Cellulose Digestibility, Ethanol Yield, and Lignin Recovery from Corn Stover Fractionated by a Two-Stage Dilute-Acid and Dilute-Alkaline Process

Abstract

Dilute-acid pretreated corn stover (PCS) from NREL has been delignified using dilute sodium hydroxide extraction to see how this treatment affects enzymatic hydrolysis and simultaneous saccharafication and fermentation (SSF) of the resulting cellulose-rich fibers. The process is intended to extract and recover the lignin from stover in a relatively pure form as a co-product of the bioethanol process, while also increasing ethanol yields. The results from this treatment indicate that about 75% of the lignin can be extracted and recovered from the PCS using 0.4% NaOH at 50°C while maintaining high enzymatic hydrolysis rates. The results show that the highest SSF ethanol yield based on 9.5 FPU/g glucan cellulase loading and 6% total solids is seen with the hot-water insoluble PCS (HWI-PCS) treated with 0.4% NaOH at 50°C for 30 min. This sample has an overall ethanol yield of 77% and an ethanol concentration of 22 g/L after 120 hours.