Ames, Iowa
May 27, 2008
Growing a 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 for cattle.
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 solubles.
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 chickens.
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 line." |
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