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Resources:Energy Balance: Ethanol is a Net Energy Winner

There is now a strong consensus among scientists: the energy output from burning ethanol as a fuel source exceeds the energy input required for ethanol production. Studies that suggest that corn ethanol has a negative net energy balance rely on outdated data, and fail to consider coproduct generation and other factors that improve ethanol’s energy efficiency. Furthermore, the energy balance of corn ethanol is steadily increasing as corn farmers and ethanol producers embrace new technologies.

Essential Facts:

  1. Scientific evidence shows that ethanol has a positive net energy balance, while petroleum is a clear energy loser.
  2. Coproduct utilization, plant location, and business strategy all make a difference in determining an ethanol plant’s net energy balance.
  3. New innovations and technologies are constantly improving the energy balance for ethanol production.
  4. Ultimately, ethanol is a key strategy to reduce our contribution to climate change and our reliance on foreign oil.

1) Scientific evidence shows that ethanol has a positive net energy balance, while petroleum is a clear energy loser.

In June 2004, the U.S. Department of Agriculture updated its 2002 analysis of ethanol production and determined that the net energy balance of ethanol production is 1.67 to 1.1 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. These figures take into account the energy required to plant, grow and harvest the corn—as well as the energy required to manufacture and distribute the ethanol.

Ethanol opponents frequently cite studies by Cornell University’s Dr. David Pimentel and Tad W. Padzek, who concluded that ethanol returns only about 70% of the energy used in its production (a net energy balance of -29%). Pimentel’s findings have been consistently refuted by USDA and other scientists who say his methodology uses obsolete data and is fundamentally unsound. In a detailed analysis of Pimentel’s research, Dr. Michael S. Graboski of Colorado School of Mines says Pimentel’s findings are based on out-of-date statistics (22 year-old data) and are contradicted by USDA.2 Pimentel’s reports have also been debunked by Michael Wang and Dan Santini of the Center for Transportation Research, Argonne National Laboratory, who conducted a series of detailed analyses on energy and emission impacts of corn ethanol from 1997 through 1999.3 A recent study by UC scientists, published in the January, 2006 edition of Science magazine, also acknowledges a positive net energy balance for ethanol, placing the energy return at between 4 and 9 MJ/L.4

Furthermore, even the most pessimistic assessments of ethanol’s energy balance acknowledge that ethanol is an improvement over petroleum-based fuels. Using the same analytical methods employed by some ethanol critics, Michigan State University’s Bruce Dale calculates the net energy of petroleum to be -45%, compared to the -29% that Pimentel and Patzek find for ethanol. In the worst-case scenario, burning ethanol is still more energy-efficient than burning gasoline.5

“Unfortunately, his (Pimentel’s) assessment lacked timeliness in that it relied on data appropriate to conditions in the 1970’s and early 1980s, but clearly not the 1990s…With up-to-date information on corn farming and ethanol production and treating ethanol co-products fairly, we have concluded that corn-based ethanol now has a positive energy balance of about 20,000 BTU per gallon.”
- Michael Wang and Dan Santini

Two of the studies stand out from the others because they report negative net energy values and imply relatively high GHG emissions and petroleum inputs…these two studies also stand apart from the others by incorrectly assuming that ethanol coproducts…should not be credited with any of the input energy and by including some input data that are old and unrepresentative of current processes, or so poorly documented that their quality cannot be evaluated
- Farrell, et al, “Ethanol Can Contribute to Energy and Environmental Goals,” in Science 311 (January 2006).

Corn ethanol is energy efficient…Moreover, producing ethanol from domestic corn stocks achieves a net gain in a more desirable form of energy. Ethanol production utilizes abundant domestic energy supplies of coal and natural gas to convert corn into a premium liquid fuel that can replace petroleum imports by a factor of 7 to 1.
- Shapouri, Duffield, and Graboski, “Estimating the Net Energy Balance of Corn Ethanol,” 1995

Pimentel’s findings are at odds with the overwhelming majority of researchers:

Scientific evidence shows that ethanol has a positive net energy balance

2) Coproduct utilization, plant location, and business strategy all make a difference in determining an ethanol plant’s net energy balance.

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. This means that not all of the energy used by an ethanol plant is directed at manufacturing ethanol, and the energy output from ethanol combustion is not the only positive factor to be considered in determining the net energy balance of the ethanol production process. Because distillers grains can be burned as an energy source, there may even be opportunities for the plant to be self-powered or to export energy, resulting in an energy return of over 100%.

Ethanol producers can enhance the energy payoff from coproduct utilization by making smart business decisions. For example, some ethanol production facilities are strategically located adjacent to cattle feeders and dairies. These sites enable local marketing of distillers’ grains, thus avoiding energy intensive drying processes and reducing fuel use for transportation. As a result, these processes use significantly less energy than the industry standard, and can reduce greenhouse gas emissions by up to 40 percent compared to conventional gasoline.

