Life cycle assessment as a tool to help avoid misconceptions around the environmental performance of plastics and their alternatives

Life cycle assessment (LCA) is a decision-making tool that allows for a comprehensive assessment of environmental impacts induced by products, processes, or services. Using the outputs of this tool, industries have been able to identify key processes in their supply chains and improve the environmental performance of products they commercialize. Yet, LCA does not yet allow for considering the consequences of (micro)plastic waste leaked into the environment. This limits the application of LCA as a decision-making tool in the case of plastic products since the potential environmental benefits of decisions based on plastic bans or substitution initiatives cannot be properly assessed and may sometimes lead to unintended consequences on ecosystems and/or human health. The international working group MarILCA (Marine Impacts in LCA) was founded in 2018 to address this gap. Recent publications contributing to this taskforce’s mandate have provided a methodology for quantifying the potential impacts of aquatic (marine and freshwater) microplastic emissions. These emissions can come from primary sources (e.g. pellets used for the production of plastics) or secondary sources (fragmentation of larger plastic objects into microplastics). The methodology comprises fate factors which assess the distribution and longevity of microplastics in the aquatic environment, and exposure and effect factors which address the ingestion of microplastics and subsequent adverse effects on aquatic organisms. The fate, exposure and effect factors are combined to deliver so-called characterization factors for eleven different polymers (EPS, PS, PP, HDPE, LDPE, PET, PVC, PLA, PHA, PA, TRWP), three shapes (sphere/microbead, cylinder/microfiber, microplastic film fragments) and five sizes (1, 10, 100, 1000, 5000 µm). These characterization factors link microplastic emissions with the potential damage they cause to ecosystems and biodiversity. Several indicators are developed to be compatible with different existing and upcoming life cycle impact assessment methodologies. The set of developed metrics are then tested in three food packaging case studies within a recent UNEP report on the topic: (1) To-go food containers used in Canada. (2) Fresh-cut produce (lettuce) bags used in Italy. (3) Crates for fruit and vegetable transportation used in Spain. The magnitude of the potential impacts from microplastic emissions is compared to other LCA impact categories. In most cases, climate change impacts predominate and are several orders of magnitude higher than the impacts from microplastic emissions. First results also highlight the fact that high-density microplastics tend to show lower impacts on aquatic ecosystems than lower-density microplastics. This is due to the fact that high-density polymers sediment quickly, which lowers the likelihood of species living in the water column ingesting them. Preliminary results show a more nuanced – but consistent - outcome when also accounting for impacts potentially occurring in the sediments. These findings show that plastic alternatives in single-use items do not necessarily represent an environmental benefit and the that the complete life cycle of products needs to be considered when assessing their environmental performance or setting forward plastic-oriented policies.