Environmental performance comparison of bioplastics and petrochemical plastics: A review of life cycle assessment (LCA) methodological decisions

There is currently a shift from petrochemical to bio-based plastics (bioplastics). The application of comprehensive and appropriately designed LCA studies are imperative to provide clear evidence on the comparative sustainability of bioplastics. This review explores the growing collective of LCA studies that compare the environmental footprints of specific bioplastics against those of petrochemical plastics. 44 relevant studies published between 2011 and 2020 were reviewed to explore important methodological choices regarding impact category selection, inventory completeness (e.g. inclusion of additives), boundary definition (e.g. inclusion of land-use change impacts), representation of biogenic carbon, choice of end-of-life scenarios, type of LCA, and the application of uncertainty analysis. Good practice examples facilitated identification of common gaps and weaknesses in LCA studies applied to benchmark bioplastics against petrochemical plastics. Many studies did not provide a holistic picture of the environmental impacts of bioplastic products, thereby potentially supporting misleading conclusions. For comprehensive evaluation of bioplastic sustainability, we recommend that LCA practitioners: embrace more detailed and transparent reporting of LCI data within plastic LCA studies; adopt a comprehensive impact assessment methodology pertaining to all priority environmental challenges; incorporate multiple plastic use cycles within functional unit definition and system boundaries where plastics can be recycled; include additives in life cycle inventories unless there is clear evidence that they contribute <1% to all impact categories; apply biogenic carbon storage credits only to long-term carbon sinks; account for (indirect) land-use change arising from feedstock cultivation; prospectively consider realistic scenarios of deployment and end-of-life, preferably within a consequential LCA framework.