Study of greenhouse gas emissions from smoldering coal fires: Estimation considering the indirect greenhouse effect of precursors

Smoldering coalfield fires generate greenhouse gases (GHGs) and their precursors, contributing to the intensification of global warming. The study on the contribution of GHGs from smoldering coal fires to climate warming has been a disputed topic. This work proposes a novel approach to estimating GHG emissions from coal smoldering by measuring CO2, CH4, and CO under different thermal environments (220, 240, 260, and 300 °C). Results indicate that the contribution of CO2 produced by smoldering to the greenhouse effect decreased from 33.67 % to 23.52 % as thermal environments increased. The comprehensive effect of greenhouse effect induced by the precursors (CH4 and CO) increased from 66.33 % to 76.48 %, showing that the impact of precursors on the greenhouse effect should not be ignored. Additionally, the study demonstrates that the greenhouse effect generated by smoldering accounts for 18.40 %–40.92 % of the equivalent emissions produced by the complete combustion of the same mass of coal. This suggests that not all combustibles undergo conversion into greenhouse gases during the smoldering process. The annual amount of GHG emissions from coal fires in China is estimated as 6.52–42.27 million tons. Importantly, this study calculates basin-specific emission factors based on coal smoldering, providing a more accurate approach for determining the GHG emissions from coal fires. [Display omitted] •Establishing GHG prediction equation for coal smoldering through experiments.•The CO2-e contribution of CO generated by coal smoldering reached 31.58 %.•Equivalent GHG generated by smoldering was 18.40 %–40.92 % of complete combustion.•Assessment of greenhouse effect by precursors was crucial and should not be ignored.•GHG emissions from smoldering and complete combustion of coal were compared.