Comparison of Biodegradation Mechanisms and Structural Evolution Characteristics between Anthracite and Bituminous Coals

Microbial-enhanced coalbed methane technology has been found to promote biomethane production, while the influence of coal rank on anaerobic degradation remains unclear. This study evaluated the biomethane potential of anthracite and high-volatile bituminous coal through comprehensive analyses including gene sequencing, FTIR, XRD, and SEM. Semiquantitative analysis of molecular structures revealed that anthracite consisted predominantly of aromatic hydrocarbons, whereas bituminous coal contained more aliphatic structures. Microbial degradation mainly affects heteroatomic functional groups and aliphatic structures, showing limited efficiency in degrading aromatic layer structures. Anthracite displays a smooth surface microstructure, whereas high volatile bituminous coal’s rough surface provides more microbial attachment sites. In high volatile bituminous coal cultures, functional bacteria such as Enterobacter, Clostridium, and Oscillibacter reached a combined relative abundance of 63.1%, which increased the variety of organic heterocyclic compounds, organic acids, and their derivatives in metabolites. These effects ultimately resulted in a 72.4% higher methane yield from bituminous coal compared to anthracite. This research provides important insights for accelerating the engineering application of microbial-enhanced coal-bed methane technology.