Edward A Caraway

EFFECT OF WIND TUNNEL AIR VELOCITY ON VOC FLUX FROM STANDARD SOLUTIONS AND CAFO MANURE/WASTEWATER

Researchers and practitioners have used wind tunnels and flux chambers to quantify the flux of volatile organic compounds (VOCs), ammonia, and hydrogen sulfide and estimate emission factors from animal feeding operations (AFOs) without accounting for effects of air velocity or sweep air flow rate. Laboratory experiments were conducted using a small rectangular wind tunnel (30.5 cm length, 15.2 cm width, 5.1 cm height). The objectives of the research were to (1) quantify the effect of wind velocity on VOC flux rates, (2) compare and contrast a two-film model with different wind speed corrections, and (3) provide insight into methods for either selecting appropriate wind tunnel velocities or conducting post-sampling wind velocity corrections to simulate field emission rates. Fluxes were measured on standard solutions and on manure/wastewater from beef cattle and dairy AFOs. Volumetric air exchange rates were varied between 0.6 and 44 exchanges per minute, corresponding to calculated longitudinal air velocities of 0.003 to 0.23 m s-1. Exhaust air was sampled using stainless steel sorbent tubes and analyzed for eleven volatile organic compounds comprised of seven volatile fatty acids (VFAs: acetic, propionic, isobutyric, butyric, isovaleric, valeric, and hexanoic) and four heavier molecular weight semivolatile organic compounds (sVOCs: phenol, p-cresol, indole, and skatole) using gas chromatography/mass spectrometry. Sulfur-containing VOCs were quantified using a portable total reduced sulfur meter. Flux rates for VOCs with small dimensionless Henrys law constants (i.e., those found at AFOs) increased with increasing air velocity. The two-film model with an experimentally derived reference gas-film transfer coefficient was found to reliably predict VOC flux at velocities between 0.003 and 0.23 m s-1. However, the two-film model did not reliably predict VOC flux with other air velocity correction formulae, an indication that flux is a function of wind tunnel geometry and turbulence factors, and not just average air velocity or sweep air flow rate. These results corroborate other studies that show that air velocity is a major factor affecting VOC fluxes from AFOs, verifying that an air velocity correction factor is required for estimating accurate VOC emission factors using wind tunnels and flux chambers.

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.

CONTINUOUS AMMONIA EMISSION MEASUREMENTS FROM A COMMERCIAL BEEF FEEDYARD IN TEXAS

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 (NH3) 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 NH3 were compared with the mass balance of N for the feedyard. Mean annual NH3 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 µg m-2 s-1 (2.2 kg m-2 year-1). Mean monthly flux density ranged from 42.7 to 123.1 µg 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 NH3. The inverse modeled daily ammonia production per head was 85.3 g NH3-N (head fed)-1 d-1.

Odor Control in Waste Management Lagoons via Reduction of p-Cresol using Horseradish Peroxidase

Para-cresol, p-ethyl phenol and isovaleric acid have been identified as the most persistent and most significant contributors to odor 1.6 km downwind from waste lagoons in concentrated animal feeding operations (CAFOs), even though more than 200 volatile compounds contribute to odor from these lagoons. Previous studies have indicated that horseradish peroxidase (HRP) coupling with p-cresol generates a high yield of a unique product, Plummerers ketone. Our preliminary laboratory studies with synthetic p-cresol, hydrogen peroxide, and HRP demonstrated that p-cresol can be reduced significantly in a hydrogen peroxide catalyzed reaction with HRP. Using GC/MS and SPME technologies, a 75% reduction was observed in relative concentrations of 100 ml 1% p-cresol after treatment with 1 ml of 170 units of HRP (prepared at 170 units/mg and 1 mg/ml) in the presence of 3% hydrogen peroxide. Further analyses using semi- volatile organic analyses- GC/MS shows a 41% reduction in the amount of p-cresol in the samples treated with HRP in the presence of hydrogen peroxide. Data obtained from these preliminary studies demonstrate that HRP has the potential to reduce the p-cresol content in CAFO effluent and has been a basis for further studies.

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.

A multi-year field olfactometry study near a concentrated animal feeding operation.

