboratory successes to industrial applications while maintaining environmental sustainability. Identified gaps include challenges in inhibitory substance management and process stability, with future research directions advocating for multidisciplinary approaches to unlock the full potential of microalgal biomass in anaerobic digestion. In conclusion, the review contributes significantly to understanding the intricate relationship between microalgal biomass and anaerobic digestion, highlighting the importance of continued research and development to address existing challenges and advance towards a more regenerative bioeconomy. [ABSTRACT FROM AUTHOR]

Traditionally, anaerobic digestion has been applied to mixed sludge, combining primary sludge (PS) with secondary sludge. However, recent research has unveiled the advantages of dedicated PS digestion due to its higher energy content. Anaerobic digestion (AD) of primary sewage sludge can offer a sustainable solution for managing sewage sludge while generating renewable energy. The present study provides a comprehensive examination of the current state of knowledge regarding the anaerobic digestion of PS. Co-digestion of PS with organic substrates, including food waste and agro-industrial residues, emerges as a promising approach to boost biogas production. Additionally, the utilization of additives such as glucose and clay minerals has shown potential in improving methane yield. Critical factors affecting AD, such as pretreatment methods, carbon-to-nitrogen (C/N) ratio, temperature, pH, volatile fatty acids (VFAs) levels, organic loading rates (OLR), inoculum-to-substrate ratio (ISR), and the role of additives, have been meticulously studied. Finally, this review consolidates existing knowledge to advance our understanding of primary sewage sludge anaerobic digestion, fostering more efficient and sustainable practices in sludge management and renewable energy generation. [ABSTRACT FROM AUTHOR]

Traditionally, anaerobic digestion has been applied to mixed sludge, combining primary sludge (PS) with secondary sludge. However, recent research has unveiled the advantages of dedicated PS digestion due to its higher energy content. Anaerobic digestion (AD) of primary sewage sludge can offer a sustainable solution for managing sewage sludge while generating renewable energy. The present study provides a comprehensive examination of the current state of knowledge regarding the anaerobic digestion of PS. Co-digestion of PS with organic substrates, including food waste and agro-industrial residues, emerges as a promising approach to boost biogas production. Additionally, the utilization of additives such as glucose and clay minerals has shown potential in improving methane yield. Critical factors affecting AD, such as pretreatment methods, carbon-to-nitrogen (C/N) ratio, temperature, pH, volatile fatty acids (VFAs) levels, organic loading rates (OLR), inoculum-to-substrate ratio (ISR), and the role of additives, have been meticulously studied. Finally, this review consolidates existing knowledge to advance our understanding of primary sewage sludge anaerobic digestion, fostering more efficient and sustainable practices in sludge management and renewable energy generation.

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 Hydrogen sulfide (H2S) is the most undesirable inorganic gas in biogas from anaerobic digestion (AD). However, H2S production in AD is complex and understanding of its processes is still limited. This study performed six controlled batch anaerobic co‐digestion experiments to investigate H2S production. Materials were obtained from four field anaerobic digester systems and co‐digestion feedstocks from agroindustry. An additional precipitation experiment was conducted to further examine H2S production dynamics. Digesters containing highly soluble, carbohydrate‐based wastes had a high H2S final specific production (FSP) value. Additionally, the FSP values were negatively correlated with the initial Fe(II):S ratios in the digester liquid of the batch tests. The precipitation experiment indicated that iron sulfide precipitation was preferred in the presence of an anaerobic community. The H2S production as a time series was successfully modeled using a generalized additive model (R2 > 0.82). This study revealed that sulfate, phosphorus, and iron concentrations are important predictors and potential inhibitors of H2S production in AD. Further examination of real‐time H2S modeling in AD is warranted.

