Public Release: 

Wet-milling process potentially could expand ethanol, feed industries

University of Illinois at Urbana-Champaign

An experimental filtering system being tested in the corn wet-milling process is showing promise. The desired payoff, in the form of added value to corn gluten meal, could be more incentive to produce ethanol and an expanded animal-feed industry. In turn, a University of Illinois researcher says, farmers could see a higher demand for corn.

Instead of using a traditional centrifuge system, UI researchers have substituted membrane filtration, using porous materials to strain fluids that pass through. If the project works according to plan, said Kent Rausch, a professor of agricultural engineering, the filtration switch could become the first major change in the wet-milling procedure for corn in more than 40 years. Rausch described the system and preliminary results of laboratory and commercial testing during the 51st Annual Starch Convention, an international conference, April 11-14 in Detmold, Germany.

Wet milling separates corn into its four main parts: starch, germ, fiber and protein. It is used to produce a variety of primary products such as sweeteners, ethanol and starch. Gluten meal and gluten feed, both of which are used widely as animal feed to supply vitamins, minerals and energy, are coproducts that result from the primary processing.

The goal, Rausch said, is to allow more soluble protein to be retained by the filters and be available for use in gluten meal that is fed to swine and poultry, which require high levels of protein. It is valued at about 12 to 15 cents per pound and contains about 60 percent protein ­ most of it insoluble and, therefore, difficult to digest. Gluten feed is valued at 2 to 3 cents per pound, has about 21 percent protein, and is mixed with other protein sources and fed to cattle.

If these coproducts are more valuable, Rausch said, ethanol production could become more viable. "For corn-to-ethanol processing to be sustainable and profitable, we have to get these coproducts to be worth more. The overall costs of the corn and the processing are very important. If the other products are worth more, then ethanol would be more profitable." The filters, which have been tested for about a year, appear to enhance the nutritional value of the gluten meal and gluten feed, Rausch said. Gluten meal possibly can be improved even more by mixing in the solids from the leftover steepwater, which contains soluble protein, he said.

The new technology also will benefit the wet-milling industry. With the membrane filters recovering more protein, less protein would get stuck on the steepwater evaporators, meaning the costly task of cleaning them would be reduced, he said.

Assuming that enhanced nutritional quality of the coproducts is realized, the cost of converting to the membrane filters could be recovered within a year, based on current projections, Rausch said.


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