Brian P. Hetchler

Quality assured measurements of animal building emissions: Odor concentrations

Abstract Standard protocols for sampling and measuring odor emissions from livestock buildings are needed to guide scientists, consultants, regulators, and policy-makers. A federally funded, multistate project has conducted field studies in six states to measure emissions of odor, coarse particulate matter (PM10), total suspended particulates, hydrogen sulfide, ammonia, and carbon dioxide from swine and poultry production buildings. The focus of this paper is on the intermittent measurement of odor concentrations at nearly identical pairs of buildings in each state and on protocols to minimize variations in these measurements. Air was collected from pig and poultry barns in small (10 L) Tedlar bags through a gas sampling system located in an instrument trailer housing gas and dust analyzers. The samples were analyzed within 30 hr by a dynamic dilution forced-choice olfactometer (a dilution apparatus). The olfactometers (AC’SCENT International Olfactometer, St. Croix Sensory, Inc.) used by all participating laboratories meet the olfactometry standards (American Society for Testing and Materials and European Committee for Standardization [CEN]) in the United States and Europe. Trained panelists (four to eight) at each laboratory measured odor concentrations (dilution to thresholds [DT]) from the bag samples. Odor emissions were calculated by multiplying odor concentration differences between inlet and outlet air by standardized (20 °C and 1 atm) building airflow rates.

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.

Comparison of Gas Sampling Bags to Temporarily Store Hydrogen Sulfide, Ammonia, and Greenhouse Gases

The National Air Emission Monitoring Study (NAEMS) project measured gas concentrations using automated semi-continuous gas analyzers. An alternative gas sampling technique is to use portable systems to fill 50 L gas sample bags over 24 h sampling periods and measure gas concentrations later in the laboratory. For this technique, a gas sampling bag that can retain gases over 24 h is needed. The objective of the study was to assess the impact of initial gas concentrations (low, medium, and high) and storage times (2, 6, 12, 24, 36, 48 h) on hydrogen sulfide, total reduced sulfur (TRS), ammonia, methane, and nitrous oxide stability in Tedlar and FlexFoil bags. Average gas concentrations ranged from 771 to 2,655 ppb, from 782 to 2,750 ppb, from 657 to 1,997 ppb, from 10,441 to 13,803 ppb, and from 337 to 344 ppb for H2S, TRS, NH3, CH4, and N2O, respectively. Bag reusability and background contamination were also investigated. Percent recoveries from FlexFoil bags ranged from 75% to 99.5% for all gases and concentrations except for TRS at high concentrations. For TRS at high concentrations, percent recovery from FlexFoil bags was 68.8%. No gas desorption or permeation was observed when using new FlexFoil bags. FlexFoil bags were more durable than Tedlar bags to mechanical stress and aging effects. There was no need to use a cover for FlexFoil bags to protect samples from sunlight. The cost of FlexFoil bags was lower than that of Tedlar bags.

Air Emissions from Tom and Hen Turkey Houses in the U.S. Midwest

Limited data exist in the literature regarding air emissions from U.S. turkey feeding operations. The project described in this article continuously monitored ammonia (NH3) and particulate matter (PM) emissions from turkey production houses in Iowa (IA) and Minnesota (MN) for 10 to 16 months, with IA monitoring Hybrid tom turkeys (35 to 143 d of age, average market body weight of 17.9 kg) for 16 months and MN monitoring Hybrid hens (35 to 84 d of age, average market body weight of 6.7 kg) for 10 months. Mobile air emission monitoring units (MAEMUs) were used in the continuous monitoring. Based on the approximately one-year measurement, each involving three flocks of birds, daily NH3, PM10, and PM2.5 concentrations (mean ±SD) in the tom turkey barn were 8.6 ±10.0 ppm, 1104 ±719 µg m-3, and 143 (±124) µg m-3, respectively. Daily NH3 and PM10 concentrations (mean ±SD) in the hen turkey barn were 7.3 ±7.9 ppm and 301 ±160 µg m-3, respectively. Daily NH3 concentrations during downtime (mean ±SD) were 38.4 ±20.5 and 20.0 ±16.3 ppm in the tom and hen barns, respectively. The cumulative NH3 emissions (mean ±SE) were 141 ±13.1 and 1.8 ±0.9 g bird-1 for the tom turkeys during 108 d growout and 13 d downtime, respectively, and 52 ±2.1 and 28.2 ±2.5 g bird-1 for the hen turkeys during 49 d growout and 32 d downtime, respectively (the extended downtime for the hen house was to ensure monitoring of one flock per season). The cumulative PM10 emission (mean ±SE) was 28.2 ±3.3 g bird-1 for the tom turkeys during 108 d growout and 4.6 ±2.2 and 0.3 ±0.06 g bird-1 for the hen turkeys during 49 d growout and 32 d downtime, respectively. Downtime in the hen house was of greater duration than would be typically observed (32 d vs. 7 d to 14 d typical). The cumulative PM2.5 emission (mean ±SE) was 3.6 ±0.7 g bird-1 for the tom turkeys during 108 d growout (not monitored for the hen turkeys). Because farm operations will vary in flock number, growout days, and downtime; annual emissions can be calculated from the cumulative emissions and downtime emissions per bird from the data provided. Air emissions data from this study, presented in both daily emission and cumulative per-bird-marketed emission, contribute to the improved U.S. national air emissions inventory for animal feeding operations.