Improper crop and animal waste management and disposal are now widely recognized as environmentally harmful practices. When crop waste is placed in landfills, greenhouse gases (GHG) like carbon dioxide (CO2) and methane (CH4) are created. In order to create the digestate for usage as bio-fertilizer from agricultural waste employing cow dung as an inoculum for 30 days of the hydraulic retention period, a 225L Polyethylene (PE) anaerobic digester was used in this study. Cassava peels, palm oil sludge, cow dung, and water were mixed in a 1:1:2:5.3 ratio. About 1.3 kilogram of crushed eggshells was added to keep the pH level within the range recommended for the anaerobic digestion process. In order to maintain mesophilic conditions during anaerobic co-digestion for enhanced organic fertilizer output, the greenhouse was used to regulate temperature. Since microbial populations flourish in friendly environments, the pH averaged 6.0 and the average slurry temperature was 34.76 oC during digestion. After 30 days of hydraulic retention time, a laboratory-scale elemental analysis of the digestate showed that the contents of nitrogen (N), phosphorus (P), and potassium (K) increased by 95%, 75%, and 93.8%, respectively. The anaerobic co-digestion of animal and agricultural waste has created digestate rich in NPK nutrients, but more research should be conducted to see whether the biofertilizer’s efficacy on fast-growing crops can be determined by measuring the number of harvests and height of the plants.

Biomethane produced from biogas which is the product of anaerobic digestion of organic wastes represents a promising option for decarbonizing the energy system, as it does not require adjustments to the natural gas network as would be required for fuels such as hydrogen. This study evaluates the viability of biomethane production from agricultural wastes for injection into gas pipelines in the Griffith regional area of New South Wales, Australia. It delves into the critical consideration of the degree of centralization and co-digestion strategies, taking into account the spatial distribution of feedstocks and associated transport costs. A comparative techno-economic analysis and an assessment of the greenhouse gas (GHG) reduction benefits from the biomethane production process were conducted for two cases: (1) a single centralized plant co-digesting various feedstocks from different locations; and (2) multiple distributed plants digesting a single feedstock located in the vicinity of the plants, together with a centralized upgrading and injection facility. Results indicate that a single centralized plant co-digesting food waste, poultry bedding materials and winery wastes is the most favorable scenario in terms of the levelized cost of energy (LCOE) and net carbon emissions saved. The LCOE for the best case is A$19.7/GJ (US$12.8/GJ), surpassing the average natural gas market price in Australia for the same year. However, with the volatility of natural gas prices in recent years, it is expected that biomethane could play an important role in providing a secure and reliable source of energy. The best case in terms of LCOE also offers the greatest potential for reducing greenhouse gas emissions, achieving a net reduction of −58.9 kt CO2-e/year if the generated biomethane could replace natural gas. The performance of the distributed biogas plants is less favorable due to higher capital and operating costs (LCOE is A$36.5/GJ (US$23.8/GJ)), as well as lower net carbon emissions (a net reduction of −33.9 kt CO2-e/year) and lower biomethane yield due to the single digestion of feedstocks and the intermittent operation of the plants throughout the year. The biomethane price shows the highest sensitivity to the biomass price. Receiving a gate fee of A$40/t for collection of the biomass would reduce the biomethane price to A$11.3/GJ (US$7.4/GJ), which would make it competitive with typical Sydney natural gas prices. The cost gap between natural gas and biomethane is expected to narrow over time as biomethane production technologies progress. Additionally, the supply risk, uncertainties and volatility of natural gas will make the investment in natural gas substitutes more favorable. The findings of this paper suggest that improved utilization of co-digestion using mixed feedstocks will be a critical factor. However, in Australia, like in many other countries, the biogas industry should be supported by the government with incentives like tax exemptions, investment subsidies or carbon credits for avoiding CO2 emissions.

