Search Results (270)

The biogas dry reforming reaction offers a promising route for syngas production while simultaneously mitigating greenhouse gas emissions. Membrane reactors have proven to be an excellent option for hydrogen production and separation in a single unit, where conversion and yield can be enhanced over conventional processes. In this study, a Pd/YSZ membrane integrated with a Ru/CeO₂ catalyst was evaluated for biogas reaction under varying operating conditions. The selective removal of hydrogen through the palladium membrane improved reactant conversion and suppressed side reactions such as methanation and the reverse water–gas shift. Experiments were performed at temperatures ranging from 500 to 600 °C, pressures of 1–6 bar, and a gas hourly space velocity (GHSV) of 800 h⁻¹. Maximum conversions of CH₄ (43%) and CO₂ (46.7%) were achieved at 600 °C and 2 bar, while the maximum hydrogen recovery of 78% was reached at 6 bar. The membrane reactor outperformed a conventional reactor, offering up to 10% higher CH₄ conversion and improved hydrogen production and yield. Also, a comparative analysis between Ru/CeO₂ and Ni/Al₂O₃ catalysts revealed that while the Ni-based catalyst provided higher CH₄ conversion, it also promoted methane decomposition reaction and coke formation. In contrast, the Ru/CeO₂ catalyst exhibited excellent resistance to coke formation, attributable to ceria’s redox properties and oxygen storage capacity. The combined system of Ru/CeO₂ catalyst and Pd/YSZ membrane offers an effective and sustainable approach for hydrogen-rich syngas production from biogas, with improved performance and long-term stability. Full article

Depressurization combined with thermal stimulation based on injection-production well patterns is considered promising for gas hydrate development. Nevertheless, its direct application to Shenhu challenging hydrates may be problematic due to the presence of low reservoir permeability and permeable boundaries. The present study proposes to improve the development potential of Shenhu hydrate by reservoir reconstruction, including boundary sealing and reservoir fracturing, and numerically investigates the production performance. The results showed that water intrusion, hot loss, and gas leakage can be effectively addressed by boundary sealing. Nevertheless, it cannot enhance productivity as thermal decomposition gas accumulated around the injection well. Conversely, reservoir fracturing can significantly improve extraction efficiency as substantial amounts of hydrates dissociate along the fractures, and the gas can be well recovered through the fractures. However, reservoir fracturing was not conducive to water control and energy utilization as it induced more severe water flooding and gas leakage. Under the synergistic effect of the two, there was no methane leakage, and the gas production rate increased with increasing fracture conductivity, while the gas-to-water ratio and energy ratio presented the opposite trend. To obtain a favorable production performance, a fracture with a conductivity of 1–10 D·cm was recommended. Therefore, the combination of boundary sealing and reservoir fracturing makes it feasible for safe and efficient extraction of offshore challenging hydrate under the injection-production mode. Full article

The article deals with the creation of a calibration model of lactic acid content in an aqueous solution. The research concept included the preparation of a control tool for the process of modifying the properties of the food fraction for methane fermentation bacteria. The thesis was formulated that it is possible to prepare a systemic solution for real-time observation and monitoring of lactic acid secretion during the digestion of a hydrated mixture of food fractions. The scientific aim of the work was to develop and verify a calibration model of lactic acid content in an aqueous mixture with limited transparency for visible light waves. The research methodology was based on near-infrared spectroscopy with multivariate analysis. Stochastic modeling with noise reduction based on orthogonal decomposition was used. A calibration model was created using Gaussian processes (GP) to predict the lactic acid concentration in an aqueous solution or mixture using an NIR-Vis spectrophotometer. The design of the calibration model was based on absorbance spectra and computational data from selected wavelength ranges from 450 nm to 1900 nm. The measurement data in the form of spectra were limited from the initial wider range (400–2250 nm) to reduce interference. The generated calibration model achieved a mean error level not exceeding 2.47 g∙dm⁻³ of the identified lactic acid fraction. The coefficient of determination R² was 0.996. The effect of absorbing the emitter waves was achieved despite the limited transparency of the mixture. Full article

