Site-specific influences on diffusion of odours released by animal housing systems

The Swiss Agency for the Environment, Forests and Landscape (SAEFL) commissioned the Swiss Federal Research Station for Agricultural Economics and Engineering (FAT) in Tänikon to revise the FAT report no. 476 on minimal distances of animal housing systems (Richner, Schmidlin, 1995). In general, the existing guideline proved to be useful for closed houses with forced ventilation. Municipalities and cantonal environmental agencies consider it to be a good working tool and apply it consistently. However, the guideline does not sufficiently take into account open housing systems and houses with an exercise yard, particularly in pig keeping. Therefore, housing systems which present a certain potential for odour nuisance are examined and assessed, with special emphasis on topographic influences on odour diffusion. As opposed to systems with forced ventilation, the new housing systems present diffuse odour sources near the ground. People living near pig houses with an exercise yard mainly complain about odour nuisances when cold air flows off. Complaints are more often made in summer, when people spend more time outside or leave the windows open at night. In autumn 2001, measurements were carried out near pig houses at two different sites. The local meteorological parameters (temperature, wind speed and wind direction) presented significant differences in situations with and without cold air flowing off.