Methane Release Research Articles

Methane release and energy evolution in coal and its implication for gas outburst

Gas outburst is a common underground geological hazard that poses a serious threat to coal mine safety production. To elucidate the influence of methane release behavior and energy evolution on gas outburst in coal, the microscopic pore parameters and macroscopic methane release law of six coal rank samples were studied by full-scale pore test, Scanning electron microscopy-Pores and Cracks Analysis System analysis and temperature measurement experiments during methane desorption. The results show that with the increase in coal rank, pore complexity, and the chaos of pore direction distribution first decrease and then increase. The pore volume and pore area of low/high-rank samples are relatively large, with well-developed pores, especially micropores, which are prone to gas accumulation and have great potential for outburst. The evolution of methane desorption-diffusion performance with coal rank is corresponding to pore development degree, methane in high rank coal is rapidly transferred at a high diffusion rate. The desorption prediction model related to temperature change can accurately characterize the relationship between temperature variation and desorption amount in the process of methane desorption. With the increase in coal rank, the desorption heat value and gas expansion energy of samples show a U-shaped trend of decreasing first and then increasing. In high-rank coal seams, large methane potential energy accumulates, posing considerable outburst potential and threats. The research findings can provide certain guidance for the prediction and forecasting of gas outburst disasters.

Methane emission from the Pregolya River Estuary (Baltic Sea)

Measurements of dissolved methane were performed in a sequentially connected system of water bodies that form the Pregolya River Estuary: Pregolya River – Kaliningrad Sea Canal – Vistula and Curonian Lagoons – Baltic Straight – Baltic Sea. Methane concentrations were detected on a gas chromatograph with a flame ionization detector, and the fluxes were calculated using a boundary layer gas transfer model. During a study period between 2016 and 2022, the Pregolya River is characterized by the high range of methane concentrations, reaching 8838 nmol/L in the annual maximum in May. This could be result of the “cumulative effect” of the contact of fresh and brackish waters and the inhibition of river flow during the surge events, probably, in combination with episodic release of methane from the bottom sediments. The estuary water was constantly oversaturated in methane, thus, emission from water into the atmosphere reached 1018 μmol/m2/day. The study area was notable source of methane to the atmosphere. In spring and in summer, subsurface maximums in methane were observed in the gas-saturated mud area on the Gdansk Deep slope, which did not seem to be related to the spreading of methane-reach water from the Baltic Straight.

Dynamic soil columns simulate Arctic redox biogeochemistry and carbon release during changes in water saturation

Thawing Arctic permafrost can induce hydrologic change and alter redox conditions, shifting the balance of soil organic matter (SOM) decomposition. There remains uncertainty about how soil saturation and redox transitions impact dissolved and gas phase carbon fluxes, and efforts to link hydrobiogeochemical processes to ecosystem-scale models are limited. This study evaluates SOM decomposition of Arctic tundra soils using column experiments, water chemistry measurements, microbial community analysis, and a PFLOTRAN reactive transport model. Soil columns from a thermokarst channel (TC) and an upland tundra (UC) were exposed to cycles of saturation and drainage, which controlled carbon emissions. During saturation, an outflow of dissolved organic carbon from the UC soil correlated with elevated reduced iron and decreased pH; during drainage, UC carbon dioxide fluxes were 70% higher than TC fluxes. Intermittent methane release was observed for TC, consistent with higher methanogen abundance. Slower drainage in the TC soil correlated with more subtle biogeochemical changes. PFLOTRAN simulations captured experimental trends in soil carbon fluxes, oxygen concentrations, and water contents. The model was then used to evaluate additional soil water drainage rates. This study emphasizes the importance of considering hydrologic change when evaluating and simulating SOM decomposition in dynamic Arctic tundra environments.

Methane emission mitigation of Paenibacillus yonginensis DCY84T incorporated with silicate on paddy rice (Oryzae sativa L.) plantation revealed in soil microbiome profiling.

