Search Results (2,795)

Cobalt-based catalysts using aluminum oxide as a support and 0.025–0.10 wt.% iridium as a second metal were prepared by the impregnation method and tested in steam and dry reforming of a model biogas with a ratio of CH₄:CO₂ = 1:1. The processes were carried out in a fixed bed flow reactor under atmospheric pressure with a gas hourly space velocity of 1000–1500 h⁻¹, and temperature varied in the range of 300–800 °C. The BET surface area, XRD, SEM, TEM, and H₂-TPR methods were conducted to characterize the physicochemical properties of the “fresh” and “spent” samples of catalysts. The catalysts exhibit high and stable activity in the production of syngas from the biogas. Methane was almost completely converted at 750–800 °C in the steam reforming of biogas. Stability tests over 80–100 h confirmed the catalyst’s stable operation. Syngas with a ratio of H₂/CO ~ 0.9 is formed in dry reforming of biogas, while in steam reforming the ratio exceeds 1. It is believed that the addition of iridium to Co/Al₂O₃ causes improvement of catalyst performance due to a synergetic effect because of the interaction between Co and Ir. Full article

Increasing surface albedo can reduce absorbed solar radiation and generate negative radiative forcing, but its application to landfill covers remains insufficiently investigated. This study assessed the potential climate benefit of reflective cover systems at the Malagrotta landfill in Rome, Italy, by integrating unmanned aerial vehicle (UAV) radiometry, Sentinel-2 imagery, shortwave-radiation modeling, and CO₂-equivalence methods. The existing landfill exhibited low and heterogeneous reflectance. Quality-controlled Sentinel-2 observations produced seasonal mean albedos ranging from 0.0819 in winter to 0.1236 in summer, with a radiation-weighted baseline albedo of 0.1091. UAV campaign means ranged from 0.1391 to 0.2145. Comparisons over common 20 m cells showed that Sentinel-2 underestimated UAV albedo by approximately 0.087 on average (RMSE ≈ 0.093), demonstrating that the two platforms should not be considered interchangeable without site-specific calibration. Five hypothetical reflective-cover scenarios with albedos of 0.55–0.75 were subsequently evaluated. Relative to the existing surface, annual absorbed shortwave energy decreased from 1481.1 kWh m⁻² to 748.1–415.6 kWh m⁻², equivalent to reductions of 49.5–71.9%. After accounting for modeled atmospheric transmission, avoided absorbed energy at the top of the atmosphere ranged from 487.4 to 708.9 kWh m⁻² yr⁻¹. Under a three-year material service life, the modeled compensation was 71.49–103.98 kg CO₂-eq m⁻² over a three-year assessment horizon. Alternative literature-based conversion methods yielded landfill-scale estimates of approximately 31,700–142,000 tCO₂-eq, highlighting substantial methodological uncertainty. The findings indicate that reflective landfill covers could provide a meaningful supplementary climate benefit on low-albedo, centrally managed surfaces. However, the results are scenario-based and represent radiative equivalence rather than physical CO₂ removal or avoided methane emissions. Field trials, multiyear monitoring, complete surface-energy-balance measurements, and cradle-to-grave life-cycle assessment are required before operational deployment or carbon-offset applications. Full article

The Dry Reforming of Methane (DRM) is an efficient route to produce syngas (which is the feedstock for the production of synthetic fuels via the Fischer–Tropsch process) or hydrogen from methane and carbon dioxide. This work evaluates several nickel-based perovskite-type mixed oxides (La_xNiO₃, La_0.8Ni_0.9M_0.1O₃ (M = Co, Fe and Mn) and La_0.8Ni_1−yCo_yO₃) as precursors of the active phase (Ni) for the DRM reaction. Although La_0.8NiO₃ yields slightly smaller Ni particles after reduction, it promotes the accumulation of a significant amount of carbonaceous material during DRM. Partial Ni substitution with Co, Fe and Mn improves redox stability, with the La_0.8Ni_0.75Co_0.25O₃ formulation being the most effective for removing the carbonaceous deposits under a 25% CH₄, 25% CO₂ (50% He) reactant atmosphere. However, when this formulation is used as a catalyst precursor for DRM under more realistic conditions (i.e., employing a feed that simulates real biogas), CH₄ conversion and H₂ yield decrease, and the carbon accumulated increases due to the greater influence of the parallel reactions. As a positive sign for future applications or research, under these conditions, the addition of 0.5% O₂ to the feed and the use of a CO₂ regeneration step decreased the amount of carbonaceous material deposited. Full article

