Search Results (499)

To address the issues of high energy consumption, high carbon emissions, and the waste of associated energy (AE) in coal mine production, which severely hinder global sustainable development goals, this paper proposes a novel low-carbon economic collaborative optimal scheduling model for a coal mine integrated energy system (CMIES) oriented towards sustainable energy transitions. First, a refined utilization model for AE encompassing coal mine gas, ventilation air methane (VAM), and mine groundwater (GW) is constructed, and a tiered carbon emission trading mechanism (TCET) is introduced to constrain carbon emissions and promote ecological sustainability. Second, a concentrated solar power (CSP) plant is integrated to break the rigid “power determined by heat” constraint of a traditional combined heat and power (CHP) unit, thereby enhancing the system’s scheduling flexibility and renewable energy integration. Meanwhile, abandoned mines are retrofitted into solvent storage tanks to construct an integrated flexible carbon capture system (IFCCS), achieving sustainable reuse of mining wastelands. Finally, to tackle the multi-source, heterogeneous uncertainties on both the source and load sides, a hybrid risk assessment method combining information gap decision theory (IGDT) and conditional value at risk (CVaR) is proposed. Case study results demonstrate that, compared to traditional energy supply modes, the proposed model reduces carbon emissions and total costs in the mining area by 66.04% and 15.97%, respectively. This significantly improves resource utilization efficiency and ecological benefits, providing a highly viable pathway for the sustainable development and clean transition of coal mine operations. Furthermore, the proposed hybrid assessment method can effectively assist decision-makers in achieving a refined trade-off between operating costs and system robustness under varying risk preferences. Full article

The accumulation of intermediate products, particularly volatile fatty acids (VFAs) like propionic acid (HPr) or its dissociated form, can inhibit biogas production during anaerobic digestion (AD) at low concentrations. Knowledge about the response of microorganisms to VFA inhibition can help control the digesters. In this study, we aimed to determine how sodium propionate (NaPr) inhibits the AD of municipal sewage sludge by identifying shifts in the microbial community. Four 5 L reactors were operated in semi-continuous mode using sewage sludge and then loaded with different levels of NaPr. The reactors operated at 37 °C with two hydraulic retention times. The results show that there was no apparent inhibition of biogas production at NaPr loading up to 20.3 mmol·L⁻¹. However, moderate inhibition was observed at 81 mmol·L⁻¹, corresponding to an approximate 10% decrease in methane production, while a ≈40% decrease in methane production was observed at 135.3 mmol·L⁻¹. Sequencing analysis revealed that the community composition was dominated by Bacillota, Bacteroidota, Proteobacteria, Chloroflexi, and Cloacimonadota, with Halobacterota and Euryarchaeota as the main archaeal groups. PERMANOVA revealed incubation time as the primary driver of community structure, followed by NaPr concentration. Elevated NaPr levels resulted in a decline in Methanothrix and Methanobrevibacter and promoted distinct syntrophic propionate-oxidizing bacteria (SPOB). Full article

To address the limitations in the accuracy of existing methods for calculating greenhouse gas emission intensity from underground coal mining, this study develops a more precise model for estimating methane emissions. The model is grounded in the methane release mechanism of coal, and incorporates field-measured original gas content, residual gas content after extraction, and retained gas content following ventilation. The model defines the computational scope based on different mining methods (with and without coal pillars) and incorporates potential direct emission reduction measures applicable at various stages of the mining process. Case studies of both a high-gas mine and a low-gas mine reveal that, while the pillarless mining method increases total methane emissions, emission intensity is reduced. Furthermore, the study demonstrates that preventing the direct release of low-concentration methane from ventilation systems is critical for further emission reductions. Compared to existing methods, the proposed framework adopts a computational approach that reduces operational complexity while maintaining accuracy through the use of readily available field-measured data. These findings offer a scientific basis for formulating tailored emission reduction strategies in the coal mining sector. Full article

Livestock production is a major source of agricultural methane (CH₄) and nitrous oxide (N₂O), making the synergistic mitigation of these two gases essential for meeting climate targets. Based on the EDGAR emission database from 2000 to 2024, this study employs international comparisons, spatial analysis, and STIRPAT-based scenario projections to characterize emissions from China’s animal husbandry and explore pathways for synergistic mitigation. The results reveal that China’s livestock CH₄ emissions exhibited a trend of early-stage fluctuation followed by a late-stage rebound, while N₂O emissions fluctuated sharply. The two gases are strongly synergistic yet driven by distinct mechanisms. China accounts for the largest share of global emissions and exhibits a distinctive emission structure—with comparable contributions from enteric fermentation and rice paddies—setting it apart from both pasture-based and intensive developed countries. High-emission areas are becoming increasingly concentrated in northern production regions. Under the baseline scenario, CH₄ and N₂O emissions are projected to peak in 2032 and 2030, respectively; under an ultra-low-carbon scenario, both gases peak around 2029, at substantially lower levels. Achieving synergistic mitigation calls for a regionally differentiated framework that combines top-down governance with bottom-up participation from farmers, integrating enteric fermentation control with optimized manure management to support a low-carbon transition. Full article

