Two-stage acid hydrolysis of biomass

Biological conversion of biomass into fuels and chemicals requires hydrolysis of the polysaccharide fraction into monomeric sugars. This hydrolysis can be accomplished enzymatically or with mineral acids. A two-step dilute and concentrated acid hydrolysis process has been developed that utilizes mild conditions and nominal quantities of acid. The use of two stages minimizes the decomposition of pentoses while allowing the high yields possible from use of concentrated acid. This process is described and the design and economics presented for conversion of corn stover. Acid recycle in the prehydrolysis step results in a 250% increase in the sugar concentration. The use of acid recycle would reduce the investment and operating cost for this process by about 20%.