Wisconsin researchers convert cellulose into biofuels

By Susanne Retka Schill
Web exclusive posted Feb. 20, 2009, at 10:19 a.m. CST

Wisconsin researchers have developed a two-step chemical method to convert the cellulose in untreated biomass into the biofuel 2,5-dimethylfuran (DMF). The key to the process is the first step, in which cellulose is converted into the platform chemical 5-hydroxymethylfurfural (HMF) from which a variety of commodity chemicals can be made.

"Other groups have demonstrated some of the individual steps involved in converting biomass to HMF, starting with glucose or fructose," said Ronald Raines, a University of Wisconsin professor in the departments of biochemistry and chemistry. "What we did was show how to do the whole process in one step, starting with biomass itself." Raines and UW graduate student Joseph Binder, developed a special mix of solvents and additives with an exceptional capacity to dissolve cellulose. A patent is pending on the process.

"This solvent system can dissolve cotton balls, which are pure cellulose," Raines said. "And it's a simple system - not corrosive, dangerous, expensive or stinky."

Using the solvent method, by using chemical compounds small enough to slip between the lignin molecules, the lignin is bypassed. Rather, the solvent dissolves the cellulose, cleaves it into component pieces and then converts those pieces into HMF.

In step two, Raines and Binder converted HMF into DMF, which is used as a gasoline additive and has the same energy content as gasoline, but doesn't mix with water and is compatible with the existing liquid transportation fuel infrastructure. Taken together, the overall yield for the two-step biomass-to-biofuel process was 9 percent, the researchers reported.

"The yield of DMF isn't fabulous yet, but that second step hasn't been optimized," Raines said. In addition to corn stover, Raines and Binder have tested their method using pine sawdust, and they're looking for more samples to try out. "Our process is so general I think we can make DMF or HMF out of any type of biomass," Raines said.

Raines' first biofuels development project was supported by the Great Lakes Bioenergy Research Center, a U.S. DOE Bioenergy Research Center located at the University of Wisconsin-Madison. Additional support was provided through a National Science Foundation Graduate Research Fellowship awarded to Binder.

A paper describing the process was published in the February issue of the Journal of the American Chemical Society.