Search Results (1,717)

Amid the global renewable energy transition and rural revitalization, efficient organic waste use is critical for circular economy and carbon neutrality—core pillars of global sustainability. This study addresses unrecovered biogas slurry waste heat and biomass boiler thermal instability in Lindian County’s agricultural waste project. Using a small-scale experiment with MATLABR2023a simulations, it analyzed key parameters’ influence on mesophilic dry anaerobic fermentation, validating waste heat recovery and heat source optimization—measures closely aligned with sustainability goals. A novel multi-energy system for biogas fermentation integrated solar, biomass, and carbonization furnace residual heat. Experiments and simulations assessed heat demand, heating allocation, and economic performance. Findings showed 17-fold peak–valley heat demand fluctuations with seasonal patterns; 200 MJ load increments captured system dynamics. The multi-energy system outperformed single-energy setups in investment and operational costs. Optimal cost-effectiveness came with a 50%, 35%, and 15% heat load distribution among the solar, charcoal furnace, and biomass subsystems, cutting operational expenses. Results provide a robust framework for optimized biogas project design, aiding cost reduction, competitiveness, and circular economy and supporting China’s energy transition, rural revitalization, and the achievement of the sustainable development goals. Full article

Biogas from municipal solid waste is a promising pathway for renewable energy production while mitigating environmental pollution and public health risks. In this study, biogas emissions from a sanitary landfill in Maringá, southern Brazil, were evaluated using three models (IPCC, LandGEM, and CETESB tool) to estimate methane generation and energy recovery potential. Experimental analysis revealed methane concentrations from 51.10 ± 8.89% to 57.06 ± 1.19% across collection drains, indicating favorable conditions for energy utilization. Methane generation was estimated under different scenarios, reaching up to 1.30 × 10⁴ tonnes of CH₄, with peak production projected over 25–26 years depending on the model. Beyond energetic relevance, controlled biogas recovery can substantially reduce methane emissions, a key precursor of tropospheric ozone, and limit hazardous trace gas release, improving air quality and reducing population exposure to harmful pollutants. These findings are particularly relevant in developing countries, where insufficient waste management infrastructure leads to uncontrolled emissions, posing elevated environmental and health risks. This study supports integrating landfill biogas recovery into waste management and climate strategies, contributing to Sustainable Development Goals related to clean energy (SDG 7), climate action (SDG 13), and health (SDG 3), demonstrating it as a scalable solution for sustainable urban development. Full article

Biogas plants utilizing organic waste play an important role in the transition toward a circular economy and renewable energy systems. However, evaluating their actual performance is challenging due to the diversity of anaerobic digestion technologies, the wide range of feedstocks, and the use of various pretreatment methods. Consequently, assessing operational efficiency requires a comprehensive approach that goes beyond installed capacity alone. This paper synthesizes and systematizes existing approaches for evaluating the efficiency of biogas plants based on key operational indicators reported in the literature. The analysis considers a broad spectrum of feedstocks, highlighting the variability of input materials and their influence on plant performance. Particular attention is given to the internal energy consumption of electricity and heat, which directly affects net energy output and overall efficiency. The relationship between annual energy production (MWh) and installed capacity (MW) is analyzed as a core performance indicator enabling comparison between plants using different technologies, substrates, and scales. The proposed framework supports transparent performance assessment, operational optimization, and evidence-based decision-making in the development and management of waste-based biogas systems. Full article

Biogas production through anaerobic digestion is increasingly recognised as a strategic renewable energy pathway capable of addressing South Africa’s energy insecurity, organic waste management challenges, and climate mitigation goals. However, the water-intensive nature of anaerobic digestion raises critical sustainability concerns in water-scarce regions. This systematic review critically examines the water footprint of biogas-based bioenergy systems, with a specific focus on South Africa’s water-stressed context, to understand how water availability, feedstock selection, digester configuration, and governance frameworks influence system viability and scalability. This study adopts a systematic literature review (SLR) approach guided by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) methodology; peer-reviewed literature published between 2010 and 2025 was retrieved from Scopus and Web of Science and synthesised through descriptive analysis and qualitative meta-synthesis. The review integrates blue, green, and greywater footprint concepts to assess water use across diverse biogas pathways, including livestock manure, agricultural residues, food waste, wastewater sludge, and aquatic biomass. Findings indicate that wet digestion systems, dominant in South Africa, are highly sensitive to freshwater availability, particularly where slurry dilution relies on blue water. In contrast, wastewater-integrated, semi-wet, and co-digestion systems substantially reduce freshwater demand while enhancing methane yields and process stability. The reuse of greywater, industrial effluents, and digestate emerges as a key strategy for lowering water footprints and strengthening circular water–energy linkages. Despite strong technical potential, the adoption of water-efficient anaerobic digestion systems remains constrained by fragmented governance, infrastructure deficits, and limited empirical data on dry and low-water digestion technologies. The review concludes that embedding water footprint considerations into bioenergy planning, policy, and system design is essential for the sustainable expansion of biogas in South Africa. Integrated water–energy–waste governance, coupled with targeted technological innovation, is critical to ensuring that biogas development enhances both energy security and water sustainability in water-scarce regions. Full article

