Evaluation of OFFSET (Odor Setback Model) Using Neighborhood Monitors

Abstract

A comparison between observed and predicted odor intensities at neighbor's living in thevicinity of various livestock farms in 5 different Minnesota counties was made to evaluate an odorsetback tool developed by the University of Minnesota. In 309 out of 570 reported odor events thefarms participating in the investigation were the probable odor sources. In 199 (64%) of these anodor less than intensity 2 was predicted but an odor intensity equal to 2 or above was reported. In 99cases (32%) the predicted and reported odor intensity was in agreement, being either higher than 2or below 2. Regarding all observations the observed odor intensity was significantly higher than thepredicted. Possible reasons for these mixed results are; variations in odor rating and sensitivity ofresident recorders, wind speed fluctuations, possible errors and fluctuations in odor emissions fromeach farm (only one emission measurements were made at each farm), topographic variationbetween sites since OFFSET assumes flat surfaces, and background emissions from other sourcesthat may have contributed to what resident recorders were smelling.