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The direct conversion of methane to methanol has attracted increasing interest due to abundant and low-cost natural gas resources. Herein, by anchoring Cr-oxo/-oxyhydroxides on UiO-66 metal–organic frameworks, we demonstrate that reactive anionic oxyl radicals can be formed by controlling the coordination environment based on the results of density functional theory calculations. The anionic oxyl radicals produced at the completely oxidized CrVI site acted as the active species for facile methane activation. The thermodynamically stable CrVI-oxo/-oxyhydroxides with the anionic oxyl radicals catalyze the activation of the methane C–H bond through a homolytic mechanism. An analysis of the results showed that the catalytic performance of the active oxyl species correlates with the reaction energy of methane activation and H adsorption energies. Following methanol formation, N2O can regenerate the active sites on the most stable CrVI oxyhydroxides, i.e., the Cr(O)4Hf species. The present study demonstrated that the anionic oxyl radicals formed on the anchored CrVI oxyhydroxides by tuning the coordination environment enabled facile methane activation and facilitated methanol production. [ABSTRACT FROM AUTHOR]

Photofragment spectroscopy is used to measure the vibrational spectra of V 2 + (CH 4) n (n = 1–4), V 3 + (CH 4) n (n = 1–3), and V x + (CH 4) (x = 4–8) in the C–H stretching region (2550–3100 cm−1). Spectra are measured by monitoring loss of CH4. The experimental spectra are compared to simulations at the B3LYP+D3/6-311++G(3df,3pd) level of theory to identify the geometry of the ions. Multi-reference configuration interaction with Davidson correction (MRCI+Q) calculations are also carried out on V 2 + and V 3 + . The methane binding orientation in V 2 + (CH 4) n (n = 1–4) evolves from η3 to η2 as more methane molecules are added. The IR spectra of metal-methane clusters can give information on the structure of metal clusters that may otherwise be hard to obtain from isolated clusters. For example, the V 3 + (CH 4) n (n = 1–3) experimental spectra show an additional peak as the second and third methane molecules are added to V 3 + , which indicates that the metal atoms are not equivalent. The V x + (CH 4) show a larger red shift in the symmetric C–H stretch for larger clusters with x = 5–8 than for the small clusters with x = 2, 3, indicating increased covalency in the interaction of larger vanadium clusters with methane. [ABSTRACT FROM AUTHOR]

Due to its abundant resources and advantages in transportation and storage, methane fueled solid oxide fuel cells (SOFCs) are highly needed. In this work, an exceptional internal reforming catalyst comprising in-situ exsolved NiRu bimetallic nanoparticles and oxygen-deficient layered double perovskite LaBaMn 1.6 Ni 0.3 Ru 0.1 O 5+δ (r-LBMNR) was prepared. Compared to the cell with LaBaMn 1.6 Ni 0.4 O 5+δ (r-LBMN) catalyst, the cell with a Ru-doping r-LBMNR catalyst layer, exhibits superior peak power output of 336 mW cm−2 and better durability with a less decay rate of 0.014% per hour in CH 4 fuel. The enhanced electrochemical performance can be attributed to the high oxygen ion and electron conductivities of the catalyst and the coupling of Ni and Ru sites with the oxygen-deficient r-LBMNR matrix This coupling activates CH 4 and H 2 O, promotes the oxidation of C atoms in CH 4 molecules, and enables reversible hydrogen spillover, ultimately leading to the production syngas of CO(g) and H 2 (g). [Display omitted] • Trace Ru-doping facilitating the exsolution of nanoparticles. • LaBaMn 1.6 Ni 0.3 Ru 0.1 O 5+δ was modified with abundant O v and exsolved NiRu alloy. • Cell can operate stably over 220 h with a degradation rate of 0.014% h−1. [ABSTRACT FROM AUTHOR]

The country's energy demand is experiencing rapid growth, and fossil fuels remain the primary resources to meet this increasing need. However, global warming poses a significant challenge for governments and industries worldwide. To address this issue, utilizing methane as a fossil fuel and implementing CO2 capture and sequestration can prove to be effective mitigation strategies. This paper presents an innovative idea to utilize unmineable coal seams in the Singrauli coal field for CO2 sequestration while extracting associated CBM to offset the cost of the sequestration process. The findings reveal that the field has great potential for CO2 sequestration. The estimated average maximum sorption capacities of CO2 and CH4 in the coal seams under in situ conditions of the basin are 39.50 m3/t and 11.15 m3/t, respectively. The total maximum sorption capacities of CO2 and CH4 in the potential coal seams are estimated to be 10,758.00 Mm3 and 3,215.00 Mm3, respectively. These results indicate that the unmineable coal seams in the Singrauli coalfield hold potential for CO2 sequestration and the extraction of available CBM from the coal seams. [ABSTRACT FROM AUTHOR]

This study investigated the anaerobic co-digestion of sugarcane vinasse (V) and elephant grass silage (S) to produce methane. Box-Behnken experimental design was applied to verify the statistical effects of the elephant grass ensiling time (40, 80 and 120 days), alkaline pretreatment of elephant grass silage (0.5, 2.25 and 4.00% w/v NaOH) and S:V mixture ratio (25:75, 50:50 and 75:25) on the methane yield. The results showed that the ensiling process resulted in the low degradation of lignocellulosic substances, emphasizing the need for pretreatment using more efficient techniques, such as thermo-alkaline, to improve the breakdown of elephant grass fibres. COD removals varied between 35 and 85%, and carbohydrate consumptions ranged from 63 to 72%, with the higher efficiencies for both parameters occurring in the reactors with lower percentages of silage. Cumulative methane yield ranged from 190.77 mLCH4/gVS (in the reactor with S:V of 75:25, 0.50% w/v NaOH and 80 ensiling days) to 1729.80 mLCH4/gVS (in the reactor with S:V of 25:75, 2.25% w/v NaOH and 120 ensiling days). According to ANOVA, S:V ratio was the only variable with a significant effect (p < 0.05) on cumulative methane yield. Therefore, the findings indicate that the relative composition of substrates within the mixture exerted the most significant influence on the process, underscoring the critical role of vinasse as a co-substrate in enhancing methane production despite silage pretreatments. [ABSTRACT FROM AUTHOR]

The anaerobic digestion (AD) process is one of the most practiced technologies for the remediation of organic waste and maximization of energy recovery in terms of biogas or biomethane. The presence of other gaseous components in biogas, e.g. CO2 and H2S, often makes its direct application in engines and electricity production unsuitable. This work aimed to develop and utilize an algae-assisted microbial fuel cell (AMFC) for the purification of biogas by removing both CO2 and H2S and simultaneous bioelectricity generation. In addition to biogas clean-up, elemental sulfur recovery and CO2 utilization for algae cultivation add value to the proposed AMFC process. Experiments were performed with both sulfide and bicarbonate in their dissolved form, in the respective anodic and cathodic chambers of the AMFC. The sulfide concentration was varied from 100 to 800 mg/l and the AMFC exhibited a sulfide removal efficiency exceeding 97% at all concentrations tested. The process efficiency dropped, however, at sulfide concentrations above 300 mg/l in terms of both sulfide removal and power output. The AMFC performed best at 400 mg/l sulfide by exhibiting a power density of 24.99 mW/m3 and sulfide removal efficiency of 98.87%. The system exhibited columbic efficiency (CE %) in the range of 7.85–80%. The total alkalinity representing CO2, carbonate and bicarbonate levels in the algae-based system was reduced by 49.54%. The electrical energy recovered from the AMFC was 0.1 kWh/m3 and the total energy recovery, which is the sum of the electrical and algal lipid energy, amounted to 7.25 kWh/m3. [ABSTRACT FROM AUTHOR]

