Ammonia emissions from cattle feedlots pose the potential to react with other compounds such as oxides of nitrogen and sulfur, which lead to detrimental environmental effects. Ambient ammonia (NH 3) concentrations were measured continuously at a beef cattle feedyard for 12 months beginning in March 2007. Concentrations were measured every 5 min, 24 hours per day, at a sample intake height of 3.3 m using a chemiluminescence analyzer. On-site weather data were collected concurrently. Modeled emissions of NH 3 were compared with the mass balance of N for the feedyard. Mean annual NH 3 concentrations were 0.57 ppm, with a monthly average low of 0.37 ppm in December 2007 and a monthly average high of 0.77 ppm in August 2007. Flux densities were calculated using a backward Lagrangian stochastic model (WindTrax 2.0.7.8). Mean annual flux density was 70.7 mg m-2 s-1 (2.2 kg m-2 year-1). Mean monthly flux density ranged from 42.7 to 123.1 mg m-2 s-1 (0.11 to 0.32 kg m-2 month-1) in November and April 2007, respectively. Both concentration and flux density had a diel distribution with minima during the nighttime hours and maxima during the early afternoon. On an annual basis, 48.8% of fed N was volatilized as NH 3. The inverse modeled daily ammonia production per head was 85.3 g NH 3-N (head fed)-1 d-1 .

There is a growing concern with air and odor emissions from agricultural facilities. A supplementary research project was conducted to complement the U.S. National Air Emissions Monitoring Study (NAEMS). The overall goal of the project was to establish odor and chemical emission factors for animal feeding operations. The study was conducted over a 17-month period at two freestall dairies, one swine sow farm, and one swine finisher facility. Samples from a representative exhaust airstream at each barn were collected in 10 L Tedlar bags and analyzed by trained human panelists using dynamic triangular forced-choice olfactometry. Samples were simultaneously analyzed for 20 odorous compounds (acetic acid, propanoic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, hexanoic acid, heptanoic acid, guaiacol, phenol, 4-methylphenol, 4-ethylphenol, 2-aminoacetophenone, indole, skatole, dimethyl disulfide, diethyl disulfide, dimethyl trisulfide, hydrogen sulfide, and ammonia). In this article, which is part 6 of a six-part series summarizing results of the project, we investigate the correlations between odor concentrations and odor activity value (OAV), defined as the concentration of a single compound divided by the odor threshold for that compound. The specific objectives were to determine which compounds contributed most to the overall odor emanating from swine and dairy buildings, and develop equations for predicting odor concentration based on compound OAVs. Single-compound odor thresholds (SCOT) were statistically summarized and analyzed, and OAVs were calculated for all compounds. Odor concentrations were regressed against OAV values using multivariate regression techniques. Both swine sites had four common compounds with the highest OAVs (ranked high to low: hydrogen sulfide, 4-methylphenol, butyric acid, isovaleric acid). The dairy sites had these same four compounds in common in the top five, and in addition diethyl disulfide was ranked second at one dairy site, while ammonia was ranked third at the other dairy site. Summed OAVs were not a good predictor of odor concentration (R2 = 0.16 to 0.52), underestimating actual odor concentrations by 2 to 3 times. Based on the OAV and regression analyses, we conclude that hydrogen sulfide, 4-methylphenol, isovaleric acid, ammonia, and diethyl disulfide are the most likely contributors to swine odor, while hydrogen sulfide, 4-methyl phenol, butyric acid, and isovaleric acid are the most likely contributors to dairy odors.

