Mechanical recycling of plastic will never be the whole package

A recent announcement from Plastic Recyclers Europe, casting doubt on the new ‘Quality Recycling Process’ developed by Ceflex, has highlighted the difficulties that are emerging as industry scales up the mechanical recycling of waste plastic. Those who know most about the properties of polymers, the manufacturers themselves, are busy hedging their bets with investments in other technologies. Shell Chemicals has just announced a new strategic cooperation with Pryme in Rotterdam to convert 60,000 tonnes of waste plastic to pyrolysis oil, which can be used as a raw material for new polymers via chemical recycling.

In reality this disagreement is part of a struggle to control the value chain for high quality recyclate. You might think that recyclers, the mainstay of the business for a long time, will automatically dominate. But polymer suppliers are muscling in by securing their own supplies of end-of-life plastic from waste management companies. They are doing their own compounding to produce high quality blends of recyclate and virgin material with guaranteed properties. They are even producing new grades of virgin polymers to improve the properties of the final virgin/recyclate blend. Their actions leave the traditional operators with lower quality material. The consumer brands, who are facing taxes on virgin plastic packaging, will be buying these high quality blends of recyclate. Because premium products require the best packaging.  

So Ceflex (The Circular Economy for Flexible Packaging initiative), which comprises polymer producers and international brand owners, is commercialising a process to separate out more of this high quality material. They are proposing advanced near-infrared sorting by polymer types and colour, followed by washing and deodorising, that creates high quality transparent flexible rpolyethylene  and rpolypropylene of mixed colours. The rest of the stream is destined for less demanding applications, markets which  are already saturated according to Plastic Recyclers Europe. They claim that the Ceflex process ‘ will jeopardize well-established and well-functioning recycling processes’ The polymer suppliers’ answer is probably that chemical recycling is the best solution for  residual plastic waste which can’t find a market. 

This scramble for control of high quality recyclate is a manifestation of the problems caused by the diversity of polymer types and grades that are in use. Inadequate sorting of different polymer types, melting point variation for different grades of the same polymer and the tendency of plastic to degrade as it is melted, all contribute to poor quality recyclate. The term ‘downcycling’ summarises the all too frequent outcome. 

In practice, there are some technology solutions that should boost the availability of better quality mechanical recyclate. Firstly, non-recyclable multilayer packaging with different polymer layers will be replaced by recyclable ‘monomaterials’- laminates of different grades of the same polymer type. Secondly, additives are being developed to improve the mixing of different polymer types when they are melted together. These ‘compatibilisers’ are tailored to the actual polymers being blended, and they produce a recyclate with improved properties which may be suitable for premium packaging. 

Of course, there is a limit to how much sorting and packaging design can improve the properties of recycled plastic. Mechanical recycling is really an extended reuse phase with a limited number of cycles before disposal is necessary. So, other technology solutions such as chemical recycling and  ‘organic recycling’ of biodegradable plastics will also be required. Mechanical recycling on its own will never be enough. We need a whole packet of technologies to get to scale.

Published: 19 October 21

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