For the calculation of the separation distance to avoid odour annoyance, the odour emission rate of the livestock building has to be known as input for the dispersion model. In general, an annual mean value is used although the influence of the live mass growth of the animals as well as of indoor air temperature and ventilation rate on the emission rate is known. This simplified approach was compared with various emission scenarios for a continuous fattening system with a constant live mass of 75 kg and an all-in/all-out system. For the last one a Monte-Carlo based model (inverse transfer sampling technique) was used to avoid an interaction between the growth of the animals and the annual variation of the outdoor temperature. The variation of the emission factor was taken into account twofold, first by a schematized diurnal emission pattern for the various seasons and second by a steady state simulation of the indoor climate to calculate indoor temperature and ventilation rate which both influence the odour release. The results indicate an underestimation of the odour emission rate of a livestock building during summer compared with winter when using an annual mean value. For the all-in/all-out system, this effect is superposed by an overestimation at the beginning of the fattening period and an underestimation at the end. Using emission models which take into account the growth function and/or the indoor climate, a more realistic description of the odour emission characteristics can be achieved. This will help to increase the goodness of the assessment of environmental odour by dispersion models.
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