As a new type of energy, hydrogen-enriched methane mixed fuel has a high risk of deflagration in the application process. In order to better understand the deflagration and inhibition characteristics of hydrogen-enriched methane fuel, the effect of potassium salt modified dry water material (DW) on the deflagration characteristics of hydrogen-enriched methane fuel was studied by 20 L spherical explosive apparatus, combined with pyrolysis characteristics and kinetic model. The results show that when the addition of different modifier concentrations, it can be divided into three types: small curvature, medium curvature and large curvature according to the change of pressure rising rate. With the increase of the proportion of potassium salt modifiers, the number of areas with small curvature is gradually increasing, the number of large curvature is gradually decreasing, and the number of medium curvature is almost unchanged. When the proportion of potassium salt modifier is 15% and ϕ ≤ 0.7, all enter the area below the medium curvature. When the addition of different modifiers, 15%KCl-DW has the best inhibition effect on P max and (dP/dt) max , while CH 3 COOK-DW and K 2 CO 3 -DW have better inhibition effect on Δ t 2 and Δ t 2. In general, when the hydrogen addition ratio is less than 70%, the addition of inhibitors can significantly reduce the explosion intensity. In terms of inhibition mechanism, we established the decomposition model of potassium salt modified dry water and found that potassium salt modified dry water will produce a large amount of gaseous K and KOH in the explosion system. And gaseous K and KOH will catalyze each other and combine with H and OH to form stable H 2 O, which significantly reduces the mass fraction of H and OH radicals in the chain reaction. The results of this paper provide a theoretical basis for the safe use of hydrogen-enriched methane fuel and the research and development of explosion emergency prevention and control technology. • The explosion suppression of potassium salt modified dry water on H 2 /CH 4 was studied. • The hierarchical inhibition model of H 2 /CH 4 explosion by dry water was defined. • Particle swarm optimization is adopted to optimize the decomposition parameters of DW. • Suppression mechanism of potassium salt modified dry water was analyzed. [ABSTRACT FROM AUTHOR]

Compounds containing the thiophene moiety find several applications in physics and chemistry, such as electrical conduction, which depends on specific conformations to properly exhibiting the desired properties. In turn, chalcogen bonding has found to modulate the conformation of some N‐thiophen‐2‐ylfomamides. Since halogens participate in a kin interaction (halogen bonding) and are abundant in agrochemicals, pharmaceuticals, and materials, we have quantum‐chemically explored the interaction between organic halogen and thiophene as a conformational modulator in some model compounds. Although such interaction indeed appears, as demonstrated by atoms in molecules and natural bond orbital analysis, it is inefficient to control the conformational equilibrium. An energy decomposition analysis scheme demonstrated that halomethane and thiophene tend to move away from one another due to a core component (Pauli repulsion and exchange), which is mainly due to a deformation term. Therefore, chalcogen bonds with halogens appear weaker than with other chalcogens. [ABSTRACT FROM AUTHOR]

Understanding and optimising biological pre‐treatment strategies for enhanced bio‐methane production is a central aspect in second‐generation biofuel research. In this regard, the application of fungi for pre‐treatment seems highly promising; however, understanding the mode of action is crucial. Here, we show how aerobic pre‐treatment of crystalline cellulose with the cellulolytic Trichoderma viride affects substrate degradability during mesophilic, anaerobic digestion. It could be demonstrated that fungal pre‐treatment resulted in a slightly reduced substrate mass. Nevertheless, no significant impact on the overall methane yield was found during batch fermentation. Short chain organic acids accumulation, thus, overall degradation dynamics including methane production kinetics were affected by the pre‐treatment as shown by Gompertz modelling. Finally, 16S rRNA amplicon sequencing followed by ANCOM‐BC resulted in up to 53 operative taxonomic units including fermentative, syntrophic and methanogenic taxa, whereby their relative abundances were significantly affected by fungal pre‐treatment depending on the duration of the pre‐treatment. The results demonstrated the impact of soft rot fungal pre‐treatment of cellulose on subsequent anaerobic cellulose hydrolysis as well as on methanogenic activity. To the best of our knowledge, this is the first study to investigate the direct causal effects of pre‐treatment with T. viride on basic but crucial anaerobic digestion parameters in a highly standardised approach. [ABSTRACT FROM AUTHOR]

Context: This study primarily investigates the changes in carbon adsorption capacity and hydrogen adsorption capacity on the anode catalyst surface when using methane fuel and mixed gas fuel as the anode fuel for SOFC systems. To reduce the carbon adsorption capacity of the commonly used anode catalyst—nickel-based catalysts—towards hydrocarbon fuels, copper and gold are doped into the nickel-based catalysts to compare the effects on carbon and hydrogen adsorption capacities. Moreover, aside from calculating the carbon and hydrogen adsorption capacities, this project also evaluates the impact of mixed gas effects and doping effects on SOFC performance through the analysis of hydrogen diffusion coefficients and performance polarization curves. The findings reveal a noteworthy enhancement in the diffusion coefficient of syngas within the Au-doped Ni catalyst, showing an improvement of up to 45.46% at 973 K. Furthermore, the electrical power generated by syngas in the Au-doped Ni catalyst at 973 K demonstrates an increase of up to 12.06%. Methods: This study primarily employs DFT to calculate the carbon and hydrogen adsorption energies on methane, utilizing CASTEP for the calculations. During these calculations, the adsorption energy is determined through a three-layer surface approach, in conjunction with the Kohn–Sham equations, combining the Generalized Gradient Approximation and ultrasoft pseudopotentials for TS-search calculations. On the other hand, this project will analyze the diffusion coefficient of hydrogen on the anode catalyst using MD methods combined with the ReaxFF potential field, with GULP being utilized to complete all dynamics calculation theories. Finally, the project will analyze the performance of SOFC cells, incorporating relevant numerical equations with Matlab for numerical analysis. [ABSTRACT FROM AUTHOR]

The present paper illustrates the results of an experimental study aimed at evaluating the effect of lubricant oil features on the emissive behaviour of a heavy duty spark ignition engine fuelled with methane. The activity was performed within a research project between CNR-STEMS and TotalEnergies in which oils with different formulations were characterized, focusing on their potentiality in particle emission reduction. Considering the ultralow particle emission level in the exhaust of gas engines, a specific testing procedure was designed to guarantee highly reliable and accurate results. In particular, the engine was operated under transient conditions, along the World Harmonized Transient Cycle in cold- and hot-start conditions. The results of the test campaign clearly highlight that the lubricant formulation is a key technology for the control of particles, revealing this as an important aspect in view of the upcoming severe regulation limits on particle emissions. The experimental findings show the capability of reformulated oils to drop down the total particle number to 60–70% with respect to a baseline standard oil. The interest in the present study also lies in providing information extendable to more sustainable fuels, like hydrogen or biomethane, nowadays of great interest as alternative energy sources. [ABSTRACT FROM AUTHOR]

Green ammonia has become an increasingly popular fuel in recent years because of its combustion process without carbon oxide release. Adding ammonia to methane fuel for co-combustion has become one of the important research topics in the current combustion field. In the present study, the CH4/NH3/Air counterflow diffusion flame was taken as the research object, and Chemkin-2019 R3 software was used to explore and analyze the flame extinction limit and chemical kinetics characteristics under different ammonia mixing ratios, initial pressures, and air preheating temperatures. It was obtained that the flame extinction stretch rate was decreased by increasing the NH3 mole fraction in the CH4/NH3 mixed fuel. The increase in pressure or air preheating temperature would accelerate the chemical reaction rate of each component in the combustion process, increase the flame extinction limit, and counteract the "stretching effect" of the flame, thus restraining the flame extinguishing phenomenon. The results of a path analysis show that the formation and consumption of OH had an important influence on flame extinction in the chain reaction. The net reaction rate of OH increases with increasing the initial pressure or air preheating temperature, which leads to an increase in flame intensity, combustion stability, and the extinction limit. Furthermore, the function curve between the reaction influences the RIF factor and the stretch rate of the first-to-ten reactions, affected by the heat release of flame combustion, was drawn and quantitatively analyzed. Eventually, a sensitivity analysis of the flame under different working conditions was completed, which found that promoting the forward reaction R39 H + O2<=>O + OH also promotes the positive combustion as a whole when the flame was near extinction. The sensitivity coefficient of R39 in the CH4/NH3/Air flame increases with the growing initial pressure. The increasing air preheating temperature was capable of switching the reaction of R248 NH2 + OH<=>NH + H2O in the CH4/NH3/Air flame from an inhibiting reaction to a promoting reaction, while decreasing the sensitivity coefficient of inhibiting the forward reaction R10 O + CH3<=>H + CH2O, R88 OH + HO2<=>O2 + H2O, and R271 H + NO + M<=>HNO + M. Thus, the inhibition effect of flame extinction was weakened, and the positive progress of combustion was promoted. [ABSTRACT FROM AUTHOR]

