Search Results (453)

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

Promoting the agricultural recycling of biogas slurry (BS) is crucial for sustainable development, yet its long-term ecological impacts remain unclear. Through a multi-year field trial in a sugarcane system, this study examined the effects of BS application (0, 3, and 6 years) on the soil properties, bacterial communities, and functional genes for C, N, P, and S cycling. The results revealed distinct two-phase patterns of changes in soil properties, microbial communities, and functional genes. Short-term (3-year) application induced a “disturbance” phase, characterized by significant acidification (pH decreased by 17.91%), a surge in nitrate-N (increased by 757.27%), and a transient decline in bacterial richness. Long-term (6-year) application drove a “functional restructuring” phase, reversing acidification and significantly increasing soil organic matter (29.05%) and total nitrogen (TN) (20.81%). Bacterial richness recovered, and community composition distinctively restructured. Functional gene analysis revealed shifts in gene abundance that transitioned from high abundance in the short term to a new balance favoring processes like N fixation. Co-occurrence network analysis indicated that this functional shift was associated with core microbial modules (e.g., Firmicutes) and changes in soil pH and SOM. This study suggests that, although short-term application causes significant adjustments, sustained and appropriate BS application can ultimately enhance soil fertility and promote a functionally reorganized state by reshaping microbial interaction networks. It presents a microbial ecological basis for the safe and sustainable use of BS in circular agriculture. Full article

The objective of this study was to evaluate the impact of seasonal changes in the chemical and structural composition of giant miscanthus (Miscanthus × giganteus) biomass on the performance, kinetics, and efficiency of anaerobic digestion (AD), as well as on the overall energy and techno-economic balance of the conversion chain. The AD performance was assessed using batch biochemical methane potential (BMP) assays conducted for eight harvest dates (June–January). Comprehensive characterization included fundamental physicochemical properties of the biomass, lignocellulosic fraction composition, AD kinetics, and methane production yield. A statistically significant (p < 0.05) increase in structural fiber fractions was observed with advancing plant maturity, accompanied by a progressive decline in specific methane yield from 281 ± 32 mL CH₄/g VS in June to 170 ± 11–172 ± 13 mL CH₄/g VS in winter harvests. Despite a relatively stable theoretical biochemical methane potential (TBMP) ranging from 425 to 443 mL CH₄/g VS, the conversion efficiency (BMP/TBMP) decreased from approximately 66% to below 40%, indicating increasing structural and kinetic limitations to substrate biodegradability. Kinetic parameters deteriorated systematically in late harvests, as reflected by a reduction in the first-order rate constant k_CH₄ from 0.115 to approximately 0.072 1/d and an extension of the lag phase λ from 2.19 to over 4 days. Regression analysis revealed strong negative correlations between lignocellulosic complex content and both BMP and k_CH₄, whereas the C/N ratio exhibited a positive association with process performance under the experimental conditions applied. The highest methane production per hectare (3904 ± 720 m³CH₄/ha) and the most favorable economic outcome (1979 ± 465 EUR/ha) were achieved for the September harvest. The results demonstrate that harvest timing constitutes a critical optimization parameter in lignocellulosic biogas systems, governing not only methane yield and process kinetics but also the overall energy output and economic viability of the bioenergy production chain. Full article

The shipping sector is responsible for a considerable share of global CO₂ emissions and is under pressure to reduce emissions and adopt carbon-neutral fuels. Among the proposed alternatives, methanol produced from green hydrogen and biogenic CO₂ represents a promising option. However, the feasibility of its production is significantly influenced by the composition and variability of the bio-CO₂ feedstock, which can negatively impact the complete value chain. To address these challenges, sampling campaigns were carried out at actual bio-CO₂-emitting sites, namely biogas and biomass combustion facilities, to characterize the impurity profiles and determine the appropriate conditioning requirements. A novel membrane gas absorption system with a Diethanolamine solution was deployed directly in the field to capture, as well as purify to a certain extent, the CO₂ stream. The system demonstrated high efficiency in removing most impurities, achieving high CO₂ capture rates and impurity reduction close to 90%. However, residual chlorine species were detected in the CO₂ streams from biogas plants, suggesting the need for additional conditioning to meet the purity specifications required for methanol synthesis. Given that the feedstock composition and upstream process conditions could significantly affect the final output and present considerable variations, the implementation of additional cleaning measures is recommended before synthesis. Full article