Air-pollution source control is usually prioritised by emission mass, yet the health damage per tonne emitted varies widely in space. Using agricultural-residue open burning in Northern Thailand as a case study, we couple a GIS emission inventory with a province-resolved damage-function health model to quantify the health and economic burden, quantify how the health damage per tonne emitted varies across provinces, and apportion the co-benefits of diverting residue from open burning between air-quality and climate gains. In 2018, residue burning released about 21 kt of PM_2.5, 3.0 kt of black carbon and 0.84 Mt CO₂-eq of net non-biogenic greenhouse gases (methane and nitrous oxide), together with 6.2 Mt of biogenic CO₂ that is refixed by the following crop and is not a net climate source, with rice, sugarcane and maize contributing 39%, 35% and 20% of fine particles respectively, imposing costs of 59,600 disability-adjusted life years (DALYs; 97.5% from primary PM_2.5) and ~USD 1.07 billion per year. The damage caused per tonne emitted varied 4.8-fold among provinces (1.43–6.85 DALY per tonne of PM_2.5), so the largest emitter (Nakhon Sawan) was not the province whose emissions caused the largest attributable burden (Phetchabun); damage-weighted prioritisation therefore identifies where diversion yields the greatest benefit. Diverting rice and maize residue avoided 12 kt PM_2.5, 1.6 kt black carbon and 0.56 Mt CO₂-eq of net greenhouse gas, and 60% of the health and economic burden; extending diversion to sugarcane raised these to 20 kt, 2.9 kt, 0.79 Mt CO₂-eq and 95% (USD 1.02 billion per year), so a three-crop strategy is required. Rice-only and maize-only diversion were not clearly separable (rice-only was larger in 64% of the Monte Carlo draws). Full article

China’s deep coalbed methane (CBM) resources hold significant development potential, yet their commercial exploitation remains hindered by four interrelated reservoir challenges: substantial burial depth, elevated in situ stress, ultra-low matrix permeability, and pronounced stress-dependent permeability decline. These conditions collectively induce rapid reservoir energy depletion and flow-path deterioration, leading to characteristic production behavior—namely, high initial gas rates followed by steep decline and persistent instability in long-term output. Accordingly, a rigorously optimized production system is indispensable to suppress formation damage, sustain desorption-driven gas release, and maximize ultimate recovery efficiency. To address this, this study establishes a physics-based numerical model that integrates field-calibrated geological and operational parameters, gas–water two-phase flow dynamics, coupled desorption–diffusion–seepage processes, and quantitatively constrained stress–permeability relationships for coal. Implemented in the CMG-IMEX simulator, the model is validated through robust history matching against production data from ten representative wells. A comparative analysis of two drawdown management strategies—the conventional constant-decline approach and the progressively decreasing drawdown strategy—demonstrates clear performance differentiation in both cumulative production and reserve utilization. Under the conventional scheme, the average ultimate recovery factor at economic abandonment reaches only 36.42%, with adsorbed-gas recovery limited to 25.53%, underscoring substantial untapped resource potential. In contrast, the progressively decreasing drawdown strategy alleviates multiphase flow restrictions, improves pressure maintenance, and elevates the average ultimate recovery factor to 40.43%—a net gain of 4.43 percentage points in adsorbed-gas recovery. Sensitivity analysis further identifies an initial drawdown of 5 MPa as the optimal balance between early productivity and reservoir sustainability. The coupling among reservoir pressure, flowing bottomhole pressure, and casing pressure enables the bottomhole drawdown-control protocol to be converted into a surface-measurable casing-pressure decline-rate criterion. These findings improve the mechanistic understanding of gas–water co-production in deep CBM systems and provide an operational framework for production-system design. Full article