Anthropogenic methane emissions from paddy cultivation contribute to greenhouse gas levels owing to the anaerobic conditions in flooded rice fields, which promotes the activity of methanogenic bacteria. This study explored bioremediation strategies to mitigate methane release through the application of plant growth-promoting rhizobacteria combined with silicate in rice cultivation. Rice seeds were coated with Paenibacillus yonginensis DCY84T, with and without the addition of silicate, prior to sowing. Results revealed notable reduction in methane flux during the peak growth stage of rice in seeds treated with DCY84T (27.215±1.975mgm-2h-1), with a further reduction observed when silicate was also applied (23.592±3.112mgm-2h-1), compared to untreated seeds (37.305±2.990mgm-2h-1). Additionally, treatment with DCY84T (28.24±0.55g) resulted in an increase in rice yield (p<0.05), as evidenced by a greater 1000-grain weight compared to both the control group (26.91±0.09g) and the application of silicate (27.37±0.57g). The beta diversity of the soil microbial community highlighted distinct differences between the treated and control groups, indicating DCY84T inoculation with or without silicate altered the soil microbial structure. Particularly, the treated groups showed dominance of the phylum Proteobacteria, especially the classes Alphaproteobacteria and Deltaproteobacteria. Furthermore, the addition of silicate to DCY84T-coated rice seeds resulted in a higher abundance of bacterial families, such as Anaerolinaceae, Clostridiceae, and Nitrospirae which compete with methanogens for organic substrates, thereby reducing their methane production. Notably, the DCY84T-silicate treatment group showed higher levels of methane metabolism biomarkers such as formate dehydrogenase within the soil microbiome, which correlated with the observed reduction in methane emissions. These findings suggest that coating rice seeds with DCY84T and silicate prior to sowing effectively mediates methane production and release during rice cultivation by promoting beneficial soil bacterial communities.

Methane emission fluxes and associated microbial community characteristics in a temperate seagrass meadow.

Seagrass meadows are acknowledged as blue carbon ecosystems, yet they are also ideal habitats for methane (CH4) release, offsetting their ability to mitigate climate change. The global CH4 fluxes in seagrass meadows remain highly uncertain due to regional and species biases, and the microbial mechanisms driving methane release are poorly understood. Here, we investigated CH4 air-sea fluxes, sediment CH4 emission potential and microbes involved in CH4 release using geochemical techniques combined with qPCR and Illumina sequencing in a temperate Zostera japonica and Zostera marina mixed meadow. The CH4 air-sea fluxes fluctuated from -0.42 to 11.42μmol·m-2·d-1, showing a strong seasonal variation. CH4 emission potential was significantly higher in seagrass vegetated sediments (10.34±2.72nmol·g-1·d-1) than in the adjacent bare sediments (1.55±1.15nmol·g-1·d-1), primarily attributed to variations in sediment organic matter content. Diverse methanogens occurred in the seagrass meadow, with Methanolobus dominating in seagrass sediments, while Methanococcoides, Methanosarcina, and Methanoculleus being prevalent in bare sediments. Meanwhile, a variety of methylotrophic groups were detected, including aerobic Gammaproteobacteria, anaerobic Desulfobacterota and Methylomirabilota, as well as archaea Candidatus Methanoperedens. The co-occurrence of these functional groups implied the presence of complex CH4 production and oxidation pathways, which regulated the CH4 budget in the seagrass ecosystems. Taken together, our findings enhance the comprehension of the methane emission process and driving mechanism in seagrass ecosystems.

Assessing the sustainable development in the European Union: influence of municipal waste, industrial waste, and waste related patents.

Waste has emerged as a pressing concern for the environment, primarily stemming from the processes of urbanization and industrialization. The substantial volumes of waste generated pose a serious threat to the environment, as they spread out harmful substances in the soil and release methane emissions into the atmosphere. To effectively address this issue, this study explores the impact of municipal and industrial waste, as well as waste-related innovation on the load capacity factor (LCF) from 2005 to 2020. For this purpose, the augmented mean group method and the half panel jackknife causality approach were conducted by using panel data from 17 European countries. The empirical findings show that (1) the load capacity curve (LCC) hypothesis is confirmed; (2) municipal and industrial waste have a detrimental effect on the LCF; and (3) innovation in waste management practices have no discernible impact on the LCF. In light of these findings, this study emphasizes the importance of efficient waste management for European countries to exploit the potential of waste as a valuable resource rather than a cause of pollution.

