With increased scrutiny of the livestock industry and an influx of nuisance lawsuits filed by neighbors, managing odors has become a top priority for livestock producers.

First, let’s go over what we know about livestock odors. Over 160 compounds make up the scent of livestock, creating a very complex odor. Due to the complexity, it is extremely difficult to measure these odors beyond the human nose. Gases such as hydrogen sulfide and ammonia make up a small portion of livestock odors.

Livestock odors are typically associated with three different sources. Odors from livestock farms can be found in and around the animal barns, manure storage facilities or from the land application of the manure nutrients.

How can you better manage odors from your operation? 

Odor can be minimized with various management techniques. Minimizing the manure storage surface area, covering manure storage facilities, reducing dust and feed wastage inside buildings, increasing air exchange, filtering odorous air, modifying diets, utilizing pit additives and incorporating manure during land application all help minimize odors.

Over 60% of Iowa producers utilize a “100% containment of manure” system. These systems greatly reduce odors by storing manure below the buildings in concrete structures, out of the wind. They also allow the producer to fully utilize the nutrients as crop fertilizer.

Limiting agitation time. Agitating manure in the storage facility is necessary prior to application to assure consistent nutrient application rates, however, agitation does create added odor. Limiting the time of agitation, yet creating a consistent slurry, minimizes the amount of odor created.

Limiting the pump outs per year. Using adequately sized manure storage structures allows minimizing the number of times per year that manure is land applied.

Most hogs produced in Iowa are raised on farms that have a DNR Manure Nutrient Management Plan on file. A manure management plan limits the amount of animal nutrients applied to land to only the nitrogen nutrients needed by the crops that will be produced, drastically reducing the risk of over application and potential run-off.

Reducing water and feed losses. Higher feeding efficiency reduces the loading rate of contributors into the manure storage system. Efforts to reduce the spillage of feed and water also reduce odor emission.

The Midwest Planning Service has created a book entitled Outdoor Air Quality. The charts below explaining the various treatments and processes to control odor are credited to this publication. 

Reducing odors during land application

Injection and incorporation
Injecting manure into the soil is the most effective way to reduce odor during the application of untreated liquid manure. The other common option is to simply spread liquid manure on the surface and immediately incorporate the applied material into the soil.

Treated manure
Treated liquid manure may be less offensive than raw or untreated manure. Liquid manure can be treated either aerobically or anaerobically. Research indicates odor reductions of 80% or more during anaerobic digestion and 90% during aerobic treatment.

Treating manure in pits
Pit agitation is another factor that contributes to odor and gas emissions during application. The best method for reducing the impact of these odor emissions is to agitate during times when outside air is heating (sunny clear mornings), causing the odorous air to rise and disperse.

The Midwest Planning Service prepares publications under the direction of agricultural engineers and consulting specialists. It is an official activity of Iowa State University and the U.S. Department of Agriculture. To order “Outdoor Air Quality,”  call 1-800-562-3618 or visit the MWPS website at www.mwpshq.org. The cost is $17 plus shipping and handling.

Odor Research — Funded through the Pork Checkoff

Each year the IPPA and the National Pork Board, comprised of pork producers, supports and funds research that is focused on finding solutions to current and emerging issues affecting the environment. Below is a listing of some of those research projects.


Air Quality

Types of bedding material, frequency of adding bedding and amount of bedding may greatly affect the air quality generated from hoop buildings.
   *J. Harmon et al, Iowa State University 
Based upon H2S data collected during manure agitation and land application from deep pit swine barns, compliance with the Minnesota ambient air standard for any size of producer would be difficult. The Minnesota Pork Producers were able to use this data to benefit producers by getting the standard revised.
   *National Pork Board 
Most methods involving some soil incorporation of liquid swine manure reduced odor levels up to 90% from the odor level emitted after broadcast application.
   *H. Hanna et al, Iowa State University 
Based on the finding of this study, there is no evidence that salmonella organisms excreted in the feces of infected swine pose a health risk to neighbors by airborne dissemination from the swine facility.
   *G. Bowman et al, The Ohio State University

Nutrient Utilization

The combination of phytase and low-phytate corn diets resulted in a 51% reduction in phosphorus excretion.
   *G. Cromwell, University of Kentucky 
Reducing crude protein and supplementing diets with synthetic amino acids can be an effective way to control ammonia and odor emissions from confinement buildings.
   *A. Sutton et al, Purdue University 
Distillers dried grain with solubles should be considered an economical feed ingredient by swine producers who purchase protein sources for their livestock enterprise.
   *W. Powers et al, Iowa State University 

Soil and Water Quality

Constructed wetlands as an additional treatment for secondary lagoon water has been shown to significantly reduce pathogens and nutrients from swine waste.
   *M. Sobsey et al, University of North Carolina at Chapel Hill 
Safely composting swine mortality in roofed compost systems can be effectively completed using either ground straw or ground corn stover as an alternative to sawdust.
   *S. Moeller et al, The Ohio State University

For more information on odor research, contact:

Iowa Pork Producers Association,
800-372-7675 or www.iowapork.org

National Pork Board,
800-456-7675 or www.porkboard.org

IPPA has developed a fact sheet explaining these and various other air quality initiatives pork producers have taken to reduce odors from their operations. The fact sheet also lists these checkoff funded research projects that are focused on finding solutions to livestock odors. To request a copy of this fact sheet, call (800) 372-7675 or visit our fact sheet page to download a copy.