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This paper deals with a model of chemostat with two cross‐feeding species and involving two inhibitions. The excess of hydrogen inhibits the growth of acetogenic bacteria which, in turn, inhibit the growth of methanogenic hydrogenotrophic bacteria. The model is described by a system of four ordinary differential equations. We established the conditions of existence and stability of equilibria with respect to the operating parameters which are the dilution rate and the input substrate concentrations of the species of the model, then we illustrate the operating and bifurcation diagrams. This technique makes it easy to interpret different regions of operating diagrams. Inhibitions let some regions of stability rise and others vanish. [ABSTRACT FROM AUTHOR]

Anaerobic digestion is a promising technology for the treatment of food waste (FW) but it requires optimization to improve its performance. This study investigated whether combining the addition of biochar with lipase pretreatment could improve the anaerobic digestion of FW. The results showed that biochar stimulated the release of soluble substances, resulting in an increase in the methane yield of groups with added biochar by 16.24% to 19.36% in comparison with the group without biochar. Lipase pretreatment substantially shortened the fermentation time required to complete the anaerobic digestion, from 15 to 9 days. Lipase pretreatment further improved microbial abundance and promoted the enrichment of functional microbes in the anaerobic digestion of FW mediated by biochar. It also changed the methane production pathway from acetotrophic to hydrogenotrophic, thereby ensuring the stability of the anaerobic digestion system in the presence of a high ammonia nitrogen concentration. [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]

Energy security is a critical global challenge in the transition to sustainable development. Anaerobic digestion (AD) offers a promising renewable energy solution that mitigates environmental impacts. Algae, as biomass feedstock, have shown significant potential for bioenergy production; however, their complex chemical composition poses challenges to the efficiency of the AD process. To address these limitations, various pretreatment methods have been applied to enhance biogas production. In this study, we performed a comprehensive meta‐analysis to evaluate the effects of different pretreatments on methane (CH₄) yields from both microalgae and macroalgae. Our results demonstrate that biological, physical, and combined chemical–physical pretreatments significantly improve CH₄ production in microalgae, with increases of up to 141%, 125%, and 151%, respectively. For macroalgae, physical pretreatments were the most effective, leading to a 129% increase in CH₄ yield. We also estimate that utilizing just 10% of the global algal biomass production (3.6 Mt) could generate over 5.5 TWh y−1 of energy. This potential could be doubled with the application of appropriate pretreatment strategies. These findings highlight the role of algae in advancing renewable energy production and contribute to the growing body of knowledge on optimizing AD processes for cleaner energy generation. [ABSTRACT FROM AUTHOR]

There is a need for research into clean alternative energy sources to meet future energy requirements. Renewable natural gas (RNG) can assist in fulfilling a growing projected demand for natural gas in a sustainable manner. This study focuses on a techno‐economic analysis (TEA) and a life cycle assessment (LCA) for the co‐digestion of manure with pretreated prairie biomass. This process offers higher biogas yields and an additional co‐product, hydroxycinnamic acid (HCA), to decrease the minimum fuel selling price (MFSP) of RNG. The plant produces between 524 000 GJ year−1 and 1 176 000 GJ year−1 of RNG in the five modeled scenarios. The MFSP of RNG for scenarios where biomass pretreatment occurs is estimated to be between $15.87 GJ−1 and $18.94 GJ−1. The MFSP for the scenario where no pretreatment occurs is estimated to be $21.21 GJ−1. The global warming potential results range from −7.30 kg CO2e GJ−1 to 21.59 kg CO2e GJ−1. Sensitivity and uncertainty analyses are also completed. [ABSTRACT FROM AUTHOR]

The advantages of implementing demand side management (DSM) strategies in biogas production are explored. Specifically, the influence of agitation intervals on biogas production and the economic advantages of DSM in fermenter agitation are examined. The model‐based study highlights the detrimental effects of insufficient agitation, such as reduced active reaction volume and diminished biogas yield. The article further delves into the optimal agitation intervals corresponding to different electricity price levels and assesses the implications of DSM on biogas production. Results substantiate that such strategies, particularly at high and low electricity prices, can increase profit while reducing greenhouse gas emissions. [ABSTRACT FROM AUTHOR]

Pyrolysis of lignocellulosic biomass commonly produces syngas, a mixture of gases such as CO, CO2 and H2, as well as an aqueous solution generally rich in organic acids such as acetate. In this study, we evaluated the impact of increasing acetate shock loads during syngas co‐fermentation with anaerobic microbiomes at different pH levels (6.7 and 5.5) and temperatures (37°C and 55°C) by assessing substrates consumption, metabolites production and microbial community composition. The anaerobic microbiomes revealed to be remarkably resilient and were capable of converting syngas even at high acetate concentrations of up to 64 g/L and pH 5.5. Modifying process parameters and acetate loads resulted in a shift of the product spectrum and microbiota composition. Specifically, a pH of 6.7 promoted methanogens such as Methanosarcina, whereas lowering the pH to 5.5 with lower acetate loads promoted the enrichment of syntrophic acetate oxidisers such as Syntrophaceticus, alongside hydrogenotrophic methanogens. Increasing acetate loads intensified the toxicity of undissociated acetic acid, thereby inhibiting methanogenic activity. Under non‐methanogenic conditions, high acetate concentrations suppressed acetogenesis in favour of hydrogenogenesis and the production of various carboxylates, including valerate, with product profiles and production rates being contingent upon temperature. A possible candidate for valerate production was identified in Oscillibacter. Across all tested conditions, acetate supplementation provided additional carbon and energy to the mixed cultures and consistently increased carboxydotrophic conversion rates up to about 20‐fold observed at pH 5.5, 55°C and 48 g/L acetate compared to control experiments. Species of Methanobacterium, Methanosarcina and Methanothermobacter may have been involved in CO biomethanation. Under non‐methanogenic conditions, the bacterial species responsible for CO conversion remain unclear. These results offer promise for integrating process streams, such as syngas and wastewater, as substrates for mixed culture fermentation allowing for enhanced resource circularity, mitigation of environmental impacts and decreased dependence on fossil fuels. [ABSTRACT FROM AUTHOR]

The influence of the inoculum‐to‐substrate ratio (ISR) on anaerobic digestion (AD) of biomass in terms of methane yield and microbial community, was explored in this paper. The level of ISR can affect the AD performance in several ways. At extremely low ISR, volatile fatty acids (VFAs) accumuate, while inhibition occur at higher level of ISR. An ISR ranging from 1.0–2.0 was found optimal resulting in higher methane yield, organic matter removal and VFA degradation. Furthermore, a high ISR (2.0–4.0) is favourable to methanogenesis, while a lower ISR (<1.0) is prone to irreversible acidification. The range of ISR can shift the methanogenic pathway of AD to favour an acetoclastic or hydrogenotrophic response, indicated by the enriched group of microorganisms. The genus Methanosaeta (acetoclastic) and Methanobacterium (hydrogenotrophic) are the most enriched methanogens across all ISRs, while Firmicutes, Bacteroidetes, Proteobacteria and Spirochaetae are dominant in the bacterial community. Additionally, the interplay of substrate biodegradability and ISR potentially affects AD performance. Finally, novel equations are developed and proposed for characterizing the quantity of inoculum and substrate. [ABSTRACT FROM AUTHOR]