Pressure swing adsorption (PSA) is a viable method for separating hydrogen from gas mixtures, an important aspect of long-term hydrogen storage in depleted gas fields. This study explores optimizing a 12-step PSA process for recovering high-purity hydrogen from varying compositions of hydrogen–methane mixtures, simulating the conditions likely encountered during hydrogen storage and recovery. Step-time optimization was performed on four different hydrogen–methane mixtures using the toPSAil simulation package—an open-source dynamic PSA simulator developed by researchers at the Georgia Institute of Technology—integrated with a particle swarm optimization (PSO) algorithm. The goal was to develop an optimization framework that can reliably identify PSA step times for different operating scenarios and satisfy specified purity and recovery constraints under fluctuating wellhead feed conditions. The optimization converged within 25–30 iterations, even in high-contaminant, low-pressure scenarios, where PSA performance is traditionally weak. The product purity in the optimized cycles was above 99.1% with more than 80% recovery for all cases, while fuel cell quality (99.7%) hydrogen was achieved in two out of the four scenarios. The purge-to-feed ratio of the best-performing cycles was between 0.07 and 0.32. These findings show the potential of the proposed approach in overcoming the difficulty of designing PSA cycles for non-constant gas compositions and achieving a hydrogen purification process suitable for variable feed conditions. The workflow generates a large synthetic dataset that can support surrogate or hybrid modeling. The results can help advance research in other gas separation areas with non-constant conditions, like flue gas or biogas purification. Full article

Wastewater treatment plants increasingly rely on anaerobic digestion and biogas utilization to reduce operational costs, enhance energy self-sufficiency, and support circular-economy objectives. This study provides a comprehensive, year-round assessment of sludge production, sludge characteristics relevant to digestion, biogas generation, and energy performance at a municipal wastewater treatment plant. The plant generated on average 68.0 m³/d of thickened primary sludge and 24.0 m³/d of excessive sludge (total 92 m³/d), with low daily variability throughout the year. Biogas production remained highly stable, with an annual average of approximately 1300 m³/d and limited daily variation. Although monthly averages ranged from 1004 to 1728 m³/d, within-month variability was low to moderate, indicating that digestion processes responded consistently to changes in sludge quantity and composition. The weak correlation between sludge volume and biogas output (r = 0.29) showed that, besides sludge quantity, factors such as organic content and digester operating conditions also influence biogas yield. Energy performance indicators demonstrated strong self-sufficiency potential: the facility produced 1,095,047 kWh of electricity, covering 56.72% of its annual demand. The high coefficient of determination for self-sufficiency (R² = 0.871) confirmed a strong linear relationship between biogas-derived energy production and reduced grid dependence. Operational correlations further highlighted system coherence, with cogenerator and boiler usage strongly inversely related (r = −0.85) and biogas production positively associated with heat output (r = 0.66). Overall, the results demonstrate a stable and efficient sludge-to-energy system and provide a detailed dataset supporting future optimization of anaerobic digestion processes. Full article

In this work, an A-site deficient perovskite, (La_0.3Sr_0.6Ce_0.1)_0.9Co_0.1Ti_0.9O_3−δ (LSCCoT) was applied as an additional catalytic layer on Ni–YSZ anode for biogas-fuelled SOFC. Under reducing conditions, the formation of well-dispersed, socketed Co nanoparticles was observed due to the cobalt exsolution from the perovskite lattice. The structural and microstructural characterization confirmed phase stability of the perovskite after high-temperature reduction in hydrogen and the presence of exsolved nanoparticles on the grains’ surface. Electrical conductivity measurements showed thermally activated semiconducting behavior in air (E_a = 0.582 ± 0.121 eV) and a strongly enhanced conductivity with weak temperature dependence in hydrogen (E_a = 0.057 ± 0.001 eV). Single-cell tests performed under a CH₄/CO₂ (60/40 vol%) biogas mixture revealed a 30% increase in maximum power density at 800 °C compared to the reference cell. During 100 h of operation, the modified cell exhibited reduced performance degradation, improved internal reforming activity, and a more stable outlet gas composition. Full article

