A framework for modular modelling of recycling process chains in life cycle assessment: concept and practical implementation for the case of post-consumer plastic packaging.

Recycling is one key strategy of the Circular Economy, especially for post-consumer plastic packaging. Life Cycle Assessment (LCA) has investigated this topic for a long time, however literature criticizes the modelling of recycling in LCA studies as incomplete and oversimplified, stating a gap between the variability of real-world practices of waste management and modelled scenarios. Consequently, Life Cycle Inventory (LCI) will have to draw more information from real-world investigations, which in turn requires a structured approach to compile data from different activity fields of waste management. We present a framework which enables the systematic modular modelling of recycling process chains, focussing on multi-material products or mixed waste, for which recycling comprehends multiple steps of material separation and processing. As key element, this framework introduces the term of Process Chain Sections (PCS), which specifies interfaces for data transfer between the fields of waste collection, material separation and material processing. As part of the framework, Material Flow Analysis (MFA) is included to identify material flows and processes within the system boundaries. The implementation in LCI is restricted to the assessment of the burdens of recycling process chains. We present the application of this framework both for studies on waste management systems and for product LCA, using the case of packaging waste in Germany. Results showcase how generic and individual datasets for PCS enable a congruent and efficient way for compiling variants of recycling process chains for different research questions. The framework supports comparability and transparency of LCI and may provide guidance for future standardization.