The Evaluation of the Odour Emission Rate for Passive Area Sources: a New Approach

Abstract

Usually the Odour Emission Rate (OER) for passive area sources is evaluated by means of a ventilated hood: a forced air flow is insufflated from an air cylinder in the hood in order to mimic the action of the wind and obtain a value for the emissivity of the source. The obtained OER is therefore estimated at a fixed speed – the predetermined rate of the airflow – so it is necessary to recalculate it at the proper wind speed for every instant of the time domain of the simulation. This can be done exploiting the dependence of the Odour Emission Rate on the flow rate and thus the speed; generally the speed used for this operation is the one obtained from the meteorological station. In the present work a new approach is discussed, arguing the legitimacy of the procedure just described, since for several reasons the wind speed detected at the station level may be significantly different from the one at the level of the source. In the paper it will be discussed how to obtain a better procedure capable of computing more reliable OER terms so to provide better final results. The discussion will revolve around the different classes of formulas to evaluate the wind speed at the desired height – namely logarithmic or power law – and will conclude with an overview of the most promising correlations.