Erosion, pollution: The secret environmental cost of the United States' ethanol policy
The most important of those assumptions was called the yield, a measure of how much corn could be produced on an acre of land. The higher the yield, the easier it would be for farmers to meet the growing demand without plowing new farmland, which counted against ethanol in the greenhouse gas equation.
Corn yields have inched steadily upward over the years as farms have become more efficient. The government's first ethanol model assumed that trend would continue, rising from 150 bushels per acre to about 180 by the year 2022.
Agriculture companies like Monsanto Co. and DuPont Pioneer, which stood to make millions off an ethanol boom, told the government those numbers were too low.
They predicted that genetically modified seeds — which they produce — would send yields skyrocketing. With higher yields, farmers could produce more corn on less land, reducing the environmental effects.
Documents show the White House budget office also suggested the EPA raise its yield assumptions.
When the final rule came out, the EPA and Agriculture officials added a new "high yield case scenario" that assumed 230 bushels per acre.
The flaw in those assumptions, independent scientists knew, was that a big increase in corn prices would encourage people to farm in less hospitable areas like Wayne County, which could never produce such large yields.
But the EPA's model assumed only a tiny increase in corn prices.
"You adjust a few numbers to get it where you want it, and then you call it good," said Adam Liska, assistant professor of biological systems engineering at the University of Nebraska. He supports ethanol, even with its environmental trade-offs.
When the Obama administration finalized its first major green-energy policy, corn ethanol barely crossed the key threshold. The final score: 21 percent.
"If you corrected any of a number of things, it would be on the other side of 20 percent," said Richard Plevin of the Transportation Sustainability Research Center at the University of California, Berkeley. "Is it a coincidence this is what happened? It certainly makes me wonder."
It didn't take long for reality to prove the Obama administration's predictions wrong.
The regulations took effect in July 2010. The following month, corn prices already had surpassed the EPA's long-term estimate of $3.22 a bushel. That September, corn passed $4, on its way to about $7, where it has been most of this year.
Yields, meanwhile, have held fairly steady.
But the ethanol boom was underway.
It's impossible to precisely calculate how much ethanol is responsible for the spike in corn prices and how much those prices led to the land changes in the Midwest.
Supporters of corn ethanol say extreme weather — dry one year, very wet the next — hurt farmers and raised prices.
But diminishing supply wasn't the only factor. More corn than ever was being distilled into ethanol.
Historically, the overwhelmingly majority of corn in the United States has been turned into livestock feed. But in 2010, for the first time, fuel was the No. 1 use for corn in America. That was true in 2011 and 2012. Newly released Department of Agriculture data show that, this year, 43 percent of corn went to fuel and 45 percent went to livestock feed.
The more corn that goes to ethanol, the more that needs to be planted to meet other demands.
Scientists predicted that a major ethanol push would raise prices and, in turn, encourage farmers like Leroy Perkins to plow into conservation land. But the government insisted otherwise.
In 2008, the journal Science published a study with a dire conclusion: Plowing over conservation land releases so much greenhouse gas that it takes 48 years before new plants can break even and start reducing carbon dioxide.
For an ethanol policy to work, the study said, farmers could not plow into conservation land.
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