The purpose of the study was twofold. The first was to study the anaerobic digestibility and the biochemical methane potential (BMP) of brown grease (BG)–fats and oils collected from restaurants and similar food production facilities. The second objective was to investigate the effects of adding dry, food waste derived hydrochar to enhance the digestion process, specifically as a possible in situ agent to improve biogas quality. The BMP tests involved various BG loadings between 3 and 30 g BG/L. The results indicate that BG is highly digestible under anaerobic conditions with 354 mL CH4/g COD equivalent of BG at 1 atm and 35°C testing conditions, which translates into 28 million gasoline gallon equivalent (GGE) potential energy that could be recovered by anaerobically digesting or co-digesting BG. The particular hydrochar investigated in this study did not show any potential to increase biogas CH4 content.

The characteristics of excess aerobic granular sludge, related to its structure and chemical composition, limit the efficiency of anaerobic digestion. For this reason, pre-treatment methods and compositions with other organic substrates are used. In earlier work, no attempt was made to intensify the methane fermentation of the excess aerobic granular sludge by adding fatty waste materials. The aim of the research was to determine the effects of co-digestion of pre-hydrodynamically cavitated aerobic granular sludge with waste fats on the efficiency of methane fermentation under mesophilic and thermophilic conditions. The addition of waste fats improved the C/N ratio and increased its value to 19. Under mesophilic conditions, the highest effects were observed when the proportion of volatile solids from waste fats was 25%. The amount of biogas produced increased by 17.85% and CH4 by 19.85% compared to the control. The greatest effects were observed in thermophilic anaerobic digestion at 55 °C, where a 15% waste fat content in volatile solids was ensured. This resulted in the production of 1278.2 ± 40.2 mL/gVS biogas and 889.4 ± 29.7 mL/gVS CH4. The CH4 content of the biogas was 69.6 ± 1.3%. The increase in biogas and CH4 yield compared to pure aerobic granular sludge anaerobic digestion was 34.4% and 40.1%, respectively. An increase in the proportion of waste fats in the substrate had no significant effect on the efficiency of methane fermentation. Strong positive correlations (R2 > 0.9) were observed between biogas and CH4 production and the C/N ratio and VS concentration. [ABSTRACT FROM AUTHOR]

Accurate prediction of biogas yield is crucial for optimizing waste-to-energy conversion systems in anaerobic co-digestion processes. In this study, a double input and single output (DISO) fuzzy mamdani model (FMM) was developed for the prediction of biogas yield in a pilot scale of 105-L mesophilic anaerobic sludge bio-digester. The input variables considered are the combination of cow dung and pig waste and the retention time (RT), while the output variable is the experimental biogas yield. Triangular Fuzzy Membership Functions (TFMF) were utilized to define the input and output datasets, and rules were derived from de-fuzzification. Comparative analysis between the FMM's predicted results and experimental values showcased its effectiveness in forecasting biogas yield during the anaerobic co-digestion of the hybrid wastes. Significantly, the FMM consistently produced results with low error values for the sample dataset, underscoring its accuracy even under stochastic conditions. This study emphasizes the FMM's ability to generate predictions with minimal deviations, offering superior results. As a prospect for future research, the implementation of hybrid algorithms may further enhance biogas yield prediction accuracy within waste-to-energy systems. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The co-digestion of untreated Napier grass (NG) and industrial hydrolyzed food waste (FW) was carried out in the batch reactor to investigate the effect of substrate ratios on biogas production performance. Two-stage anaerobic digestion was performed with an initial substrate concentration of 5 g VSadded/L and a Food to Microorganism Ratio (F/M) of 0.84. The 1:1 ratio of the NG and FW showed the optimum performances on biogas production yield with a value of 1,161.33 mL/g VSadded after 60 days of digestion. This was followed by the data on methane yield and concentration were 614.37 mL/g VSadded and 67.29%, respectively. The results were similar to the simulation results using a modified Gompertz model, which had a higher potential methane production and maximum production rate, as well as a shorter lag phase and a coefficient of determination of 0.9945. These findings indicated that the co-digestion of Napier grass and hydrolyzed food waste can enhance biogas production in two-stage anaerobic digestion.

