Switchgrass fuel yields bountiful energy: study

NEW YORK (Reuters) - Switchgrass, a crop touted by venture capitalists and environmentalists alike as a next-generation ethanol feedstock, yields about five times more energy than it takes to grow it, making the plant a far more efficient fuel source than corn, a new study said.

In addition, the life cycle of the switchgrass ethanol -- which includes growing the crop, making the fuel, and burning it in vehicles -- emits about 94 percent less of planet-warming carbon dioxide than the life cycle of gasoline, said the study, published on Tuesday in the Proceedings of the National Academy of Sciences.

U.S. companies are racing to make economical ethanol from nonfood sources like switchgrass as oil clings near record highs of over $100 per barrel and as the U.S. government inches closer to national greenhouse gas emission regulations.

Switchgrass is expected to be the main feedstock for cellulosic ethanol, a new type of alternative fuel made from breaking down the woody bits of plants. The energy law signed by President George W. Bush last month mandates a five-fold increase in ethanol blending by 2022, and some of that fuel is required to come from cellulosic sources.

Switchgrass, which used to grow naturally across wide swaths of the United States, can be grown on marginal crop land using far fewer energy-intensive inputs like fertilizer than corn needs. And since it does not double as a feed crop, it will not lead to higher grain prices.

“Switchgrass is a good crop for marginal crop lands,” Ken Vogel, a co-author of the study, called “Net Energy of Cellulosic Ethanol from Switchgrass,” said in an interview. “Corn is still going to be grown to make ethanol; whether it ever takes a chunk of crop land away from corn is all going to come down to economics,” said Vogel, a researcher for the U.S. Department of Agriculture.

Cellulosic ethanol currently costs about double the price as making the fuel from corn, the main U.S. ethanol feedstock. Venture capitalists and companies that are making small amounts of cellulosic ethanol say once the industry gets underway, biological advances in the fungi and other organisms used to break down woody plant bits into fuel will make the process cheaper.

Switchgrass plants sequester carbon dioxide in the ground because they have extensive root systems that remain buried after the crop is harvested, Vogel said. Steep greenhouse gas emissions reductions, of about 94 percent compared to gasoline, are contingent on burning switchgrass waste to fire bio-refineries. Unlike waste left over from corn after it is made into ethanol, switchgrass waste cannot be made into the animal feed distillers’ grain.

The study, funded by the U.S. energy and agriculture departments, did not compare the efficiency of corn ethanol to switchgrass ethanol. Several recent studies have suggested corn ethanol yields about 1.25 to 1.50 times more energy than it takes to grow and process the grain into fuel.

Editing by Christian Wiessner