Ethanol Production: A Net Energy Winner


There is clearly no doubt that fuel ethanol contains more energy than it takes to produce.

In June 2004, the U.S. Department of Agriculture updated its 2002 analysis of the issue and determined that the net energy balance of ethanol production is 1.67 to 1. (For every 100 BTUs of energy used to make ethanol, 167 BTUs of ethanol is produced.) In 2002, USDA had concluded that the ratio was 1.35 to 1.

The USDA findings have been confirmed by additional studies conducted by the University of Nebraska and Argonne National Laboratory. In fact, since 1995, nine independent studies found ethanol has a positive net energy balance, while only one study – which used outdated data – found the energy balance to be negative.

A Michigan State University study (2002) found that ethanol produced from corn provided 56 percent more energy than is consumed during production (1.56 to 1). This study looked at producing ethanol from both dry and wet milling of corn—and included corn grain production, soybean products from soybean milling and urea production.

These studies take into account the entire life cycle of ethanol production—from the energy used to produce and transport corn to the energy used to produce ethanol to the energy used in the distribution of ethanol in gasoline.

What’s behind this continual increase in net energy balance?

Production efficiency is one factor. Compared to just five years ago, today’s ethanol plants produce 15 percent more ethanol from a bushel of corn—and using 20 percent less energy in the process.

The energy efficiency of American farmers is another reason. According to USDA statistics, U.S. agriculture uses about half the energy to produce a unit of output today than was needed to produce the same output in 1950.

Better corn varieties, improved production practices and conservation measures also figure into the equation. A 1 percent increase in corn yield raises the net energy value by 0.37 percent.

It’s also important to note that energy from ethanol is not the only result of ethanol production. Coproducts such as distillers grains, gluten feed, carbon dioxide, and corn sweeteners are also created in ethanol production. That means that not all the energy used by an ethanol plant is directed at manufacturing ethanol, thus further improving the net energy balance of ethanol production.

Ethanol opponents frequently cite a study by Cornell University’s Dr. David Pimentel, who concluded that it takes 70 percent more energy to produce ethanol than it yields. Pimentel’s findings have been consistently refuted by USDA and other scientists who say his methodology uses obsolete data and is fundamentally unsound.