Direct emission of low-concentration methane not only aggravates global warming but also causes serious energy waste. Catalytic combustion is considered an effective strategy for methane abatement because it enables methane oxidation at relatively low temperatures. In this work, a series of Mn–Ce–Cu/γ-Al₂O₃ catalysts with different nominal Mn/Ce ratios were prepared by the incipient wetness impregnation method and applied to low-concentration methane catalytic combustion. The results showed that Mn–Ce co-modification significantly improved the activity of Cu/γ-Al₂O₃ catalysts, and the catalytic performance strongly depended on the Mn/Ce ratio. Among all samples, 7Mn-3Ce-10Cu exhibited the best activity, with the temperatures required for 10%, 50% and 90% methane conversion (T₁₀, T₅₀ and T₉₀) of 380.8, 427.3 and 478.7 °C, respectively. Apparent activation energy (E_a) analysis further showed that 7Mn-3Ce-10Cu possessed the lowest E_a value of 83.81 kJ mol⁻¹, indicating that the optimized Mn/Ce ratio effectively lowered the apparent kinetic barrier for methane oxidation. X-ray diffraction (XRD), transmission electron microscopy (TEM) and nitrogen (N₂) adsorption–desorption results suggested that Mn–Ce co-modification changed the phase composition, improved the dispersion state of active oxide species and generated a more favorable pore structure for reactant diffusion. Oxygen temperature-programmed desorption (O₂-TPD) and X-ray photoelectron spectroscopy (XPS) results further indicated that the enhanced activity of 7Mn-3Ce-10Cu was closely associated with improved oxygen desorption behavior, a higher proportion of surface oxygen species and favorable surface redox characteristics of Cu, Mn and Ce species. Moreover, 7Mn-3Ce-10Cu maintained methane conversion above 90% during a 50 h stability test at 500 °C, and the inhibition caused by 5% H₂O was partially reversible. These results demonstrate that Mn–Ce co-modification is an effective strategy for improving low-cost Cu-based catalysts for low-concentration methane combustion. Full article

Ni/Siral catalysts with different Si/Al ratios were prepared by incipient wetness impregnation (IWI) to assess the impact of support composition on Ni²⁺ speciation and ethylene oligomerization (EO) performance. The catalysts were characterized by X-ray photoelectron spectroscopy (XPS), H₂ temperature-programmed reduction (TPR), X-ray diffraction (XRD), NH₃ temperature-programmed desorption (TPD), high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) with energy-dispersive X-ray (EDX) analysis, and diffuse-reflectance infrared Fourier transform spectroscopy (DRIFTS). The EO catalysts were tested in a fixed-bed reactor at 225 °C under 11 bar ethylene and at 120 °C under 26 bar ethylene. Ni/Siral-70 was the most active catalyst investigated, but Ni/Siral-30 also exhibited good performance. The active sites were inferred to be isolated Ni²⁺ ions on amorphous SiO₂-Al₂O₃ containing interstitial Al³⁺ ions that enhance Brønsted acidity; Ni/Siral-70 displayed the highest concentration of these sites based on CO DRIFTS. Formation of NiAl₂O₄ surface species limited the activity of Ni/Siral-30 and especially Ni/Siral-5. The catalysts were also tested using a simulated ethane oxidative dehydrogenation (ODH) product stream containing 44% ethylene, 44% ethane, 4.5% methane, 2% H₂, 4.5% CO₂, 0.9% propylene, and 0.1% CO. The simulated ODH mixture gave lower EO conversion than 50/50 ethylene/N₂ at 225 °C and 11 bar over Ni/Siral-30, consistent with catalyst poisoning. In contrast, EO conversion over the Ni/Siral-70 catalyst was unaffected under these conditions. Catalyst testing at 120 °C and 26 bar revealed catalyst poisoning by feed impurities for both catalysts. Low-temperature/high-pressure EO activity was not recovered by simple thermal regeneration of Ni/Siral-30 at 300 °C. Full article

