Polypropylene progress

03/04/2024

Around 20% of the plastic recycled is polypropylene, but the diversity of products it protects has prevented safe reprocessing back into food packaging. Until now. David Burrows reports When you think of recycling plastic, what springs to mind? It’s probably a bottle – one maybe protecting a fizzy drink (likely made of PET, polyethylene terephthalate) or milk (which is mostly HDPE, or high-density polyethylene). These polymers represent success stories of UK plastic recycling. Recycling rates could be higher, but there is the know-how, technology and infrastructure to collect, sort, clean and reprocess them back into ‘new’ bottles in a so-called ‘closed loop’ – replacing virgin plastic and reducing emissions with recycled polymers (rPET and rHDPE). Now consider polypropylene (PP). In its rigid form, it’s used for everything from yoghurt pots and meat trays to detergent containers and bottle caps (as it’s easy to separate in a float/sink tank from materials such as PET). White PP is often the material of choice for things like pot noodles, which require hot water to be added before eating them. PP is “tough, lightweight and does not mind heat”, writes James Piper in The Rubbish Book. “It keeps products dry and fresh, which makes it an effective option for margarine tubs, yoghurt pots and plastic straws.” PP in food packaging It’s not just found in supermarkets, either. Two-thirds (66%) of the global plastic footprint of McDonald’s is PP, while at Starbucks it’s 59%. That’s 107,420 and 90,576 tonnes respectively. The figures, compiled as part of WWF’s ReSource project, don’t show how much of this is recycled content but it’s likely to be very, very little – if anything. Indeed, the current availability of recycled PP (rPP) for food-grade materials sits at “near zero”, says a spokesperson for Wrap, a charity that runs the UK Plastics Pact with fast-moving consumer goods (FMCG) companies and the plastic packaging supply chain. Research it has carried out shows that PP accounts for around 60% of the rigid plastics stream once PET and HDPE are stripped out. Only material that has been processed via chemical recycling (which comes with its own environmental and economic challenges) has been used in food or drink packaging to date. In fact, there is very little food-grade post-consumer rPP available anywhere in the world, says Marcian Lee, an analyst with Lux Research in Singapore. “The main issue is that the recycling feedstock must be PP food packaging in the first place, which is a huge challenge to accurately identify,” he adds.