Patent ID: 7919290

Claim:
A method of producing methane comprising: collecting combustion exhaust gas from a hydrocarbon fuel combustion process; separating O 2 from CO 2 in the exhaust gas to generate a CO 2 -rich anaerobic exhaust gas fraction; feeding the CO 2 -rich anaerobic exhaust gas fraction to a fermentation mixture containing methanogenic microorganisms; feeding a reduced substrate selected from the group consisting of H 2 and organic material and a combination thereof, to the fermentation mixture; and producing a biogas comprising methane in the fermentation mixture by the anaerobic fermentation of methanogenic microorganisms; fractionating the biogas into a methane-rich fraction and a carbon dioxide-rich fraction; and processing the methane-rich fraction for energy; wherein feeding the CO 2 -rich anaerobic exhaust gas fraction to the fermentation mixture increases methane production in the fermentation mixture.