Quantifying greenhouse gas emissions from coal fires using airborne and ground-based methods

Coal fires occur in all coal-bearing regions of the world and number, conservatively, in the thousands. These fires emit a variety of compounds including greenhouse gases. However, the magnitude of the contribution of combustion gases from coal fires to the environment is highly uncertain, because adequate data and methods for assessing emissions are lacking. This study demonstrates the ability to estimate CO2 and CH4 emissions for the Welch Ranch coal fire, Powder River Basin, Wyoming, USA, using two independent methods: (a) heat flux calculated from aerial thermal infrared imaging (3.7–4.4 t d−1 of CO2 equivalent emissions) and (b) direct, ground-based measurements (7.3–9.5 t d−1 of CO2 equivalent emissions). Both approaches offer the potential for conducting inventories of coal fires to assess their gas emissions and to evaluate and prioritize fires for mitigation.

► CO2 and CH4 emissions from a Powder River Basin coal fire.
► Airborne estimate derived from thermal infrared imagery.
► Ground-based estimate from measurement of diffuse and vent emissions.
► CO2 equivalent emission estimates roughly agree within a factor of 2.
► Both methods show promise for emission inventories.