The photocatalytic reduction of CO₂ in aqueous media offers a sustainable route for solar-to-fuel conversion, yet remains challenged by CO₂’s thermodynamic stability and kinetic inertness, low solubility, and competitive hydrogen evolution. Here, we investigate the interplay between ionic liquids (ILs), photocatalyst supports, and additive composition in directing product selectivity among CO, CH₄, and H₂. Using imidazolium acetate as a benchmark, we demonstrate that ILs not only pre-activate CO₂ but can also undergo decomposition pathways under illumination, notably Kolbe-type reactions leading to methane formation from acetate rather than from CO₂. Comparative studies of Pd-decorated TiO₂ and g-C₃N₄ nanosheets reveal distinct behaviors driven by their interfacial interactions with the imidazolim-based ionic liquid: weak interaction with TiO₂ strongly promotes hydrogen evolution, whereas strong coupling with g-C₃N₄ synergizes with C₁C₄ImOAc to trigger acetate-derived Kolbe reactivity. The systematic evaluation of alternative salts confirms the determinant role of anion basicity and medium-pH-basic anions facilitate CO₂ activation, whereas weakly basic or non-coordinating anions favor water splitting. Overall, these results clarify the dual role of ionic liquids as both CO₂ activators and sacrificial agents, and highlight design principles for improving product selectivity and efficiency in aqueous CO₂ photoreduction systems. Full article

Livestock and poultry manure emits substantial amounts of ammonia and non-CO₂ greenhouse gases of nitrous oxide and methane, contributing simultaneously to climate forcing and air quality degradation. However, few studies have provided an integrated quantification of ammonia, nitrous oxide and methane emissions across multiple species and provinces in China. This study established a coupled provincial inventory for 2013–2023 and applied the Logarithmic Mean Divisia Index (LMDI) to identify socioeconomic drivers. Results show that NH₃ emissions declined slightly from ~4.1 Tg in 2013 to 3.95 Tg in 2023 (−3.7%), while N₂O increased from 2.1 to 2.3 Tg (+9.5%) and CH₄ rose from 3.1 to 4.2 Tg (+35%). Consequently, the aggregated global warming potential increased by ~24% (from ~1100 to ~1370 Tg CO₂-eq). Hogs were identified as the dominant contributor across gases. High-emission provinces contributed disproportionately, whereas metropolitan and western provinces reported marginal levels. LMDI decomposition revealed that affluence and technological intensification were the main drivers of growth, partially offset by production efficiency and labor decline. This study provides one of the first integrated multi-gas, multi-species, and region-specific assessments of livestock manure emissions in China, offering insights into targeted mitigation strategies that simultaneously support carbon neutrality and air quality improvement. Full article

The enteric methane (CH₄) emission from dairy cattle is a significant factor contributing to anthropogenic climate change and the energy loss of animals. The objective of this study was to evaluate the prediction accuracy of the existing CH₄ estimation models from dairy cattle, and to identify the most reliable model for quantifying CH₄ emission. A database was compiled from 135 treatment means obtained from 81 peer-reviewed literatures, which included data on dietary composition, energy intake, and enteric CH₄ emission from dairy cattle. Forty existing dairy cattle prediction models were evaluated using this dataset based on the root mean square prediction error (RMSPE), concordance correlation coefficient (CCC), the ratio of RMSPE to standard deviation (RSR), and error decomposition indicators (ECT, ER, and ED). Results indicated that the RSR of model 38 was the lowest (0.71) but there were large prediction errors. Considering all evaluation indicators, model 21, which included dry matter intake (DMI), demonstrated the most robust predictive performance (RSR = 0.83, RMSPE = 14.41%, ECT = 3.42%, ER = 0.74%, ED = 96.75%, CCC = 0.58). Therefore, it is recommended for estimating enteric CH₄ emissions from dairy cattle. Future research will need to further improve the accuracy and robustness of enteric CH₄ prediction models by establishing a more comprehensive large-scale database, and expand the applicability of the model in various dairy farming systems. Full article