Agricultural soils are a major source of greenhouse gas (GHG) emissions, particularly carbon dioxide (CO₂) and methane (CH₄), highlighting the need for cost-effective and field-applicable monitoring solutions. This study developed and evaluated a low-cost real-time monitoring system for soil CO₂ and CH₄ emissions by integrating surface emission chambers, low-cost gas sensors, a solar-powered energy supply, and IoT-based wireless communication. Three acrylic chambers with different heights (40, 60, and 80 cm) were fabricated to investigate the influence of chamber geometry on measurement performance. System performance was assessed through simultaneous measurements against a Biogas 5000 analyzer under simulated conditions and during field deployment in a sugarcane cultivation area in Khon Kaen Province, Thailand. Relative agreement was used to compare the developed system with the reference instrument. The results showed that relative agreement varied with chamber height for both gases. Under simulated conditions, the 80 cm chamber achieved the highest overall relative agreement for CO₂ and CH₄, underscoring the importance of sufficient headspace volume in chamber-based measurements. Field experiments confirmed the system’s capability for continuous CO₂ monitoring in an agricultural environment. However, CH₄ emissions were not detected during the study period, likely due to drought-induced, well-aerated soil conditions. The developed system demonstrated stable autonomous operation, low energy consumption, and ease of installation, making it suitable for long-term field applications. Overall, the proposed platform provides a practical and scalable approach for real-time soil GHG monitoring and offers strong potential for integration into precision agriculture and climate-smart farming systems to support GHG mitigation strategies. Full article

Biogas upgrading to biomethane is an important route for increasing the energy value of renewable gas streams and enabling their wider use in fuel, heat, and power applications. In the present study, a two-stage membrane process for biogas upgrading was developed and validated using polysulfone (PSF) and polyetherimide (PEI) hollow-fiber membranes. The main original aspects of this work include the formulation of a PEI/DMF/IPA spinning dope composition (27/60/13 wt.%), the mixed-gas testing of PSF and PEI hollow-fiber membranes in a six-component model biogas mixture, and the combined simulation, experimental validation, and techno-economic evaluation of a two-stage membrane process. Mixed-gas permeation experiments with a six-component model biogas mixture were used as the basis for process simulation of four membrane-stage configurations. Only the PSF + PEI cascade simultaneously provided methane recovery above 90%, methane concentration in the product above 95 mol.%, and residual carbon dioxide content below 2 mol.%. Experimental verification confirmed the modeled process concept and demonstrated that the target biomethane quality was achieved at feed flow rates of 0.9–1.1 L min⁻¹, where methane recovery reached 93.5–95.2% and methane purity was 95.5–96.2 mol.%. A preliminary techno-economic analysis for a 100 m³ h⁻¹ unit indicated an upgrading penalty of USD 96.4 per ton of 95.5 mol.% CH₄. PSF membranes provided higher carbon dioxide permeance, whereas PEI membranes exhibited higher CO₂/CH₄ selectivity, which explains the efficiency of their combination in the two-stage scheme. The results show that the proposed PSF + PEI cascade is a promising membrane-based approach for energy-efficient biogas upgrading. Full article

To promote the sustainable management of marine aquaculture waste, this study investigated the effect of corn stover biochar (300 °C, 400 °C, and 500 °C) on the mesophilic anaerobic digestion (37 ± 1 °C) of particulate matter from seawater aquaculture wastewater. Batch experiments evaluated biochar’s effects on methane production, microbial succession, and antibiotic resistance genes (ARGs), and the correlation between ARG abundance and microbial taxa. Biochar addition significantly enhanced biogas production and shortened the lag phase. During 60 h fermentation, the optimal treatment achieved a methane yield of 291 mL, which was 164.55% higher than the control. Metagenomic sequencing revealed that biochar altered microbial community structure and ARG profiles, reducing the 11 most prevalent ARG types. Glycopeptide resistance genes showed the greatest reduction (15.02%). Correlation analysis identified Enterococcus, Peptostreptococcus, and Clostridium as major ARG hosts, accounting for 64.78–69.81% of total ARG abundance in the control and 68.14–76.17% in the biochar-amended group, confirming that Firmicutes are key potential ARG carriers in marine aquaculture particulate waste. From the perspective of sustainable development, biochar addition improves energy recovery from aquaculture waste and mitigates ARG dissemination risk. This study provides practical guidance for material selection and process optimization in sustainable aquaculture biogas projects, supporting the transition toward a circular bioeconomy. Full article

