Renewable chemical ready for biofuels scale-up

The technology could produce ethanol at a cost savings of roughly 10 percent

Using a plant-derived chemical, UW-Madison researchers have developed a process for creating a concentrated stream of sugars that’s ripe with possibility for biofuels.

“With the sugar platform, you have possibilities,” says Jeremy Luterbacher, a postdoctoral researcher and the paper’s lead author. “You’ve taken fewer forks down the conversion road, which leaves you with more end destinations, such as cellulosic ethanol and drop-in biofuels.”

Funded by the National Science Foundation and the U.S. Department of Energy’s Great Lakes Bioenergy Research Center(GLBRC), the research team has published its findings in the Jan. 17, 2014 issue of the journal Science, explaining how they use gamma valerolactone, or GVL, to deconstruct plants and produce sugars that can be chemically or biologically upgraded into biofuels. With support from the Wisconsin Alumni Research Foundation (WARF), the team will begin scaling up the process later this year.

Because GVL is created from the plant material, it’s both renewable and more affordable than conversion methods requiring expensive chemicals or enzymes. The process also converts 85 to 95 percent of the starting material to sugars that can be fed to yeast for fermentation into ethanol, or chemically upgraded furans to create drop-in biofuels.

To demonstrate the economic viability of this advance, Luterbacher needed to concentrate the sugar, remove the GVL for reuse, and show that yeast could successfully generate ethanol from the sugar stream.

“Showing that removing and recycling GVL can be done easily, with a low-energy separation step, is a little more of an achievement,” says Luterbacher. “By feeding the resulting sugar solution to microorganisms, we proved we weren’t producing some weird chemical byproducts that would kill the yeast, and that we were taking out enough GVL to make it nontoxic.”

“What’s neat is that we can use additives to make the solution separate,” says Luterbacher. “It becomes like oil and vinegar.”

Their additive of choice: liquid carbon dioxide.

“It’s green, nontoxic and can be removed by simple depressurization once you want GVL and solutions of sugar to mix again. It’s the perfect additive,” Luterbacher says.

An initial economic assessment of the process has indicated the technology could produce ethanol at a cost savings of roughly 10 percent when compared with current state-of-the-art technologies.

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