About seven percent of the global annual methane emissions originate from coal mining. Furthermore, during the last decade the use of coal bed methane has come into focus of the power producing industry. In Germany, the gas from active and abandoned mining areas is increasingly used for heat and power production, especially after the introduction of the "renewable energy law" in 2000. In many coal reservoirs worldwide, the analysis of the stable carbon isotopic composition of methane showed that the produced methane is a mixture of thermogenic and biogenic origin. However, the timepoint for the formation of the latter fraction is not known. Interestingly, time series of measurements show an increasing proportion of the biogenic, microbially produced methane during the last years, indicating a recent origin.
Incubations of wood and coal samples from abandoned reservoirs showed over a period of nine months constant and significant microbial methane production rates. The stable carbon isotope signatures of the produced methane were in a similar negative range as the values of the gas samples collected in situ in the reservoir. Fluorescence-in-situ-hybridisation (FISH) revealed the presence of different types of methanogenic Archaea. These could be further enriched with common methanogenic substrates, like acetate, hydrogen/carbon dioxide or methanol. Detailed molecular studies are currently carried out to identify the microorganisms involved in this scientifically as well as economically very important process.
Beckmann, Sabrina (2011) Dissertation: Microbial Methane Formation in Abandoned Coal Mines in the Ruhr Basin of Germany
Beckmann S, Lüders T, Krüger M, von Netzer F, Engelen B, Cypionka H (2011) Acetogens and acetoclastic methanosarcinales govern methane formation in abandoned coal mines. Appl. Environ. Microbiol. 77:3749–3756
Beckmann S, Krüger M, Engelen B, Gorbushina AA, Cypionka H (2011) Role of Bacteria, Archaea and Fungi involved in methane release in abandoned coal mines. Geomcrobiol J 28:347-358
Krüger M, Beckmann S, Engelen B, Thielemann T, Cramer B, Schippers A, and Cypionka H (2008) Microbial methane formation from hard coal and timber in an abandoned coal mine. Geomicrobiology J. 25:315-321
Thielemann T, Cramer B, and Schippers A (2004) Coalbed methane in the Ruhr Basin, Germany:a renewable energy resource? Organic Geochemistry 35, 1537-1549