The 5th International Conference of Geobiology

As the world's largest lignite resource holder, China holds significant potential for developing biogenic coalbed methane, yet the mechanistic impacts of inorganic mineral components on microbial methanogenesis remain poorly understood. This study systematically investigates the influence of three typical minerals (pyrite, kaolinite, and calcite) on coal bioconversion processes using density-segregated lignite samples (1.3–1.8 g/cm³) from Shaanxi Daliuta. Microbial consortia enriched from coalbed methane well drainage water were employed for bio-gasification experiments, combined with physicochemical characterization (proximate analysis, XRD, XRF, FTIR) , ELISA and high-throughput sequencing. Results demonstrated that ash and fixed carbon contents critically regulate CH₄ production (p<0.05), with Fe, Ti, K, Ca, and Sr concentrations showing strong gas yield correlations. FTIR revealed density-dependent depletion of degradable functional groups (alkyl C-H, hydroxyl/amino, ether bonds). Microbial community analysis identified mineral-driven differentiation between low-ash (1.3–1.5 g/cm³) and high-ash (1.6–1.8 g/cm³) groups, particularly in sulfur-cycling taxa (Desulfobacterota, Geobacter) and methanogens (Methanofollis, p<0.05). Controlled mineral supplementation experiments showed pyrite enhanced volatile fatty acid accumulation (18.7–24.3%) and F₄₂₀ activity (32.5–41.8%) but suppressed late-stage methanogenesis at >2% dosage, while kaolinite (optimal at 2%) and calcite (via pH modulation) boosted CH₄ yields by 45.6%. Mineral-specific restructuring of drainage-derived microbial consortia was observed: pyrite enriched Firmicutes (48.2±3.5%) and Bacteroidota (22.7±2.1%), kaolinite elevated Desulfobacterota (31.4±2.8%), and calcite promoted Proteiniphilum (19.6±1.9%) and Geobacter (15.3±1.2%), with Geobacter's dominance across systems underscoring its role in extracellular electron transfer. These findings elucidate how reservoir-adapted microbial communities interact with mineralogical constraints to govern methanogenic efficiency, providing actionable insights for enhancing in situ coalbed methane recovery through biostimulation strategies.