Odor Concentrations Downwind of Idaho Dairies and Heifer Facilities

Abstract

Odor and gas concentrations were sampled on 38 dairies and 15 heifer and calf raising facilities in southern Idaho. Odor detection threshold was measured using a Nasal Ranger field olfactometer, and odor intensity was measured using n-butanol. Gas concentrations for total reduced sulfur (hydrogen sulfide) were measured at each farm's most probable odor source, 50 m downwind, and 200 m downwind using a Jerome meter, and ammonia was measured using Drger diffusion tubes. The type and management of manure handling systems were found to have the greatest impact on odor concentration versus the number of animals on the facility. There were observations of individual facilities within each subject group that emitted odors much less and up to twice the group averages. Flushed freestall and scraped freestall systems were shown to have the greatest measured odor concentrations, while open-lot facilities had lower measured levels. Seasonal variations on each type of dairy studied were found to have a significant impact on odor and gas concentrations at the source. Odor concentrations from heifer facilities were found to be similar to those of open-lot dairies. Porous geotextile covers used on secondary manure separation basins were found to be effective in reducing odor concentrations by half. Odors that were in excess of 15 dilutions to threshold, using the Nasal Ranger, 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 80% of the time if the odor were detected during a party or event at a rural residence.