Empirical model derived from dispersion calculations to determine separation distances between livestock buildings and residential areas to avoid odour nuisance

A new VDI guideline is under development in Germany to calculate the separation distance S (m) required between livestock and residential areas to avoid odour annoyance by an empirical model. On the basis of model calculations for 23 sites by a Lagrangian dispersion model (AUSTAL2000) a regression model was developed, using a power function S = aEb. The power function is defined by three input parameters which were restricted for an improved fit of the regression model. The basis of the power function is the odour emission flow rate E (ouE s−1) in the range between 500 ouE s−1 ≤ E ≤ 50,000 ouE s−1. The two other predictors are the relative frequency of the wind direction F (‰) of a 10° sector (10‰ ≤ F ≤ 60‰) and the odour exceedance probability P (%) (7% ≤ P ≤ 40%) of the odour impact criterion, which define the exponent b and the multiplicative factor a of the power function. One of the requirements for this empirical model was a conservative assessment, which results in only a 12% underestimation of the separation distance compared to the dispersion model. The model can be used in a “paper and pencil” mode, which enabling a simple and straightforward first evaluation of a planned livestock building. For a more detailed assessment, a dispersion model can be applied with the entire meteorological information available (e.g. stability of the atmosphere, wind velocity), the geometry of the emission source, a time dependant odour emission rate, as well as the orography of the site.