Swine stench begone

Pork producers evaluate 8
odor-reducing products for manure pits

By Andrea Frazeur

Reducing odor in swine manure pits isn't just hogwash, says a group of Minnesota hog producers.

AURI and a committee of independent pork producers calling themselves AD-HOC, "A Determined Hog Odor Control Committee," completed a full year of odor study on eight pit additives and concluded that they can significantly reduce levels of ammonia, one of the culprits in swine stink.

For each of the eight products the group tested, they found ammonia levels in large hog facilities were reduced by about 50 percent. "We're not out to compare these products," says Jack Johnson, AURI waste utilization manager. "This study gives companies and livestock producers information on how the products work on the farm, not just in the laboratory."

Smelly pits
Reducing livestock odors is a serious issue in Minnesota, which ranks third in U.S. pork production and second in turkey production. With more large-scale confinement buildings popping up around the state, rural residents downwind are increasingly offended and concerned over the stench.

At present, the Minnesota Department of Health is determining compliance on air emission levels for hydrogen sulfide and is likely to also look at ammonia. Farmers worry that if they don't take action to reduce hog odor on their own, government will set regulations for them.

"The public's interest in hog odor has increased in the last year," says David Priesler, executive director of the Minnesota Pork Producers, "but the pork industry is also beginning to learn more about hog odor."

Farmers continue to adopt management practices to reduce hog odor, from careful site selection for new facilities, to planting trees, to communicating with neighbors when the pit must be pumped and the manure spread on fields.

In addition, over 150 different companies now sell products and technologies that claim to reduce hog odor. There are deodorants to mask the smell, feed additives to curb odors from hogs' digestive tracts, manure additives to effect rapid decomposition, and absorbents to soak up odors.

Dig deep for answers
The committee recognized that many Minnesota hog operations use deep pits, basement-type structures that hold a one-year supply of manure. They decided the study would focus on pit additives, which "will probably be playing a bigger role in solving (odor) problems," says AD-HOC member Robert Mensch, Fairmont.

With guidance from AURI's Johnson, the hog producers followed a scientific protocol using large hog setups with multiple identical barns. Hog genetics, management techniques, heating, ventilation and the number of hogs in each facility were kept the same. One barn was treated with a pit additive, while a second, adjacent barn was left untreated as a control.

Air Johnson
Originally, Johnson planned to hang flannel swatches in barns to be analyzed by an odor control panel. The swatches quickly became saturated and indistinguishable, so Johnson took another route to collect accurate odor samples.

He collected air samples using an AeroVironment pulse air pump. The pump sucked air into a sample bag every 6 to 9 seconds for more than three hours. Johnson then transported the bags to the University of Minnesota for odor evaluation.

Johnson obtained ammonia samples using diffuser air tubes placed three feet off the floor and one third of the way into each barn. Farmers removed the tubes that had been in the barn more than three hours. Johnson recorded ammonia readings as well as date, barn location, indoor and outdoor temperatures, wind direction, wind speed, and fan settings. For each test, both treated and control barns were sampled 20 times.

Johnson obtained manure samples to measure total nitrogen, ammonia nitrogen, phosphorous and potassium values of treated and untreated manure. Progress notes were kept for each farm, noting cost per hog to treat the barn, ease of treatment use, manure crusting and solids buildup. Results indicate that the pit additives tested have variable effects on hog odor reduction. All products reduced ammonia and solids in the manure pits.

"This is by no means a definitive list of hog odor reduction products," Johnson says. "It is a starting point, the beginning of an era of on-farm testing to find solutions to livestock odor."

Jack Johnson at AURI's waste utilization pilot plant in Waseca.