Life cycle assessment and circularity of polyethylene terephthalate bottles via closed and open loop recycling

Polyethylene terephthalate (PET) recycling is considered as one of the key approaches to achieving the circular economy (CE) of plastic waste. Bottle-to-Bottle and Bottle-to-Fiber recycling were assessed using Life Cycle Assessment (LCA) and Material Circularity Indicator (MCI). Three allocation methods (i.e., substitution, recycled content, and economic allocation) were used to deal with the recycling system. Producing bottle-grade PET resin and polyester fiber from PET bottle waste can reduce environmental impacts for most midpoint impact categories (e.g., 60% greenhouse gas emissions reduction and 85% fossil resource scarcity reduction). At the endpoint level, the damages to resources, ecosystem quality, and human health of the recycled PET bottles derived from Bottle-to-Bottle recycling were less than virgin PET bottles when using the substitution and recycled content methods. When using the economic allocation method, the final LCA findings highly depended on the recycled content used to produce the PET bottles. On the other hand, regardless of the allocation method used, recycled polyester fiber derived from Bottle-to-Fiber recycling caused less environmental damages than virgin polyester fiber. The MCI scores of Bottle-to-Bottle recycling in the baseline scenarios range between 0.20 and 0.31, whereas the MCI scores of the expected scenario in the future show a higher level of material circularity (0.55-0.60) as a result of 100% collection rate for recycling of PET bottles and the use of recycled PET as a feedstock. Therefore, higher collection rates and recycled content support Bottle-to-Bottle recycling. On the other hand, the MCI score of Bottle-to-Fiber recycling in the baseline scenario is 0.52. This high score resulted from the use of 100% recycled PET as a feedstock of polyester fiber. Recycling polyester fiber at the end-of-life could further increase the MCI to almost 0.7. However, to keep the materials at their highest quality and value, Bottle-to-Bottle recycling should be the preferred option.