A tandem enzymatic-electro upcycling of waste PET into high-value chemicals: Process development and sustainability assessment for circular economy transition

Achieving a circular economy for plastics is crucial; however, this transition is hindered by the limited economic feasibility of the current chemical recycling methods. To address this challenge, we propose a novel tandem enzymatic-electro conversion process to upcycle waste polyethylene terephthalate (PET) into recycled terephthalic acid (r-TPA) and valuable by-products. Two conversion pathways were designed, producing glycolic acid or formic acid as by-products and combining them with four different separation processes, resulting in eight different process configurations. Detailed techno-economic and environmental assessments identified the glycolic acid production pathway with reverse osmosis as the optimal configuration (EEG-RO process), achieving a unit production cost of 1.27 $/kgTPA. The net CO_2eq emission was calculated as 1.72 kgCO_2eq/kgTPA, which is lower than that of fossil-based TPA production. Sensitivity analysis underscored the importance of PET flake costs, by-product credits, and technological advancements, while uncertainty analysis revealed economic fluctuations arising from cost uncertainties. Furthermore, our sustainability assessment quantitatively analyzes the environmental benefits derived from integrating r-TPA into PET production and underscores the role of supportive policies that enhance the economic viability of the PET recycling system. This study provides valuable insights for designing sustainable PET recycling systems and contributes to accelerating the global transition toward a circular PET economy.