Promoting the bioeconomy to aid in the achievement of sustainability goals has increased demand for biomass as feedstock. Residual biomass from agricultural production is an attractive option, as it is a by‐product that does not compete with food production. However, crop residues are important for the preservation of soil quality, especially for the maintenance of soil organic carbon. Therefore, their use can conflict with environmental goals and initiatives that aim to preserve soil fertility and carbon stocks. Nevertheless, the adoption of intermediate crops could compensate for the negative effects of crop residue removal. Moreover, if crop residues are used for a bioeconomy pathway such as biogas production, the resulting digestate derived from the anaerobic digestion process could be returned to the soil, providing an input of highly recalcitrant carbon. In this study, we modeled the effects of removal of crop residues, the cultivation of intermediate crops, and the application of digestate on Swedish soil organic carbon stocks. Our results suggest that the inclusion of intermediate crops could raise the carbon stocks at equilibrium by an average of 1.93 t C ha−1 (~3% increase) with a notable spatial variation. Digestate application showed a higher average increase (3.3 t C ha−1, ~5%) with an even higher variation. The removal of crop residues was detrimental in some areas, resulting in a loss of carbon, which could not be compensated for entirely by the introduction of intermediate crops or digestate recycling. Combining these two practices showed overall positive effects on soil organic carbon stocks; however, the results cannot be generalized at any spatial location, and we emphasize the importance of assessments tailored to local conditions. [ABSTRACT FROM AUTHOR]

This study introduces a straightforward batch‐mode bioreactor for the production of biogas from two waste sources: animal slaughterhouse solid waste and fruit and vegetable solid waste, as well as poultry slaughter solid waste and fruit and vegetable solid waste. To measure the efficiency of methane and carbon dioxide (CO2) production, the system was experimentally studied for 40 days, investigating different carbon‐to‐nitrogen (C/N) ratios: 20, 30, and 40. The highest biogas and methane contents were observed at a C/N ratio of 30. The poultry slaughterhouse waste (SHW) and fruit and vegetable waste (FVW) combination resulted in an impressive 201.7 L of biogas, with 149.2 L of pure methane. Similarly, the animal SHW and FVW mixture resulted in 241 L of biogas, containing 182.7 L of valuable methane. Recognizing the complex nature of factors that impact the anaerobic digestion (AD) process, this study employed kinetic models and artificial neural networks (ANNs) combined with three optimizers: Differential Evolution (DE), Bacterial Foraging Optimization (BFO), and the Dragonfly Algorithm (DA). The simulation data revealed that the BFO approach yielded the best models. Notably, the mean squared error (MSE) during the testing phase was remarkably low, measuring 0.000552 for cumulated CO2 production and 0.001598 for cumulated methane production. Overall, the models introduced in this study exhibit excellent generalization capability and serve as reliable predictors for the systems' output in various scenarios. The significance of these findings extends beyond the laboratory, as the proposed system and its model can effectively aid end‐users in planning their consumption and correlating biogas utilization with peak production. This mainly benefits small consumers in remote areas, offering them sustainable energy solutions and paving the way for a greener future. [ABSTRACT FROM AUTHOR]

The efficient co‐production of H2 and CH4 via anaerobic digestion (AD) requires separate stages, as it cannot yet be achieved in one step. Lactic acid bacteria (LAB) (Limosilactobacillus) release H2 and acetate by enhancing hydrolysis, potentially increasing CH4 production with simultaneous H2 accumulation. This study investigated the enhanced effect of one‐step co‐production of H2 and CH4 in AD by LAB and elucidated its enhancement mechanisms. The results showed that 236.3 times increase in H2 production and 7.1 times increase in CH4 production are achieved, resulting in profits of 469.39 USD. Model substrates lignocellulosic straw, sodium acetate, and H2 confirmes LAB work on the hydrolysis stage and subsequent sustainable volatile fatty acid production during the first 6 days of AD. In this stage, the enrichment of Limosilactobacillus carrying bglB and xynB, the glycolysis pathway, and the high activity of protease, acetate kinase, and [FeFe] hydrogenase, jointly achieved rapid acetate and H2 accumulation, driving hydrogenotrophic methanogenesis dominated. From day 7 to 24, with enriched Methanosarcina, and increased methenyltetrahydromethanopterin hydrogenase activity, continuously produced acetate led to the mainly acetoclastic methanogenesis shift from hydrogenotrophic methanogenesis. The power generation capacity of LAB‐enhanced AD is 333.33 times that of China's 24,000 m3 biogas plant. [ABSTRACT FROM AUTHOR]

The efficient co‐production of H2 and CH4 via anaerobic digestion (AD) requires separate stages, as it cannot yet be achieved in one step. Lactic acid bacteria (LAB) (Limosilactobacillus) release H2 and acetate by enhancing hydrolysis, potentially increasing CH4 production with simultaneous H2 accumulation. This study investigated the enhanced effect of one‐step co‐production of H2 and CH4 in AD by LAB and elucidated its enhancement mechanisms. The results showed that 236.3 times increase in H2 production and 7.1 times increase in CH4 production are achieved, resulting in profits of 469.39 USD. Model substrates lignocellulosic straw, sodium acetate, and H2 confirmes LAB work on the hydrolysis stage and subsequent sustainable volatile fatty acid production during the first 6 days of AD. In this stage, the enrichment of Limosilactobacillus carrying bglB and xynB, the glycolysis pathway, and the high activity of protease, acetate kinase, and [FeFe] hydrogenase, jointly achieved rapid acetate and H2 accumulation, driving hydrogenotrophic methanogenesis dominated. From day 7 to 24, with enriched Methanosarcina, and increased methenyltetrahydromethanopterin hydrogenase activity, continuously produced acetate led to the mainly acetoclastic methanogenesis shift from hydrogenotrophic methanogenesis. The power generation capacity of LAB‐enhanced AD is 333.33 times that of China's 24,000 m3 biogas plant. [ABSTRACT FROM AUTHOR]

This research explores the potential for generating biogas and clean energy by processing organic waste, a process that can become a sustainable solution to Syria's energy needs. Focusing on agricultural residues generated from citrus fruit orange, date, and jujube cultivation in Syria, this study evaluates the potential for anaerobic digestion of these residues for biogas production. It highlights the influence of substrate composition and the optimization of fermentation processes on biogas and methane production. The study focuses on evaluating the anaerobic digestion process by examining various dosages ranging from 20% to 50% dry matter for citrus orange waste, and different types of substrate with a fixed ratio of 20% substrate dry matter. It specifically discusses the factors influencing the inhibitory effect of anaerobic digestion, giving particular consideration to orange waste, a significant byproduct of the citrus industry. The biogas produced maintained a stable methane content when a citrus‐to‐inoculum ratio of 30:70 was used. Jujube waste, characterized by a composition rich in cellulose and hemicellulose, exhibited a higher potential for biogas and methane generation among the fruit waste investigated, particularly when combined with the inoculum in a 20:80 ratio. The research findings underscore the potential of using Syrian agricultural residues, including orange citrus peel, date, and jujube fruit, for the production of biogas through anaerobic digestion. [ABSTRACT FROM AUTHOR]

The global seaweed industry annually consumes approximately 600,000 tons of dried algal biomass to produce algal hydrocolloids, yet only 15–30% of this biomass is utilized, with the remaining 70–85% discarded or released as scum or wastewater during the hydrocolloid extraction process. This residual biomass is often treated as waste and not considered for further commercial use, which contradicts the principles of sustainable development. In reality, the residual algal biomass could be employed to extract additional biochemical components, such as pigments, proteins, and cellulose, and these ingredients have important application prospects in the food sector. According to the biorefinery concept, recycling various products alongside the principal product enhances overall biomass utilization. Transitioning from traditional single‐product processes to multi‐product biorefineries, however, raises operating costs, presenting a significant challenge. Alternatively, developing value‐added utilization technologies that target seaweed waste without altering existing processes is gaining traction among industry practitioners. Current advancements include methods such as separation and extraction of residual biomass, anaerobic digestion, thermochemical conversion, enzymatic treatment, functionalized modification of algal scum, and efficient utilization through metabolic engineering. These technologies hold promise for converting seaweed waste into alternative proteins, dietary supplements, and bioplastics for food packaging. Combining multiple technologies may offer the most effective strategy for future seaweed waste treatment. Nonetheless, most research on value‐added waste utilization remains at the laboratory scale, necessitating further investigation at pilot and commercial scales. [ABSTRACT FROM AUTHOR]

