Influence of pyrite on biogenic coal bed methane production and microbial community structure

Abstract:

[Objective] To investigate the coal’s pyrite on the biological gas production. [Methods] In present work, we took the coal obtained from Yulin City, Shaanxi Province as substrate and the methanogenic microorganisms domesticated by our laboratory as inoculation flora. The simulation biological gas production of coal was carried out by dosing different content of pyrite into the anaerobic system. The changes of CH₄ content, total volatile fatty acids (VFAs) concentration, coenzyme F₄₂₀ content, organic functional groups of coal before and after gas production and microbial community structure were investigated by gas chromatograph, liquid chromatograph, microplate reader, Fourier infrared spectrometer and Illumina high-throughput sequencing platform. [Results] The addition of pyrite could promote the production of CH₄ in the early stage of gas production (15-22 d), while inhibited the production of CH₄ in the late stage (29-50 d). The gas production of 0.5% dosage pyrite in the early and middle stages was 48.1% higher than that of the control group, and the cumulative gas production reached 193.67 μmol/g-coal. The concentrations of VFAs and coenzyme F₄₂₀ in the experimental group were higher than those in the control group, indicating that the addition of pyrite promoted the activities of acid bacteria and methanogens in the reaction system. After adding pyrite, alcohol and phenol hydroxyl, -NH- and -NH₂ in coal were more easily utilized by microorganisms. Adding pyrite could influence the community diversity of bacteria and archaea, and greater effect on the latter. Adding a small amount of pyrite could improve the community abundance of Bacteroidota, while more pyrite could increase the community abundance of Bacillota. Pyrite had the most significant impact on Proteiniphilum, Desulfurella and JGI-0000079-D21 bacteria in the system. After addition of pyrite, the abundance of Halobacterota and Methanosarcina changed greatly. Pyrite had the most significant effect on Methanosarcina, Methanomassiliicoccus and Methanobacterium. [Conclusion] A small amount of pyrite can promote the biological gas production of coal, and affect the microbial community structure in fermentation liquid.