Measuring Odors From Livestock
Chemist Dick Pfeiffer uses a gas chromatograph/mass spectrometer to analyze
compounds in odors collected from a swine production facility.
Complaints about nuisance livestock odor in rural areas have become a
problem nationwide. Scientists for the U.S. Department of Agriculture's
Agricultural Research Service are
working to find new ways to tackle the smelly dilemma.
James A. Zahn, a microbiologist formerly with the Agricultural Research
Service at the National Soil Tilth Laboratory in Ames, Iowa, developed a way to
collect air samples for scientific analysis. He is now with Iowa State
"There is little basic understanding as to what causes the different
odors that are detected around livestock operations," says Zahn. "We
can't evaluate methods to control odor until we understand the makeup of the
Zahn devised a mechanical air-sampling device that can be transported to the
site where odors originate. The device uses an absorbing tube and a pump to
draw in a specific quantity of air. To date, Zahn has identified more than 200
volatile organic compounds, gases, and airborne particles from samples taken
near livestock operations.
The most common method of storing and processing livestock
manureespecially hog manureis by storing it in large lagoons or
deep basins. These are anaerobic, or no-oxygen, environments. There, the manure
breaks down into organic components including hydrogen sulfide, acids, ammonia,
phenols, and indoles, which together create the telltale odor some people call
According to Jerry L. Hatfield, who leads research at the Ames lab, the
secret to defusing odors is determining what makes them smelly. So far, 27
different chemicals that create hog manure odors have been identified using
Zahn's device. Hatfield says the laboratory work isn't very popular. "We
can duplicate livestock manure odors in the lab," he says. "That
doesn't smell very good, but it gives us clues that we are on the right track
toward understanding how odors are formed."
The goal of the research, done in conjunction with the National Pork
Producers Council, is to find ways to scientifically measure the stink factor
in livestock manure and reduce or eliminate it.
There is currently no measurable standard for nuisance odorsonly the
human nose. "This isn't a replacement for the human nose," says
Hatfield, "but it does give us a research tool to quickly and objectively
assess odors." Older methods of odor analysis were time consuming, labor
intensive, and messy.
The human nose is capable of discerning only one or two odors at a time and
can be easily overwhelmed by pungent odors like ammonia, the gaseous nitrogen
compound. Individual compounds may not be offensive by themselves, but they
could take on offensive traits when mixed.
Detection is only one component of the odor problem. Scientists also monitor
weather conditions, air and ground temperature, and soil conditions in and near
hog farm manure lagoons and pits to learn more about odor. The results of the
research may lead to improved farm management practices to keep odors in
Lyons-Johnson,Agricultural Research Service Information Staff, 1815
North University Street, Peoria, IL 61604, phone (309) 681-6534.
For more information, contact Jerry L.
Hatfield, USDA-ARS National Soil Tilth
Laboratory, 2150 Pammel Dr., Ames, IA 50011; phone (515) 294-5723, fax
"Measuring Odors From Livestock Operations" was published
in the April 1998 issue of Agricultural Research magazine. Click here to see this
issue's table of contents.