September 17th 2014

Controlling the Smell of Swine Facilities 

Odors associated with swine facilities can be a concern for both those inside the buildings and nearby neighbors. In addition, gases produced during the decomposition of manure and urine, as well as airborne particulate matter, can lead to poor health issues for both workers and animals.  

The Source of Odors

Odors refer to the smell that is created from a combination of airborne particulate matter, gases, and vapors:

  • Airborne particulate matter includes “dust” or particles of fecal matter, animal dander, feed particles, pollen, and mold.
  • The decomposition of manure and urine results in a number of gases, including ammonia, carbon dioxide, methane, and hydrogen sulfide.
  • Odors are produced when a gas, or multiple gases, combines with airborne particulate matter between 5 and 20 microns in diameter.
According the Kerr Center for Sustainable Agriculture, odors produced from swine facilities come from four main sources1 :
  • Land Application – 40%
  • Hog Confinement Building – 35%
  • Waste Storage and Treatment Processes – 20%
  • Carcass Disposal – 5%

Methods to Reduce Odors

Because odors can be made from a complex and diverse mixture of gases, vapors, and airborne particulate matter, regulating and controlling odors can be a challenging process. A number of methods have been established to help control odors associated with hog confinements, and many more are being tested. While new practices may develop that are more effective, the following have been shown to reduce odor2 emissions by researchers at South Dakota State University.


Diet Modifications

Swine diet modifications have the potential to decrease gas created during the anaerobic decomposition of manure, and in turn lessen odors, by reducing nutrients excreted. Low-protein and low-sulfur diets, as well as phase feeding, have been proven2 by the South Dakota State University researchers to reduce the production of gases, including nitrogen and hydrogen sulfide.


Control Airborne Particulate Matter

In addition to aiding in the creation of odors, airborne particulate matter has been linked to chronic bronchitis among hog confinement workers. One method that has been shown to decrease airborne particulate matter, while still maintaining cost-efficiencies, is oil sprinkling. Research3 by the University of Missouri has found that sprinkling vegetable oil, such as soybean oil, once a day in a swine-finishing barn considerably decreases airborne particulates at an overall operating cost of about $1 per pig space, or 40 cents per finishing pig.



Biofilters are structures made of organic materials that can be installed to fit the outlet of exhaust fans and are a useful way to capture odors. In fact, South Dakota State University researchers have been able to show biofilters reduce odor emission by 96 percent2. Additionally, eligible producers who install and maintain biofilters can receive $2.50 per animal4 unit for three years, with a 1,500 animal cap, through the USDA’s Environmental Quality Incentives Program.


New Technology

Continuous odor control is not always necessary, so installing a control system that works to regulate odor during critical periods can be a more practical option. According to National Hog Farmer, Impact-Based Odor Control5 (IBOC) technology has been tested in northern Iowa for the past three years and has been shown to be efficient in reducing odors while decreasing expenses.

This new technology utilizes a weather station, which helps determine atmospheric stability, humidity, temperature, solar radiation, and wind direction to help establish the potential impact. It also uses an on-off control that allows the biofilters to be used only when needed.


Manure Injection

The application of manure to farmland as a fertilizer accounts for around 40 percent of the odors associated with swine operations. Iowa State University researchers found injecting the manure below the surface of the soil instead of broadcasting manure can reduce these odors by more than 90 percent6.


Manure Management from MMP360

MMP360 can assist you in calculating the number of acres required for manure injection and the amount that needs to be applied to each acre based on your operation’s output. Register today for free to run your personal analyses and complete MMP forms required by the Iowa Department of Natural Resources.


1. Chapin, Amy, Charlotte Boulind, and Amanda Moore. Controlling Odor and Gaseous Emission Problems from Industrial Swine Facilities: A Handbook for All Interested Parties. N.p.: n.p., 1998. Kerr Center for Sustainable Agriculture. Web. 2 July 2014.

2. Hans Stein, Alvaro Garcia, Kent Tjardes, Charles Ullery, Stephen Pohl, Christopher Schmit. "Recommended Strategies For Odor Control In Confinement Swine Operations." Recommended Strategies for Odor Control in Confinement Swine Operations (n.d.): n. pag. South Dakota State University. Web. 2 July 2014.

3. Schmidt, Amy. "Dust, Odor and Gas Control in Swine Finishing Barns Through Oil Sprinkling." University of Missouri, Dec. 2004. Web. 2 July 2014.

4. United States Department of Agriculture. Natural Resource Conservation Service. Biofilters Now Eligible EQIP Practice., 2008. Web. 3 July 2014.

5. Vansickle, Joe. "Mitigating Manure's Odor." New Odor Control Technology for Hog Operations. National Hog Farmer, 20 Sept. 2011. Web. 22 July 2014.

6. Burns, Robert. "Land Application Practices to Minimize Odors."PorkCheckoff (n.d.): n. pag. National Pork Board - Iowa State University, 2000. Web. 2 July 2014.