This study unveils a novel concept of symmetric protonic ceramic fuel cells (symm‐PCFCs) with the introduction of a self‐recoverable electrode design, employing the innovative material BaCo0.4Fe0.4Zr0.1Y0.1O3‐δ (BCFZY). This research marks a significant milestone as it demonstrates the bi‐functional electrocatalytic activity of BCFZY for the first time. Utilizing density functional theory simulations, the molecular orbital interactions and defect chemistry of BCFZY are explored, uncovering its unique capability for the reversible exsolution and dissolution of Co‐Fe nanoparticles under redox conditions. This feature is pivotal in promoting both hydrogen oxidation and oxygen reduction reactions. Leveraging this insight, a cell is fabricated exhibiting high electrocatalytic activity and fuel flexibility as evidenced by the peak power densities of ≈350, 287, and 221 mW cm−2 (at 600 °C) with hydrogen, methanol, and methane as fuels, respectively. Experiments also show that the reversible exsolution/dissolution mitigates performance degradation, enabling prolonged operational life through self‐recovery. This approach paves the way for novel, advanced, durable, and commercially viable symm‐PCFCs. [ABSTRACT FROM AUTHOR]

The list of standard abbreviations for JDS is available at adsa.org/jds-abbreviations-24. Nonstandard abbreviations are available in the Notes. Greenhouse gas emission from the activities of all productive sectors is currently a topic of foremost importance. The major contributors in the livestock sector are ruminants, especially dairy cows. This study aimed to evaluate and compare 21 equations for predicting enteric methane emissions (EME) developed on the basis of milk traits and fatty acid profiles, which were selected from 46 retrieved through a literature review. We compiled a reference database of the detailed fatty acid profiles, determined by GC, of 992 lactating cows from 85 herds under 4 different dairy management systems. The cows were classified according to DIM, parity order, and dairy system. This database was the basis on which we estimated EME using the selected equations. The EME traits estimated were methane yield (20.63 ± 2.26 g/kg DMI, 7 equations), methane intensity (16.05 ± 2.76 g/kg of corrected milk, 4 equations), and daily methane production (385.4 ± 68.2 g/d, 10 equations). Methane production was also indirectly calculated by multiplying the daily corrected milk yield by the methane intensity (416.6 ± 134.7 g/d, 4 equations). We also tested for the effects of DIM, parity, and dairy system (as a correction factor) on the estimates. In general, we observed little consistency among the EME estimates obtained from the different equations, with exception of those obtained from meta-analyses of a range of data from different research centers. We found all the EME predictions to be highly affected by the sources of variation included in the statistical model: DIM significantly affected the results of 19 of the 21 equations, and parity order influenced the results of 13. Different patterns were observed for different equations with only some of them in accordance with expectations based on the cow's physiology. Finally, the best predictions of daily methane production were obtained when a measure of milk yield was included in the equation or when the estimate was indirectly calculated from daily milk yield and methane intensity. [ABSTRACT FROM AUTHOR]

The list of standard abbreviations for JDS is available at adsa.org/jds-abbreviations-24. Nonstandard abbreviations are available in the Notes. Dietary methane (CH 4) mitigation is in some cases associated with an increased hydrogen (H 2) emission. The objective of the present study was to investigate the acute and short-term effects of acceptors for H 2 (fumaric acid, acrylic acid, or phloroglucinol) supplemented via pulse-dosing to dairy cows fed CH 4 mitigating diets (using nitrate or 3-nitrooxypropanol), on gas exchange, rumen gas, and VFA composition. For this purpose, 2 individual 4 × 4 Latin square experiments were conducted with 4 periods of 3 d (nitrate supplementation) and 7 d (3-nitrooxypropanol supplementation), respectively. In each study, 4 rumen-cannulated Danish Holstein cows were used. Each additive for CH 4 mitigation was included in the ad libitum–fed diet within the 2 experiments (exp. 1 and exp. 2), to which the cows were adapted for at least 14 d. Acceptors for H 2 were administered twice daily in equal portions through the rumen fistula immediately after feeding of the individual cow. In exp. 1 (nitrate), the treatments were CON-1 (no H 2 -acceptor), FUM-1 (fumaric acid), ACR-1 (acrylic acid), and FUM+ACR-1 (50% FUM-1 + 50% ACR-1). In exp. 2 (3-nitrooxypropanol), the 3 treatments, CON-2, FUM-2, and ACR-2, were similar to CON-1, FUM-1 and ACR-1 treatments, however the fourth treatment was PHL-2 (phloroglucinol). Gas exchanges were measured in respiration chambers, and samples of rumen liquid and headspace gas were taken in time series relative to feeding and dosing on specific days. Headspace gas was analyzed for gas composition, and rumen liquid was analyzed for VFA composition and dissolved gas concentrations. Headspace gas composition and dissolved gas concentration were only measured in exp. 2. Dry matter intake was reduced upon acrylic acid supplementation. There were no significant effects of any treatments in any experiments on H 2 emission, except for a decrease in hourly H 2 emission rate (g/h) at 1 h after feeding in both experiments. In exp. 2, H 2 headspace proportions increased with ACR-2 supplementation, whereas dissolved concentrations were unaffected. In exp. 1, cows on ACR-1 increased propionate proportion at 1 h after feeding. In exp. 2, both FUM-2 and ACR-2 increased rumen propionate proportion in the hours after feeding and dosing. There was no effect on rumen acetate for cows on PHL-2. There was a strong positive correlation between rumen dissolved CH 4 and headspace CH 4 (r = 0.84), whereas the equivalent correlation was weaker for H 2 (r = 0.41). For the relationship between dissolved concentrations and emissions of CH 4 and H 2 , there was a moderate positive correlation for CH 4 (r = 0.54), whereas it was weak for H 2 (r = 0.28) with zero slope. In conclusion, the results suggested that fumaric acid and acrylic acid to some extent was reduced to propionate without associative effects on measures for H 2 redirection. Furthermore, phloroglucinol seemed not to be metabolized in the rumen in the present study, because no effects on rumen acetate or measures of H 2 were observed. Changes in H 2 headspace and emission may be a poor proxy for actual changes in the rumen fluid concentration of H 2. [ABSTRACT FROM AUTHOR]

The present work utilizes a response surface optimization technique to optimize hydrogen-rich syngas production through the process of methane dry reforming (DRM). This optimization is achieved by employing a bimetallic Mn–Ni/La 2 O 3 catalyst. The study aimed to evaluate the impact of three key parameters, namely reaction temperature, time on stream (TOS), and gas hourly space velocity (GHSV), on the hydrogen to carbon monoxide (H 2 /CO) ratio in syngas during the DRM. The Mn–Ni/La 2 O 3 catalyst, synthesized using the sequential wet impregnation technique, exhibited suitable physicochemical properties necessary for DRM reaction, as evidenced by the obtained characterization data. Among the five models examined, it was found that the quadratic versus 2FI model substantially fit the experimental data, as evidenced by a p-value <0.05. The analysis of variance (ANOVA) conducted on the quadratic response surface model compared to the 2FI model demonstrated that both the reaction temperature and the TOS had a significant impact on the H 2 /CO ratio in the syngas. The only significant interaction factor was the relationship between the reaction temperature and the TOS. Under the specified optimal circumstances of 15 000 ml/g.h, 850 °C, and 258.15 min, an H 2 /CO ratio of 0.98 was achieved. The resulting H 2 /CO ratio of 0.98 is almost 1, indicating its suitability as a feedstock for methanol production in the Fischer-Tropsch synthesis (FTS). • The Mn–Ni/La 2 O 3 catalyst exhibited suitable properties necessary for DRM reaction. • Temperature and time had a substantial impact on the H 2 /CO ratio in the syngas. • The response surface quadratic model is statistically significant to fit the experimental data. • At optimized conditions H 2 /CO ratio of 0.98 was obtained for the syngas. [ABSTRACT FROM AUTHOR]

