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UGA researchers looking to turn fruit into fuel

By April Sorrow
University of Georgia

Half of all the fruit grown in Georgia is never eaten by people or animals. It rots in the fields. A University of Georgia researcher says that spoiled fruit could fuel cars.

That wasted fruit can be converted into bioethanol through a fermentation process, said Elliot Altman, program coordinator for the UGA Center for Molecular Bioengineering.

“All fruits are 10 percent sugar, or potentially 5 percent ethanol,” said Altman, an engineer with the UGA College of Agricultural and Environmental Sciences. “It’s a real opportunity.”

The fermentation process could create a high-protein byproduct, which can be used in animal feed, called dried distillers grain. The largest opportunity in Georgia lies in watermelons and peaches. Last year, the state harvested one billion pounds of watermelon and more than 61 million pounds of peaches. The same amount rotted in the fields.

The fruit is left behind because it doesn’t make the grade for commercial sale. Consumers don’t want fruit that doesn’t look perfect, even though it is fine to eat in most cases. Some of the discarded fruit is used in preserves and juice, but 50 percent never leaves the field.

Ethanol conversion is not possible on a small scale like biodiesel operations. Getting enough commodity groups excited about converting the waste to fuel is one battle Altman hopes legislation may help with.

“One farmer isn’t big enough to set up operation,” he said. “If packers knew in advance the fruit would be used for something, they could gather it in a separate place for transport to the ethanol plant.”

Government regulations mandate the blending of 5 percent ethanol into gasoline by 2009 and 10 percent by 2011. The Renewable Fuel Standard program will increase the volume of renewable fuel required to be blended into gasoline from 9 billion gallons in 2008 to 36 billion gallons by 2022.

But, ethanol plants aren’t cheap.

“You can’t build a small plant,” he said. “To be cost effective, most experts agree that a plant would need to produce at least 10 million gallons of ethanol a year.”

Altman and his colleague Mark Eiteman, a biological and agricultural engineering professor, are working on techniques to simplify the commercial ethanol plant, making it cheaper to produce ethanol and DDG.

For example, their group has researched adding expired table sugars to increase the ethanol yields that can be obtained. Access to waste fruit is not a year-round venture, he said.

“Even with a couple of fruits, a fruit-ethanol plant would only be operational for half a year, and the infrastructure for an ethanol plant is a significant investment,” Altman said.

Altman is currently researching several other products – like grain sorghum – that could be used when the fruit is not available.

“It has silo storage capability and is able to grow in areas of Georgia not suitable for anything else,” he said. “It does not take away from other crops and would not hurt the food market.”

Georgia also has potential to produce ethanol from bakery waste. “We have a unique niche in the Atlanta area with our bakeries.”

(April Sorrow is a news editor with the University of Georgia College of Agricultural and Environmental Sciences.)

(April R. Sorrow is a science writer with the University of Georgia Public Affairs Office.)

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