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[Display omitted] • Pig manure biogas residue was converted to high-porosity engineered biochar. • Sequential hydroxide activation can remove heavy metals from biogas residue. • The proposed biochar showed excellent sorption performance for diethyl phthalate. • Pore filling and partitioning dominated the sorption process. Manure biogas residue has attracted increasing attention in waste recycling but faces substantial challenges because of its low carbon content, high ash content, and high heavy metal content. A novel sequential carbonization approach was proposed for recycling biogas residue; this approach consisted of pre-pyrolysis, activation with Ca(OH) 2 , and then activation with KOH. Pig manure-derived biogas residue was upcycled into engineered biochar (EB) with a high yield (26 %) and showed excellent performance in removing a typical plasticizer, diethyl phthalate (DEP). The proportion of carbon content greatly increased from 18 % (biogas residue) to 67 % (EB); however, the ash content decreased from 50 % (biogas residue) to 24 % (EB). The concentration of heavy metals decreased, and Zn had the largest decrease from 713 mg kg−1 to 61 mg kg−1 (p < 0.001). The sorption of DEP onto EB was rapid and reached equilibrium within 20 h. The developed specific surface area of EB was 1247 m2/g and provided abundant sorption sites for DEP; additionally, the sorption quantity reached 309 mg/g. The sorption capacity was dominated by surface adsorption. The oxygen-containing functional groups, graphene structure, porous structure, and hydrophobicity of EB contributed to the pore filling, hydrogen bonding, π–π stacking, and partitioning processes. Furthermore, the EB showed excellent practical application potential and great cycling stability. A sequential carbonization strategy was proposed to upcycle manure biogas residue into the EB for DEP removal; moreover, this strategy can aid in the attainment of environmental sustainability, including sustainable waste management and environmental pollution mitigation. [ABSTRACT FROM AUTHOR]

The paper presents the results of a study of the possibility of using biogas enriched with hydrogen at a steam-turbine mini-thermal power plant with a capacity of 1 MW, in which the process of heat energy accumulation was organized. Two-stage biological conversion of organic waste was considered in the technological scheme as the basis for obtaining biohydrogen and biogas. Five compositions of gaseous fuels were analyzed in this paper. The biohydrogen content was varied in increments of 15 %–45 %. When generating steam, a boiler with a capacity of 25 tons/hour was used; its calculation was key in the power generation unit. For fast recycling of waste with minimal hydraulic retention time, the most effective way is to use gas with a hydrogen content of up to 15 %. At the same time, the daily processing of waste will be from 349.87 to 362.21 tons, and the excess of technical hydrogen of 99.99 % purity can be realized in cylinders. The amount of organic fertilizers produced at the mini-TPP will be at least 241 tons/day. The efficiency of the steam boiler will be 95 %. Resulting steam is sent to a 1 MW steam turbine to generate electricity. Although the smallest amount of flue gases is generated by burning fuel with a hydrogen content of 45 % in a steam boiler, this is technologically impossible to implement in the scheme under consideration, since there is a shortage H 2. It should be noted that the fuel consumption in a steam boiler increases as the proportion of hydrogen increases. Based on a comprehensive analysis, it can be argued that there are not enough standard methods for designing a steam-turbine mini-thermal power plant on hydrogen, and additional research is necessary. [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]

Mixing in biogas fermenters is complex due to the non‐Newtonian rheology of biogenic substrates, which exhibit both pseudoplasticity and elasticity. It is yet unclear how these non‐Newtonian properties affect propeller flows and the mixing behavior in fermenters. Therefore, propeller flows in Newtonian as well as shear‐thinning inelastic and elastic fluids are compared numerically and validated against particle image velocity (PIV) data. Elastic normal stresses lead to an increase of pumping rates in the laminar regime and a suppression of the formation of a propeller jet in the transitional regime. Thus, flow rates are severely overestimated by the inelastic, shear‐thinning model in this regime. The results indicate that elasticity is critical for an accurate modeling of flows of biogenic substrates. [ABSTRACT FROM AUTHOR]

Anaerobic digestion constitutes a sustainable method for waste management and renewable energy generation, addressing significant environmental and societal challenges. The growing global waste crisis and the increasing momentum toward sustainable energy solutions emphasize the critical need to enhance anaerobic digestion technology for improved efficiency and environmental advantages. This process mitigates waste accumulation, enhances energy security, and reduces greenhouse gas emissions, providing a feasible solution within the framework of a circular bioeconomy. Here, we review the principles of anaerobic digestion and biogas production, focusing on agricultural waste and the utilization of biogas for energy within a sustainable framework. We specifically explore biogas applications in rural and industrial settings, assess the environmental impacts, and discuss the regulatory landscape with insights from China and Europe. This study reveals that the strategic implementation of anaerobic digestion can markedly improve energy yield and sustainability, demonstrating how focused policies and advanced technological practices can optimize biogas utilization. The review enhances comprehension of environmental impacts, emphasizing insights from China and Europe as key examples. [ABSTRACT FROM AUTHOR]

In the context of climate change and the circular economy, most municipal wastewater treatment plants are not efficient because they generate huge amount of organic sludge, which in turn requires costly post-treatment by biological processes such as anaerobic digestion. An emerging solution is to add biochar to improve anaerobic digestion efficiency by enhancing microbial activity, aiding in the breakdown of complex organic compounds, producing more biogas, and promoting overall reactor stability. Here, we review the effects of adding biochar in anaerobic digestion, with emphasis on digester performance, process stability, biochar properties, and mechanisms. We discuss methane production, lag phase, electrical conductivity, volatile fatty acids, ammonia nitrogen, pH, and oxidation–reduction potential. We also review the process inhibition by biochar addition, with focus on phenols, heavy metals and microbial composition. Biochar properties are controlled by feedstock type, pyrolysis temperature, specific surface area, electrical conductivity, carbon and mineral content, electron exchange capacity, aromaticity, and particle size. We found that 6–16 g/L biochar supplementation consistently yielded higher cumulative specific methane compared to control without biochar, across diverse conditions and substrate types. Biochar's role is explained by four mechanisms: enhancing functional microbes, facilitating direct interspecies electron transfer, improving the degradation of refractory compounds, and increasing reactor stability. [ABSTRACT FROM AUTHOR]

Biochar production from biomass sources is a highly complex, multistep process that depends on several factors, including feedstock composition (e.g., type of biomass, particle size) and operating conditions (e.g., reaction temperature, pressure, residence time). However, the optimal set of variables for producing the maximum amount of biochar with the required characteristics can be determined by using machine learning (ML). In light of this, the purpose of this paper is to examine ML applications in biochar processes for the production of sustainable fuels. First, recent developments in the field are summarized, and then, a detailed review of ML applications in biochar production is presented. Following that, a bibliometric analysis is done to illustrate the major trends and construct a comprehensive perspective for future studies. It is found that biochar yield is the most common target variable for ML applications in biochar production. It is then concluded that ML can help to detect hidden patterns and make accurate predictions for determining the combination of variables that results in the desired properties of biochar which can be later used for decision-making, resource allocation, and fuel production. [ABSTRACT FROM AUTHOR]

