K. A. Janni

Odor, Total Reduced Sulfur, and Ammonia Emissions from Animal Housing Facilities and Manure Storage Units in Minnesota

The quantification of odor, total reduced sulfur (TRS), and ammonia (NH3) emissions from animal housing facilities and manure storage units is essential for the development and implementation of improved setback evaluation methods and tools. This observational study measured odor, TRS, and NH3 levels emitted from more than 200 animal housing facilities and manure storage units on 85 farms in Minnesota. Emissions were highly variable in accordance with observations from other large air quality studies. Possible reasons for the large variation in emissions data included differences between sampling sites and season or ambient temperature. Odor, TRS, and NH3 emissions were typically highest from swine housing facilities and concrete tanks containing swine or dairy manure. Pearson’s correlation matrix calculated significant (p < 0.05) and strong correlations between odor and TRS emissions (r = 0.947) and odor and NH3 emissions (r = 0.954) from swine housing only. Therefore, TRS and/or NH3 emissions from swine housing facilities are potential proxies for odor emissions. This study was strictly observational and not a controlled experiment. Thus, odor TRS and NH3 emissions reported in this study may not apply to other geographic locations.

Biofilter performance of pine nuggets and lava rock as media.

Wood chips and bark mulch are commonly used biofilter media because they are generally locally available and inexpensive. Nevertheless, these organic materials degrade and require replacement every 2-5 years. In this study, airflow characteristics and gas reduction efficiencies of two alternative biofilter media (pine nuggets and lava rock) with high porosity and potentially longer service lives were evaluated at three empty bed contact times (1, 3, and 5s) and two moisture levels (82% and 90% relative humidity). The lava rock had a lower pressure drop across the media and maintained higher media depth. Gas reduction efficiencies were highest for lava rock at 5s empty bed contact time and 90% humidity. The reduction efficiencies at these conditions were 56%, 88%, 87%, 25%, and 0.7% for ammonia, hydrogen sulfide, total reduced sulfur, methane and nitrous oxide, respectively. Odor reduction up to 48% was observed but was not consistent.

AMMONIA REMOVAL DURING BIOFILTRATION AS AFFECTED BY INLET AIR TEMPERATURE AND MEDIA MOISTURE CONTENT

Biofiltration is a promising technology for minimizing odor and gas emissions from livestock buildings. A laboratory experiment investigated N accumulation and N transformations to better understand how biofilters remove airborne NH3. Total-N accumulated in the media accounted for only 29% of the N removed by the biofilter after 1160 h. The fate of the remaining N is unknown. Nitric oxide (NO) gas emission accounts for only a small part (<2%) of the difference, and no N was lost via leaching. Microsite denitrification to dinitrogen (N2), nitrogen dioxide (NO2), or nitrous oxide (N2O) may explain some of the discrepancy, but further research is needed. An attempt to determine N transformation rates was not successful due to continuous modeled circular N transformations. Despite these unexplained N fates, this experiment showed that biofiltration can effectively remove NH3 levels from exhaust air.

Three-Dimensional Buoyant Turbulent Flows in a Scaled Model, Slot-Ventilated, Livestock Confinement Facility

A three-dimensio nal turbulence model was used to determine the effects of animal-genera ted buoyant forces on the airflow patterns and temperature and airspeed distributions in a ceiling-slot, ventilated, swine grower facility. The model incorporated the Lam-Bremhorst turbulence model for low-Reynolds Number airflow typical of slot-ventilated, livestock facilities. The predicted results from the model were compared with experimental results from a scaled-enclosu re. The predicted and measured results indicated a rather strong cross-stream recirculation zone in the chamber that resulted in substantial threedimensional temperature distributions for moderate to highly buoyancy-affected flows. Airflow patterns were adequately predicted for Ar^ > 40 and J values 0.00053, the visualized patterns indicated that the jet separated from the ceiling before the opposing end-wall. This discrepancy was attributed to variations in the experimental and numerical inlet flow development assumptions.

