Continuous odour measurement from fattening pig units

A study in experimental slatted-system fattening pig units was conducted with the aim of estimating the odour emission factor (in ou/s.pig), which can subsequently be used in dispersion models to assess the odour annoyance zone. Dynamic olfactometry measurements carried out at different development stages of pigs showed a logical trend of the mean predicted odour emission factor with the pig weight. However, the variation within the same weight class was much larger than variation between classes. Possible causes of such variation were identified as the evolution of ventilation rate during the day and the circadian rhythm of pig. To be able to monitor continuously the daily variation of the odour, an electronic nose was used with suitable regression model calibrated against olfactometric measurements. After appropriate validation check, the electronic nose proved to be convenient, as a complementary tool to dynamic olfactometry, to record the daily variation of the odour emission factor in the pig barn. It was demonstrated that, in the controlled conditions of the experimental pens, the daily variation of the odour emission rate could be mainly attributed to the sole influence of the circadian rhythm of pig. As a consequence, determining a representative odour emission factor in a real case cannot be based on a snapshot odour sampling.