Solvent based dissolution–precipitation of waste polyethylene terephthalate: economic and environmental performance metrics

Abstract

Polyethylene terephthalate (PET) is one of the highest production volume polymer resins, with wide ranging applications in consumer packaging. Due to challenges in closed-loop recycling of PET, recycle rates in the U.S. are low (13% compared to PET resin converted), with the vast majority landfilled or leaked to the environment at the end of life. Solvent based dissolution and precipitation recycling technology has the potential to achieve closed-loop recycling of PET in food packaging and help achieve a circular economy for plastics. However, this technology is still in the early stages of development and there is an urgent need to understand the economic costs and environmental impacts to select promising process pathways. In this study, we analyze three precipitation process configurations for production of high-quality PET resin from post-consumer waste PET using gamma-valerolactone as the solvent: (i) anti-solvent using water, (ii) solvent evaporation, and (iii) cooling of the dissolved polymer solution. The process conditions and yields were obtained from literature sources, and process simulation was employed to estimate energy consumption and process economics. Using standard chemical engineering techno-economic analysis (TEA) assumptions and current market prices, the anti-solvent process was found to be the least profitable compared to evaporation or cooling precipitation methods, although all exhibited positive net present values. The environmental life cycle assessment (LCA) results revealed that the anti-solvent process produced 60% higher greenhouse gas (GHG) emissions compared to fossil virgin PET, but the evaporation and cooling processes reduced GHG emissions by about 50%. The sensitivity of the results to process and recycling system parameters were thoroughly investigated.