Evaluation of Air Dispersion Models for Livestock Odour Application

Instantaneous downwind malodours from two swine farrowing facilities were assessed in the field by 15 trained human sniffers. A total of 34 1-hour field monitoring sessions were carried out on the two farms between June and October in 2003 and 2004. Odour emissions from the farm were measured and weather conditions were monitored simultaneously. Four air dispersion models, ISCST3, AUSPLUME, IN-PUFF 2, and WindTrax were applied to simulate odour dispersion around the two farms by using on-site measured source emission rates and meteorological data. Correlation between odour concentration and 8-point odour intensity for swine odour was developed to convert model simulated downwind odour concentration into odour intensity so that model predictions could be evaluated against field measurements. The comparison between model predictions and field measured data indicated that in general, all four models predicted downwind odour well at distances of 500 m and 1000 m. In particular, the agreement between model predictions and field measurements was almost 100% at 1000 m for all four models. However, at downwind distance of 100m, all models predicted field odour with relatively low agreement. Since long-distance (>1000 m) predictions are of more practical value, all models are considered to be adequate in predicting odours downwind from swine operations.