Environmental risk assessment in coal mining with methane degassing

The environmental directives within the European Union consider the necessary environmental protection, establishing strict protocols for controlling methane emissions in mining operations. On the other hand, the exploitation of coal mines has found in the degasification of methane an end in itself, providing a fuel of undoubted energy value that can be easily transformed into electrical or calorific energy. All this must be accompanied by a mining control that establishes the extraction of methane and the prior degasification of the layers as a fundamental task to guarantee the safety of coal mining. Following developments under the Research Fund for Coal and Steel “DD-MET” project (Advanced methane drainage strategy-technology employing underground directional drilling technology for major risk prevention and greenhouse gases emission mitigation), this paper will analyze the related problems, establishing a comparative scenario between Polish and Spanish mines. In Polish mines, it is essential to ensure maximum methane extraction, as the degassed methane has a high economic value in long shafts, while in Spanish mines, the priority is to minimise degassing to control the environmental impact of closed mines. After an analysis of the possible types of methane-emitting sources that could be found distributed throughout the large extensions of the mine surfaces, it is proposed to use as a first approximation to know the areas with environmental risk due to the presence of methane, that of creating a dynamic map of methane concentrations both along the surface of the mine and its surroundings, due to the possible movement of methane by air currents. Subsequently, methane concentration meters on the earth's surface will specify the areas on which we must act to capture or dilute methane until the environmental risk disappears. The results obtained have allowed us to locate the most important environmental concentrations in the access shafts for people and materials and in the ventilation shafts.