An Update on Litter Amendments and Ammonia Scrubbers for Reducing Ammonia Emissions and Phosphorus Runoff from Poultry Litter


The objectives of the litter amendment research were to determine why alum applications to poultry litter occasionally fail to reduce soluble phosphorus (P) and to determine if aluminum-, calcium- or iron- based nanoparticles would reduce soluble P in litter when applied alone or in combination with conventional litter treatments used for ammonia control, such as alum and/or sodium bisulfate.

The objective of the scrubber research was to design a scrubber that reduces ammonia, dust, and pathogens in the air inside of animal rearing facilities, like broiler houses, rather than the air being exhausted from the facilities. Currently scrubbers are “end of pipe” technology, which purify the exhaust air, so the only economic benefit is the capture of nitrogen, which is relatively inexpensive. Reducing the ammonia, dust, and pathogens in the air inside poultry houses should result in production benefits, such as those found with litter amendments (improved weight gains, better feed conversion, lower susceptibility to disease, and reduced propane use).

What Did We Do?

A series of laboratory studies were conducted with various litter amendments.  The first study was conducted using litter from a commercial broiler house that had been treated with sodium bisulfate ten times over a two year period.  Poultry litter (20 grams) was weighed out into 6 centrifuge tubes and half of the litter samples were treated with alum at a rate of 5% by weight.  The tubes were incubated in the dark for one week, then extracted with 200 ml deionized water for one hour, centrifuged for 15 minutes at 8,000 rpm, filtered through 0.45 um filter paper and analyzed for soluble reactive phosphorus (SRP) using the Murphy-Riley method on an autoanalyzer.

The next four lab studies used the same basic incubation studies, although the litter that was used came from a pen trial we had conducted where we knew the litter had never been treated with sodium bisulfate.  Eighty six different treatment combinations involving conventional ammonia control treatments, such as alum and sodium bisulfate with or without the addition of different types of nanoparticles were used.  The nanoparticles used in this study were: (1) Al-nano – an aluminum based nanoparticle, (2) Fe-nano – an iron based nanoparticle, (3) MNP – a nanoparticle made of both aluminum and iron, and (4) TPX – a calcium silicate based nanoparticle made by N-Clear, Inc.  The sodium bisulfate that was utilized is sold under the tradename PLT (Poultry Litter Treatment) by Jones-Hamilton, Inc.

We also redesigned the ARS Air Scrubber so that it is scrubbing the air inside poultry houses rather than the exhaust air.  The critical design feature to allow this was the use of fast sand filters to remove all particulates from the water and acid used to scrub dust and ammonia, respectively.

What Have We Learned?

We found that alum failed to lower soluble P in poultry litter when the litter had been treated with sodium bisulfate, probably due to the formation of sodium alunite [NaAl3(OH)6(SO4)2], a mineral often found in acid soils where sulfate applications have occurred. The formation of this mineral likely inactivates the Al with respect to P adsorption or precipitation reactions.

We also found that a Ca-based nanoparticle (TPX) was very effective in reducing soluble P in litter, either when applied in combination with alum or sodium bisulfate.  Surprisingly, when TPX was applied with sodium bisulfate at very low levels, the soluble P levels of sodium bisulfate-treated litter decreased from 3,410 mg P/kg (when added alone) to 1,220, 541, and 233 mg P/kg litter, respectively, when 0.25, 0.5, and 1% TPX was added with sodium bisulfate.

Future Plans

We are currently conducting a large pen trial to determine the effect of TPX nanoparticles applied with alum or sodium bisulfate on ammonia emissions, soluble P, and P runoff from small plots using rainfall simulators.

We are also building a full-scale prototype of the indoor ammonia scrubber so that we can begin to test the efficacy of this scrubber.


Philip A. Moore, Jr., Soil Scientist, USDA/ARS, Fayetteville, AR


Additional Information

Moore, P.A., Jr. 2021. Composition and method for reducing ammonia and soluble phosphorus in runoff and leaching from animal manure. U.S. Patent Application No. 17/171,204. Patent pending.

Moore, P.A., Jr. 2022. A system for removing ammonia, dust and pathogens from air within an animal rearing/sheltering facility. U.S. Patent Application No. 17/715,666.  Patent pending.


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