ARS | Publication request: Identifying key odorants from animal feeding operations

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: November 1, 2009
Publication Date: N/A

Interpretive Summary: Odor emissions from animal agriculutre negatively impact air qualitly in surrounding communities. Current methods used to measure or describe odor from animal agriculutre underestimate it due to the properties of the odorants and the sampling containers used to store the odor. Two relatively new odor monitoring techniques were used in this study for assesing the movement of odor from the source to surrounding areas. Both techniques used gas chromatography (GC) to measure odorous compounds with one combining the response of human nose with the GC response called GC-O (olfactomerty). GC-O technique was able to detect compounds that a strictly analytical approach could not. It was also discovered that currently published odor threshold values for many odor-causing compounds need to be revised since many of the compounds quantified using GC-O were present at concentrations of less than one tenth of the published value, yet they still had odorous properties. The GC-O technique and the resultant information is important for scientists and engineers because it will help them determine the specific compounds that are most responsible for odor and enable them to target those specific compounds for odor mitagtion designs.

Technical Abstract: Odor emissions from animal agriculutre negatively impact air qualitly in surrounding communities. Current analytical practices are biased against agriculutral odorants and thus inadequate for odor quantification. The purpose of this study was to evaluate two different techniques ability to identify key odorants. The first technique ranks odorants by its odor activity value (OAV, ratio of an odorous compounds concentration in air to its odor threshold level). The second technique, GC-O (olfactometry), ranks odorants based on response of human panelists. Air samples were collected on sorbent tubes at the source site (cattle feedlot and swine facility) and downwind loactions (250 m and 3 km). Sorbent tubes were thermally desorbed for both GC-MSD and GC-O analysis. Eight non-trained panelist were used in GC-O analysis with an average age of 34 years. At the source several compounds characterized as volatile fatty acids, phenols, and indoles had OAV greater than 1.0, but none of the compound classes had OAV above 1.0 at the 250 m or 3 km sites. Key odorants detected by GC-O at the sources included sulfides, oxazoles, volatile fatty acids, phenols, and indole compounds, while further downwind odors were mainly assoicated with indole compounds and some phenol compounds. GC-O was a more sensitive technique for determining odorous compounds than OAV. It was also discovered that currently published odor threshold values for many odor-causing compounds need to be revised since many of the compounds quantified using GC-O were present at concentrations of less than one tenth of the published value, yet they still had odorous properties. This information will help scientists and engineers determine the specific compounds that are most responsible for odor and enable them to target those specific compounds for odor mitagtion designs.