Biogas produced from the anaerobic digestion of organic matter holds much promise as a renewable energy source for decentralized systems. However, raw biogas contains substantial volumes of carbon dioxide, hydrogen sulfide, water vapor, and other trace impurities. These impurities can reduce the calorific value of biogas and limit its direct use for household energy needs. Purifying biogas to high-grade biomethane (≥95%) is therefore important to improve methane (CH₄) content and combustion characteristics. This is a guarantee of its safe utilization in domestic appliances, including cooking, heating, lighting, and electricity generation. This article reviews and evaluates novel approaches for upgrading raw biogas into high-purity biomethane that can offset natural gas in domestic applications. It further examines recent developments in conventional and innovative upgrading technologies such as water scrubbing, chemical scrubbing, pressure swing adsorption, membrane separation, cryogenic separation, and biological upgrading. Particular emphasis is placed on low-cost and small-scale solutions suitable for off-grid or mini-grid rural energy systems. Moreover, the role of process optimization, intelligent monitoring, and data-driven control methods in increasing CH₄ recovery and process efficiency is discussed. Despite their relatively high capital costs and energy needs, conventional technologies such as water scrubbing, pressure swing adsorption, and membrane technology continue to dominate biogas purification systems. The findings show that coupling advanced separation technologies, including cryogenic separation, biological upgrading, and hybrid technologies, with optimized process control can significantly improve CH₄ purity, save energy use, and enhance the overall consistency of biogas purification systems. These innovative strategies have strong potential to promote the full-scale adoption of biomethane as a clean, sustainable, and affordable energy source for decentralized applications, particularly in the developing world. Full article

Anaerobic digestion is crucial for safe treatment and energy recovery from municipal sludge. However, seasonal variations in sludge physicochemical properties challenge the continuous, stable operation of anaerobic digestion systems. To investigate the seasonal variations in characteristics of municipal sludge and their impact, this study collected sludge samples from a Beijing plant over a year, analyzed their properties and microbial communities, and evaluated their biogas potential through four-week batch anaerobic digestion tests. The results demonstrated that spring sludge exhibited the highest organic matter (68.7% of total solids, TS), including soluble proteins, sugars, and lipids, while the lignocellulose content peaked in autumn (17% TS). These fluctuations were primarily driven by variations in rainfall, temperature, and human activities. The microbial community shifted significantly: Proteiniclasticum and other hydrolytic bacteria were dominant in spring, whereas Candidatus_Microthrix was notably enriched in winter. Consequently, the biochemical methane potential (BMP) was highest in spring (342.5 mL/g volatile solids) and lowest in autumn (255.8 mL/g volatile solids). Spearman’s correlation analysis indicated a significant positive correlation between BMP and soluble protein content, and a weak negative correlation with cellulose content. These findings provide essential data support for seasonal regulation of sludge anaerobic digestion systems, facilitating strategies to achieve stable biogas production. Full article

Growing municipal solid wastes, environmental deterioration, and the world’s increasing energy demand highlight the urgent need for effective, sustainable energy recovery solutions. Uncontrolled municipal solid wastes contribute explicitly to the global crises of climate change, pollution, and biodiversity loss. Food and organic waste are converted into value-added products using biochemical and thermochemical techniques. Anaerobic digestion (AD) is a versatile, multi-phase waste-to-energy technology that transforms organic waste into renewable energy in an oxygen-free environment. AD uses microorganisms to break down waste, yielding biogas (mostly methane and carbon dioxide) and digestate, a nutrient-fortified by-product. Compared with traditional Single-Stage Anaerobic Digesters (SSAD), Two-Stage Anaerobic Digesters (TSAD) offer notable benefits by separating hydrolysis–acidogenesis from acetogenesis–methanogenesis. These include increased methane yield, improved process control, increased microbial stability, and resistance to inhibitory substances. According to the literature, TSAD systems have been shown to increase methane yield by about 10–30% compared to SSAD. This article covers the dynamics of the microbial population at various stages, the impact of operational factors (HRT, OLR, pH, and temperature), and novel reactor designs with modular and multi-state functions. In line with Oman’s Vision 2040, this study discusses the continuous operation of a two-phase AD co-digestion process and the in-depth techno-economic feasibility of decentralized waste management through optimized biogas production. Optimizing the carbon-to-nitrogen (C/N) ratio within the range of 20–30 in co-digestion systems significantly enhances microbial activity and methane production. The potential of recent developments, such as microbial immobilization, biogas generation techniques, and hybrid integration with photobioreactors or electrochemical systems, to enhance the scalability and efficiency of bioconversion is addressed in a TSAD system. In addition to encouraging circular economy principles through efficient organic waste valorization, this review identifies TSAD as a promising approach to achieving the SDGs related to sustainable cities, clean energy, and responsible consumption. Full article

