Evaluation of Aluminum Sulfate (Alum) As a Feedlot Surface Amendment to Reduce Ammonia, Hydrogen Sulfide, and Greenhouse Gas Emissions from Beef Feedlots

Ammonia (NH₃) and greenhouse gas (GHG) emissions from concentrated feeding operations are a concern. The poultry industry has successfully used aluminum sulfate (Alum) as a litter amendment to reduce NH₃ emissions from poultry barns. Alum has not been evaluated for similar uses on cattle feedlot surfaces. The objective of this study was to measure NH₃, GHG, and hydrogen sulfide (H₂S) emissions from feedlot surface material (FSM) containing 0, 2.5, 5, or 10% Alum over a 32-d period in lab-scale pans containing FSM. Pans containing FSM were sampled every other day for the first 2 wk, and twice weekly thereafter. Results were analyzed as repeated measures using the MIXED procedure of SAS. Average pH of the FSM was significantly lower (P < 0.01) when 2.5, 5, and 10% Alum was included (5.3, 4.4, and 4.2, respectively) compared to 0% Alum (8.1). After 5 d, the pH of FSM containing 2.5% Alum (4.1) was higher (P < 0.01) than FSM with 5 and 10% Alum (3.8 and 3.5, respectively). Ammonia emissions were immediately reduced from FSM that received Alum, with no NH₃ volatilization occurring below pH 6.5. Overall NH₃, carbon dioxide and nitrous oxide levels were lower (P < 0.01) from FSM containing Alum than those without, with the 10% Alum providing the greatest reduction in emissions. Hydrogen sulfide emissions were higher (P > 0.01) at 0 and 10% inclusion (67 and 104 ppb, respectively) compared to 2.5 and 5% inclusions (56 and 62 ppb, respectively). Total nitrogen content of FSM did not differ among treatments (P < 0.10), but ammonium-nitrogen was highest (P < 0.01) when 10% Alum was used (2.58 g kg^-1). Application of Alum to FSM will reduce NH₃ and GHG emissions, but H₂S emission will increase at the 10% inclusion. Therefore, 5% Alum inclusion appears the most beneficial to reducing NH₃ and GHG emissions from cattle feedlots. USDA is an equal opportunity provider and employer.