Dispersion modeling for prediction of emission factors for cattle feedyards

Abstract

Upon implementation of the Federal Clean Air Act and with the anticipated increase in resources of state air pollution regulatory agencies, regulation of air quality will expand to agricultural production and processing industries. This expansion of state air pollution regulatory agencies will require accurate EPA AP-42 emission factors. A protocol was developed so that accurate emission factors can be determined using both source sampling data and dispersion modeling. In this study, an emission factor was developed, using measured and predicted concentrations, for cattle feedyards. An emission factor of 10 pounds per 1000 head per day was recommended for the cattle feeding industry. This emission factor agreed with the average and seasonally weighted emission factor of 9.2 and 10.2 pounds per 1000 head per day, respectively. This was much lower than the current EPA AP-42 emission factor of 280 pounds per 1000 head per day. An emission factor of 10 pounds per 1000 head per day was used when developing isoplanes to illustrate the particulate matter with an aerodynamic diameter less than under ten microns (PMIO) and total suspended particulate (TSP) concentrations. The isoplanes were developed for 10,000, 20,000, and 40,000 head feedyards in the Amarillo, Lubbock, San Angelo, and Brownsville area. These isoplanes can provide guidance to the cattle feeding industry when siting feedyards with respect to the predicted downwind particulate concentrations and the property line.