Switchgrass a better biofuel source than corn
Rhett A. Butler, mongabay.com
January 7, 2008

Switchgrass yields more than 540 percent more energy than the energy needed to produce and convert it to ethanol, making the grassy weed a far superior source for biofuels than corn ethanol, reports a study published in Proceedings of the National Academy of Sciences (PNAS).

Collecting data from 10 farm sites in Nebraska, North and South Dakota in which farmers grew switchgrass in fields ranging from 7 to 23 acres over a five year period, Marty Schmer, a researcher with the Agricultural Research Service of the U.S. Department of Agriculture, and colleagues found that, on average, switchgrass produced biomass equivalent to 320 gallons of ethanol per acre — more than 60 percent more the average yield for an equivalent area of corn after factoring in fossil fuel use for fertilizers and pesticides. The study also found that average greenhouse gas emissions from cellulosic ethanol derived from switchgrass were 94% lower than those from gasoline.

Ethanol yield for various crops

Net energy yield for various crops
"This clearly demonstrates that switchgrass is not only energy efficient, but can be used in a renewable biofuel economy to reduce reliance of fossil fuels, reduce greenhouse gas emissions and enhance rural economies," said co-author Ken Vogel, a U.S. Department of Agriculture-Agricultural Research Service geneticist.

While corn and other annual cereal grains are now primary sources for U.S. ethanol production, the researchers note that perennial crops, like switchgrass, as well as agricultural waste and forestry biomass can be broken down into sugars that can be fermented into ethanol. In the future these could be developed as important feedstocks for cellulosic ethanol that could potentially displace 30 percent of current U.S. petroleum consumption.

"Dedicated perennial energy crops such as switchgrass, crop residues, and forestry biomass are major cellulosic ethanol sources that could potentially displace 30% of our current petroleum consumption," wrote the authors, adding that "improved genetics and agronomics may further enhance energy sustainability and biofuel yield of switchgrass."

"As an indicator of the improvement potential, switchgrass biomass yields in recent yield trials in Nebraska, South Dakota, and North Dakota were 50% greater than achieved in this study."

The authors say the high yield and environmental benefits of switchgrass make it an attractive feedstock for biofuel production relative to annual crops in the United States.

Domestically-produced biofuels have seen a surge in popularity in recent years due to increasing concern over climate change and energy security.

CITATION: Jan Fuglestvedt et al. (2007). Climate forcing from the transport sectors. Proceedings of the National Academy of Sciences January 7-11, 2008.

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Rhett A. Butler, mongabay.com (January 07, 2008).

Switchgrass a better biofuel source than corn.