Many of the materials commonly thrown in household recycling bins, including flexible films, multilayer materials and a lot of coloured plastics, cannot be recycled using conventional methods. And only about 9 per cent of plastic in the US is ever reused, often in low-value products.

But a team at the University of Wisconsin–Madison believes that its new technique can turn low-value waste plastic into high-value products while reducing greenhouse gas emissions by roughly 60 per cent.

The process relies on pyrolysis, a method whereby plastics are heated to high temperatures in an oxygen-free environment to create pyrolysis oil. This oil contains large amounts of olefins – a class of simple hydrocarbons that are central building blocks in today’s chemicals and polymers, including various types of polyesters, surfactants, alcohols and carboxylic acids.

In current energy-intensive processes such as steam cracking, chemical manufacturers produce olefins by...