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.
