Hog odor and hydrogen sulfide (H2S) emissions from outside manure storage facilities and from hog buildings vary widely, according to a report from a University of Minnesota research team.

The team concluded the different ranges for odor and H2S support earlier work by research leader Extension ag engineer Larry Jacobson in which he found little correlation between odor and H2S levels.

In the latest study of 29 farms in three, 30-mile-diameter clusters around Minnesota, the sources of odor and H2S were identified for outdoor manure storage units and confinement buildings on hog, dairy, beef, turkey and broiler operations.

H2S levels were measured for most of the samples collected because of the state's regulatory standard for the gas. Data collected is expected to be used for predicting odor and gas concentration levels downwind from livestock operations.

Because of seasonal effects seen in earlier research, it was decided to sample from each site in spring, summer and fall. Samples were collected in 10-liter tedlar (type of plastic) bags at the source of the odor or gas. Air samples were analyzed for H2S using a Jerome meter. Odor samples were analyzed within 30 hours of collection by olfactory testing using a panel of eight people.

Overall, odor concentrations in the air emitted from buildings ranged from 20 to 1,500 odor units and H2S levels ranged from 10 to 1,200 parts per billion (ppb).

Emission rates of odors and gases exhausted from buildings were also highly variable.

Values ranged from 0.1 to 30 odor units (calculated by multiplying odor units times air flow rate divided by area). H2S values ranged from 0.1 to 26 (a measure of microgram/second/square meter).

Odor and H2S concentrations and emissions from pig buildings were about one order of magnitude (a factor of 10) higher than those detected from dairy and poultry buildings. Odor and H2S levels for manure storage units were also higher for pigs than for dairy.

Researchers: Larry Jacobson, Richard Nicolai, David Schmidt and Jun Zhu, University of Minnesota. Phone Jacobson at (612) 625-8288.