The increasing volume of textile waste in landfills and incineration poses severe environmental challenges. Waste valorisation of textile waste via anaerobic digestion (AD) is preferable, as it offers economic and environmental benefits, but it is hindered by textile complexity, necessitating effective pretreatment technologies to improve biogas production. This study aims to evaluate various pretreatment technologies for biogas production from textile fibres via AD. A weighted‐scoring analysis (WSA) assessed pretreatment methods based on technical, economic, environmental and operational criteria. Hydrothermal pretreatment emerged as the most technically effective method, scoring 140 owing to its substantial methane enhancement. Economically, shredding was the most viable option, scoring 125, as a consequence of low capital and O&M cost. Environmentally, hydrothermal and deep eutectic solvent (DES) pretreatments were top performers with 100 points owing to low environmental impact and positive heat reactions. In a case study conducted in the Auckland region, the potential environmental impact (PEI) obtained from hydrothermal and DES were 169 and 92 per year, respectively, resulting in minimal environmental impact. Operationally, ultrasonic and biological pretreatments scored highest owing to their ease of operation, and minimal health and safety requirements. Overall, hydrothermal pretreatment achieved the highest WSA score of 340, reflecting its balanced performance across all criteria. Hydrothermal pretreatment is the most promising technology for enhancing biogas production from textile waste. Its technical efficiency, economic feasibility and environmental benefits regarding the WSA score make it suitable for upscaling and providing a viable solution for managing textile waste in the AD plant. © 2024 The Author(s). Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

A high rate upflow anaerobic polyfoam‐based bioreactor (UAPB) was developed for lab‐scale in‐situ biogas upgrading by H2 injection. The reactor, with a volume of 440 mL, was fed with synthetic wastewater at an organic loading rate (OLR) of 3.5 g COD/L·day and a hydraulic retention time (HRT) of 7.33 h. The use of a porous diffuser, alongside high gas recirculation, led to a higher H2 liquid mass transfer, and subsequently to a better uptake for high CH4 content of 56% (starting from 26%). Our attempts to optimize both operational parameters (H2 flow rate and gas recirculation ratio, which is the total flow rate of recirculated gas over the total outlet of gas flow rate) were not initially successful, however, at a very high recirculation ratio (32) and flow rate (54 mL/h), a significant improvement of the hydrogen consumption was achieved. These operational conditions have in turn driven the methanogenic community toward the dominance of Methanosaetaceae, which out‐competed Methanosarcinaceae. Nevertheless, highly stable methane production rates of 1.4–1.9 L CH4/Lreactor.day were observed despite the methanogenic turnover. During the different applied operational conditions, the bacterial community was especially impacted, resulting in substantial shifts of taxonomic groups. Notably, Aeromonadaceae was the only bacterial group positively correlated with increasing hydrogen consumption rates. The capacity of Aeromonadaceae to extracellularly donate electrons suggests that direct interspecies electron transfer (DIET) enhanced biogas upgrading. Overall, the proposed innovative biological in‐situ biogas upgrading technology using the UAPB configuration shows promising results for stable, simple, and effective biological biogas upgrading. [ABSTRACT FROM AUTHOR]

The USA has committed to cutting its emissions of methane, an extremely potent greenhouse gas, by at least 30% by 2030 (‘30 × 30’). This is part of the Global Methane Pledge, signed by 155 countries, to keep global warming within 1.5 °C and thereby to forestall the disastrous effects of ‘runaway climate change’. It will be a major challenge for the USA to reach 30 × 30 and there is no consensus on how to do so. This paper provides a concrete, data‐driven roadmap to indicate how to reach 30 × 30 feasibly, focusing on two enormous sources of methane emissions: organic waste and oil and gas production. It calculates that building approximately 4700 anaerobic digesters (ADs) to process food waste and animal manure would cost about $74.2 billion in capital expenditure (capex) and cut 13.6% of total US methane emissions per year. On average, each project would take roughly 2–6 years to build. Of the various methane mitigation measures analyzed in the oil and gas sectors, the most impactful would be full compliance with the US Environmental Protection Agency's (EPA's) revised New Source Performance Standards (NSPS) for oil and gas production by 2029. This would cut 17.5% of total US methane emissions annually, at a cumulative capex of $20.7 billion from 2024 to 2029. Together, the 13.6% cut from food waste and manure ADs and the 17.5% cut from full NSPS compliance would amount to a 31.5% reduction, exceeding the 30 × 30 goal. Greater clarity from the federal government on funding eligibility and additional incentives would accelerate the buildout of ADs. [ABSTRACT FROM AUTHOR]

Biogas is a type of biomass energy source, primarily composed of methane and carbon dioxide. It is generated through the controlled anaerobic digestion of manure or other organic residues. As a cleaner alternative to conventional fuels, fully purified biogas can produce approximately 36.68 MJ/m3 of en.ergy. As the separation of CO2/CH4 in biogas became an important part of the energy industry, we used membrane separation technique to study its separation methods. At first, 3,3′‐dihydroxy‐4,4′‐diamino‐biphenyl (HAB) and 4,4′‐(hexafluoroisopropylidene)diphthalic anhydride (6FDA) were polymerized by open‐loop as polyamide acid macromolecules. Then it was divided into two research routes. One was condensation to polyimide (PI) membranes directly and then thermal rearrangement (TR); the other one was ionic liquid (IL) added before condensation and thermal rearrangement. Through adjusting the thermal rearrangement temperature, different modified polyimide membranes were obtained and tested their separation performance of CO2/CH4. For the result of the test, the best one, membrane HAB‐6FDA‐IL‐TR400, could reach a good separation performance as PCO2 = 403.80 Barrer, αCO2/CH4 = 82.35. It was beyond the Robeson's 2019 upper limit and proved that the modification by IL and thermal rearrangement was benefit for the separation performance of polyimide membranes. [ABSTRACT FROM AUTHOR]

Sludge disintegration is an environmental and industrial challenge that requires intensive research and technological development. Sludge has a complex structure with a high yield of various chemical and biological compounds. Anaerobic digestion is the most commonly used process for sludge disintegration to produce biogas, detoxify sludge, and generate biosolids that can be used in agriculture. Biological cell lysis is the rate‐limiting cell lysis. This review discusses the application of sonolysis as a sludge pretreatment for enhanced anaerobic digestion via three combined processes: thermal destruction, hydrochemical shear forces, and radical oxidation. The mechanistic pathways of sono‐pretreatment to enhance biogas, sludge‐enhanced dewatering, activation of filamentous bacteria, oxidation of organic pollutants, release of heavy metals, reduction of bulking and foaming sludge, and boosting ammonia‐oxidizing bacterial activity are discussed in this review. This article also discusses the use of ultrasound in sludge disintegration, highlighting its potential in conjunction with Fenton and cation‐binding agents, and reviews common large‐scale sonoreactors available on the market.. [ABSTRACT FROM AUTHOR]

