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New Reports Find Increasing Ethanol Production Efficiency
by Kristin Brekke

The energy efficiency of the ethanol production process and the net energy balance of ethanol itself are both increasingly positive, according to two recent studies.

A detailed report on dry mill ethanol production was published in May by Dr. Steffen Mueller, a Principal Research Economist for the Energy Resources Center at the University of Illinois at Chicago. The data covers the 2008 production year, an update to the figures on ethanol production efficiency found in a 2001 survey commissioned by the U.S. Department of Agriculture. Dry mill facilities account for 86 percent of the U.S. industry.

In just seven years’ time, gains have been made across a number of key categories.

Compared to 2001, today’s ethanol production requires 28 percent less thermal energy and 32.1 percent less electricity per gallon – a significant reduction in energy inputs. In addition, 5.3 percent more ethanol can be created today from the same bushel of corn.

Ethanol production, 2008 vs. 2001

  • 28% less thermal energy used per gallon
  • 32.1% less electricity used per gallon
  • 5.3% higher ethanol yield per bushel

Source: “Detailed Report: 2008 National Dry Mill Corn Ethanol Survey,” Dr. Steffen Mueller, May 2010

“This study is an excellent illustration of how ethanol production in the U.S. advances each and every year,” said Brian Jennings, Executive Vice President of the American Coalition for Ethanol. “U.S. ethanol producers are creating more ethanol using far fewer energy inputs today than they did just a few years ago, and it’s only going to continue getting more productive and efficient.”

The report found that America’s ethanol producers are further diversifying their co-products, in the model of a true “biorefinery.” Traditionally, corn-based ethanol plants produced two co-products: dried distillers grain with solubles (DDGS) and wet distillers grain (WDG). But the new report found that a sizeable number of today’s ethanol plants also produce a third co-product – corn oil.

“One of the most significant new process technologies adopted by ethanol plants is backend corn oil separation, which accounts for about one-third of all surveyed plants,” the study states.

A dozen of the plants surveyed also reported co-products other than distillers grain and corn oil, a trend the report author believes indicates further diversification within the industry.

The report also finds a trend among U.S. ethanol producers toward optimizing water use. Many reported the recycling of water, improved water treatment capacity, and reverse osmosis as improvements to water usage at their plants. Three ethanol plants responding to the survey reported achieving the status of a zero-discharge facility, meaning all water is recycled or reused in the process and no water is discharged from the plant.

Compared to 2006 industry data in an Argonne National Laboratory report (“Analysis of the Efficiency of the U.S. Ethanol Industry 2007”), ethanol producers in 2008 had reduced water use by 22 percent per gallon of ethanol in just two years’ time. And that 2006 study represented a 26.6 percent decrease in water use from the 2001 USDA figures – a clear and steady improvement in the amount of water used by the industry.

Net energy balance improves

A second report out this year, published June 21 by the U.S. Department of Agriculture’s Office of Energy Policy and New Uses, finds that the net energy gain from converting corn to ethanol is improving in efficiency.

The new report updates data from 2004 to measure all conventional fossil fuel energy used in the production of 1 gallon of corn ethanol. The findings – for every 1 British Thermal Unit (BTU) of energy required to make ethanol, 2.3 BTUs of energy are produced.

“A dry grind ethanol plant that produces and sells dry distiller’s grains and uses conventional fossil fuel power for thermal energy and electricity produces nearly two times more energy in the form of ethanol delivered to customers than it uses for corn, processing, and transportation,” the USDA report states.

This report of a 1 to 2.3 positive energy balance for ethanol is significantly higher than USDA’s previous estimate of 1 to 1.77, which was based on 2004 data.

The gains are related to new efficiencies in both the growing of the corn and the energy in the corn that is actually used for the ethanol production process. New agricultural efficiencies are paying off.

USDA found that in U.S. corn production, both direct energy inputs and the use of nitrogen as fertilizer are on the decline, leading to fewer BTUs of energy required to produce a bushel of corn. Since the mid-1990s, nitrogen use on a per-bushel basis has declined by about 20 percent, and all direct energy components have declined by about 50 percent.

“Together, the nitrogen and direct energy reductions result in a 30 percent decline in the energy required to produce a bushel of corn. Overall, 65,285 BTU/bu (British thermal unit per bushel) were required for corn production in 1996, whereas 41,029 BTU/bu were required in 2005,” the study found.

Also, USDA states, “it is the energy in corn that is actually used for ethanol production, expressed per gallon of ethanol, which is important for an evaluation of ethanol production.”

Yields at ethanol plants have improved by about 10 percent over the last 20 years, meaning proportionately less corn is required. Only the starch portion of the corn – about two-thirds of the kernel – is used for ethanol production. These factors have combined to reduce the corn-energy input into ethanol production from 16,346 BTUs per gallon to 9,811 BTUs per gallon over the last 10 years.

New technologies in ethanol production are leading to an even better overall energy balance. Ethanol plants that are offsetting some conventional energy with biomass power sources – corn stover, for example – are achieving a 1 to 2.8 positive energy ratio, according to the new USDA report.

The numbers speak for themselves – today’s ethanol production is energy efficient and carries a clearly positive energy balance. The trend should continue through advancements in both agriculture and ethanol production, but would benefit by action from the federal government to make sure that there is enough open market for the Renewable Fuels Standards biofuels targets to be met.

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The American Coalition for Ethanol publishes Ethanol Today magazine each month to cover the biofuels industryís hot topics, including cellulosic ethanol, E85, corn ethanol, food versus fuel, ethanolís carbon footprint, E10, E15, and mid-range ethanol blends.
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