A method for determination of pollutant emissions from naturally ventilated freestall dairy barns

In mechanically-ventilated freestall dairy barns, pollutant emissions can accurately be determined from the differences in concentrations between the influent and exhaust gases and the measured flow of the ventilating air. In contrast, emissions from naturally ventilated (NV) freestall dairy barns do not have well defined specific air entry or exit points. In addition, pertinent airflow characteristics (velocity and direction) vary continuously, both temporally and spatially. This scenario significantly complicates the determinations of emissions. This paper examines a method being developed and tested for determining emissions from NV livestock barns. The method essentially entails placement of sonic anemometers (to measure air movement in and out of the structure) at salient points all around the barn in order to determine the airflow characteristics. Air samples are simultaneously collected at these selected points to determine the respective representative concentrations of the air entering or leaving the barn over a given sampling cycle or time. The airflow data is subsequently coupled with pollutant concentrations data to determine respective emissions from the barn. Results indicate credibility of sonic anemometers in the determination of ventilation characteristics in naturally ventilated bams, which are critical to accurate determination of pollutant emissions calculations from such barns.