Feasibility test and field application of biofoam spray to directly reduce ammonia emissions from a swine manure slurry pit

Abstract

Bad-odor gases emitted from swine manure slurry are a global concern because of their detrimental effects on human health and animal welfare. We sprayed odor-removing microbe-loaded surfactant foam (biofoam) directly on the manure slurry surface to suppress NH3 (major odor component in slurry) emissions. Two subsequent experiments were conducted: a feasibility test in a tank and a field manure slurry pit test. The biofoam was sprayed directly onto the slurry once per day. The biofoam sprayed once on the slurry was stable for 20–24 h on the slurry. In the feasibility test tank, 99%–100% NH3 emissions were suppressed for 72 h, and a 61%–89% reduction in NH3 emissions was obtained for 72 h from the field manure slurry pit. The biofoam successfully blocked NH3 emissions. The NH3 reduction efficiency of the biofoam was consistently related to its stability on the surface of the manure slurry. The long-lasting surfactant foam is a good physical suppression cover for reducing NH3 release into the environment. After 72 h, NH3 slowly began to be emitted; nevertheless, the emission was much lower than that of the control. The tiny bubbles that formed after the foam broke still acted as an odor-suppression barrier. Moreover, NH3-reducing microbes loaded onto the surfactant foam degraded NH3 from the manure slurry, and a 34%-63% reduction in NH3 emission was attributed to biological effects after the foam was broken. Overall, NH3 emissions were reduced directly by the biofoam surface covering the manure slurries, the formation of a thin encapsulation layer on the slurry surface, and the activity of spontaneously added microbes. The developed method is a promising odor-reducing technique for swine manure.