U of I
investigators evaluate ways for ethanol plants to recycle more water
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[April 20, 2007]
URBANA -- Ethanol plants use about three
gallons of water for every gallon of ethanol they make, using the
dry grind process. But investigators at the University of Illinois
are trying to determine if the amount of water that is recycled
during ethanol production can be increased -- significantly.
"If you have a plant that's going to produce 100 million gallons
of ethanol, like the proposed Anderson plant, that's about 400
million gallons of water per year, and that's not a trivial
amount," said Kent Rausch, a U of I agricultural and biological
engineer involved in the project. "If we can increase the amount
of recycled water from 50 to 85 percent, that will make a big
difference from economic and environmental standpoints."
the conventional dry grind process, raw corn is finely ground
and cooked; then the starch is fermented and converted into
ethanol. After the ethanol has been recovered, the remaining
material is called whole stillage. It contains water, protein,
fat, fiber and ash from the corn kernel and yeast. This stillage
is run through a centrifuge, and about 50 percent of the water
is recycled. The soluble material that remains after
centrifuging is called thin stillage.
Rausch and his colleagues are planning to add membrane
filtration -- filtration through very small holes -- to the
process at this point. "We're looking at filtering the thin
stillage to improve our ability to recycle it," said Rausch.
"Impurities that inhibit yeast growth build up in the water and
reduce ethanol yield; that makes the process less efficient."
Although a total recycle may not be possible, he said, "Our goal
is to get rid of those impurities so more water can be
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Rausch and his colleagues are also experimenting with a modified
dry grind process that removes much of the protein, fiber and fat
before the fermentation process.
"As a result, the thin stillage obtained from the modified dry
grind process will be different," said Rausch. "This will affect the
filtration rate through the membrane, so we will test which membrane
construction and pore size will work most effectively with each
Vijay Singh, an agricultural and biological engineer at the U of
I, and Ron Belyea, an animal scientist at the University of
Missouri, are co-investigators for this study, which is being funded
by the Council on Food and Agricultural Research.
"Water use is important to the economic well-being of the plant
even where water is plentiful," Rausch concluded. "Reducing the
demand for water in the process should reduce the environmental
footprint. We want these facilities to do all they can to be good
stewards in the community."
[Text from file received from
the University of Illinois
College of Agricultural, Consumer and Environmental Sciences]