CULTURE STUDIES ON THE CONVERSION OF CORN STOVER TO METHANE

The anaerobic fermentation of corn stover to methane has been demonstrated to be a viable process for the conversion of this agricultural residue to a useable form of energy. With fresh cow manure as the original inoculum, digestors were operated over a period of four years at retention times varying between 20 and 100 days. A first order reaction rate constant of 0.045 per day was determined as was a maximum conversion at infinite retention of 73 percent.;Several bacteria were examined to determine their ability to produce better conversion of sugars and corn stover to methanogenic substrates. Clostridium butyricum, which is not found in the normal flora of the rumen, performed the best from the group of bacteria studied. This organism was placed in a semi-continuous digestor in order to compete with other bacteria for the sugars produced from enzymatic hydrolysis of the corn stover. A first order reaction rate constant of 0.0534 per day was determined after the addition of C. butyricum, this represents an 18.7 percent increase in the rate constant. For a process converting corn stover to methane, where the digestor tanks account for two-thirds of the capital costs, this improvement results in a 12.5 percent savings in the capital investment for this facility.