Evaluating Tier 1 sox emission estimates for a petroleum refinery: a case study

Accurate quantification of sulphur oxide (SOx) emissions from petroleum refineries is essential for regulatory compliance, environmental impact assessment and air quality management. In the absence of site-specific data, the EMEP/EEA Tier 1 methodology is often applied, using generalized emission factors derived from EU-27 averages. While this approach provides harmonized estimates for largescale inventories, its applicability at the facility scale is limited, as it does not capture refinery-specific variables such as crude sulphur content, process configuration and abatement technology performance. This study evaluates the reliability of Tier 1-derived SOx emissions for a refinery in the Marche Region (Italy) by comparing them with operator-reported emissions and with ambient concentrations measured at the nearby FS_obs monitoring station. Gaussian dispersion simulations using AERMOD were performed for both emission datasets and the resulting monthly mean concentrations were compared against observations. Results show that Tier 1 estimates overpredicted measured concentrations by approximately 35% but reproduced seasonal trends with good agreement, whereas refinery-reported values significantly underestimated observations. Both scenarios exhibited high correlation with monitoring data, highlighting that temporal patterns can be captured even when magnitude biases occur. The analysis also reveals that the FS_obs station, despite its proximity to the refinery, is influenced by multiple sources, including maritime traffic from the Port of Ancona.