Developing microbial consortia emerges as a new research frontier since complementing metabolisms provides new biotechnological capabilities for symbiotic interaction. To date, microalgal consortia with other microorganisms, such as fungi, bacteria, or other microalga are considered a biotechnological strategy to enhance microalgal physiological performance during CO2 removal from biogas—a gaseous by-product composed mainly of methane (CH4, 65–70%) and CO2 (25–30%) considered an energy source due to its high methane content. Today, microalga-microorganism interaction studies have focused on developing diverse microbial consortia to increase CO2 fixation of biogas and their metabolic changes during processing time. Thus, the present review proposes in a novel way the use of microalgal growth-promoting bacteria (MGPB) as a suitable partner to boost microalgal physiological performance and positively influence CO2 fixation from biogas. Furthermore, the MGPB mechanisms involved during MGPB-microalga interaction to mitigate or regulate microalgae metabolism under the stressful condition of this gaseous effluent and improve their biotechnological uses focusing on CO2 removal from biogas are analyzed and proposed. Additionally, the microalgal ability to convert CO2 from biogas into high-value biotechnological compounds of commercial interest is analyzed, including the economic feasibility and scalability of a microalga-MGPB consortium. This physiological knowledge of microalga-MGPG consortia notably warrants its real impact on different economic sectors as a bio-economy overview. Furthermore, the discussion between engineering and biological sciences facilitates the development of suitable bioprocesses based on microalgae. [ABSTRACT FROM AUTHOR]

Whey, a cheese production byproduct, can be anaerobically digested to reduce pollution and generate energy. Yet, stability is challenging due to organic content sensitivity and influent fluctuations. The present work attempts to implement the mechanistic model and machine learning (ML) models (support vector regression (SVR) and artificial neural networks (ANNs)) together to predict the concentration dataset of substrate 1 (S1) (i.e., carbohydrates and proteins), substrate 2 (S2) (i.e., glucids and amino acids), VFA, and methane (CH4) as a function of input independent variables, namely time and organic loading rate (OLR). The R2 values for S1, S2, VFA, and CH4 obtained through the mechanistic model remained as 0.953, 0.918, 0.84, and 0.976, respectively; for ANN models, 0.982, 0.928, 0.958, and 0.99; and for SVR models, 0.984, 0.939, 0.938, and 0.999, respectively. ML models have been discovered to be among the most precise and versatile compared to the mechanistic model. Moreover, other performance metrics, such as RMSE (0.022–2.177), MRE (0.007–0.100), and AARE (0.008–0.104) for ANN and RMSE (0.083–1.961), MRE (0.021–0.091), and AARE (0.037–0.089) for SVR, are obtained, indicating good prediction performances for both ML models. SVR and ANN models excel, aligning concentration curves to the optimum line when input parameters are adjusted, unlike the subpar traditional-based mechanistic model. Therefore, ML methods offer a tool to predict anaerobic digestion more effectively, enhancing design and operations. [ABSTRACT FROM AUTHOR]

Substantial amounts of expired dairy products (EDP) are generated due to their high perishability. These wastes are rich in organic matter, and their landfill disposal negatively impacts the environment. An alternative to reducing and recovering this waste would be to use it as a substrate in anaerobic digestion (AD) to produce biogas. This study investigated methane (CH4) production using different concentrations of EDP co-digested with synthetic domestic wastewater (SDW). Five anaerobic batch reactors (1000 mL) were assembled with different concentrations of EDP in SDW (500 mL working volume), namely (1) 0%, (2) 5.0%, (3) 7.5%, (4) 10.0%, and (5) 15.0% (v/v). COD removals were 81%, 84%, 80%, 89%, and 14% for assays 1 to 5, respectively. The cumulative CH4 productions were (mL/L) 717, 3354, 5327, 6584, and 1156 for assays 1 to 5, respectively. Assay 5 (15% EDP) was inhibited by volatile fatty acid (VFA) accumulation. However, assays 2, 3, and 4 (with 5.0–10.0% EDP) showed high CH4 yields (mLCH4/gVSadd) of 319, 333, and 317, respectively, demonstrating the feasibility of anaerobic co-digestion of EDP with SDW. In assays 3 and 4, a similar archaeal community structure was observed, dominated by the genera Methanosaeta, Methanolinea, Methanoregula, and Methanobacterium. In assay 2, the archaeal community demonstrated lower dominance due to insufficient substrate adaptation. This study confirms the viability of using EDP in AD systems to generate CH4, suggesting future sustainable applications for this residue. [ABSTRACT FROM AUTHOR]

Microplastic pollution has emerged as a global environmental concern, with pervasive contamination in terrestrial and aquatic ecosystems. This review paper delves into the intricate dynamics of microplastics within anaerobic digestion systems, addressing their occurrence, impact, and potential mitigation strategies. The occurrence of microplastics in anaerobic digesters is widespread, entering these systems through diverse inputs, such as sewage sludge, organic waste, and etc. Microplastics in anaerobic digestion have been associated with potential adverse impacts on biogas production, process performance, microbial communities, and degradation processes, though the relationship is complex and context dependent. This review highlights the urgent need for comprehensive research into the fate of microplastics within anaerobic digesters. Mitigation strategies offer promise in alleviating microplastic contamination, with advanced separation methods, innovative techniques such as magnetic micro-submarines, photocatalytic micro-motors, membrane bioreactors combined with activated carbon filters, rapid sand filtration, or conventional activated sludge, and disintegration-oriented techniques such as electrocatalysis, biodegradation, and thermal decomposition. Nonetheless, there is a significant knowledge gap that necessitates further research into the fate and long-term effects of microplastics in digestate. Collaborative efforts are crucial to addressing this emerging concern and ensuring the sustainability of anaerobic digestion systems in the face of microplastic challenges. [ABSTRACT FROM AUTHOR]

[Display omitted] • Comparison of different physical and enzymatic OFMSW pre-treatments. • Study of the pre-treatment effects on both the AD products: biogas and digestate. • Evaluation of the most energetically sustainable AD configurations. • Analyses of digestate quality in terms of nutrient content for the application as fertilizer. • UPP2 and cavitation are the best enzymatic and physical pre-treatments, respectively. This study optimized the anaerobic digestion (AD) of separated collected organic fractions of municipal solid waste (OFMSW) to produce energy and digestate as biofertilizer. Due to OFMSW's partial recalcitrance to degradation, enzymatic (UPP2, MCPS, USC4, USE2, A. niger) and physical (mechanical blending, heating, hydrodynamic cavitation) pre-treatments were tested. Experimental and modeling approaches were used to compare AD performance regarding energy sustainability and digestate quality. Digestate was separated into solid and liquid fractions, and then chemically and physically characterized by investigating the nutrient release mechanisms. Principal Component Analysis was applied, equally weighing energy and digestate productions. Unlike previous studies focusing only on biogas, this study evaluated the effects of pre-treatments on both biogas and digestate production, viewing AD as a biorefinery process for urban waste valorization. Results showed that all pre-treatments were energetically sustainable, but enzymatic pre-treatments yielded digestates richer in nutrients (increase of 80% N, 200% P and 150% K as compared to OFMSW) and with greater organic matter degradation compared to physical pre-treatments. The liquid fraction of digestate from enzymatic pre-treatments had higher nutrient concentrations, while those from physical pre-treatments had more balanced nutrient content, making them more suitable for fertigation. [ABSTRACT FROM AUTHOR]

