The analysis of phenomena related to gas transport in hard coal is important with regard to the energetic use of coal bed methane (CBM), the reduction of greenhouse gas emissions to the atmosphere (CO₂) and the prevention of natural hazards such as methane hazards and gas and rock outbursts. This article presents issues concerning the feasibility and scope of applying the unipore and bidisperse diffusion models to obtain knowledge concerning the kinetics of methane sorption and its diffusion in the carbon structure, depending on its petrography. Laboratory tests were carried out on coal samples which varied in terms of petrography. Quantitative point analyses were carried out, based on which content of groups of macerals was determined. The degree of coalification of coal samples was also determined based on measurements of vitrinite reflectivity R₀ and the volatile matter content V^daf. Sorption kinetics were also investigated, and attempts were made to adjust the unipore and bidisperse models to the real sorption kinetic courses. This allowed the identification of appropriate coefficients controlling the course of sorption in mathematical models. An attempt was also made to assess the possibility of applying a given model to properly describe the phenomenon of methane sorption on hard coal.

The content of natural methane in hard coal seams, called methane-bearing capacity, is the basic parameter that enables the level of methane hazard to be determined in hard coal mines. This parameter is also used to determine the potential quantities of methane that can be collected and used for energy purposes and the amount of its harmful emission to the atmosphere. Direct methods are most often used to determine methane-bearing capacity. An important aspect that has a great influence on the final result of the research is the gas losses generated at the stage of sampling. Under the conditions of the Polish mining industry, the direct drill cuttings method is used to determine the methane-bearing capacity. Gas losses are compensated for in this method with the use of the coefficient 1.12, by which the obtained result is multiplied. In this paper, a multi-parameter analysis of gas loss in the determination of methane-bearing capacity in hard coal seams has been carried out. Several experiments were performed to identify the most important aspects to be taken into account to obtain a correct result. A methane-bearing capacity test was conducted using two direct methods: the direct drill cuttings method, otherwise known as the single-phase vacuum degassing method, and a method based on the United States Bureau of Mines standards. Sorption studies, such as methane sorption kinetics tests, were also conducted in which sorption properties, such as sorption capacity, effective diffusion coefficient, and half sorption time, were determined. Methane sorption isotherms were also determined, and pore structure was analysed. Based on the obtained test results, an analysis was carried out which made it possible to present appropriate conclusions concerning the gas losses during the methane-bearing capacity test, generated at the stage of sampling. The final result of the work was the proposal of a new gas loss coefficient for the direct drill cuttings method of methane-bearing capacity determination.

The methane hazard is one of the natural hazards occurring in hard coal mining. The content of natural methane in hard coal seams, the so-called methane-bearing capacity, is one of the key parameters that allow for proper assessment of the methane hazard and the state of the threat of gas and rock outbursts. For safety purposes, there is a constant need to improve the methods for the determination of this parameter. In the conditions of Polish mining, the method used for methane-bearing capacity determination is the direct drill cuttings method. This paper contains a comparative study presenting three different methods of methane-bearing capacity determination. Tests were conducted using two direct methods (the drill cuttings method and the United States Bureau of Mines (USBM) method), and the indirect method based on the desorption intensity index. On the basis of the obtained test results, it was found that the results obtained with the USBM method were slightly higher than those obtained with the direct drill cuttings method. Gas losses, an important element affecting the final value of the assay, were also analysed. This comparative study will evaluate the validity and applicability of the above methods under specific conditions in hard coal mining.

Atmospheric methane emissions from the energy sector, particularly coal mines, are a component of total global methane emissions. Its presence causes climate changes that contribute to global warming. Methane is a potent greenhouse gas (GHG) with a global warming potential (GWP) approximately 30 times greater than that of carbon dioxide over a 100-year period. The estimation of methane emissions from both underground hard coal mines and open-pit lignite mines is performed based on guidelines that follow the methods recommended in the core publications of the International Panel on Climate Change (IPCC). The methane emission rate determination method developed by scientific institutions is allowed. This article focuses on the analysis and formulation of guidelines for determining the potential methane emissions from open-pit lignite mines, which are determined based on the emission factor and coal production. Coalbed methane content was tested using two methods to determine the methane emission factor. Results of sorption tests were also presented. The results obtained can be used for the development of new solutions or the improvement of current solutions for the determination of the methane emission rate in open-pit lignite mines.