Circular Quality of Polymers: Test-Based Evidence for Comparison of Bio-Based and Fossil-Based Polymers

The factual circularity of materials needs utilization of materials that keep their quality properties after going through recycling to minimize the inflow of virgin materials in the technosphere. Within the PEF methodology, and based on the economic model approach, the European Commission provides default parameters for the quality changes of the polymers after recycling, but solely for some fossil-based polymers. This study provides a test-based example for the calculation of technical substitutability for 2 fossil-based polymers (HDPE and PET) and 2 bio-based polymers (PLA and PHB) based on mechanical, processing, and optical properties. The results show that the economic substitutability method gives very different results compared to those obtained by considering real technical quality changes of the polymers in multiple-cycle recycling. HDPE proved to have superior circular properties compared to any other polymer under research. In addition, the recent practice of substituting fossil-based with bio-based polymers will need to be re-evaluated after additional research related to the quality change of bio-based polymers in recycling. The results showed the important limitations of the economic substitutability method and a strong need for a harmonized testing method for the calculation of quality degradation of all types of polymers in recycling.