Using Ground‐Penetrating Radar to Infer Ice Wedge Characteristics Proximal to Water Tracks

AbstractMassive ground ice in Arctic regions underlain using continuous permafrost influences hydrologic processes, leading to ground subsidence and the release of carbon dioxide and methane into the atmosphere. The relation of massive ground ice such as ice wedges to water tracks and seasonally saturated hydrologic pathways remains uncertain. Here, we examine the location of ice wedges along a water track on the North Slope of Alaska using Ground‐Penetrating Radar (GPR) surveys, in situ measurements, soil cores, and forward modeling. Of nine unique GPR surveys collected in the summers of 2022 and 2023, seven exhibit distinctive “X”‐shaped reflections above columnar reflectors that are spatially correlated with water track margins. Forward modeling of plausible geometries suggests that ice wedges produce reflection patterns most similar to the reflections observed in our GPR profiles. Additionally, a large magnitude (∼71 mm) rain event on 8 July 2023 led to a ground collapse that exposed four ice wedges on the margin of the studied water track, ∼100 m downstream of our GPR surveys. Together, this suggests that GPR is a viable method for identifying the location of ice wedges as air temperatures in the Arctic continue to increase, we expect that ice wedges may thaw, destabilizing water tracks and causing ground collapse and expansion of thermo‐erosional gullies. This ground collapse will increase greenhouse gas emissions and threaten the Arctic infrastructure. Future geophysical analysis of upland Arctic hillslopes should include additional water tracks to better characterize potential heterogeneity in permafrost vulnerability across the warming Arctic.

Diversity and Distribution of Methane Functional Microorganisms in Sedimentary Columns of Hongfeng Reservoir in Different Seasons.

Freshwater ecosystem is a significant natural source of CH4 emission in the atmosphere. To fully understand the dynamics of methane emissions in reservoirs, it is essential to grasp the temporal and vertical distribution patterns, as well as the factors that influence the methanogenic bacterial communities within the sediments. This study investigates the methane dynamics, carbon isotope fractionation (δ13CH4), and abundance of functional microorganisms along the geochemical gradient in the in situ sedimentary column of Hongfeng Reservoir (China). Notably, the methane concentration in sediment in summer ranged in 15.39-127.22µmol/L, which is twice as high as wintertime concentrations in the surface layer near the sediment-water interface (0-10cm depth). Illumina sequencing of the sediments identified 11 genera affiliated with methanogenic archaea, with dominant genus Methanosaeta reaching a relative abundance of 34.95% in summer. The total carbon (TOC) content in sedimentary columns in different seasons is positively correlated with Methanosarcina (P < 0.05). In addition, seasonal discrepancies are observed in the sediment profiles for total nitrogen (TN), sulfate (SO42-), and ferrous iron (Fe2+) concentrations. The concentration of total nitrogen (TN) is higher in summer than in winter. In summer, sulfate accumulates in the middle layer of the sedimentary column, while in winter, the maximum concentration of sulfate in the surface layer reaches 0.65mmol/L. These geochemical gradients drive the biological transformation of nitrogen, sulfur, and iron, may also be linked to the consumption of methane. Thus, it is established that the temporal and spatial dynamics of methanogenic communities in sediments significantly influence the fluctuations in methane release fluxes within reservoirs, highlighting the necessity to account for seasonal biological variations when assessing greenhouse gas emissions from reservoirs.

Composition and in situ structure of the Methanospirillum hungatei cell envelope and surface layer.

Archaea share genomic similarities with Eukarya and cellular architectural similarities with Bacteria, though archaeal and bacterial surface layers (S-layers) differ. Using cellular cryo-electron tomography, we visualized the S-layer lattice surrounding Methanospirillum hungatei, a methanogenic archaeon. Though more compact than known structures, M. hungatei's S-layer is a flexible hexagonal lattice of dome-shaped tiles, uniformly spaced from both the overlying cell sheath and the underlying cell membrane. Subtomogram averaging resolved the S-layer hexamer tile at 6.4-angstrom resolution. By fitting an AlphaFold model into hexamer tiles in flat and curved conformations, we uncover intra- and intertile interactions that contribute to the S-layer's cylindrical and flexible architecture, along with a spacer extension for cell membrane attachment. M. hungatei cell's end plug structure, likely composed of S-layer isoforms, further highlights the uniqueness of this archaeal cell. These structural features offer advantages for methane release and reflect divergent evolutionary adaptations to environmental pressures during early microbial emergence.