Anaerobic digestion enables simultaneous organic waste treatment and renewable energy production. However, the presence of CO₂ in biogas limits its calorific value and restricts its direct use as a fuel, making upgrading processes necessary. This study investigated an integrated approach combining anaerobic treatment of potato processing wastewater in a 12 L Upflow Anaerobic Sludge Blanket (UASB) reactor with ex situ biomethanation in a Trickle Bed Reactor (TBR). The UASB reactor was operated for 170 days under different hydraulic retention times (HRTs) and organic loading rates (OLRs), while ex situ biomethanation was subsequently evaluated in the TBR using green hydrogen and a synthetic CH₄/CO₂ gas mixture representative of the UASB-derived biogas composition. The UASB reactor achieved a maximum biogas production rate of 14.5 ± 3.2 L d⁻¹ with a methane content of 74.5 ± 2.1% at an OLR of 3.5 g COD L⁻¹ d⁻¹ and an HRT of 1.2 days. Subsequent biomethanation in the TBR increased biomethane purity to 98.1%, demonstrating effective CO₂ conversion through hydrogenotrophic methanogenesis. Process performance was further evaluated using Anaerobic Digestion Model No. 1 (ADM1), providing mechanistic insights into reactor operation and stability. The results demonstrate that combining UASB treatment with subsequent TBR biomethanation enhances carbon utilization and biomethane quality, offering a sustainable pathway for energy recovery from industrial wastewater. Full article

Although combustion technology is used in various fields, carbon dioxide is emitted when fossil fuels are burned. Using methane, the main component of natural gas, mixed with a non-carbon-dioxide-emitting fuel is a practical solution. In this study, we focused on hydrogen as a zero-emission fuel and examined the associated challenges. As a case study, we considered co-combustion in which the methane (the main component of LNG) was replaced with hydrogen, analyzing the impact on carbon dioxide emissions, calorific value, and price. Similarly, we examined ammonia and compared it with hydrogen. Taking into account the CO₂ emissions permitted during fuel production under the Act on the Promotion of a Hydrogen Society, the reduction rate is lower when methane is replaced with hydrogen or ammonia. When methane is completely replaced with hydrogen, the CO₂ emissions from the fuel production process would still amount to 15% of those from a 100% methane fuel. In contrast, this value rises to 33% for ammonia, indicating that the CO₂ reduction effect of ammonia is smaller than that of hydrogen. Full article

To use renewable energy and mitigate the greenhouse gas effect on the environment, carbon dioxide (CO₂) separation is crucial. Recent research has shown that using membranes for CO₂ separation is a vital option, but challenges remain with permeability and selectivity. Blend hollow fiber membranes offer a solution to these challenges. In this study, a blend of hollow fiber membranes made of polyether sulfone (PES) and polyvinyl acetate (PVAc) was developed, along with the incorporation of fillers, to overcome the permselectivity challenge. This resulted in the creation of mixed matrix blend hollow fiber membranes by using the phase inversion method. The membranes that were developed were examined using FESEM, FTIR, XRD, TGA, and pure-gas permeation analysis. The polymer blend demonstrated miscibility and preserved strong morphological and structural stability during CO₂ and CH₄ separation tests, exhibiting little deformation and reliable performance across different feed pressures ranging from 2 to 8 bar. The addition of TiO₂ improved the compatibility of the polymer blend and increased the mobility of CO₂. At 8 bar, the optimized PES/PVAc–5 wt.% TiO₂ hollow fiber membrane reached a CO₂ permeance of 92.22 GPU, representing an enhancement of about 24.7% in CO₂/CH₄ selectivity compared to the standard membrane. This emphasizes its potential for effective biogas upgrading under high pressure. Full article

