Sarah D. Bereznicki

Odor and Odorous Chemical Emissions from Animal Buildings: Part 6. Odor Activity Value

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.

Odor and Odorous Chemical Emissions from Animal Buildings: Part 4—Correlations Between Sensory and Chemical Measurements

This study supplemented the National Air Emissions Monitoring Study (NAEMS) with one year of comprehensive measurements of odor emission at five swine and four dairy buildings. The measurements included both standard human sensory measurements using dynamic forced-choice olfactometry and chemical analysis of the odorous compounds using gas chromatography-mass spectrometry. In this article, multilinear regressions between odor and gas concentrations (a total of 20 compounds including H2S, NH3, and VOCs) were investigated. Regressions between odor and gas emission rates were also tested. It was found that gas concentrations, rather than emission rates, should be used to develop multilinear regression models. For the dairy sites, H2S, NH3, acetic acid, propanoic acid, 2-methyl propanoic, and pentanoic acids were observed to be the compounds with the most significant effect on sensory odor. For the swine sites, in addition to these gases, higher molecular weight compounds such as phenol, 4-methyl phenol, 4-ethyl phenol, and 1H-indole were also observed to be significant predictors of sensory odor. When all VOCs were excluded from the model, significant correlations between odor and H2S and NH3 concentrations were still observed. Although these coefficients of determination were lower when only H2S and NH3 were used, they can be used to predict odor variability by up to 83% when VOC data are unavailable.

Odor and odorous chemical emissions from animal buildings: Part 2. odor emissions

This study was an add-on project to the National Air Emissions Monitoring Study (NAEMS) and focused on comprehensive measurement of odor emissions considering variations in seasons, animal types, and olfactometry laboratories. Odor emissions from four of 14 NAEMS sites with nine barns/rooms (two dairy barns at the WI5B and IN5B sites, two pig finishing rooms at IN3B, and two sow gestation barns and a farrowing room at the IA4B site) were measured during four 13-week cycles. Odor emissions were reported per barn area (OU h-1 m-2), head (OU h-1 head-1), and animal unit (OU h-1 AU-1). The highest overall odor emission rates were measured in summer (1.2 × 105 OU h-1 m-2, 3.5 × 105 OU h-1 head-1, and 6.2 × 105 OU h-1 AU-1), and the lowest rates were measured in winter (2.5 × 104 OU h-1 m-2, 9.1 × 104 OU h-1 head-1, and 1.5 × 105 OU h-1 AU-1). The highest ambient odor concentrations and barn odor emissions were measured from the sow gestation barns of the IA4B site, which had unusually high H2S concentrations. The most intense odor and the least pleasant odor were also measured at this site. The overall odor emission rates of the pig finishing rooms at IN3B were lower than the emission rates of the IA4B sow gestation barns. The lowest overall barn odor emission rates were measured at the IN5B dairy barns. However, the lowest ambient odor concentrations were measured at the ventilation inlets of the WI5B dairy barns.

Odor and odorous chemical emissions from animal buildings: Part 2- odor emissions

This study was an add-on project to the National Air Emissions Monitoring Study (NAEMS) and focused on comprehensive measurement of odor emissions. Odor emissions from two animal species (dairy and swine) from four sites with nine barns/rooms (two dairy barns in Wisconsin, two dairy barns and two swine rooms in Indiana, and three swine barns in Iowa) during four cycles (13-week periods) were measured. Odor samples were analyzed in three olfactometry laboratories and no significant difference was found among these laboratories. The highest ambient odor concentrations and barn odor emissions were measured for the Iowa swine site. The most intense odor and the least pleasant odor were also measured for this site. Ambient odor concentrations were the lowest for the Wisconsin dairy site. But the lowest barn odor emission rates were measured for the Indiana dairy site. Significantly higher odor emissions were measured in summer.

Odor and Chemical Emissions from Dairy and Swine Facilities: Part 1 – Project Overview and Collection Methods

Livestock facilities have received numerous criticisms due to their emissions of odorous air and chemicals. Hence, there is a significant need for odor emission factors and identification of principle odorous chemicals. Odor emission factors are used as inputs to odor setback models, while chemical emission factors may be compared with regulations to demonstrate possible health impacts.

Odor and odorous chemical emissions from animal buildings: Part 4- correlations between sensory and chemical measurements

This study supplemented the National Air Emissions Monitoring Study (NAEMS) by making comprehensive measurements, over a full calendar year, of odor emissions from five swine and four dairy rooms/buildings (subset of the total number of buildings monitored for the NAEMS project). The measurements made in this project included both standard human sensory measurements using dynamic forced-choice olfactometer and a novel chemical analysis technique for odorous compounds found in these emissions. Odor and hydrogen sulfide (H2S) and ammonia (NH3) concentrations for all dairy and swine buildings had a statistically significant correlation. A higher number of correlations between odor and volatile organic compounds (VOCs) were found for the five swine rooms/buildings (two rooms in a pig finishing barn, two sow gestation barns, and a farrowing room) compared to the four dairy buildings. Phenol and 4-methyl phenol (p-cresol) concentrations were well correlated (R2 > 50%) with odor concentrations in the five swine rooms/buildings but not significantly correlated in the four dairy buildings.

