Fermentation of corn stover to carboxylic acids

This article describes countercurrent fermentation to anaerobically convert corn stover and pig manure to mixed carboxylic acids using a mixed culture of mesophilic microorganisms. Corn stover was pretreated with lime to increase digestibility. The Continuum Particle Distribution Model (CPDM) was used to simulate continuous fermentors based on data collected from batch experiments. This model saves considerable time in determining optimum operating conditions. For 80% corn stover/20% pig manure, the highest total carboxylic acid productivity was 1.81 g/(L of liquid . d) at a concentration of 21.4 g total acid/L. The highest total acid selectivity, yield, and conversion were 0.714 g total acid/g volatile solids (VS) digested, 0.550 g total acid/g VS fed, and 0.770 g VS digested/g VS fed, respectively, at a concentration of 16.0 g total acid/L. CPDM predicted the acid concentration and conversion within 13.4 and 11.6%, respectively. (C) 2003 Wiley Periodicals, Inc.