David Schmidt, Extension Engineer
Larry Jacobson, Extension Engineer
Kevin Janni, Extension Engineer
Department of Biosystems and Agricultural Engineering
Copyright © 2001 Regents of the University of Minnesota. All rights reserved.
Minnesota Rules Relating to Animal Feedlots and Storage, Transportation, and Utilization of Animal Manure, Chapter 7020.0505 Subpart 4 B, requires feedlots with 1,000 animal units or more to submit an air emission plan. This plan must include:
This air emissions plan must address odor specifically but may also include dust and specific gases such as hydrogen sulfide and ammonia. Although this air emission plan is only required for those sites over 1,000 animal units, all feedlots should consider writing such a plan. An odor management plan helps avoid nuisance odor conflicts and shows the intent to be a good neighbor. This publication presents information on preparing odor management plans for farms of any size.
Manure management plans have become a standard practice for most animal production systems. These plans document the proper handling and application of manure onto cropland. Likewise, odor management plans systematically identify potential odor sources, determine control strategies to reduce these odors, and establish criteria for implementing these strategies.
The development of an odor management plan consists of the following four steps:
(A guide can be found below.)
Nuisance odors can be the result of a single odor source, a single odor event, or the combination of several sources and events. Therefore, it is important to conduct a thorough inventory of all odor sources on the farm. This inventory should be conducted on-site in a systematic way to ensure that all odor sources are included.
Odors from an animal production site originate from three primary sources: manure storage structures, animal housing (including open lots), and land application of manure. However, other sources such as dead animal disposal sites, silage piles, feed centers, and any other areas where organic matter is present may also contribute to odor emissions. These other odor sources are often overlooked in discussions about nuisance complaints. For instance, improperly managed dead animal disposal sites can generate significant amounts of odors. Intermittent odor events (e.g., manure agitation) should also be listed in the odor inventory because often these events, though infrequent, can be the source of significant odor emissions and thus generate odor complaints.
A brief description of each odor source should be included in the inventory. This description should include the size of the odor source (physical area) and its distance and direction from roadways, neighbors, property boundaries, etc. (See shaded box below.)
*Taken from Livestock and Poultry Odor Workshop Manual II, Department of Biosystems and Agricultural Engineering, University of Minnesota, 2000
Earthen basins are designed for manure storage only. A properly designed treatment
lagoon may have far less odor.
A good odor management plan must also identify which of the many on-farm odor sources have the highest potential to create nuisance odors.
Research has shown that some odor sources emit more odor per unit area than other sources (Tables 1 and 2). Therefore, both relative odor emissions and the size of the odor source must be considered in determining the high odor sources. Intermittent sources, such as liquid manure agitation and pumping or land application, also cause relatively high odor emissions and should be considered in the development of a list of high odor sources.
Another factor to consider in determining high odor sources is the proximity of the sources to public areas or neighbors. Dilution of odors is caused through the mixing of odors with ambient air. This dilution of odorous air is a function of distance, topography, and meteorological conditions. Farther distances between odor sources and the public will result in fewer nuisance complaints. Topographical features can either enhance dilution or reduce dilution depending on the particular feature. Wind breaks or tree lines will encourage mixing of the odorous air with clean air, whereas valleys or low areas may reduce odor dilution. Meteorological conditions also affect dilution. Maximum dilution occurs when the cool air near the ground is heating and rising. Conversely, during the late evenings when it is calm and the atmosphere is cooling, the odorous air is trapped near the ground and there is little dilution. Of these three factorsÑdistance, topography, and meteorologyÑseparation distance will likely have the biggest impact on nuisance complaints.
Figure 1. Biofilter on exhaust fans for odor control.
Figure 2. Manure storage cover for odor control.
Odor control technologies can be thought of in three different categoriesÑthose that reduce the generation of odors, those that decrease the emission of odors, and those that increase dilution of odors. Several of these technologies are listed in Table 3. (See also the shaded box) Since there is little known about many of these technologies, the odor management plan should list one, two, or possibly three control technologies for each of the high odor sources. If the first odor control strategy proves ineffective, then the second or third strategy can be implemented.
Control technologies that reduce the production or generation of odorous gases include: manure treatment technologies such as anaerobic digesters or aeration systems, diet manipulation to reduce the amount of manure produced or the amount of nutrients in the manure, or chemical or biological additives. Manure treatment technologies can be very effective at odor control but are typically expensive. Chemical additions can also be effective, and the cost depends on the specific chemical and the frequency of addition. Biological additives are typically less expensive than manure treatment or chemical additives, but their effectiveness often varies by farm site and particular additive.
Technologies considered to reduce emissions are those that capture and treat the odorous gases before they leave the site. In most situations these gases are converted through biological, physical, or chemical processes to other non-odorous gases. Biofilters are a good example of a technology that reduces odor emissions. A biofilter treats the odorous gases as they are emitted from an odor source. Microorganisms in the biofilter media oxidize these complex odorous chemicals into simple odorless compounds. The air emitted from the biofilter is nearly odor free.
Technologies that disperse and dilute odors include shelterbelts, windbreak walls, and setback distances. Of these, setback distances are the most effective. New information on shelterbelts suggests that some odor reduction occurs because of the increased turbulence caused by the windbreak and because of some capturing of the odorous gases on the tree foliage.
In accordance with the Americans with Disabilities Act, this material is available in alternative formats upon request. Please contact your University of Minnesota Extension office or the Extension Store at (800) 876-8636.