SULFUR AND NITROGEN BALANCES IN BIOFILTERS FOR ODOROUS GAS EMISSION CONTROL

Biofiltration is a promising technology for reducing odor and gas emissions from livestock operations. Two important operating parameters in biofiltration—media moisture content (MC), and gas retention time (RT)—were studied to determine their effects on sulfur (S) and nitrogen (N) balances. Laboratory experiments were carried out to determine S and N accumulation in and emissions from biofilters with various media MC (30%, 40%, 50% wb) and RT (5, 10, 20 s). The biofilter media was a mixture of compost and wood chips. The media bed was 0.20 m deep and 0.30 m in diameter. Two trials (replications) were run. Results showed that 47% to 94% of the hydrogen sulfide (H 2 S) and 25% to 90% of the ammonia (NH 3 ) were removed by the biofilters. Removal efficiency varied with treatment. Biofilters with 50% MC and 20 s RT had the largest removal efficiencies for both H 2 S and NH 3 , with average H 2 S removal rates of 92.8% in Trial 1 and 94.2% in Trial 2. Average NH 3 removal efficiencies of these biofilters (50% MC and 20 s RT) were 90.3% in Trial 1 and 75.8% in Trial 2. S and N accumulation in the biofilter media was also affected by MC and RT. Accumulation models for S and N in the media were developed and reported.

Dynamic olfactometry variability in determining odor dilutions-to-threshold

When conducting research on odor abatement technologies, a weak link has been the inability to place a precise quantifying number on odor strength that can be accurately reproduced within the same laboratory and between laboratories. Olfactometry is one of the most accepted means for evaluating odor samples. However, insufficient effort has been made to determine variation between or among individual panelists. This study was designed to analyze three odor sample strengths over a three-day period by two odor panels, each composed of eight panelists. Three sample strengths were presented randomly to each panelist three times within each session. Whole-panel variation ranged from a 22% to 50% difference in reported odor units for the same sample, depending on sample strength. Using two different airflow rate calibrations resulted in a 9% to 28% difference in odor units for the same sample, depending on sample strength. Panelist variation ranged from 4.3- to 7.1-fold, depending on sample strength, although panelist standardization slightly reduced this variation. Sample order had no effect on odor strength determination. A learning curve for individual panelists appeared to exist, as odor unit evaluation for later observations were 3.8 and 4.1 times greater than similar evaluations for the first samples. Variation between panelists is approximately the same as variation among evaluations done by the same individual; efforts should be made to reduce both these variations. To be able to detect differences in odor concentrations between control and treatment samples, large reductions in odor concentrations with several air samples are needed to accurately detect a significant reduction in odor.

Compost Dairy Barn Layout and Management Recommendations

Compost barns are a loose housing system that provides excellent cow comfort for dairy cows. Producer experience with well-managed compost barns in Minnesota has generally been positive. Cows are relatively clean, very comfortable, have fewer lameness problems, and in some cases had lower somatic cell counts (SCC) after moving to a compost barn from tie-stall or freestall barns. Current design and management recommendations are based on dairy producer experiences. Compost barns have a concrete feed alley, a bedded pack resting area that is stirred two times a day, and a 1.2-m (4-ft) high wall surrounding the pack. The wall that separates the pack and feed alley has walkways to allow cow and equipment access to the stirred pack area. The stirred pack is sized to provide a minimum stirred bedded pack area of 7.4 m2/cow (80 ft2/cow). Producers use dry fine wood shavings or sawdust for bedding. Fresh bedding is added when the bedded pack becomes moist enough to stick to the cows. The pack is stirred (aerated) at least two times each day to a producer recommended depth of 25 to 30 cm (10 to 12 in.). Stirring aerates and mixes manure and urine on the surface into the pack to provide a fresh surface for cows to lie down on. The pack can provide manure storage for 6 to 12 months. Excellent pack management and pre-milking cow preparation procedures are required. Research on compost barns is needed.

DEVELOPMENT OF THE OFFSET MODEL FOR DETERMINATION OF ODOR-ANNOYANCE-FREE SETBACK DISTANCES FROM ANIMAL PRODUCTION SITES: PART I. REVIEW AND EXPERIMENT