This study evaluated the stability of anaerobic digestion and biogas production from the manure of laying hens fed diets containing different mineral sources and rosemary oil concentrations. Manure was obtained from 288 semi-heavy laying hens, 30 weeks old, and collected for 112 days. A completely randomized design was used in a 2×3 factorial scheme with repeated measures, considering two mineral sources (inorganic and organic) and three concentrations of rosemary oil (0, 100, and 200 mg kg-1). Twelve continuous bench digesters (7.5 kg) were operated with a hydraulic retention time of 30 days and daily loads of 5% total solids, for 90 days. A weekly analysis of influents and effluents was performed by measuring the values of total solids (TS), volatile solids (VS), pH, ammonia nitrogen (ammonia N), intermediary alkalinity (IA), partial alkalinity (PA), and the relationship IA:PA; biweekly analysis of total nitrogen (N) and total phosphorus (P) concentrations; and daily measurement of biogas production data to calculate the biogas production potential of the manure. Manure from laying hens fed with organic minerals has greater potential for biogas production and greater TS and VS reduction than manure from hens supplemented with inorganic minerals. Laying hen diets containing up to 200 mg kg-1 of rosemary oil do not present the risk of anaerobic digestion failure. [ABSTRACT FROM AUTHOR]

A key source of renewable energy, biogas (methane) was generated in the anaerobic mixed digestion of floral waste along with the combinations of other substrates. The present study has focused on the treatment of floral waste by anaerobic mix digestion along with co wastes named as canteen waste (CW), dairy waste (DW), and yard waste (YW) by using cow dung (CW) and sewage sludge (SS)as an inoculum. The concept of mixed digestion is used in this work by using different substrates with the main substrate as floral waste. The substrates are added with co substrates in a ratio of 2:1. Three types of comparative studies are carried out by making different combinations of substrates by keeping floral waste common in every combination. Different parameters responsible for the quantity of methane gas resulting from anaerobic digestion are optimized using design expert software's response surface methodology (RSM). A specially designed laboratory-scale model is used which is attached with a biogas analyser to continuously measure and analyse the generated biogas. A total of 45 experiments were carried out on the predicted conditions for different combinations. Parameters such as pH, temperature, and food to microorganism ratio have been chosen as independent variables. Daily biogas generation and cumulative biogas generation were recorded. COD removal efficiency recorded after eight days was in the range of 75-85%. Good interactions have been occurred among the independent variables chosen for the generation of biogas. Highest results were observed at optimum conditions (with pH = 7.2, F/M ratio = 2, T = 37°C). The cumulative biogas yield resulting from an experiment was 7.2L/kg VS. The average VS removal of 62-73% and TS removal of 45-55 % were recorded. [ABSTRACT FROM AUTHOR]

One of the alternative ways to obtain low-cost energy is to use biogas generated by the digestion process from sewage sludge. This paper presents an analysis of the processes in four anaerobic digesters (AD) - A, B, C and D. The study analyzed the amount of biogas produced in each digester tank and compared them with each other. Using data sets consisting of parameters relating to the pre-sludge and surplus sludge diverted to each tank, the effect of the proportion of these parameters on biogas production efficiency was studied. Based on this data, several models using different machine learning techniques were built and compared, which can be used to support the biogas production optimization process. A free convenient web tool written in Python language - AD2Biogas Predictor Tool - was also given away for sewage treatment plants to conveniently estimate the predicted amount of biogas produced on a given day using the implemented models. The main objective of the study is to understand how the studied parameters affect the efficiency of the process and identify potential optimization strategies, as well as to propose a model for biogas yield prediction based on sludge characteristics. The result of the study is to contribute to increasing the efficiency of sludge management in wastewater treatment plants and increasing biogas production, both in the form of developed models and a software tool. [ABSTRACT FROM AUTHOR]

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

The organic fertilizer (biogas slurry and biogas residues) was produced by the self-developed integrated device of "Pressure swirl / inclined plate sedimentation separation pretreatment (P/I) combined with ultrafiltration / reverse osmosis two stages membrane separation (UF/RO)". The paper focuses on the effect of concentrated biogas slurry and biogas residue produced by this technology on the yield and quality (vitamin C, soluble sugar, protein and nitrate content) of pepper as organic fertilizer compared with chemical fertilizer. The concentrated biogas slurry and biogas residue separated by this technology contained active substances such as N, P, K, trace elements and humic acids with stable composition and potential for good fertilization efficiency. The experiment of seed soaking for pepper sprouting confirmed the best effect of seed soaking with a concentration of 80% biogas slurry. Compared with chemical fertilizer treatment, the application of concentrated biogas slurry and biogas residue can improve the yield and quality of pepper, which is related to the nutrient elements in concentrated digestate. Meanwhile, the results of pepper cultivation trials show that the base fertilizer treatment of biogas residue is best with 2000kg/667m2 and foliar spraying of 75% biogas slurry. The results strongly demonstrate the great potential of the concentrated biogas slurry and biogas residue produced by the self-developed digestate concentration technology for pepper cultivation. [ABSTRACT FROM AUTHOR]

Environmental problems and the ever-increasing growth of population dictate the need for new methods to turn the problem into an opportunity. The recycling of agricultural waste is very important to achieve sustainable development of agriculture. Present paper focuses on how the proper disposal and recycling of agricultural waste can significantly reduce greenhouse gas emissions, conserve resources, and improve soil fertility. Hereupon, the specified criteria were determined by relevant organisations. Five final products including composting, biochar, biogas, reuse/recycling, and incineration resulting from the technologies used were investigated using the AHP technique. In addition to the effective management of agricultural waste, these technologies help in the production of electricity, fertiliser, and carbon absorption, which results in the reduction of climate change and the reduction of economy. Among the proposed products, biochar was preferred, and the incineration method was ranked the last. Biochar offers potential environmental benefits in terms of reducing greenhouse gas emissions, increasing the quality and quantity of agricultural products, and preventing soil erosion and degradation as well as water pollution. High rank was assigned to environmental criteria, and the actual waste production sub-criterion was preferred over other criteria with a weight of 0.170. The lowest weight was obtained for the shipping distance (weigh = 0.013). [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the anaerobic treatability and generation of potential valuable by-products of agro-food industry wastewaters where bulgur production is carried out. Among the agro-food products, bulgur which is a wheat product (Triticum spp.) and rich in fibers, is one of the ancient foods of Anatolia. The most critical issue in bulgur production is high energy and water consumption for cooking where wheat starch gelatinizes and results in a considerable amount of high strength wastewater. In the raw bulgur wastewater sample, 81% of total chemical oxygen demand (tCOD) was in soluble form which was readily fermentable and acidic by nature. Batch anaerobic study results indicated almost complete tCOD removal (99%) which decreased from 7820 to 100 mg/L. The cumulative methane yield was determined as 275 mL/g tCODfed. Hence, for such industrial wastewaters with high level of organic pollution, anaerobic biotechnology stands out as one of the most effective treatment options. Fermented bulgur wastewater was also tested for the production of polyhydroxyalkanoates (PHAs). It was determined that 37% of the tCOD could be recovered as PHAs without hindering the biogas generation. In this context, it was shown that PHAs and biogas production could be simultaneously achievable with a smart organic carbon utilization strategy which will also contribute to reduce energy requirement and carbon footprint of the industrial bulgur production process as well as create environmentally friendly solutions through resource recovery. [ABSTRACT FROM AUTHOR]

