Investigation of methane content and sorption properties of lignite deposits

Methane is one of the main greenhouse gases (GHG) affecting climate change, and proper quantification of the amount of its emissions to the atmosphere is crucial. The basic parameter for determining the potential amounts of naturally occurring methane in coal for both hard coal and lignite is the methane content. Determination of the methane content of lignite for open-pit mines is not commonly used and required as there is no possibility of its accumulation in the mine workings, as is the case for underground hard coal mines. In this article, two research areas for open-pit lignite mines were analyzed in terms of the methane content of their coal seams. Two direct methods for determining methane content are presented: the single-phase vacuum degassing (SPVD) method and the United States Bureau of Mines (USBM) method, which have been adapted to the conditions of an open-pit lignite mine. In addition, a study of methane sorption kinetics was conducted to determine the potential methane emission rate during coal exploitation and to estimate gas losses during sampling for proper testing. Conclusions from the analysis can be used to develop new or improve existing solutions for determining the methane content of lignite deposits for open-pit mines.