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Keeping lid on farm, livestock odors

Farm goals should include economic viability, environmental soundness and social responsibility. These three factors impact the future of an individual farm, and in general, farming in a community. Acknowledging these three goals helps a farm succeed and have a positive impact within its community.

Odor from livestock is not regulated by the U.S. Environmental Protection Agency; therefore, controlling odors and limiting their impact on rural residents is a component of social responsibility. In Michigan’s rural communities, livestock production and the resulting odor is often accepted as a normal outcome of farming activities. That acceptance does not relieve livestock farms from the responsibility of minimizing odor nuisance.

More than 200 compounds (odorants) have been identified as components of manure odor. Odor detection panels have labeled many of these compounds as very offensive at very low concentrations. These odorous compounds are produced during the anaerobic degradation of manure organic matter and include a wide variety of compounds including volatile fatty acids, aldehydes, alcohols, phenols, indoles, mecaptans and amines. Knowing which compounds are the primary culprits of livestock malodors remains uncertain. As a result, most management practices aimed at minimizing odor nuisance focus on limiting the production of odorants or providing an environment for microbes to break down odorants to their base elements of carbon, hydrogen, nitrogen and oxygen.

Key Points

• Controlling odor nuisance is part of a farm’s social responsibility.

• Animal manure contains more than 200 odorous compounds.

• Farmers can take steps to control odor and improve their landscapes.

Controlling odorous compounds

Some methods to minimize odors include the following:

Biofilters use carbon-rich media to capture odorous compounds while encouraging the microbial activity necessary to break the compounds down. “Biofilters” are often associated with permanent structures that capture and retain ventilated air from livestock housing. In reality, the microbial activity encouraged by biofilters may be implemented and utilized in other areas of the farmstead. Blowing a clean straw cover, or other similar carbon source, on outside manure storages will create a similar microbial effect and limit odor. Research suggests that blowing straw on in late spring or early summer and again in July or August will create a cover that lasts throughout summer’s peak outdoor activity. Because straw can only be blown a limited distance, and high winds can move straw, straw covers are less effective on large manure storage structures.

Crusts that sometimes form on the top of manure storage are natural odor filters. Crusts should be encouraged by limiting surface activity, and left intact as late into the summer or fall as possible when the likelihood of interfering with neighbor activities decreases.

Planting trees and establishing vegetative buffers, or shelterbelts, help with odor control by retaining odor particles and dust on their foliage. The microorganisms that dominate these plant surfaces may breakdown odor-causing compounds. There is a size and density relationship between the size of the tree, density of the foliage and the corresponding odor reduction. Small immature trees are less effective than larger, mature rows of vegetation. Guidelines suggest shelterbelts must be 20 to 30 feet tall for full effectiveness. Planting individual trees will improve eye appeal, but will supply limited odor relief.

A well-kept, landscaped farmstead may be more than just eye-appealing. Standing water, ponded feed storage runoff, uncontrolled lot runoff and stacked spoiled feed go through the same anaerobic processes as stored manure, producing the same odor. These odors add to the odors associated with livestock farms. Limiting the amount of rain contacting feed storage areas and feedlots — then controlling precipitation that does run off these surfaces — helps control total farm odor.

Incorporating manure when applying it to fields reduces odor and helps retain the manure nitrogen in the soil. Much like biofilters, incorporating manure in the soil captures the odorous compounds on soil particles where they are broken down by microbial activity. Often, the nitrogen portion contributes up to 50% of its crop nutrient and economic value.

MidWest Plan Service bulletins report that 10% to 25% of the ammonium-N in liquid manure will be lost if left exposed on soil surface for up to 96 hours. If manure is immediately incorporated after application, less than 5% of that N will be lost. Even less N is lost (less than 1%) if the manure is totally covered when injected. Incorporating and injecting manure are sound agronomic practices that also pay large dividends in odor control and neighbor relations.

Livestock odors are a natural result of farming activity. Implementing management practices intended to limit and control odors improves a farm’s image in the community and acknowledges the farm’s social responsibility.

May is a Michigan State University Extension pork educator.

This article published in the March, 2010 edition of MICHIGAN FARMER.

All rights reserved. Copyright Farm Progress Cos. 2010.