This study presents a novel approach to intensifying the anaerobic digestion of sewage sludge through enzymatic pretreatment using hydrolytic enzymes—cellulase and lysozyme. It aims to determine how enzymatic activation affects the efficiency of methane fermentation, defined as the degree of organic matter decomposition and yield and composition of biogas. An experiment was carried out under mesophilic conditions over 20 days, analyzing the physicochemical properties of sludge, biogas production, methane content, and sanitary parameters. The addition of cellulase and lysozyme significantly enhanced process efficiency, increasing both the rate of organic matter degradation and biogas yield. The highest biogas production values (0.73 L·g⁻¹ d.m. for cellulase and 0.72 L·g⁻¹ d.m. for lysozyme) were obtained at a 4% (w/w) enzyme concentration, with a corresponding increase in the degree of organic matter decomposition to 78.7% and 80.0%, respectively. The produced biogas contained 58–61% methane, exceeding the values observed in the control sample, which indicates a positive effect of enzymatic activation on methane selectivity. Enhanced biogas production was attributed to improved hydrolysis of complex organic compounds, resulting in greater substrate bioavailability for methanogenic microorganisms. Moreover, methane fermentation led to the complete elimination of E. coli from all supernatants, confirming the hygienization potential of the process. The results of this study indicate that enzymatic pretreatment may serve as a viable strategy to improve both the energy efficiency and hygienic safety of anaerobic digestion processes, with relevance for future optimization and full-scale wastewater treatment applications. Full article

Thermo-catalytic decomposition (TCD) presents a promising pathway for producing hydrogen from natural gas without emitting CO₂. This process represents a form of fossil fuel decarbonization where the byproduct, rather than being a greenhouse gas, is a solid carbon material with potential for commercial value. This study examines the dynamic behavior of TCD, showing that carbon formed during the reaction first enhances and later dominates methane decomposition. Three types of carbon materials were employed as starting catalysts. Methane decomposition was continuously monitored using on-line Fourier transform infrared (FT-IR) spectroscopy. The concentration and nature of surface-active sites were determined using a two-step approach: oxygen chemisorption followed by elemental analysis through X-ray photoelectron spectroscopy (XPS). Changes in the morphology and nanostructure of the carbon catalysts, both before and after TCD, were examined using high-resolution transmission electron microscopy (HRTEM). Thermogravimetric analysis (TGA) was used to study the reactivity of the TCD deposits in relation to the initial catalysts. Partial oxidation altered the structural and surface chemistry of the initial carbon catalysts, resulting in activation energies of 69.7–136.7 kJ/mol for methane. The presence of C₂ and C₃ species doubled methane decomposition (12% → 24%). TCD carbon displayed higher reactivity than the nascent catalysts and sustained long-term activity. Full article

Catalytic methane decomposition (CMD) is an environmentally friendly method of hydrogen production that, unlike other conventional processes, such as steam methane reforming, partial oxidation of methane, and dry reforming of methane, can convert methane into hydrogen with a simultaneous generation of solid carbon without CO₂ emissions. This study mainly focused on the application of carbon-based catalysts derived from biomass and biowaste for the CMD process. For this purpose, eight catalysts were produced from three carbon materials (wood, sewage sludge, and digestate) through the subsequent processes of pyrolysis, leaching, and physical activation. The comparison of catalysts prepared from the slow pyrolysis of biowaste and wood indicated that carbon materials with a lower ash content achieved a higher initial methane conversion (wood char > digestate char > sewage sludge char). For feedstocks with a high initial ash content, such as digestate and sewage sludge chars, an improvement in the catalytic activity was observed after ash removal through the leaching process with HNO₃. In addition, physical activation through CO₂ fluxing led to an enhancement in the BET surface area of these catalysts, and consequently to a growth in methane conversion. The initial methane conversion was assessed for all chars under operating conditions of 900 °C, a gas hourly space velocity (GHSV) of 3 L/g/h, and a CH₄:N₂ ratio of 1:9, and it was 65.9, 59.1, and 42.6% v/v, respectively, for chars derived from wood, sewage sludge, and digestate; these values increased to almost 80% v/v when these chars were upgraded by chemical leaching and physical activation. Full article

