Search Results (547)

In Abidjan, the treatment of pig waste is becoming a priority given the continued growth of pig farms, which readily reuse manure as organic fertilizer. This study evaluated the effectiveness of anaerobic digestion for simultaneous biogas production and pathogen reduction from pig farm residues. Two 1600 L biodigesters were installed at pig farms in Port Bouët (PBk) and Abobo (Ab). They were fed with pig manure and water (1:4 ratio) and monitored over 56 days. The total biogas production was 22.63 m³ and 16.31 m³ for the PBk and Ab digesters, respectively, with peak production occurring between days 14 and 28. Following biofilter treatment, the methane content increased to 80–82%, yielding potential energy outputs of 2.32–3.29 kWh/d, with optimal production occurring at a pH of 7.28–7.76. The COD, BOD₅, organic acid, and total nitrogen levels decreased progressively in the biodigesters, while the mineral element content remained almost unchanged. Complete elimination was achieved for most of the bacteria tested (E. coli, Enterococcus, Salmonella, etc.). However, Bacillus and Clostridium were able to persist, albeit with significant reductions of between 3.11 and 5.79 log₁₀. Anaerobic digestion is an effective method of combining waste treatment and energy recovery. It eliminates major pathogens while producing valuable biogas. This makes it a sustainable waste management solution for urban agricultural systems. Full article

There has been significant interest in deploying unmanned aerial vehicles (UAVs) for their ability to perform precise and rapid remote mapping and inspection of critical environmental assets for structural health monitoring. This case study investigates the use of UAV-based LiDAR and photogrammetry at Melbourne Water’s Western Treatment Plant (WTP) to routinely monitor high-density polyethylene floating covers on anaerobic lagoons. The proposed approach integrates LiDAR and photogrammetry data to enhance the accuracy and efficiency of generating digital elevation models (DEMs) and orthomosaics by leveraging the strengths of both methods. Specifically, the photogrammetric images were orthorectified onto LiDAR-derived DEMs as the projection plane to construct the corresponding orthomosaic. This method captures precise elevation points directly from LiDAR, forming a robust foundation dataset for DEM construction. This streamlines the workflow without compromising detail, as it eliminates the need for time-intensive photogrammetry processes, such as dense cloud and depth map generation. This integration accelerates dataset production by up to four times compared to photogrammetry alone, while achieving centimetre-level accuracy. The LiDAR-derived DEM achieved higher elevation accuracy with a root mean square error (RMSE) of 56.1 mm, while the photogrammetry-derived DEM achieved higher in-plane accuracy with an RMSE of up to 35.4 mm. An analysis of cover deformation revealed that the floating cover had elevated rapidly within the first two years post-installation before showing lateral displacement around the sixth year, which was also evident from a significant increase in wrinkling. This approach delivers valuable insights into cover condition that, in turn, clarifies scum accumulation and movement, thereby enhancing structural integrity management and supporting environmental sustainability at WTP by safeguarding methane-rich biogas for renewable-energy generation and controlling odours. The findings support the ongoing collaborative industry research between Monash University and Melbourne Water, aimed at achieving comprehensive structural and prognostic health assessments of these high-value assets. Full article

Global concerns about resource depletion, climate change, and nutrient pollution in aquatic systems are compelling a transition towards zero-waste industries. With the skyrocketing carbon footprint of the modern fertiliser industry, sustainable options are highly sought after. Anaerobic digestion of organic waste to generate renewable biogas and fertiliser production from the residual nutrient-rich digestate are promising nutrient recovery and recycling avenues. This review explores the potential use of anaerobic digestate to develop value-added agronomic products, focusing on the quality and safety parameters pivotal to its fertiliser value. A comprehensive review of conventional and cutting-edge technologies available for digestate processing into organic/organo-mineral fertilisers has been conducted, highlighting emerging sustainable approaches. Specifically, this review unravels novel aspects of enhancing digestate quality with biostimulants such as plant growth-promoting rhizobacteria, humic substances and biochar for biofertiliser/slow-release fertiliser production. Additionally, methods and guidelines to assess and address environmental impacts by digestate application on croplands and challenges in the commercialisation of digestate-based fertilisers were analysed. This review also underscores the importance of valorising anaerobic digestate as a fertiliser in implementing a circular bioeconomy within the agroindustry. Full article

