Flame retardants are added to plastics in passenger vehicles to save lives. However, their releases can, in some cases, be accompanied by undesired impacts to human health and the environment. In the context of a transition to a Circular Economy, it is therefore important to keep track of the flow of flame retardants in passenger vehicle plastics. This study focuses on the flame retardant Decabromodiphenyl Ether (decaBDE), whose use in plastics has become banned in recent years. Through a static layered material flow analysis, the flows of plastics and decaBDE are quantified for passenger vehicles in The Netherlands in 2019. Afterwards, six scenarios are created outlining different possible approaches to plastics and flame retardants: Reference, Recycling, Incineration, Less Cars, No DecaBDE Ban, and No Substitution. The first four of these scenarios acknowledge the progressive phasing out of decaBDE and include the use of an additional flame retardant, triphenyl phosphate (TPP). At the hands of a dynamic layered material flow analysis, the stocks and flows of plastics, decaBDE, and TPP, are calculated from 1980 until 2050. The emissions calculated in this step, as well as the flow of flame retardant directed to incineration, are then used to evaluate the environmental performance of each scenario by means of a life cycle impact assessment. The results from the life cycle impact assessment show that, from a midpoint perspective, no scenario is a clear winner. Moreover, the lack of characterization factors for some categories makes it difficult to assess the reliability of the results. From an endpoint perspective, the best performing scenarios are the TPP-free scenarios No DecaBDE Ban and No Substitution. This is because TPP is shown to have a significant influence in the global warming impacts. From the TPP-using scenarios, the best performing one is the Recycling scenario, which shows the advantages of promoting recycling strategies in the sector. Overall, TPP-using scenarios perform worse environmentally than decaBDE-using scenarios. According to the findings in this study, some of the key elements that could smooth the transition to a sustainable and healthy circular economy are policy measures that incentivize plastic recycling in the automotive industry and the use of less cars per capita. Further research is needed on the environmental performance of less harmful flame retardant alternatives to decaBDE. The methodology used in this study could serve as a framework in future research for other type of product applications as it is useful to evaluate different policies involving chemicals or additives embedded in materials over time. With this methodology, a link is made between the product, material, and chemical layers, able to bridge potential gaps in the often data scarce chemical layer.

In 2050, over 80% of the worldwide electricity demand is expected to be supplied by renewables. The mismatch between supply and demand resulting from these intermittent energy sources and the physical limits of existing electrical grids are challenges in this transition, for which batteries are part of the solution. Therefore, there is a renewed interest to develop advanced and environmentally sound batteries, which requires assessing their environmental impacts by means of life cycle assessment (LCA). However, in current LCA studies the use phase is insufficiently addressed and even oftentimes excluded due to complexity. The aim of this research was to gain insight into current approaches of modelling the use phase in existing LCA and footprinting studies to provide LCA practitioners with recommendations and improved approaches. A literature review was performed which included 26 papers, Annex II of Regulation (EU) No 2019/1020 and the PEFCRs for High Specific Rechargeable Batteries for Mobile Applications. Next to storing renewable energy, batteries can serve different services, also called applications. The implications of incorporating the utilisation of a battery for multiple applications simultaneously, i.e., value stacking, in modelling the use phase are discussed in a qualitative way, since this is emerging as a practical and economically beneficial operational strategy. Finally, the relative effect on a battery’s life cycle impact assessment (LCIA) scores of four issues identified in the literature review is analysed in an illustrative case study about an organic redox flow battery (ORFB). It appears that many studies do not provide clear information on how the functional unit (FU) is specified, which application(s) the battery is utilised for, application characteristics, modelling assumptions including the electricity and battery inputs or complete LCI data. Overall, the degree of transparency of many battery LCA studies is mediocre which complicates judging the usefulness of results and should be improved to improve comparability and reproducibility for which recommendations are provided. Moreover, the interaction of battery parameters and application characteristics is captured in proposed modelling guidelines for the electricity and battery system input flows. Value stacking results in environmental benefits, particularly when a battery is used to store renewable electricity which is used to serve another application simultaneously. It seems only interesting for battery technologies with high cycle lives such as RFBs and some lithium-ion batteries because these offer the ability to increase battery utilisation without considerably decreasing the battery’s lifetime. To reach sustainability ambitions, battery applications leading to a reduction in environmental impacts should be promoted for which a general incentive policy is not appropriate. Such policy stimulates all battery applications, which could lead to small or even negative contributions to environmental impact reduction compared to the current situation. Even though this is a temporary transition problem, it could lead to an undesirable interim increase of environmental impacts during the transition. To this end, performing comparative assessments of applications that are expected to be served by batteries in the future, requiring the involvement of transmission network operators, and how these are served in the current situation are useful.