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Scientists at Illinois State University in Normal
have developed a method for processing massive quantities of hog excrement
that removes so much of the nasty odor and pollution potential, it even has
a cute name — Swine Waste Economical and Environmental Treatment
Alternatives, or SWEETA.
The process is designed for use on large-scale
factory farms, where hogs spend their lives in confined feeding areas built
on slatted floors suspended above containment pits. The SWEETA process
provides a way to separate the “slurry” from those pits into
solid and liquid waste, turning the former into compost and the latter into
fertilizer that farmers can spray on crops.
There’s nothing new about the separation
process — it mimics what municipal wastewater-treatment plants have
been doing for decades. The breakthrough at ISU is the development of a
separation system that costs as little as $100,000 — cheap enough
that large-scale farmers can afford it.
“All the technology is available commercially
from other companies. We have taken other companies’ technology and
developed them into a systems approach,” says Paul Walker, professor
of animal science and coordinator of ISU’s livestock and urban waste
research team.
SWEETA separates solid waste through a combination of
mechanical screens and a polymer flocculent, which attracts and binds
smaller particles of organic matter. Walker likens this part of the process
to the way Ivory soap attracts particles of dirt. “If you look at
dirty suds in the bathtub, that’s what a flocculent is,” he
says.
The solids can then be composted, mixed with
landscape waste, and turned into mulch that can be sold on the retail
market or used as an agronomic fertilizer, Walker says. The remaining
liquid is aerated and can be used on farmland where corn or soybeans are
grown, at much higher concentrations than the untreated slurry that many
farmers now use. The SWEETA process removes more than 90 percent of
phosphorus — the surface-water pollutant associated with the creation
of algae blooms.
At ISU’s 40-acre test site, researchers used
25,000 gallons of SWEETA-treated liquid effluent per acre instead of the
5,000 to 8,000 gallons of slurry that’s the traditional per-acre
dose. “We were still phosphorus-deficit for what the corn plant
needed,” Walker says. “We have eliminated the pollution
potential for phosphorus with this method.”
At this stage, however, phosphorus and noxious odors
are the only hazards reduced by the SWEETA process. It isn’t designed
to address such contaminants as pesticides, parasites, and hormones.
Furthermore, this new system isn’t yet in use
anywhere other than ISU’s test farm. Walker has hosted workshops for
extension specialists and is planning a “field day” for
producers, but so far no one has bought it.
“We’re still trying to make the process
more economical,” Walker says. “We’ve got several folks
interested — just no one has chosen to do it yet.”
Contact Dusty Rhodes at drhodes@illinoistimes.com.
This article appears in Jul 17-23, 2008.