Over the past 45 years, anaerobic membrane bioreactor (AnMBR) technology has transitioned from laboratory-scale research to widespread successful implementation in various wastewater treatment applications, as part of sustainable technology initiatives. Compared to aerobic membrane bioreactor (AeMBR) and conventional anaerobic treatment methods, AnMBR offers numerous well-documented advantages, including efficient reduction of chemical oxygen demand (COD), conversion of organic waste into useful biogas, and production of treated effluent with less sludge generation. Nevertheless, employing AnMBR for treating low to moderate strength wastewater, such as domestic and municipal wastewater, continues to pose challenges due to concerns regarding membrane fouling and low bioenergy recovery efficiency. This article features last 11 year's publication statistics to visualize global research trends covering the historical development of AnMBRs and related areas, emphasizing key innovations and technological milestones that have driven their evolution in reactor configurations. It includes a performance comparison of AnMBRs across different wastewater treatments, presenting a tabulated analysis and critically discussed various performance parameters such as, COD removal efficiency, biogas production, biomass retention, and sludge generation. The discussion also covered the impact of operational and design parameters on AnMBR performance to enhance the depth of analysis. Despite its effectiveness, AnMBR frequently suffers from substantial membrane fouling and low degradation rate. While addressing such issues, this article also explores both conventional and modified approaches, including the use of bioelectrochemical techniques for fouling control and enhanced methane recovery. Finally, this paper highlights a comprehensive overview and identifies potential areas for future research pertaining to the prevailing issues. [ABSTRACT FROM AUTHOR]

The increased demand for energy worldwide and the focus on the green shift have raised interest in renewable energy sources such as biogas. During biogas production, sulphide (H2S, HS− and S2−) is generated as a byproduct. Due to its corrosive, toxic, odorous, and inhibitory nature, sulphide is problematic in various industrial processes. Therefore, several techniques have been developed to remove sulphide from liquid and gaseous streams, including chemical absorption, chemical dosing, bioscrubbers, and biological oxidation. This review aims to elucidate electrochemical and bioelectrochemical sulphide removal methods, which are gaining increasing interest as possible supplements to existing technologies. In these systems, the sulphide oxidation rate is affected by the reactor design and operational parameters, including electrode materials, anodic potential, pH, temperature and conductivity. Anodic and bioanodic materials are highlighted here, focusing on recent material developments and surface modification techniques. Moreover, the review focuses on sulphide generation and inhibition in biogas production processes and introduces the prospect of removing sulphide and producing methane in one single bioelectrochemical reactor. This could introduce BESs for combined biogas upgrading and cleaning, thereby increasing the methane content and removing pollutants such as sulphide and ammonia in one unit. [ABSTRACT FROM AUTHOR]

The rapid increase in global energy demand and the depletion of fossil fuels highlight the importance of biomass as a renewable energy source. Biomass, especially agricultural by-products rich in hemicellulose, cellulose, and lignin, offers a sustainable alternative for producing fuels and value-added products. The generation of power, heat, and biofuels from biomass has gained increasing significance in today's energy landscape. This review explores the potential of advanced biomass conversion technologies, with a focus on thermochemical and biochemical processes as key methods for optimizing agricultural waste management strategies. It examines these technologies for converting agricultural wastes into bioenergy, such as biogas, syngas, bio-oil, biochar, and digestate, while detailing their operational parameters, technological principles, and implementation prospects. While biological processes are limited by long processing times and low yields, thermochemical methods are challenged by high processing costs and temperature requirements. The review also compares the advantages and challenges of each method to assess their overall effectiveness and suitability. Further research in feedstock pretreatment, catalyst development, and system optimization is essential for advancing biofuel production. [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]

The document "Grand challenges in heat engines" published in the Frontiers in Thermal Engineering Journal discusses the historical impact, scientific challenges, and future directions of heat engines. It highlights key challenges such as reducing pollutant emissions, increasing thermal efficiency, and decarbonization through the use of alternative fuels like biofuels and e-fuels. The document emphasizes the importance of research and development efforts to address these challenges and improve the sustainability and efficiency of heat engines for various applications. [Extracted from the article]

The alarming rise in atmospheric CO2 levels, primarily driven by fossil fuel combustion and industrial processes, has become a major contributor to global climate change. Effective CO2 capture technologies are urgently needed, particularly for the selective removal of CO2 from industrial gas streams, such as flue gas and biogas, which often contain impurities like N2 and CH4. In this study, we report the design and synthesis of novel molecularly imprinted polymers (MIPs) using 4‐vinylpyridine (4VP) and methacrylic acid (MAA) as functional monomers, and thiophene (Th) and formaldehyde (HC) as molecular templates. The MIPs were specifically engineered to create selective molecular cavities within a nanoporous polymer matrix for the efficient capture of CO2. By adjusting the molar ratios of the template to functional monomers, we optimized the molecular imprinting process to enhance CO2 selectivity over N2 and CH4. The resulting MIPs exhibited outstanding performance, with a maximum CO2/N2 selectivity of 153 at 25 bar and CO2/CH4 selectivity of 25.3 at 1 bar, significantly surpassing previously reported porous polymers and metal‐organic frameworks (MOFs) under similar conditions. Furthermore, we conducted heat of adsorption studies, which revealed the strong and selective interaction of CO2 with the imprinted cavities, confirming the superior adsorption properties of the synthesized MIPs. The study demonstrates that molecular imprinting can effectively enhance both CO2 capture capacity and selectivity, providing a cost‐efficient and scalable solution for industrial CO2 separation and purification processes. [ABSTRACT FROM AUTHOR]

