Influence of plume rise parameterization on odor impact assessment: A case study of open biofilters

Advances in odor impact assessment increasingly rely on accurate atmospheric dispersion modelling. In this context, odor emissions from open biofilters are commonly modelled as non-buoyant area sources, implicitly neglecting plume rise effects. However, the biological activity within biofilters generates heat, producing emissions warmer than ambient air and potentially inducing buoyancy-driven plume rise. This study investigates the influence of plume rise parameterization on odor dispersion modelling from open biofilters using the CALPUFF model. A series of simulations is performed considering different source configurations (point, area, and buoyant area), and plume rise algorithms (Briggs and numerical). Results show that neglecting plume rise, as typically done in the literature, leads to substantial overestimations of odor concentrations compared to the other investigated scenarios. Including buoyancy effects produces outcomes that appear more physically consistent and representative of real emission behaviour, with comparable results between point and buoyant area sources. Within the spectrum of available algorithms, the semi-empirical formulation is inherently limited by simplifying assumptions, while numerical approaches exhibit enhanced physical robustness as they are subject to fewer constraints. Overall, the findings emphasize the importance of accounting for buoyancy in modelling open biofilters and suggest that common simplifications may lead to overly conservative outcomes.