In developing countries, final disposal sites exhibit different levels of operational control, which influence their environmental performance. This study evaluated the environmental performance of four types of final disposal sites in Mexico: sanitary landfill with energy recovery (SLF+ER) and sanitary landfill with gas flaring (SLFGF), controlled site (CS), and open dump (OD), using life cycle assessment for 1 t of municipal solid waste. Biogas generation was estimated using the Mexican Biogas Model 2.0, and Ecoinvent processes were adapted to local conditions; six impact categories were assessed, and a sensitivity analysis was conducted. The SLF+ER scenario showed the lowest impact in global warming, followed by SLFGF and CS, while OD recorded the highest impact, mainly associated with biogas management. In contrast, scenarios with gas capture and treatment showed higher contributions in categories related to combustion processes. Normalized results indicated that freshwater eutrophication and human carcinogenic toxicity are the dominant impact categories. The sensitivity analysis confirmed the influence of the organic fraction on CH₄ generation without altering the relative ranking among scenarios. Overall, increasing the level of environmental control reduces impacts from fugitive emissions but introduces trade-offs across other impact categories, highlighting the need for comprehensive assessments to support decision-making. Full article

Biogas is a renewable energy resource that is not only economical but also fulfills the criteria of net-zero carbon emissions. This is highly favorable for agriculture-based developing countries with an abundance of animal and agricultural waste that can be effectively utilized for biogas production. A dual-stage reactor was designed and built to investigate the optimal conditions during the different seasons of winter and summer for mesophilic biogas production utilizing cow manure from local dairy farms. During the experiments, the pH was continuously monitored and automatically controlled between 6.8 and 7.2 over a period of fifteen days for each experiment using an Arduino Mega controller. The weight ratio (r_w) of cow manure slurry was varied from 50% to 80%, and the optimal condition was found to be 70%, irrespective of the seasonal variations. However, the statistical analysis suggests that the optimal weight ratio is 66% for both seasons. A maximum reaction yield of 87% was achieved at a r_w value of 60% during the summer, with an expected yield of over 95% at a r_w value of 70% if similar extreme environmental conditions occur. Employing this apparatus for biogas production requires significant electrical energy to drive the stirrer and pumps, suggesting the use of a conventional underground setup for biogas production, integrated with an automatic pH control module. Full article

While silage maize (Zea mays L.) remains the dominant biogas feedstock crop in Germany, concerns about landscape homogenization and ecological risks have stimulated the search for more diverse energy crops. This study evaluated twelve amaranth genotypes (GT01–12; Amaranthus spp.) in southwest Germany using field experiments combined with biomass composition analysis and laboratory batch biogas assays. In contrast to earlier studies focusing primarily on the cultivar ‘Baernkraft’ (GT04), a broader set of genetic material was examined. Significant differences among GTs were observed for plant density, dry matter yield (DMY), dry matter content (DMC), and biomass composition. The most productive genotypes (GT09 and GT11) exceeded 10 Mg ha⁻¹ DMY, clearly outperforming Baernkraft. However, even these GTs did not reach the ≈28% DMC threshold considered necessary for reliable ensiling. Lignin concentrations ranged from 4.7% to 7.2% of dry matter. Methane concentrations remained relatively stable (54–55%), resulting in an average methane yield of 1788 ± 441 m³ CH₄ ha⁻¹ (maximum: 2677.8 m³ CH₄ ha⁻¹) across all genotypes and harvest dates. These findings indicate that amaranth may contribute to diversification of biogas cropping systems, although its agronomic and substrate-related performance remains inferior to that of maize under the conditions studied. Full article