Lantana camara, one of the world's top ten most invasive species, was initially cultivated for ornamental use. However, it spread uncontrollably across the fallow areas and agricultural lands, threatening approximately 44% of Indian forests. Its invasion disrupts ecosystems by suppressing nearby plant growth through allelopathy and poses toxicity risks to grazing ruminants. It significantly increases forest fire risk by adding large amounts of combustible biomass, particularly dried L. camara. Despite efforts to control it using mechanical, chemical, and biocontrol methods, the results have been largely unsatisfactory, with associated costs estimated at $18,000 per square kilometre. Considering these challenges, recent research explored the potential of L. camara as a bioenergy resource. The L. camara briquettes exhibit a heating value of approximately 20 MJ/kg with a low sulphur (0.5%), nitrogen (1%), and ash content (2%), making them suitable for decentralised energy production. Furthermore, bioethanol production from L. camara hydrolysate has shown promising results, yielding 0.33 g/g with Pichia stipitis and 0.47 g/g with Saccharomyces cerevisiae, which is comparable to other lignocellulosic feedstocks. Additionally, the gasification of L. camara using a downdraft gasifier produced syngas with a lower heating value (LHV) of 6.4 MJ/Nm3. These findings demonstrate that using L. camara for bioenergy production presents a dual solution, addressing the growing demand for renewable energy and managing invasive species. This review aims to critically evaluate the potential and challenges associated with the different energy production pathways for L. camara, highlighting its role in sustainable energy generation. [ABSTRACT FROM AUTHOR]

To mitigate environmental emissions in the industrial nanosilica sector and promote its sustainable development, the life cycle assessment (LCA) method is employed to evaluate the environmental impacts throughout the life cycle of industrial precipitated nanosilica. This LCA spans from the acquisition and transportation of raw materials to the production of nanosilica. By identifying the critical contributing factors, effective optimization strategies have been proposed to enhance the environmental performance of the nanosilica life cycle. The effects of electricity, alkalis, acids, and steam on the life cycle emission factors of nanosilica were examined. The results indicate that substituting traditional coal power and steam with cleaner alternatives like wind energy, hydroelectric power, and solar power (both photovoltaic and thermal), as well as biogas steam, can lead to a significant reduction in the life cycle emission factors of nanosilica, ranging from 50% to 90%. Notably, the types of acids and alkalis used only significantly reduce certain environmental factors. These findings provide valuable theoretical insights and practical guidance for the industrial nanosilica sector, particularly in the areas of energy conservation, emission reduction, and the transition towards a lower-carbon economy. [ABSTRACT FROM AUTHOR]

This spatial analysis focuses on the relevant elements regarding the use of renewable energy sources, in particular, biogas, taking into account sustainability. The characteristics of the processes of biogas formation are presented, including the technological and biological aspects of its production. The issues of agricultural biogas plant profitability are discussed using examples from Poland, analyzing the economic and financial aspects of investing in this type of plant. Geospatial analysis supported by geographic information systems (GISs) looked at factors affecting the relief of the land and also the analysis of local plans or zoning decisions for the selected site. In addition, distance relationships and geological aspects taking into account terrain, landslides, and forestation, as well as hydrological aspects relating to flood and flooding hazards, were examined. It analyzed the availability of utility networks and proximity to road infrastructure. It was also examined that the proposed project will not have a negative impact on environmental protection. The analyzed site meets favorable conditions for the construction of the proposed project, and the conclusion drawn from this study is to emphasize the importance of integrating renewable energy sources with information systems to achieve sustainable development. [ABSTRACT FROM AUTHOR]

Biogas has improved due to technological advancements, environmental awareness, policy support, and research innovation, making it a more cost-effective and environmentally friendly renewable energy source. The Generalized Linear Model (GLM) was employed to examine the relationship between purchased and generated energy from 2007 to 2023. Metrics such as deviance, log likelihood, and dispersion phi were examined to assess model fit. The Mann–Kendall test was utilized to detect trends in energy datasets. Biochemical Oxygen Demand (BOD5) and Chemical Oxygen Demand (COD) reduction was significant, exceeding 97% from 2014 to 2023. However, treated sewage displayed limited susceptibility to biological degradation, with COD to BOD5 ratios increasing from 2.28 to 6.59 for raw sewage and from 2.33 to 7.05 for treated sewage by 2023. Additionally, the efficiency of sewage purification processes was calculated, and multivariate regression analysis was conducted on gas composition data. Principal Coordinate Ordination (PCO) and k-means clustering were used for dimensionality reduction and biogas component clustering, respectively. This research showed that biogas from the waste water treatment process can be used, particularly in methane production. Technological advancements have made biogas production more efficient, enhancing energy generation within a circular economy framework. [ABSTRACT FROM AUTHOR]

In this work, the recent achievements in the application of solid oxides fuel cells (SOFCs) are discussed. This paper summarizes the progress in two major topics: the materials for the electrolytes, anode, and cathode, and the fuels used, such as hydrocarbon, alcohol, and solid carbon fuels. Various aspects related to the development of new materials for the main components of the materials for electrocatalysts and for solid electrolytes (e.g., pure metals, metal alloys, high entropy oxides, cermets, perovskite oxides, Ruddlesden–Popper phase materials, scandia-stabilized-zirconia, perovskite oxides, and ceria-based solid electrolytes) are reported in a coherent and explanatory way. The selection of appropriate material for electrocatalysts and for solid electrolyte is crucial to achieve successful commercialization of the SOFC technology, since enhanced efficiency and increased life span is desirable. Based on the recent advancements, tests were conducted in a biogas-fueled Ni-YSZ/YSZ/GDC/LSC commercial cell, to elucidate the suitability of the LSC as an anode. Results obtained encourage the application of LSC as an anode in actual SOFC and SOFEC systems. Thus, H2-SOFC demonstrated a satisfying ASR value, while, for biogas-assisted electrolysis, the current values slightly increased compared to the methane-SOFEC, and for a 50/50 biogas mixture of methane and carbon dioxide, the corresponding value presented the higher increase. [ABSTRACT FROM AUTHOR]

Anaerobic digestion has the potential to convert organic waste materials into valuable energy. At the same time, using press water from biomass materials for energy generation while taking advantage of the resulting cake for other purposes is an emerging approach. Therefore, this study aimed to investigate the residual potential expected from a typical biogas feedstock after it has been mechanically separated into liquid and solid phases. Hence, in this study, the rumen contents of ruminants (cow, goat, and sheep) and their proportionate ratios were obtained from an abattoir in Ghana. Resource characterization of the waste samples was carried out in the central laboratory of the HFR, Germany. Anaerobic batch tests for biogas (biomethane) yield determination were set up using the Hohenheim Biogas Yield Test (HBT). The inoculum used was obtained from an inoculum production unit at the Hohenheim University biogas laboratory. The trial involved two different forms of the sample: mixture of rumen contents, press water, and inoculum, each in four (4) replicates. The trial was carried out at a mesophilic temperature of 37 °C. Results obtained over a seventy (70) day period were transformed into biogas yields. Overall, the results show that the current contents are suitable for biogas generation as an option as opposed to the current form of disposal at a refuse dump. However, using these mixtures in their original forms is more technically viable than using press water without further treatment. [ABSTRACT FROM AUTHOR]