Textile waste is becoming among the most polluting waste in the world, discarded mostly in landfills. Valorizing textile waste via anaerobic digestion (AD) helps conserve resources, reduce environmental impact, and foster a circular economy. Although several reviews have discussed textile waste AD, there is a lack of detailed understanding of the challenges encountered during textile waste AD. Therefore, the goal of this review is to focus on challenges encountered and possible solutions for those challenges for biogas and fertilizer conversion via AD. Potential strategies include chemical, biological, and thermal pretreatments that significantly increase the digestion process. Co‐digestion of natural textile waste, cotton, and wool with carbon and nitrogen‐rich substrates improves AD efficiency by twofold. Moreover, separating polyester from polycotton and textile dye removal via solvent and advanced oxidation processes significantly increases methane yield compared with untreated textile waste. This review can aid in analyzing suitable methods to optimize the biogas production of textile waste via AD. [ABSTRACT FROM AUTHOR]

One of the well‐known methods for correctly managing sludge disposal is using produced sludges as fuel in biogas‐burning power plants. This study employed the ReCiPe2016 life cycle assessment methodology in conjunction with SimaPro software to assess the environmental impacts of a biogas‐fired power plant in Tehran with a total capacity of 2.4 MW. The results were analyzed, and the 13 necessary pieces of information for the biogas burning system per 1 MWh produced heat and power by the combined heat and power unit were considered. In anaerobic digestion, heat and power in all classes had reducing effects on the environment. The heat and power classes, reinforced steel, chrome steel, low alloy steel, copper, and cast iron, exhibited the highest environmental impacts within the integrated heat and power system. Among all impact classes, power (for anaerobic digestion) in the class of carcinogenic toxicity in humans with a value of −6.01976 kg 1,4‐DCB and copper (for combined heat and power) in the marine environmental toxicity class with a value of 0.731434 kg 1,4‐DCB had the most reduction effect and the most impact of pollutant on the environment among the considered classes, respectively. Conclusively, in the anaerobic digestion process, heat and power had a positive effect on the environment in all impact classes. So, sludge can be an adequate candidate and anaerobic digestion can be an eco‐friendly method for power generation. Other effect classes are presented in detail as results. This study could guide the development of similar facilities globally, considering factors like wastewater volume and combined heat and power technology. [ABSTRACT FROM AUTHOR]

Anaerobic digestion of abundant feedstock from biomaterials is a good innovative fossil fuel alternative approach for the synthesis of green fuel (biogas). Rotatable central composite design (CCD) and machine learning (ML) via Python coding were successfully used to design, optimize, and predict the rate of biogas production from stew‐rice and eggs digestate with Udara seeds in an anaerobic unit. Two‐input parameters, such as inoculation ratio (S/I) and hydraulic reaction time (HRT) were considered, resulting in 13 experimental setups under mesophilic surroundings of 25–34°C. Mixture ratios of substrate/inoculum (S/I) of 0.98:1, 1.5:1, 2.75:1, 2.75:1, 4:1, 1.5: 1, and 4.52:1 were used against 30, 20, 44.14, 15.86, 40, 40, and 30 days HRT as modeled by CCD rotatable to optimize biogas production from crushed Udara seeds with spoilt stew‐rice and eggs digestate. From the results, it was observed that the coefficient of determination (R2) of 0.9573 was generated via CCD rotatable whereas, the R2 of 1 was generated from the multivariate regression of ML approach. Also, the data and graphs derived via ML were superior to the ones derived from CCD rotatable. However, the maximum output of 4.84 L at 4 mixing ratio and 40 days HRT from CCD rotatable is close to the ML value of 4.89 L under the same input factors, yet ML yielded more. Thus, it is clear that the Python‐based ML algorithm approach has the potential to predict biogas output better than CCD rotatable. However, the Gas Chromatography Mass Spectrometry analysis of the highest output produced generated 63.29% biomethane and 26.71% CO2 by volume and produced a flashpoint of −167°C which is flammable. Thus, the generated biogas via an anaerobic unit can be transmitted into large‐scale commercial applications for the betterment of mankind. [ABSTRACT FROM AUTHOR]

The production of value‐added products from sewage sludge is considered to be one of the solutions for the sustainable management of sludge in wastewater treatment plants (WWTPs). The presence of carbon, nitrogen, and phosphorus sources has made the sewage sludge of WWTPs a valuable and low‐cost substrate for the production of fermentative products. In the current study, a process was developed for microbial lipid production from two types of sewage sludge from a WWTP in northern Isfahan: anaerobic digester inlet sludge (DIS) and anaerobic digester outlet sludge (DOS). This process was based on the release of volatile fatty acids (VFAs) from the sludge by combinations of γ‐ray irradiation, anaerobic digestion, and acidogenic fermentation followed by utilization of VFAs in a microbial process by the oleaginous yeast Cryptococcus aureus UIMC65. After γ‐ray irradiation, the acidogenic fermentation of the treated sludge released 72% of the organic matter content of the sludge with acidification efficiency of 12% leading to 0.516 g L−1 VFAs. The oleaginous fermentation of the released VFAs for 7 days was accompanied by production of 1.58 g L−1 dry cell biomass with 40% lipid content. The results of this study indicate that the sewage sludge from urban WWTP has the potential to be used for the production of microbial lipids. [ABSTRACT FROM AUTHOR]

This research focuses on the impact of pulsed feeding of corn residues on biogas production from pig manure. It also analyzes the properties and microbial diversity in the resulting product. The study highlights the increasing global demand for pork and the resulting environmental challenges, such as effluent management, and suggests that biogas production can be a sustainable solution. The research was conducted at a model farm in Argentina and involved evaluating biogas production and microbial variability at different stages of the pulsed feeding process. The results showed a significant decrease in the chemical and biochemical oxygen demands after the degassing process, indicating a reduction in organic matter. The biogas composition improved with an increase in methane and a reduction in volatile fatty acids. There was also an increase in biogas and methane production and a decrease in methane production lag time, indicating an improvement in anaerobic digestion efficiency. Microbiological analysis revealed a reduction in microbial diversity during pulsed feeding, indicating the adaptation of the microbial community to new conditions. Overall, the study demonstrates the potential of pulsed feeding of corn residues to enhance biogas production from pig manure, with significant implications for effluent management in pork production and sustainable biogas production. [ABSTRACT FROM AUTHOR]

To reach the goals set by the US Department of Energy's Sustainable Aviation Fuel (SAF) Grand Challenge, currently available feedstocks may be insufficient. Giving priority to developing, prototyping and reducing the cost of algal feedstock before investing and lining up locations is important. As the production of algal feedstocks advances, a simplified conversion approach using more mature technologies can help reduce the investment risk for algae‐based fuels. Reducing process complexity to the steps described here [namely, conversion of lipids to HEFA (hydroprocessed esters and fatty acids) fuels and relegating the remainder of the biomass to anaerobic digestion or food/feed production] enables the near‐term production of algal SAF but presents challenging economics depending on achievable cultivation costs and compositional quality. However, these economics can be improved by present‐day policy incentives. With these incentives, the modeled algae‐to‐HEFA pathway could reach a minimum fuel selling price as low as $4.7 per gasoline gallon equivalent depending on the carbon intensity reduction that can be achieved compared with petroleum. Uncertainty about algal feedstock production maturity in the current state of technology and the future will play a large role in determining the economic feasibility of building algae‐to‐HEFA facilities. For example, if immaturity increases the feedstock price by even 10%, SAF production in 2050 is about 58% of the production which could have been achieved with mature feedstock. Additionally, growth in this conversion pathway can be notably boosted through the inclusion of subsidies, and also through higher‐value coproducts or higher lipid yields beyond the scope of the process considered here. [ABSTRACT FROM AUTHOR]