The distillers grains complex represents valuable coproducts of ethanol production from corn grain. Distillers grains can provide from 35 to 40% of the total diet for feedlot cattle…With increased ethanol production, more coproducts may be generated than cattle feedlots and dairies can use. If this situation occurs, coproducts can be burned as energy sources for ethanol plant operation or exported to foreign markets.
- Cassman, et al, “Convergence of Agriculture and Energy: Implications for Research and Policy,” College of Agricultural Science and Technology, November 2006.

…the energy requirements for drying coproducts for transport as DDGS represents roughly one-third the total energy used in a typical ethanol plant. Thus, a trend toward using WDGS [wet distillers’ grains] as cattle feed is emerging because of the lower energy requirements…Transportation costs are a critical factor in considering plant location. In addition to optimizing plant location, a move toward “closed loop” ethanol plants is feasible. In this scenario, cattle are fed larger volumes of the coproducts, and cattle waste products and excess coproducts are used as fuel sources to replace a portion of the natural gas used to power the biorefinery.
- Cassman, et al, “Convergence of Agriculture and Energy: Implications for Research and Policy,” College of Agricultural Science and Technology, November 2006.

3) New innovations and technologies are constantly improving the energy balance for ethanol production.

The net energy balance of ethanol production continues to improve as ethanol production becomes more efficient. One bushel of corn now yields 2.8 gallons of ethanol—up from 2.5 gallons just a few years ago. Today’s ethanol plants produce 15 percent more ethanol from a bushel of corn—and use 20 percent less energy in the process – than those of five years ago.

The energy efficiency of American farmers is also contributing to improvements in the energy efficiency of ethanol production. According to USDA statistics, U.S. agriculture uses about half the energy to produce a unit of output today than in 1950. Better corn varieties, improved production practices and conservation measures also figure into the equation. A one percent increase in corn yield raises the net energy value of ethanol by 0.37 percent.6

The future for ethanol is even brighter. Ethanol derived from cellulosic sources will offer even greater energy savings and greenhouse gas reductions. Not only are the energy inputs to grow cellulosic biomass relatively minimal, but cellulosic feedstocks will generate energy to power ethanol plants as a coproduct of production, and may even reduce energy consumption as compared to gasoline by more than 100 percent by generating excess energy to export to the power grid.7

4) Ultimately, ethanol is a key strategy to reduce our contribution to climate change and our reliance on foreign oil.

When it comes to the benefits of ethanol production, energy balance alone doesn’t tell the entire story. Energy used to produce ethanol represents an investment in displacing nonrenewable fuels with renewable alternatives – whereas energy used to produce gasoline, for example, goes toward perpetuating the problems associated with petroleum-based fuel sources. Comparisons between ethanol and gasoline, or between any two fuel sources, are meaningless unless the important implications of petroleum substitution are considered.

For every barrel of crude oil that enters the refining process, about 0.85 barrel of liquid fuel reaches the market as gasoline. By contrast, investing a barrel’s worth of petroleum to generate energy for ethanol production yields about 20 barrels of energy-equivalent liquid fuel. Thus, by switching from gasoline to ethanol, we can extend our supplies of petroleum and reduce our reliance on foreign oil.8 Additionally, an April, 2007 report from the Environmental Protection Agency found that life-cycle greenhouse gas emissions from corn ethanol are 21.8 percent lower than those from gasoline.9 In order to make responsible use of our energy resources, we need to calculate our return on investment not only in terms of energy in versus energy out, but also in terms of improvements in our long-term energy and climate security. Using those metrics, ethanol is a clear winner.

Footnotes

1 http://www.ethanolrfa.org/objects/documents/files/net_energy_balance_2004.pdf

2 http://www.ncga.com/ethanol/pdfs/EthanolfFuelsRebuttal.pdf

3 http://www.ethanolrfa.org/objects/documents/80/31961.pdf

4 Alexander E. Farrel, et al, “Ethanol Can Contribute to Environmental and Policy Goals,” Science 311, January 2006.

5 Bruce E. Dale, “Thinking Clearly About Biofuels: Ending the Silly Net Energy Controversy,” 05 February 2007.

6 http://www.eesi.org/programs/Agriculture/Energy%20Balance%20update.htm

7 http://www.oregon.gov/ENERGY/RENEW/Biomass/docs/FORUM/EthanolEnergyBalance.pdf

8 http://www.ncga.com/ethanol/pdfs/020607ThinkingClearlyAboutBiofuels.pdf

9 http://www.epa.gov/otaq/renewablefuels/420f07035.htm