Date of Award
2024
Document Type
Campus Access Dissertation
Degree Name
Doctor of Philosophy in Chemical Engineering (PhD)
Administrative Home Department
Department of Chemical Engineering
Advisor 1
David R. Shonnard
Committee Member 1
Rebecca G. Ong
Committee Member 2
Robert M. Handler
Committee Member 3
David W. Watkins
Abstract
The existing polyethylene terephthalate (PET) and polyolefins (PO) supply chains follow a fossil-based linear economy, leading to high greenhouse gas emissions (GHG) and energy consumption. A transition towards “closed-loop” circular economy of plastics via emerging chemical or advanced recycling technologies has been recognized as one of the important solutions by reducing the reliance on fossil-based plastics. However, the sustainability of this linear-to-circular transition in PET and PO supply chains is not well understood, further requiring a systems analysis to holistically understand and quantify the sustainability implications.
The objective of this dissertation was to employ a novel systems analysis framework to evaluate and compare the sustainability of existing and emerging PET and PO supply chains, including end-of-life (EOL) processes. Various tools like material flow analysis (MFA), chemical engineering process simulations, life cycle assessment (LCA), techno-economic analysis (TEA), socio-economic analysis, transportation and logistics modelling, and system optimization were applied to achieve this objective.
MFA and LCA of existing 2019 U.S. PET and PO plastics supply chains revealed that they account for 1.5% and 3.1% of the total U.S. GHG emissions and energy consumption, respectively. Applications of process simulations with LCA and TEA tools to emerging advanced recycling processes revealed that the solvent-based dissolution precipitation processes for PET and liquid-fed pyrolysis process for polyethylene films were environmentally and economically feasible, compared to their relevant fossil alternatives, with some exceptions.
Finally, a systems analysis optimization model for U.S. PET packaging supply chains evaluated environmental and socio-economic impacts and trade-offs of linear-to-circular transition of PET packaging material. An optimum PET packaging system showed a shift towards emerging EOL circular advanced recycling processes, which resulted in higher employment, wages, recycled content, and systems circularity. An environmentally optimum PET packaging system showed a circularity of 77% resulting in GHG emissions and energy savings of 31% and 37%, respectively, compared to the linear PET packaging system, but showed a loss of 5% in total systems revenues. Overall, our systems analysis results show that a transition from a linear to a circular economy for PET packaging will improve sustainability, however there is a trade-off between environmental impacts and system revenues. A novel “decision diagram” was generated to display the Pareto trade-off optimum results in a way that aids in decision-making and may lead to better policies and investments.
Recommended Citation
Chaudhari, Utkarsh Shailesh, "SUSTAINABILITY ASSESSMENT OF CIRCULAR ECONOMY IN PET AND POLYOLEFIN PLASTICS SUPPLY CHAINS IN THE U.S. AND MICHIGAN: A SYSTEMS ANALYSIS APPROACH", Campus Access Dissertation, Michigan Technological University, 2024.