Microalgae are considered to be a dual solution for CO₂ fixation and biogas slurry purification due to their high photosynthetic efficiency and strong environmental adaptability. However, their application is constrained by the low solubility of CO₂ in the solution environment, which restricts microalgal growth, resulting in low biomass production and poor slurry purification efficiency. In this study, we developed MgFe layered double hydroxide (LDH) that spontaneously combined with Chlorella pyrenoidosa to help it concentrate CO₂, thereby increasing biomass yield and purification capacity for food waste biogas slurry. The prepared MgFe-LDH exhibited a typical layered structure with a CO₂ adsorption capacity of 4.44 mmol/g. MgFe-LDH and C. pyrenoidosa carried opposite charges, enabling successful self-assembly via electrostatic interaction. Compared with the control, the addition of 200 ppm MgFe-LDH increased C. pyrenoidosa biomass and pigment content by 36.82% and 63.05%, respectively. The removal efficiencies of total nitrogen, total phosphorus, and ammonia nitrogen in the slurry were enhanced by 20.04%, 31.54% and 14.57%, respectively. The addition of LDH effectively alleviated oxidative stress in C. pyrenoidosa and stimulated the secretion of extracellular polymeric substances, thereby enhancing the stress resistance and pollutant adsorption capabilities. These findings provided a new strategy for the industrial application of microalgal technology in CO₂ fixation and wastewater treatment. Full article

The purpose of this study was to evaluate the production of biogas and the digestate obtained by means of the anaerobic digestion of sargassum, and its anaerobic co-digestion with municipal solid waste, while considering the effect of particle size and the carbon–nitrogen ratio (C:N) on methane generation. Physicochemical analyses of both Sargassum and the digestate were performed, including ultimate analysis and heavy metal content. The highest methane yield (92.62 mL CH₄/gVS) was achieved with a 2 mm particle size and a C:N ratio of 15. Digestate characterization revealed the presence of arsenic and zinc, indicating the need for additional treatment before agricultural use. The agronomic potential of Sargassum digestate was assessed by comparing it with livestock waste, humus, and garden soil in tomato seedling growth trials. The Sargassum-based digestate significantly enhanced seedling biomass and development, supporting its potential as a sustainable soil amendment. Overall, the findings confirm the viability of Sargassum as a feedstock for biogas and biofertilizer production, emphasizing the importance of contaminant monitoring to ensure environmental safety. This study supports the integration of Sargassum into circular economy strategies and regenerative agricultural systems. Full article

Second-, third-, and fourth-generation biofuels represent an important response to the challenges of clean energy supply and climate change. In this context, the Horizon 2020 “TO-SYN-FUEL” project aimed to produce advanced biofuels together with phosphorus from municipal wastewater sludge through a combination of technologies including a Thermo-Catalytic Reforming system, Pressure Swing Adsorption for hydrogen separation, Hydrodeoxygenation, and biochar gasification for phosphorous recovery. This article presents the environmental performance results of the demonstrator installed in Hohenberg (Germany), with a capacity of 500 kg per hour of dried sewage sludge. In addition, four alternative scenarios are assessed, differing in the source of additional thermal energy used for sludge drying: natural gas, biogas, heat pump, and a hybrid solar greenhouse. The environmental performance of these scenarios is then compared with that of conventional fuel. The comparative study of these scenarios demonstrates that the biofuel obtained through wood gasification complies with the Renewable Energy Directive, while natural gas remains the least sustainable option. Heat pumps, biogas, and greenhouse drying emerge as promising alternatives to align biofuel production with EU sustainability targets. Phosphorus recovery from sewage sludge ash proves essential for compliance, offering clear environmental benefits. Although sewage sludge is challenging due to its high water content, it represents a valuable feedstock whose sustainable management can enhance both energy recovery and nutrient recycling. Full article

