Bacteria for biofuel

by Diane Boudreau

Some scientists are trying to develop more efficient solar cells to capture sunlight for human energy use. Other scientists are trying to produce fuel using artificial photosynthesis. Wim Vermaas doesn't believe in reinventing the wheel. Cyanobacteria invented a perfect way to extract energy from the sun more than 2 billion years ago. He's content to let them continue doing the work.

Vermaas is a professor of life sciences working with ASU's Center for the Study of Early Events in Photosynthesis. He has been studying cyanobacteria for the past 20 years. Currently, he's working to engineer cyanobacteria to produce biofuels.

"Photosynthesis has more on its mind than making biomass for us humans," explains Thomas Moore, director of the Photosynthesis Center. "Photosynthesis is a living process. It involves all the complexities of life."

The cyanobacterium was the first photosynthetic organism to be genetically sequenced. That work opened all kinds of new opportunities for the scientists who study it. Vermaas is working to engineer cyanobacteria to be more efficient at manufacturing fuels that people can use.

"You can engineer organisms that have more membranes, for example, which are largely lipids," he says "Lipids are good for biodiesel. We can modify organisms in a way that makes them more productive. You don't rely on Mother Nature's design. They weren't naturally selected for high lipid production," he adds.

Biodiesel is a good option because it would require few changes to our energy infrastructure.

"You can put biodiesel right into any existing diesel engine," says Vermaas. "You can transport it using the existing infrastructure."

Biodiesel releases as much carbon dioxide (CO₂) as regular diesel, but it also gobbles up CO₂ as it is produced. The result? It doesn't contribute to rising atmospheric CO₂ levels which contribute to global warming.

"The carbon in biodiesel is fixed photosynthetically from CO₂. You can view it as a cycle," says Vermaas.

Lots of scientists are looking at biodiesel and other forms of biofuel as a way to produce cheap, renewable energy. For example, in the Midwest and in South America, corn is used to produce ethanol. But corn might not be the best crop to use for making fuel. After all, if you put the corn in your gas tank, then you can't put it on your dinner plate.

"You can't use corn twice," says Vermaas. "If everyone wants to do bioethanol, then what are we displacing? Are we reducing the food supply? What are we doing to the soils? In the Midwest, that could be farmland being used to make fuel. In South America, the cornfields were rainforests. It's not very sustainable. Biofuel isn't necessarily green."

The beauty of bacteria is that they can be grown on land that isn't suitable for anything else. Replacing a 6 gigawatt coal-fired power plant with biomass cultures would require about 240 square miles of land. That is about half the area covered by the city of Phoenix, Arizona.

"You can use much degraded lands, as long as they're sunny and reasonably warm. The water used to grow the bacteria can be reused. You can even take groundwater from agricultural runoff. It contains nitrate which will fertilize the cultures," says Vermaas.