Getting the Stink Out!

Submitted by: Matt Shipman, NC State News Services

A North Carolina State University researcher has devised a new technology that really does not stink. In fact, it could be the key to
eliminating foul odors and air pollutants emitted by industrial chicken rendering facilities and – ultimately – large-scale swine feedlots.

Dr. Praveen Kolar, assistant professor of biological and agricultural engineering at NC State, has developed an inexpensive treatment process that significantly mitigates odors from poultry rendering operations. Rendering facilities take animal byproducts (e.g., skin, bones, feathers) and process them into useful products such as fertilizer. However, the rendering process produces extremely foul odors.

These emissions are not currently regulated by the government, but the smell can be extremely disruptive to a facility’s community. The
industry currently uses chemical “scrubbers” to remove odor-causing agents, but this technique is not very effective, Kolar says.
Furthermore, some of the odor-causing compounds are aldehydes, which can combine with other atmospheric compounds to form ozone – triggering asthma attacks and causing other adverse respiratory health effects.

Kolar, working with his co-author Dr. James Kastner at the University of Georgia, has designed an effective filtration system that takes
advantage of catalytic oxidation to remove these odor-causing pollutants. Specifically, the researchers use ozone and
specially-designed catalysts to break down the odor-causing compounds. This process takes place at room temperature, so there are no energy costs, and results in only two byproducts: carbon dioxide and pure water.

The researchers developed the catalysts by coating structures made of activated carbon with a nanoscale film made of cobalt or nickel oxides, Kolar says. “We used activated carbon because its porous structure gives it an extremely large surface area,” Kolar explains, “meaning that there is more area that can be exposed to the odorous agents.” The cobalt and nickel oxide nanofilms make excellent catalysts, Kolar explains, “because they increase the rate of the chemical reaction between the odor-causing compounds and the ozone, making the process more efficient. They are also metals that are both readily available and relatively inexpensive.”

Kolar  says his next goal is to apply this research to industrial hog farms. “This technology could be applied to swine operations to
address odors and ammonia emissions,” Kolar says. “My next step is to try to pursue this research on a large scale.”

The research, “Room-Temperature Oxidation of Propanal Using Catalysts Synthesized By Electrochemical Deposition,” is published in the August issue of Transactions of the American Society of Agricultural and Biological Engineers.

Note to editors: The study abstract follows.

“Room-Temperature Oxidation of Propanal Using Catalysts Synthesized By Electrochemical Deposition”

Authors: Praveen Kolar, North Carolina State University; James R. Kastner, University of Georgia

Published: August 2009, Transactions of the American Society of Agricultural and Biological Engineers

Abstract: Poultry rendering emissions contain aldehydes that are reactive and regulated volatile organic compounds requiring mitigation. This research presents an application of catalytic oxidation technology to treat aldehydes at room temperature using ozone as an oxidant and metal oxides deposited on activated carbon as catalysts. Four types of catalysts were tested: activated carbon, activated carbon impregnated with iron oxide, and activated carbon electrochemically deposited with nickel and cobalt oxides. Iron oxides were deposited on activated carbon via traditional dry impregnation, while nickel and cobalt were deposited on activated carbon via electrochemical deposition. The prepared catalysts’ activities were tested in a continuous differential packed-bed reactor, using an ozone generator and gas chromatography. Propanal (50 to 250 ppmv) was tested as a representative contaminant, and ozone (1500 ppmv) was used as an oxidant. Experiments with activated carbon as a catalyst indicated that 70 percent removal was achieved within 0.1s residence time, and the oxidation rates of propanal were determined to be in the range of 90 x 10-9 to 300 x 10-9 mol/g-s. However, when iron oxide deposited activated carbon was tested for propanal oxidation, the oxidation rates decreased significantly (7 x 10-9 to 60 x 10-9 mol/g-s), probably due to the clogging of the micro- and meso-pores of the activated carbon support with iron oxide particles. When the electrochemically deposited nickel and cobalt oxide catalysts were tested, propanal oxidation rates increased by 20% to 25%. Based on the preliminary results, electrochemical deposition on activated carbon appears to be a valuable tool in synthesizing advanced catalysts for use in air pollution remediation.