Comparative analysis concerning the amount of methane released into the atmosphere and collected by hard coal mines in Poland

The process of underground hard coal exploitation is accompanied by the release of methane. This phenomenon has been present in the majority of Polish hard coal mines, with the intensity of methane release from hard coal seams exhibiting a growing trend on a year-by-year basis. The highest amount of this gas is emitted into the atmosphere, with only a small part being collected by methane drainage systems and subsequently used for industrial purposes. In 2017, all the hard coal mines in Poland released 611.15 million m³ of methane directly from underground headings into the atmosphere together with the ventilation air, whereas 337 million m³ of this gas was collected by methane drainage systems. The paper presents the results of an analysis aiming to identify homogeneous mines in terms of the quantities of methane emitted into the atmosphere of the natural environment and collected from the rock mass by means of methane drainage systems, with account being taken of the effectiveness of this process. The analysis was carried out on the basis of the 2017 data and it encompassed 21 hard coal mines. The detailed analysis was conducted using one of the hierarchical grouping methods, namely the agglomeration algorithm. This tool made it possible to isolate homogeneous subsets of items under analysis (mines), adopting the Euclidean distance as a measure of distance between the mines.