China's CH4 emissions from coal mining: A review of current bottom-up inventories

Slowdown in China's methane emission growth

The unprecedented surge in global methane levels has raised global concerns in recent years, casting a spotlight on China as a pivotal emitter. China has taken several actions to curb the methane emissions, but their effects remain unclear. Here, we developed the Global ObservatioN-based system for monitoring Greenhouse GAses for methane (GONGGA-CH4) and assimilate GOSAT XCH4 observations to assess changes in China's methane emissions. We find the average rate of increase in China's methane emissions (0.1 ± 0.3 Tg CH4 yr-2) during 2016-2021 slowed down compared to the preceding years (2011-2015) (0.9 ± 0.5 Tg CH4 yr-2), in contrast to the concurrent acceleration of global methane emissions. As a result, the contribution of China to global methane emissions dropped significantly. Notably, the slowdown of China's methane emission is mainly attributable to a reduction in biogenic emissions from wetlands and agriculture, associated with the drying trend in South China and the transition from double-season to single-season rice cropping, while fossil fuel emissions are still increasing. Our results suggest that GONGGA-CH4 provides the opportunity for independent assessment of China's methane emissions from an atmospheric perspective, providing insights into the implementation of methane-related policies that align with its ambitious climate objectives.

Low-carbon development path based on carbon emission accounting and carbon emission performance evaluation: a case study of Chinese coal production enterprises

Carbon emission accounting is the basic premise of effective carbon emission reduction and management. This study aimed to establish the carbon emission model and performance evaluation framework of coal mine production enterprises and clarify the low-carbon development path of enterprises. In this study, we took a typical coal production enterprise (K enterprise) in the Shanxi province of China as the research object. We also estimated the carbon emissions of the enterprise mainly according to the Chinese Carbon Emission Accounting Standard (GB/T 32151.11-2018). The triangular model was used to construct the carbon performance evaluation framework. On this basis, we suggested the enterprise's low-carbon development path. The results showed that (1) the carbon emission of K enterprise in 2021 was 36,875.38 tCO2eq; the carbon emission intensity of each ton of coal produced was 0.089 tCO2eq. The critical carbon emissions were electricity consumption and methane fugitive emissions during production. (2) The evaluation indicators for carbon emission performance revealed an imbalance in K enterprise's economic, energy, and environmental development in 2021. The work on energy saving and consumption reduction was relatively weak. (3) Countermeasures for low-carbon development, including a carbon emission ledger, were proposed based on carbon emission accounting and performance evaluation results. This study can help typical underground coal production enterprises in Shanxi province obtain more accurate carbon emission data, providing practical guidance and reference for the same underground coal production enterprises to improve the carbon emission control effect.

High-resolution assessment of coal mining methane emissions by satellite in Shanxi, China

Accurate assessment of coal mine methane (CMM) emissions is a prerequisite for defining baselines and assessing the effectiveness of mitigation measures. Such an endeavor is jeopardized, however, by large uncertainties in current CMM estimates. Here, we assimilated atmospheric methane column concentrations observed by the TROPOMI space borne instrument in a high-resolution regional inversion to estimate CMM emissions in Shanxi, a province representing 15% of the global coal production. The emissions are estimated to be 8.5 ± 0.6 and 8.6 ± 0.6 Tg CH4 yr-1 in 2019 and 2020, respectively, close to upper bound of current bottom-up estimates. Data from more than a thousand of individual mines indicate that our estimated emission factors increase significantly with coal mining depth at prefecture level, suggesting that ongoing deeper mining will increase CMM emission intensity. Our results show robustness of estimating CMM emissions utilizing TROPOMI images and highlight potential of monitoring methane leakages and emissions from satellites.

Remarkable Spatial Disparity of Life Cycle Inventory for Coal Production in China

Coal is the primary energy source in China, and its life cycle inventory (LCI) is widely used as background data for life cycle assessment studies. Previous research indicates that the inventory of coal production varies regionally. However, the development of complete regionalized LCIs for coal production is quite limited. Here, we establish the first provincial-level LCIs of local coal production and market for coal in China, based on a database of 6,122 coal mines and developed models. In the inventory results of local coal production, the coefficients of variation (CVs) of nine indicators exceed 0.5, especially SO2 and particulate matter emission factors (CVs > 1). Compared with that, the interprovincial coal trade homogenizes the provincial production inventory of market for coal relatively, despite four indicators with CVs exceeding 0.5. Therefore, the regionalized inventory with remarkable spatial differentiation can provide more accurate fundamental data for future research such as electricity production. Furthermore, CH4 emissions from coal production account for 24% of China's total methane emissions, highlighting its significance in mitigating global warming. Moreover, through the increasing coal trade, the significant and implicit plunder of water resources from the three coal net-exporting provinces, located in water-scarce areas, should be noted.

