Engineering Notes Index

Minnesota/Wisconsin Engineering Notes
Summer 1998

Odor Control Technologies for Animal Production Units

Larry Jacobson and David Schmidt, Minnesota Extension Engineers

Introduction

Much has been written about outdoor air quality and odor concerns in and around livestock and poultry production units in the upper Midwest. Not much, however, has been published on odor control solutions that are applicable to most animal producers in Minnesota, Wisconsin, Iowa, and North and South Dakota. An update, Odor Control for Animal Agriculture, BAEU-17, has just been completed at the University of Minnesota which summarizes available and appropriate odor control technologies for various manure storage units and livestock and poultry production systems. The update will be available on the University of Minnesota Biosystems and Agricultural Engineering Department web site (www.bae.umn.edu).

Several known technologies can significantly reduce odors from livestock production. These technologies range from simple to complex, from low to high maintenance, and from inexpensive to expensive. Some of these technologies have shown odor reduction based on scientific measurements while odor reduction from other technologies is supported only by anecdotal evidence and testimonials. The spectrum of available technologies is discussed in this article and in BAEU-17 with indication as to what type of evidence and information is available for each control method. Although anecdotal evidence is useful, it should be verified where possible with actual measurements.

Odor reduction during land application

Land application of manure typically results in the largest number of odor complaints. Practices which have been shown to reduce odors during land application of manure are listed below:

• Injection of manure directly into soil.
• Surface application (within several inches of soil) of manure in crop canopy.
• Incorporation of manure into soil with tillage immediately after surface application of manure.

The following materials have either positive preliminary research results or anecdotal evidence of odor reduction during the agitation of manure pits and storage units prior to land application:

• Manure pit and feed additives.
• Ferrous chloride added to pit immediately prior to agitation of pits.

Odor reduction from manure storage

Manure storage units are the most “apparent” odor source on many farms, especially if there is no visual barrier of the storage system from neighbors or passersby. Open storage systems are the most susceptible to seasonal effects as well as day-to-day weather changes.

Some odor control options which have been shown to be successful include:

• Covers, especially floating organic covers like straw.
• Anaerobic digestion, which works but has substantial costs and labor requirements.
• Aerobic treatment, which works but has high initial and operating costs.

Other odor control strategies for manure storage units which have positive anecdotal evidence and/or positive preliminary research results include:

• Manure and feed additives.
• Landscaping with trees and other plant materials to deflect and/or absorb odor plumes.

Odor reduction from buildings

Livestock buildings are a source of odors that is often overlooked. The most significant problem with reducing odors from buildings is controlling gas generation or capturing the gases before they are emitted into the atmosphere. Odorous gases are generated from manure-soiled flooring, animals, and from any manure stored below the flooring.

Practices known to reduce odor emissions from buildings include:

• Effective manure collection systems which eliminate or reduce manure accumulation on floors and slats.
• Use of large quantities of bedding (deep bedded systems).
• Use of biofilters to remove odors from ventilation exhaust air.
• Storing manure outside rather than beneath the building.

Other techniques which have shown some promising results include:

• Sprinkling vegetable oil daily inside the building to reduce dust and odor emissions.
• Non-thermal plasma treatment of ventilation exhaust air.
• Simple filtration of ventilation exhaust air.

Odor management plans

It is becoming a standard practice to have a manure management plan developed for an animal production system to document the proper handling and application of manure onto cropland. Likewise, in the near future, a similar “odor management plan” might be needed by animal producers to indicate what control technologies and strategies will be implemented to reduce odors. Knowledgeable individuals to make these assessments and develop the odor management plans are in short supply at the present time. As odor research and application of that research become available, more people will be able to make these decisions and assessments.

Summary

The debate will continue on how much odor control is enough. However, one fact remains: odors from animal production systems must be reduced significantly in order for producers to remain in business and still coexist with neighbors and the community. Several technologies are currently available to reduce odors, but unfortunately, economics often prohibit such technologies from being implemented. Currently, there is a substantial effort by university researchers, industry representatives, and producer groups to find and implement practical odor control technologies that are effective and yet manageable for the average animal producer.

This page is part of the Biosystems and Agricultural Engineering Department web at http://www.bae.umn.edu/