| The purpose of this research was to enhance the rate and amount of biogenic coal methane production from coal. Oxidized coal, un-oxidized coal, and coal extracts were used to examine whether the rate and amount of biogenic methane production from coal can be enhanced by solubilizing coal with chemicals or amending with an external inoculum or electron donors.;Oxidized coal samples, Canyon coal (Powder River Basin (PRB), Wyoming) and Durango coal (Durango, Colorado), did not support methane production using an external culture. Methane production from oxidized coal was affected by competition between methanogens and sulfate-reducing organisms, by the limited native microbial community existing on the oxidized coal, and by inhibition of fermentative processes, presumably arising from soluble acidic compounds released from oxidized coal.;Chemicals (HNO3, NaOH, H2O2 and KMnO 4) could solubilize oxidized and un-oxidized coal and increase dissolved organic carbon. Methane was not detected from cultures receiving coal extracts during subsequent testing.;Organisms present on coal samples (Big George coal and Smith coal, PRB) readily consumed amended substrates (hydrogen, cysteine, and ethanol) to produce methane in preference to using coal constituents. The hydrogen consumption and biomass growth rates for a coal microbial community could be simulated with a Monod-type model. Amending an enriched inoculum could decrease the lag time of methane production from un-oxidized coal, but could not enhance the amount of methane production from coal. Additionally, amendments lead to rapid methane production, but this methane production did not exceed the theoretical methane production from the amendments. The amounts of amendments added and subsequent methane production should be carefully tracked using mass balances on chemical oxygen demand to evaluate the extent of enhancement. Without this information, the amount of methane desired specifically from coal constituents cannot be unequivocally determined.;While methane can be biogenically produced from sub-bituminous coal, the rate and amount of production are small. The addition of amendments enhances methane production, but primarily due to the biotransformation of the amendments and not coal constituents. Methods to convert the coal matrix to more readily degraded constituents are likely required for economically viable implementation of biogenic coal to methane processes. |