The objective of the study was to develop a science-based model, OFFSET (Odor from Feedlot - Setback Estimation Tool), to establish setback distances from animal production sites based on the use of an air dispersion model (INPUFF-2) and the actual odor emission data from these sites. Extensive research was conducted to obtain representative odor emissions from various animal facilities and to evaluate the air dispersion model. Odor emissions were measured from 280 animal buildings and manure storage units on 85 farms in Minnesota during 1998 to 2001. The geometric means of the odor emission rates for each type of odor source were obtained to represent odor emissions of that source. The efficiencies of some odor control technologies were summarized. The air dispersion model was evaluated for short-distance (<0.5 km) odor dispersion prediction against the odor plumes measured by trained field assessors on 20 farms and also for long-distance (4.8 km) odor dispersion prediction against odor data recorded by trained resident observers living in the vicinity of livestock operations in a 4.8 × 4.8 km rural area. The relationship between odor detection threshold and intensity was obtained for swine and cattle odors in order to convert odor intensity to detection threshold. The results indicated that the INPUFF-2 model was capable of simulating odor dispersion downwind from animal production operations for low-intensity odors. Six stable or neutral weather conditions that favor odor transport were identified, and their historical occurrence frequencies in all 16 directions at six weather stations in Minnesota were obtained. The occurrence frequencies of these weather conditions were used to determine odor occurrence frequencies in the OFFSET model.

Aspergillus and other human respiratory disease agents in turkey confinement houses

The atmosphere of a turkey confinement house on a large Minnesota farm was examined over the course of a year in order to determine levels of airborne contaminants and to evaluate the hazard potential posed by the contaminants to farm workers. Air concentrations of total and respirable dust, ammonia, carbon monoxide, hydrogen sulfide, nitrogen dioxide, methane, and Aspergillus (a fungal respiratory disease agent) were evaluated. Inter- and intra-seasonal variations in confinement house contaminant concentrations were observed. The highest concentrations of dust, ammonia and Aspergillus occurred during the winter months when dust levels averaged 9.3 mg/m3 and ammonia levels averaged 35 parts per million (ppm). Aspergillus levels were lower than expected, never exceeding 73 colony forming units per cubic meter (cfu/m3). Ammonia levels were found to be particularly high during tilling of the confinement house when concentrations greater than 100 ppm were reached. Concentrations of carbon monoxide, hydrogen sulfide, nitrogen dioxide and methane were below detectable levels.

DEVELOPMENT OF THE OFFSET MODEL FOR DETERMINATION OF ODOR-ANNOYANCE-FREE SETBACK DISTANCES FROM ANIMAL PRODUCTION SITES: PART II. MODEL DEVELOPMENT AND EVALUATIONS

The OFFSET (Odor from Feedlots - Setback Estimation Tool) model was developed to estimate the setback distances from animal production sites in Minnesota. It is based on odor emissions taken from field measurements and an evaluated air dispersion model. The odor emissions of a site were estimated using odor emission rates that were the geometric means of odor emissions measured from 280 animal buildings and manure storage units on 85 farms in Minnesota. The odor-annoyance-free intensity level was set at 2 (faint odor) on a 0 (no odor) to 5 (very strong odor) intensity scale. An evaluated air dispersion model, INPUFF-2, was used to calculate setback distances from various animal farms for the set odor-annoyance-free level under six weather conditions that favor odor transport. Setback distances are presented in a graphic form as well as mathematically as a function of the total odor emission factor and the desired odor-annoyance-free frequency of the neighbors. Odor-annoyance-free frequencies between 91% and 99% are based on the average weather data for Minnesota from 1984 to 1992. Suggestions for odor-annoyance-free frequency selections are given. The OFFSET model also deals with residences located in different directions from a livestock site. Additionally, it can determine the odor occurrence frequency of a residence surrounded by several livestock sites. Comparing the setback distances obtained from the OFFSET model and the odor events reported by the resident observers, it was found that the OFFSET model does not overpredict odor transport distances under very stable weather conditions. By comparing the OFFSET predictions with the odor complainers’ distances from swine farms, it was clear that their residences had high odor occurrence frequencies. The OFFSET model was also evaluated by comparing odor occurrences documented by the resident odor observers in the vicinity of eight livestock farms. It was found that although the model may describe the average neighborhood intensity correctly, a high variation in the observed odor intensities existed for all levels of predicted intensities calculated from the OFFSET. Further research is needed to improve the accuracy of OFFSET and also to improve the field odor measurement method by the resident observers to obtain reliable odor occurrence data. By comparing OFFSET with four other existing setback guidelines, it was found that the distances required by the other models fell in or below the 91% to 98% annoyance-free curves of the OFFSET.