The USA has significant potential to produce energy from anaerobic digesters (AD) due to the size of its agricultural sector. The use of ADs reduces greenhouse gas (GHG) emissions from manure management. The financial benefits to farmers come from the on‐farm use, or off‐farm sales, of biogas and its end products, namely renewable natural gas (RNG) or electricity. Current energy prices and policies in the USA are insufficient to trigger large‐scale construction of ADs; however, payments to avoid GHG emissions and sequester carbon could become sufficiently high to prompt investment. This analysis quantifies the economic incentives necessary for the construction of ADs for swine producers and can easily be expanded to include other feedstocks. Various end‐use pathways to produce RNG and electricity are considered to account for location, herd size, and other parameters to deliver a comprehensive analysis for the USA. The analysis and results are composed of a generic part to illustrate the effects of carbon payment on profitability in general as well as a specific analysis for states representing 83.6% of the US hog inventory. Our results indicate that carbon payments would be a stronger determinant than energy prices in farm‐level decisions to install ADs, but that energy prices would be influential in determining the optimal biogas end use. The potential need for long‐term contracts – both for energy and carbon payments – to reduce investment uncertainty and increase investment in ADs is also discussed. [ABSTRACT FROM AUTHOR]

Digitally controlled reactors can optimize biological reactions and process control through a neural network system. This study reports on the design, fabrication, and automation of a laboratory‐scale anaerobic reactor for the management of agrifood byproducts and bioenergy recovery. The process described here can digitally control the operational parameters, which is beneficial for stable methane production. The proposed process comprises the digital measurement of temperature, pH, humidity, biogas volume, and methane composition by integrating the data in a processor module. The proposed automated reactor can assist significantly in controlling and monitoring the anaerobic digestion process, providing decision making during waste management and bioenergy recovery. A case study is described with the application of automated reactors in a pilot‐scale plant, operated with the flow of 8 m3 slaughterhouse wastewater per day and a biogas production of 10 m3 h−1. The automated pilot‐scale process presents many advantages, including a continuous mode of operation and a faster adaptation of the microorganisms to the substrate, improving biogas production. [ABSTRACT FROM AUTHOR]

Magnetite nanoparticles can boost methane production via direct interspecies electron transfer. However, the combined effect of inoculum and particle characteristics on magnetite's methanogenesis stimulation is poorly understood. Here, the influence of inoculum type, particle size, and particle concentration on the ability of magnetite to accelerate methanogenesis was studied in batch anaerobic digestion experiments. Fresh and degassed mesophilic digester sludge was used as inoculum, representing methanogenic communities in the exponential or stationary growth and endogenous decay phases, respectively. Three magnetite particle size ranges, small (50–150 nm), medium (168–490 nm), and large (800 nm–4.5 μm), at two different concentrations (2 and 7 mM) were used. With degassed sludge, the effect of magnetite on the methane production rate was weak and depended on the particle size and concentration. Only magnetite of medium size at both 2 and 7 mM significantly increased the methane production rate by 12% compared to the control with no magnetite. The lag phase was reduced by 17% compared to the control, only with 2 mM of both small and medium size magnetite. Conversely, adding magnetite into fresh sludge significantly increased the methane production rate by an average of 32% while simultaneously decreasing the lag phase by 15%–40%, as compared to the control, independently of the magnetite's size and concentration. The stimulation of methane production depends on magnetite and inoculum characteristics. [ABSTRACT FROM AUTHOR]

Pakistan is facing a major challenge in the domestic gas and energy sector, and its demand is continuously growing. It is imperative to produce more energy in the form of gaseous resources and electricity to reduce this energy crisis in the future. The current work is related to studying various factors that play a critical role in enhancing the process and production of biogas. The effect of codigestion, substrate size, temperature, pH, and catalyst addition are important parameters. Three batch processes are conducted for 21 days under mesophilic conditions, which is easier to achieve as compared with the thermophilic one. Codigestion of cow manure combined with food, poultry waste, and sewerage water showed some promising results compared with a single substrate (cow dung). This results in the production of biogas of about 120 L. The particle size is then reduced to 5 mm, which leads to an increase in the available surface area for microbial attack and hence increases and enhances further the process and production of biogas. However, the addition of 250 g of silica gel increases production by up to 17%. The better value for the pH range for this batch was found in the range of 6.5–7.8. The codigestion would help in cost‐effective and more efficient waste treatment. The digestate in all the batch processes comes out enriched in nitrogen that is used as an organic fertilizer. [ABSTRACT FROM AUTHOR]

Orange peel waste (OPW) and crude glycerol (CG) can be used in anaerobic processes. To avoid inhibition due to D‐limonene from OPW, the process can be carried out in two stages. Thus, this work aimed to evaluate the generation of methane in biogas through the anaerobic digestion of OPW and CG, individually and mixed, in a single‐stage and two‐stage batch system. For this purpose, the biochemical methane potential (BMP) of the wastes, separately and mixed, was determined in a single‐stage system (methanogenic phase) and in a two‐stage system (acidogenic and methanogenic), following the German standard VDI 4630. The results obtained were statistically analyzed using Shapiro−Wilk and non‐parametric tests. For OPW, the BMP value found was 160.5 m3 CH4. tonSV−1. For CG, the result for BMP was 344.8 m3 CH4. tonVS−1. The result of these mixed wastes was equivalent to 501.3 m3 CH4. tonSV−1, for BMP. Through the statistical tests used, it was found that the use of OPW and CG, separately and mixed, in the two‐stage system does not present a statistically significant difference in the production of biogas when using the same wastes in a single‐stage system. However, it was found that the co‐digestion of these wastes is promising for biogas generation and contributes to managing these agro‐industrial wastes. [ABSTRACT FROM AUTHOR]

Understanding and optimising biological pre‐treatment strategies for enhanced bio‐methane production is a central aspect in second‐generation biofuel research. In this regard, the application of fungi for pre‐treatment seems highly promising; however, understanding the mode of action is crucial. Here, we show how aerobic pre‐treatment of crystalline cellulose with the cellulolytic Trichoderma viride affects substrate degradability during mesophilic, anaerobic digestion. It could be demonstrated that fungal pre‐treatment resulted in a slightly reduced substrate mass. Nevertheless, no significant impact on the overall methane yield was found during batch fermentation. Short chain organic acids accumulation, thus, overall degradation dynamics including methane production kinetics were affected by the pre‐treatment as shown by Gompertz modelling. Finally, 16S rRNA amplicon sequencing followed by ANCOM‐BC resulted in up to 53 operative taxonomic units including fermentative, syntrophic and methanogenic taxa, whereby their relative abundances were significantly affected by fungal pre‐treatment depending on the duration of the pre‐treatment. The results demonstrated the impact of soft rot fungal pre‐treatment of cellulose on subsequent anaerobic cellulose hydrolysis as well as on methanogenic activity. To the best of our knowledge, this is the first study to investigate the direct causal effects of pre‐treatment with T. viride on basic but crucial anaerobic digestion parameters in a highly standardised approach. [ABSTRACT FROM AUTHOR]