Adopting waste-to-wealth strategies and circular economy models can help reduce biowaste and add value. For instance, poultry farming is an essential source of protein, and chicken manure can be converted into renewable energy through anaerobic digestion. However, there are a number of restrictions that prevent the utilization of chicken manure in bioenergy production. Here, we review the conversion of chicken manure into biomethane by anaerobic digestion with focus on limiting factors, strategies to enhance digestion, and valorization. Limiting factors include antibiotics, ammonia, fatty acids, trace elements, and organic compounds. Digestion can be enhanced by co-digestion with sludge, lignocellulosic materials, food waste, and green waste; by addition of additives such as chars, hydrochars, and conductive nanoparticles; and by improving the bacterial community. Chicken manure can be valorized by composting, pyrolysis, and gasification. We found that the growth of anaerobic organisms is inhibited by low carbon-to-nitrogen ratios. The total biogas yield decreased from 450.4 to 211.0 mL/g volatile solids in the presence of Staphylococcus aureus and chlortetracycline in chicken manure. A chlortetracycline concentration of 60 mg/kg or less is optimal for biomethanization, whereas higher concentrations can inhibit biomethane production. The biomethane productivity is reduced by 56% at oxytetracycline concentrations of 10 mg/L in the manure. Tylosin concentration exceeding 167 mg/L in the manure highly deteriorated the biomethane productivity due to an accumulation of acetate and propionate in the fermentation medium. Anaerobic co-digestion of 10% of primary sludge to 90% of chicken manure increased the biogas yield up to 8570 mL/g volatile solids. Moreover, chemicals such as biochar, hydrochar, and conducting materials can boost anaerobic digestion by promoting direct interspecies electron transfer. For instance, the biomethane yield from the anaerobic digestion of chicken manure was improved by a value of 38% by supplementation of biochar. [ABSTRACT FROM AUTHOR]

Hydrogen sulfide (H2S) is the most undesirable inorganic gas in biogas from anaerobic digestion (AD). However, H2S production in AD is complex and understanding of its processes is still limited. This study performed six controlled batch anaerobic co‐digestion experiments to investigate H2S production. Materials were obtained from four field anaerobic digester systems and co‐digestion feedstocks from agroindustry. An additional precipitation experiment was conducted to further examine H2S production dynamics. Digesters containing highly soluble, carbohydrate‐based wastes had a high H2S final specific production (FSP) value. Additionally, the FSP values were negatively correlated with the initial Fe(II):S ratios in the digester liquid of the batch tests. The precipitation experiment indicated that iron sulfide precipitation was preferred in the presence of an anaerobic community. The H2S production as a time series was successfully modeled using a generalized additive model (R2 > 0.82). This study revealed that sulfate, phosphorus, and iron concentrations are important predictors and potential inhibitors of H2S production in AD. Further examination of real‐time H2S modeling in AD is warranted. [ABSTRACT FROM AUTHOR]

The effects of co-digesting sewage sludge (SS) and horse waste (HW), the composition of HW, and the ratio of HW:SS were studied using two semi-continuous digesters of 9.5 L of working volume. These digesters were operated in parallel with the mono-digestion of SS in digester 1 (D1) and the co-digestion of SS and HW in digester 2 (D2). In digester 2, there were two phases of digestion (durations of 40 and 43 weeks, respectively). The composition of HW in the first phase was 85% wheat straw (WS), 14% wood chips (WC), and 1% horse manure (HM), with 99% wheat straw (WS) and 1% horse manure (HM) in the second phase. Variable ratios of HW:SS were studied in the digesters. The co-digestion of sewage sludge (SS) and horse waste (HW) produced more biogas than the mono-digestion of SS alone, with a maximum of 15.8 L·d−1, compared to 9 L·d−1 at the end of the experiment. When comparing the results obtained in both phases, the production of methane in phase 2 was 18 NmL·gVS−1 higher than in phase 1. This slight increase in methane yield could be linked to the absence of wood chips (WC), which is considered to have a diluting effect on methane production. Therefore, this study shows that an organic loading rate (OLR) of 4.8 kgVS·m−3·d−1, a ratio of HW:SS of 3, and a composition of HW (99% WS, 1% HM) should be respected in the actual experimental conditions for a well-functioning anaerobic digestion. [ABSTRACT FROM AUTHOR]