Whether voluntary carbon markets can effectively contribute to climate mitigation remains a debated issue. Taking Chinese Certified Emission Reduction (CCER) projects as a quasi-natural experiment, this study employed a difference-in-difference approach calibrated with a county-level panel dataset spanning 2008–2021 to examine the carbon abatement effect of CCER projects. The results show that CCER projects reduced county-level emissions by 2.8%, though this reduction falls short of the levels self-declared by project developers, implying the possibility of overstating emission reductions. The carbon abatement effect is more pronounced in biogas projects and projects verified by large agencies, underscoring the mitigation potential of biogas deployment as well as the importance of professional expertise in enhancing project quality. In addition, CCER projects generate a range of socio-economic benefits, including raising income, creating employment opportunities, and preserving farmland. Overall, this study identified the effectiveness of voluntary carbon markets, providing valuable insights for fostering their further sustainable development. Full article

This study aimed to evaluate the potential benefits of co-digesting rapeseed oil cake, a by-product of biodiesel production, with microalgal biomass. Anaerobic fermentation was carried out under mesophilic conditions using various doses of press residue as a co-substrate. The results demonstrate that the addition of rapeseed oil cake enhances biogas production. The highest biogas yield was achieved during co-digestion with 1 g VS·L⁻¹ of microalgal biomass and 0.5 g VS·L⁻¹ of rapeseed oil cake. The average methane content in the biogas was 62.42%. The average hydrogen sulfide concentration ranged from 400 to 700 ppm. The maximum energy yield of 3.76 kWh·kg⁻¹ DM was obtained from co-digesting microalgal and rapeseed oil cake biomass in a 2:1 ratio. Full article

Bamboo (subfamily Bambusoideae, Poaceae) ranks among the fastest-growing plants on Earth, achieving up to 1 m day⁻¹, significantly faster than other fast growing woody plant such as Eucalyptus (up to 0.6 m day⁻¹) and Populus (up to 0.5 m day⁻¹). Native to Asia, South America and Africa, and cultivated on approximately 37 million ha worldwide, bamboo delivers multifaceted environmental, social, and economic benefits. Historically central to construction, handicrafts, paper and cuisine, bamboo has evolved into a high-value cash crop and green innovation platform. Its rapid renewability allows multiple harvests of young shoots in fast-growing species such as Phyllostachys edulis and Dendrocalamus asper. Its high tensile strength, flexibility, and ecological adaptability make it suitable for applications in bioenergy (bioethanol, biogas, biochar), advanced materials (engineered composites, textiles, activated carbon), and biotechnology (fermentable sugars, prebiotics, biochemicals). Bamboo shoots and leaves provide essential nutrients, antioxidants and bioactive compounds with documented health and pharmaceutical potential. With a global market value exceeding USD 41 billion, bamboo demand continues to grow in response to the call for sustainable materials. Ecologically, bamboo sequesters up to 259 t C ha⁻¹, stabilizes soil, enhances agroforestry systems and enables phytoremediation of degraded lands. Nonetheless, challenges persist, including species- and age-dependent mechanical variability; vulnerability to decay and pests; flammability; lack of standardized harvesting and engineering codes; and environmental impacts of certain processing methods. This review traces bamboo’s trajectory from a traditional resource to a strategic bioresource aligned with Industry 5.0, underscores its role in low-emission, circular bioeconomies and identifies pathways for optimized cultivation, green processing technologies and integration into carbon-credit frameworks. By addressing these challenges through innovation and policy support, bamboo can underpin resilient, human-centric economies and drive sustainable development. Full article

