Accurate monitoring and accounting of methane emission in underground coal mine

Methane, the second most prevalent greenhouse gas globally, is characterized by its high global warming potential and short atmospheric lifetime. It is primarily emitted from sectors such as coal mining, oil and gas production, agriculture, livestock rearing, and waste management. Active, prudent, and orderly control of methane emissions offers a multifaceted benefit: it mitigates global warming, enhances the economic value through the resource utilization of energy, provides environmental advantages by control of pollutants, and improves safety by reducing production accidents. Methane is also the principal greenhouse gas emitted in coal mine operations. Currently, monitoring and researching the distribution of methane emissions and their concentration within the three-dimensional space of coal mines have become a key focus in China’s methane emission control efforts, which is of significant importance for coal mining enterprises to align with national strategies. A study conducted on a high-gas mine in Shanxi and a low-gas mine in Shaanxi for methane emission monitoring and accounting utilized fixed monitoring, manual monitoring, drone monitoring, and post-mining activity monitoring to investigate the distribution of methane in high and low gas mines in China and to analyze their methane emissions. The results indicate that: ① The methane emission volumes for a certain high-gas mine in Shanxi and a low-gas mine in Shaanxi published by the U.S.-based Climate TRACE website for the year 2022 show a significant discrepancy from the results calculated using the ground measurement method, with the published annual methane emission volume for a certain low-gas mine being 10.92 times that of the ground measurement calculation. The top-down monitoring and accounting methods have been found to be insufficiently accurate and unable to provide reliable data support for carbon trading. ② In the monitoring and accounting of post-mining activities, the use of default values recommended by the IPCC results in methane emissions that are 3 to 5 times higher than those calculated using the ground measurement method, and there is a significant variation in the emissions calculated based on coal samples of different sizes and exposure durations. There is an urgent need for a unified and precise testing standard to ensure fair and accurate data for future carbon market transactions.