The effect of different inoculum-to-substrate ratios (ISRs) and feed mix (FM) ratios on the kinetics of methane production and yields during anaerobic digestion of spoiled silage mixture (SM) alone or co-digestion with cow manure (CM) was investigated in batch experiments at 37 °C. The silage mixture was prepared from spoiled silages of maize, lucerne and barley in equal proportions of 33% by wet weight. The effect of ISRs of 0.5, 1, 2 and 4 showed that methane yields increased with an increased ISR ratio. At ISRs of 1, 2 and 4, methane yields of 262.18 ± 14.96, 387.77 ± 14.43 and 482.23 ± 38.47 NmL CH4/gVSadded were obtained, respectively. Incubation at ISR 0.5 resulted in low methane yields (174.49 ± 9.29 NmL CH4/gVSadded) due to build-up of volatile fatty acids (VFAs). Further, co-digestion of spoiled SM with CM showed that the highest methane yields of 387.77 and 382.86 NmL CH4/gVSadded were obtained at SM:CM feed mix ratios of 100–0 and 75–25, respectively. The corresponding volatile solids (VS) removal rates were 72.80% and 70.82%, respectively. However, the best synergistic effect was noticed at a SM:CM = 50–50 feed mix ratio. Thus, this study shows that anaerobic digestion of spoiled silages is feasible and co-digestion of spoiled silage mixed with cow manure at a SM:CM feed mix ratio of 75–25 is recommended. [ABSTRACT FROM AUTHOR]

Wet anaerobic digestion is the most used stabilisation method in the world. However, it has some limitations resulting from the high hydration of the feed, which requires the construction of large-volume anaerobic digestion chambers, difficulty in managing of digested sludge (digestate), which requires dewatering and drying. For this reason, more worldwide attention is paid to the development of dry technologies, which is supported primarily by the possibility of working with higher organic loading, smaller reactor volume, and the minimum need for digestate dewatering. This study aimed to conduct mesophilic and thermophilic batch high-solids anaerobic digestion (HSAD) of sewage sludge (SS) with grease trap sludge (GTS) and algae biomass (AB). Additionally, to shorten the long digestion time, which is the bottleneck of the process, in this study, various pre-treatment methods were used. The effectiveness of the conditioning methods was assessed based on the results of the biochemical determination of the methane potential and the analysis of the kinetics of the process with the use of five kinetic models. The thermochemical pre-treatment method observed the most pronounced pre-treatment effect on the studied SS/GTS/AB mixture at mesophilic temperature. Its methane yield was 109.48 ± 0.00 N·mL-CH4/g-VS, which was 110% higher in comparison to the control (52.21 ± 0.00 N·mL-CH4/g-VS). High-solids co-digestion significantly increased lag phase time (more than 30 d). However, thermochemical pre-treatment improved that parameter by 26.3% compared to the control. [ABSTRACT FROM AUTHOR]

