How depolymerisation could enable infinite reuse of plastics and the circular economy

The average UK household throws away 60 pieces of plastic packaging a week, according to the Big Plastic Count citizen science survey. This equates to approximately 1.7 billion pieces of plastic discarded nationally each week. The survey organisers report that only 17% of this plastic is recycled in the UK, while a further 14% is exported for recycling elsewhere. The remainder is incinerated (58%) or put in landfills (11%). Concerningly, the UK is still one of the better performing nations in this area. Globally, it is estimated that that less than 10% of plastic waste is recycled into new plastic products.

In the UK, efforts to collect post-consumer plastic for recycling are ramping up. Historically, what councils collect for kerbside recycling has been a postcode lottery. This has already started to change, with much of the country switching to a standardised four-bin system in April 2026 as part of the Simpler Recycling initiative. By March 2027, a fifth household bin collection, for soft plastics and films such as plastic bags, crisp packets and other food wrappers, should also be in place nationwide. But behind the positive headlines hides a very big issue: a lack of profitable recycling facilities capable of processing all this newly collected plastic waste.

Most plastic recycling facilities today are mechanical. The plastic is washed, shredded and then extruded into plastic pellets ready to be re-made into new plastic products. This approach is best suited to rigid, colourless single-material plastics such as single-use polyethylene terephthalate (PET) bottles for water and carbonated drinks and high-density polyethylene (HDPE) milk containers.

But plastics can only be mechanically recycled a finite number of times. Each cycle reduces polymer chain lengths, making the plastic weaker. Single-use PET drink bottles, for example, can be recycled into new PET bottles around five times, and HDPE milk containers can be recycled about 10 times. Once the polymers are too degraded, they are downcycled into items such as furniture, flowerpots and fibres for clothing and carpets. At their end of life these downcycled products are hardly ever recycled, meaning they wind up being incinerated or dumped in landfills.

How depolymerisation works

Expanding the types of plastics that can be recycled will necessitate new technologies. Recyclability should also be considered when designing products. Omitting unnecessary dyes and other additives can have a big impact, with the Sprite bottle one success story. In 2022, the Coca-Cola Company changed this bottle from its iconic green to colourless. ‘This was a big move towards getting some of that waste PET that’s difficult to recycle out of the stream,’ says Andrew Dove, a professor of sustainable polymer chemistry at the University of Birmingham, UK.

Depolymerisation is one of the new technologies on the horizon for plastic recycling. This approach breaks down the long polymer chains in plastics to retrieve their monomers that can then be used to rebuild new plastics. ‘Chemical recycling gets you back to the molecules that you make the plastics from,’ says Dove.

Importantly, these new plastics have indistinguishable properties from virgin plastics made directly from fossil fuels. This means that, unlike with mechanical recycling, there is no limit to how many times a plastic can be recycled using depolymerisation. ‘Chemical recycling has the potential to go round and round and round an infinite number of times,’ says Matthew Jones, a professor of inorganic chemistry at the University of Bath, UK. ‘Because you effectively go polymer, monomer, polymer, monomer, polymer, monomer, you theoretically generate materials with exactly the same physical and thermal properties [each time].’

The idea of depolymerising plastics isn’t a new one, but the technology has never previously taken off at scale, mostly for economic reasons. Today, a shift in public opinion towards plastic recycling and sustainability has caused a revival of interest in depolymerisation. ‘We need to try to make ourselves less dependent on crude oil and other carbon resources coming from fossils,’ says Bert Weckhuysen, a professor of catalysis, energy and sustainability at Utrecht University in the Netherlands.

PET projects

PET with added dyes and other additives that make them unsuitable for mechanical recycling are an area of high interest. This category includes coloured bottles, containers for personal care and household cleaning products, clamshell packaging for grapes and berries, meat packaging, and polyester clothing and carpets. ‘These are things that that don’t get recycled efficiently or to any great extent via mechanical means,’ says Christopher Layton, director of circular policy and strategy at the US-headquartered chemical company Eastman.

