SCALE-UP OF MICROBIALLY ENHANCED COALBED METHANE STRATEGIES USING A COLUMN UPFLOW REACTOR

Because the subsurface is difficult to access, making it expensive to run experiments there, subsurface environments are inherently challenging to study in situ. Therefore, it is necessary to mimic these environments in laboratory microcosm studies to increase the understanding of the abiotic and biological processes, pathways, and kinetics. Batch reactors can provide insights into specific processes, pathways, and engineering strategies, however comparability to the in situ conditions can be restricted due to limited substrate availability or accumulation of byproducts that may influence reactions or metabolisms and other restrictions. Flow reactors can overcome some of the batch limitations and allow for greater understanding of in situ conditions, especially when developing techniques for subsurface engineering.

We developed upflow column reactors to mimic in situ flow conditions in a methane producing coal bed. This system is designed to maintain an anaerobic environment for applications in upscaling microbially enhanced coalbed methane (CBM) strategies. The coal-packed columns create surrogates for the subsurface coal seams where CBM producing microbial processes take place. Gas traps capture all gases produced for quantification and analysis, and sampling can occur at various points throughout each reactor system. Each iteration of the system has been tested with a monoculture of Methanosarcina acetivorans to ensure anaerobicity and to collect and quantify produced gases, primarily methane. The system is currently being used to apply CBM enhancement strategies that have been developed in batch systems to increase the understanding of the stimulation process and develop strategies for a field-scale demonstration.

These upflow reactors can be operated under different flow conditions and can be easily modified for investigations of other subsurface environments, especially where gases or volatile compounds are of interest.