Mitigating climate change by abating coal mine methane: A critical review of status and opportunities

Abstract

Methane has a short atmospheric lifetime compared to carbon dioxide (CO₂), ∼decade versus ∼centuries, but it has a much higher global warming potential (GWP), highlighting how reducing methane emissions can slow the rate of climate change. When considering the contribution of greenhouse gas (GHG) emissions to current global warming (2010–2019) relative to the industrial revolution (1850–1900) levels, methane contributes 0.5 °C or ∼ a third of the total. The most recent post-2023 global estimates of methane emissions by bottom-up (BU) and top-down (TD) approaches for the coal mining sector are in the range of ∼41 ± 3 Tg yr⁻¹ and 33 ± 5 Tg yr⁻¹, respectively. This divergence, notwithstanding overlapping confidence intervals, is a result of differences between applied TD global inversion models and BU emission inventories. Further research can help to better refine emissions from the various contributing coal mine methane (CMM) emissions sources. The coal mining sector accounts for over 10 % of global anthropogenic methane emissions. The contribution of CMM emissions to the global budget have increased since 2000, although upward and downward regional trends have been observed.

The Global Methane Pledge (GMP), which was signed by more than 150 nations, aims to reduce methane emissions by 30 % from 2020 levels by 2030. This could eliminate 0.2 °C of warming by 2050. The success or failure to reach the emission reduction targets of the GMP will depend on engagement with different sectors of the economy. In that regard, the coal sector could play a significant role for mitigating emissions and reaching emission reduction targets. The International Energy Agency (IEA) and United States Environmental Protection Agency (U.S. EPA) both estimate that over half of global methane emissions from coal operations could be avoided with the application of existing technologies. However, setting up emission reduction scenario targets for the coal mining sector poses significant challenges, which require clear understanding of the magnitude and behavior of CMM emission sources. Notwithstanding regional differences, with improved reporting and data transparency, emission control potential can be more accurately defined, which can inform effective and defensible policy approaches.

This paper highlights the climate forcing role of methane in the atmosphere and presents a detailed review of CMM emission sources along the coal lifecycle, traditional and new inventory practices applied in different countries, the status of estimating CMM emissions, and opportunities and difficulties associated with mitigating emissions from different CMM sources. Different policy approaches utilizing regulatory and economic mechanisms are explored and concluding remarks for importance and tools of CMM emission mitigation are provided. Ultimately, this paper aims to inform global CMM mitigation and emission reduction scenario targets for the coal mining sector.