In early 2024, Eastman opened a PET depolymerisation plant in Tennessee, US. ‘We feed in those hard-to-recycle plastics and using methanol we simply unzip the polymer chain back into the individual links, the monomers,’ says Layton. Since the facility came online it has depolymerised hundreds of thousands of tonnes of PET back to its dimethyl terephthalate and ethylene glycol building blocks.

‘We can get to a monomer quality that’s indistinguishable from the same monomers we produce today on fossil feeds,’ Layton says. ‘It’s a very high yield process with about 90% of the waste plastics that go in coming out as the two monomers.’ Eastman then repolymerises these into pellets on the same site for use in a variety of applications including food grade packaging. ‘The two monomers are held in storage tanks, and then we feed them to the various polymer lines in conjunction with, or in lieu of, those same fossil monomers,’ he says.

The high cost of collecting and manually sorting the raw materials means that Eastman charges a premium for its recycled PET compared to virgin plastic. This price difference is typical across the recycled plastic market. To really hit the mainstream, the price of recycled plastic needs to match that of virgin plastic. The increasing global oil prices will help with this, as will economy of scale. Pro-recycling governmental policies are also driving change in some parts of the world. The UK and some other European countries, for example, now offer tax incentives for companies using recycled plastics in their packaging.

Governmental support for plastic recycling is not universal, however, with the US being of particular concern. Eastman’s plan to build a second PET recycling plant, in Texas, is currently paused due to the US Department of Energy rescinding a previously agreed $375 million (£277 million) grant in early 2025. Some academics working on the depolymerisation of plastic waste have similarly lost out on US government funding under the Trump administration.

Improved catalysts and processes may also help bring down costs of depolymerisation. ‘If we can get a faster catalyst that operates at half the temperature, then we’ll have a much better process from an energy point of view and a speed point of view,’ says Dove. His group is working to recycle hard-to-recycle PET, in collaboration with Joe Wood, a professor in chemical reaction engineering at the University of Birmingham, UK.

The academics are developing a semi-continuous process where PET reacts with ethylene glycol and a solid-state catalyst to produce the monomer bis(2-hydroxyethyl) terephthalate (BHET). One of the biggest challenges is finding catalysts that work with the additives, dyes and other impurities typically present in plastic waste, Dove says.

They are also exploring low-energy methods to purify the BHET. ‘Once the catalytic cycle is done, we could then put the mixture through a membrane separation process,’ says Wood. Membranes with different pore sizes able to collect the BHET and also recover the catalyst and left over ethylene glycol for reuse are of particular interest.

Recycling nylon 6 textiles

Nylon fibres in end-of-life textiles are another type of plastic that can’t currently be recycled into virgin-like material. It can be mechanically recycled, but the resulting degradation to the polymer means that the recycled material isn’t suitable to reuse in clothes. Instead, it is typically used in car parts and carpet backings.

BASF has known how to depolymerise nylon 6 (also called polyamide 6) to its monomer caprolactam since the 1940s, when it first started to manufacture the material. But it’s only recently that the company has seen a market for recycled polyamide 6 for textiles, he adds, due to a growing public interest in sustainability.

In March 2025, BASF opened a polyamide 6 textiles recycling plant in Shanghai, China. ‘This [location] is the industrial gateway for textile industries in China,’ says Faissal-Ali El-Toufaili, the technical lead for BASF’s depolymerisation project. This plant can produce 500 tonnes of recycled polyamide 6 from textile waste per year. The feedstock is typically 80–90% polyamide 6 and includes offcuts from textile manufacturers and end-of-life clothing from donated textile waste sorting houses.

For sustainability reasons, the technology breaks the polymer without harsh chemicals, and the energy consumption is small, says El-Toufaili. After the depolymerisation the caprolactam is extracted and purified ready to be re-polymerised using existing infrastructure on the site.

Big brands such as Zara and Adidas have used this recycled polyamide 6, which BASF calls Loopamid, in premium limited-edition collections. BASF is currently working to reduce the costs of the sorting of post-consumer textile waste. ‘We are developing automatic sorting with partners and hopefully in the future this will be very efficient,’ El-Toufaili says.

