Performance Evaluation of IDW Interpolation with a Gaussian Dispersion Model for Biodiesel Emissions

Dispersion modelling is essential for estimating the extent and magnitude of air pollution from industrial emissions. However, reliance on commercial modelling software can limit regular evaluations due to cost and accessibility. This study presents a case study from a biodiesel plant in Lampung, Indonesia, comparing results from a commercial dispersion model with a free and publicly available Geographic Information System (GIS) approach that integrates Inverse Distance Weighted (IDW) interpolation with the Gaussian dispersion equation. The study shows that, in the dry season, all pollutants showed comparable RMSE values between the two methods. While in the wet season, NO₂ indicate clearer differences, the commercial application yielded an RMSE of 2.5 µg/m³, while IDW achieved 1.2 µg/m³, highlighting the limitations of commercial software approach in handling reactive pollutants under complex meteorological conditions. The findings suggest that interpolation-based dispersion modelling can serve as a practical alternative for preliminary assessments and can assist in evaluate appropriate monitoring points to support air quality management.