Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: February 1, 2009
Publication Date: June 19, 2009
Citation: Trabue, S.L., Maghirang, R., Mcconnell, L.L. 2009. Distant Odors: Identifying Key Odors Associated With Cattle Feedlots Downwind. In: Proceedings of Air & Waste Management Association's Annual Conference & Exhibition, Detroit, Michigan, June 16-19, 2009. Paper No. 113. Interpretive Summary: The National Research Council identified odors as the most significant animal emission at the local level and noted that methods to quantify odor needed to be developed and standardized. In this study, we tested two different methods to quantify key odorants associated with animal production. The first method assigned a compound significance to odor by the ratio of that compound’s measured concentration in air to its odor threshold value known as the odor activity value (OAV). Compounds with the highest OAV were considered the most odorous at a particular site. The second method used a technique developed by the food and fragrance industries to identify key aromas; gas chromatography-olfactometer (GC-O). This technique ranks the importance of a compound based on its frequency of detection among human panelists. Compounds detected by the most panelists are considered key components of the overall odor. In this study, air samples were collected directly from a cattle feedlot, 0.25 miles downwind, and over 2 miles downwind from a facility. Key odorants detected at the feedlot included sulfide compounds, oxazoles, volatile fatty acids, phenolic compounds, and indole compounds. Key odorants detected 0.25 miles away included sulfides, oxazoles, butanoic acid, 4-methylphenol, and indole compounds. Samples collected over 2 miles away were associated mainly with indole compounds and some with 4-methylphenol. Indole had the highest OAV for compounds detected over 2 miles away and it also had the highest frequency of detection in GC-O analysis. The two methods complemented each other, with the GC-O method being more sensitive. Research results described in this report provide air quality and animal scientists, growers, engineers, and regulatory officials valuable information on the development and adoption of new odor quantification techniques.
Technical Abstract: The National Research Council identified odors as the most significant animal emission at the local level and has highlighted the need for the development of standardized protocols for sampling and analysis of odors. To date, however, little progress has been made on identifying sampling and analysis techniques. Identifying key odorants using both analytical (odor activity values) and GC-O (olfactometry) are promising techniques that have wide acceptance in both the food and fragrance industries. Air samples for both GC-O and GC-MSD (mass spectrometry thermal desorption) analysis were collected on sorbent tubes containing graphitized carbon sorbent material. Samples were collected directly from a cattle feedlot in central Kansas, 0.25 miles away, and over 2 miles away. Sorbent tubes were analyzed by GC-MS-O (mass spec olfactometry) and key odorants determined using both GC-SNIFF (technique within GC-O) and OAV (odor activity value). Key odorants detected at the source included sulfide compounds, oxazoles, volatile fatty acids, phenolic compounds, and indole compounds. Key odorants 0.25 miles away included sulfides, oxazoles, butanoic acid, 4-methylphenol, and indole/3-methylindole, while samples collected over 2 miles away were associated with indole/3-methylindole and 4-methylphenol. No compound was detected above their odor threshold value for samples collected further than 0.25 miles away, which suggest that there may be some synergistic effects of odor combinations. Indole had the highest OAV for compounds detected over 2 miles away.