Due to tectonic uplift in the Cenozoic and numerous shelf-wide glaciations during the Quaternary, -1-2.5 km of sedimentary overburden has been eroded from the Barents Sea shelf, leading to the exhumation and partial uncapping of hydrocarbon accumulations. Widespread natural gas and oil leakage from the glacially eroded middle-upper Triassic reservoir directly into the water column has been documented at the Sentralbanken high in the northern Norwegian Barents Sea. However, it remains unclear whether the hydrocarbon leakage occurs only from the middle-upper Triassic reservoir units in geological settings exceptionally conducive to hydrocarbon leakage, or if other reservoir formations contributed to the release of hydrocarbons into the water column. It is also not clear whether complete erosion of the caprock is a prerequisite for widespread liberation of natural gas and oil from glacially eroded reservoirs across Arctic continental shelves. Here we analyze multibeam echosounder data covering -5,000 km2 and a suite of high-resolution P-cable seismic lines from a range of geological structures across the northern Norwegian Barents Sea. Our analyses reveal that -21,700 natural gas seeps originate from exhumed, faulted and variably eroded structural highs bearing a range of Mesozoic reservoir formations. All investigated structural highs fuel seabed methane release hotspots with no exception. Evident from observations of seismic anomalies, fluid accumulations are pervasive in the subsurface and likely to continue fuelling seabed gas seepage into the future. We also document that gas seepage through faults piercing overburden, caprocks and reaching potential reservoir levels is pervasive at all investigated structural highs. On the Storbanken high and the Kong Karl platform, such fault-controlled seepage is more prevalent than seepage from reservoir formations subcropping below the seafloor. Using a simple parametrization approach, we estimate that seeps identified within our multibeam data coverage produce a seabed methane flux of 61 x 107 mol/yr (9,803 ton/yr), which is one to two orders of magnitude higher than other globally known submarine methane seepage provinces. Fluxes of methane from sea water to the air above the thermogenic gas seep provinces in the northern Norwegian Barents Sea remain to be determined. [ABSTRACT FROM AUTHOR]

Waste glycerol is produced in excess by several industries, such as during biodiesel production. In this work, the metabolic versatility of anaerobic sludge was explored towards waste glycerol valorization. By applying different environmental (methanogenic and sulfate-reducing) conditions, three distinct microbial cultures were obtained from the same inoculum (anaerobic granular sludge), with high microbial specialization, within three different phyla (Thermodesulfobacteriota, Euryarchaeota and Pseudomonadota). The cultures are capable of glycerol conversion through different pathways: (i) glycerol conversion to methane by a bacterium closely related to Solidesulfovibrio alcoholivorans (99.8% 16S rRNA gene identity), in syntrophic relationship with Methanofollis liminatans (98.8% identity), (ii) fermentation to propionate by Propionivibrio pelophilus strain asp66 (98.6% identity), with a propionate yield of 0.88 mmol mmol−1 (0.71 mg mg−1) and a propionate purity of 80–97% and (iii) acetate production coupled to sulfate reduction by Desulfolutivibrio sulfoxidireducens (98.3% identity). In conclusion, starting from the same inoculum, we could drive the metabolic and functional potential of the microbiota towards the formation of several valuable products that can be used in industrial applications or as energy carriers. Key points: Versatility of anaerobic cultures was explored for waste glycerol valorization Different environmental conditions lead to metabolic specialization Biocommodities such as propionate, acetate and methane were produced [ABSTRACT FROM AUTHOR]

Concentrating organic matter in sludge and converting it into methane through anaerobic bioconversion can improve resource recovery from domestic wastewater. Enhanced membrane coagulation (EMC) is highly efficient at concentrating organic matter, but residual coagulants (aluminum salts) can obstruct bioconversion by blocking microbial access. Limited research exists on evaluating EMC sludge bioconversion performance and addressing coagulant inhibition. This study proposes alkaline pre-fermentation to break down HO-Al-P backbones in coagulated sludge flocs, thereby improving hydrolysis and organic acid production for anaerobic digestion. Among the tested alkaline conditions (pH 9, pH 10, pH 11), pre-fermentation at pH 11 released the most organic matter (4710.0 mg/L SCOD), 20.4 times higher than without alkaline treatment. At pH 11, phosphate (61 mg/L PO43−–P) and organic acid production (2728.1 mg COD/L, with nearly 50% acetic acid) peaked, resulting in superior volatile solids removal (65.2%) and methane production (185.8 mL/g VS) during anaerobic digestion. Alkaline pre-fermentation favored alkali-tolerant bacteria such as Firmicutes and Actinobacteria, especially at pH 11, while neutrophilic Proteobacteria were suppressed. Trichococcus and Bifidobacterium, known acid producers, dominated under all conditions, with their abundance increasing at higher pH levels. Anaerobic digestion enriched fermentative bacteria like Chloroflexi and Synergistota (e.g., Thermovirga), especially in high pH reactors. Methanothrix, an acetoclastic methanogen, became the dominant methanogenic archaeon, indicating that methane production from EMC sludge primarily followed the acetoclastic methanogenesis pathway. Our findings demonstrate that alkaline pre-fermentation at pH 11 significantly enhances the hydrolysis efficiency of EMC sludge for methane recovery. [ABSTRACT FROM AUTHOR]

Solar-driven CO2 reduction to yield high-value chemicals presents an appealing avenue for combating climate change, yet achieving selective production of specific products remains a significant challenge. We showcase two osmium complexes, przpOs, and trzpOs, as CO2 reduction catalysts for selective CO2-to-methane conversion. Kinetically, the przpOs and trzpOs exhibit high CO2 reduction catalytic rate constants of 0.544 and 6.41 s−1, respectively. Under AM1.5 G irradiation, the optimal Si/TiO2/trzpOs have CH4 as the main product and >90% Faradaic efficiency, reaching −14.11 mA cm−2 photocurrent density at 0.0 VRHE. Density functional theory calculations reveal that the N atoms on the bipyrazole and triazole ligands effectively stabilize the CO2-adduct intermediates, which tend to be further hydrogenated to produce CH4, leading to their ultrahigh CO2-to-CH4 selectivity. These results are comparable to cutting-edge Si-based photocathodes for CO2 reduction, revealing a vast research potential in employing molecular catalysts for the photoelectrochemical conversion of CO2 to methane. Solar-driven CO2 conversion to produce solar fuels is an attractive way to harness solar energy and reduce carbon emissions. Here, the authors report two osmium complexes as highly active and selective CO2 reduction catalysts for selective CO2-to-methane conversion on Si-based photocathodes. [ABSTRACT FROM AUTHOR]

Anaerobic digestion of waste activated sludge (WAS) was one of the directions of sludge treatment, but how to effectively improve the production of methane as a resource product of anaerobic digestion of sludge still needs further research. The study examined how the combination of potassium ferrate (PF) and thermal hydrolysis (TH) pretreatment affected methane production from sludge. The results demonstrated a positive synergistic effect on methane production with PF-TH pretreatment. Specifically, by employing a 0.05 g/g TSS (total suspended solids) PF in conjunction with TH at 80 °C for 30 min, the methane yield increased from 170.66 ± 0.92 to 232.73 ± 2.21 mL/g VSS (volatile suspended solids). The co-pretreatment of PF and TH has been substantiated by mechanism studies to effectively enhance the disintegration and biodegradability of sludge. Additionally, the variation of microbial community revealed an enrichment of active microorganisms associated with anaerobic digestion after treated with PF + TH, resulting in a total abundance increase from 11.87 to 20.45% in the PF + TH group. [ABSTRACT FROM AUTHOR]

