Abstract
An integrated multiproduct facility for the valorization of apple pomace in the green production of high value-added chemicals such as phenolic compounds and pectin, bioethanol, as well as apple juice, was optimally designed. The process includes green extraction technologies relying on subcritical water extraction and ethanol produced on-site through fermentation of residues. Two scenarios were evaluated: one based on purchasing the ethanol and another with on-site ethanol production. The units of the process were modeled using first principles. The process superstructure was formulated as a mixed-integer nonlinear programming problem, solved by decomposition. Investment and production costs of both alternatives were similar, with unit production requirements ranging from 1.09 €/L to 1.13 €/L. The discounted payback periods were 6.7 years and 6.4 years for the on-site ethanol production and purchased ethanol scenarios, respectively, while the internal rates of return were 36.4 and 37.8% for both processes, respectively. Both scenarios showed economic profitability with higher returns under the purchased ethanol scenario, but the on-site production scenario allowed waste reduction, self-sufficiency and ethanol reuse. A green extraction process based on subcritical water for the pectin extraction and the solvent recycling avoided the use of conventional acids and promoted the circular economy. The findings of this project demonstrated the potential of apple pomace as a valuable feedstock for integrated biorefinery applications in the agri-food sector.