Biogas slurry is rich in nitrogen, phosphorus and bioactive substances, making it an effective material for restoring degraded grasslands. Against this background, we conducted a field experiment in Zhenglan Banner, Xilingol League, Inner Mongolia Autonomous Region, China, from 2024 to 2025, to study the short-term effects of biogas slurry fertilizer on vegetation characteristics and above- and belowground plant traits. The experiment comprised three treatments: a water control (CK), 50% diluted biogas slurry (BS_50%), and full-strength biogas slurry (BS_100%). All treatments were applied at a rate of 300 m³·ha⁻¹, with CK receiving an equivalent volume of water. The biogas slurry contained 0.11% nitrogen (N), 0.07% phosphorus (P₂O₅), and 0.09% potassium (K₂O). Results showed that, compared with the control, biogas slurry application increased plant height, coverage, and biomass by 8.04–54.00%, 5.48–17.76%, and 18.40–96.01% in the first year, respectively. Plant crude protein and crude fat also increased by 7.33–31.17% and 21.54–30.00%. In the second year, the increases were 26.41–50.22%, 6.16–20.55%, and 13.91–52.42% for plant height, coverage, and biomass and 4.46–28.27% and 14.24–19.89% for crude protein and crude fat, respectively. The carbon, nitrogen and isotope indices of leaves and roots also increased simultaneously. Biogas slurry application altered plant community composition, BS_50% transiently increased plant family richness, BS_100% exerted persistent inhibitory effects, and species diversity across all fertilization treatments showed a recovery trend in the second year. Principal component analysis and redundancy analysis showed that treatment groups were clearly separated in 2024 but overlapped substantially in 2025. Root δ¹³C and root δ¹⁵N were key indicators distinguishing vegetation community characteristics. The results of this study confirmed that the application of biogas slurry fertilizer could actively improve the vegetation recovery of degraded grasslands. It provided reference support for the resource utilization of biogas slurry fertilizer and the sustainable management of grassland ecosystems. Full article

This study evaluated the influence of four thermal pretreatment techniques—autoclaving, hot-air oven treatment, hot-water immersion, and microwave irradiation—on Parthenium hysterophorus biomass to improve its biodegradability and biogas generation potential under batch anaerobic digestion. Among the investigated methods, hot-air oven pretreatment at 110 °C for 90 min exhibited the most significant enhancement in biomass solubilization, as indicated by a 51.5% rise in soluble chemical oxygen demand (sCOD) and an increase in volatile fatty acids (VFAs) compared with the untreated control. These compositional improvements facilitated faster hydrolysis and led to a 25.73% higher cumulative methane yield in biochemical methane potential (BMP) assays. Structural analysis revealed pronounced alterations in the lignocellulosic matrix, with reductions in hemicellulose and partial delignification improving substrate accessibility. Complementary characterisation using field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR) confirmed the disruption of crystalline cellulose regions and modification of functional groups, supporting the observed biochemical improvements. Collectively, the results demonstrate that hot-air oven pretreatment is a practical and energy-efficient approach for enhancing the digestibility of P. hysterophorus biomass, promoting its utilisation as a sustainable feedstock for renewable biogas production and environmental management of this invasive weed. Full article

Maize silage can play a key role in policies aimed at stabilising local energy systems, as it constitutes a critical renewable feedstock for European biogas plants. By providing a dense and predictable source of chemical energy, it supports balance and reliability in the agricultural energy sector. To convert this potential into stable energy production, operators require kinetic models that translate routine silage quality indicators into concrete guidance for digester operation and control. Therefore, the aim of this article was to evaluate the batch kinetics of anaerobic digestion (AD) of maize silage and to select an adequate model for describing biochemical methane potential (BMP) profiles and associated energy recovery in the context of start-up, organic loading rate (OLR), hydraulic retention time (HRT) and feedstock preparation. Ten batches of silage (A–J) were examined, covering a realistic range of pH, electrical conductivity (EC), dry and volatile solids, ash, protein–fat–fibre fractions, fibre composition (NDF, ADF and ADL), derived fractions (hemicellulose, cellulose, and residual organic matter (OM)), C/N ratio and macro-/micronutrient profiles, including trace elements relevant to methanogenesis (Ni, Co, Mo, and Se). BMP tests were carried out in batch mode, and the resulting curves were fitted using the modified Gompertz and a first-order kinetic model. Methane yields of approx. 100–120 m³ CH₄/Mg fresh matter (FM) and 336–402 m³ CH₄/Mg volatile solids (VS), with CH₄ contents of 52–57% v/v, were typical for energy-grade maize silage. Kinetic and energetic behaviours were governed mainly by residual OM and hemicellulose (shortening the lag phase and increasing the maximum methane production rate), the ADL/cellulose ratio (controlling the slower hydrolytic tail), EC and Na/Cl/S (extending the lag phase), and C/N together with Ni/Co/Mo/Se (stabilising methanogenesis). The modified Gompertz model reproduced BMP curves with a pronounced lag phase and asymmetry more accurately (lower error and better information criterion values), and its parameters directly support start-up design, OLR ramp-up and energetic performance optimisation in bioenergy reactors. The novelty of this work lies in combining batch BMP tests, comparative kinetic modelling and detailed silage characterisation to establish quantitative links between kinetic parameters and routine maize silage quality indicators that are directly relevant for biogas plant operation and renewable energy production. Full article

