Search Results (1,817)

With the growing use of crossbred cattle in Brazilian feedlots and increasing pressure to reduce antibiotic use as growth promoters, this study examines the impact of three feed additives—monensin (MON), monensin with Lithothamnium calcareum (LCM), and a blend of essential oils (BEO)—on the performance of Nellore (NEL) and crossbred (CROSS) cattle. A total of 90 Nellore and 90 crossbred bulls were assigned to a completely randomized block design with a 2 × 3 factorial design for 112 days, and all received the same diet with varying additives. Their methane (CH₄) emissions were estimated. All data were analyzed using the emmeans package of R software (version 4.4.1). Crossbred cattle outperformed Nellore in average daily gain (ADG), hot carcass weight (HCW), and dry matter intake (DMI), though feed efficiency remained unaffected. Across additives, no significant differences were observed in ADG, HCW, or dressing percentage. However, LCM had a lower DMI than the BEO, while MON showed better feed efficiency than the BEO. A breed-by-additive interaction trend was noted for DMI as a percentage of body weight (DMI%BW), with Nellore bulls on LCM diets showing the lowest DMI%BW. Crossbreeds had greater net energy (NE) requirements for maintenance (NEm) and gain (NEg), and MON-fed animals had greater NEm and NEg than the BEO. Crossbred bulls had greater daily methane (CH₄) emissions than Nellore bulls. Animals on the BEO had greater daily CH₄ emissions and greater g CH₄/kg metabolic BW than LCM bulls. In conclusion, the addition of Lithothamnium calcareum to monensin did not enhance performance compared to monensin alone. Monensin outperformed the BEO in feed efficiency and nutrient utilization. Full article

The interactions among water molecules, coal beds, and gases during the process of coal bed methane mining are highly complex. The water and methane (CH₄)/carbon dioxide (CO₂) molecules compete for adsorption and undergo a series of reactions that affect gas diffusion. In this study, Monte Carlo and molecular dynamics methods were used to investigate the microscopic mechanism of CH₄/CO₂ competitive adsorption and diffusion during CO₂-enhanced coal bed methane mining (ECBM) under different moisture contents, and the geological storage potential of CO₂ was predicted. The results showed that when the CO₂ and water binding sites were independent of each other, the water molecules changed the electrostatic potential around the coal molecules, resulting in enhanced CO₂ adsorption performance, as verified by the surface electrostatic potential. When the water molecules formed a water molecule layer, the adsorption capacity of the secondary adsorption sites provided was larger than that of the surface of the coal molecules, so the CO₂ molecules were preferentially adsorbed on the secondary adsorption sites. However, the number of secondary adsorption sites available was not as large as that on the surface of the coal molecules. The interaction energies revealed that when the displacement effect of CH₄ in the process of CO₂-ECBM and the sequestration effect of CO₂ were considered comprehensively, the best CO₂ sequestration effect and a good CH₄ displacement effect were obtained at a 3% moisture content. The worst CO₂ sequestration effect was found at a 5% moisture content. After CO₂ injection, the main adsorption layer of CH₄ shifted from X = 5 and X = 9 to X = 8.7 and X = 12.5, respectively, and obvious detachment and diffusion occurred. The distribution of the molecular motion and diffusion coefficient revealed the considerable displacement and dispersion of the gas molecules. The distribution of the gas molecular velocity and diffusion coefficient indicated that a 3% moisture content was the ideal condition for CO₂ displacement of CH₄, and the CO₂ sequestration effect was good. Full article

Rapid industrialization and the indiscriminate use of fossil fuels have generated an impact that is affecting the climate worldwide. Among the substances that are causing climate change are several gases such as carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O) and sulphur hexafluoride (SF₆), among others. Particularly, carbon dioxide is one of the substances that has attracted the most attention from researchers, as it is responsible for more than three quarters of greenhouse gases. Because of this, many efforts have been directed towards the capture of CO₂, its separation, adsorption and transformation into products that are less harmful to the environment or that even have added value in the industry. For this purpose, the use of different types of macrocycles has been explored mainly in the last 5 years. This review seeks to present the advances that have occurred in recent years in the capture and transformation of CO₂ by different methods, to finally focus on the capture and transformation through macrocycle systems such as azacompounds, heterometallic macrocycles, calixpyrrols, modified cyclodextrins and metallic porphyrins, among others. Full article

