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.