Global trade networks bring targeted opportunity for energy-related CH4 emission mitigation

Recent literature highlights the contributions the global energy sector has made to anthropogenic CH4 emissions, calling for immediate action. However, extant studies have failed to reveal the energy-related CH4 emissions induced by global trades of intermediate and final commodities or services. This paper traces fugitive CH4 emissions via global trade networks using the multi-regional input-output and complex network models. Results show that approximately four-fifths of global fugitive CH4 emissions in 2014 were associated with international trade, of which 83.07% and 16.93% were embodied in the intermediate and final trades, respectively. Japan, India, the USA, South Korea, and Germany were the world's five largest net importers of embodied fugitive CH4 emissions, while Indonesia, Russia, Nigeria, Qatar, and Iran were the five largest net exporters. Gas-related embodied emission transfers were the largest in both the intermediate and the final trade networks. The fugitive CH4 emissions embodied within the intermediate and final trade networks were all characterized by five trading communities. The virtual fugitive CH4 emission transfers via intermediate trade were largely determined by global energy trade patterns, especially the trade in regionally integrated crude oil and natural gas. Significant heterogeneity was revealed by the coexistence of numerous loosely linked economies and several hub economies (e.g., China, Germany, the USA, and South Africa). Interventions on the demand side of interregional and intraregional trade partners in different communities and hub economies will bring targeted opportunities for global energy-related CH4 emission reduction.

Technological avenues and market mechanisms to accelerate methane and nitrous oxide emissions reductions

Strategies targeting methane (CH₄) and nitrous oxide (N₂O) emissions are critical to meeting global climate targets. Existing literature estimates the emissions of these gases from specific sectors, but this knowledge must be synthesized to prioritize and incentivize CH₄ and N₂O mitigation. Accordingly, we review emissions sources and mitigation strategies in all key sectors (fuel extraction and combustion, landfilling, agriculture, wastewater treatment, and chemical industry) and the role of carbon markets in reducing emissions. The most accessible reduction opportunities are in the hydrocarbon extraction and waste sectors, where half (>3 Gt-CO₂e/year) of the emissions in these sectors could be mitigated at no net cost. In total, 60% of CH₄ emissions can be mitigated at less than $50/t-CO₂. Expanding the scope of carbon markets to include these emissions could provide cost-effective decarbonization through 2050. We provide recommendations for carbon markets to improve emissions reductions and set prices to appropriately incentivize mitigation.

Toward a Carbon-Neutral State: A Carbon–Energy–Water Nexus Perspective of China’s Coal Power Industry

Carbon neutrality is one of the most important goals for the Chinese government to mitigate climate change. Coal has long been China’s dominant energy source and accounts for more than 70–80% of its carbon emissions. Reducing the share of coal power supply and increasing carbon capture, utilization, and storage (CCUS) in coal power plants are the two primary efforts to reduce carbon emissions in China. However, even as energy and water consumed in CCUS are offset by reduced energy consumption from green energy transitions, there may be tradeoffs from the carbon–energy–water (CEW) nexus perspective. This paper developed a metric and tool known as the “Assessment Tool for Portfolios of Coal power production under Carbon neutral goals” (ATPCC) to evaluate the tradeoffs in China’s coal power industry from both the CEW nexus and financial profits perspectives. While most CEW nexus frameworks and practical tools focus on the CEW nexus perturbation from either an external factor or one sector from CEW, ATPCC considers the coupling effect from C(Carbon) and E(Energy) in the CEW nexus when integrating two main carbon mitigation policies. ATPCC also provides an essential systematic life cycle CEW nexus assessment tool for China’s coal power industry under carbon-neutral constraints. By applying ATPCC across different Chinese coal industry development portfolios, we illustrated potential strategies to reach a zero-emission electricity industry fueled by coal. When considering the sustainability of China’s coal industry in the future, we further demonstrate that reduced water and energy consumption results from the energy transition are not enough to offset the extra water and energy consumption in the rapid adoption of CCUS efforts. However, we acknowledge that the increased energy and water consumption is not a direct correlation to CCUS application growth nor a direct negative correlation to carbon emissions. The dual effort to implement CCUS and reduce electricity generation from coal needs a thorough understanding and concise strategy. We found that economic loss resulting from coal reduction can be compensated by the carbon market. Carbon trading has the potential to be the dominant profit-making source for China’s coal power industry. Additionally, the financial profits in China’s coal power industry are not negatively correlated to carbon emissions. Balance between the carbon market and the coal industry would lead to more economic revenues. The scenario with the most rapid reduction in coal power production combined with CCUS would be more sustainable from the CEW nexus perspective. However, when economic revenues are considered, the scenario with a moderately paced energy transition and CCUS effort would be more sustainable. Nevertheless, the ATPCC allows one to customize coal production scenarios according to the desired electricity production and emission reduction, thus making it appropriate not only for use in China but also in other coal-powered regions that face high-energy demands and carbon neutrality goals.

