A recent comparative study from IVL Swedish Environmental Research Institute has found that optimising the sorting of plastic packaging waste can contribute considerably to reducing greenhouse gas emissions. The more thoroughly plastics can be separated according to their specific properties, the more efficiently they can be recycled and used again, the study found.
In collaboration with the consulting firm Terra and the packaging compliance scheme Svensk Plaståtervinning (Swedish Plastic Recycling), the researchers assessed the climate impact of various treatment options in Sweden. They concluded that high-quality recycling has a "significantly higher" climate benefit compared to low-value recycling or incineration only.
Sorting is key to emission reductions
While the highest emissions are produced by primary production and waste incineration of plastics, "advanced sorting can reduce the climate impact of plastic packaging recycling," the authors assert. "With better sorting, where different types of plastic are separated, the plastic can be recycled into new packaging or into other products, without unnecessary quality losses. The material can then be recycled multiple times," said Emma Moberg, researcher and life cycle assessment expert at IVL.
The study is based in part on internal operational data from the Site Zero facility in Motala, Sweden. The extended producer responsibility (EPR) system Svensk Plaståtervinning describes it as the world’s largest and most modern sorting plant for plastic packaging.
The study found that downcycling of plastic waste to railway sleepers reduces climate impact by only 4 per cent compared to incineration with energy recovery. By comparison, high-value recycling with advanced sorting results in a 27 per cent reduction in climate impact. "The longer you can maintain the quality of the plastic in the life cycle through advanced sorting, the lower [the] emissions," said Terra’s Tomas Ekvall, lead author of the study.
The study considered three different scenarios. In the "incineration with energy recovery" scenario, all plastic packaging is thermally recovered. In the second scenario, the material is recycled, but downcycled, which is not uncommon in Sweden. The study's author's note that the country currently succeeds in meeting its 50 per cent recycling target by transforming mixed plastic packaging into railway sleepers as a replacement for wooden sleepers. The third scenario was advanced sorting, whereby the 50 per cent target is met by separating plastic waste into individual polymer fractions, which enables high-quality mechanical recycling. In this case, a small share of the plastics are still downcycled.
According to the analysis, downcycling has an advantage over incineration, as it postpones the ultimate release of fossil-based CO₂ and frees up incineration capacity in Sweden in the short term. However, the authors conclude that advanced sorting is the most effective method for reducing greenhouse gas emissions, as it minimises the need for primary plastics and reduces incineration to an absolute minimum.
No comparison with chemical recycling
The study does not make any direct comparison with chemical recycling, but notes this technology "may potentially complement mechanical recycling". Because most chemical recycling processes require some degree of pre-treatment such as sorting and washing, they could sometimes be in competition with high-value mechanical recycling for the same sorted waste streams, the study authors wrote.
In gasification processes for mixed plastic waste streams, the recycling yield is low because a share of the material is used as a source of energy, so roughly half of the carbon is released into the atmosphere, according to the study. However, the researchers note that "the yield and climate impact may improve in the future if the process is electrified."
Authors call for amendments to legislation
Although Sweden’s current legislation for recycling plastic packaging waste does prioritise recycling over incineration, "it does not take into account the potential environmental and circularity benefits that different levels of recycling can deliver," the authors say. Linnea Granström, climate and environmental strategist at Svensk Plaståtervinning, therefore calls for targeted adjustments to the legislation: "There is a considerable difference between recycling with or without advanced sorting for mixed plastic waste. Therefore, appropriate requirements and instruments should be devised accordingly."
