为探索低压环境下CO₂生物甲烷化和煤炭微生物降解气化特征，选取低阶烟煤(R_max=0.67%)作为发酵底物，利用CO₂和H₂营造低压氛围，开展为期96 d的微生物发酵产气实验。借助气相色谱、16S rRNA基因测序和低温液氮吸附测试分析生物气产出−微生物群落−煤结构内在变化规律。

结果表明：(1) 相比于常规发酵，注入低压CO₂对CH₄的产出有抑制作用，CH₄产出效率呈现降低现象，H₂注入后很快被转化利用，H₂体积分数快速降低，促进了CH₄的产出，同时也改变了生物气产出方式，对发酵液中微生物群落结构也产生了深刻影响，表现为细菌中厚壁菌门(Firmicutes)相对丰度的降低和拟杆菌门(Bacteroidota)相对丰度的升高，尤其是拟杆菌门中S50_wastewater_sludge_group菌属始终为优势菌属，它与unclassified_W27菌属均呈现上升趋势，分析原因为后期H₂的注入，促进了它们的生长代谢。(2) 古菌在属水平分布中，甲烷杆菌属(Methanobacterium)所占比例最大(47.66%~83.05%)，其次是甲烷八叠球菌属(Methanosarcina)、甲烷囊菌属(Methanoculleus)；得益于可以同时利用H₂+CO₂和乙酸等底物，Methanosarcina相对丰度增大趋势显著；而Methanoculleus是通过氢营养途径进行甲烷的合成，后期缺乏H₂，其丰度也快速减小。(3) 相比于原煤，低压CO₂的注入导致煤吸附能力的减弱，总孔容和比表面积的减小；随着低压CO₂注入越多，分形维数D₁和D₂分别出现了增大和减小趋势，煤中孔隙表面粗糙程度增加，孔隙结构复杂程度或均质化程度减小，考虑与微生物降解和碳酸盐沉淀形成的双重作用有关。研究结果丰富了煤炭生物降解与CO₂生物转化利用基础理论，尤其为煤层中CO₂生物转化埋存技术贡献一定的理论依据。

This study aims to investigate the characteristics of CO₂ biomethanation and coal gasification through microbial degradation in a low-pressure environment. With low-rank bituminous coals (R_max = 0.67%) as fermentable substrates, this study conducted a 96-day gas production experiment through microbial fermentation in a low-pressure CO₂ and H₂ environment. Using techniques including gas chromatography, 16S rRNA gene sequencing, and low-temperature liquid nitrogen adsorption, this study delved into the intrinsic variation patterns of biogenic gas production, microbial communities, and coal structures.

The results indicate that compared to conventional fermentation, the injection of low-pressure CO₂ inhibited CH₄ production, leading to a reduced CH₄ production efficiency. After the H₂ injection, the injected H₂ was consumed quickly, resulting in a rapid decrease in the H₂ concentration and contributing to CH₄ production. Meanwhile, the H₂ injection changed the production mode of biogenic gas, exerting a profound influence on the structure of microbial communities in fermentable liquids. Specifically, the relative abundance of Firmicutes and Bacteroidota increased. Notably, the S50_wastewater_sludge_group in Bacteroidota always predominated, trending upward together with the unclassified_W27 genus. This occurred due to the late-stage H₂ injection, which accelerated the growth and metabolism of both bacterial genera. Regarding the distribution of archaea at the genus level, Methanobacterium represented the highest proportion (47.66%‒83.05%), followed by Methanosarcina and Methanoculleus sequentially. Benefiting from the simultaneous consumption of H₂, CO₂, and substrates such as acetic acid, the relative abundance of Methanosarcina exhibited a significant upward trend. In contrast, Methanoculleus, which synthesizes methane via the hydrogenotrophic pathway, displayed a rapidly decreasing relative abundance due to a shortage of H₂ in the later stage. Compared to the raw coals, coals with injected low-pressure CO₂ exhibited a lower adsorption capacity, with the total pore volume and specific surface area decreasing. As more low-pressure CO₂ was injected, fractal dimensions D₁ and D₂ trended downward and upward, respectively, suggesting an increase in the surface roughness of coal pores and a decrease in the complexity/heterogeneity of pore structures. This is inferred to be associated with the dual effects of microbial degradation and carbonate precipitation. The results of this study enrich the fundamental theories on the microbial degradation of coals and the biological transformation and utilization of CO₂, especially providing a theoretical basis for the biological transformation and storage of CO₂ in coal seams.