The chemical-looping reforming (CLR) of methane for hydrogen production employs a solid oxygen carrier (OC) and combines endothermic and exothermic stages, allowing for potential autothermal operation. This study conducted a thermodynamic analysis using Gibbs free energy minimization and energy balances to assess the behavior of WO₃, MnWO₄, and NiWO₄ as OCs in the CLR process. The effects of CH₄:OC ratios and reactor temperatures on equilibrium composition and the energy performance were examined. The results demonstrated that elevated reduction temperatures promote OC conversion and the formation of more reduced solid products. Molar ratios above stoichiometric prevent carbon formation, whereas stoichiometric ratios result in higher H₂ yield, achieving 98% at 1000 °C. However, these conditions do not support autothermal operation, which requires CH₄:OC molar ratios above stoichiometric. Additionally, lower oxidation temperatures are preferred regardless of the OC, due to the lower heat needed to preheat the air, which has a greater effect on the net heat. For the reduction temperature, its effect depends on the type of OC analyzed. The maximum H₂ yield obtained under autothermal operation was 88% for the three OCs, at 875 °C for MnWO₄ and 775 °C for both WO₃ and NiWO₄. Full article

Methane, a greenhouse gas with 21 times the global warming potential of carbon dioxide, is increasingly subject to stringent emission regulations, driving the demand for high-performance methane sensors. This study proposes a novel IR spectroscopy technique based on a CuBDC-integrated microcantilever (CuBDC-microcantilever IR spectroscopy) for CH₄ sensing, offering exceptional sensitivity and selectivity. The metal-organic framework (MOF) CuBDC was synthesized on the microcantilever using a drop-and-dry method facilitated by an intense pulsed light technique. Characterization via scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy confirmed the successful formation of CuBDC on the microcantilever. The CuBDC-microcantilever IR spectroscopy demonstrated a significantly enhanced sensitivity, with a differential amplitude at the CH₄ characteristic peak approximately 13 times higher than that of a conventional Si microcantilever. Moreover, the limit of detection was determined to be as low as 14.05 ppm. The clear separation of the CH₄ characteristic peak from the water and acetone vapor peaks also emphasized the sensor’s high selectivity. These findings highlight the superior sensitivity and selectivity of the proposed sensor, positioning it as a promising platform for CH₄ detection in industrial and environmental applications. Full article

Small intestinal bacterial overgrowth (SIBO) is a disorder characterized by the excessive growth of bacteria in the small intestine. Bacterial overgrowth disrupts the bacterial balance and can lead to abdominal pain, weight loss, and gastrointestinal symptoms, including bloating, diarrhea, and malabsorption. SIBO is widespread in the population. There are two main methods for diagnosing SIBO: breath tests and bacterial culture. The most commonly used method is a breath test, which enables the division of SIBO into the following three types: hydrogen-dominant (H-SIBO), methane-dominant (CH₄-SIBO), and hydrogen/methane-dominant (H/CH₄-SIBO). This comprehensive review aims to present the current knowledge on the use of prebiotics, probiotics, and postbiotics in the context of SIBO. For this purpose, medical databases such as MEDLINE (PubMed) and Scopus were analyzed using specific keywords and their combinations. This review is based on research studies no older than 10 years old and those using only human models. In summary, clinical studies have shown that the efficacy of SIBO therapy can be increased by combining antibiotics with probiotics, especially in vulnerable patients such as children and pregnant women. The further development of diagnostic methods, such as point of care testing (POCT) and portable devices, and a better understanding of the mechanisms of biotics action are needed to treat SIBO more effectively and improve the quality of life of patients. Full article

