CAREER: Modeling, Optimization, and Equilibrium Formulations for the Analysis and Design of Circular Economy Networks

Carnegie Mellon University, Pittsburgh PA

Investigators

Abstract

The current extract-make-use-dispose paradigm throughout product supply chains has enormous environmental and socioeconomic impacts, including climate change, biodiversity loss, depletion of natural resources, and pollution. Policymakers and industry practitioners support transitioning to Circular Economies (CEs) to solve these challenges. CEs aim to re-design current processing consumption practices to eliminate waste and pollution, circulate products and materials at their highest value, and regenerate nature. Although conceptually simple, the development of CE networks is hindered by the lack of scientific guidance on implementing and evaluating the effectiveness of CE initiatives. This CAREER project aims to advance the state of the art in designing and assessing CEs by developing modeling, optimization, and equilibrium formulations to analyze and design CE initiatives and networks. The proposed research will allow researchers to engineer CE strategies to accelerate the development of value chains that consume fewer new resources and produce less pollution. The proposed study also advances the use of game theory in process systems engineering. The results of this research will be incorporated into undergraduate and graduate-level project-based process design courses at Carnegie Mellon University to promote circularity and sustainability thinking in future scientists and engineers. Outreach activities are planned for a K-12 audience and include (i) writing articles for specialized STEM-oriented children’s journals and (ii) two hands-on workshops focusing on the concepts of circularity and sustainability in process design as well as the use of computers for chemical process design and optimization. To develop and test the mathematical tools needed to create Circular Economies (CEs), this project is divided into three Research Objectives. In the first, mathematical models for different CE initiatives will be developed, such as those that can be used to extend the life of goods and materials and those that exploit post-use processes. These models will be used to construct prototypical multi-agent CE networks, where each agent adopts a strategy consisting of one or more CE initiatives. Traditional (mathematical programming) optimization of these networks will be pursued from a multi-agent perspective to find trade-offs between their strategies. These results will be used to engineer circularity indicators so that agents benefit from each other’s strategies. In the second objective, individual agents will be treated as autonomous entities that base their decision-making in a decentralized manner. Game theory provides the framework for the formal analysis of these networks of agents. The Nash equilibria of the prototypical networks will be studied under non-cooperative simultaneous and sequential games. The difference between the Nash equilibrium solutions and the network-optimal solutions will be quantified by comparing the relative circularity efficiency of the two. The third objective involves the application of the theory developed under the first two objectives to design two CE networks, one involving the recovery and reuse of polyethylene terephthalate (PET) plastic bottle waste and the second examining CEs relevant to the recovery of rare earth (critical) minerals from end-of-life products. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.