The appropriate rationing of NPK is a core problem in biofertilizer production. In this study, a 30-liter bench-scale anaerobic biodigester for biofertilizer production from solid waste was fabricated using galvanized steel sheet. About 4kg of chicken dung, 7.5 kg of wastewater treatment sludge, and 0.5 kg of banana peel are mixed, a total of 12kg, the substrate is then mixed with water in a ratio of 1:1. (w/w) 24 kg of the slurry is fed into the biodigester. The slurry is allowed to stay for 37 days at mesophilic temperature. The pH of the digestion is between 6-7, and the temperature is within the range of 25-34oC. The amount of total solid, moisture content, ash, and volatile matter of the feedstock after digestion decreases by about 31%,47%,67%, and 69%. Moreover, an increase in the amount of nitrogen content from 0.3783% to 0.6420%, phosphorous from 0.1903% to 0.2983%, and potassium from 0.1876% to 0.3153% was also observed. After digestion the biofertilizer produced has an appropriate ratio of 2:1:1. For the kinetic study, the specific growth was found to be 0.0098hr-1. Also, experimental data for microbial growth obtained from the study fitted the Monod model.

The objective of this work was to develop an automated anaerobic biodigester capable of operating in a semi-continuous or batch system for biogas production. Low biodegradability biomass has little efficiency in the production of biogas by anaerobic digestion processes and an efficient alternative is the use of bioprocesses in semi-continuous system. Two experiments were carried out in the same proportions but in different processes, and all control and automation parameters were tested and evaluated. For testing, mixtures of organic waste, anaerobic sludge (inoculum) and raw sewage without any treatment from the sewage treatment plant, in mesophilic phase (37 °C), were used during the 60 days of experiment. The semi-continuous system showed the greatest reduction in organic matter, expressed by the removal of 80.7% Total Solids Volatile (TVS) and the greatest volume (68.5 L) and methane percentage (78.5%). Finally, with these and other results found, it is possible to conclude that the biodigester developed for semi-continuous system, with the automation and control system, was satisfactory for the reduction in organic matter and biogas production. In addition, all operating system worked properly and with the use of current, low-cost technologies, the application and development on a larger scale becomes viable in the future.

Indonesia has abundant oil palm empty fruit bunches (OPEFBs). However, high lignin content in OPEFBs may hinder their valorisation to bioenergy resources, as its degradation by microorganisms is rate-limiting. This paper aims to review OPEFB as feedstock in anaerobic digestion (AD) systems and sustainable strategies to enhance methane yield. This paper provides a comprehensive review of the availability of OPEFB, the prospective of AD technology, and compares various biological pre-treatment and co-digestion strategies for superior AD process. Improving the value-added benefits from OPEFBs and simultaneously making pre-treatment processes more sustainable is critical to wider application. Several scenarios were proposed by combining multi-stage pre-treatment of physical and mushroom cultivation pre-treatment prior to AD. This paper presents an original approach to establishing a commercially viable and sustainable AD of OPEFBs in Indonesia by integrating multi-product biorefinery and a circular economy. Further investigation is required to ensure cost-effective and eco-friendly configurations. Abbreviations: ABR: Anaerobic Baffled Reactor; AD: Anaerobic Digestion; AF: Anaerobic Filter; AFEX: Ammonia Fibre Expansion; AI: Artificial Intelligence; AnMBR: Anaerobic Membrane Bioreactor; ANN: Artificial Neural Network; ASP: Activated Sludge Process; CMM: Cattle Manure and Maize Silage; COD: Chemical Oxygen Demand; CPO: Crude Palm Oil; CPW: Cocoa Pods Waste; CSTR: Continuous Stirred-Tank Reactor; DH: Dry Husk; DM: Dry Matter; DMF: 2,5-dimethylfuran; EM: Effective Microorganisms; EGSB: Expanded Granular Sludge Bed; FBR: Fluidised Bed Reactors; FFB: Fresh Fruit Bunch; FTIR: Fourier-Transform Infrared Spectroscopy; GHG: Greenhouse Gasses; HRT: Hydraulic Retention Time; IC: Internal Circulation Reactor; IoT: Internet of Things; Lac: Laccase Enzyme; L-AD: Liquid-AD; LiP: Lignin Peroxidase; LRAD: Low-Rate AD; MARS: Multivariate Adaptive Regression Splines; MCC: Microcrystalline Cellulose; MDF: Medium-Density Fibreboard; MEMR: Ministry of Energy and Mineral Resources, Republic of Indonesia; ML: Machine Learning; MnP: Manganese Peroxidase; MPA: Marine Predators Algorithm; MSW: Municipal Solid Waste; OFMSW: Organic Fraction of Municipal Solid Waste; OLR: Organic Loading Rates; OPEFBs: Oil Palm Empty Fruit Bunches; OPF: Oil Palm Fibre; OPKS: Oil Palm Kernel Shell; OPMF: Oil Palm Mesocarp Fibre; OPT: Oil Palm Trunk; P(3HB): Poly(3-Hydroxybutyrate); PHA: Polyhydroxyalkanoate; PLTBg: Biogas Power Plants; POM: Palm Oil Mill; POME: Palm Oil Mill Effluent; SCG: Spent Coffee Grounds; SRF: Solid Refused Fuel; SRT: Solids Retention Time; SS-AD: Solid-State AD; TS: Total Solid; TSI: Torrefaction Severity Index; UASB: Up-flow Anaerobic Sludge Blanket; VFA: Volatile Fatty Acids; VP: Versatile Peroxide; VS: Volatile Solid; W2E: Waste-to-Energy.

