Continuous Biomass Fractionation Process for Producing Ethanol and Low-Molecular-Weight Lignin

A continuous biomass 'fractionation process for producing ethanol and low-molecular-weight lignin was developed, and its economic feasibility was evaluated. The two-stage process fractionates biomass into three streams a solid cellulose stream and two liquid streams containing mostly bemicellulosic sugars and lignin, respectively. Process optimization was conducted using corn stover as feedstocks in a continuous pilot-scale unit, with thhe goals of efficient hemicellulose and lignin hydrolisis for the countercurrent first and cocurrent second stage, respectively. Countercurrent prehydrolysis is an extruder is a novel feature of the process. Autohydrolysis at 210 degrees C followed by NaOH (0.06 g/g biomass) catalyzed delignification at 220 degrees C was determined to be optimal. Economic feasibility of the process for ethanol production was commpared to that of the National Renewable Energy Laboratory (NREL; Golden, CO) process Major differences between the two scenarios are that the Purevision process generates lignin as a sellable output but needs to replace the lost fuel value of the lignin withh additional stover. The minimum ethanol selling price, calculated following thhe NREL protocol, is projected to be lower for the Purevision process ($0.94/gal) than that for the NREL process ($1.07/gal)-the differential depending on lignin selling price-indicating a process with commercial potentia. (C) 2008 American Institute of Chemical Engineers Environ Prog, 28: 89-99, 2009