Closing the loop for engineering plastic waste using advanced physical recycling methods

Norbert Fraunholcz

Engineering plastics (e.g., ABS, PC and PMMA) have superior mechanical properties, such as strength and gloss. Therefore, they are primarily used in high-end products, such as electrical and electronic (E&E) devices and passenger cars. When it comes to end-of-life solutions, closed-loop recycling is the only sustainable option for this group of plastics. This is mainly due to a lack of alternative product applications to absorb lower-grade recycled material in quantity. In turn, closed-loop recycling implies very high quality requirements on the recycled material to replace virgin resins.

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What is chemical recycling / pyrolysis?

Chemical recycling today often refers to technologies that can be classed depending on the level at which they break down the plastic waste. Concretely, the technologies can be divided into 3 types:

  • Solvent-based purification. Comprises technologies that go down to the polymer stage. They are capable of decontaminating the plastic but cannot address its degradation. They work only with monostreams (PVC, PS, PE, PP).
  • Chemical depolymerisation. Chemical process which turns the plastics back into their monomers. Allows for decontamination but not addressing degradation. Only works with monostreams (PET, PU, PA, PLA, PC, PHA, PEF).
  • Thermal depolymerisation and cracking (pyrolysis and gasification) are energy-intensive processes which turn the polymers back into simpler molecules. They are capable of decontaminating polymers and, by bringing plastic back to its original building blocks, addressing the degradation of the material. These technologies can deal with more than one monomer at a time and are also capable of producing fuels. This raises the need for strict regulatory controls to prevent plastic being turned into fuel in lieu of recycling.
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