The Main Geohazards in the Russian Sector of the Arctic Ocean

The Arctic region, including vast shelf zones, has enormous resource and transport potential and is currently key to Russia’s strategic development. This region is promising and attractive for the intensification of global economic activity. When developing this region, it is very important to avoid emergency situations that could result in numerous negative environmental and socio-economic consequences. Therefore, when designing and constructing critical infrastructure facilities in the Arctic, it is necessary to conduct high-quality studies of potential geohazards. This paper reviews and summarizes the scattered information on the main geohazards in the Russian sector of the Arctic Ocean, such as earthquakes, underwater landslides, tsunamis, and focused fluid discharges (gas seeps), and discusses patterns of their spatial distribution and possible relationships with the geodynamic setting of the Arctic region. The study revealed that the main patterns of the mutual distribution of the main geohazards of the Russian sector of the Arctic seas are determined by both the modern geodynamic situation in the region and the history of the geodynamic evolution of the Arctic, namely the formation of the spreading axis and deep-sea basins of the Arctic Ocean. The high probability of the influence of seismotectonic activity on the state of subsea permafrost and massive methane release is emphasized. This review contributes toward better understanding and progress in the zoning of seismic and other geological hazards in the vast Arctic seas of Russia.

New insights into methane storage through coal pore opening and closure mechanisms during transient supercritical CO2 fracturing

This study focuses on the often-overlooked closed pores in coal, which play a crucial role in isolating and storing significant amounts of methane, thereby directly impacting the efficiency of methane extraction. Using low-temperature nitrogen adsorption (LP-N2A) and small-angle x-ray scattering (SAXS) combined with multifractal theory, we examined the dynamics of pore opening and closure during supercritical CO2 (SC-CO2) fracturing at various pressures. Initially, chemical dissolution and the extraction of small organic molecules increased the surface area and volume of open pores. Stress-induced pore opening reduced closed pore volume, potentially increasing methane release. Enhanced fractal dimensions indicated greater pore heterogeneity. As fracturing progressed, pore interconnectivity improved, facilitating methane migration. Matrix contraction slightly expanded closed pores, increasing closed porosity. Fractal parameter decreases reflected changes in pore-scale correlation and reduced density. The isolation effect of closed pores delayed stress transmission, leading to asynchronous responses between total and open pores. Later, larger open pores collapsed, fragmenting the coal and increasing pore volume and surface area, while new closed pores raised closed porosity. These findings offer insights into how pore structure evolution during fracturing regulates methane at the micropore level.

High-resolution dynamic characteristics of thermal wave in porous media burners with low-concentration methane

Thermal flow reverse reactor can realize stable oxidation and heat release of low-concentration coal mine methane, while the dynamic characteristics of thermal wave warrant further investigation. In this work, the temperature field of porous media with a high spatio-temporal resolution was obtained in an optically accessible burner using a short-wave infrared camera (SWIR). The effects of operating conditions and structural parameters on the thermal waves were investigated experimentally. The results indicate that SWIR thermometry is more accurate than long-wave infrared thermometry (LWIR) and thermocouples in measuring the temperature of thermal wave. The ability of porous media to broaden the flammability limit is better at pore diameter Dp = 2.3 mm than that at Dp = 1.7 mm and Dp = 3.4 mm. The large flow velocity enhances the stability of the thermal wave and increases the speed of the thermal wave. The average temperature and maximum temperature of thermal wave are positively related to the equivalence ratio, with the maximum temperature rising from 889 °C to 925 °C when the equivalent ratio increases from 0.40 to 0.6. The acquisition of the comprehensive characteristics of thermal wave can help to improve the combustion stability of low-concentration methane and further extend the lean flammability limit.

