On Comparison Between Fungal and Bacterial Pretreatment of Coal for Enhanced Biogenic Methane Generation

Owing to better understanding of subsurface geochemical carbon recycling and real-time active methanogenesis in major coal basins around the globe, substantial share of subsurface methane generation is attributed to biogenic origin. Since coal, being complex geopolymer, does not appear to be a favorable microbial substrate, enhancement in biogenic methane yield depends on its degradation into simpler organic substrates. This review puts forward a comparative analysis of fungal and bacterial pretreatment for determining the extent of facilitation in initial degradation of coal, which is still rate limiting step in overall conversion of coal into methane. Primarily, the initial fungal degradation of coal differs from bacterial pretreatment of coal in terms of the nature of released organics. On the basis of previous reports, fungal pretreatment of coal yields, majorly, polyaromatic hydrocarbons, however, bacterial pretreatment results in the generation of mixed organics pool of aromatics and aliphatics. The presence of aliphatics may be prospected for achieving greater conversion rates of coal conversion into methane. Considering the criticality of preliminary degradation of coal and associated issues, the fate of commercial biogenic methane generation would be dictated by the factors pertaining to geological considerations and reservoir geology, chemistry of coal and associated water tables, geomicrobial considerations and economic viability.