Microbial coal gasification is a highly promising bioenergy technology, yet its efficiency is often constrained by the highly polymeric structure of coal. This study explores a novel approach to enhance methane production from low-rank coal through anaerobic co-degradation with sawdust. Using Xilinguole lignite as the substrate, we systematically assessed how wood chip supplementation influences microbial degradation efficiency and community dynamics. Results demonstrated that co-degradation significantly increased methane yield—most notably at a coal-to-wood chip ratio of 4:1—far surpassing methane production from coal alone. The addition of sawdust enriched the substrate with bioavailable hydrocarbons and organic acids, and enhanced the degradation of complex compounds including aromatics and lipids. Microbial analysis revealed a marked shift in community structure, with increased abundance of key genera such as Bacillus, Clostridium, and Bathyarchaeia, indicative of enhanced functional specialization and metabolic cooperation. Network analysis further confirmed more tightly interconnected microbial communities in co-degradation systems. These findings underscore the potential of sawdust as a co-substrate to facilitate microbial coal conversion by improving utilization efficiency and promoting synergistic microbial interactions. This strategy offers a practical and efficient means to advance the bioenergy recovery from low-rank coal resources.

Microbial coal gasification technology is a new, efficient, and clean method for coal resource mining; however, its commercial application remains limited by gasification efficiency and cost. To examine the impact of biomass on microbial coal gasification processes, improve gas production efficiency, and identify economically viable nutrient supplements with broad availability, this study employed culture medium (CM), sawdust (SD), and blue-green algae (BA) as nutritional additives. An anaerobic fermentation experiment with three-stage nutrient supplementation was conducted using a fed-batch reactor. The comparison of gas and liquid compositions within reactors throughout the reaction process demonstrated that key nutrient supplementation could reactivate methane production in reactors in which gas generation had ceased. Gas composition analysis revealed that under identical conditions, BA supplementation achieved the highest methane yield (24.49 ± 1.31 mL/g), followed by SD (1.56 ± 0.1 mL), representing 24.13-fold and 1.53-fold increases, respectively, compared with the yield in CM control group. Analysis of 16S rRNA sequencing indicated that nutrient supplementation induced microbial community differentiation, with dominant bacterial genera (Herbinix, Proteiniborus) shifting according to the organic composition of the liquid environment. A positive feedback relationship between microbial life activities and functional performance further confirmed the dominance of these superior strains. This study advances the understanding of substrate degradation characteristics in microbial coal degradation systems and provides theoretical support for the clean and efficient coal exploitation.