Effect of using aluminum sulfate (alum) as a surface amendment in beef cattle feedlots on ammonia and sulfide emissions

Authors: Spiehs, Mindy; Woodbury, Bryan

Submitted to: Sustainability
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/7/2022
Publication Date: 2/10/2022
Citation: Spiehs, M.J., Woodbury, B.L. 2022. Effect of using aluminum sulfate (alum) as a surface amendment in beef cattle feedlots on ammonia and sulfide emissions. Sustainability. 14(4). Article 1984. https://doi.org/10.3390/su14041984.
DOI: https://doi.org/10.3390/su14041984

Interpretive Summary: Ammonia and sulfides are compounds that are emitted from cattle feedlot operations that not only produce unpleasant odors, but they can be harmful to humans and animal. 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; one such product is aluminum sulfate, also known as alum. Alum has been used in the poultry industry for almost 20 years and works by lowering the pH of the poultry litter which traps the nitrogen in the litter and keeps it from volatilizing into the air. This study was designed to see if alum could also work on beef cattle feedlot surfaces. Four studies were conducted. The first two were preliminary studies conducted in the laboratory to determine how much alum needed to be applied and how frequently it should be applied. Three concentrations of alum were tried including 2.5, 5, and 10% alum. All three lowered the pH of the feedlot surface material but only the 5 and 10% alum lowered ammonia emissions. Next, 5% alum was added to the feedlot surface material in one dose or 20% of the dose was added each week for 5 weeks to see if the reduction in ammonia emissions could be extended beyond 14 days. There was no advantage of adding the alum more frequently in smaller doses. The last two studies were conducted on the feedlot surface of a recently vacated cattle pen. In the first study 5% alum was added which was only able to successfully lower the ammonia emissions for 7 days compared to the untreated areas of the pen. The second study increased the dose to 10% alum, which could successfully lower the ammonia for 14 days compared to untreated areas of the pen. Sulfide emissions were also measured in each study and in each study sulfide emissions increased when alum was added to 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: The objective of this study was to measure NH3 from feedlot surface material (FSM) containing aluminum sulfate (alum). A 33-day lab-scale study was conducted using pans containing FSM and either 0, 2.5, 5, or 10% alum. The pH of the FSM was significantly lower (P < 0.01) when treated with 2.5, 5, and 10% alum as opposed to the 0% alum treatment. No NH3 volatilization occurred below a pH of 6.5. A second study determined that small, weekly doses of 5% alum did not lower NH3 emissions further than a single dose of 5% alum. Two studies on the feedlot surface demonstrated a significant decrease (P < 0.01) in pH in the areas of the pens where alum was added compared to those that did not receive alum. Ammonia concentrations were lower (P < 0.05) for the areas that received alum compared to those that did not receive alum for 7 days when 5% alum was applied and 14 when 10% alum was applied. In all the studies, sulfide emissions increased when alum was added to the FSM. We concluded that 5% or 10% alum may reduce NH3 emissions from beef feedlots temporarily, but higher sulfide emissions offset this benefit.