Technology Type - Ammonia Stripping

Technology Strengths,Weaknesses and Critical Indicators

Ammonia-N can be harvested from manure and digestate using proven chemical/thermal processes:

  • Produces a concentrated source of nitrogen from a renewable source
  • Requires pre-treatment to remove coarse and fine solids
  • Pairs well with anaerobic digesters because digesters convert organic N into ammonium
  • Chemical storage required for process chemicals and final product
  •  Proven technology for nitrogen recovery, odor control, and pathogen reduction

image/svg+xml Nitrogen Recovery Phosphorus Recovery Storage Reduction GHG Reduction Odor Control Pathogen Reduction Negative Positive NEAT MATRIX - Peer Reviewed P - Documented D - Expert Opinion E P D E P D E

Overall Summary

Primary Application

  • Only appropriate for digested manure where combination of increased temperature and pH facilitate effective stripping; therefore, all bullets are contingent to this assumption.
  • Due to high capital cost, ammonia stripping is appropriate for consideration by farms with a very large number of cows or farms that co-process with poultry manure.
  • Pre-treatment to remove suspended solids is required for ammonia stripping; therefore, all bedding materials are acceptable.
  • Desirable manures will be high in ammonia-N.
  • Ammonia stripping can work in all climates with proper planning.
  • Coproduct is dilute liquid manure.
  • Optimally, the resulting ammonia product is used to replace commercial fertilizer for on-farm use or sale.

Economic/Return on Investment Considerations

  • Capital cost range is in the medium price range compared to other ammonia-N processes (reverse osmosis and biological treatment).
  • Estimated annual operating costs are also high due to the chemicals and electricity required.
  • No unintended consequences from ammonia-N recovery appear to exist.

Industry Uptake

  • Only a few demonstration systems operating on US dairy farms.
  • Only a few technology providers have systems commercially available in the US.

Technology Maturity

  • Ammonia-N stripping is a mature technology that is used extensively in commercial/industrial applications but has seen little uptake in animal agriculture to date.
  • Various approaches exist, including air stripping, steam stripping, and membrane, to name a few. Membrane is still experimental and in need of development while air/steam have considerable, practical history within multiple industries.

Primary Benefits

  • Recovery of gaseous ammonia-N from manure for reuse as a commercial fertilizer replacement (gaseous ammonia-N is typically combined with an acid such as sulfuric to create a liquid ammonium sulfate product).

Secondary Benefits

  • Odorous emissions from long-term storages are reduced since a portion of the ammonia is removed prior to storage and emitted ammonia is an offensive emission.
  • Recovery and reuse of ammonia-N can reduce GHG emissions when process is driven by renewable electrical and heat energy (as compared to conventional nitrogen fertilizer production).

How it Works

  • Ammonia stripping is usually operated as a continuous flow but can be operated in batch-mode.
  • Solid-free (or nearly solid-free) influent is pumped to a reactor vessel—usually a chemical stripping tower containing plastic media to increase surface area and reaction, although complete-mix and/or plug-flow basin versions also exist.
  • Various levels of chemical (a caustic or lime to raise pH), heat (to raise temperature), and/or pre-treatment stripping (to remove carbon dioxide and raise pH) are used to move the aqueous ammonia/gaseous ammonia equilibrium within the liquid manure towards greater gaseous form.
  • Air/steam introduced into the vessel is used to strip and transport stripped ammonia-N to a recovery vessel.
  • Stripped ammonia-N is recovered in a separate vessel – sulfuric acid or nitric acid is usually used during this process.
  • End-product is usually either liquid ammonium sulfate or ammonium nitrate.
  • Long-term liquid storage is required until appropriate time for land application.
  • Liquid ammonium sulfate can be dried to crystal form.

Pre-treatment and/or Post-treatment Required

  • Primary and secondary solid-liquid separation of manure is required to remove suspended solids, especially if a packed-tower is utilized.
  • Sand-manure separation is required for influents sourced from sand-bedded stalls.
  • Liquid effluent from ammonia stripping can be stored long-term or further processed if significant levels of dissolved phosphorous are present after pre-treatment to remove suspended solids.


  • Primary limitations are relatively low amounts of ammonia-N in raw dairy manure, capital and operating cost, storage requirements for recovered ammonia-N product, and lack of agronomic test plots to substantiate benefit to field crops.
  • Total manure N recovery rates are estimated to be between 33 and 66% with higher in the range recovery possible with pre-treatment by anaerobic digestion.

Other Considerations

  • Under the current economic conditions, partnership with poultry operations provide the best opportunity for a successful system due to the comparatively high ammonia-N concentrations.
  • Ammonia stripping has no effects on phosphorus or potassium as well as liquid storage volume.

Alitalo, A., Kyrö, A., & Aura, E. (2012). Ammonia stripping of biologically treated liquid manure. Journal of environmental quality, 41(1), 273-280.


Bonmatı, A., & Flotats, X. (2003). Air stripping of ammonia from pig slurry: characterization and feasibility as a pre-or post-treatment to mesophilic anaerobic digestion. Waste management, 23(3), 261-272.


Drosg, B., W. Fuchs, T. Al Seadi, M. Madsen, B. Linke. 2015. Nutrient recovery by biogas digestate processing, IEA Bioenergy, Implementing Agreement for a Programme of Research, Development and Demonstration on Bioenergy, ISBN 978-910154-16-8.


He, Q., Tu, T., Yan, S., Yang, X., Duke, M., Zhang, Y., & Zhao, S. (2018). Relating water vapor transfer to ammonia recovery from biogas slurry by vacuum membrane distillation. Separation and Purification Technology, 191, 182-191.


Frear, C., Ma, J., Yorgey, G., (2018). Approaches to nutrient recovery from digested dairy manure. Washington State University Extension, Pullman WA. EM112E.


Jiang, A., Zhang, T., Zhao, Q. B., Li, X., Chen, S., & Frear, C. S. (2014). Evaluation of an integrated ammonia stripping, recovery, and biogas scrubbing system for use with anaerobically digested dairy manure. Biosystems engineering, 119, 117-126.


Ukwuani, A. T., & Tao, W. (2016). Developing a vacuum thermal stripping–acid absorption process for ammonia recovery from anaerobic digester effluent. Water research, 106, 108-115.


Vaneeckhaute, C., Lebuf, V., Michels, E., Belia, E., Vanrolleghem, P. A., Tack, F. M., & Meers, E. (2017). Nutrient recovery from digestate: systematic technology review and product classification. Waste and Biomass Valorization, 8(1), 21-40.


Wallace, J.M., J.S. Budaj, and S.I. Safferman. 2015. Integrating Anaerobic Digestion and Nutrient Separation: A Synergistic Partnership. Manuscript for Dairy Environmental Systems and Climate Adaptations Conference, Cornell University.


Zhao, Q. B., Ma, J., Zeb, I., Yu, L., Chen, S., Zheng, Y. M., & Frear, C. (2015). Ammonia recovery from anaerobic digester effluent through direct aeration. Chemical Engineering Journal, 279, 31-37.

Technology Providers in order of 9 - Point Scoring System