Kinetic model development is integral for designing, redesigning, monitoring, and optimizing chemical processes. Of the various approaches used within this field, microkinetic modeling is a crucial tool that focuses on surface events to analyze overall and preferential reaction pathways. This work covers noticeable features of microkinetic modeling for three critical case studies: (i) ammonia to hydrogen, (ii) oxidative coupling of methane to chemicals, and (iii) carbon dioxide hydrogenation for methanol synthesis. We analyze how microkinetic modeling enables predicting and optimizing complex reaction networks, allowing the design of efficient and tailored catalysts with enhanced activity and selectivity. [ABSTRACT FROM AUTHOR]

Metal‐free boron‐based catalysts such as boron oxide (B2O3) and boron nitride (h‐BN) are promising catalysts for methane oxidation to HCHO and CO. The B2O3 catalyst contains various probable boron sites (B1 to B6), which may be responsible for methane oxidation. In this work, we utilized density functional theory to compare two relevant geometrically identical boron sites (B2 and B4) for their reactivities. The two sites are explored in‐detail for the conversion of methane to formaldehyde (M2F), carbon monoxide and carbon dioxide. The B4 site activates the methane C−H bond easily as compared to the B2 site. In M2F conversion, the rate‐determining step for the B2 site is the co‐activation of dioxygen and methane, whereas over the B4 site, formaldehyde formation is the rate‐determining step. The computationally‐determined RDS for the B4 site coincides well with the reported experiments. It is further revealed that this site also prefers the formation of CO over CO2, which is in‐line with the experiments in literature. It is also shown through orbital analysis that methanol formation does not occur during methane oxidation. We employed descriptors such as condensed Fukui functions and global electrophilicity index to chemically distinct these twin sites. [ABSTRACT FROM AUTHOR]

Metal‐free boron‐based catalysts such as boron oxide (B2O3) and boron nitride (h‐BN) are promising catalysts for methane oxidation to HCHO and CO. The B2O3 catalyst contains various probable boron sites (B1 to B6), which may be responsible for methane oxidation. In this work, we utilized density functional theory to compare two relevant geometrically identical boron sites (B2 and B4) for their reactivities. The two sites are explored in‐detail for the conversion of methane to formaldehyde (M2F), carbon monoxide and carbon dioxide. The B4 site activates the methane C−H bond easily as compared to the B2 site. In M2F conversion, the rate‐determining step for the B2 site is the co‐activation of dioxygen and methane, whereas over the B4 site, formaldehyde formation is the rate‐determining step. The computationally‐determined RDS for the B4 site coincides well with the reported experiments. It is further revealed that this site also prefers the formation of CO over CO2, which is in‐line with the experiments in literature. It is also shown through orbital analysis that methanol formation does not occur during methane oxidation. We employed descriptors such as condensed Fukui functions and global electrophilicity index to chemically distinct these twin sites. [ABSTRACT FROM AUTHOR]

The increasing discovery of underwater methane leakage underscores the importance of monitoring methane emissions for environmental protection. Underwater remote sensing of methane leakage is critical and meaningful to protect the environment. The construction of sensor arrays is recognized as the most effective technique to increase the accuracy and sensitivity of underwater remote sensing of methane leakage. With the aim of improving the reliability of underwater methane remote-sensing sensor arrays, in this work, a deep learning method, specifically an explainable sparse spatio-temporal transformer, is proposed for detecting the failures of the underwater methane remote-sensing sensor arrays. The data input into the explainable sparse block could decrease the time complexity and the computational complexity (O (n)). Spatio-temporal features are extracted on various time scales by a spatio-temporal block automatically. In order to implement the data-driven early warning system, the data-driven warning return mechanism contains a warning threshold that is associated with physically disturbing information. Results show that the explainable sparse spatio-temporal transformer improves the performance of the underwater methane remote-sensing sensor array. A balanced F score (F1 score) of the model is put forward, and the anomaly accuracy is 0.92, which is superior to other reconstructed models such as convolutional_autoencoder (CAE) (0.81) and long-short term memory_autoencoder (LSTM-AE) (0.66). [ABSTRACT FROM AUTHOR]

The conversion of lignite into biomethane is of great significance in the field of energy research. However, the yield of biomethane is low. To improve the biomethane yield from lignite, the effects of ultrafine grinding lignite on the biomethanation fermentation system were analyzed. The daily biomethane yield, total biomethane yield, pH, glucose concentration, and volatile fatty acid concentration of lignite were used to determine the optimum particle size of lignite. The results demonstrated that the total biomethane yield of the fermentation group with ultrafine grinding lignite was 14.69 mL·g−1 at a reaction temperature of 50°C and a biomethane fermentation time of 39 d. This was 36.91, 33.42, and 26.75% higher than that of the 40, 150, and 250 mesh lignite biomethane fermentation groups, respectively. The daily biomethane yield reached the peak of the ultrafine grinding lignite fermentation group 1.30 mL·g−1 on the second day, which was 1.96, 1.63, and 1.04 times higher than that of the 40, 150, and 250 mesh lignite fermentation systems, respectively. The research demonstrated that ultrafine grinding of lignite can effectively increase the biomethane yield. This provides an effective method for improving the yield of biomethane from lignite. [ABSTRACT FROM AUTHOR]

Explosion in the military zone emergency response plan includes the process of preparedness, risk reduction, and normalization of the emergency. A bomb blast causes human and financial losses to people. Therefore, to prepare and reduce the risk, it is necessary to simulate a bomb blast in a military zone. For this purpose, in this study, the risk of a bomb blast containing ethane, methane, and propane fuel was simulated by the Baker-Strehlow-Tang explosion method in the form of 3 scenarios. According to this method, at a distance of 6, 4.5, and 5 km from the place of ethane, methane, and propane bombs explosion, respectively, the amount of impulse caused by the explosion is reduced by 50%. According to these results, it is clear that the overpressure explosion of ethane, methane, and propane bombs in the military zone is not directly related to the distance from the site of the explosion. The pulse from the explosion of ethane, methane, and propane bombs occurs in one second and will be the same at all distances. [ABSTRACT FROM AUTHOR]

Zeolites are a promising support for Pd catalysts in lean methane (CH 4) combustion. Herein, three types of zeolites (H-MOR, H-ZSM-5 and H-Y) were selected to estimate their structural effects and deactivation mechanisms in CH 4 combustion. We show that variations in zeolite structure and surface acidity led to distinct changes in Pd states. Pd/H-MOR with external high-dispersing Pd nanoparticles exhibited the best apparent activity, with activation energy (E a) at 73 kJ/mol, while Pd/H-ZSM-5 displayed the highest turnover frequency (TOF) at 19.6 × 10−3 sec−1, presumably owing to its large particles with more step sites providing active sites in one particle for CH 4 activation. Pd/H-Y with dispersed PdO within pore channels and/or Pd2+ ions on ion-exchange sites yielded the lowest apparent activity and TOF. Furthermore, Pd/H-MOR and Pd/H-ZSM-5 were both stable under a dry condition, but introducing 3 vol.% H 2 O caused the CH 4 conversion rate on Pd/H-MOR drop from 100% to 63% and that on Pd/H-ZSM-5 decreased remarkably from 82% to 36%. The former was shown to originate from zeolite structural dealumination, and the latter principally owed to Pd aggregation and the loss of active PdO. [Display omitted] [ABSTRACT FROM AUTHOR]

