Energy can be saved, more water recycled and livestock feed improved when microscopic fungus is grown in some of the leftovers from ethanol production. Researchers at Iowa State University have found that fungi can be used to clean up and improve the dry-grind ethanol production process.
June 4, 2008 By Iowa State University News Service
May 27, 2008
AMES, Iowa — Growing microscopic fungus in
some of the leftovers from ethanol production can save energy, recycle more
water and improve the livestock feed that's a co-product of fuel production,
according to a team of researchers from Iowa State University and the University of Hawai'i.
"The process could
change ethanol production in dry-grind plants so much that energy costs can be
reduced by as much as one-third," said Hans van Leeuwen, an Iowa State professor of civil, construction
and environmental engineering and the leader of the research project.
Van Leeuwen and the other
researchers developing the technology — Anthony L. Pometto III, a professor of
food science and human nutrition; Mary Rasmussen, a graduate student in
environmental engineering and biorenewable resources and technology; and Samir
Khanal, a former Iowa State research assistant professor who's now an assistant
professor of molecular biosciences and bioengineering at the University of
Hawai'i at Manoa — recently won the 2008 Grand Prize for University
Research from the American
Academy of Environmental Engineers for the project.
"Those chosen for
prizes by an independent panel of distinguished experts address the broad range
of modern challenges inherent in providing life-nurturing services for humans
and protection of the environment," according to a statement from the
academy. "… Their innovations and performance illustrate the essential
role of environmental engineers in providing a healthy planet."
The Iowa State project is focused on using fungi
to clean up and improve the dry-grind ethanol production process. That process
grinds corn kernels and adds water and enzymes. The enzymes break the starches
into sugars. The sugars are fermented with yeasts to produce ethanol.
The fuel is recovered by
distillation, but there are about six gallons of leftovers for every gallon of
fuel that's produced. Those leftovers, known as stillage, contain solids and
other organic material. Most of the solids are removed by centrifugation and
dried into distillers dried grains that are sold as livestock feed, primarily
The remaining liquid, known
as thin stillage, still contains some solids, a variety of organic compounds
from corn and fermentation as well as enzymes. Because the compounds and solids
can interfere with ethanol production, only about 50 percent of thin stillage
can be recycled back into ethanol production. The rest is evaporated and
blended with distillers dried grains to produce distillers dried grains with
The researchers added a
fungus, Rhizopus microsporus, to the thin stillage and found it would feed and
grow. The fungus removes about 80 percent of the organic material and all of
the solids in the thin stillage, allowing the water and enzymes in the thin
stillage to be recycled back into production.
The fungus can also be
harvested. It's a food-grade organism that's rich in protein, certain essential
amino acids and other nutrients. It can be dried and sold as a livestock feed
supplement. Or it can be blended with distillers dried grains to boost its
value as a livestock feed and make it more suitable for feeding hogs and
Van Leeuwen said all of
that can save United States ethanol producers a lot of energy and
money at current production levels:
- Eliminating the need to evaporate thin stillage
would save ethanol plants up to $800 million a year in energy costs.
- Allowing more water recycling would reduce the
industry's water consumption by as much as 10 billion gallons per year.
And it allows producers to recycle enzymes in the thin stillage, saving
about $60 million per year.
- Adding value and nutrients to the livestock feed
produced by ethanol plants would grow the market for that feed by about
$400 million per year.
- And the researchers' fungal process would
improve the energy balance of ethanol production by reducing energy inputs
so there is more of an energy gain.
Van Leeuwen estimated it
would cost $11 million to start using the process in an ethanol plant that
produces 100 million gallons of fuel per year. But, he said the cost savings at
such a plant could pay off that investment in about six months.
The Iowa State research project is supported by
grants of $78,806 from the Grow Iowa Values Fund, a state economic development
program, and $80,000 from the U.S. Department of Agriculture through the Iowa
Biotechnology Byproducts Consortium.
The researchers have filed
for a patent on the technology and are looking for investors to commercialize
the invention. And while the process needs to be proven at larger scales, there
are high hopes it can do a lot to improve the efficiency of ethanol production.
"We will be saving
ethanol producers money and energy," Pometto said. "That's the bottom