Biogas is produced from organic materials, typically containing methane (CH 4) with content varying between 50% and 70%, and carbon dioxide (CO 2) ranging from 30% to 50%. It may also include hydrogen (H 2) with appropriate source material. Biogas is commonly utilized for power or heat generation in combined heat and power systems. The Homogeneous Charge Compression Ignition (HCCI) engine is well-suited for this purpose due to its efficient and rapid combustion process, with a lean air-fuel mixture. However, to limit the high pressure rise rate resulting from simultaneous premixed combustion in the engine cylinder, the combustion process must be controlled. The dilution inherent to this combustion mode helps in limiting the maximum cylinder temperature, and so the nitrogen oxides emissions. Moreover, particulate emissions can be lower than with diesel engine due to the homogeneous charge. Nonetheless, hydrocarbon (HC) and carbon monoxide (CO) levels are greater than those observed with spark ignition (SI) combustion. Additionally, high intake temperatures are needed to operate HCCI engines, depending on compression ratio, intake pressure, fuel type, and equivalence ratio. This paper focuses on an experimental study involving a modified diesel engine initially built for passenger vehicles, adapted to run in HCCI mode. Different fuel mixtures containing methane, hydrogen, and carbon dioxide with a fixed equivalence ratio of 0.4 were tested to reproduce an innovative biogas composition naturally containing hydrogen. The intake temperature and pressure were set according to the fuel mixtures to properly phase the combustion onset. A combustion analysis has been conducted to determine the effect of fuel composition on the combustion process. For each fuel type, the optimal intake pressure and temperature for achieving best combustion timing were identified, resulting in a peak indicated efficiency of 40% and specific NOx emissions as low as 0.1 g/kWh. Results show the effect of both CH 4 /H 2 ratios and CO 2 content as well as intake conditions on the load (IMEP), efficiencies, engine stress (i.e. pressure gradient) and emissions. [Display omitted] • Hydrogen reduces intake temperature and pressure requirements for HCCI combustion. • Maximum in-cylinder pressure is highly sensitive to intake temperature and pressure. • Findings indicated excellent combustion stability and Indicated efficiency of 40%. • Fuels containing CO 2 showed very low NOx emissions. [ABSTRACT FROM AUTHOR]

There is a growing recognition that food waste (FW) comprises a significant amount of unused energy. Indeed, FW shows great potential to produce methane (CH4)-rich biogas via an anaerobic digestion (AD) process. Nevertheless, to ensure high AD process performance, deepening the knowledge of FW characteristics is required. Furthermore, the biogas yield is strongly influenced by several operational parameters. Taking into account the above, in the current study, based on the data in the literature, the physicochemical parameters of FW generated throughout the world are presented and discussed. In addition, the performance profile of the single-stage anaerobic mono-digestion process with the use of FW as a feedstock was investigated. The performed analysis clearly demonstrated that FW is characterized by significant variations in several parameters, such as pH, the total solid (TS) and volatile solid (VS) contents, the volatile solids to total solids ratio (VS/TS), soluble chemical oxygen demand (sCOD), the concentrations of VFAs and ammonium nitrogen (NH4+-N), and the carbon-to-nitrogen ratio (C/N). Moreover, it was shown that the selected operational parameters, such as temperature, pH, the ratio of food waste to inoculum (I) (FW/I), and the organic loading rate (OLR), may have the most significant impact on the performance of the single-stage anaerobic mono-digestion process. In addition, it was found that most of the experimental investigations presented in the literature were conducted on a laboratory scale. Hence, in future research, more effort should be made to determine the biogas yield with the use of full-scale systems. To summarize, it should be clearly highlighted that the analysis presented in this study may have important implications for the management and application of FW as feedstock for an anaerobic mono-digestion process on an industrial scale. [ABSTRACT FROM AUTHOR]

Morocco is located in the northwestern part of Africa and is one of the Mediterranean countries threatened by the increasing generation of organic waste. Without any treatment or management strategy, these wastes are dumped illegally in large quantities and can affect natural resources. Recently, the anaerobic digestion method seems to be one of the best processes available to treat organic wastes. In the present study, the 15-m3 Puxin digester was used to produce biogas and digestate from cow dung. A total amount of 3500 kg of cattle dung was treated, generating a specific biogas production of 0.163 m3 kg−1 volatile solid. Furthermore, the application of the digestate diluted to 50% as biofertilizer for maize crop showed higher yield (P < 0.05) compared to the NPK fertilizer (45 quintals per ha and 33 quintals per ha respectively, i.e., + 36%) and the control (+ 80%). These valuable results can promote the development of biogas technology in Morocco as well as in similar countries. [ABSTRACT FROM AUTHOR]

Biogas is one of the renewable energy sources that may be used as an alternative. It can reduce negative environmental effects by producing electricity from agricultural waste and industrial effluents. This study intends to construct a lab-scale version of the VMMI instrument, which monitors the methane quality inside and outside the laboratory. In addition, this study aims to investigate the biogas upgradation by CO2 capture at atmospheric conditions utilizing three different alkaline absorbents (NaOH, Na2CO3, KOH) in the volumetric meter. To assess the efficiency of these alkaline solutions, an artificial biogas composition with a varied ratio of CO2 from 1 to 95% was prepared using natural gas as a methane source and CO2-filled cylinder. The biogas composition was analyzed on a gas chromatograph before and after CO2 absorption in an alkaline solution. In this study, potassium hydroxide had the maximum CO2 removal, 98%, compared to NaOH and Na2CO3. To further assess the effect of an acidic solvent, 1 M HCl acid was used, but it had a very low CO2 absorbing efficiency of 1.8%. Hence, major findings can help better understand proper alkaline solvent selection that contributes to high CO2 capture efficiency, easy use, and low cost. [ABSTRACT FROM AUTHOR]

Phytochemicals are potent inhibitors of in vivo ruminal microbial activity and methanogenesis of plant materials. However, a knowledge gap exists on the influence of phytochemicals on microbial ecology and biomethane production under anaerobic bioreactor environment. In this study, high-throughput metagenomic sequencing and physicochemical analyses were used to evaluate the effects of phytochemicals on the microbial community structure and methane production efficiency of different avocado oil processing wastes under standard batch anaerobic digestion (AD) over the 30-day period. Results showed that the avocado wastes produced methane yields (MY) ranging from 79 to 247 mL CH4/gVSadded, with skin/peels (AS), cold-pressed pomace (CDP), cold-pressed wastewater (CDW), and hot-pressed pomace (HDP) digestates showing diauxic methane production patterns and peak daily methane production at day 7. Avocado seed (AK) digestate, characterized by high phytochemical content, exhibited a monophasic methane production pattern and the lowest MY. Pseudomonas, Romboutsia, Paeniclostridium, and Methanocorpusculum, Methanosaeta, Methanoregula, and Methanosarcina were the dominant bacterial and archaeal genera in all digesters. Lipolytic Pseudomonas were enriched in the early AD phase (0–15 days), whereas Romboutsia, Paeniclostridium, and Clostridium increased in the late AD stage (days 13–30). Spearman correlation analyses showed that the total polyphenols and saponins exhibited a significant negative influence on biomethane production. Alkaloid level significantly affected Romboutsia, Paeniclostridium, and Methanoregula, while saponins negatively correlated to AC160630, Clostridium, Methanocorpusculum, and Methanoregula. To the best of our knowledge, this is the first report on the potential negative impact of phytochemicals on the microbial community structure and biomethane production from avocado processing wastes. [ABSTRACT FROM AUTHOR]