In this study, a hierarchically confined Pt/MnO₂–meso-Al₂O₃ catalyst with 0.5 wt% Pt loading was synthesized via a precipitation method using MnO₂ as a promoter and mesoporous Al₂O₃ (m-Al₂O₃) as a support, and its methane catalytic combustion performance and structure–activity relationship were systematically investigated. The results demonstrate that the 0.5 wt% Pt-loaded Pt-MnO₂/m-Al₂O₃ catalyst achieved 90% methane conversion at 236 °C. The enhanced performance is attributed to three synergistic mechanisms: (1) Pt doping induced lattice contraction in MnO₂ (XRD revealed a 0.03 Å reduction in the (001) interplanar spacing), which facilitated the formation of Mn³⁺–oxygen vacancy pairs (XPS indicated a Mn³⁺- content of 79.87%); (2) the MnPt₃O₆ interfacial structure (HAADF-STEM confirmed lattice spacings of 0.21 nm) accelerated oxygen species cycling, with the 0.5 wt% Pt-loaded catalyst for lattice oxygen desorption capacity (O₂-TPD) increasing by 54% compared to undoped samples; (3) the mesoporous m-Al₂O₃ carrier provided effective confinement, achieving a high specific surface area (27.6 m²/g) and sub-nanometer Pt dispersion (particle size < 2 nm). Under conditions of 1000 ppm CH₄ and a space velocity of 30,000 h⁻¹, the catalyst maintained a methane conversion rate of 98.2 ± 0.5% during continuous operation for 300 h. Post-cycling characterization revealed a stable crystalline structure (XRD full width at half maximum of 0.35° ± 0.02°) and grain size (15.5 ± 0.5 nm), confirming its robustness for industrial applications. This study provides theoretical and experimental foundations for the rational design of highly efficient catalysts for low-concentration methane elimination. For comparison, a Co-doped catalyst (1.0 wt% Co–MnO₂/Al₂O₃) was also prepared, which exhibited significantly lower activity (T₉₀ = 251 °C), underscoring the unique role of Pt in the confined architecture. This study provides theoretical and experimental foundations for the rational design of highly efficient catalysts for low-concentration methane elimination. Full article

Methane (CH₄) is a highly potent greenhouse gas whose accurate detection and quantification are essential for climate mitigation and compliance with emerging environmental regulations. Conventional monitoring approaches, including fixed monitoring stations and satellite-based observations, often exhibit limitations in terms of spatial resolution, operational flexibility, and accessibility for localized measurements. This paper presents CH4SCOUT, a modular unmanned aerial vehicle (UAV)-based platform designed for methane detection, environmental monitoring, and georeferenced data acquisition. The proposed system integrates a methane sensing module, environmental sensors, controlled airflow sampling, onboard data acquisition, and wireless communication capabilities within a UAV-compatible architecture. A three-stage signal-conditioning pipeline based on Median filtering, Hampel outlier suppression, and Exponential Moving Average (EMA) smoothing is implemented to improve measurement stability under dynamic flight conditions. Initial real-world validation flights demonstrate stable methane concentration measurements under realistic environmental conditions while maintaining reliable data transmission and telemetry synchronization. Results indicate that low-cost UAV-assisted sensing architectures can provide operationally useful methane measurements when supported by appropriate calibration and deterministic signal conditioning. Future work will focus on advanced plume localization algorithms, autonomous navigation strategies, and enhanced methane emission quantification capabilities. Full article

Enteric methane emissions (EMEs) from grazing dairy systems in tropical regions remain poorly quantified, increasing uncertainty in national greenhouse gas inventories. This study aimed to quantify EMEs using electronic spirometry masks (ESMs) in dairy cows in the Colombian high tropics during two precipitation seasons in two adjacent milk production management systems. Six cows of a high-milk-yield management system (HMYMS; >30 L/d) and six cows of a low-milk-yield management system (LMYMS; <15 L/d) grazing kikuyu grass (Cenchrus clandestinus) and supplemented with concentrate feed were monitored by EMEs, exhaled air volume, feed intake, milk yield and composition. Data were analyzed in a 2 × 2 factorial arrangement (season × production system). Season affected kikuyu chemical composition (p < 0.05) but not dry matter intake (DMI), milk production, quality, nor EMEs (p > 0.05). However, the absence of seasonal effects on these variables may be due to the sample size. Although HMY cows had a higher DMI (kg DM/d; p < 0.01) and EME (g/d, L/d; p < 0.05), they exhibited a lower methane intensity (both, L/L milk yield and L/kg fat-corrected milk) and gross energy intake lost as methane (p < 0.05). Positive correlations were found between EMEs and total dry matter intake (r = 0.638) and milk production (r = 0.726). The observed methane yield was comparable to previous studies for tropical kikuyu-based systems but lower than reports from temperate regions, suggesting seasonal-driven kikuyu quality does not translate into EME changes in high tropic regions. Animal productivity level was a key driver of EME magnitude and efficiency. Full article