Deammonification, which is based on partial nitritation and anammox (PN/A), is a well-established sidestream treatment for nitrogen removal. However, transferring deammonification to mainstream wastewater treatment remains challenging due to low temperatures, the need to retain slow-growing anammox bacteria (AnAOB), and their competition for nitrite with nitrite-oxidizing bacteria (NOB) and heterotrophic denitrifiers. This work investigates cubic polyurethane foam carriers to promote growth and retention of AnAOB. A moving bed biofilm reactor (MBBR) and an integrated fixed-film activated sludge (IFAS) reactor were compared over a three-year experimental period at lab-scale. The feasibility of the biofilm carriers for deammonification was first evaluated under sidestream conditions, followed by a stepwise transition to mainstream operational conditions. The impact of operational parameters, including dissolved oxygen concentration, pH value, and aeration strategy, was evaluated with respect to the activity of aerobic ammonium-oxidizing bacteria (AOB), NOB, and AnAOB, as well as nitrogen removal rates. Deammonification reached nitrogen removal rates of 0.04–0.12 kg N m⁻³ d⁻¹ (IFAS reactor) and 0.02–0.28 kg N m⁻³ d⁻¹ (MBBR) at subphases with reactor bulk concentrations above 60 mg NH₄-N L⁻¹. Highest nitrogen removal degrees of 77 ± 6% (IFAS) and 76 ± 5% (MBBR) were achieved at reactor bulk concentrations of 96 mg NH₄ L⁻¹ and 97 mg NH₄ L⁻¹, respectively. Lower concentrations triggered NOB activity in both reactors, leading to an increase in nitrate concentration up to 22 mg NO₃-N L⁻¹. AOB and AnAOB activities were on average 6-fold higher on the carriers compared to suspended biomass throughout all experimental phases, demonstrating the feasibility of using cubic polyurethane foam carriers for deammonification. This was also confirmed by fluorescence in-situ hybridization (FISH) measurements. Median nitrogen removal rates over all experimental phases of 0.07 kg N m⁻³ d⁻¹ for the IFAS reactor and 0.05 kg N m⁻³ d⁻¹ for the MBBR were achieved, which are comparable to conventional activated sludge systems performing nitrogen removal via nitrification–denitrification. While at lower nitrogen concentrations, the IFAS reactor yielded superior nitrogen removal rates, peak nitrogen removal rates of 0.28 kg N m⁻³ d⁻¹ were measured in the MBBR configuration. However, controlling NOB activity at lower temperatures and concentrations remains a challenge in MBBR and IFAS configurations. In our study, in the IFAS reactor NOB activities were visible on fewer days than in MBBR. At mainstream-like conditions, higher nitrogen removal rates of IFAS (0.09–0.12 kg N m⁻³ d⁻¹) were achieved compared to the MBBR (0.06–0.09 kg N m⁻³ d⁻¹). This demonstrates the advantage of the IFAS reactor in treating mainstream wastewater via deammonification. As an autotrophic nitrogen removal process, the implementation of deammonification in the mainstream of municipal wastewater treatment plants enables enhanced recovery of biogas from sewage organic matter. The latter would otherwise be consumed during the conventional nitrification-denitrification pathway. Consequently, the overall energy balance for wastewater treatment can be improved, contributing to a more environmentally sustainable process. Full article

Energy transition includes the substitution of centralized energy systems with decentralized variable renewable energy sources (vRES), the growth of which brings drawbacks such as grid congestion and intermittency. These issues are increasingly troublesome in many local energy systems, including in The Netherlands. Biogas may provide options to provide backup renewable energy in times of energy supply uncertainty. In The Netherlands, the consideration of biogas in such functions is limited. Meanwhile, local energy initiatives (LEIs) are spearheading the adoption of vRES. Because of concern over local grid balancing, LEIs may want or need to innovate and diversify their activities. Such innovation could include bioenergy in general, and biogas specifically. However, only a small number of LEIs consider bioenergy, and Dutch LEIs seem hesitant to venture into biogas specifically. In this paper we explore the question of what hinders adoption of biogas in The Netherlands in general, and by LEIs specifically, deploying an approach based on the technological innovation systems (TIS) concept. In that approach, we take insights from current and expected policy in The Netherlands juxtaposed with insights from similar countries surrounding The Netherlands. We conclude that historic developments in biogas already created a moderately supportive platform for large-scale biogas development, but some essential factors remain inadequately developed. Key barriers to biogas innovation, especially for LEIs, are insufficient mobilization of financial and knowledge resources, and insufficient attention to alleviating preconceptions. Dependable support and attention for socio-economic factors in policymaking would improve conditions associated with resources, preconceptions and resistance, and the situation for LEIs to explore the potential of biogas. However, it remains uncertain whether such measures would be sufficient to improve the potential of local biogas utilization in The Netherlands in a way that opens a role for biogas in solving energy transition challenges such as energy system balancing. Full article