This study aims to explore anaerobic co-digestion (AcoD) of cassava (EUM) and poultry (FP) effluents using one inoculum/substrate ratio (30%) and three EUM vs. FP substrate composition ratios (25:75, 50:50, and 75:25). The AcoD process was therefore designed for 20 L batch digesters, under mesophilic conditions, with less than 5% total solids for 66 days. The results showed that EUMs were highly resistant to degradation, while FPs were the most easily degradable. Kinetic analysis indicated specific organic matter (MO) reduction rates of 0.28% per day for EUM and 0.76% per day for FP. EUM alone produced 45.47 mL/g MO, while the 50:50 substrate produced 1184.60 mL/g MOV. The main factors contributing to EUM inefficiency were the inability to tame acidic conditions and the accumulation of volatile fatty acids. AcoD produced 23 to 50 times more methane than EUM alone, 2 to 5 times more than FP alone, and 2 to 4 times more than inoculum. As a result, the AcoD of both types of waste had a qualitative and quantitative effect on biogas production. CH₄ content increased from around 2 to 75%, depending on the amount of organic nitrogen added. The addition of nitrogen by AcoD, even under mesophilic conditions, improves the kinetics and quality of anaerobic digestion of low-nitrogen substrates. Its impact on thermophilic and psychrophilic conditions needs to be verified. Full article

The hydrodeoxygenation (HDO) of biomass pyrolysis oil (BPO) was evaluated in the presence of two commercial alumina-supported transition metal catalysts, NiMo/alumina-1 (NM1) and NiMo/alumina-2 (NM2). The study explored two characteristic aspects: how HDO reaction conditions affected the oxygen content, density, and boiling point distribution of BPO with varying temperature and HDO reaction time, and the roles of catalysts. Characterizations of HDO-treated oils included elemental analysis, GC-MS, SIMDIS, ¹³C NMR, and ¹H NMR, and characterizations of catalysts included NH₃-TPD, XRF, and TPO-MS analysis. The results show that both NM1 and NM2 catalysts removed oxygenated compounds effectively, which led to decreases in density and shifts toward higher boiling point distributions of BPO. Compared to the NM1 catalyst, NM2 had a higher acidity and enhanced HDO activity. The best HDO reaction performance was achieved in the presence of the NM2 catalyst at 300 °C. Furthermore, HDO reactions showed a significant amount of CO₂, CH₄, C₂H₆, and C₃H₈, which suggests that HDO reactions proceeded via a series of reactions of decarboxylation, water–gas shift, and methanation. In addition, hydrocarbon fraction tests suggested a favorable potential for the blending of HDO-treated biomass pyrolysis oil (HDO-BPO) with petroleum-derived fractions. Full article

Methane (CH₄), the second-largest greenhouse gas contributing to global warming, has a high warming potential despite its short atmospheric lifespan. Inner Mongolia, due to its high carbon and energy consumption industries, faces significant methane emission challenges. This study uses TROPOMI satellite data (February 2019 to December 2022) to analyze the long-term trends and spatial distribution of methane in Inner Mongolia. The results indicate significant spatial heterogeneity in the methane concentration distribution in Inner Mongolia, China. Higher methane concentrations are observed in the southeastern regions, whereas the central regions exhibit relatively lower concentrations. Temporally, the methane concentrations show an increasing trend with seasonal peaks from late August to early September. Using multiple stepwise regression and geographically weighted regression (GWR) methods, the study identifies the key factors influencing methane concentrations. Increased precipitation and soil temperature, along with intensified human activity, contribute to higher methane levels, while rising surface temperatures and increased vegetation suppress methane concentrations. The GWR model provides a better fit compared to the traditional methods, especially in regions with higher methane levels. This research offers insights for developing strategies to mitigate methane emissions and supports China’s emission control targets. Full article