This study investigated the effects of different concentrate-to-roughage ratios on the rumen microbial community, functional potential, and fermentation characteristics in yak. Forty Qinghai Plateau-type yaks (8–9 months, 68.725 ± 18.973 kg) were randomly assigned to four dietary groups with concentrate-to-roughage ratios of 80:20 (C80), 65:35 (C65), 50:50 (C50), and 35:65 (C35). After a 15-day adaptation period, animals were fed for 105 days. Rumen contents were analyzed using metagenomic sequencing combined with fermentation parameter measurements. High-concentrate diets (C80 and C65) were associated with increased relative abundance of starch-degrading and propionate-producing bacteria, such as Prevotella and Succiniclasticum, whereas low-concentrate diets (C50 and C35) were associated with higher abundance of cellulolytic bacteria, including Ruminococcus and Fibrobacter. Functional analysis indicated increased relative abundance of genes involved in glycolysis (ko00010), propanoate metabolism (ko00640), and energy-related pathways in high-concentrate groups, while fiber degradation and methane-related pathways were relatively higher in low-concentrate groups. Rumen fermentation parameters showed a significant decrease in pH with increasing concentrate level (p = 0.001), and NH₃-N concentrations differed among treatments (p = 0.036). Dietary concentrate-to-roughage ratio significantly influences rumen microbial composition, functional potential, and fermentation characteristics in yak. A moderate concentrate level (approximately 65:35) may contribute to a more balanced rumen microbial and fermentation profile under the conditions of this study. Full article

As a low-grade energy source, ventilation air methane (VAM) can be utilized via regenerative oxidation technology. However, its low methane concentration hinders self-sustained operation in regenerators. Blending pulverized coal provides a feasible approach to supplement heat input and offers a potential route for improving energy utilization and reducing methane emissions from coal mines. This study numerically investigated the heat release behaviors during the oxidation of pulverized coal-dispersed VAM in a 400 mm-long millimeter-scale regenerator channel, with particular attention to the complementary heat-release roles of methane and pulverized coal. The results show that when the wall temperature for methane oxidation increases from 1173 K to 1373 K, the methane oxidation rate rises from 3.72 mol·m⁻³·s⁻¹ to 23.87 mol·m⁻³·s⁻¹—an enhancement by a factor of 5.3. For pulverized coal, inlet velocity and coal feed rate governed the completeness of pulverized coal combustion and the volatile reaction rate, respectively. Among the four tested coal–methane heat input ratios (4:1, 3:2, 2:3, 1:4), the 4:1 case showed the most favorable burnout behavior. Further analysis of a representative 2:3 co-combustion case revealed a complementary heat-release pattern: methane provided rapid upstream heat release, whereas pulverized coal sustained the downstream high-temperature region and mitigated the temperature decay after methane consumption. Full article

Ventilation air methane (VAM) discharged from coal mines is considerable in volume, causing serious environmental pollution and energy resource waste. The methane concentration of raw VAM is generally lower than 0.3%, which greatly limits its efficient utilization. Blending low-cost solid fuels with VAM for regenerative oxidation is a practical and promising strategy to overcome the technical bottlenecks of VAM resource recovery. Clarifying the gas–solid two-phase flow behaviors inside millimeter-scale regenerative microchannels is critical for optimizing the process parameters and structural design of regenerative oxidation devices. In this work, numerical simulations are conducted using ANSYS Fluent 2022 R2 software to systematically explore the flow evolution characteristics and corresponding influencing factors of gas–solid two-phase flow in millimeter-scale microchannels to investigate three key objectives: (1) reveal the flow evolution characteristics of gas–solid two-phase flow in millimeter-scale microchannels along the flow direction; (2) quantify the effects of particle size and inlet velocity on particle deposition rate and deposition velocity; and (3) propose optimal operational parameter ranges to avoid microchannel blockage and improve particle transport performance. Along the flow direction, the near-wall velocity gradient gradually declines with the flow distance, while the thickness of the boundary layer grows continuously. Both particle deposition rate and deposition velocity are positively correlated with particle size. At an inlet velocity of 2 m/s, once the particle size exceeds 60 μm, the deposition rate and velocity rise markedly, and the particle outflow probability decreases significantly. For a fixed particle size, increasing flow velocity reduces both deposition rate and deposition velocity, which enhances the transport ability of pulverized coal particles and weakens wall adhesion. When the flow velocity is lower than 2.5 m/s, the outlet deposition rate exceeds 60%, and the particle deposition velocity rises sharply. Accordingly, maintaining flow velocity above 2.5 m/s and controlling particle size below 60 μm can effectively inhibit rapid particle deposition, improve particle transport performance, and avoid microchannel blockage. This study provides a theoretical basis and parameter reference for the structural and operational optimization of horizontal microchannels in pulverized coal-blended VAM regenerative oxidation systems. Full article