ABSTRACT This study developed and tested a protocol for monitoring odors near a Concentrated Animal Feeding Operation (CAFO). The Nasal Ranger, a portable field olfactometry instrument, was used by a panel of trained individuals to conduct the monitoring near a swine CAFO. Monitors were selected based on olfactory sensitivity, scheduling availability, and lack of association with the CAFO or residential neighbors of the CAFO. Monitors were trained to use the Nasal Ranger, collect and record weather data, and characterize any odors detected. Data were collected over a 3-year period (2007-2009) for approximately 9 months each year. The data recorded included odor intensity, a description of the odor, date and time of the reading, and weather conditions. Of more than 50,000 readings, forty-one (0.1%) odor readings had a dilution to threshold ratio (D/T) of ≥ 7:1 and were attributed to hog manure. The frequency of odor readings attributed to hog manure with D/T ≥7:1 was found to negatively correlate with log wind speed and positively correlate with wind from the direction of the farm. Other meteorological variables (temperature, precipitation, cloud cover) and time of day did not influence the frequency. IMPLICATIONS The use of a portable field olfactometry instrument can provide an assessment of the intensity, frequency and duration of odor in real time. Along with descriptors of the odors being detected, such data can provide a basis for the evaluation of odor complaints.

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.

Effect of Wind Tunnel Air Velocity on VOC Flux Rates from CAFO Manure and Wastewater

Wind tunnels and flux chambers are often used to measure volatile organic compound (VOC) emissions and estimate emission factors from animal feeding operations (AFOs) without regard to air velocity or sweep air flow rates. Laboratory experiments were conducted to evaluate the effect of wind tunnel air velocity on VOC emission rates. VOC emissions were measured on standard solutions of VOCs in water, and on manure and wastewater from beef cattle and dairy AFOs at wind tunnel air velocities between 0.003 and 0.2 m/s corresponding to volumetric air exchange rates of 0.6 to 39 exchanges per minute. Activated-carbon-filtered air was passed through a small rectangular wind tunnel (30.5 cm length, 15.2 cm width, 5.1 cm height). Outlet air was sampled using stainless steel sorbent tubes (Tenax® TA) and analyzed for seven volatile fatty acids (acetic, propionic, isobutyric, butyric, isovaleric, valeric, hexanoic) and four heavier molecular weight (MW) semi-VOCs (phenol, p-cresol, indole and skatole) using gas chromatography/mass spectrometry. VOC emission rates increased linearly with increasing wind velocity. These results show that wind velocity is a major factor affecting VOC emissions from AFOs. Selection of representative air velocity or sweep air flow rate is critical when estimating VOC emission factors using wind tunnels and flux chambers.

Ammonia Concentration and Modeled Emission Rates from a Beef Cattle Feedyard

Ambient NH3 concentrations were measured at a beef cattle CAFO during the spring and summer months of 2007. Concentrations were measured every five minutes, 24-hours per day at a sample intake height of 3.3 m using a chemiluminescence analyzer. On site weather data was collected concurrently. Emission rates were estimated using a backward Lagrangian Stochastic model (WindTrax 2.0.7.8). Mean 24-hr concentrations for spring were 0.498, 0.597 and 0.568 ppm for March, April and May, respectively. Corresponding fluxes for March, April and May were 57.76, 123.10 and 86.34 µg m-2 sec-1, respectively. Summer mean ambient concentrations were 0.684, 0.702 and 0.568 ppm for June, July and August, respectively. Summer fluxes were 85.27, 75.06 and 71.56 µg m-2 sec-1 for June, July and August, respectively.

Identification of Malodorous Compounds from a Fish Meal Plant

Odor emissions and control of nuisance odors are important to the agriculture industry because of growing populations around processing operations. Spoilage of fish and associated odors are due to activities of enzymes produced by pseudomonas patheromonas strains. The possibility of removing only those odorants that have long-distance contributions appears to be a more achievable and cost-effective means of controlling downwind odors than addressing all odorous compounds. A research project was conducted at a fish meal plant to identify those specific compounds that contribute significantly to the overall downwind odor. Sampling was conducted using Tedlar® bags, thermal desorption tubes and personal vacuum pumps. The study employed gas chromatography/mass spectrometry-olfactometry (GC/MS-O). The overlaying of chemical analyses results with human panelist data indicated the most offensive odors detected were trimethylamine (TMA) and dimethyl sulfide (DMS). The information was used to successfully design mitigation strategies for reduction of odors downwind of the plant.