Proposed state regulations for gaseous emissions from livestock and poultry facilities mean understanding which specific compounds contribute to odors and how environmental conditions and distance affect odors is gaining importance in the state of Iowa. The subject was the focus of recent research at Iowa State University (ISU) that led to the creation of mathematical formulas that can predict odor and gas concentrations under various conditions.
In the study, air samples were collected at and downwind from Iowa dairy, poultry, and swine facilities during two ten-week periods, one from May through July 2001, and the other from May through August 2002.
Odor was measured using an "electronic nose" and a Jerome meter for hydrogen sulfide concentrations. Using these tools, researchers determined how much unscented air had to be mixed with the collected air samples in order to make the odor almost unnoticeable.
The air samples they collected were analyzed using olfactometry and gas chromatography.
Most of the study's findings weren't too surprising: of the gases monitored, hydrogen sulfide was found to be most closely correlated to odors; higher temperatures and higher humidity caused stronger odors; and with other conditions equal, odors were stronger on sunny days than on cloudy days.
What is interesting is that at distances of 50 meters or more downwind from the facilities, the hydrogen sulfide measurements were generally within the limits that may become law.
Also interesting is the fact that predicting odors remains a somewhat inexact science.
"We had two facilities right next to each other, managed by the same people with the same practices," said Wendy Powers, animal scientist and lead investigator in the study.
"We would have thought they would have had similar odor and gas levels, but one was much higher than the other."
This research was sponsored by the Iowa Pork Producers Association, the Midwest Poultry Consortium, and the Animal and Poultry W aste Management Center at North Carolina State University.
