How accurate are LCAs for pyrolysis and gasification in the context of plastic waste management?

Pyrolysis and gasification are often presented in the life cycle assessment (LCA) literature as environmentally promising solutions for plastic waste management. However, the lack of validated large-scale inventory data and limited use of uncertainty/statistical analysis cast doubts on the findings. This study aims to investigate the validity of these conclusions by modelling LCA for pyrolysis (PYR) and gasification (GASI) using two data sources: Aspen-generated data (ASP) and aggregated literature data (LIT). The novelty of this study lies in applying uncertainty propagation tailored to each source, enabling systematic evaluation of result variability. Using a functional unit of 1 kg mixed polyolefin (MPO) waste treated, our results show that Aspen-based scenarios exhibit narrower uncertainty ranges than their literature-based counterparts. For instance, the variability in terms of global warming potential for PYRO (ASP) ranged from 0.751 to 1.53 kg CO 2 eq/kg MPO waste treated, whereas that of PYRO (LIT) ranged from 1.24 to 6.51 kg CO 2 eq/kg MPO waste treated. Similarly, GASI (ASP) had a more constrained 95 % confidence interval (from 2.56 to 4.97 kg CO 2 eq/kg MPO waste treated) compared to that of GASI (LIT), which spanned from 2.20 to 15.58 kg CO 2 eq/kg MPO waste treated. Other impact categories, including acidification, freshwater eutrophication, freshwater ecotoxicity, and resource depletion, also showed considerably varied results. These disparities largely stem from many underlying assumptions and simplification during Aspen modelling, leading to reduced number of variables. Conversely, literature-based LCA models are constrained by repeated reuse of data and by inconsistencies in system boundaries, which exacerbate result variability. These issues suggest that the consensus in support of chemical recycling rests on a narrower data foundation than often assumed. As such, we recommend that LCA findings be used as policy reference only when supported by robust case-specific data, and transparent uncertainty analysis. While these findings provide crucial perspective for stakeholders and decision-makers, it is important to note that the methodology applied in this study is limited by various practical factors, including simplification of Aspen modelling and LCA system boundaries, as well as inherent limitations related to data gathering protocol.