The integration of bioactive compound extraction with anaerobic digestion (AD) represents a promising strategy for maximizing the valorization of agro-industrial residues within circular biorefinery systems. However, the extraction of valuable compounds may reduce or enhance the methane potential of the remaining biomass, making it important to evaluate the feasibility of subsequent energy recovery. This study investigates AD and anaerobic co-digestion (AcoD) of tomato pomace after supercritical CO₂ extraction (TPCO₂) and green walnut shell after ethanolic extraction (GWSe), aiming to identify synergistic interactions capable of enhancing biomethane production. Batch biochemical methane potential (BMP) assays were performed under mesophilic conditions using laboratory-scale (500 mL) reactors, followed by experiments in 5 L reactors. The mono-digestion of TPCO₂ and GWSe resulted in low methane yields of approximately 169 and 105 NmL CH₄ g⁻¹ VS, respectively. In contrast, AcoD enhanced methane production, reaching 361 NmL CH₄ g⁻¹ VS for the 0.50:0.50 mixture, with 409 NmL CH₄ g⁻¹ VS obtained in 5 L reactors (scale-up assay), confirming that the synergistic effect was maintained at larger reactor volumes. Kinetic modeling using a first-order model with a lag phase adequately described methane production (R²adj = 0.88–0.99) and indicated rapid microbial adaptation under all experimental conditions. Based on the BMP results obtained in the 5 L reactor, the estimated availability of the residues in Portugal, and assuming an electrical conversion efficiency of 35%, the 0.75:0.25 mixture could theoretically generate 5.50 × 10⁷ kWh year⁻¹ of electricity, equivalent to the annual electricity demand of approximately 40,400 inhabitants. These findings demonstrate that residual biomasses generated after supercritical CO₂ and ethanolic extraction remain suitable feedstocks for biomethane production and highlight AcoD as an effective strategy for integrating renewable energy generation into agro-industrial biorefineries. Full article

Ni-based catalysts supported on kaolin were synthesized via solution combustion synthesis and promoted with Fe and/or La to investigate their catalytic performance in CO₂ methanation. Catalytic tests showed that Fe significantly improved CO₂ conversion from approximately 52% for Ni-catalyst to 83% for Ni2.5Fe_SCS at 300 °C. However, the promotional effect of Fe showed only a weak dependence on its loading, with Ni modification already being achieved at the lowest Fe content. Among all investigated catalysts, the La-promoted sample exhibited the highest CO₂ conversion (85% at 300 °C), owing to the formation of highly dispersed Ni⁰ crystallites, enhanced surface basicity, and strong metal–support interactions. These interactions also effectively suppressed particle sintering during prolonged stability tests. In contrast, simultaneous promotion with Fe and La did not provide additional catalytic enhancement, indicating that the effects of both promoters were not simply additive. Full article

The eastern Ordos Basin holds substantial natural gas resources, yet its development performance varies considerably across different areas, and the underlying causes merit close attention. Taking the Mizhi–Qingjian Block as a case study, this paper integrated petrophysical tests, well-logging interpretation, and volumetric resource estimation to characterize the development of TSM (tight sandstone methane) and deep CBM (coalbed methane) reservoirs in the BX Fm (Benxi Formation) to H₈ Mb (He 8 Member) interval. The results indicate that the H₈ Mb effective sandstones exhibit the best reservoir development. The No. 8 coal seam is markedly thicker than the No. 5 coal seam. Water-bearing zones are extensively distributed in the Qingjian Block. Resource potential assessment shows that the TSM resources in the BX Fm–H₈ Mb interval total 1962.72 × 10⁸ m³, of which Class I + II amount to 905.47 × 10⁸ m³. The deep CBM resources of the No. 5 and No. 8 coal seams together reach 9974.31 × 10⁸ m³, with Class I + II accounting for 5503.83 × 10⁸ m³. On this basis, a synergistic co-production technology has been developed to enable efficient and coordinated extraction of both TSM and deep CBM resources. Northern Mizhi is identified as the primary development target, while the Qingjian area requires cautious planning due to high water content. Full article

The methanation of pyrolysis gas was investigated using the open access software DWSIM v9.0.5 to assess its potential for producing methane-rich gas. The pyrolysis gas composition was derived from known experimental tests of anthropogenic residues, namely sewage sludge and digestate. Four gas compositions were considered; they were obtained by the pyrolysis of residues with and without a sorbent for CO₂ capture. The methanation process was simulated by a non-stoichiometric thermodynamic approach to calculate the chemical equilibrium composition of the gas. A parametric investigation was carried out under a temperature range of 300–500 °C and a pressure range of 10–40 bar. Carbon oxide conversion, methane selectivity and methane yield were calculated. CO almost underwent quantitative conversion, while CO₂ showed significantly lower or negative conversion. Synthetic biogas was obtained from the pyrolysis gas of the residues, showing a methane content of about 50 mol%. Synthetic natural gas was obtained from the pyrolysis gas residues plus sorbent, showing a methane content of about 90 mol%. Full article