BACKGROUND: The addition of conductive materials or the application of external voltage is a promising novel methodology to enhance methane production in anaerobic digesters. However, there is limited knowledge about their individual or combined effects on the anaerobic digestion of dairy wastewater. The aim of this study was to examine the effects of granular activated carbon (GAC) or magnetite addition and external voltage application, both individually and in combination, for the anaerobic digestion of real, undiluted dairy wastewater. RESULTS: The results showed that the estimated maximum methane production rate increased significantly (P < 0.05) from 143 ± 8 mL gVSadded−1 day−1 in the control reactors to 163 ± 11 mL gVSadded−1 day−1 and 166 ± 11 mL gVSadded−1 day−1 in the reactors containing GAC, with or without the combination of external voltage, respectively. The addition of GAC, in both cases, resulted in higher consumption rate of acetate, indicating a promotion of the methanogenesis step. By contrast, the application of external voltage or the addition of magnetite had no significant effect on either methane production rate nor methane yield. Moreover, the analysis of the microbial community showed that the addition of GAC resulted in the enrichment of Desulfobacterota, Methanosarcina, Candidatus Methanofastidiosum and Methanolinea. CONCLUSION: Overall, GAC addition seems a promising strategy to increase methane production in anaerobic digesters treating dairy wastewater. © 2024 The Author(s). Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

The increasing global population has led to a surge in waste production across various fields including agriculture, industry, marine, and household, posing significant waste management challenges. Concurrently, the world is facing an energy crisis, emphasizing the crucial need for sustainable and renewable energy sources. This comprehensive review examines the potential of biomethane production from diverse waste biomass. Feedstock characteristics; anaerobic digestion (AD); biochemical pathways; factors influencing AD; various pretreatment methods such as physical, chemical, biological, and combined; existing policies supporting biomethane production; and potential new policy implications are discussed in this review along with the significance of waste‐to‐energy integration. Our findings indicate that lignocellulosic wastes, primarily agricultural waste, stand out as the most efficient biomass source for biomethane production due to their characteristics such as high carbon/nitrogen ratio, low ash content, and their abundant availability. Among pretreatment methods, combined pretreatment emerges as the most promising option, offering flexibility and effectiveness in enhancing biomethane production. Additionally, the two‐stage digester configuration proves advantageous in overcoming limitations associated with single‐stage digesters such as pH inhibition. Altogether, the review highlights that biomethane production from waste biomass through AD offers a sustainable solution. [ABSTRACT FROM AUTHOR]

This work assessed the performance of a pilot‐scale cascade anaerobic digestion (AD) system when treating mixed municipal wastewater treatment sludges. The cascade system was compared with a conventional continuous stirred tank reactor (CSTR) digester (control) in terms of process performance, stability, and digestate quality. The results showed that the cascade system achieved higher volatile solids removal (VSR) efficiencies (28–48%) than that of the reference (25–41%) when operated at the same solids residence time (SRT) in the range of 11–15 days. When the SRT of the cascade system was reduced to 8 days the VSR (32–36%) was only slightly less than that of the reference digester that was operated at a 15‐day SRT (39–43%). Specific hydrolysis rates in the first stage of the cascade system were 66–152% higher than those of the reference. Additionally, the cascade system exhibited relatively stable effluent concentrations of volatile fatty acids (VFAs: 100–120 mg/l), while the corresponding concentrations in the control effluent demonstrated greater fluctuations (100–160 mg/l). The cascade system's effluent pH and VFA/alkalinity ratios were consistently maintained within the optimal range. During a dynamic test when the feed total solids concentration was doubled, total VFA concentrations (85–120 mg/l) in the cascade system were noticeably less than those (100–170 mg/l) of the control, while the pH and VFA/alkalinity levels remained in a stable range. The cascade system achieved higher total solids (TS) content in the dewatered digestate (19.4–26.8%) than the control (17.4–22.1%), and E. coli log reductions (2.0–4.1 log MPN/g TS) were considerably higher (p < 0.05) than those in the control (1.3–2.9 log MPN/g TS). Overall, operating multiple CSTRs in cascade mode at typical SRTs and mixed sludge ratios enhanced the performance, stability digesters, and digestate quality of AD. Practitioner Points: Enhanced digestion of mixed sludge digestion with cascade system.Increased hydrolysis rates in the cascade system compared to a reference CSTR.More stable conditions for methanogen growth at both steady and dynamic states.Improved dewaterability and E. coli reduction of digestate from the cascade system. [ABSTRACT FROM AUTHOR]

High carbon content and high‐level biodegradability are major constraints of the anaerobic digestion of food waste. In the present study, anaerobic digestion of model food waste was carried out in a fed batch digester. Nitrogen content in model food waste was adjusted by the addition of ammonium chloride at the desired C/N ratio. Biogas production at ammonium chloride percentages of 0, 0.8, 1.5, 2.14, and 3.2 % (weight basis) were carried out under mesophilic conditions in a pilot plant scale floating drum digester. At an ammonium chloride percentage of 1.5 % that balances C/N ratio 25, highest biogas production of 0.42 m3 kg−1 of VS was attained while biogas production from food waste without ammonium chloride of 0.06 m3 kg−1 of VS was obtained. The highest methane yield of 0.323 m3 kg−1 of VS was found at ammonium chloride of 1.5 % while methane yield of 0.042 m3 kg−1 of VS was achieved from food waste without ammonium chloride. The highest percent increase CH4 yield of 669 % was obtained at an ammonium chloride percentage of 1.5 %. Biogas productivity obtained at ammonium chloride percentage of 1.5 % was 0.6 L L−1 d−1. Hence, the optimum ammonium chloride percentage obtained was 1.5 % which balances the C/N ratio at 25. [ABSTRACT FROM AUTHOR]

The decarbonization potential of hydrogen offers increasing usage paths in the fight against climate change resulting in a growing demand for climate‐neutral hydrogen. This challenge is met by producing hydrogen microbially from renewable substrates as an alternative to 'green hydrogen' from water electrolysis. Initial results have shown that coupling dark fermentation and anaerobic digestion is not only possible but also advantageous. Specifically, by integrating dark fermentation in existing biogas plants, the overall physical efficiency of the process's substrate turnover can be increased by up to 50% through providing hydrogen in addition to biogas. The achieved test results are examined based on limit‐oriented physical efficiency evaluation to show the potential for optimization of the substrate turnover in biological concepts based on modeling. Finally an overview of a commissioned demonstration plant is given, which will provide further insights into the feasibility of the dark fermentation on an industrial scale. [ABSTRACT FROM AUTHOR]

The objective of this work was to evaluate anaerobic digestion processes of mixtures of cassava starch‐based polymer (CSP) and papaya fruit pulp waste (PPW) at different ratios, with physical division of digestion stages. Acidogenic phase (phase 1) was conducted under temperature of 45°C and hydraulic retention time of 96 h. Monitoring reactors with destructive samples were subjected to the same conditions in order to assess the initial degradation profile of the substrates. The methanogenic phase (phase 2) was conducted under temperature of 37°C and the hydraulic retention time was defined as equal to the time the biogas production ceased. The results showed that the CSP/PPW mixtures presented interesting synergism and high biogas production potential under the conditions studied. The treatment with CSP/PPW at the ratio of 75/25 showed the best digestion performances in the phase 1. The highest CSP to PPW ratios showed satisfactory results for accumulated biogas productions (5955.58 mL) and for maximum biogas production rate (25.64 mL gVS−1 day−1) in the phase 2. [ABSTRACT FROM AUTHOR]