This study investigates the preparation of a composite material by immobilizing Bacillus subtilis on biochar derived from chicken manure biogas residue for the removal of Cr(VI) from wastewater. The results demonstrated that the composite material (Bacillus subtilis immobilized biochar, BIB) achieved a maximum Cr(VI) removal efficiency of 94.1% in a 100 mg/L Cr(VI) solution within 4 h. The chicken manure-derived biochar not only served as an effective carrier for Bacillus subtilis but also enhanced the Cr(VI) removal efficiency through a synergistic effect with the microorganism. Functional groups such as phosphorus, carboxyl, and hydroxyl groups on the biochar surface played a key role in the sorption of Cr(VI). Bacillus subtilis primarily reduced Cr(VI) to Cr(III) by secreting cellular reductases. The combined action of biochar and Bacillus subtilis increased the Cr(VI) removal rate by 13.71% compared to biochar alone. This study presents a promising approach for Cr(VI) remediation in contaminated water and lays a theoretical foundation for the development of composite materials for Cr(VI) reduction. Full article

This study investigates the sequential integration of hydrothermal liquefaction (HTL) and anaerobic digestion (AD) as a strategy for resource recovery from municipal wastewater (MW) and semiconductor packaging wastewater (SPW) sludges. The primary objective is to determine the influence of HTL pretreatment on conversion efficiencies, water quality metrics, and subsequent anaerobic biodegradability. Specifically, the research focuses on biogas generation, COD removal, and the potential to promote circular resource utilization. HTL was conducted under controlled temperature (150–374 °C) and pressure (10–25 MPa) conditions, followed by batch AD at 41 °C using hydrogen- and methane-producing inocula at various ratios, specifically 20%, 50%, and 80%. Key variables, including total solids (TS), suspended solids (SS), chemical oxygen demand (COD), pH, and electrical conductivity (EC), were monitored to assess degradation efficiency and resource recovery. Additionally, chemical modifications in HTL-processed sludge were characterized using Fourier Transform Infrared Spectroscopy (FTIR). Results indicate that MW sludge achieved significant reductions in TS (65.3%) and enhanced biogas production of 156.7 mL/g VS at 80% inoculum. These figures reflect high biodegradability and compatibility with AD. In contrast, SPW sludge demonstrated limited COD removal (26.6–85%) and lower biogas yields of 154.0 mL/g VS. These results are likely due to elevated salinity and compositional complexity. These findings suggest that while HTL pretreatment significantly improves MW sludge utilization, SPW sludge may require additional or alternative treatment strategies. Overall, this study clarifies key factors influencing the performance of integrated HTL-AD systems across distinct sludge types and lays a foundation for the further development of sustainable sludge management processes. Full article

