SusChEM: Collaborative Research: Biogenic Methanogenesis and Biodegradation of Organic Matter in Coals

Indiana University, Bloomington IN

Investigators

Abstract

Broader significance. Natural gas, composed primarily of methane, provides approximately a quarter of the total energy in the US and is therefore a major cornerstone of the US economy. Coalbed methane (CBM) provided about 9% of the total domestic natural gas production in 2010 and the U.S. Energy Information Administration (USEIA) estimates that CBM will continue to be an important part of the US energy portfolio through 2035 and in subsequent years. Through recent work and observation of deep coal-bearing sedimentary basins, it has become obvious that microbes are controlling the generation of this methane, and yet surprisingly little is known about what controls these microbes. There is growing public, regulatory, and industrial interest in recovery of natural gas from unconventional sources because of the continued need to develop alternative energy sources and the publicity associated with gas recovery from such sources, especially hydraulic fracturing (fracking). CBM production is estimated to remain constant through 2035, averaging 1.8 trillion cubic feet (CF) per annum. Based on a current price of $4.57/MMBtu and the USEIA 2013 average heat content for natural gas (1.025 MMBtu/103 CF), CBM production has a value of approximately $8.43 billion/year. The investigators on this project propose to identify the component organisms in the communities that generate CBM, and importantly, what influences their metabolic processes leading to methane production. Armed with this knowledge it may be possible to increase the biogenic production of CBM, and provide a significantly more stable and profitable fuel resource. Enhancing current biogenic CBM production by even a modest 0.1% would, based on the above annual production value, would have an economic return of $8.43 million/year. This research is supported via the NSF Sustainable Chemistry, Engineering, and Materials (SusChEM) initiative. Technical description. The proposed research focuses on characterizing the genotypes and regulatory networks that mediate CBM-associated microbial metabolism in the subsurface. It seeks to build on our initial biogeochemical investigation of changes in hydrocarbon composition that accompany microbial incubations with coal extracts by elucidating the microbial community structure and functional regulation in bioreactor enrichments under controlled laboratory incubations. Specifically, we will determine the influence of low concentrations of terminal electron acceptors on microbial community dynamics associated with increased organic matter degradation and altered rates of methane production. We will describe the genotypes of key components of each system, and determine how their relative abundance shifts over time and across experimental manipulations of terminal electron acceptor concentration. We will also map the transcription of their genes in response to experimental conditions and time, to determine the potential influence on the metabolism of the complex organic carbon in coals. These data, in concert with the physic-chemical parameterization of each bioreactor experiment will be combined to generate a compartmentalized metabolic model of the microbial assemblage. This model will be a first of its kind, laying the groundwork for modeling the metabolism of more complex systems.