RAPP Technology for Control of Gas and Odor from Swine Manure Pits

Reprinted, with permission, from the proceedings of: Mitigating Air Emissions From Animal Feeding Operations Conference.

The proceedings, “Mitigating Air Emissions from Animal Feeding Operations”, with expanded versions of these summaries can be purchased through the Midwest Plan Service.

This Technology is Applicable To:

Species: Swine
Use Area: Manure Storage
Technology Category: Chemical Amendment
Air Mitigated Pollutants: Odors, Ammonia, Carbon Dioxide, Sulfur Dioxide

System Summary

This gas and odor reduction technology, Rapp Technology, consists of an oil cover and a neutralizer that is an alkaline solution. The laboratory study in swine manure reactors to simulate deep manure pit demonstrated statistically significant reductions of ammonia, carbon dioxide, sulfur dioxide, and odor from the treated reactors. Compared with previously tested commercial manure additives, this technology is more effective in mitigating gas and odor emissions from simulated deep manure pits.

Applicability and Mitigating Mechanism

  • The oil cover is added at initial application. It floats on the surface of the manure slurry to slow the releases of gases and odorous molecules while allowing excrement to pass through.
  • The neutralizer solution is injected beneath the oil cover periodically. It neutralizes the volatile fatty acids and phenols in the slurry to their ammonium salts. Such salts are more prone to stay in the aqueous slurry because they are more water-soluble and less volatile than the original acids.



  • The oil cover is not suitable for applying on the manure on the barn floors.
  • The effect of neutralizer on emission reduction could not be differentiated from the effect of oil cover in the lab test.
  • Future high quality field studies are needed.


During the lab test, the oil and the neutralizer (both by Custom Formulating & Blending, Bristol, IN) cost $1.13 and $ 0.67 per reactor, respectively. According to Juergens Environmental Control (Carroll, Iowa) for field application of the neutralizer, the fixed cost of the system for 1000 to 8000-pig finishing operations averages $2.50 – $5.00 per pig per 3-year term (shipping and labor not included). The cost of neutralizer operation averages $ 0.01 per pig per day over one year.


Ji-Qin Ni1, Sam Hanni1, Albert J. Heber1, Warren M. Kosman2, Gary Rapp3, 1Purdue University, 2Valparaiso University, 3Juergens Produce and Feed Company
Point of Contact:
Gary Rapp, garyrapp@westianet.net

The information provided here was developed for the conference Mitigating Air Emissions From Animal Feeding Operations Conference held in May 2008. To obtain updates, readers are encouraged to contact the author.