How biology will help fill your fuel tank

Going for the gut
Researchers such as Caltech's Simon have been analyzing microbes extracted from the termite's digestive system, looking for the enzymes that enable the bugs to turn wood cellulose into sugars. So far, hundreds of promising enzymes, including glycohydrolases and cellulases, have been found.

The project, which is being conducted by Diversa and Caltech as well as the U.S. Department of Energy's Joint Genome Institute and Costa Rica's National Biodiversity Institute, has turned up challenges as well, Simon said.

"The problem with biology is that it's slow, so it takes an awful lot of termites an awful lot of time to digest a 2-by-4," he said. "There are bacteria that make essentially fuel oil, but the process is very inefficient."

The goal isn't to enlist the termites or even the bacteria per se, but to unravel the chemical pathways that the microbes use — then adapt those biological processes for more efficient artificial techniques.

"In general, microbes play only one part in the process," Simon said. "Nobody can think of a superbug that can eat your table."

Brave new world
Another avenue for research is breeding cellulosic plants that are more amenable to the conversion process. That was part of the impetus behind the recent sequencing of the poplar genome — the first tree to have its genetic code fully analyzed. The genes of trees or woody plants could conceivably be tweaked to make the sugars within the cellulose easier to get at.

However, Somerville cautioned that this type of brave new world was still far off: "It's impossible that any genetically modified plants would be available before 15 years from now."

By that time, he expects the biofuels industry to be running at full speed. "Within 10 to 12 years we'll have a very substantial cellulosic ethanol industry," he said. From his point of view, the big problem may not be producing the ethanol, but having enough cars that are capable of using high-ethanol fuel blends. Currently, less than 3 percent of the nation's 250 million highway vehicles are capable of using an 85 percent ethanol blend.

Even if cellulosic ethanol production increases on a pace to replace a third of America's gasoline consumption, as the Department of Energy hopes, the dearth of ethanol-friendly vehicles could pose a "large infrastructure problem," Somerville said.

"The fleet needs to turn over," he said.

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