Supplementation with iron oxide nanoparticles has been suggested as a potential method for improving energy generation through anaerobic digestion, specifically by enhancing the rate of methane production. This investigation examined the effects of iron oxide (Fe3O4) nanoparticles (NPs) on anaerobic co-digestion of cow manure (CM) and sewage sludge (SS) through batch testing conducted under mesophilic conditions (35 °C) using a RESPIROMETRIC Sensor System 6 Maxi—BMP (RSS-BMP). The use of Fe3O4 nanoparticles at doses of 40, 80, 120, and 160 mg/L (batches M1, M2, M3, and M5) was studied. The use of 160 mg/L Fe3O4 nanoparticles in combination with mixtures of different ratios (M4, M5, and M6) was further investigated. The findings indicate that the addition of Fe3O4 nanoparticles at a concentration of 40 mg/L to anaerobic batches did not significantly impact the hydrolysis process and subsequent methane production. Exposing the samples to Fe3O4 NPs at concentrations of 80, 120, and 160 mg/L resulted in a similar positive effect, as evidenced by hydrolysis percentages of approximately 94%, compared to 60% for the control (C2). Furthermore, methane production also increased. The use of Fe3O4 nanoparticles at a concentration of 160 mg/L resulted in biodegradability of 97.3%, compared to 51.4% for the control incubation (C2). Moreover, the findings demonstrate that supplementing anaerobic batches with 160 mg/L Fe3O4 NPs at varying mixture ratios (M4, M5, and M6) had a significant impact on both hydrolysis and methane production. Specifically, hydrolysis percentages of 94.24, 98.74, and 96.78% were achieved for M4, M5, and M6, respectively, whereas the percentages for the control incubation (C1, C2, and C3) were only 56.78, 60.21, and 58.74%. Additionally, the use of 160 mg/L Fe3O4 NPs in mixtures M4, M5, and M6 resulted in biodegradability percentages of 78.4, 97.3, and 88.3%, respectively. In contrast, for the control incubation (C1, C2, and C3) biodegradability was only 44.24, 51.4, and 49.1%. [ABSTRACT FROM AUTHOR]

