Reduction of Odor and VOC Emissions from a Dairy Lagoon

Abstract

Odor is a concern at many large animal feeding operations. Due to complaints from downwind neighbors, a project was initiated to reduce emissions of odor and volatile organic compounds (VOCs) from a 3000-cow dairy. An initial odor evaluation showed that the volatile solids loading rate to the lagoons was 15 times that recommended by ASABE standards, and that the primary source of the odor problem was the two lagoons. Abatement measures included covering the treatment lagoon, adding additional aeration capacity to the storage lagoon, and reducing the volatile solids loading rate to both lagoons. Odor, hydrogen sulfide, and water quality were monitored initially and at the completion of the project. A laboratory-based wind tunnel and gas chromatographic method was developed to evaluate reduction in VOC emissions of phenol,4-ethylphenol, p-cresol, indole, skatole, and seven volatile fatty acids. Dramatic improvements in ambient air quality were observed after 30 months, with 80% reduction in ambient odor concentrations and 96% reduction in ambient H2S concentrations downwind of the lagoons. There was a 94.2% reduction in total odorous VOC emissions from the lagoons as measured under laboratory conditions with the small wind tunnel. Paralleled improvements in water quality were observed, with a 55.3% reduction in BOD5, 84.1% reduction in VFAs, and 76.3% increase in oxidation reduction potential (ORP). These results demonstrate the potential for air quality improvements with best management practices such as lagoon covers, aeration, and using innovative methods for reducing the volatile solids loading rate. Relative improvements are always site specific.