Ethanol production is more energy efficient than previously thought as processing plants continue to make upgrades and changes to improve the process.
A recent report by John Christianson, certified public accountant for the independent United States accounting firm Christianson & Associates PLLP, catalogues the energy improvements being made at ethanol biorefineries across the country.
According to the report, the average amount of energy, measured in British thermal units (Btus), required to produce ethanol and a livestock feed co-product across all ethanol production technologies was reduced 13.5pc between 2004 and 2007.
The most efficient biorefineries demonstrated an even more dramatic reduction in energy requirements of 19pc and today use fewer than 21,000 Btus/gal of ethanol produced (see table).
A large portion of the energy consumed in an ethanol plant is for the production of distillers grains, with production of dried distillers grains consuming much more than wet production.
A noticeable industry trend reflects reducing the Btus consumed per gallon as improved production practices and technology occur.
The efficiency gains are larger for the leaders, which represent the newer, more efficient plants.
Another trend is that developing ethanol plants are emphasizing energy efficiencies of production.
Likewise, ethanol biorefineries have also cut electricity usage.
The Christianson report shows a 13pc reduction in electricity consumption at the average ethanol facility.
Ethanol yield efficiency is measured by the gallons of ethanol that can be produced from a bushel of corn.
In 2004, the industry had an average yield of 2.80 denatured gallons, with the leaders at 2.87 gal/bu.
This denatured yield was consistent over a four-year time period due to a varying denaturant rate usage.
However, there was an increase in un-denatured yield - from 2.66 gal of ethanol per bushel in 2004 to 2.70 gal/bu in 2007.
The leaders also increased from 2.73 in 2004 to 2.77 gal/bu. in 2007.
This increase in un-denatured yield can be attributed to improved plant technologies as well as more experienced management teams at the plants, the report noted.
Findings of the Christianson report are consistent with results released in March from the US Department of Energy's Argonne National Laboratory analysis that showed improving efficiency of the US ethanol industry between 2001 and 2006.
The Argonne study found that US ethanol facilities are using less energy and water than five years ago but producing more ethanol.
Water consumption is down 26.6pc, grid electricity use is down almost 16pc and total energy use is about 22pc lower.
Energy balance
Soon-to-be released research conducted under the supervision of Dr Kenneth Cassman at the University of Nebraska-Lincoln's Nebraska Center for Energy Sciences Research confirms a continuation of better efficiencies in ethanol plants.
"Recent research conducted at the University of Nebraska clearly shows that estimates for the energy balance of corn-based ethanol are much more favorable - in fact, two to three times more favorable than previous estimates," Cassman said.
"That's because most of the published values for energy efficiency of corn ethanol are 'backward looking' in the sense that they evaluated older technologies with regard to energy use in corn production, the biorefinery and co-product utilization."
Cassman, who is also a Heuermann professor of agronomy at the university, said it is important to understand that ethanol has a substantial net positive direct energy balance: 1.5-1.6 more units of energy are derived from ethanol than are used to produce it.
"Using dated information simply doesn't work in a world where the technology and efficiency of corn and ethanol production are rapidly improving over the years," he said.
"Moreover, if the goal is to reduce dependence on imported oil, we estimate that 13 gal. of ethanol are produced for every gallon of petroleum used in the production lifecycle for corn ethanol."