Treating Liquid Swine and Dairy Manure with Aluminum Chloride
Liquid aluminum chloride is added to liquid swine or dairy manure to reduce soluble phosphorus.
Liquid manures, such as liquid swine or dairy manure, contain relatively high concentrations of soluble phosphorus. Research has shown that phosphorus runoff and leaching from manure is correlated to the soluble phosphorus content of manure. Aluminum chloride can be added to liquid swine or dairy manure to reduce soluble phosphorus, resulting in less phosphorus runoff and leaching. Liquid manure may be treated in the pits inside swine production facilities or in retention ponds, holding ponds and/or lagoons on swine or dairy farms. In addition to reducing phosphorus runoff, aluminum chloride additions reduce ammonia volatilization from liquid manure, which improves air quality. It also facilitates flocculation to help remove solids from liquid manure.
How Does This Practice Work?
Aluminum chloride additions to liquid manure reduce non-point source phosphorus pollution by reducing soluble phosphorus via precipitation of aluminum phosphate and/or adsorption of phosphorus onto aluminum hydroxide. Once phosphorus is bound with aluminum it is less mobile, hence, phosphorus runoff and leaching are greatly reduced. Aluminum chloride can be applied to liquid manure in almost any location from inside production facilities to holding ponds or even in liquid manure spreaders immediately prior to land application. Reducing phosphorus runoff and leaching improves water quality by decreasing eutrophication, since phosphorus is normally the limiting nutrient for primary productivity, at least in freshwater systems. Reducing soluble phosphorus also reduces struvite mineral formation, which can cause clogging of pipes in liquid manure systems.
Aluminum chloride additions also reduce ammonia emissions from manure by lowering the pH of the manure, which shifts the ammonia/ammonium equilibria towards ammonium, which is not volatile. When utilized inside production facilities, such as treating pits in swine houses, lower atmospheric ammonia levels can result in improved animal performance such as better weight gains, feed conversion and reduced susceptibility to diseases, particularly airborne viral diseases. Improved air quality in animal rearing facilities is also beneficial to the health of agricultural workers.
Where This Practice Applies and Its Limitations
This practice applies to all swine and dairy operations that utilize liquid manure systems. To do this the producer should first take a representative sample of the manure and have it analyzed for total phosphorus. Then the mass of phosphorus should be calculated using the volume of manure to be treated, along with the phosphorus concentration. Aluminum chloride is then added in sufficient quantities to roughly make a 1:1 mole ratio of aluminum to phosphorus. Since the atomic weights of aluminum and phosphorus are similar producers can simply calculate the total pounds of phosphorus to be treated and add that much aluminum as aluminum chloride.
Aluminum chloride is acidic; hence, care should be taken to avoid applying it onto metal equipment or concrete to avoid corrosion. Adding aluminum chloride to liquid manures may sometimes cause the formation of foam. The foam is not a problem; in fact the foam helps reduce ammonia emissions by creating a physical barrier to volatilization.
It should be noted that sulfate containing compounds such as aluminum sulfate (alum), ferric sulfate, ferrous sulfate, calcium sulfate, sodium bisulfate, or sulfuric acid should never be added to liquid manures because of the potential formation of hydrogen sulfide (H2S) gas. Under anaerobic conditions bacteria in liquid manures can use sulfate as an electron acceptor for respiration, converting it to hydrogen sulfide gas, which could possibly cause harm or even death to agricultural workers.
Treating liquid swine or dairy manure with aluminum chloride is one of the most effective management practices for reducing phosphorus runoff and leaching.
Cost of Implementing the Practice
In 2023 liquid aluminum chloride (27.7% AlCl3 or 5.6% Al) costs $420 per ton or $0.21 per pound (without freight). This is equivalent to $3.75 per pound of aluminum. So, for example if 1,000 gallons of liquid swine manure contained a total of 4 pounds of phosphorus were being treated it would take about 4 pounds of aluminum or $15 worth of aluminum chloride. A delivery system including an acid-resistant pump, PVC pipe, and plumbing would cost an additional $1,000 – 2,000.
Operation and Maintenance
Aluminum chloride can be added to flush water, applied directly to holding ponds and lagoons or added directly to manure prior to land application.
DeLaune, P.B., P.A. Moore, Jr. and S. Formica. 2010. Reducing phosphorus in swine effluent with aluminum chloride treatment during lagoon cleanout. Applied Eng. Agr. 26:867-871.
Moore, P.A. Jr. 1999. Swine rearing facility and method for reducing ammonia and odors therein. U.S. Patent 5,890,454. Issued April 6, 1999.
Moore, P.A., Jr. 2002. Methods of treating animal waste slurries. U.S. Patent 6,346,240. Issued Feb. 12, 2002.
Moore, P.A., Jr. 2006. Methods of treating manure. U.S. Patent 7,011,824. Issued March 14, 2006.
Smith, D.R., P.A. Moore, Jr., C.V. Maxwell, B.E. Haggard and T.C. Daniel. 2003. Reducing phosphorus runoff from swine manure with dietary phytase and aluminum chloride. J. Environ. Qual. 33:1048-1054.
Smith, D.R., P.A. Moore, Jr., B.E. Haggard, C.V. Maxwell, T.C. Daniel, K. Van Devender and M.E. Davis. 2003. Impact of aluminum chloride and dietary phytase on relative ammonia losses from swine manure. J. Anim. Sci. 82:605-611.
Smith, D.R., P.A. Moore, Jr., C.L. Griffis, T.C. Daniel, D.R. Edwards and D.L. Boothe. 2001. Effects of alum and aluminum chloride on phosphorus runoff from swine manure. J. Environ. Quality. 30:992-998.
Timby, G.G., T.C. Daniel, R.W. McNew and P.A. Moore, Jr. 2004. Polymer type and aluminum chloride affect screened solids and phosphorus removal from liquid dairy manure. Applied Engineering in Agriculture 20:57-64.
For Further Information
Contact your local soil and water conservation district, USDA-NRCS or Cooperative Extension Service office. To find your local USDA Service Center, visit https://www.nrcs.usda.gov/contact/find-a-service-center.
|Philip A. Moore, Jr.
Editing and Design
NC State University
University of Tennessee
Moore, P.A., Jr. 2023. Treating Liquid Swine and Dairy Manure with Aluminum Chloride. SERA17 Phosphorus Conservation Practices Fact Sheets. https://sera17.wordpress.ncsu.edu/treating-liquid-swine-and-dairy-manure-with-aluminum-chloride/