Can’t leave odor issues up in the air


AMES, Iowa – With trends moving toward larger livestock and poultry farms, controlling odors, gases and dust has become a greater concern for producers and their neighbors.

“Larger and larger numbers of animals and birds concentrated onto single facilities create a significant amount of annoying odor that is generated on the farm and emitted into the local atmosphere,” said Albert Heber, professor of agricultural and biological engineering at Purdue University.

What smells? The primary sources of odor, gases and dust from animal production units are buildings or open lots, and manure treatment, storage and transport systems.

The public’s increasing intolerance of agricultural odors, coupled with the economic importance of animal agriculture, has researchers scrambling to find solutions.

Purdue agricultural engineers say there is little information available on the impact of odor and airborne contaminants from livestock and poultry operations, although more than 160 odorous compounds have been identified in dairy, beef, swine and poultry manure.

Health risks. Gases such as ammonia and hydrogen sulfide can affect human health if present at high levels.

“Every year in the Midwest, two to three farmers die from exposure to toxic gases generated in enclosed manure storage,” said Don Jones, professor of agricultural and biological engineering at Purdue.

In addition, some gases may have an impact on global warming and acid rain. According to Outdoor Air Quality, a MidWest Plan Service book, it is estimated that one-third of the methane produced each year comes from industrial sources, one-third from natural sources and one-third from agriculture.

Methane. In animal production operations, methane can be produced from the bacteria in liquid manure storage areas. Jones said that although animals produce more carbon dioxide, methane’s contribution to the greenhouse effect is estimated to be 21 times that of carbon dioxide.

Some states have established air quality standards that limit emissions of hydrogen sulfide and ammonia from livestock and poultry operations.

Vegetable oil. Producers can approach the problem in a variety of ways. Since dust carries gases and odors, dust reduction in and around buildings can significantly reduce odors.

By spraying a small amount of vegetable oil inside a confinement barn every day, a producer can reduce the amount of dust in the exhaust air, according to the book.

Purdue agricultural engineers say more than half of all odor complaints related to animal production are due to land application of manure. One way to reduce the odor from manure that is land applied is to inject or till the manure directly into the soil, Jones said.

Air quality model. Written primarily for producers, the book has an air quality model to help estimate the area over which air quality may be a concern for their operation and/or their neighbors.

Outdoor Air Quality is available for $17, plus shipping and handling, from the MidWest Plan Service, Iowa State University in Ames, Iowa.

For more information or to order the book call 515-294-4337 or log on to

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