Developing an odor acceptability threshold for livestock facilities and the application of manure

Odor and gas emissions were sampled on 38 dairies and 15 feedlots in southern Idaho. Odor strength was measured using a "Nasal Ranger"(TM) Field Olfactometer and n-butanol to analyze for detection threshold and odor intensity, respectively, at the facilities' most probable odor sources 50 meters downwind and 200 meters downwind. Facility waste handling systems and management were found to have the greatest effect on odor emission versus facility size. Odors in excess of 15 Dilutions to Threshold (DT), using a "Nasal Ranger"(TM), were found to be objectionable when odor panelists were located at a rural residence during 50% of the odor measurements. Panelists observing the same level of odor would have found it objectionable nearly eighty percent (80%) of the time if the odor was detected during a party or event at a rural residence. This paper suggests that scientists, producers, policy makers, and rural residents consider various odor levels objectionable depending on land use conditions, or how rural citizens are enjoying their property. The combination of evaluating odor acceptability, given different land use conditions and dilutions to threshold, allows decision makers and scientists to discuss and manage odors on the basis of objective rather than subjective criteria.