The Next Generation of Biofuels

Companies are poised to go commercial with gasoline substitutes made from grass, algae and the ultimate source: engineered microorganisms

That is why a second group of scientists—including J. Craig Venter, the entrepreneur and biologist whose Institute for Genomic Research in Rockville, Md., played a key role in mapping the human genome—argues for a bolder approach. These researchers believe that the best biofuels will bypass crop plants—cutting out the middleman entirely—relying instead on algae and a few microorganisms that have a plantlike knack for directly and efficiently turning sunlight into energy through photosynthesis. The scheme has yet to be proved on a large scale, however. “I haven’t seen anyone really do a fair calculation of what algae can do,” Keasling notes, “and until I see that, I’m not convinced.”

Regardless of the method, scientists will have to improve on Mother Nature to make a successful biofuel, tinkering with existing microorganisms or even building brand-new ones. Dozens of start-ups are manufacturing fuels from novel strains of yeast, algae and bacteria. Several promise that by 2011 they’ll have made gasoline or diesel substitutes that can be pumped directly into cars. And although these biofuels will probably first be supplied preblended with traditional gasoline or diesel—much the way E10 is today—one day we may use them alone and say good-bye to petroleum-based gasoline forever.

From BioWillie to the Q Microbe
Keasling’s idea of fun is making microorganisms do strange things. “I want to see how much we can tweak cells and probe the limits of nature,” he says. Microbes are perfect little factories because they can be engineered to perform practically any chemical reaction. They also replicate on their own, whereas chemical reactions in the lab require a scientist’s near-constant attention. Since Keasling joined the Berkeley faculty in 1992, he has engineered bacteria to produce lifesaving malaria drugs and biodegradable plastics and to break down a range of environmental contaminants.

Now Keasling has turned his attention to energy. In December 2008 he and his colleagues at the Emeryville, Calif.–based Joint BioEnergy Institute, one of three new Department of Energy research centers developing sustainable biofuels, modified a common yeast strain so that it could generate digestive enzymes normally used by four different microorganisms. The jazzed-up yeast could digest more of the cellulosic plant material, pumping out up to 10 times as much biofuel.

Keasling grew up on a corn farm in a small Nebraska town, so he understands the downside of corn-based ethanol. Farmers make the fuel by chemically treating corn kernels to isolate the sugars and then feeding the sugars to yeast, which digests them and secretes ethanol.Not only do the corn husks and stalks go to waste, but ethanol production has driven up the price of the corn that is used for food by reducing its availability. Environmentalists have also become critical of using corn, sugarcane and other agricultural crops because they typically need lots of fresh water, fossil fuel–rich fertilizer and land to grow. Keasling is designing new forms of yeast, bacteria and archaea—three types of single-celled organisms—with special digestive systems that can break down the complex starches known as cellulose that are found not only in cornstalks but in many grasses, shrubs and trees. Because these plants aren’t food crops, they won’t detract from the food supply. If we ever hope to replace a large fraction of gasoline with biofuels, “it’s going to have to be through plants,” he says.

Keasling is also looking to engineer microbes to produce what he calls “second-generation” biofuels such as butanol, isopentanol and hexadecane. Though similar in structure to ethanol, these fuels behave much more like gasoline. They contain more energy per volume; a car driving on a gallon of ethanol will go only 67 percent as far as a car on a gallon of gasoline; on butanol, it can go 80 percent as far. And unlike ethanol, these fuels can be used directly in jet and diesel engines.

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