This study evaluated the feasibility of using effluent from the anodic chamber of a microbial fuel cell (MFC), powered by real fruit and vegetable wastewater, as a cultivation medium for Tetraselmis subcordiformis, a microalga capable of bio-photolytic hydrogen production. In three experimental variants, different organic loading rates were applied in the anodic chamber, resulting in significant differences in effluent quality and its suitability as a culture medium. In contrast to the dominant MFC configurations, in which microalgae act as cathodic biocatalysts, the microbial fuel cell in this study was used as a source of the inevitable anode effluent, which was subsequently valorized as a cultivation medium for the marine microalga T. subcordiformis to support biomass and hydrogen production. In variants with moderate COD concentration and low lipid content, the highest biomass concentrations, ranging from 941 ± 104 mg VS/L to 1020 ± 108 mg VS/L, were obtained, along with the highest nitrogen assimilation efficiency (48.7–49.1%) and phosphorus assimilation efficiency (62.3–63.1%). The variant in which the culture medium contained the highest concentrations of COD, TSS, and lipids showed a substantial limitation of biomass growth to 745 ± 75 mg VS/L and lower nutrient removal efficiency (total nitrogen—42.3 ± 4.7%, total phosphorus—55.0 ± 5.0%). The obtained biomass was then used for H₂ production in a mineral photobiolytic medium. The highest total hydrogen production reached 184.7 ± 25.0 mL, while the specific hydrogen yield reached 193.7 ± 32.6 mL/g VS. Increased concentration of organic matter in the medium reduced total hydrogen production to 112.0 ± 14.8 mL, mainly due to lower biomass concentration, although the specific hydrogen yield remained high (153.4 ± 25.8 mL/g VS). The biogas composition was stable (H₂ 58.0–58.7%, CO₂ 35.3–35.9%, O₂ 6.0–6.2%). Full article

Filter cake (or cachaza), a residue generated in the artisanal production of panela, represents an under-explored source of renewable energy in the Ecuadorian Amazon. Valorizing filter cake could reduce the use of solid biomass and emissions associated with traditional combustion. Our objective was to determine the energy potential of the biogas obtained and its contribution to the sustainability of the panela (unrefined cane sugar) production system. A sequential procedure was applied that included the physicochemical characterization of filter cake, feed flow modeling, and stoichiometric simulation under mesophilic conditions. The anaerobic digestion of filter cake with the optimal Composition 6 generated up to 1736.40 m³·day⁻¹ of biogas with 40.7% methane and a calorific value of 14,350 kJ·m⁻³. This was enough to replace 1.24 t·day⁻¹ of wood or 2.38 t·day⁻¹ of bagasse in the production system. This represents an annual saving of 631.08 t of solid biomass, equivalent to conserving 3.63 ha·year⁻¹ of the Amazon rainforest. The Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts (TRACI) analysis showed impacts on climate change (17.40 kg CO₂ eq/m³) and acidification (0.00516 kg SO₂ eq/m³), attributable to unburned methane and residual H₂S. Meanwhile, the social assessment using the Occupational Health and Safety Potential (OHSP) indicator showed high risks in terms of handling filter cake and cleaning the digestate. Full article

Microalgae and cyanobacteria represent promising, sustainable resources for agricultural applications, particularly as biofertilisers, biostimulants, and biological plant protection agents. Their biomass can improve nutrient use efficiency, support plant growth and yield, and enhance soil structure and microbial activity, while cyanobacteria additionally contribute through biological nitrogen fixation, reducing reliance on synthetic fertilisers. The integration of microalgal cultivation with closed-loop systems, such as wastewater treatment plants or biogas facilities, enables nutrient recovery, production of value-added biomass, and mitigation of greenhouse gas emissions. This review synthesises current knowledge on the biochemical composition, functional properties, and mechanisms of action of microalgal and cyanobacterial biomass in relation to these established agricultural applications. In addition, prevailing research trends, selected technological and organisational constraints, and implementation challenges are discussed. Particular attention is given to emerging application contexts, including bioregenerative life support systems (BLSS) for space agriculture, where microalgae and cyanobacteria can contribute to oxygen production, nutrient recycling, and edible biomass generation. Species such as Chlorella vulgaris, Arthrospira platensis, and Scenedesmus obliquus demonstrate tolerance to microgravity, radiation, and limited light conditions, supporting their potential use in closed, self-sufficient cultivation systems. Although numerous reviews have addressed individual agricultural applications of microalgae and cyanobacteria, a more integrative perspective that connects biological functionality with broader technological, regulatory, and implementation contexts remains valuable. The present review contributes to this perspective by consolidating established agronomic uses and extending the discussion toward selected emerging applications, thereby providing a structured framework for future research and development in sustainable terrestrial and extraterrestrial agriculture. Full article