To accelerate the transition to sustainable energy, efficient methods for CO₂-free hydrogen production and carbon utilization are needed. This study presents a new, sustainable approach for the simultaneous production of hydrogen, valuable hydrocarbons, and functional carbon materials by converting methane in low-pressure microwave plasma. Compared to traditional methane reforming methods (such as steam reforming), our plasma-based process operates at low temperatures, eliminates direct CO₂ emissions, and enables the conversion of methane into three valuable products: (1) environmentally friendly hydrogen for fuel cells and energy storage systems, (2) a range of valuable organic products (C₂H₂, C₂H₄, C₂H₆), and (3) functional carbon films with self-improving catalytic properties. Optical emission spectroscopy (OES) and the Langmuir double probe method were used for plasma diagnostics, revealing an increase in the concentration of active species (CH, Hα, C₂) and electron temperature upon argon addition. The structure, morphology, and impurity composition of the deposited films were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and inductively coupled plasma mass spectrometry (ICP-MS), respectively. Gas-phase byproducts were analyzed using gas chromatography–mass spectrometry (GC-MS). Argon addition at an Ar/CH₄ ratio of 1 leads to the formation of carbon films with a more ordered structure, as confirmed by XRD data, and improved surface morphology. It was established that argon, by effectively participating in the excitation and dissociation processes of methane molecules through energy transfer from metastable states and increased electron temperature, optimizes plasma–chemical reactions, promoting the deposition of higher-quality carbon coatings. Full article

This paper presents a conceptual design for a technological installation aimed at mitigating ventilation air methane (VAM) from coal mine exhaust shafts, offering combined heat and power generation. It addresses the challenge posed by low methane concentrations (below 0.7%), which preclude direct combustion. To overcome this, the proposed concept involves diverting a portion of the VAM to a combustion chamber of the power boiler dedicated to co-combustion with flotation concentrate suspension, which is properly prepared for feeding into the combustion chamber. The heat generated in the power boiler produces steam to drive a turbine generator for electricity production. Back-pressure steam from the turbine can be utilized for district heating or as a thermal energy source for various industrial processes, optimizing the plant’s energy efficiency and reducing its environmental footprint. The feasibility of this technology hinges on its cost-effectiveness and energy efficiency. This aspect of efficiency has been outlined. An energy balance analysis, based on real emission data from a selected mine, is provided to determine power boiler efficiency, fuel consumption, and a VAM reduction rate. The forecast of the amount of energy produced was presented for a single installation with a grate boiler capable of co-firing fuels with a VAM flow participation of 25 m³/s. Such installations can be scaled to meet mine requirements, enabling the neutralization of VAM at a total capacity of up to 300 m³/s, which corresponds to emissions from a large ventilation shaft. Full article

Substituting hydrocarbon fuels such as methane (CH₄) with ammonia (NH₃) reduces CO₂ emissions in gas turbines, but ammonia’s low reactivity challenges flame stability. Dual-swirl staged combustors using a low thermal power (P_pilot) pilot flame can stabilise the main flame. This work compares the morphologies and stabilities of NH₃/air premixed swirl flames using ammonia and methane pilot flames (APF and MPF). Flame imaging and simultaneous OH-NH planar laser-induced fluorescence (PLIF) are employed to analyse flame morphology. Main flame stability is assessed by measuring the lean blow-off equivalence ratio (ϕ_b,main). The results show that MPF significantly outperforms APF in main flame stabilisation. At P_pilot = 1.2–1.8 kW (14.2–21.3% of P_main), the dual-swirl flames exhibit a stratified structure, with OH concentrated in the pilot stage. Flames with MPF exhibit considerably lower ϕ_b,main than those with APF. For example, at P_pilot = 1.6 kW, ϕ_b,main is reduced to 0.42 with MPF, compared to 0.56 with APF, demonstrating MPF’s superior stabilisation capability. MPF can reduce CO₂ emissions by 82.4–87.6% compared to a CH₄ flame of equivalent thermal power. Two stabilisation modes are identified, namely primary recirculation zone-dominated and pilot-dominated modes. These findings demonstrate that a low-power MPF provides an effective strategy for enhancing ammonia flame stability and reducing CO₂ emissions in gas turbines. Full article