Analysis of methane producing communities within underground coal beds

Abstract

The Powder River Basin in southeastern Montana and northeast Wyoming is the largest source of coal mined in the United States but most of the coal contained in the basin is buried too deeply to be economically accessible. These remote coal beds are dynamic zones where biogeochemical processes work to sustain a microbial ecosystem. Previous work has shown that a direct byproduct of these microbial processes is biogenic methane that can be harvested and utilized as an energy source. Methane is the principle component of natural gas and this can be used as an energy source for electricity generation, heat and transportation fuel producing only carbon dioxide and water when burned in the presence of oxygen. The only known organisms on the planet able to produce methane are classified as Archaea, microorganisms termed methanogens. However, little is known about the responsible methanogens, the conditions conducive to coal-associated methane production, nor the microbial community interactions that promote methane production. Advances in subsurface sampling and molecular techniques have provided a route to capture active microbial consortia from coal beds, but methods need to be refined in order to deal with the unique attributes of coal. Microorganisms involved in coal bed methane (CBM) formation were investigated by applying molecular methods in combination with cultivation techniques with and without nutrient supplementation to maximize methane production in batch, bench-scale incubations. Our research suggests that Clostridium species are involved with the breakdown of coal and Acetobacterium species are able to utilize substrates produced by the coal degradation. Coal and yeast extract each appear to contribute important nutrients that stimulate coal degrading communities. A better understanding of this microbial system and the biotic and abiotic parameters that control activity may permit microbially enhanced CBM production in situ to become an industrially sustainable process through the application of suitable methane stimulation strategies.