(726g) Coal-to-Biomethane Potential of Microbial Consortia Native to Coal Seam Formation Waters

Laboratory culture experiments have demonstrated that microbial consortia native to coal seam formation waters are capable of producing methane given native coal as the primary substrate.  The field application of such a process has the potential to generate new natural gas reserves in situ in real time.  Given the diversity in coal rank, type, and depositional setting, a fundamental understanding of this natural microbial process is needed to develop site-specific stimulation treatments.  Multiple samples taken from the Surat Basin of Queensland, Australia were collected and screened for methanogenic activity using native Walloon coal as the sole carbon and energy source.  In vitro methanogenic rates and yields were 0.24 m³/ton/day and 6.1 m³/ton, respectively; if our average laboratory rate could be extrapolated to the field, the Surat Basin mean gas content of 3.5 m³/ton could be replenished in two weeks.  Various coal weights in a constant growth medium volume were subjected to culture tests; results indicate that methanogenesis yields in our system were limited by a coal substrate, as opposed to a supplemental nutrient.  While the interior coal matrix holds additional biomethane substrate, only the coal surface is bioavailable in the short term.  With this in mind, experiments designed to enhance microbial surface interactions and coal bioavailability showed that both physical and chemical treatment of coal enhances methanogenesis rates and yields.  Microscopic imaging has revealed microbial coal surface interactions, which may play a critical role in coal-to-methane biodegradation.  The CO₂ reduction pathway was active for these consortia, which may have implications for CO₂ sequestion in these coal seams.  Our Walloon coal substrate was separated into vitrain and dull lithotypes, and the coal-to-methane activity was quantified as a function of maceral type; the results were used to hypothesize potential coal substrates and possible scale-up limitations.   Finally, a genomic study using pyrotag sequencing from both raw and enriched methanogenic communities was used to identify the most active and critical consortium members.