The aim of this study was to determine the feasibility of producing biogas by combining solid poultry slaughterhouse wastes (SPSWs) with fruit and vegetable solid wastes (FVSWs) and to obtain the optimum conditions for maximum biogas production by means of anaerobic digestion (AD). The ratio of available carbon to available nitrogen (C/N), as a critical parameter in producing methane, was adjusted by mixing the appropriate amount of SPSWs with FVSWs. For each load, a 50-L pilot-scale digester was operated for 40 days. For start-up and seeding, the biogas reactor was bioaugmented using the anaerobic sludge of an industrial poultry wastewater treatment plant. The analyzed SPSW, which had a C/N ratio of 5.75, was combined with FVSWs to obtain C/N ratios of 20, 30, and 40. Furthermore, it was found that the highest biogas yield occurred when the C/N ratio of the feed was 30. Also, for all three loading ratios, biogas production volumes were 215.1, 241, and 182.7 L, respectively, where methane's shares were 104.5, 120.6, and 91.7 L of the total gas volume that constituted 48.6, 50, and 50.2% of the produced biogas. Therefore, the obtained results from the process of mesophilic AD of this type of solid wastes illustrate that it is possible to efficiently produce biogas as a renewable energy source by combining SPSWs and FVSWs, instead of burning or burying them. [ABSTRACT FROM AUTHOR]

The increasing environmental pollution resulting from plastic waste and the need to reuse agro-industrial wastes as a source of discarding has led to the development of innovative biobased products. In the frame of this context, the use of neat polylactic acid (PLA) and its blend with polybutylene succinate (PBS) with or without cellulose nanocrystals (CNCs) extracted from hemp fibers is explored here. This study aimed to assess the biogas production of different biopolymeric films. In parallel, life cycle assessment (LCA) analysis was performed on the same films, focusing on their production phase and potential end-of-life scenarios, regardless of film durability (i.e., single-use packaging) and barrier performance, to counteract possible soil health threats. Specifically, this study considered three specific systems: PLA, PLA_PBS (PLA/PBS blend 80:20 w/w), and PLA_PBS_3CNC (PLA/PBS blend + 3% CNCs) films. The assessment involved a batch anaerobic digestion (AD) process at 52 °C, using digestate obtained from the anaerobic treatment of municipal waste as the inoculum and cellulose as a reference material. The AD process was monitored over about 30 days, revealing that reactors containing cellulose showed inherent biodegradability and enhanced biogas production. On the other hand, biopolymeric films based on PLA and its blends with PBS and CNCs exhibited an inhibitory effect, likely due to their recalcitrant nature, which can limit or delay microbial activity toward biomass degradation and methanogenesis. LCA analysis was performed taking into consideration the complex environmental implications of both including biopolymers in the production of renewable energy and the use of post-composting digestate as an organic fertilizer. Remarkably, the PLA_PBS_3CNC formulation revealed slightly superior performance in terms of biodegradability and biogas production, mainly correlated to the presence of CNCs in the blend. The observed enhanced biodegradability and biogas yield, coupled with the reduced environmental impact, confirm the key role of optimized biopolymeric formulations in mitigating inhibitory effects on AD processes while maximizing, at the same time, the utilization of naturally derived energy sources. [ABSTRACT FROM AUTHOR]

The modern world's major challenges, such as global warming, air pollution, and increasing energy demands, escalate the importance of sustainable development and transition toward renewables using innovative and environmentally friendly solutions, such as intensifying chemical processes, to reduce carbon footprints effectively. Aiming to enhance the process toward negative carbon emissions, this perspective explores the intensified membrane reactors for reducing the energy intensity of converting biogas into methanol, a versatile chemical feedstock, and renewable liquid fuel. Syngas and methanol synthesis processes, catalysts, and membranes were explored, and novel reactor designs were proposed. Introduction of selective membranes into the catalytic reaction zone to combine synthesis separation steps could enhance the system efficiency and intensify the process by recycling energy and materials, besides reducing costs and required energy for the separation process: the continuous harnessing of products shifts reactions toward desired species while recycling energy and materials enhances the process efficiency, and separating water from methanol reduces the required energy and costs of extra processes for methanol separation. The successful implementation of this technology holds significant promise for sustainable developments in producing chemicals and renewable fuel from renewable biogas and reducing methane and carbon dioxide emissions toward achieving carbon‐negative technologies. [ABSTRACT FROM AUTHOR]

In this study are presented the possibilities of using maize silage for biogas production. An experiment with maize silage took place over three years (2016–2018) in two localities, Ilandža, Alibunar municipality (L1—Locality 1) and Dolovo (L2—Locality 2), Serbia, and using two variants: a control with no digestate (C) and a variant with digestate, which was organic manure from biogas facilities (AD). In the AD variant, 50 t ha−1 of digestate was introduced into the soil just before sowing the maize. The following traits were examined: plant height (PH), biomass yield (BMY), biogas yield (BGY), and methane yield (MY). The effects of the studied factors (year, fertilization, and locality) on the biogas yield were significant (p < 0.5). The most favorable year for biogas production was 2016 (207.95 m3 ha−1), while the highest values of maize plant height, biomass, and methane yield were recorded in 2018 (2.48 m, 51.15 t ha−1 dry matter, and 258.25 m3 ha−1). The digestate exerted a significant influence (p < 0.5) on the values of all the tested maize parameters in all three experimental years. The biomass yield was positively associated with the plant height, biogas, and methane yield (r = 0.62 *; r = 0.70 *; r = 0.81 **) and positively but nonsignificantly associated with temperature (r = 0.42) and precipitation (r = 0.12). The application of the digestate before sowing improves the anaerobic digestion of maize silage and biogas production. [ABSTRACT FROM AUTHOR]

Organic waste has the potential to produce methane gas as a substitute for petrol-based fuels, while reducing landfilling and possible environmental pollution. Generally, anaerobic digestion (AD) is used only in wastewater treatment plants as a tertiary stage of sewage sludge treatment, generating a fraction of the energy that such process plants require. In this study, four different wastes—food waste (FW), dairy industry waste (DIW), brewery waste (BW), and cardboard waste (CBW)—were tested for biogas production. The biochemical methane potential (BMP) of each sample was evaluated using an automatic methane potential system (AMPTS). Operating parameters such as pH, temperature, total solids, and volatile solids were measured. Experiments on the anaerobic digestion of the samples were monitored under mesophilic conditions (temperature 37 °C, retention time 30 days). Specific methane yields (SMYs), as well as the theoretical methane potential (BMPth), were used to calculate the biodegradability of the substrates, obtaining the highest biodegradability for BW at 95.1% and producing 462.3 ± 1.25 NmL CH4/g volatile solids (VS), followed by FW at an inoculum-to-substrate ratio (ISR) of 2 at 84% generating 391.3 NmLCH4/g VS. The BMP test of the dairy industry waste at an inoculum-to-substrate ratio of 1 was heavily inhibited by bacteria overloading of the easily degradable organic matter, obtaining a total methane production of 106.3 NmL CH4/g VS and a biodegradability index of 24.8%. The kinetic modeling study demonstrated that the best-fitting model was the modified Gompertz model, presenting the highest coefficient of determination (R2) values, the lowest root means square error (RMSE) values for five of the substrates, and the best specific biogas yield estimation with a percentage difference ranging from 0.3 to 3.6%. [ABSTRACT FROM AUTHOR]