Dairy manure is an important nitrogen (N) source for crops, but its role in greenhouse gas (GHG) emissions and farm sustainability is not fully understood. We evaluated the effects of application of two dairy manure sources (bedded pack heifer, BP, and separated dairy solids, SDS) on corn silage yield and GHG emissions (carbon dioxide, CO₂; methane, CH₄; nitrous oxide, N₂O) compared to a urea-fertilizer-only control (80 kg N ha⁻¹ yr⁻¹). The BP and SDS were applied at 18.4 and 19.4 Mg dry matter ha⁻¹ in fall 2020 in the final year of ryegrass production. No-till corn was planted from 2021 to 2023, and GHG emissions were measured each season (from May to November). The results showed significantly greater CO₂-C emissions for BP in 2021 and no differences in 2022 or 2023. A small N₂O-N emission increase for BP occurred in the spring after application; however, seasonal fluxes were low or negative. Mean CH₄-C emissions ranged from 2 to 7 kg ha⁻¹ yr⁻¹ with no treatment differences. Lack of soil aeration appeared to be an important factor affecting seasonal N₂O-N and CH₄-C emissions. The results suggest that GHG models should account for field-level nutrient management factors in addition to soil aeration status. Full article

This study presents a comprehensive investigation of Methane (CH₄) emissions in the wetlands of South Sudan, employing an integrated approach that combines TROPOMI satellite data, river altimetry, and hydrological model outputs. TROPOMI data show a strong increase in CH₄ concentrations over the Sudd wetlands from 2018 to 2022. We quantify CH₄ emissions using these data. We find a twofold emission increase from 2018 to 2019 (9.2 ± 2.4 Tg yr⁻¹) to 2020 to 2022 (16.3 ± 3.3 Tg yr⁻¹). River altimetry data analysis elucidates the interconnected dynamics of river systems and CH₄ emissions. We identify correlations and temporal alignments across South Sudan wetlands catchments. Our findings indicate a clear signature of ENSO driving the wetland dynamics and CH₄ emissions in the Sudd by altering precipitation patterns, hydrology, and temperature, leading to variations in anaerobic conditions conducive to CH₄ production. Significant correlations are found between CH₄ emissions and PCR-GLOBWB-simulated soil moisture dynamics, groundwater recharge, and surface water parameters within specific catchments, underscoring the importance of these parameters on the catchment scale. Lagged correlations were found between hydrological parameters and CH₄ emissions, particularly with PCR-GLOBWB-simulated capillary rise. These correlations shed light on the temporal dynamics of this poorly studied and quantified source of CH₄. Our findings contribute to the current knowledge of wetland CH₄ emissions and highlight the urgency of addressing the complex interplay between hydrology and carbon dynamics in these ecosystems that play a critical role in the global CH₄ budget. Full article

In Italy, the number of farmed dairy buffaloes rose up to approximately 436,000 heads in 2023 (+22% in the last 15 years), a fourfold increase compared to the 1980s, due to the growing market interest in mozzarella cheese. The increased demand for mozzarella cheese, in turn, requires higher production, which can result in increased methane emission from the sector. Therefore, it is necessary to establish mitigation and selection schemes for low-emission strategies. The current study aimed to highlight sources of variation in methane emission from lactating Italian Mediterranean buffaloes measured using a laser methane detector in order to identify practical and methodological aspects to consider when designing experiments focused on methane emission evaluation. Methane (CH₄), exhaled from 60 cows, was recorded twice a day during milking, over two weeks per month for at least three months throughout a whole lactation cycle. The animal (individual), days in milk, parity, month, operator, milking entry order, and milking session effects were significant for methane emission (p < 0.0001). Our results showed that laser methane detector may be used as a rapid tool for methane emission studies and highlighted which factors can account for individual measures. This instrument is easy to use, fast, versatile, and not too expensive. These characteristics make it suitable for large-scale herd screening and monitoring. Full article