Ukraine entered the definitive period of the EU Carbon Border Adjustment Mechanism (CBAM) in January 2026 as the largest exporter of CBAM-covered goods to the EU by physical volume, while its industrial base remains under direct wartime pressure. This study provides the first structural analysis of the open microaggregated dataset of the State Statistics Service of Ukraine (SSSU) on air pollutant and greenhouse gas emissions, covering 1990–2025 across 1284 territorial units, 128 substances, and 605 economic activities (NACE/KVED-2010). A documented harmonization procedure is proposed that resolves the 2020/2021 dimensional break and the ambiguity between oblast (region)- and hromada (municipality)-level records, yielding consistent 36-year series with independent national total validation for 2015–2025. Four phases are identified: transformational decline (1990–1999, −56.5%), stabilization (1999–2013, +4.6%), post-2014 structural decline (2013–2021, −47.9%), and the full-scale war shock (2021–2025, −55.0%). Stationary source emissions fell by 89.3% overall, but the wartime reduction reflects destruction and occupation of capacity, not decarbonization, as reflected in the collapse of metallurgy (−73.8%) and coke production (−89.6%) and the loss of the Mariupol district from statistical coverage after 2022. Mobile sources now supply 65% of the national total. Coal mine methane dominates stationary CH₄ (301 kt in 2021; ≈9.0 Mt CO₂ eq), directly relevant to Regulation (EU) 2024/1787. The regional Herfindahl–Hirschman index fell from 1847 (2021) to 1524 (2025), indicating war-driven regional deconcentration and a westward shift in the emission center of gravity. The findings are validated against independent satellite-based and conflict attribution estimates, and implications for monitoring, reporting and verification (MRV) infrastructure, CBAM default value exposure, and the phased design of Ukraine’s emissions trading system are derived. Full article

This study presents a 3D computational fluid dynamics (CFD) investigation of methane and methanol combustion in a medium-speed, large-bore marine spark-ignition engine equipped with a pre-chamber (PC) ignition system. Simulations were performed in ANSYS Forte at 100%, 80%, and 20% engine load. Methane operation with an active PC was used as the reference configuration, while methanol was investigated with both active and passive PC. A preliminary injection-timing analysis was conducted for the active methanol configuration to obtain a near-stoichiometric and sufficiently homogeneous mixture inside the PC at spark timing (ST). The results show that active methanol operation promotes earlier heat release, shorter combustion duration, and higher thermal efficiency than methane operation. The active PC generates stronger turbulent reacting jets and ensures more robust combustion than the passive configuration. Methanol also considerably reduces NO_x emissions because of its lower initial and combustion temperatures. However, active methanol operation increases CO emissions, particularly at low load, because of incomplete oxidation associated with low temperatures, mixture inhomogeneity, and possible spray–wall interaction. The passive PC further reduces NO_x and CO emissions but causes delayed combustion, lower thermal efficiency, higher fuel consumption, and tank-to-wake CO₂ emissions than the active methanol configuration. Full article

Underground coal mining operations remain significantly threatened by the accumulation of methane (CH₄) and carbon monoxide (CO): Methane poses an acute explosion risk, and carbon monoxide serves as a critical biomarker for spontaneous coal combustion. Consequently, rigorous real-time monitoring to ensure environmental safety is necessitated, which is based on superior gas sensor devices. Although various detection modalities exist, conventional methods are frequently constrained by environmental sensitivity and limitations regarding long-term sensor stability. This review provides a comprehensive analysis of recent advancements in chemiresistive gas sensors based on metal oxide (MO) semiconductor materials with low cost, high stability, high sensitivity, and easy preparation, which are engineered for the detection of methane and carbon monoxide in coal mining environments. This study examines the redox-sensing mechanisms of both n-type and p-type MO semiconductors, for which special attention is directed toward optimization strategies designed to overcome the high activation energy of methane and improve carbon monoxide response kinetics. Importantly, novel approaches to lower high operating temperatures and improve the selectivity of MO sensors under complex mine environments have been comprehensively discussed. Full article