Multi-Objective approach to the Circular Economy paradigm in the chemical process industry

Abstract

This thesis deals with a multi-objective approach to promote the circular economy in the context of chemical recycling of plastic waste. The main objective of this thesis was to develop a multi-objective decision making tool that could be integrated into the iSMA framework developed by Pacheco-Lopez et al. (2023) to fill an identified gap. The literature review highlighted the growing importance of sustainable plastic waste management, describing current waste management methods and their limitations, as well as the potential of chemical recycling to improve this situation. Chemical recycling, in particular pyrolysis, offers a promising way to convert plastic waste into valuable resources, although challenges remain in terms of efficiency and environmental impact. The iSMA framework generates Pareto optimal solutions for different recycling paths, but a tool was needed to objectively select the best options. This tool, developed in Python, implements the multi-objective optimization methods TOPSIS and PROMETHEE, and includes a sensitivity analysis module to assess the stability and robustness of alternatives in the face of uncertainty in the weighting of criteria. The results obtained show that the tool is functional and able to provide relevant rankings, although depending on the quality and completeness of the initial data. Future prospects include extending the tool to other areas of environmental sustainability, integrating new optimization methods, and specifying criteria weightings guided by local sustainability policies.