Diurnal and annual variation of odour emission from animal houses: a model calculation for fattening pigs

Odour emission from livestock buildings adjacent to residential areas may constitute an environmental nuisance and dispersion models are of interest in the regulation of air pollutants. To apply dispersion models to odour emissions, the odour concentration and the volume flow of the outlet air must be known. In this paper, the odour concentration of the outlet air is determined by combining a steady-state balance model to calculate the outlet air temperature and the volume flow with a simple model for the odour release inside the livestock building. The results show a distinct diurnal and annual variation of the odour concentration due to the variability of the volume flow. The mean odour concentration during daytime in the summer months lies in a very narrow range close to the overall minimum. Odour concentration derived from odour emission and the maximum volume flow of the animal house is useful for model calculations. During a clear-sky summer period, the model predicts a nighttime odour concentration of about 4.6 times the daytime concentration due to the reduced volume flow at night. To improve the calculation of odour concentrations by dispersion models, the annual and diurnal variation of the odour release has to be taken into account. The model suggests that long-term measurements of the odour emissions of animal houses are necessary for regulatory and legal purposes. (C) 1999 Silsoe Research Institute.