Prospective life cycle assessment of poly (ethylene terephthalate) upcycling via chemoselective depolymerization

Abstract

Chemical upcycling of non-biodegradable polymers can shift the current linear plastic economy towards circular patterns. This work studies the environmental impacts of poly(ethylene terephthalate) (PET) upcycling given its extensive use in packaging, textile and automotive industries. A prospective gate-to-gate life cycle assessment is applied to five PET upcycling processes representative of common chemoselective depolymerization strategies. Laboratory-scale upcycling is scaled-up for processes depolymerizing 1 kg of post-consumer PET. With a global warming potential from 4.3 to 5.8 kg·CO2 equiv. per kg of upcycled postconsumer PET, Glycolysis-PG using propylene glycol and a manganese acetate catalyst, Aminolysis and Hydrogenolysis processes bear the lowest global warming potential. On the contrary, the Glycolysis-EG process that uses ethylene glycol (EG) and a protic ionic salt catalyst has the largest global warming potential of 91.3 kg·CO2 equiv. per kilo of PET. These differences are driven by variabilities in the energy and solvent consumption, and the presence of catalysts. Two sensitivity analyses focused on EG recirculation and ethylene carbonate production are performed to explore environmentally friendlier processes. Overall, this work highlights the environmental hotspots during postconsumer PET upcycling, guiding the implementation of sustainable approaches in polymer recycling.