Abstract:

The coal sector, which is the largest anthropogenic methane source in China, accounts for 38% of the country’s total anthropogenic methane emissions. Studies have identified significant uncertainties in existing inventories, indicating the urgency to enhance the accuracy of China’s coal methane inventory. Using a self-built dynamic mine-level database and high-tier methodologies in emission calculation recommended by IPCC (Intergovernmental Panel on Climate Change) inventory guidelines, this work improved China’s coal methane inventory and revised the estimation of coal methane emissions in 2012 and 2014. The results show consistency of coal methane emissions in 2012 between this work (23.33 Tg) and China’s national greenhouse gas inventory (23.85 Tg). However, it is important to note that the consistency observed in 2012 does not guarantee the accuracy of China’s national inventory due to significant discrepancies among sub-sources. In fact, coal methane emissions in 2014 were found to be 25.87 Tg, or 23% higher, compared to the national inventory. Further analysis reveals that abandoned mine methane (AMM) is the most significant source of this discrepancy, which has emerged as the second largest contributor of coal methane emissions, accounting for a share of 10%?20%, but has been substantially underestimated in previous studies. Additionally, this work identifies the dynamic variation of key parameters, such as the emission factor, as having a significant impact on inventory accuracy. It highlights the importance of timely updates to fundamental data, such as the timely measurements of mine gas gushing rates. Overall, this work makes significant contribution to improving the accuracy of coal methane inventory, supporting policy decisions of methane mitigation, and ensuring high-quality compliance.

Key words: Greenhouse gas inventory, Coal methane, Abandoned mine methane (AMM)