AIRFLOW REDUCTION OF LARGE BELT-DRIVEN EXHAUST VENTILATION FANS WITH SHUTTERS AND LOOSE BELTS

Two tunnel ventilated sow gestation buildings (78 m x 15 m), each holding approximately 645 sows, were monitored for emissions of ammonia (NH3), carbon dioxide (CO2), hydrogen sulfide (H2S), odor, and particulate matter 10 µm or less (PM10) for a large multi-state research project that collected data for 15 months. In order to measure emissions, ventilation rates from each barn were periodically measured using a portable Fan Assessment Numeration System (FANS) unit, that measured airflow capacity of the six (5 – 122 cm and 1 – 91 cm diameter blade fans) exhaust fans at one end of each barn. During the first routine airflow measurements of the large (122 cm diameter) belt-driven fans it was determined that when the fan drive belts were slightly loose that belt slippage occurred and the fan airflow delivery was reduced by 30 to 60% of the fan airflow delivery when the belts were properly tightened. This large reduction in airflow delivery represents a significant reduction in the total ventilation rate for these sow facilities since a large majority of the airflow capacity was provided by these belt-driven fans. Belt-driven fans are commonly used to provide most of the airflow capacity in tunnel ventilated buildings in the U.S. and elsewhere in the world. Belt slippage and dirty shutters can result in serious under ventilation of the barns, providing inadequate environmental control for the animals housed in these buildings.

Real-Time Ventilation Measurements from Mechanically Ventilated Livestock Buildings for Emission Rate Estimations

A six-state USDA-IFAFS funded research project (Aerial Pollutant Emissions from Confined Animal Buildings, APECAB) was conducted with the purpose of determining hydrogen sulfide, ammonia, PM10, and odor emission rates from selected swine and poultry housing systems. An important aspect of emission studies is to be able to measure the mass flow rate of air through the housing system. For this research project, the decision was made to study only fan ventilated buildings due to the difficulty in estimated mass flow rates through naturally ventilated buildings. This paper highlights the various techniques used throughout the study to determine mass flow rate through fan ventilated swine and poultry housing systems.

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.

COMPARISON OF IMPACT PLATE AND TORQUE-BASED GRAIN MASS FLOW SENSORS

The performance of two grain flow sensors was compared on a stationary combine in the laboratory. The separator mechanism was intact, and the threshing cylinder was immobilized. Grain flow to the machine was controlled by electronically modulating gate valves on two grain conduits. Base grain flows ranged from 0.91 to 6.36 kg/s in 0.91 kg/s steps. Perturbations of 0.91, 1.82, and 2.73 kg/s could be introduced into the machine through a separate conduit. The results showed that the torque sensor was ten times more sensitive to changes in flow rate when compared to the impact plate sensor. Standard errors for both sensors increased at flow rates below 3 kg/s. For flows less than 1 kg/s, the standard error for the impact plate sensor was ±60%, and the standard error for the torque sensor was ±18%. At flow rates greater than 3 kg/s, the error for the impact plate sensor was ±15%, whereas the error for the torque sensor was ±5%. Measuring the torque required to lift the grain in the clean grain elevator is an alternative and more precise method of quantifying grain flow when compared to the impact plate sensor.