Modeling VOC emissions from hydrocarbon tanks: mechanistic insights vs. inventory approaches

Volatile Organic Compounds (VOCs) released from storage tanks represent a major source of air pollutants in refineries and petrochemical facilities. This study benchmarks the phenomenological tank-headspace model of Rota et al. (2001) against the standard US EPA’s AP-42 methodology using one year of hourly operational data from diesel tanks. The former formulation was re-implemented through numerical stabilization with flux limiters and a condensation sub-model, improving robustness under steep gradients and enabling to capture the possible vapor recondensation absent from the original scheme. Both approaches reproduce seasonal emission cycles but diverge in their ability to resolve transient events: the mechanistic model captures filling/emptying peaks and headspace dynamics, while AP-42 remains primarily temperature-driven. Annual emission totals are comparable, with AP-42 offering a rapid, low-input solution for inventories, and Rota et al. (2001) providing enhanced temporal resolution for short-term exposure. Results highlight a trade-off between computational demand and temporal resolution, with implications for regulatory versus process-level applications.