Net Energy Yield

The Governors' Ethanol Coalition believes that ethanol plays a strongly positive role in America today by reducing our dependence on oil imported from unstable regions of the world, reducing consumer energy costs, improving environmental quality, and facilitating economic development. The significant rise in oil prices that began in 2003 has become a significant threat to our national economy as oil is now fully one-quarter of the national trade deficit and is the single most important cause of inflationary pressures.

However, these benefits to the American public from ethanol are all dependent on the simple fact that a typical gallon of ethanol produced in America today contains more energy than the fossil fuel inputs required to produce it. Said differently, all of the benefits are dependent on the fact that ethanol has a positive “net energy yield.” This positive net energy yield is made possible by renewable energy — the energy of the sun that is captured by corn or other plants and converted into ethanol in an ethanol facility. The solar energy that is captured by the plant and then converted to ethanol is greater than the amount of fossil fuel inputs required to achieve that conversion. In attempts to discredit ethanol, however, ethanol opponents frequently make unsubstantiated attacks on the net energy yield of ethanol.

The broad body of available science, including numerous peer-reviewed scientific studies, supports the strong positive net energy yield of ethanol production. Those studies, as well as the work of the only significant scholar who finds a negative energy yield for ethanol production, are provided below.

The Governors’ Ethanol Coalition firmly agrees with mainstream science that ethanol production has a positive energy yield. The Governors have been concerned by the continuing inaccurate statements that ethanol production has a negative net energy yield, and believe that the negative energy yield argument cannot withstand close scrutiny. Therefore, the Coalition makes both sides of this argument available for open and public consideration.

The Coalition finds much recent work, such as the U.S. Department of Agriculture study by Hosein Shapouri (indicating that corn ethanol has an energy output/input ratio of 1.67) supports a positive energy yield conclusion. The Coalition furthermore finds that the main work arguing that ethanol has a negative net energy yield, produced by Cornell University’s David Pimentel, relies heavily on flawed and out-of-date data (from the 1970’s through early 1990s) and does not take into account energy costs associated with other co-products such as dried distillers grains (DDGs). At a basic level, critics of corn ethanol seem unaware that the production of ethanol from corn starch leaves essentially all the proteins and various other elements available for livestock feed and other purposes, and they are content to base their criticism on data that is so old that it is entirely unrelated to current farm practices.

The Governors’ Ethanol Coalition is therefore pleased to make available the complete arguments on both sides. For a useful discussion of the net energy yield debate, see:

For a survey of key academic studies on ethanol’s net energy yield, see the following:

If you want more information about the Coalition, contact the Coalition's Administrative Office at Box 95085, Lincoln, NE 68509

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