ODOUR AND GAS EMISSIONS, ODOUR IMPACT CRITERIA, AND DISPERSION MODELLING FOR DAIRY AND POULTRY BARNS
Very limited research has been conducted to study the concentrations and emissions of odour, toxic gases (e.g., ammonia [NH3], hydrogen sulfide [H2S]), dust, and greenhouse gases (GHGs) from dairy and poultry barns in Canada. The major goals of this dissertation work were to study both the indoor and outdoor air pollution of a dairy, cage-layer, and broiler barn under the Canadian Prairies climate condition. The five odour properties, including odour concentration (OC), odour intensity (OI), hedonic tone (HT), persistence, and character descriptor, were studied for all three barns. The broiler barn presented the highest OC, strongest OI and most unpleasantness (HT) followed by the layer barn and then the dairy barn. It was found that OC, OI, and HT were significantly correlated with each other (P<0.01); increased OC was associated with increased OI but decreased HT. Then, new odour impact criteria were developed based on the derived relationships among OC, OI, and HT, with odour concentration limits being determined under both OI and HT limits. Seasonal concentration and emission profiles of odour, NH3 and H2S, GHG (carbon dioxide [CO2], methane [CH4], and nitrous oxide [N2O]), and respirable dust were characterized for the dairy, broiler, and layer barns by long-term monitoring over a year, and diurnal profiles of odour and gas concentrations and emissions were identified by continuous measurements for two days in mild, warm, and cold seasons, respectively. With NH3, H2S, and respirable dust concentrations, the indoor air quality of the three barns in different seasons were evaluated by not only considering the occupational health effect (respiratory irritation) of these individual air pollutants, but also their additive health effect. The worst indoor air quality was observed for the broiler barn followed by the dairy barn and then the layer barn. Also, the emission factors of odour, gases, and respirable dust were acquired. The highest annual average odour and NH3 emissions were from the layer barn (140 OU s-1 AU-1 and 1.10 mg s-1 AU-1), followed by the broiler barn (127 OU s-1 AU-1 and 1.06 mg s-1 AU-1) and then the dairy barn (45.9 OU s-1 AU-1 and 0.53 mg s-1 AU-1). The annual average CO2 and CH4 emissions were 116 and 3.1 mg s-1 AU-1 for the dairy barn, 437 and 0.06 mg s-1 AU-1 for the broiler barn, and 435 and 0.21 mg s-1 AU-1 for the layer barn. The impact of environmental parameters (T, RH, and VR) on concentrations and emissions of odour and gases were investigated, and then prediction models for odour emission were developed depending on the environmental parameters. To validate the performance of AERMOD for predicting odour dispersion, field odour plume measurements were conducted around the broiler barn. In consistent with previous studies, the modelled results were all greatly below the field measured results. Thus, scaling factors were generated to improve the comparison. One scaling factor was 286 by plotting all data and the other was 154 by only using the geometric mean of each odour plume. Both scaling factors achieved good agreements between model predictions and field measurements; however, the scaling factor of 154 was suggested to use due to its better performance over short distances (100-200 m). With the variable emission rates of odour, NH3, H2S, and respirable dust, dispersion modelling of the four air pollutants were conducted by the AERMOD dispersion model for all three barns to study their outdoor impact. Using both the recommended odour impact criteria by the Government of Saskatchewan (2012) and the developed odour impact criteria for the three barns in this study, directional setback distances were determined with the ambient threshold limits of NH3, H2S, and respirable dust being complied with. Additionally, odour impact criteria were found to be stricter than that of gases and respirable dust as the former always required greater setback distances than the latter.
Odor, Gas, Emission, Dispersion modelling, Dairy barn, Poultry barn
Doctor of Philosophy (Ph.D.)
Chemical and Biological Engineering
Agriculture and Bioresource Engineering