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September/October 2002s
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University of Illinois Engineers Lead the Field in Efficient Ethanol Research

Scientist: Steven Eckhoff, Dept. of Ag Engineering, 217-244-4022, sre@age.uiuc.edu Source: Leanne Lucas, College of Aces/ITCS Urbana, 217-244-9085, llucas@uiuc.edu

In the competitive world of fuel production, every penny per gallon counts. That’s why industry is taking notice of two innovative milling techniques under study at the University of Illinois Agricultural engineers. Vijay Singh and Steven Eckhoff are studying “quick germ” and “quick fiber,” two techniques that could have significant economic impact on the production of ethanol. “There are two ways to produce ethanol,” Singh explained. “One is wet milling, the other is dry grind. Our goal is to make dry grind look like wet milling, but do it at a much lower capital cost.”

The wet milling process soaks the corn in sulfur dioxide for 24 to 36 hours so the kernel can be separated into its four component parts--germ, protein, fiber and starch. The starch is fermented into ethanol, and the three remaining parts are sold as high value co-products.

Dry grind, on the other hand, starts with raw corn, finely milled and cooked. The starch is fermented and converted into ethanol, and the three non-fermentables are carried through the process and recovered at the back end as a feed product. This feed product is called distiller-dried grains with solubles (DDGS), and is the only co-product produced by the dry grind process. It can be used in feed for cattle, but because of its high fiber content, it cannot readily be used for swine or poultry.

Right now, the cost of capital per gallon of ethanol produced by the dry grind process is approximately 24 cents less than the cost of the wet milling process. However, wet milling still has the overall economic edge on dry grind for two reasons: its high-value co-products and its large scale. According to Eckhoff, wet milling co-products have a 15-cent per gallon advantage over dry grind co-products. What’s more, the average wet mill operates at 200,000 bushels a day, while the average dry grind plant operates at 50,000 bushels a day. “So it’s very difficult for the dry grind plant to compete,” Eckhoff said. The quick germ and quick fiber processes could help the small dry grind ethanol producers reduce the 15-cent per gallon difference in the value of co-products, compared to the wet millers.

Essentially, the quick germ and quick fiber processes add wet milling technology to the front end of the dry grind process. What’s more, quick germ makes it possible to recover the germ as a co-product and quick fiber recovers the fiber--significantly boosting the economic benefits of dry grind. With the quick germ method, corn is soaked for a short period in water only. Because the oil-laden germ is the first part of the kernel to fully hydrate, it floats and is recovered by density separation. To recover the germ properly, the soaking solution must have the proper density. It was while trying to determine the right density for germ recovery that Singh discovered he could increase the density and also recover the coarse fiber.

Removing the germ and fiber from the corn has three benefits, said Singh. “In the conventional dry grind process, DDGS is the only co-product produced. By pulling the germ and fiber out up-front, you have added high-value co-products.” A second benefit is increased protein content in the DDGS. “When you pull the germ and fiber out, your concentration of protein goes up and you can sell your DDGS for higher protein content,” said Singh. Increasing the total capacity of the dry grind plant is the third benefit. By removing germ and fiber from the corn, a producer can pack more fermentable substrate in the fermenter and therefore produce more ethanol per batch. Eckhoff believes the co-products obtained from the quick germ and quick fiber processes will substantially improve the profitability of dry grind ethanol production. In fact, he said, “With the work that Vijay and others have been doing, pulling the co-products out up-front, it really tips the scales in favor of dry grind ethanol.”

Singh’s quick germ process will be tested on a commercial scale beginning in early 2003. This project was one of 10 chosen for further development at the National Corn-to-Ethanol Research Pilot Plant. This pilot plant, funded in part by the USDA and the state of Illinois, will be used by government, university and industrial laboratories to test promising technologies on a smaller scale. Experts believe that if only five of the ten initial projects can be sped to commercialization, ethanol production costs can be reduced by 10 cents a gallon.

Currently, production of ethanol in the United States is at 1.77 billion gallons per year. That number is expected to triple by the year 2012, greatly enhancing the economic benefits derived from the efficient production of ethanol.