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United States Department of Agriculture

Agricultural Research Service

Title: Effect of Adding Alum and Zeolite to Dairy Slurry on Ammonia Volatilizationand Chemical Composition

Authors
item Lefcourt, Alan
item Meisinger, John

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 31, 2001
Publication Date: N/A

Interpretive Summary: Development of cost effective amendments for treating dairy slurry has become a critical problem as the number of cows on farms continues to grow and the acerage available for manure spreading continues to shrink. This study determined the optimal rates of adding either alum or zeolite to dairy slurry to reduce ammonia missions and to bind phosphorous so that it is less of a problem when the manure is spread. Four rates of adding amendments were tested: 0.4, 1.0, 2.5, and 6.25% by weight. Cumulative ammonia losses were measured over 96 hours,and manure samples from the start and end of trials were analyzed for total nitrogen and phosphorus, and were extracted with 0.01M CaCl2, 1.0M KCl, and water. To test the chemical properties of the amendments, the extracts were analyzed for ammonium nitrogen, phosphorous, aluminum, and pH. The addition of 6.25% zeolite or 2.5% alum to dairy slurry reduced ammonia emissions by about 50%. Alum treatment retained ammonia by reducing the slurry pH to 5 or less. In contrast, zeolite adsorbed ammonium thereby reducing dissolved ammonia gas. In addition, alum essentially eliminated soluble phosphorous. Zeolite also reduced soluble phosphorous by over half, but the mechanism for this reduction is unclear. Alum must be carefully added to slurry to avoid effervescence and excess additions which can increase soluble aluminum in the slurry. In conclusion, the use of alum or zeolites as an on-farm amendment to dairy slurry offers the potential for significantly cutting ammonia emissions and for reducing problems with phosphorus.

Technical Abstract: Development of cost effective amendments for treating dairy slurry has become a critical problem as the number of cows on farms continues to grow and the acerage available for manure spreading continues to shrink. To determine the effectiveness and optimal rates of addition of either alum or zeolite to dairy slurry, ammonia emissions and the resulting chemical changes in the slurry were measured in response to addition of amendments at 0.4, 1.0, 2.5, and 6.25% by weight. Ammonia volatilization over 96 hours was measured using six small wind tunnels with gas scrubbing bottles at the inlets and outlets. Manure samples from the start and end of trials were analyzed for total nitrogen and phosphorus, and were extracted with 0.01M CaCl2, 1.0M KCl, and water with the extracts analyzed for ammonium nitrogen, phosphorous, aluminum, and pH. The addition of 6.25% zeolite or 2.5% alum to dairy slurry reduced ammonia emissions by nearly 50% and nearly 60%, respectively. Alum treatment retained ammonia by reducing the slurry pH to 5 or less. In contrast, zeolite, being a cation exchange medium, adsorbed ammonium and reduced dissolved ammonia gas. In addition, alum essentially eliminated soluble phosphorous. Zeolite also reduced soluble phosphorous by over half, but the mechanism for this reduction is unclear. Alum must be carefully added to slurry to avoid effervescence and excess additions which can increase soluble aluminum in the slurry. The use of alum or zeolites as an on-farm amendment to dairy slurry offers the potential for reducing ammonia emissions and soluble phosphorus in dairy slurry.

Last Modified: 9/21/2014
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