Farm- and Industrial-Scale Biomass Fermentation Studies. Annual Progress Report, 1 September 1980-31 December 1981

摘要

The overall objective of this three-year research project is to study the reaction kinetics of the anaerobic digestion process in both batch and continuous flow reactors. Anaerobic digestion of corn stover in continuous laboratory reactors has been found to follow first-order kinetics. A large number of microorganisms were screened for their ability to provide cellulolytic activity or produce methane intermediates. Clostridium butyricum was found to be the most promising. Batch studies involving culture enhancement with C. butyricum have shown a 42 percent increase in methane production. In continuous culture, enhancement with C. butyricum increases the first-order rate constant by 20 percent. These improvements in the reaction rate translate into significant reductions in capital cost for industrial processes. The design of a 3-ton-per-day demonstration unit to produce methane from corn stover has been completed. This design is based upon standard kinetics with two reactors in series. The capital cost for this unit is estimated to be $600,000 with annual operating cost of $200,000. Inoculation and agitation studies were conducted in the laboratory to determine the appropriate inoculation ratio for corn stover and the agitation requirements for batch farm scale systems. Agitation studies have shown that continuous agitation in batch laboratory reactors is unnecessary. Periodic agitation of only 10 minutes per day is necessary to prevent scum formation and promote mass transfer. The farm demonstration unit continued to operate to produce methane and electricity for farm use. The unit operated with 75 percent overall energy efficiency and can produce methane for $1.80 to $6.50 per 10 exp 6 Btu, and electricity for $.04 to $.13 per kWh, depending upon the biomass and capital charges. (ERA citation 08:043439)