We know the world has a problem with plastic – 370 million tonnes of it were produced in 2020 alone. This problem is complex as these versatile materials are a vital part of modern society. Recycling will be one of the main solutions to growing mountains of waste plastic. But there is another facet to this problem – plastics are complex materials in and of themselves, which makes dealing with them at the end of their life that much harder.
Plastics are more than just polymers. To turn polymers into the everyday, indispensable materials we’re familiar with, a range of additives must be formulated with them. These include everything from lubricants to ease processing, to plasticisers to improve flexibility and pigments to impart colour. This is before we even get to the chemistry taking place in plastics themselves, as they are not static mixtures and contain breakdown products, unreacted monomers and manufacturing byproducts. One study identified more than 10,000 additives in use in the plastics that are on the market today. The question is whether such a huge range of different additives is strictly necessary. Probably not. Many will be doing very similar jobs.
These additives all make recycling more difficult, however, as two plastics made using exactly the same polymer can have different formulations. Recyclers want to work with the same polymers, but the additives used in some plastics can pose a threat to human health or the environment, limiting their options. The first step on the road to addressing this problem will be understanding the size of it. Creating an inventory to track all the additives in use would be an excellent start. From there it would be possible to start whittling down some of the additives that could be easily substituted with ones that are simpler to reprocess.
All this has to happen with industry on board. As the Royal Society of Chemistry’s Camilla Alexander-White notes, past efforts to tackle waste have too often been led by politicians without getting industry and scientists in the room. The end product can be ineffectual or even counter-productive. The good news is there should be benefits for every business along the supply chain. As more and more countries take up the principle of the polluter pays, producing plastics that are simpler to manufacture and easier to recycle is sure to be a boon. Industry has already shown that it can share data on a huge scale during the implementation of the EU’s Reach regulation, so clubbing together to share best practice on plastic additives is achievable. And with a global plastic waste treaty in the works, voluntary action now will deliver benefits later as legislation begins to bite.