In the present work the influence of a non-ideal separation step of a supercritical fluid extraction (SFE) unit was studied; the solvent used was carbon dioxide. The behavior of clove bud (Eugenia caryophyllus), vetiver grass (Vetiveria zizanioides), and fennel (Foeniculum vulgare) was analyzed. The starting point was a previous study on the same subject, which considered that no solute is lost in the vapor phase and a fixed fraction of 2% of the CO2 is lost within the heavy phase. The flash separation step was simulated using the SuperPro Designs 6.0 (R) Software, which calculates the phase equilibrium that occurs during the separation step using the Peng-Robinson equation of state. Experimental data for extraction kinetics from vetiver grass were obtained at 313 K and 20 MPa. Phase equilibria for CO2/vetiver extract were measured at pressures from 7.5 to 30 MPa and temperatures of 303.2, 318.2 and 333.2 K; CO2 weight fraction varied from 0. 1 to 0.99. The flash tank experimental data was obtained for fennel at 4 MPa and 293 K; the resulting anethole loss was 1.45%. The costs of manufacturing (COM) of the SFE extracts were determined according to Turton et al. using Tecanalysis v 1.0; the influence of the non-ideal flash separation step on COM was studied for clove buds. (C) 2007 Elsevier B.V. All rights reserved.