The Energetics of Ethanol: An Introduction and Link to Studies

[last update February 2008]

Does it take more energy to make ethanol than is contained in ethanol?  That question continues to haunt the ethanol industry even after nearly 30 years of expanding production.  Over the years more than 20 scientific studies have examined the question.  This document contains links to the major studies of the subject completed during the last decade or so.

Some introductory comments may be in order.

First, any analysis should be viewed as an historical snapshot.  Virtually all studies of ethanol before 1990 showed a net energy loss.  Virtually all of the studies after 1990 show a net energy gain.  This is because the ethanol industry, in terms of energy use per gallon of ethanol produced, has become much more efficient over the years, as has the farmer, in terms of energy use per bushel of corn grown.    

Second, agricultural productivity and energy intensity varies dramatically not only by crop but by state and even within a state.  For example, irrigated corn acreage, which comprise a small percentage of overall corn acreage, is energy intensive.  A rotational corn cultivation in which corn fields become soybean fields become alfalfa fields on a three year basis, are low energy users per bushel grown.  

The Institute for Local Self-Reliance’s own study may be a good starting point because it is very accessible, explains the assumptions used and why, and offers three different scenarios(national average, best current, best near term future).  Although completed in 1992 and updated in 1995 ago we’re pleased to say that our conclusions are very much within the range of more recent estimates.  Click here for ILSR's 1995 study, How Much Energy Does It Take to Make A Gallon of Ethanol?

The United States Department of Agriculture has done the best job of showing comparative data of all the major studies on the energetics of ethanol.  This is an excellent place to understand why there are differences.  The initial USDA report was done in 1995.  Click here for the 1995 USDA study.   An update was published in 2002.  Click here for the 2002 USDA study.

David Pimentel, a Cornell University professor, has been ethanol’s most consistent critic. He has done several studies over the last few years.  His latest was published in 2003. Click here for Pimentel's study. For a more recent critical analysis, see University of California Berkeley professor Tad Patzek's study,  Thermodynamics of the Corn-Ethanol Biofuel Cycle (2004).

There have been several critiques of Pimentel’s methodology and numbers.  Here is a brief one - Click here for the study and critique of Pimentel's work .  Another much more extensive, indeed exhaustive, analysis is available here. Click here for study.  To my knowledge, Pimentel has not responded to his critics nor done a detailed critique of studies that come to different conclusions.

Pimentel and Patzek teamed together and released a study in March 2005 titled, "Ethanol Production Using Corn, Switchgrass, and Wood; Biodiesel Production Using Soybean and Sunflower," published in the Natural Resources Research journal. Indeed, this latest study reached a remarkable and highly provocative conclusion: the energetics of making ethanol from switchgrass or wood are considerably worse than for making ethanol from corn, and the energetics of making biodiesel from soybeans or sunflowers may be more bleak than making ethanol from corn.

In response to these latest numbers from Patzek/Pimental, ILSR prepared the following reponse and critique. The Carbohydrate Economy, Biofuels and the Net Energy Debate - issued August 2005. ILSR presented these findings at an August 23, 2005, presentation at the National Press Club [watch the video].

Argonne National Laboratory also weighed in on the latest claims by Patzek/Pimentel and issued a report titled, The Debate on Energy and Greenhouse Gas Emissions Impacts of Fuel Ethanol (August 2005).

Researchers at the University of California - Berkeley released a study published in the January 27, 2006, issue of the journal Science that shows a positive energy balance for ethanol production. [Click to download their full paper, the six analyses, and supporting research from the UC-Berkeley web site].

More:

• Cellulosic Biofuels: Another Opportunity for Washington to Marry Agriculture and Energy Goals - by David Morris, published in Ethanol Today Magazine, May 2008
• Ethanol and Land Use Changes
  This February 2008 policy brief criticizes the authors of two recent studies published in Science for advancing a conclusion not supported by their own studies. The paper notes that the vast majority of today’s ethanol production comes from corn cultivated on land that has been in corn production for generations. Since little new land has come into production, either directly or indirectly, the current use of ethanol clearly reduces greenhouse gas emissions.(View Press Release)
• Give Ethanol a Chance: The Case for Corn-Based Fuel - by David Morris, published on AlterNet, June 13, 2007
• Energizing Rural America: Local Ownership of Renewable Energy Production is the Key
  This January 2007 paper by David Morris was originally published by the Center for American Progress.  This report argues that Congress must recognize the dramatic benefits of clean, renewable energy on rural communities and then ensure that the federal farm bill policies work to maximize local ownership of the rapidly expanding biofuels and wind energy industries. Numerous policy options are recommended.
• Ethanol as a Renewable Fuel: An Overview - video of a speech by David Morris, ILSR Vice President, presented at the Minnesota Pollution Control Agency's Air Quality Series, September 28, 2006 (streaming video, 1.5 hours)
• Putting the Pieces Together: Commercializing Cellulosic Ethanol - September 2006
  A report examining federal policies supporting cellulosic ethanol production and advocating that the Federal government adopt strategies that support farmer-owned biorefineries. [see also ILSR Press Release]
• The New Ethanol Future Demands a New Public Policy - by David Morris, June 21, 2006 [this is an expanded version of an opionion column published in the NY Times - also in PDF]
• The Once and Future Carbohydrate Economy - by David Morris, published in the American Prospect magazine, March 2006
• Ownership Matters: Three Steps to Ensure a Biofuels Industry That Truly Benefits Rural America
  This February 2006 paper by David Morris was adapted from a speech given at the Minnesota Ag Expo 2006. The paper provides a snapshot of today's biofuels industry and a roadmap to ensure that local farmers see significant benefits from the expanding industry in the future.