This study was conducted to investigate the effect of hydrogen peroxide (H₂O₂) pretreatment on the anaerobic digestion performance of dairy wastewater. Initial physicochemical characterization revealed that the substrate is highly enriched in volatile solids (approximately 90.67%), indicating its strong potential for anaerobic biodegradation. Given this favorable composition, biochemical methane potential (BMP) assays were performed under mesophilic conditions (37 °C) to quantify biogas and methane generation from the untreated and pretreated dairy effluent. To enhance substrate biodegradability and increase methane yield, an oxidative pretreatment using various doses of H₂O₂ was applied. This pretreatment aimed to disrupt the complex organic matter and promote the solubilization of chemical oxygen demand (COD), especially in its soluble form (sCOD), which is more readily assimilated by methanogenic microorganisms. The experimental results demonstrated a significant improvement in biogas production efficiency. While the untreated sample yielded approximately 100 mL CH₄/g VS, the pretreated substrate achieved a maximum of 168 mL CH₄/g VS, marking a substantial enhancement. Gas composition analysis further revealed that methane accounted for nearly 45% of the total biogas produced under optimal conditions. The dosage of 0.2 g H₂O₂ per g of volatile solids (VS) resulted in the highest improvement in methane production after thermal treatment C1, followed by 1.35 g H₂O₂/g VS, and then 0.5 g H₂O₂/g VS. Furthermore, the kinetics of methane production were assessed by fitting the experimental data to the modified Gompertz model. This model enabled the determination of key parameters, such as the maximum specific methane production rate and the duration of the lag phase. The high coefficient of determination (R²) values obtained confirmed the excellent agreement between the experimental data and the model predictions, highlighting the robustness and reliability of the modified Gompertz model in describing the anaerobic digestion process of dairy waste subjected to oxidative pretreatment. Full article

Anaerobic digestion (AD) is an environmentally sustainable approach for managing invasive plants species, mitigating pollution, and generating renewable energy. However, the complex structure of these biomasses limits their biodegradability and necessitates pretreatment to enhance methane production. This study explored the biotransformation of two invasive species, Reynoutria japonica and Phragmites australis, harvested across diverse phenological stages. Bioprocess intensification was achieved through a single-stage process using a hydrolytic–methanogenic consortium under thermophilic conditions (55 °C, 25 days). The impact of harvest timing distinct plant fractions (shoot vs. root) on biogas production was meticulously evaluated. Results revealed progressive biogas production. Notably, winter-harvested shoot fractions exhibited the highest methane-rich biogas, achieving 551.12 ± 33.07 mL/g VS for Reynoutria and 401.42 ± 24.09 mL/g VS for Phragmites. The resulting digestate demonstrates a rich composition of essential macronutrients (N-P-K) vital for plant growth, highlighting its potential as a valuable biofertilizer. Significantly, complete inhibition of seed germination was observed, confirming the process’s efficacy in preventing the further propagation of invasive species. This research underscores that thermophilic anaerobic digestion, coupled with hydrolytic treatment, is a significant advancement in the valorization of invasive biomasses, contributing to both renewable energy production and ecological recovery. Full article

Anaerobic digestion (AD) effectively treats organic waste and biomass. This process recovers energy as biogas, while a by-product known as digestate requires proper treatment. The goal of enhancing biogas production as a way of increasing the share of renewable fuels in the transport and industrial sectors comes with the drawback of managing digestates. When digestate cannot be used as an organic amendment, thermal processes provide alternatives for producing valuable energy products. Hydrothermal treatment is particularly promising due to its lower thermal requirements when paired with anaerobic digestion (AD), unlike gasification or pyrolysis. However, challenges such as managing by-products like process water and hydrochar contaminants, along with high operating and maintenance costs, need to be addressed before these technologies can be widely adopted in digestion plants. The present document reviews the current state of the art in hydrothermal carbonization and liquefaction as technologies for treating digestate, focusing on the key aspects that require further research and development. This review examines the existing gaps in the treatment and management of process water, as well as the techno-economic barriers faced when deploying hydrochar-related technologies and integrating them with digestion plants. Full article