With increasingly stringent emissions regulations, the trend toward using low-carbon fuels in internal combustion engines is unstoppable. Achieving higher rates of methane substitution is a crucial direction for future diesel-methane engines. However, the details of the combustion process involving the auto-ignition of micro pilot diesel fuel and ignition of methane main fuel to form premixed flames are still not clear. Therefore, the study employed visualization technique using a rapid compression machine and numerical study to analyze the process of igniting methane main fuel using various injection strategies for micro pilot diesel fuel. The results indicate that before the onset of the second diesel injection, a pale blue premixed flame had already formed within the cylinder, and the ignition delay of the second diesel injection was influenced by the presence of this premixed flame. The ignition delay of the diesel droplets from the second injection decreases gradually as SOI1 advances. Compared to the single injection strategy, the split injection strategy forms smaller high-temperature regions during the combustion process, thereby displaying a discernible trend toward reducing NOx emissions. Since the energy contribution of the second diesel injection is only 2%, the turbulence and diffusion flames formed by the second diesel injection have a relatively low impact on the propagation of the methane premixed flame. The flame front for single injection strategy is closer to the thickened flames region, suggesting a thicker flame surface due to the concentrated distribution of diesel. [ABSTRACT FROM AUTHOR]

The first part of the current study highlights the importance of developing a clean hydrogen supply chain (CHSC) in Iran to enhance energy security and contribute to global efforts towards sustainable energy transition. Depending on whether the focus is on domestic consumption or export of hydrogen, the study provides valuable insights into the prioritization of CHSC development pathways via multi-criteria decision-making tools (AHP, AHOP-TOPSIS, and AHP-VIKOR). The results show that for domestic hydrogen consumption (internal scenario), the best path of the supply chain includes blue hydrogen from steam methane reforming coupled with carbon capture and storage, H 2 -carriers (ammonia and methanol), natural gas grid for transportation and distribution, and industry sector as the end user. In the external scenario, however, the best path of the CHSC consists of green hydrogen production based on solar energy, and the other parts of the path include liquid hydrogen as the storage method, ship as the distribution and transportation, and industrial sector as the end user. By identifying the most suitable methods and technologies for each stage of the supply chain, this paper offers a comprehensive analysis that can guide decision-making in CHSC development. [ABSTRACT FROM AUTHOR]

Borgs are huge extrachromosomal elements (ECE) of anaerobic methane-consuming "Candidatus Methanoperedens" archaea. Here, we used nanopore sequencing to validate published complete genomes curated from short reads and to reconstruct new genomes. 13 complete and four near-complete linear genomes share 40 genes that define a largely syntenous genome backbone. We use these conserved genes to identify new Borgs from peatland soil and to delineate Borg phylogeny, revealing two major clades. Remarkably, Borg genes encoding nanowire-like electron-transferring cytochromes and cell surface proteins are more highly expressed than those of host Methanoperedens, indicating that Borgs augment the Methanoperedens activity in situ. We reconstructed the first complete 4.00 Mbp genome for a Methanoperedens that is inferred to be a Borg host and predicted its methylation motifs, which differ from pervasive TC and CC methylation motifs of the Borgs. Thus, methylation may enable Methanoperedens to distinguish their genomes from those of Borgs. Very high Borg to Methanoperedens ratios and structural predictions suggest that Borgs may be capable of encapsulation. The findings clearly define Borgs as a distinct class of ECE with shared genomic signatures, establish their diversification from a common ancestor with genetic inheritance, and raise the possibility of periodic existence outside of host cells. Borgs are huge extrachromosomal elements associated with anaerobic methane-consuming archaea. Here, the authors use nanopore sequencing to identify new Borgs from peatland soil and their hosts, uncover their DNA modifications and activities, and elucidate the evolutionary relationships of Borgs. [ABSTRACT FROM AUTHOR]

The new derivatives of bis(2‐methyl‐1H‐indol‐3‐yl)methane are synthesized by employing decanoic acid to boost aldehyde reactivity via electrophilic activation. The reactions entail combining 2‐methyl‐1H‐indole with various aromatic, aliphatic, and heterocyclic aldehydes at room temperature for 24 h. The newly synthesized compound 4‐(bis(2‐methyl‐1H‐indol‐3‐yl)methyl)‐3‐bromophenol f) has been characterized through 2D structure elucidation. Chemo selectivity and mono selectivity have been explored. [ABSTRACT FROM AUTHOR]

The diazotrophic cyanobacterium Trichodesmium has been recognized as a potentially significant contributor to aerobic methane generation via several mechanisms including the utilization of methylphophonate (MPn) as a source of phosphorus. Currently, there is no information about how environmental factors regulate methane production by Trichodesmium. Here, we grew Trichodesmium IMS101 at five temperatures ranging from 16 to 31°C, and found that its methane production rates increased with rising temperatures to peak (1.028 ± 0.040 nmol CH4 μmol POC−1 day−1) at 27°C, and then declined. Its specific growth rate changed from 0.03 ± 0.01 d−1 to 0.34 ± 0.02 d−1, with the optimal growth temperature identified between 27 and 31°C. Within the tested temperature range the Q10 for the methane production rate was 4.6 ± 0.7, indicating a high sensitivity to thermal changes. In parallel, the methane production rates showed robust positive correlations with the assimilation rates of carbon, nitrogen, and phosphorus, resulting in the methane production quotients (molar ratio of carbon, nitrogen, or phosphorus assimilated to methane produced) of 227–494 for carbon, 40–128 for nitrogen, and 1.8–3.4 for phosphorus within the tested temperature range. Based on the experimental data, we estimated that the methane released from Trichodesmium can offset about 1% of its CO2 mitigation effects. [ABSTRACT FROM AUTHOR]

Simple Summary: Our results revealed that the total gas production, CH4 production, and dry matter digestibility reduced significantly as 3NPA doses increased in both yak and cattle. In addition, the H2 accumulation increased significantly in the tubes cultured with 3NPA compared to the control in both yak and cattle. The dynamic profile of total volatile fatty acid (TVFA) production, acetate concentration, and propionate concentration in both yak and cattle at 12 and 24 h incubation was consistent, in which they decreased as 3NPA doses increased, while those for 48 and 72 h incubation were divergent between them. These data demonstrated that the effects of 3NPA on fermentation characteristics between yak and cattle were divergent, and these effects were dose-dependent, and 3NPA regarded as a potential additive to mitigate methane production; although, it inhibits the dry matter digestibility in vitro, which is beneficial to determine the effective and safe dose for use to improve animal productivity in vivo. 3-nitropropionic acid (3NPA) has been proposed as an useful modifier to mitigate ruminal enteric methane emissions. However, few studies investigated the effects of 3NPA on ruminal fermentation characteristics of grazing ruminants in vitro. Rumen fluid from grazing yak and cattle were collected and incubated with additions of 0, 8, and 16 mM 3NPA. The total gas production, CH4 production, and dry matter digestibility significantly decreased with increasing 3NPA doses in both ruminant species (p < 0.05) and methane production decreased to almost 100% in cattle at 8 mM NPA but not yak, while H2 accumulation showed an opposite trend. The total fatty acid (TVFA) production, acetate concentration, and propionate concentration in cattle decreased as 3NPA doses increased at 12 and 24 h incubation. For yak, the H2 accumulation reached its apex at 8 mM NPA (p < 0.05). The TVFA in yak decreased significantly with increasing 3NPA doses at 12 and 72 h incubation. Moreover, the acetate concentration and propionate concentration in yak decreased as 3NPA doses increased at 12 and 24 h incubation. Overall, these findings demonstrated that 3NPA could be used as a strategy to mitigate methane emissions; although, it negatively affected the dry matter degradability in vitro. [ABSTRACT FROM AUTHOR]

