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The ethanol equation
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How much energy does it take to convert this corn into another energy source -- ethanol? That is one of the questions being asked as the Legislature considers whether to increase the ethanol content in gasoline. (MPR file photo)
As the Minnesota Legislature debates whether to expand the use of ethanol in the state, old arguments against the fuel are resurfacing. One of the most contentious is this: it takes more energy to make the fuel than it produces. The analysis comes from Cornell University scientist David Pimentel. What may be less well known is that Pimentel says his negative energy equation is true for practically all forms of fuel.

Worthington, Minn. — Pimentel has studied ethanol for more than 20 years. He says even with more efficient production techniques, ethanol is still an energy loser.

"It takes about 1.3 gallons of oil to produce one gallon of ethanol," says Pimentel.

He uses a very detailed formula to come to that conclusion. Ethanol is basically pure alcohol, fermented from corn. Pimentel includes in his analysis the energy used to grow corn, as well as the energy used to ferment the grain.

The equation includes obvious things like tractor fuel and the energy needed to make fertilizer. But Pimentel takes it one step further, by including the energy it takes to build the tractor.

"Now this is all prorated on how many acres the machinery is used on, how long the machinery lasts and so forth," Pimentel says.

He then goes even further, including human energy -- the calories burned by the people doing the farm work. At the ethanol processing plant, he is just as rigorous. He calculates the energy needed to heat water to ferment the grain, but also the energy needed to build the plant and all its parts -- steel girders, concrete, stainless steel.

Pimentel's analysis is so detailed it yields some big surprises when it's applied to other energy sources. Take gasoline. Pimentel says if all the energy used to make the fuel is considered, gasoline, too, is a net energy loser.

"If you include the pumping and processing and so forth, it runs a little over 10 percent," says Pimentel.

In other words, it takes 10 percent more energy to make gasoline than it produces. Pimentel's gasoline equation puts him at odds with some of his supporters. Oil industry officials have quoted Pimentel's findings on ethanol to support their case against the fuel.

On the opposite side of the ethanol debate from Pimentel are researchers like Bruce Dale at Michigan State University. Dale claims ethanol yields more energy than it takes to make it. Dale disagrees with Pimentel's methodology, saying Pimentel violates recognized standards guiding academic research.

"Those standards say specifically you're not to include the energy cost of making the machinery. Neither are you to include the energy cost for feeding the people that work the machinery. It's just not part of the study," says Dale. "Where do you stop? Do you include the energy cost of feeding the people that made the machinery, that made the machinery, that made the machinery?"

Dale says the debate over how much energy it takes to make ethanol has obscured its main benefit. He says it makes corn into a more useful fuel, much like transforming coal into electricity.

"Coal sitting in the ground won't light a room, and it won't power up a computer," Dale says. "When we burn it to make electricity, we sacrifice quantity of energy to make a higher quality of energy."

Ethanol opponents question whether the fuel is a higher quality energy source. They say it adds to air pollution.

One thing researchers David Pimentel and Bruce Dale agree on is that politics finds its way into ethanol research. Each of them believes the other skews research to fit their position on ethanol. It's a debate that will continue.

The Minnesota Legislature is considering a bill to expand the use of ethanol in the state. It wants to require a 20-percent ethanol blend in gasoline by the year 2012. In Congress, farm state lawmakers are pushing for more ethanol use all across the nation.

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