Application of remote sensing in coal-fire studies and coal-fire–related emissions

Coal fires are one of the most common geohazards in most coal-producing countries, such as india and China. Combustion can occur spontaneously or due to anthropogenic causes, either within underground coal seams or in exposed layers of coal on Earth’s surface. Once started, coal fires are difficult to extinguish and sometimes cannot be controlled. In addition to burning millions of tons of coal, the fires have an enormous negative impact on the local and global environments. Coal fires produce large quantities of greenhouse gases, such as CO, CO2, CH4, SOx, and NOx, which have a direct impact on the local and global atmospheric composition. Since the preindustrial era, the concentration of CO2, a major greenhouse gas that contributes to global warming, has increased from 280 ppm to 375 ppm. Land subsidence is an associated problem in areas that are affected by coal fires. Coal fires also create operational difficulties in existing mines and endanger human safety. After the first use of remote sensing to study a coal fire in the early 1960s, this technology became a useful and convenient tool for the detection and monitoring of additional coal fires. Several air- and spaceborne thermal remote sensors are available for studying coal fires. Coal-fire–related emissions have not been studied extensively; ground-based methods mainly use CO2 detection instruments or other indirect calculations (e.g., amount of coal burnt). Few attempts are being made to estimate coal-fire emission using remote sensing.