Methane sealed due to the formation of gas hydrate system in the South China Sea

Although the release of methane into oceans and potentially the atmosphere could accelerate climate change, detailed investigations on the gas source from deep-buried strata and its migration through the gas hydrate stability zone (GHSZ) to the seafloor are limited. These studies are often hindered by the presence of diffracted waves and inaccuracies in seismic velocity models, leading to poor seismic imaging that hampers the understanding of gas sources, migration pathways, and gas hydrate accumulation. In the study, we utilize the technique of common scatter point (CSP) gathers to build an accurate velocity model and obtain high-quality images for a complex gas-hydrate and natural-gas petroleum system. The CSP processing enables the accurate migration of reflected and diffracted waves, resulting in improvements in signal-to-noise ratio and lateral resolution. The improved seismic images offer clearer visualization of various petroleum elements. Specifically, we can identify the top of the hydrate zone and base of the free gas zone within a shallow-buried hydrate system, fault geometries within the free gas zone, a middle-buried natural gas reservoir, gas chimneys as migration pathways, and the deep-buried source rock strata beneath the intrusive volcanic rocks. As a result, we reveal a joint prospect of natural-gas reservoir and gas-hydrate system in the deep-water region of the South China Sea. Our results suggest that methane in the natural gas reservoir has migrated upwardly into the hydrate system, and it is unlikely to leak into the water column.

Trace elements of pyrite in the Ediacaran Doushantuo Formation reveal ancient methane release events

Multiple records of extremely negative carbon isotopes have been reported from the Ediacaran Doushantuo Formation in South China (ca. 635–551 Ma), implying frequent methane release from seafloor sediments of the Yangtze Sea at that time. The incorporation of Ni and Co from AOM-modified biomass into pyrite has emerged as a novel indicator for ancient methane release events, while the widespread presence of pyrite in sedimentary rocks has the potential to yield a continuous long-term record of submarine methane flux. To better understand the magnitude of ancient methane release events during the Ediacaran, we measured trace-elemental compositions for pyrite and bulk rock in the Qinglinkou section and compared these results with data from the more distal (deeper-water) Wuhe section. Three episodes of methane release were identified, one each in the lower, middle, and upper parts of the Doushantuo Formation. The first two release events were observed at both Qinglinkou and Wuhe and may have been linked to destabilization of gas hydrates due to sea-level falls associated with the Marinoan and Gaskiers glaciations. In contrast, the third release event is present only within the Wuhe section, which implies that methane release may have been associated with either a potential glaciation or increased sulfate transport to offshore areas during an oceanic oxygenation event. The methanic signals revealed by pyrite trace elements are consistent with the extremely low carbon isotopic compositions found locally within the study sections. Thus, our study is significant in demonstrating the utility of pyrite trace elements as proxies for ancient methane release events. Determining the spatial extent of a given methane release event will require analysis of correlative units in multiple globally distributed basins and/or cratons. In addition, our results provide new insights into the regulation of methane releases, ocean-redox variation, atmospheric oxygen levels, and bioevolution during the Ediacaran Period.

The Role of Earth Tides in Reactivating Shallow Faults and Triggering Seafloor Methane Emissions

AbstractThe role of solid Earth tide in fault reactivation has significant implications for understanding earthquake triggering, carbon sequestration, and the global carbon budget. Despite extensive research on this topic, the relationship between Earth tide and fault reactivation remains unclear. In this study, we investigate the influence of solid Earth tide on the reactivation of sub‐seabed faults, which may lead to the release of methane. We monitored the sub‐seabed temperature and pore‐fluid pressure at two sites on a fault system located in the Black Sea. Two sets of data obtained from distinct periods revealed inconsistent results. For the first set of data and despite the distance between the two sites (∼790 m), the responses in terms of temperature and pore pressure changes were synchronous (September 2021). We showed from these data that the presence of over‐pressured fluid promotes fault reactivation under Earth tide cycles, resulting in synchronized degassing events. For the second set of data recorded from the same two sites (September 2021–May 2023), we did not identify any concomitance between Earth tides and the monitored parameters. Our analyses show that discrepancies in observations could be related to the fluid discharge/recharge process. The fluid discharge observed during the first period resulted in a decrease in excess pore‐pressure, making the fault insensitive to Earth tides during the subsequent recharge period. Our data also sheds light on conflicting literature results, suggesting that the interaction between faults and Earth tides primarily depends on fluid pore pressure, a parameter rarely measured.

