The study looked at how different types of coal react to being cooled with liquid nitrogen, which is important for getting methane gas from coal. They tested lignite and bituminous coal to see how their pore structures changed after cooling. Lignite coal had more changes in its pores, making it more damaged than bituminous coal. Cooling also made the coal weaker and more likely to break. The cracks in the coal became more random and twisted after cooling, especially in lignite coal. Overall, lignite coal was more affected by cooling than bituminous coal, leading to more damage and fragmentation.