Quantification of Fugitive Carbon Emissions from Uncontrolled Combustion in Coal Fire Area: the Sandaoba Coalfield, Xinjiang, China.

Spontaneous coal fires are a significant source of greenhouse gas emissions, contributing to global warming. However, the lack of reliable estimation methods and research has obscured the full environmental impact of these emissions. This paper presents a novel quantification method for fugitive carbon emissions from spontaneous coal combustion. A combination of field measurements, laboratory tests, and geostatistical analysis led to the development of the Carbon Emission Flux (CEF) model, which was applied to the Sandaoba coalfield fire areas. The study quantitatively estimates the average CO2 emission fluxes from borehole, fissure, and soil sources: 517 g/m2·s, 61.5 g/m2·s and 5.33 mg/m2·s, respectively. Borehole fluxes exhibit the highest intensity, while fissures contribute the most carbon emissions. Both temperature and gas velocity significantly and positively influence the CO2 concentration in borehole and fissure emissions. Surface fissure density, measured across different fire areas, averages 1.039 × 10-3 per unit area. Using chamber flux measurement and Kriging geostatistical interpolation, the net soil-diffuse flux was determined to be 2.406 mg/m2·s after background removal. Methane emissions are also considered, with a correction factor of 1.004%. The total annual fugitive carbon emissions from the Sandaoba coalfield fire are estimated at (6.53 ± 1.86) × 10⁵ tons/yr (CO₂ equivalent), with a robust uncertainty of 28.6%. The study further highlights the significant carbon reduction achieved through local fire suppression efforts, applicable across all emission sources.