Water: Still Ethanol's Achilles Heel

As our nation scuttles to find cleaner energy sources, we must look at each energy option on the table from every possible perspective, examining all potential externalities or unintended consequences – especially consequences related to our water. With the spotlight on ethanol as a ‘cleaner’ substitute for oil and gasoline, we must ask the question, “Have we adequately examined the externalities associated with running our cars and trucks on ethanol?”

Biofuels can be made from a variety of feedstocks including corn, perennial grasses, soy beans, algae and woodchips, just to name a few. All of these feedstocks have their pros and cons in terms of cost, resource requirements (think water and energy inputs), land use and level of technological maturity. This makes it impossible (and unwise) to lump all biofuels together in a single category because the production process and environmental impacts for each type of biofuel can be drastically different.

While it is important to keep in mind that not all Biofuels are created equal, the most widely used feedstock for ethanol production is corn As a result corn farming is the largest source of water pollution attributable to biofuels by way of chemical fertilizer seepage and runoff. In an article titled ‘As Ethanol Booms, Critics Warn of Environmental Effects,’ New York Times journalist Erica Gies reports:

Corn requires vastly more fertilizer and pesticides than soybeans or other potential biofuel feedstocks, such as perennial grasses, according to a 2007 report from the National Academy of Science.

…Fertilizer and pesticide runoffs from the U.S. Corn Belt are key contributors to “dead zones” in the Gulf of Mexico and along the Atlantic Coast.

In 2007, an analysis was done on to look at the effects of growing corn for ethanol on the Embarras River in Illinois. Researchers evaluated the increased amount of phosphorus and nitrogen run-off as a response to increasing corn production per acre of farm land along the river. As reported in the article, ‘More Ethanol Means More Corn – and More Water Pollution,’ researchers found that:

…When acreage in the Embarras' watershed is planted half in corn and half in soybeans, the usual crop rotation, about 31 pounds of nitrogen from fertilizer runs off every acre of land in the upper stretches of the river.

What happens if two-thirds of the acreage is planted in corn? Using a computer model called SWAT (Soil and Water Assessment Tool), University of Illinois researchers projected that the nitrogen runoff would increase to more than 40 pounds per acre each year _ an increase of more than 29 percent.

This just goes to show that the more we rely on ethanol as an energy source, the more we risk water pollution and water scarcity. But this isn’t the end of the story; ethanol production doesn’t just consume and pollute water through corn farming, the actual treatment and production process requires a great deal of water as well. As NYT’s Gies reports further:

Modern plants use about three gallons of water to produce one gallon of ethanol. The National Academy of Sciences report estimated that a plant producing 100 million gallons a year uses as much water as a town of 5,000 people.

…According to a G.A.O. report last year, 12 Midwestern states produced 89 percent of the U.S. corn crop in 2007 and 95 percent of the ethanol, using 7 to 321 gallons of water for corn irrigation for every gallon of ethanol produced.

The 2007 report by the National Academy of Sciences calculated that it required 780 gallons of irrigation water to produce a gallon of ethanol in Nebraska, the second-largest U.S. ethanol producer, behind Iowa.

These numbers show quite a large range in water intensity, using approximately 7 to 780 gallons of water to produce one gallon of ethanol – again, illustrating how not all Biofuels are created equal - however these figures may not even capture the entire picture as far as water use for crop irrigation. As famed water wonk, and professor of law and public policy at the University of Arizona Robert Glennon reports:

The most efficient ethanol plants need 4 gallons of water to produce one gallon of ethanol fuel. That doesn't account for the feedstock, and in the case of corn, it takes 2,500 gallons of water to grow enough corn to produce 1 gallon of ethanol. That's right, 2,500 gallons.

So is it 7, 780 or 2,500 gallons of water per gallon of ethanol? Whatever the accurate water withdrawal and consumption rates may be, it is obvious that ethanol production not only requires a massive amount of water, but is a huge contributor to water pollution as well, both reducing and impairing our currently suffering available water supplies. To reiterate a conclusion presented by my colleague Mr. Griffiths-Sattenspiel in a previous post on the same issue:

With much of the country already facing debilitating water shortages, the last thing we need is a fuel source that will put more strain on our water supplies and increase pressure to divert our rivers.