Greenhouse Gas Emission Reduction Potential of Chemical Recycling of Polyethylene Terephthalate into Plasticizers

This study evaluates the environmental performance of a plasticizer process as an alternative to conventional recycling methods. The process chemically recycles polyethylene terephthalate (PET) into dioctyl terephthalate, a non-phthalate plasticizer, using 2-ethyl-1-hexanol (EH). Unlike traditional processes that regenerate PET, this approach offers an open-loop recycling pathway. A process simulation-based life cycle assessment (LCA) was conducted to quantify cradle-to-gate greenhouse gas (GHG) emissions and to compare them with those of glycolysis, methanolysis, and enzymatic hydrolysis. The plasticizer process achieved GHG emissions of −0.88 t-CO2-eq per ton of treated PET flakes, which were substantially lower than those from methanolysis and slightly lower than those from glycolysis. A PET material flow analysis for Japan in 2023 further revealed that introducing the plasticizer process, alone or in combination with glycolysis, could reduce GHG emissions by up to 0.98 Mt-CO2-eq/year while supporting the domestic plasticizer supply. A multicategory LCA indicated that the plasticizer process provided the greatest reductions in resource depletion. However, it exhibited higher burdens in terms of human carcinogenic toxicity, aquatic ecotoxicity, and terrestrial ecotoxicity. These findings indicate that the plasticizer process is a viable open-loop recycling route that complements closed-loop methods and supports sustainable material circularity.