By April Reese
University of
Georgia
Poultry rendering plants recycle the chicken parts you don’t
usually see into useful oils and other products. But they also
produce an odor. And they give off compounds that are regulated
in some Georgia counties.
K.C. Das, J.R. Kastner and a team of other researchers with the
University of Georgia Bioconversion Center have taken on the
plants’ air-related problems. They set out to solve them with
two projects:
- Developing a natural biofilter to cleanse the air of the
volatile organic compounds being produced. - Finding ways to produce fewer VOCs by modifying the cooking
process.
Odors and ozone
The VOCs produced in the rendering process can lead to odors and
the formation of ground-level ozone, which may cause respiratory
damage in some people. The U.S. Environmental Protection Agency
regulates these VOCs through the Clean Air Act.
The researchers evaluated the gases being produced to find a way
to treat the air. This process took about 18 months. Then they
could begin working on solutions.
“Since July 2001, we’ve been working on evaluating treatment
options,” said Das, an agricultural engineer with the UGA
College of Agricultural and Environmental Sciences.
Peat moss, compost, bark…
Das and Kastner recommended using a biofilter to treat the
emissions pumped into the air. A biofilter is a bed of organic
material such as peat moss, compost, bark, wood chips, rice
hulls or a combination of these. It’s used to biologically remove
pollutants from the air stream.
One Georgia rendering plant uses a biofilter to treat its air
emissions. But many others spend massive amounts of money using
chlorine dioxide to bleach the air and neutralize the polluting
chemical compounds.
“Once we know these compounds and their concentrations, then the
designed biofilter can be used in any plant that renders poultry
waste,” Das said.
Ways to reduce VOCs
At the same time that the scientists started working on the
treatment options, he said, they also began researching ways to
reduce VOCs in the rendering process.
To understand VOCs, think of gasoline. A highly volatile
compound, gasoline evaporates quickly. That’s why you can smell
it at the pump. Fueling your car at noon differs greatly from
filling it up a night, because hotter air causes the gasoline to
evaporate faster.
The same principle, Das said, can apply to the rendering
industry when it comes to cooking temperatures and the gases
being released.
Higher heat, higher VOC levels
Das believes the high temperatures rendering plants used to
process the meat by-products has much to do with the volume of
odorous VOCs produced. So he has begun evaluating alternative
cooking methods at lower temperatures.
He’s trying to find methods that would be environmentally safe
while not compromising on the safety or quality of the products
and always keeping cost-efficiency in mind.
Miniature cooking tanks were created for the experiments. These
allow researchers to recreate the environment found inside the
plants.
Neither angle of the research has been completed. But Das hopes
to see results within the next year.
“We hope to reach major milestones relating to treatment options
by July 2003,” he said. “I suspect that the pollution prevention
work will continue longer, probably until July 2004.”
The solutions can’t come too soon in north Georgia. Metro
Atlanta has been classified an ozone nonattainment zone. That
means the air quality there is not up to Clean Air Act standards.
Cleaning up rendering-plant emissions would be a small, but
helpful piece of the clean-air puzzle.
