Effect of calcium hydroxide application to feedlot pen surface material on ammonia, odor, and greenhouse gas emissions

Abstract. Calcium hydroxide (lime) is used to reduce microorganisms and odors in human biosolids, animal and poultry manures, and abattoir wastes. In the cattle industry, lime has been used as a disinfectant and is spread on the pen surface to control infections such as diarrhea and foot rot. The increase in pH that results from lime addition may increase ammonia emissions thereby negatively impacting air quality. Changing the pH of feedlot surface material (FSM) may also alter microbial activities which produce odorous compounds and greenhouse gases. The objective of this study was to measure ammonia (NH₃), hydrogen sulfide (H₂S) and greenhouse gas (GHG) emissions from FSM containing 0, 2.5, 5, or 10% lime. Measurements were taken over a 12 day period in lab-scaled pans containing FSM. The pH of the FSM was higher when the 5 and 10% treatments were applied compared to the 0 and 2.5% treatments for the first four days. During this time, there was a linear increase in NH₃ emissions as the concentration of lime increased in the FSM (P < 0.01). Ammonia emissions were similar across all treatments after day 4. Hydrogen sulfide emissions were higher (P < 0.01) for FSM containing 0% lime compared to the other treatments at Day 1. By Day 4 the H₂S emission for the FSM containing 2.5 and 5% lime were greater when compared to the 10 and 0% lime treatments. Carbon dioxide and N₂O remained near atmospheric concentrations for all treatments except the 0% lime which increased dramatically after Day 4. This indicates suppressed microbial activities in the FSM receiving lime. Methane increased gradually over time for all treatments. Results of this study indicate a potential increase in NH₃ emissions and a decrease in H₂S and GHG immediately following lime application, but no long-term treatment effects were observed.