Analysis of the Characteristics of CH4 Emissions in China's Coal Mining Industry and Research on Emission Reduction Measures

CH₄ is the second-largest greenhouse gas and has a significant impact on global warming. China has the largest amount of anthropogenic coal mine methane (CMM) emissions in the world, with coal mining emissions (or gas emissions) accounting for 90% of total energy industry emissions. The results of CH₄ emission inventories from previous studies vary widely, with differences in the spatial and temporal dimensions of gas emission factors of belowground mining being the main points of disagreement. Affected by the policies of “eliminating backward production capacity” and “transferring energy base to the northwest”, China’s coal production layout has changed greatly in the past ten years, but the closely related CH₄ emission factors have not been dynamically adjusted. This paper investigated 23 major coal producing provinces in China, obtained CH₄ emission data from coal mining, calculated CH₄ emission factors in line with current production conditions, and studied the reduction measures of coal mine gas emission. According to the CH₄ emission data of China’s coal mines in 2018, 15.8 Tg of methane is released per year in the coal mining industry in China, and 11.8 Tg after deducting recycling. Shanxi Province’s CH₄ emissions are much higher than those of other provinces, accounting for 35.5% of the country’s total emissions. The weighted CH₄ emission factor of coal mining in China is 6.77 m³/t, of which Chongqing is the highest at approximately 60.9 m³/t. Compared with the predicted value of the IPCC, the growth trend of CCM has slowed significantly, and the CH₄ utilization rate has gradually increased. This change may be aided by China’s coal industry’s policy to resolve excess capacity by closing many high-gas and gas outburst coal mines. In addition, the improvement of coal mine gas extraction and utilization technology has also produced a relatively significant effect. This paper determines the distribution of methane emissions and emission sources in China’s coal mining industry, which is useful in formulating CCM emission reduction targets and adopting more efficient measures.

Geochemical Partitioning of Heavy Metals and Metalloids in the Ecosystems of Abandoned Mine Sites: A Case Study within the Moscow Brown Coal Basin

Significant environmental impacts of mining activities connected with high-sulfur materials result from the production of acid mine drainage and potentially toxic elements, which easily migrate to adjacent ecosystems due to the typical absence of vegetation on spoil heaps and toeslope talus mantle. In this paper, we present the results of the first comprehensive study of the ecosystems affected by acidic and metal-enriched (Al, Ca, Co, Cu, Fe, Mg, Mn, Ni, and Zn) mine drainage conducted at spoil heaps and adjacent talus mantle under semihumid climate conditions within the Moscow Brown Coal Basin (Central Russian Upland, Tula Region, Russia). A total of 162 samples were collected, including 98 soil samples, 42 surface water samples, and 22 plant samples (aerial tissues of birch). Coal talus mantle materials of Regosols were characterized by the increased concentration of water-soluble Ca, K, Mg, and S, and all mobile fractions of Al, Co, S, and Zn. The chemical composition of birch samples within the zones affected by acid mine drainage differed insignificantly from those in the unpolluted ecosystems with black soils, due to the high tolerance of birch to such conditions. Differences between the affected and undisturbed sites in terms of the chemical composition decreased in the following order: waters > soils > plants. The geochemical characterization of plants and soils in coal mining areas is essential for the mitigation of negative consequences of mining activities.

