The world is drowning in plastic. About 60% of the more than 8,700 million metric tonnes of plastic ever made is no longer in use, instead sat mostly in landfill or released to the environment. That equals over 400kg of plastic waste for every one of the 7.6 billion people on the planet.

One reason for this is that many plastics are not recyclable in our current system. And even those that are recyclable still go to landfill eventually.

Plastics cannot be recycled infinitely, at least not using traditional techniques. Most are only given one new lease of life before they end up in the earth, the ocean or an incinerator. But there is hope in a different form of recycling known as chemical recycling.

Traditional physical or mechanical recycling typically grinds down plastic into smaller parts that are then mixed and moulded together to create lower grade plastic products. Chemical recycling, on the other hand, breaks the plastic down to the molecular level, making available “platform molecules” that can then be used to make other materials. It’s early days for this idea but, in principle, it could open up a whole range of opportunities.

Plastics are a broad classification of materials known as polymers, which are made from small “monomer” building block molecules composed mostly from carbon and hydrogen. The challenge in chemically recycling plastic involves finding the right techniques to break down and reconstitute the material into a variety of end products while minimizing waste.

All this needs to be done in a productive, economic, large-scale and carbon-neutral way. The eventual solution should create less harm than the problem it is trying to solve.

The monomers that make up plastics can take a variety of shapes and sizes: some are straight lines, some are branched and some have rings. The ways that they are bonded together determines the plastic’s material properties, including how easy it is to break them down, their melting temperatures and so forth.