Energy does grow on trees

September 14, 2006

GAINESVILLE, Fla. — Road warriors, it may be time to hug a tree. In a few years, you could find yourself filling your gas tank with ethanol derived from specially bred black cottonwood trees — and at prices not seen since the 1990s.

Researchers from the University of Florida’s Institute of Food and Agricultural Sciences, in conjunction with 33 scientific institutions worldwide, have mapped out the genome of the black cottonwood tree, a prime candidate for use in new “biomass” fuel production methods that could someday cut our reliance on petroleum and reduce pollution.

The research, featured on the cover of the Sept. 15 issue of the journal Science, identifies genes that can be specifically selected through traditional plant breeding to produce trees with the perfect qualities for efficient conversion into biomass fuel.

For example, one method developed by UF researcher Lonnie Ingram uses genetically engineered bacteria to convert substances in the tree’s cell walls into ethanol and other useful chemicals. The work isn’t just pie-in-the-sky idealism. He is collaborating with Massachusetts-based Celunol Corp. to build a 20-million-gallon biomass-to-ethanol plant in Jennings, La., expected to be operational by spring 2007.

The genomic research revealed 93 genes that help control the production of these cell wall substances. By breeding trees with just the right variation of these genes, researchers can produce the ideal energy cash crop that could help replace as much as half of the oil imported into the United States.

“We are not talking about a genetically modified organism,” said John Mark Davis, one of three UF researchers who collaborated on the project. “This is a wild tree, and there’s enough genetic variation already out there for us to get the plant we want without direct genetic manipulation.”

In ideal environments, the trees already grow rapidly, as much as 12 feet in a year, and can reach maturity in as little as four years. But the genome could also mean breeding trees that respond well to less than ideal environments. The result could be a new type of crop that could be grown through the somewhat economically depressed Midwestern and Pacific Northwest states, said UF researcher Matias Kirst.

Of course, vast farms of the black cottonwood would come with another advantage other than cleaner-burning, cheaper fuel—the trees, like all plants, absorb the most significant greenhouse gas, carbon dioxide. They then store the carbon in their stems, roots and the soil.

“Basically, you would have a fuel source for our cars that, in the big picture, could help capture almost as much carbon dioxide as it produces,” said UF researcher Gary Peter. “That would go a long way in slowing the biggest driver of global warming.”

The effort to sequence the black cottonwood’s genome was funded by the U.S. Department of Energy and included institutions such as Oak Ridge National Laboratory, the University of British Columbia and Ghent University in Belgium. It is part of a broader effort to replace 30 percent of the fuel burned in the U.S. with biomass fuels by 2030.

This is only the third plant genome to be sequenced, and contains nearly four times more genetic information than that of either rice or Arabidopsis thaliana, a flowering weed. More than 45,000 genes were identified—that’s twice the number identified in the human genome, which is six times larger than that of the cottonwood.

There is still much work to do before the genome is completely understood. Computers have helped identify which genes may be responsible for certain characteristics, but trees with those specific genes must still be grown, tested and harvested. Peter, Davis and Kirst are growing thousands of trees with hundreds of different genetic variations in an environmentally controlled greenhouse.

“We’ve done the groundwork, now we need to do the growing,” Davis said. “And that takes time.”