by Marion Nestle
Jul 18 2010

USDA: Ethanol from corn yields “substantial” energy

I’m just getting around to reading an optimistic report from USDA about how much more energy we are getting from converting corn to ethanol. 

The report surveyed corn growers for the year 2005 and ethanol plants in 2008 and happily reports that energy yields are improving.  

Never mind that the mere thought of using food resources to feed cars rather than farm animals or people makes no sense from the standpoint of sustainability.   Early estimates of energy efficiency made it clear that it took almost as much—or, in fact, as much—energy to convert corn to ethanol as cold be obtained from the ethanol, and that the size of the energy yield depended on who was doing the estimating.   

This latest report says that “the net energy balance of corn ethanol has increased from 1.76 BTUs to 2.3 BTUs of required energy” since 2004.  If true,

Ethanol has made the transition from an energy sink, to a moderate net energy gain in the 1990s, to a substantial net energy gain in the present. And there are still prospects for improvement. Ethanol yields have increased by about 10 percent in the last 20 years, so proportionately less corn is required. In addition to refinements in ethanol technology, corn yields have increased by 39 percent over the last 20 years, requiring less land to produce ethanol.

I still think this is not a good idea.  A rational energy policy must develop sustainable sources, and corn is not one of them.

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  • JMT

    I’m new here. Why isn’t corn considered sustainable?

  • Sorghum Crow

    It’s not sustainable because of the energy input required. It’s all about EROEI (Energy return on energy invested). Presently, it’s not clear that we get more energy than we put in. David Pimental from Cornell has addressed this issue. Google his name for interesting articles. Growing corn takes an immense input of energy and materials. I recommend you go to and start reading…

  • Sorghum Crow

    Sorry, that should be

  • Bellinghamster

    Please do not feed the corn to the farm animals. It’s very very bad for them. ;(

  • DennisP

    An important problem is that with ethanol, the price of food becomes linked to the price of oil. If oil prices go up, then more land is devoted to corn for ethanol and less land goes into producing food crops, so the price of food goes up. This is apart from the effect of higher oil prices increasing the cost of purchased inputs for the fossil fuel-drenched production systems of modern agri-industrialism.

  • B. Korn

    Why can’t ethanol be produced from vegetable scraps instead of growing corn, with all it’s necessary imputs?

  • marketmaster

    The billions of gallons of water needed for producing ethanol is seldom mentioned in discussions of the negative consequences of increasing ethanol production. We live in the Midwest where the ancient water of the Ogalalla Aquifer is rapidly declining. When there is no more ground water, I wonder where our grains for eating will come from.

  • Bobby

    Hi JMT, to answer your question:

    let’s see, more corn=more crop subsidies, less bio diversity, more water sucked out of the water table for irrigation, more monoculture agriculture, greater and herbicide pesticide use, higher prices for basic foodstuffs, more marginal cropland converted back into production, greater erosion, more oil-based production inputs, more oilo based fertiliser required, more energy required to convert corn into ethanol, more risk that old cars get their fuel systems completely messed up when increased % of ethanol is required to be put into gasoline, more agricultural lobbyists lining the streets of washington, and of course, more agricultural lobbying dollars lining the pockets of your elected officials.

    Well, that’s a start to the problems that corn-based ethanol production can create.

    Corn is far from a sustainable crop as practiced in the present north american agricultural system.

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