(117ay) A Dynamic Material Flow Analysis of the Global Demand of Polymers

Introduction

Polymers are ubiquitous thanks to their low-cost and versatile properties. The production of plastics has increased from 1.7 Mt in 1950 to 368 Mt in 2019¹. The wide application of polymers has led to a series of environmental issues, including greenhouse gas (GHG) emissions and ocean pollutions. The life cycle of polymers accounts for 4.5% of the global GHG emissions².

In order to reduce the environmental impact of polymers, capping the production and consumption of polymers is proposed by researchers^1,3–5. Circular economy is also proposed to reduce the waste of polymers^6,7 and reduce production. However, a global model to quantify the practical limitation of circular economy and demand reduction is not available yet.

Material flow analysis is widely adopted to investigate the global and regional mass flow of polymers⁸. However, a holistic breakdown of polymer’s mass flow in each world region is missing. Few studies forecasted the future demand of polymers by extrapolating the historical consumption^8–10, but the accuracy of regional demand of polymers is disabled or compromised by the lack of regional granular data to fit the model, e.g., production and trade of polymer raw materials and products with embedded polymers.

Method

To bridge the gap, the study adopts the dynamic material flow analysis model to quantify the productions, trades, and consumptions of 11 groups of polymers (LDPE, LLDPE, HDPE, PP, PS, PVC, PET, PU, rubber, fibres, and other plastics) and 1205 products made of polymers in eight world regions from 1978 to 2020, and fits the historical trend in order to project the future regional and global demands of polymers in different scenarios.

Results and discussion

Among the 8.86 Gt cumulative consumption of polymers, 2.41 Gt polymers are still in use in 2020. Among all the regions, Northeast Asia ranks the first, covering 28% of the total stock in-use, and North America, Europe and South Asia are responsible for 20%, 19% and 10% of the total stock in-use, respectively.

In terms of application sectors, 51% of the in-use stocks takes place in building and construction, due to the long average residence time of 35 years. 19% plastics are used in the transportation sector. The other sectors are responsible for less than 10% of the total in-use stocks.

The stocks in-use per capita in Oceania and North America are 1.28 t/cap and 1.27 t/cap, respectively. The average stock in-use in Europe is 840 kg/cap, and all other regions have less than 400 kg/cap. As the regional GDP per capita increases, the regional stock in-use per capita also increases, which is the basis for the projection of future demands of polymers in different scenarios.

The results will show how much GHG emissions can be reduced globally by different changes in recycling rate across eight different world regions modelled.

References

1. Bauer, F. et al. One Earth 5, 361–376 (2022).

2. Cabernard, L., et al. Nat Sustain 5, 139–148 (2022).

3. Simon, N. et al. Science 373, 43–47 (2021).

4. Bergmann, M. et al. Science 376, 469–470 (2022).

5. Syberg, K. Nature 611, S6 (2022).

6. Kakadellis, S., et al. Science 373, 49–50 (2021).

7. Meys, R., et al. Science 76, 71–76 (2021).

8. Geyer, R., et al. Sci Adv 3, 25–29 (2017).

9. OECD. Global Plastics Outlook: Policy Scenarios to 2060. (2022)

10. Stegmann, P., et al. Nature 612, 272–276 (2022).