Sustainable valorization of agro-industrial residues represents a key strategy in advancing circular economy principles. In this study, residual eucalyptus leaves were evaluated as feedstock for essential oil extraction using four different separation technologies: (i) supercritical CO₂ extraction (SFE), (ii) SFE with ethanol as a co-solvent (SFE-EtOH), (iii) steam distillation (SD), and (iv) ethanol-based solvent extraction (EtOH-SE). Each method was analyzed in terms of extraction efficiency and energy consumption. Mathematical optimization models were developed in the GAMS environment to identify optimal operating conditions. These models integrated key variables such as oil yield, raw material usage, and auxiliary facility requirements. Subsequently, a comprehensive techno-economic analysis was carried out to estimate capital investment and operational expenses.

The results revealed that steam distillation offered the most favorable performance-to-cost ratio, achieving an essential oil yield of 2.06%, with an estimated annual energy demand of −16,833.98 GWh, operating costs of approximately USD 4.16 million, and a capital investment of around USD 878,625 (annualized). While supercritical fluid extraction methods demonstrated higher selectivity compared to steam-based extraction, their operational complexity and elevated energy demands limited their economic efficiency under the evaluated conditions. This study underscores the importance of integrating advanced process modeling tools with rigorous techno-economic assessments to support informed decision-making in the design and optimization of biomass valorization strategies.