(398d) Dynamic Systems Analysis of PET and Polyolefin Plastic Supply Chains in Circular Economy

Polyethylene terephthalate (PET, resin code #1), and polyolefin plastics such as High Density Polyethylene (HDPE, resin code #2), (Linear) Low Density Polyethylene ((L)LDPE, resin code #4), and Polypropylene (PP, resin code #5) have become an integral part of our day-to-day life owing to their low cost and excellent material properties suitable for multiple applications in several manufacturing industries. High consumption and production of these plastics with low collection rates has led to a global plastic waste crisis. Unfortunately, the plastics supply chains globally, and in the U.S., are highly dependent on fossil resources leading to high greenhouse gas (GHG) emissions and consumption of energy. In the U.S., PET and polyolefin plastic waste accounts for ~80% of the total plastic waste produced, most of which is currently being landfilled (77%), incinerated with energy recovery (16%), and with the remainder collected for sorting and recycling (7%). These mostly linear supply chains in the U.S. released 101 MMT CO₂-eq and consumed 3,248 PJ of energy in 2019, which accounted for 1.5% of the total U.S. GHG emissions and 3.1% of total energy consumed in the U.S.¹

To break this linearity of plastic supply chains, emerging chemical recycling technologies have been proposed to be a part of this solution to implement a circular economy for plastics. The sustainability of this transition from linear to circular economy is not well understood. In this work, we combine multiple systems analysis tools^2,3 such as material flow analysis, process simulation, life cycle analysis, technoeconomic analysis, transportation logistics and system optimization tools to look at the effect of incorporating a circular economy in the U.S. plastic supply chains for these plastics. In a preliminary application of this systems analysis model to U.S. PET bottles and packaging supply chain, the optimum material flow through mechanical and chemical recycling (including dissolution/purification, glycolysis, methanolysis, and enzymatic depolymerization) resulted in up to a 37% reduction in greenhouse gas emissions and 47% reduction in energy and a circularity metric of 0.8. This presentation extends this preliminary analysis to U.S. HDPE, LDPE, LLDPE, and PP plastics supply chains.

References

1. Chaudhari, U.S., Johnson, A.T., Reck, B.K., Handler, R.M., Thompson, V.S., Hartley, D.S., Young, W., Watkins, D. and Shonnard, D., 2022. Material Flow Analysis and Life Cycle Assessment of Polyethylene Terephthalate and Polyolefin Plastics Supply Chains in the United States. ACS Sustainable Chemistry & Engineering, 10(39), pp.13145-13155.

2. Chaudhari, U.S., Lin, Y., Thompson, V.S., Handler, R.M., Pearce, J.M., Caneba, G., Muhuri, P., Watkins, D. and Shonnard, D.R., 2021. Systems analysis approach to polyethylene terephthalate and olefin plastics supply chains in the circular economy: A review of data sets and models. ACS Sustainable Chemistry & Engineering, 9(22), pp.7403-7421.

3. Shonnard, D., Tipaldo, E., Thompson, V., Pearce, J., Caneba, G. and Handler, R., 2019. Systems analysis for PET and olefin polymers in a circular economy. Procedia CIRP, 80, pp.602-606.