Evaluating Draft EPA Swine Emission Models – Part I: Facilities

Highlights Draft EPA emission models for swine facilities were systematically evaluated. Draft EPA models performed poorly on estimating pollutant emissions when input variables were outside of NAEMS data. An unanticipated sensitivity of the draft EPA model outputs to pig inventory and climate was identified. Draft EPA models may need further revision and improvement before being adopted by the swine industry. ABSTRACT. In August 2021, the United States (U.S.) Environmental Protection Agency (EPA) released draft models to estimate daily NH 3 , H 2 S, PM 10 , PM 2.5 , and TSP emissions from breeding/gestation, farrowing, and grow-finish swine facilities (open-source swine manure storages are evaluated in Part II of this series) using inputs of daily mean ambient temperature, relative humidity (RH), cycle day (only farrowing), and live animal weight (animal inventory multiplied by animal body weight). For breeding/gestation and grow-finish facilities, unique models for NH 3 and H 2 S emissions were created based on manure storage classifications of deep-pit, shallow-pit, and no differentiation between deep- and shallow-pits. These models were developed from refined datasets generated by the National Air Emissions Monitoring Study fieldwork completed in 2009 and notably do not include nurseries, wean-finish facilities, gilt development units, and boar studs. This study evaluated the robustness of the EPA draft models by using a “one-factor-at-a-time” sensitivity analysis and an assessment of annual emission estimates using inputs reflective of current U.S. swine housing practices and ambient conditions of representative locations in the U.S. Results revealed that draft EPA model outputs exhibit erratic trends as input factors are changed with others held constant; namely, the influence of animal inventory and animal weight tends to cause drastic changes in draft model emission outputs. The calculation of annual emissions showed insensitivity to ambient conditions and varying levels of agreement with previously published studies. These current draft emission models cannot be used to accurately characterize the wide range of swine facilities where management and climate conditions across regions vary considerably. Revisions are suggested to accommodate a greater range of swine facility types, inventories for practical emission estimations, and climate zones. While these models may provide some insight into estimating emissions, they may not fully encapsulate the complexity and variability of emissions from swine facilities. Keywords: Air quality, Ammonia, Buildings, Hydrogen sulfide, Models, Particulate matter, Pigs.