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Biofuel Two-Step

Chemical process may be an option for turning biomass into fuel.

In the mad rush to come up with quick, easy ways to turn biomass into fuel, biochemistry professor Ron Raines may have a solution. And it’s literally a solution.

Using some inventive chemistry, Raines and graduate student Joseph Binder created a unique mix of solvents and additives that can dissolve cellulose, the tough but energy-rich molecules in inedible parts of plants and trees. After its solvent bath, cellulose is converted into a platform chemical known as HMF, from which a variety of other commodities can be made. Among those end products is a potentially promising biofuel known as DMF, which is sometimes used as a gasoline additive.

While other researchers have been able to turn glucose or fructose into HMF, Raines says this process removes the need for pretreatment of cellulose-rich biomass.

“What we did was show how to do the whole process in one step, starting with biomass itself,” he says. “This solvent system can dissolve cotton balls, which are pure cellulose. And it’s a simple system-not corrosive, dangerous, expensive or stinky.”

The approach also bypasses another problem that has so far vexed biofuels researchers: lignin, the glue that holds plant cell walls together. Often described as intractable, lignin molecules act like a cage protecting the cellulose they surround. However, Raines and Binder used chemicals small enough to slip between the lignin molecules, where they work to dissolve the cellulose, cleave it into its component pieces and then convert those pieces into HMF.

After the second step of turning HMF to DMF, the overall yield for the biomass-to-biofuel process was 9 percent, meaning that 9 percent of the cellulose in the corn stover samples used in the experiment was ultimately converted into biofuel. “The yield of DMF isn’t fabulous yet, but that second step hasn’t been optimized,” says Raines.

But he is excited about DMF’s prospects as a biofuel. DMF, he notes, has the same energy content as gasoline, doesn’t mix with water and is compatible with the existing liquid transportation fuel infrastructure.

The discovery comes on Raines’s first foray into biofuels development, which was supported by UW-Madison’s Great Lakes Bioenergy Research Center. Additional support was provided through a National Science Foundation Graduate Research Fellowship awarded to Binder.

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