# 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. From 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 3 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 E e 50,000 ouE s-1. The 2 other predictors are the relative frequency of the wind direction F () of a 10° sector (10 e F e 60) and the odour exceedance probability P (%) (7% e P e 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 1st 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 atm., wind velocity), the geometry of the emission source, a time dependant odour emission rate, as well as the orography of the site.

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