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A Circular Economy Sustainability Analysis Framework for Plastics: Application for Polyethylene Terephthalate (PET)


Gracida-Alvarez, Ulises; Xu, Hui; Benavides, P.; Wang, Michael; Hawkins, Troy


The establishment of the circular economy (CE) for plastics aims to reduce material losses anddependence on virgin materials; however, this practice does not necessarily imply reduction oflife-cycle impacts. In this study, a CE sustainability analysis framework combining life-cycleassessment (LCA) and material flow analysis (MFA) was developed to simultaneously evaluatethe life-cycle impacts and circularity metrics of implementing different CE strategies ofproduction of plastic packaging, using polyethylene terephthalate (PET) bottles as an example.The strategies included increasing the recycling rate of PET bottles and integrating of twochemical recycling technologies in industrial development: enzymatic hydrolysis andmethanolysis. The energy use of enzymatic hydrolysis and methanolysis was estimated to be 60and 40 MJ/kg PET, respectively, while the two technologies accounted for greenhouse gas(GHG) emissions of 3.0 and 2.1 kg CO2 e/kg PET, respectively. The analysis at the system leveldemonstrated that compared to the current practice, relying on 97% virgin PET resin, the jointimplementation of these strategies generated similar GHG emissions (33.4 g CO2 e/bottle) butreduced virgin material use and solid waste generation by 56% and 64%, respectively. Based onpresent technology development, increasing the share of mechanically recycled resin in bottle manufacturing and using a decarbonized electricity grid resulted in 14% and 6% lower GHGemissions, respectively, than the current supply chain.