Steering the microbial ecosystem: how ethanol boosts coalbed methane output

Microbial-enhanced coalbed methane (MECBM) technology is considered a key approach to increasing CBM yields. However, the biogenic conversion of coal to methane is limited by coal’s recalcitrant macromolecular structure, which constrains production. Therefore, enhancing microbial degradation efficiency is critical for improving CBM yields. To elucidate the mechanism through which ethanol enhances coal biodegradation and methanogenesis, this study employed an integrated approach combining 13C-stable isotope tracing with multi-omics analyses. This strategy enabled investigation of the bioconversion dynamics related to methane, volatile fatty acids (VFAs), and the ethanol-responsive microbial community. The addition of ethanol (2 mg/mL) markedly enhanced methane and hydrogen production by 10.9-fold and 3.1-fold, respectively. It also significantly elevated the soluble chemical oxygen demand (SCOD) level. Ethanol selectively stimulated the proliferation of key hydrogen-producing acetogens, including Clostridium, Syntrophomonas, and Petrimonas, while concurrently enhancing the cooperative interactions between these bacterial populations and methanogenic archaea. Isotope tracking confirmed that the direct incorporation of ethanol-derived carbon into methane, carbon dioxide, and VFAs. Furthermore, the abundance of key functional genes involved in ethanol oxidation, acetic acid metabolism, and central carbon pathways was enriched. This genetic response correlated with increased organic acids production and enhanced mobilization of soluble compounds derived from coal. Collectively, these findings offer novel insights into the stimulatory effects of ethanol on coal bioconversion and highlight a promising strategy to improve coalbed methane (CBM) recovery and utilization.