The oxidative dehydrogenation of propane with CO₂ (CO₂-ODP) was investigated over different metal oxides M_xO_y (M: Ca, Sn, Cr, Ga) supported on a SiO₂ surface. Catalysts were characterized employing nitrogen adsorption/desorption, X-ray diffraction (XRD), CO₂ temperature programmed desorption (CO₂-TPD) and pyridine adsorption/desorption experiments in order to identify their physicochemical properties and correlate them with their activity and selectivity for the CO₂-ODP reaction. The effect of operating reaction conditions on catalytic performance was also examined, aiming to improve the propylene yield and suppress side reactions. Surface acidity and basicity were found to be affected by the nature of M_xO_y, which in turn affected the conversion of propane to propylene, which was in all cases higher compared to that of bare SiO₂. Propane conversion, reaction rate and selectivities towards propylene and carbon monoxide were maximized for the Ga- and Cr-containing catalysts characterized by moderate surface basicity, which were also able to limit the undesired reactions leading to ethylene and methane byproducts. High surface acidity was found to be beneficial for the CO₂-ODP reaction, which, however, should not be excessive to ensure high catalytic activity. The silica-supported Ga₂O₃ catalyst exhibited sufficient stability with time and better than that of the most active Cr₂O₃-SiO₂ catalyst. Decreasing the weight gas hourly space velocity resulted in a significant improvement in both propane conversion and propylene yield as well as a suppression of undesired product formation. Increasing CO₂ concentration in the feed did not practically affect propane conversion, while led to a decrease in propylene yield. The ratio of propylene to ethylene selectivity was optimized for CO₂:C₃H₈ = 5:1 and space velocity of 6000 mL g⁻¹ h⁻¹, most possibly due to facilitation of the C–H bond cleavage against that of the C–C bond. Results of the present study provided evidence that the efficient conversion of propane to propylene is feasible over silica-based composite metal oxides, provided that catalyst characteristics have been optimized and reaction conditions have been properly selected. Full article

This study examines CH₄ and N₂O fluxes during the dry season in two distinct areas of the Pantanal: Barranco Alto Farm (BAF), dominated by grasslands, and Passo da Lontra (PL), a forested region. As climate change increases the occurrence of droughts, understanding greenhouse gas (GHG) fluxes in tropical wetlands during dry periods is crucial. Using static chambers, CH₄ and N₂O emissions were measured from soils and tree stems in both regions, with additional measurements from grass in BAF. Contrary to expectations, PL—characterized by clayey soils—had sandy mud samples that retained less water, promoting oxic conditions and methane uptake, making it a CH₄ sink. Meanwhile, BAF’s sandy, well-drained soils exhibited minimal CH₄ fluxes, with negligible methane uptake or emissions. N₂O fluxes were generally higher in BAF, particularly from tree stems, indicating significant interactions between soil type, moisture, and vegetation. These findings highlight the pivotal roles of soil texture and aeration in GHG emissions, suggesting that well-drained, sandy soils in tropical wetlands may not always enhance methane oxidation. This underscores the importance of continuous GHG monitoring in the Pantanal to refine climate change mitigation strategies. Full article

Methane (CH₄) emissions from urban sewer systems represent a significant contributor to greenhouse gases, driven by anaerobic decomposition processes. This review elucidates the mechanisms underlying CH₄ production in sewers, which are influenced by environmental factors such as the COD/SO₄²⁻ ratio, temperature, dissolved oxygen, pH, flow rate, and hydraulic retention time. We critically evaluated the effectiveness of empirical, mechanistic, and machine learning (ML) models in predicting CH₄ emissions, highlighting the limitations of each. This review further examines control strategies, including oxygen injection, iron salt dosing, and nitrate application, emphasizing the importance of balancing CH₄ reduction with the operational efficiency of wastewater treatment plants (WWTPs). An integrated approach combining mechanistic and data-driven models is advocated to enhance prediction accuracy and optimize CH₄ management across urban sewer systems. Full article