###### Abstract
Coal, having a moderate intrinsic porosity, can store about six times more gas than sandstones of an equivalent volume. However, the gas storage capacity and methane generation are functions of coal rank and pressure. Therefore, of the coal ranks, anthracic has the greatest storage capacity, followed by bituminous and subbituminous coals, and lignite [6]. Methane is generated in low-rank coals, such as lignite, through microbial activity [9] and in higher-rank coals, such as anthracic, during the thermal maturation of their organic compounds [10]. The generated methane is adsorbed on the surface of the organic materials that make up the coal, while the coal's storage capacity is described by the Langmuir sorption isotherm and is related to the adsorbed \begin{table}
\begin{tabular}{l c c c c c c} \hline \hline \multirow{2}{*}{**Stated for 2021**} & **Primary Energy Consumption (E)** & **Oil Consumption (E)** & **Coal Consumption (E)** & **Natural Gas Consumption (E)** & **Renewable Consumption (E)** & **CO\({}_{2}\) Emissions \({}^{**}\) \\ \hline North America & 113.7 & 42.1 & 11.3 & 37.2 & 8.4 & 6.2 \\ \hline S. and Cent. & & & & & & \\ America & 28.5 & 11.3 & 1.46 & 5.88 & 3.4 & 1.5 \\ \hline Europe & 82.4 & 27.6 & 10.0 & 20.6 & 10.1 & 4.0 \\ \hline Middle East & 37.8 & 16.3 & 0.34 & 20.7 & 0.18 & 2.7 \\ \hline Africa & 20.0 & 7.86 & 4.21 & 5.9 & 0.47 & 1.7 \\ \hline Asia–Pacific & 272.5 & 70.65 & 127.6 & 33.1 & 17.2 & 20.0 \\ \hline CIS \({}^{*}\) & 40.3 & 16.3 & 0.34 & 20.7 & 0.18 & 2.7 \\ \hline Total World & 595.2 & 184.2 & 160.1 & 145.4 & 39.9 & 39.0 \\ \hline \hline \end{tabular}  
* Commonwealth of Independent States, ** sum of CO\({}_{2}\)-equivalent emissions from energy, flaring, methane emissions, and industrial processes.  
\end{table} 
Table 1: Primary energy consumption, consumption by fuel, and carbon dioxide-equivalent emissions [1]. gas content and pressure [11]. Large volumes of CBM are deposited in the internal surface area of the coal's micropores and in the larger pores of its surface, while small amounts of methane can be found in the void spaces as coal shrinks after deposition. Methane occurs in coal deposits at pressures higher than in atmospheric conditions, and thus, methane desorption is limited because of the nonlinear Langmuir-type isotherm. Macropores (cleats) of the coal matrix are the main track for the flow of gas [12]; however, pressure needs to decrease significantly below the critical desorption pressure in order to promote desorption, as in the case of the mining process. The system of cleats is divided into face cleats that are continuous and provide connectivity and butt cleats that are noncontinuous and often end at face cleats. The production of CBM from the surface of coal involves the dewatering of cleats, which leads to a pressure decrease in the reservoir, liberating the methane adsorbed on the coal face so that it flows through the macropore fracture system to the wellbore [13]. Geological characteristics, such as the thickness and tightness of the overburden and deposit tectonics, are crucial for the desorption of CBM deposits [14]. In addition, pore characteristics as well as the heterogeneity, coal rank, metamorphic degree of coal reservoirs, as well as the composition of CBM gases are key factors affecting the migration and extraction of CBM [15; 16]. It has been previously reported that during low-temperature and low-pressure N\({}_{2}\) adsorption experiments, the adsorption of N\({}_{2}\) molecules on lignite was higher than those found on bituminous coal and anthracite [17; 18]. Lignite deposits are generally located near the surface of the earth and are characterized as lightly metamorphosed natural carbonaceous materials with a higher porosity as compared with subtituminous coal [19].