Restoring native grassland vegetation can substantially improve ecosystem service outcomes from agricultural watersheds, but profitable pathways are needed to incentivize conversion from conventional crops. Given growing demand for renewable energy, using grassy biomass to produce biofuels provides a potential solution. We assessed the techno‐economic feasibility and life cycle outcomes of a "grass‐to‐gas" pathway that includes harvesting grassy (lignocellulosic) biomass for renewable natural gas (RNG) production through anaerobic digestion (AD), expanding on previous research that quantified ecosystem service and landowner financial outcomes of simulated grassland restoration in the Grand River Basin of Iowa and Missouri, United States. We found that the amount of RNG produced through AD of grassy biomass ranged 0.12–45.04 million gigajoules (GJ), and the net present value (NPV) of the RNG ranged −$97 to $422 million, depending on the combination of land use, productivity, and environmental credit scenarios. Positive NPVs are achieved with environmental credits for replacement of synthetic agricultural inputs with digestate and clean fuel production (e.g., USEPA D3 Renewable Identification Number, California Low Carbon Fuel Standard). Producing RNG from grassy biomass emits 15.1 g CO2‐eq/MJ, which compares favorably to the fossil natural gas value of 61.1 g CO2‐eq/MJ and exceeds the US Environmental Protection Agency's requirement for cellulosic biofuel. Overall, this study demonstrates opportunities and limitations to using grassy biomass from restored grasslands for sustainable RNG production. [ABSTRACT FROM AUTHOR]

Microbial electrochemical systems (MESs) can enhance methane production in anaerobic digestion, but their performance is hindered by inadequate electron transfer between the cathode and microbes. Magnetite–zeolite (MZ)‐based catalysts accelerate electron exchange; however, the optimal loading of MZ is crucial for maximizing MES performance. In this study, different loadings of the MZ catalyst ranging from 0 to 2 mg cm−2 on the cathode were evaluated to obtain an optimum loading for maximizing methane recovery from MES. Electrochemical analyses demonstrated enhanced electrochemical reduction kinetics of the cathode with increased MZ loading from 0 to 2 mg cm−2. Among the tested loadings, the MES with 1 mg cm−2 MZ on the cathode exhibited the highest methane production rate at 548 mL L−1 d−1, surpassing other MES operations with 2 and 0.5 mg cm−2 (499 and 434 mL L−1 d−1, respectively). Additionally, the MES with 1 mg cm−2 MZ demonstrated the highest soluble chemical oxygen demand removal efficiency of 87% and total coulomb recovery of 1444.06C ± 42.60C, with the lowest amount of volatile fatty acids accumulation. Consequently, MZ is recommended as a superior catalyst for enhancing MES performance and suggested to utilize 1 mg cm−2 MZ loading on the cathode to maximize methane production. [ABSTRACT FROM AUTHOR]

Exploring alternative energy sources is vital amid increasing human fuel consumption. Globally, biogas, rich in methane, hydrogen sulfide, and carbon dioxide, addresses energy demands through biomass anaerobic digestion (AD). Efficient digestate management, employing techniques like solid‐liquid separation and composting, is crucial for environmental protection. The goal is to optimize nutrient‐rich byproduct utilization while minimizing negative impacts. This review analyzes diverse substrates, emphasizing challenges and benefits. Key considerations include nutrient ratios, moisture content, co‐digestion, organic loading rate, and retention time. The study explores temperature's impact on microbial growth, biogas impurities, and upgradation techniques, including biological methods. Fermentation, microbial electrochemical techniques, and biochar use for enhanced AD are introduced. Discussing digestate's multifaceted aspects, the review highlights its nutrient value and diverse applications in aquaculture, animal feed, fermentation, bioremediation, and fine chemical production. [ABSTRACT FROM AUTHOR]

In response to the EU's REPowerEU initiative (COM (2022) 108) which encourages an increase in biogas production by 20% in member states by 2030 to boost energy independence, it has become essential to identify sustainable alternatives to traditional feedstocks for biogas production, especially in the EU Member states where there is still high dependence on corn silage as the main raw material in biogas plants. While corn silage, predominantly used in the European biogas plants today, serves primarily for the livestock sector, alternative sources need to be explored. Therefore, this study aimed to evaluate the potential of Arundo donax, a perennial energy crop, as an alternative feedstock in a continuous anaerobic process. The biogas yield and its quality, characterized by CH4, CO2, H2S and O2 content, were determined during a continuous process with A. donax, compared with two mixed feedstocks of A. donax and corn silage over a 5‐month period in a continuous anaerobic digestion process. The results revealed that A. donax exhibits a biogas yield and methane content comparable to corn silage, indicating its potential as a viable and sustainable alternative feedstock for biogas production. [ABSTRACT FROM AUTHOR]

Nanotechnology is a widely applied technology in environmental remediation, medicine, chemical processes and catalysis. The Development and modification of nanoparticles for wastewater treatment via anaerobic digestion have gained much interest over the years. This study synthesized six different magnetic nanoparticles (MNPs) via the co‐precipitation method. These MNPs were characterized via scanning electron microscopy/energy dispersive X‐ray (SEM/EDX), Fourier transform infrared spectroscopy (FTIR), X‐ray diffraction (XRD) and Brunauer–Emmett–Teller analysis. The SEM/EDX, FTIR and XRD affirmed the success of the synthesis of MNPs. The MNPs were furthermore explored to enhance the anaerobic digestion of wastewater to generate biogas. This was done by conducting a biochemical methane potential (BMP) assay, where seven bioreactors were digested for 21 and 30 days at 35°C. In comparison with the control (no MNPs), which had a removal efficiency of <68%, the results showed that the addition of MNPs to the BMP system demonstrated good degradation of >70% chemical oxyggen demand (COD) and turbidity removal efficiencies. There was a 20% increase in methane yield for the BMP setups with MNP additives compared with the control bioreactor. [ABSTRACT FROM AUTHOR]

In response to the growing awareness of environmental preservation, there has been a surge in studies employing the life cycle assessment (LCA) approach which helps to identify and minimize environmental impacts associated with rice straw recovery processes. However, there is lack of comprehensive and trend analysis related to the development of critical methodological steps of LCA within this field. To fill the gap, this review examines 43 primary LCA studies from 2004 to 2023 period concerning the use of rice straw for bioenergy production and categorized into two groups: the "first‐year group" covering 2004–2013 and the "second‐year group" spanning from 2014 to 2023. This categorization serves to facilitate the examination of trends and patterns within each decade, offering insights into the evolution of research objectives, methodological advancements, and changes in research outcomes over time. The analysis reveals a shift from studying individual technologies to comparing various technologies, includes scenarios development and consideration of economic and social aspects. Furthermore, the "second‐year group" (2014–2023) exhibits a notable uptick in the exploration of gasification, pyrolysis, anaerobic digestion, and fermentation, whereas combustion technologies have experienced a slight decrease in the number of studies. Challenges in LCA studies arise from nonstandardized methodologies, introducing bias and uncertainty. To enhance the reliability and comparability of environmental assessments, it is recommended to establish standardized guidelines, improve transparency, and update databases. Overall, this review provides a foundational resource for future waste‐to‐energy studies and recommends steps to enhance the applicability and validity of LCA in forthcoming research. This article is categorized under:Sustainable Energy > BioenergyClimate and Environment > Pollution PreventionClimate and Environment > Circular Economy [ABSTRACT FROM AUTHOR]

Anaerobic digestion processes for biogas generation using alperujo have been the subject of intensive studies suggesting that phenolic compounds act as microbial inhibitors in anaerobic digestion. Pretreatments are needed to reduce the effects of phenolic compounds and improve biogas production, especially for dry anaerobic digestion. However, industrial‐scale implementation of these pretreatments is challenging, and it is unclear whether the improvement in biogas production justifies the energy expended on pretreatment. This study examines the energy analysis of dry anaerobic digestion and three alternative pretreatments: alkaline, oxidative and thermal. Results indicate that thermal pretreatment at 80°C with added water reduces phenolic compounds in alperujo by 35.4%. Meanwhile, pretreated with hydrogen peroxide in alkaline medium had the highest methane productivity (205 mL CH4/gVS). Even so, thermal pretreatment was only one with an energy return on investment greater than 1, signifying the necessity for energy analysis to ensure the viability of pretreatment processes. Highlights: Three pretreatments were evaluated to improve biogas production.Thermal pretreatment offers top phenolic compounds reduction in alperujo digestion.Oxidative pretreatment increased methane productivity by 36%.Dry anaerobic digestion shows promise for alperujo biogas production.Energy return on investment index determines thermal pretreatment efficiency and viability. [ABSTRACT FROM AUTHOR]

