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Cellulosic Pretreatment Process Patented by Michigan State University
January 23, 2009
Michigan State University has patented a process to pretreat corn-crop waste with ammonia rather than acid that reduces the cost of making biofuels from cellulose. The ammonia fiber expansion (AFEX) pretreatment process, developed by Bruce Dale, MSU distinguished professor of chemical engineering and materials science, and doctoral student Ming Lau, uses ammonia to make the breakdown of cellulose and hemicellulose in plants 75% more efficient than when conventional enzymes alone are used. Cellulose in plants must be broken down into fermentable sugars before they can be turned into biofuel.The pair has demonstrated that "it's possible to use AFEX to pretreat corn stover (cobs, stalks, and leaves) and then hydrolyze and ferment it to commercially relevant levels of ethanol without adding nutrients to the stover," Dale said. "It's always been assumed that agricultural residues such as corn stover didn't have enough nutrients to support fermentation. We have shown this isn't so."Currently, pretreating cellulose with acid is a common way to break the material down into fermentable sugars. But after acid pretreatment, the resulting material must be washed and detoxified. That removes nutrients, leading to the mistaken idea that crop waste lacks the necessary nutrients, according to Dale. Cellulosic material pretreated with the AFEX process doesn't have to be washed or detoxified, allowing ethanol to be created from cellulose without added nutrients or other steps.The research for this process is available in the current issue of the Proceedings of the National Academy of Sciences.
