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2004 Swine Research Review

Manure/Odor Control

Test of Farrowing Environments Reveals No Clear-Cut Winner

Growing concerns over odor and gas levels being released from pig production units has led agricultural engineers across the U.S. to test a variety of facilities to determine actual air emission rates.

In doing so, engineers are accumulating data on emission rates for gases (ammonia and hydrogen sulfide), particulate matter (dust) and odor concentrations, to determine their impact on existing and potential state and federal regulations and public nuisance concerns.

Studies at the University of Minnesota West Central Research and Outreach Center near Morris, MN, compared a deep-bedded “Swedish” style farrowing facility and a conventional-crated farrowing facility.

Hydrogen sulfide and odor levels were highest from the conventional deep-pit barn. Ammonia emissions recorded were higher from the deep-bedded barn during the summer farrowing, but ammonia levels were otherwise similar to the deep-pit barn in other months.

Particulate matter and odor emissions were higher for the conventional, deep-pitted farrowing barn.

The “Swedish” farrowing barn was built in 2002 and includes three farrowing rooms (eight sows/room) with a 33-sq.-ft. solid floor that is heavily bedded. At the start of farrowing, solid partitions that form 6×8-ft. cubicles are placed along the outside walls for use by sows and piglets, as desired. PVC pipes are placed at the bottom of cubicle doors to keep piglets inside for the first 10 days after farrowing.

After 10 days, the cubicle partitions are removed and sows and pigs are permitted to commingle at will.

The conventional farrowing facility was built in the 1970s and features two rows of eight crates. An 8-ft.-deep manure pit is pumped once a year.

For the study, data was collected from October 2003 to June 2004, spanning four farrowing cycles and covering all seasons. Ammonia and hydrogen sulfide levels were monitored continuously in both buildings. A 24-hour particulate matter sample was collected weekly, while an odor sample was taken once during each farrowing cycle.

The daily mean values for ammonia and hydrogen sulfide emissions for the November farrowing period for the deep-bedded barn and the deep-pit barn are shown in Figures 1 and 2, respectively.

Figures 3 and 4 show measurements recorded for the June farrowing period for the deep-bedded barn and deep-pit barn, respectively.

Overall, for the summer farrowing cycle, ammonia emissions were about two times greater in the deep-bedded barn than the deep-pit barn on an animal unit (AU) basis. One AU equals 1,100 lb.

But during the other seasons' ammonia emission rates were found to be quite similar for the two barns; the lowest emission rates occurred in winter.

Hydrogen sulfide emissions were very low in the bedded barn, while gas levels from the deep-pit barn were highest during the summer farrowing period. Around 80% of the hydrogen sulfide gas exhausted from the deep-pit barn exited via the pit fans, with the rest going out the sidewall fans.

Particulate matter emissions were lowest in winter and spring farrowings and were found to be slightly higher in the deep-pit barn.

Odor discharges were very low from the deep-bedded facility, averaging 85% less than the deep-pit barn.

The cost-benefit analysis of this information is difficult to evaluate, but could be sizable if limits on certain emissions are implemented.

Researcher: Larry D. Jacobson, University of Minnesota; phone Jacobson at (612) 625-8288; fax (612) 624-3005; or e-mail

Click to view graphs.