Observation-based mine-level methane emission factors uncover inventory biases and constrain emissions from Shanxi’s Coal Mines

Abstract

Bottom-up coal mine methane (CMM) inventories rely on static or empirically derived emission factors (EFs), and therefore mine-level emissions are poorly constrained, limiting the use of these inventories for implementing detailed mitigation strategies. Here, we compiled 1418 satellite-detected methane plumes (2019–2025) and attributed them to 159 active underground coal mines in Shanxi province, China. We further derived observed mine-level EFs, calculated as mine-level emission rates divided by production data. We then compared these observed EFs with those from the State Administration of Coal Mine Safety (SACMS) and Global Coal Mine Tracker (GCMT), and developed a production-capacity-stratified bootstrap framework to upscale emissions from high-gas and outburst coal mines. Observed EFs were highly heterogeneous, right-skewed, temporally variable and negatively correlated with production capacity. Inventory comparisons revealed distinct biases: SACMS reproduced the overall EF magnitude but systematically underestimated EFs for small-capacity coal mines (production capacity <1.2 Mt yr−1), whereas GCMT overestimated EFs for medium- (1.2⩽ production capacity <3.0 Mt yr−1) and large-capacity coal mines (production capacity ⩾3.0 Mt yr−1). Using the production-capacity-stratified bootstrap upscaling framework, we estimated 2023 CMM emissions from high-gas and outburst coal mines in Shanxi to be 7.0 [5.6–8.9] Mt yr−1. Total provincial CMM emissions were estimated at 11.2 [9.3–13.6] Mt yr−1. These findings show that satellite-observed plumes can constrain mine-level EFs, reveal inventory biases, and support observation-based provincial CMM estimation.