Gary Anderson designed the Recycled Mobius Loop logo in response to a Container Corporation of America competition in 1970. Entrants were asked to create a simple recycled paper icon. Nowadays this symbol is everywhere. And our domestic recycling bin is almost always full these days – but I can hardly believe that my hometown only added cans and plastic bottles to its roadside recycling service in July 2009. However, putting plastic in your trash is not a guarantee that it will be effectively recycled.
Sorting mixed plastic waste efficiently and accurately is a tedious but essential step for most recycling methods. The technology for sorting this mish-mash of household waste is surprisingly mature. Hayley Bennett’s recent article on ferrofluids showed how a company in the Netherlands uses magnetic nanoparticles suspended in ferrofluids as part of a density-based sorting process. Sorting is important because the higher the homogeneity of the waste stream, the higher the chance that the polymers will retain their value when recycled.
Most polymer recycling is mechanical. Crushing a plastic and melting it into a new product does not change the base polymer. However, hydrolysis and transesterification reactions mean that the polymers degrade with each cycle, so they cannot be recycled indefinitely with this technique.
Chemical recycling – the breaking down of polymers into monomers for use in another polymerization reaction – can result in high quality products with high-end uses. Such methods are less established, but the current methods are energy intensive and require further processing in the sequence.
Then there is the upcycling of plastic, which has lucrative potential. In June, we presented you with research that successfully converted a plastic bottle into vanillin. Microbes with specific enzymes turn an almost useless starting material into a chemical with superior economic value.
Creating a circular economy for plastics will never be easy. Radically reducing the amount of plastic we produce and use in the first place, of course, has to be part of the equation. By finding ways to convert discarded plastics into chemicals and materials with higher value, scientists are revising society’s view of plastic waste. But let’s be realistic, plastics recycling has to be profitable. The earth’s plastic waste problem needs long-term solutions that can save themselves and the planet.