Towards the circularity of plastics

(Credit: Tanvi Sharma on Unsplash)

Our modern world is addicted to plastics. Cheap, light, durable and very flexible they have largely replaced traditional materials such as metal and wood. Used for everything from food packaging and medical equipment to parts for consumer goods, plastics have made our lives easier and better in many ways.

But plastic waste is now one of the most urgent environmental issues of our time.

Disposal is difficult because of the huge volume of waste generated and its extreme durability. More than 30% is sent to landfill where it takes hundreds of years to decompose; even more is simply thrown away and accumulates around land, rivers, and oceans.

Although it is possible to recycle plastic waste, current methods are expensive and often polluting. Around 40% is incinerated to produce energy, while only 30% percent is recycled into new products. Astonishingly, less than 10% of the 8 billion tons ever produced worldwide has been recycled.

But now a team in the Department of Chemistry is developing new technologies which could transform the recycling of plastics. As Professor Peter Edwards explains: ‘The team views plastic waste as an untapped anthropogenic resource with substantial environmental and economic potential.’

The researchers started by developing a range of innovative processes to convert plastics into fuels and hydrogen. This led to the creation of the spin-out company Oxford Sustainable Fuels in 2017, which is now in discussions with sponsors to license their patented process.

More recently the research group have developed a process to deconstruct plastics back to their constituent ‘monomers’ for subsequent conversion into ‘polymers’ – the building blocks of plastics. ‘Whilst many Nobel Prizes have been awarded for the development of plastics over the last hundred years, we’re attempting to do the opposite and deconstruct plastic back into its constituent parts so it can be made into new products,’ says Edwards.

The process uses microwave technology instead of conventional heating to rapidly heat and activate catalysts to break down the material. The catalysts themselves are developed from abundant and inexpensive iron, avoiding the use of precious metals, and making the process cheaper, easier, and less polluting.

Edwards explains how the new technology should help the environment. ‘The process will reduce the environmental impact of the recycling process as it creates near-zero emissions, whilst it also avoids dependence on non-renewable petrochemicals to make new plastics. Eventually we hope it will reduce the amount of waste plastic that accumulates in land and water – so it will bring substantial benefits all round.’

This work has led to two major international patents and several scientific articles, the most recent published in the journal Nature Catalysis in November 2020. A new collaboration with the Biorenewables Development Centre (BDC) in York, funded by the University Challenge Seed Fund, will transition the technology ‘out of the lab’ and, building on BDC’s experience in scale-up microwave technology, enable transition to widespread industry application.

‘The beauty of the process is that we have taken existing microwave techniques already used by the scientific community and applied them in new ways to one of the most compelling problems of our time,’ says Edwards. ‘Our technologies will make recycling plastic more feasible and attractive and could help create a truly ‘circular economy’ for the material.

‘The availability of inexpensive microwave devices makes the process suitable for both large- and small-scale processing in different contexts. We particularly hope the process will benefit developing countries, offering them the opportunity to manufacture high-value products from an abundant resource (used plastic), using affordable and sustainable technology.’

 Peter Edwards is Statutory Professor of Chemistry

Funders: University Challenge Seed Fund