Urea-pretreated corn stover: Physicochemical characteristics, delignification kinetics, and methane production

Solids loading is a key factor in aqueous or gaseous ammonia production from urea. Methane production from urea-pretreated corn stover, as well as the physicochemical characteristics and delignification kinetics of the corn stover, were investigated with four solids loading values (10%-70%) and five ratios of urea to corn stover (1:100-7:10) at 35 degrees C for 6 weeks. A 1:20 ratio of urea to corn stover was optimal for achieving high lignin removal with <= 50% solids loading, and 7:10 was optimal with 70% solids loading. Under the two optimal conditions, 85.56% and 82.35% of cellulose and 85.76% and 85.49% of hemicellulose were retained. The maximum lignin removal rates of 69.67% and 68.27% and methane production of 294.70 and 292.56 L/kg volatile solids (VS) were achieved, respectively. The delignification kinetics of the urea-pretreated corn stover conformed to three first-order reactions. Most of the lignin was degraded within the first 3 weeks.