Minnesota/Wisconsin Engineering Notes

February 2004 Postharvest and Alternative Energy Info on Web Your Farm Doesn’t Have to Smell that Bad Science-based Information on Manure Management Issues Competitive Milking? Bedded Pack Housing For Dairy Cows Livestock Ventilation Design—Indoor and Outdoor Air Quality Concerns EDEN – Extension Disaster Education Network Workshops on Food System Terrorist Threats Irrigated Acres Update New Book and Companion CD Focus on Dairy Replacements Resources Calendar

Your Farm Doesn’t Have to Smell that Bad Brian J. Holmes, Wisconsin Extension Engineer Complaints about farm odors have increased in recent years, especially for larger livestock operations. There are several reasons for this including increasing population in rural areas and adoption of technologies that increase odor production. Practices such as building freestall barns with wide manure alleys, maintaining large outside yards, storing manure, and applying large amounts of manure from storage onto large fields can increase odorous compounds released from manure. The odorous compounds can be reduced 50-90% while using these technologies by adopting different management practices. For example, an Iowa study found the odor detection threshold (ODT*) for swine manure was reduced from 2820 down to 32 by switching from surface spreading to injection during application. Disking following surface application reduced the ODT to 130. Field application of manure results in many complaints about odor. If a livestock producer wants to reduce odors (and complaints) during manure application, injection or incorporation within an hour after surface application will go a long way toward accomplishing that objective. Odors can originate from many sources in addition to those mentioned above. Feed storages, deteriorating feed, dead animals, burning trash, as well as wet and dirty animals can contribute to odors emanating from a farm. Adopting specific management practices can reduce the impact of odors on neighbors and the community. These practices include reducing the source, reducing the odor production rate, and removing odorants from the air. Examples of reducing the source include manipulating animal diets to limit odorous-compound production from manure, cleaning manure frequently from alleys and yards, preserving feed properly and disposing of waste feed, managing so as to limit the number of animal deaths and removing dead animals from the farm as quickly as possible, and halting trash burning. Some examples of reducing the odor production rate are covering the surface of a manure storage, incorporating manure into the soil during application, reducing the size of the animal lot, constructing lots that drain runoff water, treating manure to make it more biologically stable (composting, anaerobic digestion, aeration, etc.), and spraying oil onto surfaces in swine barns to suppress dust release into the air. Odorants can be removed from the air by blowing exhausted ventilation air through a biofilter, intercepting dust on vegetation, biomass walls, and air scrubbers, and treating with ozone. So, there are methods for reducing the impact of odors on neighbors and the community. You can learn more about options for reducing odors and doing a management assessment in Outdoor Air Quality, MWPS-18, Section 3. For ordering information see Resources. *Odor Detection Threshold or ODT is an estimate of the number of dilutions of clean air needed to make the odor “non-detectable” by the human nose. A lower number is more desirable.

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