Continuous biomass fractionation process for producing ethanol and low‐molecular‐weight lignin

Abstract

AbstractA 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 hemicellulosic sugars and lignin, respectively. Process optimization was conducted using corn stover as feedstock in a continuous pilot‐scale unit, with the goals of efficient hemicellulose and lignin hydrolysis for the countercurrent first and cocurrent second stage, respectively. Countercurrent prehydrolysis in an extruder is a novel feature of the process. Autohydrolysis at 210°C followed by NaOH (0.06 g/g biomass) catalyzed delignification at 220°C was determined to be optimal. Economic feasibility of the process for ethanol production was compared 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 with additional stover. The minimum ethanol selling price, calculated following the 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 potential. © 2009 American Institute of Chemical Engineers Environ Prog, 2009