Additive inclusion in plastic life cycle assessments part I: Review of mechanical recycling studies

As the European Union transitions to the circular use of plastics, robust life cycle assessments are crucial in understanding and preparing for this new economy. Additives are essential to the production of all plastics but were reported as missing from life cycle assessments (LCAs) of plastic materials a decade ago. This study expands upon previous research by investigating if plastic additive impacts are now included in LCAs of recycled plastic materials or if they are still absent. In part I, we conduct a systematic literature review of 93 LCAs on plastics, including mechanical recycling pathways, and distinguish if plastic additive impacts are considered in (i) in-text discussions and (ii) the life cycle inventories (LCIs) of each study. We then compare the types of additive inclusion within the corpus to ascertain whether author knowledge or data availability dictates additive inclusion in plastic LCAs. We find that data disclosure and detailed discussions of specific additive impacts are missing across the corpus due to poor transparency in LCI disclosure or overly generic disclosures of additives. The lack of detailed and transparent discussions and disclosure indicates that additive impacts are missing from LCAs of recycled plastic materials, leading to incomplete analyses of their impacts. Until addressed, such a gap may lead to inaccurate or incomplete circular plastic material LCAs. In part II, we assess the quality of generic disclosures and explore how database quality and transparency have contributed to additive omissions in LCAs.