This proposed study aims to characterize and utilize the biogas (BG) derived from the anaerobic co‐digestion of university hostel food waste and Vinasse (waste from the sugarcane industry) in a digester and to run an agricultural diesel engine with BG and Jatropha Curcas methyl ester (JCMS) on a dual fuel (DF) mode. In DF mode, BG from food waste was the main fuel, and JCMS100 was the pilot (secondary) fuel. The engine was run at different BG flow rates as 4, 8, and 12 liters per minute (LPM) with JCMS100 as injected fuel. As per the author's earlier experimental findings, the fuel injection pressure for the JCMS100 was elevated to 240 bar from the base range of 200 bar to enhance the engine performance. The experimental findings for the JCMS, and BG operation were compared with diesel in all aspects. It was revealed that the NOx emission of JCMS100 + 12 LPM of BG was about 7.5% lower than the D100 fuel at full load. Increasing BG intake up to 8 LPM, the BTE increased, however, afterward it started to decline. In a similar consequence, the brake specific fuel consumption (BSFC) declined up to 8 LPM of BG, however, when the engine was fed with 12 LPM of BG the BSFC started to elevate. The carbon monoxide and hydrocarbon also elevated with higher induction of BG. However, interestingly a NOx‐smoke compromised tradeoff was observed for JCME‐BG operation. [ABSTRACT FROM AUTHOR]

Different technologies can be utilised to mitigate environmentally harmful ammonia (NH 3) emissions after field application of liquid animal manure (slurry). After a solid-liquid separation, air-plasma technology can acidify the liquid fraction and enrich its nutrient value by increasing the amount of inorganic nitrogen. The present work investigates the emissions of NH 3 and volatile organic compounds (VOC) after field application of the following fractions of pig slurry and slurry digestate: i) untreated slurry (UN), ii) liquid fraction of slurry (LF), iii) liquid fraction of slurry treated with air from the plasma treatment (LP). Emissions were measured with a system of wind tunnels and a cavity ring-down spectrometer for NH 3 concentration measurements and a proton-transfer-reaction mass-spectrometer for measurements of VOC. For both slurry types, the cumulative NH 3 emissions were in the following order UN > LF > LP. All the differences were significant (P < 0.05), except between pig slurry LF and LP. The reduction in cumulative NH 3 emission obtained by the treatments compared to UN were 55–74% and 70–89% for LF and LP, respectively. The slurry separation decreased dry matter by 46–54% and resulted in a rapid decrease in slurry exposed surface area after application, presumably due to high infiltration. Several VOCs were measured after application of the slurry, but continuous emission was undetectable for all VOCs. The very low VOC emission was presumably due to high infiltration of the low dry matter slurry treatments and low concentration of VOC in the digestate. Science4Impact Statement • Separation with decanter centrifuge reduced slurry DM by 46–54%. • Treatment with plasma treated air lowered slurry pH by 1.6–1.8 units. • Separation of slurry decreased cumulative NH 3 emissions by 55–74%. • Separation + treatment with plasma treated air reduced NH 3 emission by 70–89%. • All slurry types investigated had low VOC fluxes after application. [ABSTRACT FROM AUTHOR]

Digestate is a product with valuable fertilizing properties, remaining after the anaerobic fermentation process. An essential feature of the substance in question is its high water content of up to 97%. To improve the fertilizer value of the digestate, it is necessary to dehydrate it to produce a concentrated product. This paper determined the possibility of dewatering the digestate using an innovative reactor design. The study, conducted on a laboratory scale, used digestate from a Polish biogas plant. The dewatering technique described in the paper is based on the evaporation and condensation of water vapor on the inner surface of the reactor dome. The condensate accumulated on the leach trough and was directed to a storage tank. During the weeks of testing, 11.5 kg of condensate was separated from the initial weight of the digestate (32 kg), with a dry weight of 6.11%. The resulting condensate from dehydration had an average pH value of 9.0 and an average ammonium nitrogen content of 2.07 g∙kg−1. The economic calculations made in the paper allowed for estimating the expected savings associated with the management of digestate in Poland. The research showed the proposed technology's high potential for dewatering digestate under laboratory conditions. [ABSTRACT FROM AUTHOR]

Using biogas fuel in a modern internal combustion engine equipped with gas equipment of the fourth and fifth generations can create several difficulties. This is due to the low heat of combustion of untreated biogas, the presence of moisture, and the specifics of the injectors. The main problem of the studies we considered is that there are no data on the operating parameters of biogas fuel injectors. Studies on the parameters of the Matrix, Barracuda, Valtek, Hana, and Keihin injectors in relation to biogas fuel were carried out according to performance indicators, the linearity of operation, the resistance of the injectors, the ability to maintain factory parameters, and service life. According to the indicators of performance and linearity of work, Valtek injectors have the highest deviation in productivity and linearity of work, with an average of 38.8%, and the lowest deviation of Barracuda injectors is 7.5%. Keihin (15.3%) and Hana injectors (19.1%) also showed good performance indicators, and therefore can be used effectively for biogas fuel systems. As a result of research on the response time of the injectors, it was established that the best indicators were found for Hana (1.75 ms) and Keihin (1.99 ms) injectors. Valtek injectors showed good response rates (2.07 ms), as did Barracuda injectors (2.19 ms), but the highest response time was found in Matrix injectors, with 2.44 ms. Keihin injectors had the lowest average resistance value of 1.25 ohms, and Valtek injectors had the highest resistance value of 3 ohms. According to the research results, Keihin, Matrix, and Barracuda injectors provide the best ability to maintain factory performance when using biogas fuel at 2 to 5%, and Valtek had the worst performance up to 20%. Keihin, Barracuda, and Hana experimental injectors had the highest service life, which is from 200 to 250 thousand km of car mileage. The lowest indicators were found for Valtek and Matrix injectors, the service life of which varies from 70 to 100 thousand km of mileage. [ABSTRACT FROM AUTHOR]

This numerical study investigates the impact of the reaction temperature, molar ratio of CH4:CO2, and catalyst porosity (εp) on the H2 yield and H2 selectivity during biogas dry reforming over a Ni/Cr catalyst. Using COMSOL Multiphysics, we conducted detailed simulations to elucidate the underlying reaction characteristics. Our findings reveal that increasing εp from 0.1 to 0.95 significantly provides a 5 times increase in H2 production and a 2.3% increase in H2 selectivity while simultaneously reducing CO selectivity by 2.3%. This effect is attributed to the improved mass transfer within the catalyst bed, leading to more efficient reactant conversion and product formation. Additionally, we observed a strong correlation between higher reaction temperatures and increased H2 yield and H2 selectivity. By optimizing these operational parameters, our results suggest that Ni/Cr catalysts can be effectively employed for the sustainable production of H2 from biogas. [ABSTRACT FROM AUTHOR]