Complementary roles for mechanical and solvent-based recycling in low-carbon, circular polypropylene

Area of Science:

• Materials Science
• Environmental Science
• Chemical Engineering

Background:

• Mechanical recycling of plastics like polypropylene leads to property degradation, limiting applications.
• Advanced recycling methods offer higher quality but often have a larger environmental footprint.
• Plastic waste streams typically require preprocessing, irrespective of the recycling pathway.

Purpose of the Study:

• To quantify the life-cycle greenhouse gas (GHG) implications of various plastic recycling strategies.
• To propose an integrated system combining mechanical and solvent-assisted recycling for polypropylene.
• To enhance recycling rates and meet demand for diverse product applications.

Main Methods:

• Life-cycle assessment to evaluate GHG emissions of different recycling scenarios.
• Processing of polypropylene from mixed-plastic bales through mechanical recycling.
• Upgrading of a fraction of mechanically recycled polypropylene using solvent-assisted recycling.

Main Results:

• Mechanically recycled rigid polypropylene reduces life-cycle GHG emissions by 80% compared to virgin material.
• Upgraded polypropylene via solvent-assisted recycling achieves 30% GHG savings.
• The proposed integrated system can boost overall recycling rates and material quality.

Conclusions:

• A combined mechanical and solvent-assisted recycling approach is effective for polypropylene.
• This integrated strategy offers significant GHG reductions and expands the usability of recycled plastics.
• The system supports a circular economy by enabling higher-value applications for recycled polypropylene.