Many operational parameters, either discretely or collectively, can influence the biodegradation performance towards enhancing biogas yield and quality. Among the operating parameters, organic loading rate (OLR), inoculum-substrate ratio, and carbon-nitrogen ratio (C/N) are the most critical parameters in the optimization and enhancement of biogas yield. Optimization of the biogas production processes depends on the ability of anaerobic microorganisms to respond to variations in operational parameters such as pH, redox potential, and intermediate products to enhance the biogas yield. This review article focuses on the role of process parameters, kinetic models, artificial intelligence, Aspen Plus (AP), and anaerobic digestion model no. 1 (ADM1) in optimizing biogas yield via an anaerobic codigestion (AcoD) process. The review showed that biomaterials codigestion upgraded biogas yield to the extent of 400%, and organic removal efficiency reached up to 90% compared to a single substrate. In addition, the current work has verified that the kinetic model is the most effective tool for signifying that the hydrolysis phase is the rate-limiting step, whereas AP is the most effective tool in the design and optimization of the AcoD process parameters. The reviewed kinetic and AI models show strong correlation values ranging from 0.931 to 0.9991 and 0.8700 to 0.9998, respectively. The AcoD system involves complex chemical reactions, but AP might have limitations in representing such complex chemical processes with nonideal behavior and complicated reaction mechanisms. The design and optimization of AcoD with reliable input parameters are highly limited or nonexistent. The AcoD process design with AP opens fresh research opportunities, including improved efficiency, finding appropriate retention time, and saving time, as well as finding the optimum biogas yield. This review article gives an insightful understanding of AcoD process parameter optimization and valuable strategies for policy development enhancing sustainability in the biogas sector. [ABSTRACT FROM AUTHOR]

All the inputs and outputs of a technical system can be interpreted from an environmental point of view. Using the life cycle assessment (LCA) approach, some changes that are less harmful to the environment can be included in the system. This research aims to evaluate the environmental effects of the wastewater treatment plant (WWTP) in South Tehran, and the LCA method was used in this study. Based on the data of qualitative parameters obtained from the measurement of Tehran province's water and sewage company, the environmental emissions were calculated and analyzed using SimaPro software (9.0.0) and the standards defined under the ReCiPe 2016-midpoint method. In the ReCiPe 2016 method, the results were expressed in two intermediate levels (including three classes of influence) and final (including 18). The results showed that the treated wastewater and chlorine factors had the most adverse environmental effects. Among the 18 effect classes, the treated wastewater in the class of marine environmental toxicity with the amount of 101.1531 kg 1,4-DCB had the most environmental impacts among other classes. The power consumed by the biogas-burning combined heat and power (CHP) unit in the wastewater treatment (WWT) process reduced the environmental effects in most impact classes. The most adverse environmental effects of the WWT process are related to damage to human health and the ecosystem. According to the findings, the use of CHP systems is suggested for energy saving and also for reducing harmful effects on the environment. [ABSTRACT FROM AUTHOR]

In anaerobic technology, pH values are crucial for targeted volatile fatty acid production. While pH dynamics can be modeled using the Anaerobic Digestion Model No. 1 (ADM1), simulation results may be biased. To address this issue, the pH prediction routine of Visual Water, a specialized water chemistry simulator, was validated. Unlike ADM1, it accounts for ionic strength and activities while also providing an automated uncertainty analysis. The analysis revealed Visual Water simulations to better fit measured pH data from acidic solutions in a miniaturized stirred‐tank reactor. [ABSTRACT FROM AUTHOR]

Biomass energy is a renewable energy source that is carbon‐neutral, versatile, and can never go extinct. In the current study, a simulation model of an anaerobic digester with parameters such as pretreatment temperature (PTT), hydraulic retention time (HRT), and feed‐to‐water (F/W) ratio was developed and a design of experiment was created. The results showed that the higher hemicellulose content in sugarcane bagasse (SB) gave a decent H2 yield (13–23 %). The significance sequence was PTT > F/W > HRT. The optimal values were HRT of 15–16 d; F/W of 1.5 (SB), 1.26 [rice straw (RS)], and 0.5 [sawdust (SD)]; and PTT of 63.3 (SB), 68.8 (RS), and 75 °C (SD). The optimal H2 yield was 19.80 (SB), 20.94 (RS), and 21.41 % (SD). Therefore, the present simulation and optimization showed concrete results to raise H2 yield. [ABSTRACT FROM AUTHOR]

BACKGROUND: To our best knowledge, no experimental study has previously investigated the simultaneous effects of adding Fe powder for the decrease of hydrogen sulfide (H2S) in biogas and the removal of phosphate (PO4‐P) in continuous anaerobic digestion (AD). This study investigated the effects of iron (Fe) powder (5 g L−1) in AD to remove H2S and PO4‐P. A comparative experiment was conducted using two semi‐continuous‐flow anaerobic digesters treating primary sludge at decreasing hydraulic retention times (HRTs) of 20 to 10 days. RESULTS: The addition of Fe powder to AD removed > 98% of H2S at all HRTs, and removed 64–72% of PO4‐P, with the highest removal efficiency at HRT = 10 d. The addition of Fe powder to AD had no noticeable effect on biogas production or pH, but it increased the CH4 content (62.7–66.0% in Fe‐treated vs 58.2–60.4% in the Control) partly due to the greater presence of Methanoregulaceae. The relative abundance of the microbial groups was more affected by HRT than by the addition of Fe powder. The presence of Fe powder notably increased the abundance of Spirochaetaceae and Syntrophaceae. CONCLUSION: As shown, the addition of Fe powder can improve the management of both H2S in the biogas and PO4‐P in the digested sludge in the AD system. © 2024 Society of Chemical Industry (SCI). [ABSTRACT FROM AUTHOR]

The increasing demand for renewable energy sources as a substitute for fossil fuels has driven researchers to develop sustainable processes for biomass energy reuse in biofuel production. Based on this premise, the present study aimed to simulate the production process of synthesis gas (syngas) from vinasse, a by‐product of the sugar and alcohol industry, highlighting the applicability of this gas in transitioning toward a more renewable and sustainable energy future. The simulation was conducted in four distinct stages using the Aspen HYSYS® software. The first stage involved obtaining hydrated ethanol from sugarcane juice, followed by anaerobic digestion of vinasse to produce biogas. The third stage involved purifying the biogas to obtain biomethane. Finally, the simulation of steam methane reforming was performed to generate syngas. The modeling and simulation results demonstrated the feasibility of the process, as it generated 20.68 Nm3 of biogas (~55% vol CH4 and 45% vol CO2) per 1 Nm3 of vinasse, corresponding to 11.66 Nm3 of biomethane (~96.5% mol CH4), which aligns with national regulatory standards and the literature presented. Regarding syngas, both evaluated configurations yielded satisfactory results. The first configuration resulted in syngas with an H2/CO molar ratio of three, making it a viable source of pure hydrogen and a raw material for biofuel production, such as dimethyl ether and methanol. The second configuration, with an H2/CO molar ratio of two, holds great potential for its application in the synthesis of liquid fuels (Fischer‐Tropsch), serving as a direct substitute for gasoline, diesel, and jet fuel. [ABSTRACT FROM AUTHOR]