Municipal solid waste (MSW) management is identified as a significant sustainability concern. Source segregation (SS) is the most effective method of managing MSW, and anaerobic digestion (AD) is the most efficient treatment method. The aim of this study was to analyze the impact of waste collection rules on the efficiency and performance of AD. The potential biomethane yields for SS-kitchen waste and SS-biowaste were calculated, determined in laboratory tests, and verified full-scale. The content of the organic fraction in SS-biowaste reached about 81 to 86%; however, regarding SS-kitchen waste, it reached almost 92%. The primary contaminants were plastics. The obtained biogas yield was slightly higher for SS-kitchen waste (136.2 m³/ton), compared to SS-biowaste (116.6 m³/ton). The pH values, acidity, and alkalinity indicated no risk of exploitation using both feedstocks. However, in the case of SS-kitchen waste, the acetic acid content was about 2.5 times higher than that of SS-biowaste. Furthermore, the acetic acid was noted in the outlet section (about 140–160 mg/kg), indicating no complete organic matter decomposition. Regarding SS-kitchen waste, the calculated methane yield reached 137.1 m³_CH4/ton and laboratory tests showed a methanogenic potential of 129.7 m³_CH4/ton, while at full-scale, it reached about 82.2 m³_CH4/ton. The research confirmed that the SS of biowaste positively impacts MSW management by improving waste composition and increasing recycling possibilities. AD is an effective biowaste treatment process, allowing energy recovery from waste. Full article

Nickel and nickel oxide are widely used as heterogeneous catalysts in various processes involving the hydrogenation or reduction of organic compounds, and also as excellent methanation catalysts in the hydrogenation of CO₂. As heterogeneous catalysis is a surface-dependent process, nickel compounds in the form of microparticles (MPs), and particularly nanoparticles (NPs), improve the catalytic activity of Ni-based catalysts due to their high specific surface area. Solvothermal synthesis, which has so far been neglected for the synthesis of Ni-based methanation catalysts, was used in this study to synthesize nickel and nickel oxide MPs and NPs with a narrow size distribution. Solvothermal synthesis allows for the control of both the chemical composition of the resulting Ni catalysts and their physical structure by simply changing the reaction conditions (solvent, temperature, or concentration of reactants). Only non-toxic substances were used for synthesis in this study, meaning that the whole synthesis process can be described as environmentally friendly. Solvothermally prepared Ni compounds were subsequently transformed into nickel oxide by means of high-temperature decomposition, and all of the prepared Ni-based compounds were tested as catalysts for CO₂ methanation. The best catalysts prepared in this study exhibited a CO₂ conversion rate of nearly 95% and a selectivity for methane close to 100%, which represent thermodynamic limits for this reaction at the used temperature. These results are commonly achieved with much more complex catalytic composites containing precious metals, while here we worked with pure nickel and its oxides, in the form of micro- or nanoparticles, only. Full article

Electrochemical reduction processes enable the CO to be converted into a useful chemical fuel. Our study employs density functional theory calculations to analyze the (110) facets of the transition metal carbide surfaces for CO capture, incorporating the Mars–van Krevelen (MvK) mechanism. All the possible adsorption sites on the surface, including carbon, metal, and bridge sites, were fully investigated. The findings indicate that the carbon site is more active relative to the other adsorption sites examined. The CO hydrogenation paths have been comprehensively investigated on all the surfaces, and the free energy diagrams have been constructed towards the product. The results conclude that the TiC is the most promising candidate for the formation of methane, exhibiting an onset potential of −0.44 V. The predicted onset potential for CrC, MoC, NbC, VC, WC, ZrC, and HfC are −0.86, −0.61, −0.61, −0.93, −0.87, −0.61, and −0.81 V, respectively. Our calculated results demonstrate that MvK is selectively relevant to methane synthesis. Additionally, we investigated the stability of these surfaces against decomposition and conversion to pure metals concerning thermodynamics and kinetics. It was found that these carbides could remain stable under ambient conditions. The exergonic adsorption of hydrogen on carbon sites, requiring smaller potential values for product formation, and stability against decomposition indicate that these surfaces are highly suitable for CO reduction reactions using the MvK mechanism. Full article

