Moving from linear to circular household plastic packaging in Belgium: Prospective life cycle assessment of mechanical and thermochemical recycling

Currently, Belgium is in a transition period after which more household plastic packaging waste will be collected separately in function of increased recycling. The challenge is to identify the most environmentally sound treatment option for the increased selectively collected plastic waste. In this study, mechanical recycling (MR) and thermochemical recycling (TCR) of four newly collected subfractions, being polypropylene (PP), polystyrene (PS), mixed polyolefins (MPO) rigids and polyethylene (PE) films, were investigated through prospective Life Cycle Assessment (LCA), in comparison to incineration with energy recovery. Results showed clear benefits of recycling over incineration with energy recovery. Generally, MR showed a better net environmental impact compared to TCR (for PP, PS, MPO rigids and PE films, respectively, e.g., a global warming impact of 100, -1580, 539 and 101 kg CO2 eq. per ton by TCR, and -1183, -3096, -319 and -1162 kg CO2 eq. per ton by MR, and 2339, 2494, 2108 and 2141 kg CO2 eq. per ton by incineration). This could mainly be explained by the avoided burdens of virgin materials. Whereas TCR avoids the virgin supply of the feedstock for polymer production, MR avoids additionally polymerisation and granulation. MR products, i.e. regranulates or flakes, can be directly used in manufacturing, whereas TCR products require first processes like steam cracking, polymerisation and granulation before being used in manufacturing. As this study assumed a 1:1 substitution ratio between MR regranulates and their virgin alternatives, it presents the most favourable results for MR, which should be kept in mind and further investigated.