Skip to main content
Skip Navigation

Does Ethanol Pollute the Environment … or Does Corn?

By: Dennis Keeney

When environmentalists complain about ethanol, they complain about the negative impacts of an ethanol economy: increased levels of nitrate, sediment and pesticide pollution, as well as decreased biodiversity and fewer small farms. Are these valid complaints? Or are they actually complaining about corn? Are we talking about “failed agronomy?”

First, some facts. The amount of land dedicated to corn today is at an all-time high. And so is the land in soybeans. The reason is clear: corn and soybeans are at all-time high prices and returns. The USDA is putting less emphasis on conservation reserve programs, and so farmers with their eyes on the bottom line are putting more land into corn and soybeans.

But why is corn fetching such high prices? Higher prices have been brought on by more demand—for feed grain, for food, for export and yes, for ethanol. Food demand, brought on by higher standards of living and more people, is worldwide and has brought higher prices for all grains.

So how does corn culture cause environmental harm? First, corn is a poor scavenger of nutrients. Because of its relatively shallow rooting zone and growth pattern, much of the year the soil is open and subject to leaching. In much of the Midwest, where most of the corn is grown, the land is tiled to facilitate drainage in the spring and fall. This causes water to move quickly through the soil, carrying nitrate with it. Because the drainage tiles are directly connected to the surface drainage systems, water with nitrate rapidly flows into the rivers draining the Corn Belt, and then on to the Mississippi River, where it ultimately affects (negatively) the Gulf of Mexico.

The result is hypoxia; the excess nutrients (such as nitrates) promote algae growth, which reduces oxygen, effectively asphyxiating marine life. Growth and survival of fish and shell fish is imperiled, and the affected area in the northern Gulf of Mexico has become known as the “Dead Zone.” But the Corn Growers lobby insists that agriculture is not to blame for increased nitrate loads.

Through the Environmental Quality Incentives Program (EQIP), which is funded through the Farm Bill, the USDA has created targets for decreasing hypoxia in the Dead Zone. But as corn growers put more land into corn to meet ethanol mandates, the goal of reducing nitrate pollution in the Gulf of Mexico is in serious jeopardy.

Mark David, a University of Illinois researcher, related nitrate concentration to tile drainage in the Midwest Corn Belt and found that tile drainage explained 83 percent of the nitrate loss in the Gulf dead zone.

David expressed it well. He said, “Farmers are not to blame…. They are using the same amount of nitrogen as they were 30 years ago and getting much higher corn yields, but we have created a very leaky agricultural system. This allows nitrate to move quickly from fields into ditches and on to the Gulf of Mexico. We need policies that reward farmers to help correct the problem….  A lot of people just want to blame fertilizer, but it’s not that simple…. It’s fertilizer on intensive corn and soybean agricultural rotations in heavily tile-drained areas.”

It is widely documented that annual row crops increase soil erosion. And while there are ways to grow crops that minimize soil loss, the approaches cost money and time. Research directed by Dr. Richard Cruse of Iowa State University provides evidence that erosion in some parts of the state is occurring at levels far beyond government estimates. It is being exacerbated, they say, by severe storms, which have occurred more often in recent years, possibly because of broader climate shifts. In a variety of locations, we’re losing topsoil considerably faster—10 to as much as 50 times faster—than it’s forming.

Pesticide use on corn is currently in decline because of the advent of genetically modified corn hybrids. Extensive monitoring of Corn Belt watersheds has shown that pesticide residues in water are also declining.

So the answer to our question, “Does ethanol cause environmental pollution?” is a double-edged one. Corn, not ethanol, is to blame. Yet, without ethanol, we would have less corn.

More Stories and Viewpoints

Mighty Millets Have Potential for Positive Change

An overlooked grain, the mighty millet, has potential to mitigate climate change, improve nutrition, and make positive change in industrial food animal production.

Bob Lawrence: The Long View on Food System Reform

Director emeritus Bob Lawrence reflects on CLF’s progress on creating positive change in industrial food animal production models.

Paolo di Croce: Biodiversity is Essential

Slow Food’s Paolo di Croce is on a mission to help people choose food that’s culturally meaningful and suited to local ecosystems.