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University of Nebraska-Lincoln research finds positive energy balance for corn-based ethanol
Lincoln, Nebraska
March 22, 2004

By Vicki Miller
IANR News Service
This story is from the spring/summer issue of Research Nebraska magazine, which is published twice annually by the University of Nebraska's Agricultural Research Division in the Institute of Agriculture and Natural Resources.


Dan Walters thinks ethanol gets a bad wrap energywise and he's got numbers to prove it.

Grain-based ethanol is a cleaner-burning, renewable alternative to fossil fuels. But critics cite studies showing ethanol production uses more energy than it produces.

"The problem is that's all old data," said Walters, a University of Nebraska-Lincoln soil scientist. Such studies are based on figures from the late 1980s and early 1990s, yet much has changed in agriculture and ethanol production in the past decade.

"If you're making public policy, we need modern data that reflects the energy efficiencies of current or future farming and ethanol processing," he said. To calculate a modern energy balance for ethanol, Walters gathered and assessed current information on all the fossil fuel needed to grow and transport corn and to convert it to ethanol, blend it with gasoline and get it to the pump.

Today's ethanol has a positive energy balance, he found. It provides more energy than is used to produce it. Walters calculated the energy output to energy input ratio for converting irrigated corn to ethanol is 1.3-to-1 and 1.4-to-1 for dryland corn.

"We're about 30 percent ahead" energywise, the Institute of Agriculture and Natural Resources scientist said.
Advances in ethanol conversion and plant efficiency are part of the equation, he said. In 2002, a bushel of corn produced 2.7 gallons of ethanol, up from 2.5 gallons in 1990. Ethanol byproducts such as livestock feeds enhance efficiency because energy would be needed to produce these products if they weren't made during ethanol conversion.

On the crop production side, nitrogen is the largest energy factor, accounting for 30 percent to 50 percent of all energy needed to raise corn, Walters said. Nitrogen efficiency has improved immensely over the past 20 years, and continues improving by an average .013 bushels of grain per pound of nitrogen annually.

Improvements in seed genetics, water use, crop management and production equipment also help boost efficiency.

"These efficiencies rely on normal best management practices and judicious nitrogen use to optimize, not maximize, productivity," he said. Much of Walters' production data comes from 160-acre fields in the university's ongoing carbon sequestration research, but he said national averages are similar.

"I'm confident we're still in positive energy balance," he said.

Irrigation requires extra energy but compensates by boosting yields and nitrogen efficiency, Walters said.
"That bodes very well for Nebraska," he said, where irrigation is widely used and 23 percent of the corn crop is sold for ethanol. "We can compete with rainfed corn growing states for ethanol production."

Walters calculated the ethanol energy balance while working on broader energy use and carbon assessments for the carbon sequestration project. More than half of corn's carbon is in grain, but scientists don't factor it in long-term carbon storage because grain's carbon recycles back to the atmosphere as feed or food in a year or so.
But converting grain to ethanol helps offset carbon emissions from fossil fuels, Walters said.

Typically, 10 percent ethanol is blended with conventional unleaded gasoline to produce E-10 Unleaded.
"When we put gasoline in our car, we're using carbon that has been stored for millions of years," Walters explained. "When we put E-10 in the tank, carbon dioxide emissions are 10 percent less than someone who burns straight fossil fuel because ethanol is a biofuel. It's made with carbon from the atmosphere that's recycled through the corn plant."

He predicts ethanol's energy equation will continue improving along with farming and processing efficiencies.
"That picture gets better and better."

A U.S. Department of Energy grant helps fund NU's carbon sequestration research.
Research Nebraska magazine

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