Making ethanol out of biodiesel byproducts

Rice University researchers say that microbes can help us get more biofuel for the buck.

Microorganisms can be used to metabolize glycerol--one of the primary byproducts in converting vegetable oil or animal fat into biodiesel--into high-value products, said Ramon Gonzalez, the William Akers Assistant Professor in Chemical and Biomolecular Engineering.

Gonzalez and a group of students, for instance, have identified a process in which Escherichia coli, in an oxygen-free environment, will convert glycerol into ethanol. The strain of E. coli currently being used in the experiments isn't genetically modified or enhanced, which could further enhance yields.

The glycerol could also be converted into different types of industrial acids, which could even be more profitable than ethanol.

The research, which is attracting investors and companies interested in licensing the technology, could help take some of the risk out of the growing biofuel business. Start-ups and established companies are sinking hundreds of millions of dollars into building biodiesel refineries and ethanol plants.

Unfortunately, turning a profit isn't easy, even with subsidies that range from 50 cents to $1 a gallon. Both biodiesel and ethanol are dependent upon feedstocks such as palm oil, sugar cane, and corn, which can fluctuate wildly in price and erode margins. Corn has doubled in price, from $2 a bushel to $4 a bushel, in the U.S. in the past year and whacked the profits of ethanol producers. Increased biodiesel demand is expected to make cooking oil prices spike in the coming years.

To remain economically viable, these companies have to be able to sell their byproducts. In biodiesel, that's become tough to do because of the sudden glut in supply. Glycerin (also known as glycerol), which is sold to cosmetics companies, went for about 25 cents a pound 18 months ago, said Gonzalez. Now it sells for about 2 to 3 cents a pound--when sellers can find buyers. For every 10 pounds of biodiesel produced, refiners are left with about a pound of glycerin. (Oil in industrial processes gets measured in pounds.)

"This could help biodiesel a lot," he said. "When they design their economic models, they count on selling the glycerin."

Ethanol produced from glycerin could also be more economical than producing it out of corn, the main feedstock for ethanol in the U.S., or than cellulosic ethanol, which is made out of wood chips and waste vegetable matter. Gonzalez hopes a prototype production process for making glycerin ethanol will be in place by the end of the year, meaning it could come to market earlier than cellulosic ethanol. Mascoma will try to open a small cellulosic plant by early 2008 and New Zealand is investing in the concept. But most believe cellulosic ethanol is still at least a few years away.

During the past three years, microorganisms have begun to be more actively enlisted for industrial production. Microbes, after all, are essentially miniature chemical factories: they ingest materials, break them down with enzymes and turn out byproducts. Brewers and pharmaceutical manufacturers have exploited microorganisms for years, but now they are being drafted for other types of work. Some companies have also figured out ways to re-create microbial processes in the lab in the growing field of synthetic biology.

Cambrios Technologies has come up with a biologically inspired enzyme that can be used to add insulating layers to semiconductors. Meanwhile, companies such as LS9, Gevo and Synthetic Genomics are trying to harness microbes for energy production.

And why use E. coli, the microorganism usually associated with stomach pains? It's one of the most extensively studied microbes, and several techniques for genetic modification have already been developed with it. Gonzalez and others call it the workhorse of microbiology.

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