Efficiently converting methane into valuable chemicals via photocatalysis under mild condition represents a sustainable route to energy storage and value‐added manufacture. Despite continued interest in this area, the achievements have been overshadowed by the absence of standardized protocols for conducting photocatalytic methane oxidation experiments as well as evaluating the corresponding performance. In this review, we present a structured solution aimed at addressing these challenges. Firstly, we introduce the norms underlying reactor design and outline various configurations in the gas–solid and gas–solid–liquid reaction systems. This discussion helps choosing the suitable reactors for methane conversion experiments. Subsequently, we offer a comprehensive step‐by‐step protocol applicable to diverse methane‐conversion reactions. Emphasizing meticulous verification and accurate quantification of the products, this protocol highlights the significance of mitigating contamination sources and selecting appropriate detection methods. Lastly, we propose the standardized performance metrics crucial for evaluating photocatalytic methane conversion. By defining these metrics, the community could obtain the consensus of assessing the performance across different studies. Moving forward, the future of photocatalytic methane conversion necessitates further refinement of stringent experimental standards and evaluation criteria. Moreover, development of scalable reactor is essential to facilitate the transition from laboratory proof‐of‐concept to potentially industrial production. [ABSTRACT FROM AUTHOR]

Enhanced coalbed methane (ECBM) recovery by gas injection is regarded as a feasible method for ECBM recovery. To investigate the mechanism of CH4 displacement by N2 injection, a series of physical experiments were conducted in the laboratory under different N2 injection pressures. The experimental results showed a continuous increase in the N2 volume fraction and a decrease in the CH4 volume fraction with the N2 injection pressure. The CH4 displacement efficiency increases rapidly in the initial stage and then gradually stabilizes. Given the effect of matrix shrinkage and effective stress on coal permeability, a dynamic multi‐field coupling model of ECBM recovery by N2 injection (N2‐ECBM) was proposed in this work. Then, numerical simulations were implemented by the coupling model to analyze the key factors affecting coal permeability, N2 injection pressure and CH4 pressure during the N2–ECBM process. Furthermore, the Response Surface Methodology (RSM) was used to investigate the interactions of multiple factors, the results reveal that an increase in one factor would weaken the influence of another factor. In addition, a RSM regression model was obtained and verified by the experimental data, with a well‐fitting outcomes. Therefore, the RSM model can be used in practical engineering applications to optimize specific extraction parameters for ECBM recovery at minimum cost in a limited extraction period. [ABSTRACT FROM AUTHOR]

One strategy for utilizing ammonia as an energy vector is to replace conventional hydrocarbons with hydrogen-enriched ammonia in existing or retrofitted combustors. However, the strong differential diffusion effect of hydrogen can significantly alter the combustion properties and cause challenges in combustor operability. Therefore, this numerical study performs a systematic investigation on the effect of differential diffusion on fundamental combustion properties of ammonia/hydrogen fuel blends. The investigated combustion properties span from the initiation of combustion, i.e., ignition, to stretched flame propagation and ultimately to flame stabilization mechanisms. The objective is to evaluate the feasibility of hydrogen/ammonia/air mixtures as substitutes for methane/air particularly considering the implications of differential diffusion effects. To this end, four fuel blends with similar unstretched burning properties are selected: fuel lean ammonia/hydrogen (AH-L), fuel rich ammonia/hydrogen (AH-R), fuel lean methane (M-L) and fuel lean methane/hydrogen (MH-L). First, the forced ignition and stretched flame propagation are evaluated. It is found that the AH-L (AH-R) mixture has a large negative (positive) Markstein length, and thereby among the selected fuel blends, AH-L (AH-R) has the lowest (highest) minimum ignition energy. Then flame stabilization mechanisms are investigated. For a stable flame, AH-L (AH-R) has an intensified (weakened) flame base and a weak (strong) flame tip, which shows a higher flashback (blow-off) propensity. Based on the critical gradient theory, a novel stability regime diagram is proposed. With the regime diagram, the flame stabilization limits (central flashback, boundary layer flashback, stable, and blow-off) and flow conditions can be determined for burners of different sizes. [Display omitted] • Feasibility of H 2 /NH 3 as a substitute fuel for CH 4 was evaluated (4 blends with equal s L 0). • A systematic analysis on ignition, flame propagation and stabilization was performed. • The rich (lean) H 2 /NH 3 mixture is more difficult (easier) to ignite than CH 4 mixture. • The rich (lean) H 2 /NH 3 flame is more prone to blow-off (flashback) than CH 4 mixture. • A flame stability regime diagram based on critical gradient theory was proposed. [ABSTRACT FROM AUTHOR]

The integrated system of anaerobic digestion and microbial electrolysis cells (AD-MEC) was a novel approach to enhance the degradation of food waste anaerobic digestate and recover methane. Through long-term operation, the start-up method, organic loading, and methane production mechanism of the digestate have been investigated. At an organic loading rate of 4000 mg/L, AD-MEC increased methane production by 3–4 times and soluble chemical oxygen demand (SCOD) removal by 20.3% compared with anaerobic digestion (AD). The abundance of bacteria Fastidiosipila and Geobacter, which participated in the acid degradation and direct electron transfer in the AD-MEC, increased dramatically compared to that in the AD. The dominant methanogenic archaea in the AD-MEC and AD were Methanobacterium (44.4–56.3%) and Methanocalculus (70.05%), respectively. Geobacter and Methanobacterium were dominant in the AD-MEC by direct electron transfer of organic matter into synthetic methane intermediates. AD-MEC showed a perfect SCOD removal efficiency of the digestate, while methane as clean energy was obtained. Therefore, AD-MEC was a promising technology for deep energy transformation from digestate. [ABSTRACT FROM AUTHOR]

In the past, Cu‐oxo or ‐hydroxy clusters hosted in zeolites have been suggested to enable the selective conversion of methane to methanol, but the impact of the active site's stoichiometry and structure on methanol production is still poorly understood. Herein, we apply theoretical modeling in conjunction with experiments to study the impact of these two factors on partial methane oxidation in the Cu‐exchanged zeolite SSZ‐13. Phase diagrams developed from first‐principles suggest that Cu‐hydroxy or Cu‐oxo dimers are stabilized when O2 or N2O are used to activate the catalyst, respectively. We confirm these predictions experimentally and determine that in a stepwise conversion process, Cu‐oxo dimers can convert twice as much methane to methanol compared to Cu‐hydroxyl dimers. Our theoretical models rationalize how Cu‐di‐oxo dimers can convert up to two methane molecules to methanol, while Cu‐di‐hydroxyl dimers can convert only one methane molecule to methanol per catalytic cycle. These findings imply that in Cu clusters, at least one oxo group or two hydroxyl groups are needed to convert one methane molecule to methanol per cycle. This simple structure–activity relationship allows to intuitively understand the potential of small oxygenated or hydroxylated transition metal clusters to convert methane to methanol. [ABSTRACT FROM AUTHOR]

The axial acoustic characteristics of detonation sound waves generated by single and dual detonation tubes, utilizing methane as fuel and oxygen as oxidizers, are experimentally investigated. Various acoustic parameters are analyzed, including the effective sound pressure level, A duration, and energy characteristics. By the A duration, we mean the time when the sound pressure ascends to a significant maximum and then swiftly descends to the ambient pressure. Experimental results reveal that the decay rate of the effective sound pressure level gradually decreases with increasing distance, with ground reflection prolonging the A duration. The energy of the detonation sound wave is primarily concentrated in the low frequency, and the proportion of low-frequency energy increases with distance. For the dual detonation tubes, the detonation sound wave exhibits a higher effective sound pressure level and A duration compared to the single detonation tube. Although the energy proportion and wave structures of detonation sound waves generated by the dual detonation tubes are similar to those of the single detonation tube, the high-frequency energy experiences greater gain. The effective sound pressure level of the dual detonation tubes increases with the separation distance. Altering the ignition interval can transfer energy to lower frequencies, albeit slightly reducing the effective sound pressure level. These findings highlight the significant impact of the spacing between dual detonation tubes on the effective sound pressure level, and the potential for changing the ignition interval to modify the energy characteristics of the detonation sound wave. [ABSTRACT FROM AUTHOR]

