Experimental study on the mechanism of biological hydrogen sulfide generation from organic sulfur-rich coal

Whether of primary or secondary origin, the presence of hydrogen sulfide (H2S) in coalbed methane (CBM) is commonly attributed to sulfate reduction facilitated by sulfate-reducing bacteria (SRB). However, the sulfate content in high-sulfur coal is exceptionally low, insufficient to function as a substrate for sulfate-reducing bacteria (SRB). In this study, an anaerobic digestion experiment was conducted with high-organic-sulfur coal collected from the Late Permian Longtan Formation in Guangxi Province as both the carbon and sulfur sources. The formation mechanism of H2S is revealed from the evolution rules of gas components, liquid organic matter, and microbial communities during the anaerobic digestion process. The findings indicate three distinct mechanisms contributing to the biological formation of H2S in coal seams: firstly, the degradation of readily degradable organic sulfur in coal by microorganisms possessing denitrification capabilities, primarily attributed to the activity of the Wolinella; secondly, The synergistic consortium involving SRB, Pseudomonas spp., and denitrifying Thiobacillus species mediates SO42- reduction and H₂S biogenesis through cross-metabolic interactions; thirdly, Methylotrophic methanogens employ the methyl groups of organic sulfides to produce CH4 and H2S simultaneously. Therefore, biological H2S can be generated under the presence of a sulfur source, appropriate temperature, and conducive environmental conditions. This comprehension will contribute valuable insights to the discourse on the generation and enrichment patterns of H2S in natural coalbed methane. Additionally, it can offer practical avenues for the prevention and control of H2S through technological approaches.