Towards circular plastics within planetary boundaries

The rapid growth of plastics production exacerbated the triple planetary crisis of habitat loss, plastic pollution and greenhouse gas (GHG) emissions. Circular strategies have been proposed for plastics to achieve net-zero GHG emissions. However, the implications of such circular strategies on absolute sustainability have not been examined on a planetary scale. This study links a bottom-up model covering both the production and end-of-life treatment of 90% of global plastics to the planetary boundaries framework. Here we show that even a circular, climate-optimal plastics industry combining current recycling technologies with biomass utilization transgresses sustainability thresholds by up to four times. However, improving recycling technologies and recycling rates up to at least 75% in combination with biomass and CO2 utilization in plastics production can lead to a scenario in which plastics comply with their assigned safe operating space in 2030. Although being the key to sustainability and in improving the unquantified effect of novel entities on the biosphere, even enhanced recycling cannot cope with the growth in plastics demand predicted until 2050. Therefore, achieving absolute sustainability of plastics requires a fundamental change in our methods of both producing and using plastics. The sustainability of the net-zero circular strategies of plastics has not been previously examined on a planetary scale. Linking a bottom-up model for the production and end-of-life treatment of plastics to the planetary boundaries framework, this study shows the need to scale up recycling and reconsider how we produce and use plastics.

Automated summary

The rapid growth of plastics production worsens the triple crisis of habitat loss, plastic pollution, and greenhouse gas emissions. Circular strategies to achieve net-zero GHG emissions have been proposed, but their implications for overall sustainability have not been studied on a global scale. This study links a comprehensive model of plastic production and end-of-life treatment to the planetary boundaries framework and finds that even a circular, climate-optimized plastics industry exceeds sustainability thresholds by up to four times. However, improving recycling technologies and rates, combined with biomass and CO2 utilization, can bring plastics into their safe operating space by 2030. Still, achieving absolute sustainability for plastics requires fundamental changes in production and use methods.