Coal Bed Methane
Over the past two decades, coal-bed methane (CBM) has emerged as an important source of fossil energy. While CBM was originally thought to be of thermogenic origin, it is now evident that microbial methanogenesis is significant in many formations (for a review see Strąpoć et al. 2011). That is, CBM is abundantly found in formations that have never been subject to conditions conducive to thermogenic methane formation. Isotopic analysis of gases from coal formations of varying maturity often indicate mixed signals that suggest both a biological and abiotic origin for CBM. Elevated paleo-temperature regimes may have constrained subsurface microbial activity in coal formations has been hypothesized to allow CBM to proceed.
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These observations have prompted investigations into the ecology of subsurface communities associated with coal formations and of the environmental factors influencing microbial activity. While prior studies collectively indicate that the requisite methanogens are present in coal seams, the physiological range of coal-bed methanogens, particularly in the context of other participating organisms, as well as the ecological conditions that ultimately lead to methanogenesis still remain unclear.
The key challenges to understanding CBM formation are therefore elucidating the mechanisms of microbial coal activation, identifying the requisite microorganisms, and determining the physiological constraints on the system. We have been applying an integrated approach to studying these questions that inovelves molecular ecology, metagenomic, functional microarray, and metabolomic tools.
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Figure 1. Example of a heatmap illustrating the relative distribution of archaeal 16S rRNA sequences in each of the core taxa with respect to sampling locations (A-J, top tree) and phylogenetic affiliation. Sequence abundances were normalized to the size of each library and the darkness of each square represents the relative frequency of sequences in each of the OTU for each of the libraries. Intensity (number of sequences) is plotted on a linear grey scale. OTUs were defined at the 10% identity level. Core taxa were defined as those taxa that account for at least 1% of the sequences in any one of the sequence libraries. The nearest neighbor dendrogram on the top was calculated using Euclidean distances based on the matrix used to generate the heat map. Letters indicate the site locations. The labels on the right correspond to different archaeal taxonomic groups: RC-I = Rice Cluster I, MM = methanomicrobiales, MS = methanosarcinales, MC = methanococcales. |
References:
Wawrik, B., M. Mendivelso, V.A. Parisi, J.M. Suflita, I.A. Davidova, C.R. Marks, J.D. Van Nostrand, Y. Liang, J. Zhou, B.J. Huizinga, D. Strapoć, and A.V. Callaghan. Field and Laboratory Studies on the Bio-Conversion of Coal to Methane. In review.
Strąpoć, D., M. Mastalerz, K. Dawson, J. Macalady, A. V. Callaghan, B. Wawrik, C. Turich, and M. Ashby. 2011. Biogeochemistry of Microbial Coal-Bed Methane. Annu. Rev. Earth Planet. Sci. 38:617-656.