Anaerobic digestion (AD) plays a crucial role in renewable energy production and waste management by converting organic waste into biogas and reduces greenhouse gas emissions. Optimized bioreactor performance depends on two main categories of factors: (1) reactor and geometric factors of agitator geometry, blade configuration, rotational speed, torque, power consumption, and the impeller-to-tank ration (d/D), and (2) fluid property factors of viscosity and flow characteristics, which relates turbulence, circulation patters, and stratification. Impeller power strongly influences nutrient distribution, gas exchange, and temperature uniformity within the reactor. While higher power inputs improve turbulence and prevent stratification, they also increase energy demand. This study evaluated fifteen blade configurations to determine the optimal fluid circulation using ANSYS 2024 R1 Fluent simulations. The bioreactor tank, with a diameter of 0.130 m and a height of 0.225 m, was tested at speeds ranging from 40 to 150 RPM. Among the single-blade configurations, the curved blade achieved the highest velocity at 0.521 m/s, generating localized circulations. The Rushton blade produced strong radial flows with a velocity of 0.364 m/s, while the propeller blade reached 0.254 m/s, supporting axial flow. In double-blade arrangements, the curved-propeller combination exhibited velocities between 0.261 and 0.342 m/s, enhancing fluid motion. The three-blade configurations resulted in the highest power consumption, ranging from 1.94 W to 1.99 W, with power increasing at higher RPMs and larger impeller sizes. However, torque values decreased over time. The most efficient mixing was achieved at moderate RPMs (80–120) and an impeller-to-tank diameter ratio (d/D) of approximately 0.75. These findings highlight the significance of blade selection in balancing mixing efficiency and energy consumption for scalable AD systems. Full article

This study addresses volatile fatty acid (VFA) accumulation, a key issue limiting methane fermentation under high organic loading rate (OLR) conditions. Batch experiments were conducted with GAC (0–10%) under various OLRs (1:0.5–1:10) to investigate its effect on biogas yield, methane purity, and microbial interactions. Higher GAC levels (7.5% and 10%) significantly enhanced biogas production (750–800 mL/g VS) and methane concentration (–70%) while shortening stabilization time. A continuous system with 10% GAC showed suppressed VFA accumulation, stable pH (7.0–8.1), and improved organic matter degradation. This work quantitatively evaluates the link between GAC dosage, DIET induction, and microbial community shifts under high OLR. These findings highlight GAC as an operationally simple and potentially cost-beneficial strategy for stabilizing methane fermentation, particularly in decentralized or small-scale applications. Full article

This study provides a comprehensive review of the application of pulsed electric field (PEF) technology as a pretreatment method for enhancing biogas production from various organic substrates. A comparative bibliometric analysis was conducted using four databases, Web of Science Core Collection, Scopus, Dimensions, and Google Scholar, to evaluate research activity, interdisciplinarity, and geographic distribution of PEF-related literature. The results show that, although biomass pretreatment research has grown considerably over the past two decades, the number of studies focused specifically on PEF remains extremely low, accounting for less than 0.5% in each database. A detailed overview of 66 studies further confirms PEF’s potential to improve methane yield through substrate disintegration and microbial community enhancement, yet highlights the need for standardization and scalability. Optimization studies reveal promising outcomes, particularly for sludge and algal substrates, though most were limited to laboratory scale. Two full-scale studies demonstrated economic feasibility, yet long-term stability, energy balance, and integration into existing anaerobic digestion systems remain underexplored. The analysis of author countries and institutions shows that research is concentrated in China, Sweden, and France. Overall, this review identifies major research gaps and outlines future directions aimed at including a more diverse range of substrates, improving comparability, and validating PEF in real-scale biogas production systems. Full article