Odor and odorous chemical emissions from animal buildings: Part 5 -correlations between odor intensities and chemical concentrations (GC-MS/O)

Simultaneous chemical and sensory analysis based on gas chromatography-mass spectrometry-olfactometry (GC-MS-O) of air samples from livestock operations is a very useful approach for quantification of target odorous gases and also for ranking of odorous compounds. This information can help link specific gases to odor, that can assist in solving farm odor problems and in evaluating of odor mitigation technologies. In this study, we applied the fundamental Weber-Fechner law to correlate the odor intensity and odorous chemical concentration for 15 individual target compounds (from GC-MS-O) for the gas samples collected from four livestock facilities (dairy barns in Wisconsin and Indiana and swine barns in Iowa and Indiana) over a one year period. The results showed that most of the correlations between odor intensities and chemical concentrations for the 15 odorous VOCs sampled fit well with the Weber-Fechner law and had correlation coefficient (R2) greater than 0.65, with R2s of 0.84, 0.83, and 0.82 for 4-methylphenol, 3-methylbutanoic acid, and 3-methylindole, respectively. The odorous compounds with higher mean odor activity value (OAV) values fit better with the Weber-Fechner law whereas the odorous compounds with lower mean OAV values resulted in relatively poor R2 values to the relatively large variations for odor intensities obtained from GC-MS/O for these compounds with low concentrations. The correlations for odorous compounds between odor intensities and chemical concentrations for swine sites were much better than that for dairy sites. R2s for eight out of fifteen compounds for the two swine sites were greater than 0.60 whereas only one R2 (butyric acid) was greater than 0.60 for two dairy sites.

Odor and Odorous Chemical Emissions from Animal Buildings: Part 3- Chemical emissions

This study was an add-on study to the National Air Emission Monitoring Study (NAEMS). The objective of this study was to measure odor emissions and corresponding concentrations and emissions of target odorous gases. Odor and odorous gas measurements at four NAEMS sites (dairy barns in Wisconsin-WI5B and Indiana-IN5B, swine finisher barn in Indiana-IN3B and swine gestation/farrowing barns in Iowa-IA4B) were conducted during four-13 weeks periods over ~1 year. Odorous gas samples were collected every two weeks using sorbent tubes and analyzed by the automated one-step thermal desorption-GC-MS-Olfactometry. In this paper, we summarize measured concentrations and emissions of 15 odorous gases from four sites. The average volatile fatty acids (VFAs) concentrations ranged between1.1 and 121 µg m-3. The average phenolics and indolics concentrations varied from 0.03 to 42 µg m-3. The total volatile organic compound VOC emission rates for 15 compounds for four sites ranged between 8.89 and 546 mg/hr-m2. Only acetic acid (p<0.05) and propanoic acid (p<0.1) had a seasonal significant difference for IA4B. For IN3B, 4-ethyl phenol and indole and most of VFAs (except hexanoic and heptanoic acid) have the seasonal significant differences. At the WI5B dairy site, there were five VFAs (acetic, propanoic, 2-methyl propanoic, butyric and 3-methylbuanoic acid) and one phenolics ( 4-methyl phenol) showing a seasonal significant difference. Only three compounds (2-methoxyphenol, 1-(2-aminophenyl)-ethanone and indole) had a seasonal significant difference for IN5B. Between dairy sites (WI5B vs. IN5B), acetic, propanoic, 2-methyl propanoic, butyric, and 3-methyl butanoic acids were significantly different. Most of odorants were significantly different except heptanoic acid, 1-(2-aminophenyl)-ethanone and 3-methyl indole, between the two swine sites (IA4B vs. IN3B). Between the two different species (Dairy vs. Swine), five odorants including acetic and heptanoic acid, phenol, 4-ethylphenol, 1-(2-aminophenyl) ethanone were not significantly different, whereas the other 10 compounds measured were.

Downwind Odor Analysis Using a Field Olfactometer and a Handheld Weather Station

Annoying odors emitted from livestock production sites can be an issue for both neighbors and producers, and can lead to nuisance lawsuits and community complaints. One way to minimize such conflicts is to provide the industry with recommendations of odor setback distances. While national/local level setback laws may exist, these distance rules may sometimes be unfair to neighbors or a producer. Hence, development and refinement of scientifically-founded odor setback models, such as the Purdue Odor Setback Model, is ongoing.