MSU-patented Process Can Reduce the Cost of Making Cellulosic Biofuels

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Bruce Dale (view larger image)

A patented Michigan State University process to pretreat crop waste before its conversion into ethanol means extra nutrients don’t have to be added and so cuts the cost of making biofuels from cellulose.

Cellulose in plants must be broken down into fermentable sugars before they can be turned into biofuel. The AFEX (ammonia fiber expansion) pretreatment process, developed by Bruce Dale, MAES chemical engineering and materials science researcher, uses ammonia to make the breakdown of cellulose and hemicellulose in plants 75 percent more efficient than when conventional enzymes alone are used.

“Doctoral student Ming Lau and I have shown 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.”

“The research also shows that the chemical compounds created when the stover goes through the AFEX process can improve the overall fermentation process,” Lau added. “This is at odds with the general perception that these compounds are detrimental and should be removed.”

The research was published in the Jan. 21 issue of the Proceedings of the National Academy of Sciences.

Currently, cellulose is commonly pretreated with acid to break the material down into fermentable sugars. After acid pretreatment, the resulting material must be washed and detoxified. That removes nutrients. Hence the mistaken idea that crop waste lacks the necessary nutrients for fermentation, Dale said.

Cellulosic material pretreated with the AFEX process doesn’t have to be washed or detoxified, so ethanol can be created from cellulose without added nutrients or other steps.

“Washing, detoxifying and adding nutrients back into the pretreated cellulose are three separate steps,” Dale said. “Each step is expensive and adds to the cost of the biofuel. Breaking down cellulose into fermentable sugars cost effectively has been a major issue slowing cellulosic ethanol production. Using AFEX as the pretreatment process can dramatically reduce the cost of making biofuels from cellulose.”

The next step could be a pilot plant, Dale said, perhaps at MBI International. MBI, a subsidiary of the MSU Foundation, partners with universities and companies to commercialize technology.

“There are several companies that may be interested in using this technology,” Dale said. “We are working to make the AFEX technology fit these companies’ needs.”

Dale is associate director of the MSU Office of Biobased Technologies and has a leadership role in the Great Lakes Bioenergy Research Center. The center is a partnership between Michigan State and the University of Wisconsin-Madison funded by the U.S. Department of Energy to conduct basic research aimed at solving some of the most complex problems in converting natural materials to energy.

This research is supported by the GLBRC and the MSU Research Foundation. Dale’s research also is supported by the Michigan Agricultural Experiment Station.

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