The integration of an MFC-powered Fenton (MFC-Fenton) system into the traditional anaerobic composting process can promote excess dewatered sludge (ES) decomposition. However, the antibiotic resistance gene (ARG) profiles in ES treated by MFC-Fenton systems remain poorly understood; in addition, the effect of adding 2-bromoethane sulfonate (BES, a methane inhibitor) during ES treatment using an MFC-Fenton system on ARG levels is largely unexplored. The present work focused on investigating the effects of BES and bioelectrochemical processes on ARG and MGE abundances and unraveling the ARG attenuation mechanism. According to our findings, adding BES promoted ARG reduction in ES in an MFC-Fenton system. The average ARG levels in the MFC-Fenton samples containing high BES contents (0.4 or 0.5 g BES/g VSS) markedly declined relative to those in samples containing lower BES levels. Moreover, macrolide transporter ATP-binding protein, macrolide-efflux protein, and macB levels markedly decreased as BES levels increased. BES supplementation and bioelectrochemical assistance were crucial for altering the ARG composition in the MFC-Fenton system. Changes in the microbial community composition had the greatest effect on the variation in ARG composition. Furthermore, the Actinobacteria and Firmicutes levels accounted for 52.8% of the overall ARG variation. Among MGEs, plasmids, insertion sequences, and integrons showed lower levels within the sludge metagenomes. Typically, sulI, sulII, tetG, and bla TEM levels were positively correlated with metal resistance genes (MRGs), and their levels markedly declined following the MFC-Fenton process. Thus, the collective evidence indicates that BES synergizes with bioelectrogenesis to reduce ARG abundance. Full article

It is critical to provide proper environmental conditions in poultry houses to maintain birds’ health, boost productivity, and improve the overall economic viability of the poultry industry. Among the myriad of environmental elements, indoor air quality has been a determining factor that directly affects poultry well-being. Elevated concentrations of harmful gases—in particular Carbon Dioxide ($C{O}_2$), Methane ($C{H}_4$), and Ammonia ($N{H}_3$)—decomposition products of poultry litter, feed wastage, and biological processes have draconian effects on bird health, feed efficiency, the growth rate, reproduction efficiency, and mortality rate. Despite their importance, traditional air quality monitoring systems are often operated manually, labor intensive, and cannot detect sudden environmental changes due to the lack of real-time sensing. To overcome these limitations, this paper presents an interdisciplinary approach combining cloud computing, Artificial Intelligence (AI), and Internet of Things (IoT) technologies to measure real-time poultry gas concentrations. Real-time sensor feeds are transmitted to a cloud-based platform, which stores, displays, and processes the data. Furthermore, a machine learning (ML) model was trained using historical sensory data to predict the next-day gas emission levels. A web-based platform has been developed to enable convenient user interaction and display the gas sensory readings on an interactive dashboard. Also, the developed system triggers automatic alerts when gas levels cross safe environmental thresholds. Experimental results of $C{O}_2$ concentrations showed a significant diurnal trend, peaking in the afternoon, followed by the evening, and reaching their lowest levels in the morning. In particular, $C{O}_2$ concentrations peaked at approximately 570 ppm during the afternoon, a value that was significantly elevated (p < 0.001) compared to those recorded in the evening (~560 ppm) and morning (~555 ppm). This finding indicates a distinct diurnal pattern in $C{O}_2$ accumulation, with peak concentrations occurring during the warmer afternoon hours. Full article

The lotus–fish co-culture (LFC) system leverages plant–fish symbiosis to optimize aqua-culture environments, enhancing both economic and ecological yields. However, the eco-logical mechanisms of microbial communities in LFC systems remain poorly understood, particularly regarding the functional roles of fungi, archaea, and viruses. This study compared microbiota (viruses, archaea, fungi) in water, sediment, and fish (crucian carp) gut of LFC and intensive pond culture (IPC) systems using integrated metagenomic and environmental analyses. Results demonstrated that LFC significantly reduced concentrations of total nitrogen, total phosphorus, and nitrite nitrogen and chemical oxygen demand in water, and organic matter and total nitrogen in sediment compared to IPC. Community diversity analysis, LefSe, and KEGG annotation revealed suppressed viral diversity in LFC, yet increased complexity and stability of intestinal virus communities compared to IPC. Archaeal and functional analyses revealed significantly enhanced ammonia oxidation and OM decomposition in LFC versus IPC, promoting methane metabolism equilibrium and sediment organic matter decomposition. Moreover, crucian carp intestines in LFC harbored abundant Methanobacteria, which contributed to maintaining a low hydrogen partial pressure, suppressing facultative anaerobes and reducing intestinal infection risk. The abundance of fungi in sediment and crucian carp intestine in LFC was significantly higher than that in IPC, showing higher ecological self-purification ability and sustainability potential in LFC. Collectively, LFC's optimized archaeal–fungal networks strengthened host immunity and environmental resilience, while viral community suppression reduced pathogen risks. These findings elucidate microbiome-driven mechanisms underlying LFC’s ecological advantages, providing a framework for designing sustainable aquaculture systems through microbial community modulation. Full article