Livestock facilities have historically generated public concerns due to their emissions of odorous air and various chemical pollutants. Odor emission factors and identification of principal odorous chemicals are needed to better understand the problem. Applications of odor emission factors include inputs to odor setback models, while chemical emission factors may be compared with regulation thresholds as a means of demonstrating potential health impacts. A companion study of the National Air Emissions Monitoring Study (NAEMS) included measurements necessary for establishing odor and chemical emission factors for confined animal feeding operations. This additional investigation was conducted by the

The objective of this study was to measure the long-term odor emissions and corresponding concentrations and emissions of 20 odorous volatile organic compounds (VOCs). This study was an add-on study to the National Air Emission Monitoring Study (NAEMS). Odor and odorous gas measurements at four NAEMS sites, including dairy barns in Wisconsin (WI5B) and Indiana (IN5B), a swine finisher barn in Indiana (IN3B), and swine gestation and farrowing barns in Iowa (IA4B), were conducted from November 2007 to May 2009. The odorous gas samples were collected every two weeks using sorbent tubes (samples were collected twice each season of the year, with the exception of spring 2009 when samples were collected three times) and analyzed by gas chromatography-mass spectrometry-olfactometry (GC-MS-O). In this article, we summarize the measured gas concentrations and emissions of the 20 target VOCs from each of the four sites. The average total odorous VOC concentrations for the entire sampling period were 276, 96.9, 1413 and 394 μg dsm -3 for WI5B, IN5B, IN3B, and IA4B, respectively. For the swine sites, the highest seasonal average total odorous VOC concentrations for each barn were observed during spring (1890 μg dsm -3 for IN3B and 458 μg dsm -3 for IA4B). For the dairy sites, the highest seasonal average total odorous VOC concentrations were observed in winter at WI5B (446 μg dsm -3 ) and in summer at IN5B (129 μg dsm -3 ). The average total emission rates for the 20 odorous VOCs were 290 mg h -1 AU -1 (WI5B), 36.0 mg h -1 AU -1 (IN5B), 743 mg h -1 AU -1 (IN3B), 33.9 mg h -1 AU -1 (IA4B swine gestation barns), and 91.7 mg h -1 AU -1 (IA4B swine farrowing room). The average seasonal total odorous VOC emission rates were highest during summer at WI5B (805 mg h -1 AU -1 ), IN5B (121 mg h -1 AU -1 ), and IN3B (1250 mg h -1 AU -1 ) and during spring at IA4B (95.8 mg h -1 AU -1 ). The emissions of specific VOCs varied between seasons, sites, and species. To date, this is the most comprehensive VOC measurement survey of odorous compound emission rates from commercial livestock buildings. KeywordsAnimal feeding operations, Gas chromatography-mass spectrometry, Volatile organic compounds

Simultaneous chemical and sensory analyses using gas chromatography-mass spectrometry-olfactometry (GC-MS-O) for air samples collected at barn exhaust fans were used for quantification and ranking of the odor impacts of target odorous gases. Fifteen target odorous VOCs (odorants) were selected. Air samples were collected at dairy barns in Wisconsin and Indiana and at swine barns in Iowa and Indiana over a one-year period. The livestock facilities with these barns participated in the National Air Emissions Monitoring Study (NAEMS). Gas concentrations, odor character and intensity, hedonic tone, and odor peak area of the target odorants in air samples were measured simultaneously with GC-MS-O. The four individual odorants emitted from both dairy and swine sites with the largest odor impacts (measured as odor activity value, OAV) were 4-methyl phenol, butanoic acid, 3-methyl butanoic acid, and indole. The total odor (limited to target VOCs and referred to as the measured concentrations, odor intensities, and OAVs) emitted from the swine sites was generally greater than that from the dairy sites. The Weber-Fechner law was used to correlate measured odor intensities with chemical concentrations. Odorants with higher mean OAV followed the Weber-Fechner law much better than odorants with lower mean OAV. The correlations between odor intensities and chemical concentrations were much better for the swine sites (typically p < 0.05 and R 2 = 0.16 to 0.51) than for the dairy sites (typically p > 0.05 and R 2 < 0.15). Linking specific gases to odor could assist in the development and evaluation of odor mitigation technologies for solving livestock odor nuisance problems. KeywordsAir quality, Animal feeding operations, Gas chromatography, Mass spectrometry, Odor, Olfactometry, WeberFechner law Disciplines Agriculture | Bioresource and Agricultural Engineering CommentsThis article is from Transactions of the ASABE 58 (5)