Emission of ammonia, hydrogen sulfide, and greenhouse gases following application of aluminum sulfate to beef feedlot surfaces

Authors: Spiehs, Mindy; Woodbury, Bryan

Submitted to: Waste to Worth Conference
Publication Type: Proceedings
Publication Acceptance Date: 3/29/2022
Publication Date: 4/21/2022
Citation: Spiehs, M.J., Woodbury, B.L. 2022. Emission of ammonia, hydrogen sulfide, and greenhouse gases following application of aluminum sulfate to beef feedlot surfaces. In: Proceedings of Waste to Worth Conference, April 18-22, 2022, Oregon, Ohio.

Interpretive Summary: Ammonia and hydrogen sulfide are compounds that are emitted from cattle feedlot operations that not only produce unpleasant odors, but they can be harmful to humans and animal. Carbon dioxide, nitrous oxide, and methane are gases that are associated with global warming, and livestock producers are under increased scrutiny to reduce these emissions from their operation. One way livestock producers can reduce these emissions is to apply products to the feedlot surface that can prevent the release of these gases into the air. Aluminum sulfate, also known as alum, is one such product. The poultry industry has successfully used alum for almost 20 years to reduce ammonia emission. Alum works by lowering the pH of the poultry litter which traps the nitrogen in the litter and keeps it from escaping into the air. This study was designed to see if alum could also work on beef cattle feedlot surfaces to reduce ammonia, hydrogen sulfide, carbon dioxide, nitrous oxide, and methane emission from the surface of beef feedlot pens following application of alum. Four pens (30 cattle/pen) had alum applied and four did not receive alum. Air samples were analyzed at day -1, 0, 5, 7, 12, 14, 19, 21, and 26; pH was measured at each sampling location. The pens treated with alum had a lower pH on the pen surface which reduced ammonia emissions for the first 5 days, the treatment was not successful in sustaining lower ammonia emission. Hydrogen sulfide and methane emissions were increased when alum was used on the feedlot surface. Aluminum sulfate contains sulfur which bacteria in the feedlot surface material convert to sulfide compounds that are released into the air. Therefore, it does not appear that alum will be a suitable amendment to use on cattle feedlot surfaces to reduce emissions.

Technical Abstract: Preliminary lab studies have indicated that 5-10% (g/g) aluminum sulfate (alum) lowers NH3 from feedlot surface material (FSM). The objective of this study was to determine the emission of NH3, hydrogen sulfide (H2S), carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4) from the surface of beef feedlot pens following application of 10% alum (g/g). Four pens (30 cattle/pen) had alum applied and four did not receive alum. Air samples were analyzed at day -1, 0, 5, 7, 12, 14, 19, 21, and 26; pH was measured at each sampling location. Addition of alum lowered pH of pen surface material 8.3 to 4.7 (p < 0.01) and the pH remained lower in alum-treated pens for 26 days (p < 0.01). Although the pH remained low, NH3 flux was only lower (p < 0.01) at day 0 and day 5 for alum-treated pens compared to the pens with no alum treatment. Nitrous oxide emission was not affected by alum treatment (6.2 vs 5.7 mg m-2 min-1, respectively for 0 and 10% alum treated pens). Carbon dioxide emission was lower for alum-treated pens than non-treated pens from day 5 until the end of the study (p < 0.05), perhaps due to suppressed microbial activity from the lower pH. Hydrogen sulfide emission was higher (p < 0.05) from alum-treated feedlot surface material (0.8 mg m-2 min-1) compared to non-treated feedlot surface material (0.3 mg m-2 min-1), likely due to addition of sulfate with alum. Methane emission was also higher in alum-treated pens (173.6 mg m-2 min-1) than non-treated pens (81.4 mg m-2 min-1). The limited reduction in NH3, along with increased H2S and CH4 emission from the FSM indicates that alum is not a suitable amendment to reduce emissions from beef feedlot surfaces.