Modern society is characterised by its outstanding capacity to generate waste. Lignocellulosic biomass is most abundant in nature and is biorenewable and contains energy sources formed via biological photosynthesis from the available atmospheric carbon dioxide, water, and sunlight. It is composed of cellulose, hemicellulose, and lignin, constituting a complex polymer. The traditional disposal of these types of waste is associated with several environmental and public health effects; however, they could be harnessed to produce several value-added products and clean energy. Moreover, the increase in population and industrialisation have caused current energy resources to be continuously exploited, resulting in the depletion of global fuel reservoirs. The overexploitation of resources has caused negative environmental effects such as climate change, exacerbating global greenhouse gas emissions. In the quest to meet the world's future energy needs and adequate management of these types of waste, the anaerobic digestion of lignocellulosic biomass has remained the focus, attracting great interest as a sustainable alternative to fossil carbon resources. However, substrate characteristics offer recalcitrance to the process, which negatively impacts the methane yield. Nevertheless, the biodigestibility of these substrates can be enhanced through chemical, physical, and biological pretreatment methods, leading to improvement in biogas yields. Furthermore, the co-digestion of these substrates with other types and adding specific nutrients as trace elements or inoculum will help to adjust substrate characteristics to a level appropriate for efficient anaerobic digestion and increased biogas yield. [ABSTRACT FROM AUTHOR]

During the processing of raw agricultural materials from the primary sector, large quantities of by-products with high chemical energy content are produced. Some of these are olive mill wastewater (OMW), cheese whey (CW), and liquid cow manure (LCM). Anaerobic digestion is a promising, environmentally friendly process for the energy valorization of agro-industrial and livestock by-products. The purpose of this study was the mathematical modeling of anaerobic digestion in batch systems, aiming to quantify possible synergies occurring between complementary substrates. The analysis was based on using biochemical methane potential data to predict the optimum hydraulic retention time (HRT) under steady-state conditions of continuous systems, for different substrate ratios. The objective function for HRT optimization was based on maximizing the process profit and included technoeconomic parameters, allowing the comparison of the different substrate ratios that can be used in the feedstock. The co-digestion with a mixture ratio of OMW:LCM equal to 70:30 proved very satisfactory for the sustainability of the process, exhibiting a maximum net profit of 16 €/m3 reactor /d for a plant capacity of 10 m3 feed /d. [Display omitted] [ABSTRACT FROM AUTHOR]

Considering the high rates of atmospheric pollution caused by the exploitation of fossil fuels on planet Earth, the generation of new, affordable, and economical alternative fuels to minimize this problem is a widely studied initiative. Biogas production from organic matter represents one of the most promising initiatives in this field. For this reason, this publication presents a study of the influence of the physicochemical and operational parameters considered in the anaerobic digestion models, which study the yield and quality of the biogas obtained by route. The operating parameters analyzed from the scientific literature such as temperature, pH, hydraulic retention time, carbon/nitrogen ratio, among others, can be used to perform comparisons between different techniques, which allows varying raw materials, establishing operating conditions, and scaling processes. The results indicate that there are different types of substrates, which are associated with considerable yield percentages; as is the case of pig and cattle manure, carbon/nitrogen ratios were established according to the raw material and the most important reactions of anaerobic digestion. The data of the review were compared with those obtained in the laboratory of transformation of organic materials of the Universidad del Atlántico, thus obtaining a great similarity in most of the reported data. [ABSTRACT FROM AUTHOR]

Anaerobic co-digestion technology is widely used for biogas generation from organic wastes. In this study, co-digestion of petroleum oily sludge (POS) for biogas production in bench-scale anaerobic digesters at thermophilic conditions was investigated. The effects of inoculum type on the biogas production were considered. Three types of inoculums were examined individually for the co-digestion of POS which were; poultry manure, cattle manure, and cow dung. The results revealed that the biogas production from poultry manure, cattle manure, and cow dung exceeded its production from uninoculated POS by 64.6, 20.94 and 6.1% respectively. Effect of C/N on the co-digestion process was also considered in this study. Modified Gompertz model was applied to describe the kinetic of the co-digestion process. The predicted and experimental results of biogas generation were fitted well with coefficients of determination > 0.96 indicating appropriate conditions of the co-digestion process. Statistical analysis was performed to estimate if there were significant differences in terms of cumulative biogas yield. A significance level value of < 0.05 was obtained. [ABSTRACT FROM AUTHOR]