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

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.

Limitations

  • 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.

Technology Providers in order of 9-Point Scoring System

The Nutritec® is a unique technology to recover nitrogen and phosphorus from wastewater by struvite precipitation followed by membrane ammonia stripping resulting in ammonium sulfate. The Nutritec technology can be used to recover nutrients from reject water, concentrated industrial wastewater, or even separately collected urine. Phosphate is recovered via struvite precipitation…
An award winning solution to recover ammonia from digestate or substrates from digestion. Instead of biological oxidation the recovered ammonia is turned into a bio-based fertilizer turning waste into value. The Nijhuis mission with this next level of ammonia recovery is ‘doing more with less’. The NAR has a proven…
Organics USA provides advanced process technology to control emissions from contaminating sources such as biogas from landfill sites or anaerobic digestion plants or to generate renewable energy. Their technology has been proven under the most exacting conditions, ensuring that clients will not only meet their environmental obligations but also protect…
The challenges and regulations in today’s tough marketplace require producers to be more efficient, more productive and more profitable. The McLanahan Nutrient Separation System allows dairies to do more with their valued manure stream. For more on how this tested and proven technology can economically benefit your operation, contact McLanahan…
GNS uses a modified stripping process, wherein the ammonium nitrogen is removed from digestates by using only exhaust heat from the CHP without the use of bases, acids or external stripping media. Binding of ammonia preferred with FGD gypsum to produce a concentrated ammonium sulfate solution and solid calcium carbonate…
Stripping (also called distillation) allows the separation of a solvent. This technology is often used to complement an evaporation unit for separating a solvent of produced condensates. The most common applications being the separation of ammonia or alcohol, to improve on the quality of condensates.
ECOCHIMICA’s stripping tower is used to reduce the volatile compound concentration (ammonia for example) in a fluid (waste water and process water). In the ecochimica stripping tower the fluid to be treated is pushed at the top of the tower and sprinkled downwards by spray-nozzle through special filling packs, which…