It’s a Biofuel, It’s a Rubber Glove…No, It’s Guayule!

Federal researchers have been calling Guayule the biofuel plant of the future for a while now, and it looks like they’re ready to bet the ranch on it. Well, maybe not the whole ranch, but the Department of Energy’s high-tech funding agency, ARPA-E, has just awarded $5.7 million to a new partnership that will develop guayule biofuel. The project also includes related research into developing sweet sorghum for biofuel.

Guayule makes rubber, too

If you haven’t ever heard of guayule before, you will soon. The weedy, drought-tolerant, fast-growing plant is native to the U.S. and it is already being exploited as a source of natural rubber for gloves and other products by an Arizona company called Yulex. The tire company Bridgestone is beginning to eyeball it as a source of natural rubber for tires, too (for that matter, Ford is looking into dandelion rubber — but that’s another story).

Guayule rubber is close cousins with the conventional natural rubber harvested from the hevea tree (aka the “rubber tree”), with one big advantage: it lacks the proteins that can trigger an allergic reaction in some people.

A green biofuel twofer for guayule

Aside from its biofuel-friendly nature as a non-food crop that can be grown on marginal lands, guayule is attractive because its use in rubber production puts it on a potentially more firm commercial footing than crops that are grown exclusively for biofuel.

After being harvested and processed for latex extraction, guayule produces leftover “bagasse” in the form of stems and branches. When dried and powdered, guayule bagasse yields about the same Btu per pound as charcoal.

In that context, it’s not surprising that after more than a decade in the natural rubber business, Yulex announced earlier this year that it would be exploring ways to commercialize its guayule bagasse for biofuel.

The company is pursuing a couple of different avenues, including supplying bagasse to an electric utility as a biomass feedstock, and working with USDA on converting it to ethanol and other liquid fuels.

ARPA-E and guayule

The ARPA-E grant is focused on another aspect of guayule, which is its ability to produce relatively high amounts of farnesene in its stems and branches. Farnesene is a natural oil that can be extracted from plants at a relatively low cost and converted to liquid fuel.

In terms of biofuel yield per acre, high-farnesene plants like guayule have a significant potential advantage over conventional biofuel crops that mainly produce oil in their seeds, especially food crops like canola, soy, and corn.

The grant partnership, which will focus on genetically engineering guayule to produce more farnesene, will be led by the Chicago-based green energy company Chromatin Inc. A key role will be played by Ohio State University’s Ohio Agricultural Research and Development Center, and other partners include the San Diego company Allylix and Kansas State University.

The ARPA-E project includes sweet sorghum because it also produces farnesene, though in relatively small amounts compared to guayule. ARPA-E anticipates that the guayule research model can be transferred to sorghum, saving time as well as money.

Image courtesy of Biswarup Ganguly via wikimedia

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