Integrated process modelling, optimization, and sustainability assessment for Eucalyptus leaves valorization via extraction technologies

The valorization of Eucalyptus leaves as lignocellulosic residues contributes to circular bioeconomy targets. Identifying the optimal extraction technology requires balancing complex thermodynamic, economic, and environmental trade-offs. This study systematically evaluates four extraction pathways integrated within a biorefinery framework: steam distillation (SD), hydroalcoholic extraction (EtOH-S), supercritical CO 2 ( SC − CO 2 ), and supercritical CO 2 with ethanol co-solvent ( SC − CO 2 –EtOH ). The assessment employs a hybrid modeling approach combining process simulation, mathematical formulations to represent non-ideal system behaviors, and optimization, followed by techno-economic and life cycle assessments. Results show the EtOH-S route is the most economically robust, achieving a 25% internal rate of return at a selling price of $5/kg (25% of the essential oil benchmark) due to its superior extraction yield, while the SC − CO 2 –EtOH route is economically unfeasible for this ($48/kg required) application. Conversely, SD and SC-CO₂ remain viable for high-purity niche markets. Under a baseline mass-based functional unit ( 1 kg extract), EtOH-S also dominates environmentally as its high yield dilutes upstream burdens, while SD exhibits the highest land-use impacts due to low extraction efficiency and high feedstock intensity. However, using a functionality-based functional unit ( 1 kg active essential oil equivalent) drastically shifts these dynamics. Due to its low target-compound purity, EtOH-S incurs massive inventory and processing scaling penalties while SD demonstrates the most balanced, practical, and eco-efficient option while operating safely within market price boundaries. Overall, EtOH-S provides the most balanced solution for bulk crude chemical valorization, whereas specialized techniques like SD are required when the biorefinery objective targets high-purity bioactive isolates.