Enhancing the environmental performance of production processes is currently a major issue. To propose efficient processes both in terms of productivity and environmental impacts, it is necessary to develop multi-objective optimization tools. Such an approach was developed in this study for an ultrasound-assisted extraction process, aiming at val-orizing antioxidant polyphenols from downgraded beetroot seeds (agri-food by-product). Environmental impacts of the process (assessed using LCA), as well as classical productivity indicators (extraction yield, antioxidant activity of the extract, energy consumption) were all predicted in function of the varied process parameters (extraction time, solvent composition, solvent/beetroot seeds ratio, ultrasound power density). The proposed multi-criteria optimization tool allowed to predict optimal operating conditions in function of specific constraints, such as maximization of extraction yield and/or minimization of extraction time, energy consumption and/or environmental impacts. Maximal polyphenols concentration (2.8 g.L-1 GAE) and antioxidant activity (16.6 mM TEAC) were obtained after 120 min with 65% ethanol in the solvent, ultrasound power density of 667 W.L-1, and ratio of 5 mL.g-1. Ultrasounds assistance allowed extraction yield enhancement (up to 60%) of and process duration decrease (8 times), without degrading environmental performance. The original proposed methodology could easily be adapted for multi-criteria optimization of other processes. (c) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.