Breaking down polyolefin plastics and films

Historically, most soft plastics and films – the plastics that the UK will start kerbside collections for in 2027 – have been incinerated or landfilled. In recent years a number of attempts have been made to commercialise the use of pyrolysis to recycle polyolefins. Pyrolysis involves heating plastics to extremely high temperatures, to break the chemical bonds and produce complex hydrocarbon mixtures such as naphtha. These mixtures are then purified and processed using existing crude oil infrastructure to recreate monomers.

Depolymerisation offers a shorter recycling loop than pyrolysis for polyolefins. In 2024, the academic lab of John Hartwig, a professor of sustainable chemistry at the University of California, Berkeley, in the US, reported the use of two common industrial catalysts to depolymerise polypropylene, polyethylene and mixtures of the two, into monomers suitable for re-use.

The group discovered that the first catalyst cleaves the polymer into smaller pieces with carbon–carbon double bonds on the ends. The second catalyst adds a carbon atom (from ethene gas pumped into the reaction vessel) onto this double bond. Next, a metathesis reaction breaks apart the double bond, releasing a small molecule from the end of the polymer chain. For polyethylene, the released molecule is propene and for polypropylene it is a blend of propene and isobutene. ‘One carbon of the propene comes from the waste plastic, and two from the ethene,’ explains Hartwig. The metathesis reaction leaves a double bond on the polymer chain; it then continues as a cycle, eating away the polymer chain until it has all been converted into monomer. The propene and isobutene are produced at mild temperatures in greater than 90% yield.

This process does not quite return polyolefins to their original monomers, but does produce alternative light hydrocarbons that can be polymerised into other plastics. The team is currently working to increase the activity and robustness of the catalysts.

Managing mixed material recycling

Michael Shaver, a professor of polymer science at the University of Manchester, UK, is exploring depolymerisation in complex plastic systems. In 2023, he reported the concept of repolymerisable bank cards as an example of designing products with recyclability in mind.

Each year, roughly six billion polyvinyl chloride bank cards are produced globally that contain numerous valuable metals and other materials held in the magnetic strip, microchip and antenna. End-of-use bank cards are not currently recycled; consumers just cut them up and put the pieces into the domestic waste.

Working with Mastercard, Shaver produced a glycosylated PET bank card. ‘It had the same properties of the original card,’ he explains. The new card can be depolymerised in the presence of a catalyst under mild conditions, to recover BHET and cyclohexanedimethanol monomers, along with the metals. ‘What that depolymerisation allowed us to do was to recover the metals … which is actually the economic driver,’ he explains.

Shaver’s bank card chemistry may have been successful but the roll out of this technology is hindered by the lack of current infrastructure for consumers to return expired bank cards. The team has therefore turned its attention to hotel key cards that, Shaver says, will be much easier to collect in bulk for recycling.

This idea of recovering other valuable materials in plastics to improve the economics of plastic recycling is also being explored by other academics – including Weckhuysen. His group is currently working to efficiently recover inorganic pigments and organic dyes from polyesters for reuse.

An alternative approach to reducing depolymerisation costs is to remove the need for costly sorting all together. To achieve this, some academics have recently started exploring the depolymerisation of multiple plastic types sequentially in the same reactor. ‘Let’s say you’ve got a mixture of five different plastics, and we sequentially degrade one, then the other, then the other, then the other, then the other, [that would mean] you don’t have to separate them first,’ says Jones.

His group is currently designing catalysts and exploring temperature gradients to achieve this. In 2025, Jones reported a lab-scale effort to sequentially depolymerise polylactic acid, then bisphenol A polycarbonate, then PET, using a single catalyst under mild conditions.

The plastic world is a highly complex one. Today, we use thousands of different types of plastics to make a staggeringly wide variety of products. Each of these plastics contains a bespoke combination of dyes, other materials and additives to achieve the right performance for their purpose. There will never be a single plastic recycling approach that suits all of these. ‘There is no panacea,’ says Shaver.

This article only gives a snapshot of some of the depolymerisation approaches in development. These and many more chemical recycling approaches will be needed if society is to truly get a handle on its plastic waste problem. ‘Chemical depolymerisation technologies are going to be an important complementary tool to other circularity routes that that we have available to us,’ Shaver concludes.

Nina Notman is a science writer based in Salisbury, UK