Regional trends and drivers of the global methane budget

The ongoing development of the Global Carbon Project (GCP) global methane (CH₄ ) budget shows a continuation of increasing CH₄ emissions and CH₄ accumulation in the atmosphere during 2000-2017. Here, we decompose the global budget into 19 regions (18 land and 1 oceanic) and five key source sectors to spatially attribute the observed global trends. A comparison of top-down (TD) (atmospheric and transport model-based) and bottom-up (BU) (inventory- and process model-based) CH₄ emission estimates demonstrates robust temporal trends with CH₄ emissions increasing in 16 of the 19 regions. Five regions-China, Southeast Asia, USA, South Asia, and Brazil-account for >40% of the global total emissions (their anthropogenic and natural sources together totaling >270 Tg CH₄  yr^-1 in 2008-2017). Two of these regions, China and South Asia, emit predominantly anthropogenic emissions (>75%) and together emit more than 25% of global anthropogenic emissions. China and the Middle East show the largest increases in total emission rates over the 2000 to 2017 period with regional emissions increasing by >20%. In contrast, Europe and Korea and Japan show a steady decline in CH₄ emission rates, with total emissions decreasing by ~10% between 2000 and 2017. Coal mining, waste (predominantly solid waste disposal) and livestock (especially enteric fermentation) are dominant drivers of observed emissions increases while declines appear driven by a combination of waste and fossil emission reductions. As such, together these sectors present the greatest risks of further increasing the atmospheric CH₄ burden and the greatest opportunities for greenhouse gas abatement.

Evaluation of comprehensive monthly-gridded methane emissions from natural and anthropogenic sources in China

The observed atmospheric methane (CH₄) concentration in China has grown rapidly in recent years, showing marked spatial-temporal variation. However, existing inventories, most of which are yearly, provincial, and incomplete, have failed to reflect the spatial variation and seasonal trends of CH₄ emissions. This study aims to develop a high-resolution (0.05° × 0.05°) monthly inventory of CH₄ emissions across China in 2015 from eight major natural and anthropogenic sources. The inventory evaluation of CH₄ emissions was based on the gridded activity data and high spatial-temporal resolution emission factors, which were estimated by their relationship with environmental factors in most source sectors. The results showed that the annual CH₄ emissions across China were 61.65 Tg, of which 85% was associated with anthropogenic emissions. Energy activities, livestock, and paddy fields were the largest contributors, accounting for 31% (19.06 Tg), 24% (15.01 Tg) and 19% (11.45 Tg) of the total emissions respectively, followed by vegetation (7%, 4.52 Tg), wetlands (7%, 4.20 Tg), wastewater (6%, 3.43 Tg), municipal solid waste, (4%, 2.59 Tg) and biomass burning (2%, 1.40 Tg). However, these proportions varied by month; paddy fields, vegetation, and wetlands emitted the most CH₄ in July and August with approximately 29%, 14%, and 8% of total emissions, respectively, and least in January and December with 0%, 2%, and 2%, respectively, leading to a CH₄ emissions peak in summer and a valley in winter. Moreover, the major contributing provinces of CH₄ emissions in China were Inner Mongolia, Shanxi, Sichuan, Guizhou, and Hunan, accounting for 33% of China's total emissions. The dominant emission sources were energy activities in Mongolia, Shanxi, and Guizhou; livestock in Sichuan; and paddy fields in Hunan. This improved inventory of CH₄ emissions can help understanding the spatial-temporal variation of CH₄ concentration in the atmosphere and formulating regional-seasonal-specific emission reduction policies.

Introduction to Modern Climate Change. Andrew E. Dessler: Cambridge University Press, 2011, 252 pp, ISBN-10: 0521173159

Climate change is the variability of the climate system that includes the atmosphere, the biogeochemical cycles (Carbon cycle, Nitrogen cycle and Hydrological cycle), the land surface, ice and the biotic and abiotic components of the planet earth. Significant impact of climate change is seen in the form of rise in temperature called as global warming. Carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O) are the primary greenhouse gases (GHGs) mainly responsible for the global warming and climate change. These GHGs have drawn lot of attention due to their significant role in the global warming potential. Intergovernmental Panel on Climate Change (IPCC) suggested to stop global warming at 1.5oC above preindustrial levels as warming beyond this level might lead to heat extremes, alter insect and plant phenology (Phenological shifts) and more occurrence of vector borne diseases. Climate change is the topic of interest in all fields of life starting from social science and going to the applied science. Global climate cycles and world food production systems are under threat due to the recent climate extreme events. These events include heat waves and change in the rainfall patterns. Thus, risk reduction intervention in the form of mitigation and adaptation is required to minimize the impacts of climate change. Mitigation option includes understanding the present and future components of the climate system and interaction among them through coupled modeling system i.e. Global Circulation Model (GCM). Finally, global issue of climate change could be addressed by taking worldwide cooperation and action and adopting sustainable measures like use of alternative energy sources. The visible benefit on recovery of climate has been seen recently through global lockdown against coronavirus disease 2019 (COVID-19) pandemic.