Comparative Study of LCA Approaches and Circularity Metrics in Recycled Polyethylene Systems

Plastics such as polyethylene (PE) are increasingly scrutinized for their environmental impacts, with recycling promoted as a key mitigation strategy within a circular economy. However, assessing the true environmental benefits of recycling remains methodologically challenging. This study compares different life cycle assessment (LCA) calculation approaches, namely, the cut-off, system expansion, waste valuation, and the circular footprint formula. These approaches are applied to a hypothetical but realistic case of polyethylene bag production, including virgin, once-recycled, and twice-recycled products. In addition, complementary circularity metrics, the material circularity indicator (MCI) and the circularity index (CI), are evaluated for the same scenarios. The results show that calculated environmental impacts and circularity scores vary substantially depending on the chosen method. Even within a single recycling case, methodological choices lead to divergent outcomes. Such variability may complicate communication among chemists, engineers, suppliers, and policymakers and undermine effective decision-making for polymer and plastic production. While LCA provides detailed and structured insights, its methodological complexity often limits accessibility and transparency. In contrast, MCI and CI offer simpler and more communicable perspectives on circularity but overlook important environmental dimensions. Overall, these findings highlight the need for clearer and more consistent assessment frameworks that balance methodological complexity with usability.