Mechanisms of microbial methanogenesis and energy metabolism in anaerobic fermentation of coals with different ranks

Methane generation is intrinsically linked to the energy conversion processes that take place during the anaerobic decomposition of coal. This study investigates the differences in energy metabolism of bio-methane production from coal samples with different ranks during anaerobic fermentation. Four coal samples (BYH, ML, SQ, and QD) were selected for anaerobic fermentation experiments, and methane yields, heat release, changes in small-molecule organic compounds, and microbial community structures were analyzed using gas chromatography, microcalorimetry, and other techniques. The results show that the BYH coal sample, which can generate abundant degradable organic substrates, has the highest methane yield and heat release, with peak reaction heat and gas production values reaching 32.539 J/g and 65.05 μmol/g, respectively. Microbial community analysis reveals that the high abundance of Geobacter and Methanoculleus in the BYH system enhances the direct interspecies electron transfer (DIET) and hydrogenotrophic methanogenesis pathways. In contrast, the SQ system, dominated by Methanothrix and Macellibacteroides, generates more aromatic large-molecule organic compounds and has lower methanogenesis efficiency. By providing theoretical foundations, this research aids in improving the coal bio-methanation process, thus contributing to the efficient utilization and environmental sustainability of coal resources.