STATE OF RESEARCH AND TECHNOLOGY FOR THE STIMULATION OF BIOGENIC COALBED METHANE PRODUCTION

Since the discovery that microbes can produce methane from coal on human time scales in the laboratory, there has been academic and commercial interest in determining whether these microbes could be stimulated in the field to produce methane sustainably. This study reviews the progress in stimulating secondary microbial coalbed methane production through approximately 30 years of published research by companies and academic groups.

Research groups in universities and government have made progress in determining what microbes are present, what metabolic pathways microbes use to produce methane from coal, what conditions are favorable for microbial methanogenesis, and what water and gas chemistry and isotopic signatures tell us about this process. Meanwhile, companies such as Luca Technologies, Ciris Energy, and Next Fuel Inc. have conducted lab and field experiments to investigate what can be done to increase coalbed methane production in-situ. Stimulation strategies include injecting nutrients to stimulate microbes already present in coal seams to increase or initiate methane production, introducing new microbes into coal seams (either currently productive or non-productive) to begin or enhance methane production, increasing microbial access to coal by increasing coal surface area (either chemically or physically), and solubilizing coal in order to break it down into products that are more easily utilized by microbes.

Moving forward, researchers face several challenges, such as how to best incorporate lab findings into commercial-scale field projects, determining the type and function of microbes that break down complex coal substrate into acetate, CO₂ and H₂ that methanogens use to produce methane, identifying specific constituents of the coal these microbes are utilizing, and how to best access subsurface coal deposits to implement stimulation strategies. Answers to these questions will help determine if it is economically feasible to stimulate biogenic methane production on a commercial scale.