Alkanes, single carbon methane to long‐chain hydrocarbons (e.g. hexadecane and tetradecane), are important carbon sources to anaerobic microbial communities. In anoxic environments, archaea are known to utilize and produce methane via the methyl‐coenzyme M reductase enzyme (MCR). Recent explorations of new environments, like deep sea sediments, that have coupled metagenomics and cultivation experiments revealed divergent MCRs, also referred to as alkyl‐coenzyme M reductases (ACRs) in archaea, with similar mechanisms as the C1 utilizing canonical MCR mechanism. These ACR enzymes have been shown to activate other alkanes such as ethane, propane and butane for subsequent degradation. The reversibility of canonical MCRs suggests that these non‐methane‐activating homologues (ACRs) might have similar reversibility, perhaps mediated by undiscovered lineages that produce alkanes under certain conditions. The discovery of these alternative alkane utilization pathways holds significant promise for a breadth of potential biotechnological applications in bioremediation, energy production and climate change mitigation. [ABSTRACT FROM AUTHOR]

The microbiomes play a key role in anaerobic digestion (AD) and perturbations caused by external factors like antibiotics may disturb the microbial community dynamics. This experimental investigation studied the effect of antibiotics tetracycline and spectinomycin individually and in combination at three different concentrations on the biogas, methane yield, and microbial dynamics of AD. In a limited 5 days, well-controlled, lab-scale, batch, mesophilic anaerobic digestion experiment, high concentration of spectinomycin impacted the AD process most negatively by yielding 55.13% less methane and 54.02% less biogas followed by 47.12% less methane and 38.31% less biogas in its medium concentration as compared to the control group. High concentration of combination of antibiotics least negatively impacted the biogas (12.52% decrease), and low concentration of tetracycline resulted in the least reduction of 15.17% in methane production. Flow cytometry fingerprinting has been explored as a rapid, high-throughput, objective, data-driven approach to monitor the day-to-day changes in microbial community fingerprints. Dissimilarity variations were observed from day 1 to 5 in autocorrelations data which putatively accounted for the changes in biogas production. This effective monitoring might help in improved AD operation with increased bioenergy yield and prevent the entry of antibiotics and other harmful pollutants into the food chain. [ABSTRACT FROM AUTHOR]

The atmospheric concentration of carbon dioxide is continuously rising mostly due to the consumption of fossil fuels. Renewable fuels, such as synthetic methane and methanol, for which production hydrogen and carbon dioxide are needed, have the potential to mitigate climate change by substituting fossil-based energy carriers. The core objective of this paper is to investigate the utilization of carbon dioxide from biomass-based processes for the production of synthetic methane and methanol, as well as to analyze their future prospects. Different scenarios including the most relevant impact parameters, such as possible learning rates or number of full load hours, are derived. Finally, the strengths, weaknesses, opportunities and threats of synthetic methane and methanol are compared with direct hydrogen utilization from an economic and technical point of view. In spite of the possible cost reductions due to technological learning and economies of scale, the production costs of synthetic methane and methanol will remain very high in the main scenario. Therefore, low electricity prices and a high number of full-load hours are key to enhance the economic viability. [ABSTRACT FROM AUTHOR]

A comprehensive understanding of the mechanical characteristics of deep coalbed methane reservoir rocks (DCMRR) is crucial for the safe and efficient development of deep coalbed gas resources. In this study, the microstructural and mechanical features of the coal seam roof, floor, and the coal seam itself were analyzed through laboratory experiments. The impact mechanisms of drilling fluid and fracturing fluid hydration on the mechanical properties and failure behavior of coal seam rocks were investigated. The experimental results indicate that the main minerals in coal seams are clay and amorphous substances, with kaolinite being the predominant clay mineral component in coal seam rocks. The rock of the coal seam roof and floor exhibits strong elasticity and high compressive strength, while the rock in the coal seam section shows a lower compressive capacity with pronounced plastic deformation characteristics. The content of kaolinite shows a good correlation with the mechanical properties of DCMRR. As the kaolinite content increases, the strength of DCMRR gradually decreases, and deformability enhances. After immersion in drilling fluid and slickwater, the strength of coal seam rocks significantly decreases, leading to shear fracture zones and localized strong damage features after rock compression failure. The analysis of the mechanical properties of DCMRR suggests that the horizontal well trajectory should be close to the coal seam roof, and strong sealing agents should be added to drilling fluid to reduce the risk of wellbore collapse. Enhancing the hydration of slickwater is beneficial for the formation of a more complex fracture network in deep coalbed methane reservoir. [ABSTRACT FROM AUTHOR]

Converting corn grains into bioethanol is an expanding practice for sustainable fuel production, but this is accompanied by the production of large quantities of by-products such as whole stillage. In the present study, the influence of advanced wet oxidation and steam explosion (AWOEx) pretreatment on biogas production and lignocellulose decomposition of corn whole stillage (CWS) was evaluated using semi-continuous thermophilic reactors. The digestion of the CWS was shown to be feasible with an organic loading rate (OLR) of 1.12 ± 0.03 kg VS/m3 day and a hydraulic retention time (HRT) of 30 days, achieving a methane yield of 0.75 ± 0.05 L CH4/g VSfed for untreated stillage and 0.86 ± 0.04 L CH4/g VSfed for pretreated stillage, corresponding with an increase in methane yield of about 15%. However, the reactors showed unstable performance with the highest investigated OLRs and shortest HRTs. Under optimal conditions, the conversion efficiencies of COD, cellulose, hemicellulose, and lignin were 88, 95, 97, and 59% for pretreated CWS, and 86, 94, 95, and 51% for untreated CWS, respectively. Microbial community analysis showed that Proteiniphilum, MBA03, and Acetomicrobium were the dominant genera in the digestate and were likely responsible for the conversion of proteins and volatile fatty acids in CWS. [ABSTRACT FROM AUTHOR]

The article discusses a special issue on the sustainable development of food waste biorefineries. The issue includes research papers covering various aspects of biorefinery processes, such as fermentation, sustainability assessment, and the production of valuable bioproducts from food waste. The papers highlight the benefits of biorefineries in reducing food waste, conserving natural resources, and promoting sustainable behaviors. However, there are challenges in terms of technological development, biomass supply, and economic competitiveness. The authors express their appreciation to the contributing authors for their valuable work and identify research gaps in the field. [Extracted from the article]

This study aimed to evaluate the effects of dietary supplementation with 3-nitrooxypropanol (3-NOP) on growth performance, ruminal fermentation, and enteric methane emissions of beef cattle using a meta-analytic approach. The final meta-analysis database included results from 15 scientific articles. The response variables were analyzed through random effects models, where the results were reported as weighted mean differences (WMD) between the treatments without 3-NOP and those supplemented with 3-NOP. The dietary inclusion of 3-NOP decreased (p < 0.001) dry matter intake but did not affect (p > 0.05) average daily gain and increased (p < 0.05) feed efficiency. In the rumen, 3-NOP supplementation increased (p < 0.01) the pH and ruminal concentration of propionate, butyrate, valerate, isobutyrate, and isovalerate. In contrast, dietary supplementation with 3-NOP decreased (p < 0.001) the rumen concentration of ammonia nitrogen, total volatile fatty acids, acetate, and the acetate/propionate ratio. Furthermore, daily methane (CH4) emission, CH4 yield, and CH4 emission as a percentage of gross energy ingested decreased (p < 0.001) in response to 3-NOP dietary supplementation. In conclusion, dietary supplementation with 3-nitrooxypropanol can be used as a nutritional strategy to improve feed efficiency and ruminal fermentation in beef cattle and, at the same time, reduce enteric methane emissions. [ABSTRACT FROM AUTHOR]

The current trends converge towards minimizing the carbon footprint on the environment in the operation of all thermal equipment and need finding alternative solutions compared to what the market offers at the moment. Utilizing hydrogen in combustible mixtures with methane gas to fuel condensing boilers is one solution. The benefit is that it reduces carbon dioxide emissions into the atmosphere as only water vapor is produced when hydrogen undergoes combustion. The effects of adding hydrogen at percentages of 23%, 30%, 35% and 45%, respectively, to the combustible gas mixture are examined in the paper. [ABSTRACT FROM AUTHOR]