Slow post-fire carbon balance recovery despite increased net uptake rates in Alaskan tundra

Abstract Increasing wildfire occurrence and intensity have immediate effects on northern ecosystems due to combustion of aboveground vegetation and belowground soil organic matter. These immediate impacts have indirect and longer term effects, including deepening of the active layer, changes in soil decomposition rates, and shifts in plant community composition. Despite the increasing fire impacts across the tundra region, the implications of wildfire on ecosystem carbon balance are not well understood. Using paired eddy covariance towers in unburned and burned tundra, we examined the effects of a 2015 wildfire on carbon dioxide and methane fluxes in a wetland tundra ecosystem in the Yukon–Kuskokwim Delta, Alaska, from 2020 to 2022. Wildfire increased the amplitude and variability of carbon uptake and release on seasonal and annual timescales and increased the temperature sensitivity of soil respiration. Seven years post fire, there was annual net uptake in both unburned and burned tundra based on net ecosystem exchange, with the sink strength of burned tundra exceeding that of the unburned tundra by 1.18–1.64 times. However, when considering emissions, it would take approximately 86 years to recover the carbon lost from the wildfire itself. Soil moisture was a dominant driver of fluxes and positively associated with higher rates of carbon dioxide uptake and release and methane release. This study underscores the importance of understanding the effects of wildfire-induced shifts on tundra carbon cycling, allowing better predictions of long-term landscape-scale climate feedbacks as the climate continues to warm.

Insights into prokaryotic communities and their potential functions in biogeochemical cycles in cold seep.

Deep-sea cold seeps are among the most productive ecosystems, sustaining unique fauna and microbial communities through the release of methane and other hydrocarbons. Our study revealed that the influence of seepage fluid on the prokaryotic community in the water column is surprisingly limited, which challenges conventional views regarding the impact of seepage fluids. In addition, we identified that different DOM compositions play a crucial role in shaping the prokaryotic community composition, providing new insights into the factors driving microbial diversity in cold seeps. Furthermore, the study highlighted Proteobacteria as key and multifaceted drivers of biogeochemical cycles in cold seeps, emphasizing their significant contribution to complex interactions and processes. These findings offer a fresh perspective on the dynamics of cold-seep environments and their microbial communities, advancing our understanding of the biogeochemical functions in deep-sea environments.

Using open-path dual-comb spectroscopy to monitor methane emissions from simulated grazing cattle

Abstract. Accurate whole-farm or herd-level measurements of livestock methane emissions are necessary for anthropogenic greenhouse gas inventories and to evaluate mitigation strategies. A controlled methane (CH4) release experiment was performed to determine if dual-comb spectroscopy (DCS) can detect CH4 concentration enhancements produced by a typical herd of beef cattle in an extensive grazing system. Open-path DCS was used to measure downwind and upwind CH4 concentrations from 10 point sources of methane simulating cattle emissions. The CH4 mole fractions and wind velocity data were used to calculate CH4 flux using an inverse dispersion model, and the simulated fluxes were then compared to the actual CH4 release rate. For a source located 60 m from the downwind path, the DCS system detected 10 nmol mol−1 CH4 horizontal concentration gradient above the atmospheric background concentration with a precision of 6 nmol mol−1 in 15 min interval. A CH4 release of 3970 g d−1 was performed, resulting in an average concentration enhancement of 24 nmol mol−1 of CH4. The calculated CH4 flux was 4002 g d−1, showing good agreement with the actual CH4 release rate. Periodically altering the downwind path, which may be needed to track moving cattle, did not adversely affect the ability of the instruments to determine the CH4 flux. These results give us confidence that CH4 flux can be determined by grazing cattle with low disturbance and direct field-scale measurements.

Methane Release in Failure of Microstructure in Coal

Methane Release in Failure of Microstructure in Coal

Көмір шахталарында өндірілген кеңістіктерден метанның бөлінуі

The sources of methane release into the workings of coal mines are the coal seams and interlayers being developed and the host rocks, methane from which is released into both preparatory and treatment workings [1]. A forecast is made about the possibility of moving methane from the mined-out spaces in coal mines to the daytime surface. A comprehensive analytical method has been developed to determine the most likely places of displacement. The regularities of the change in the velocity of movement depending on the temperature, pressure, specific gravity and viscosity of migrating hydrocarbon gases are established. Methane has the highest viscosity. The fracturing coefficient of rocks affecting gas filtration in dry and watered rocks has been revealed. Based on the research, the probable locations of methane migration are substantiated.