Chemical additions to plastic that mimic natural polymers like DNA can create materials that break down in days, months or years rather than littering the environment for centuries. Researchers hope their new technique will lead to plastic products that serve their purpose and then safely self-destruct.

In 2022, more than a quarter of a billion tonnes of plastic was discarded globally, and only 14 per cent was recycled – the rest was either burned or buried. The promise of a practical, biodegradable plastic has been around for at least 35 years, and there have been efforts to make such materials using everything from bamboo to seaweed. But, in truth, many such materials are difficult to compost and their producers make unrealistic claims.

Now, and his colleagues at Rutgers, The State University of New Jersey, are developing a technique to create plastics with finely-tuned lifespans that could quickly break down either in compost or in the natural environment.

Gu wondered why natural, long-stranded polymers like DNA and RNA can break down relatively quickly, but synthetic ones, such as plastics, can’t, and if there was a way to replicate their process.

Natural polymers contain chemical structures called neighbouring groups that aid in deconstruction. These structures power internal reactions called nucleophilic attacks that sever the bonds in polymer chains – something that requires a great deal of energy with normal plastics.

Gu and his team created artificial chemical structures that mimic these neighbouring groups, and added them when making new plastics. They found that the resulting material could break down easily and that by altering the structure of the additions, they could fine-tune how long the material remained intact before deconstructing.

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After the plastic breaks down, the long polymer chains are converted into small fragments, which Gu hopes will either be used to make new plastics or will safely dissolve into the environment.

“This strategy works best for plastics that benefit from controlled degradation over days to months, so we see strong potential for applications like food packaging and other short-lived consumer materials,” says Gu. “At the moment, it is less suited for plastics that must remain stable for decades before breaking down – such as construction materials or long-term structural components.”

But there are several problems to solve before this type of plastic can be used commercially. The liquid left over after the plastics deconstruct is made up of fragments of polymer chains, and further tests are needed to ensure that this soup of parts isn’t toxic and can therefore be safely released into nature.

Also, ultraviolet light is currently needed to initiate the deconstruction, although ambient sunlight is sufficient. So until the group finds ways to create materials that can break down in the dark, any plastic that is buried or otherwise covered up will remain in the environment almost indefinitely.

In artist Mandy Barker’s new book, , she uses the same technique as the botanist and pioneering photographer Anna Atkins to draw attention to the ongoing pollution crisis facing our oceans. Like Atkins nearly two centuries earlier, Barker scoured the British coastline for items to image. Rather than finding natural beauty, however, she saw discarded clothing washing up onto the beaches. Her first find, she says, looked like seaweed. “It was kind of an attractive, beautiful piece of cloth.” But as pieces of jackets, dresses, shoes, underwear and school uniforms started appearing, the scale of the problem quickly became apparent to her.

A genetically modified bacterium can break down chemicals in nylon and turn them into useful products, which could one day help us recycle clothes and fishing nets.

Nylons, or aliphatic polyamides, are plastics that are widely used due to their high durability and tensile strength, but their recycling rate is below 5 per cent.

“Production is around 10 million tonnes per year, but at the moment there’s basically no recycling,” says at the Jülich Research Centre in Germany. “Even incineration is difficult because you get cyanides when you burn them. The vast majority ends up in landfill.”

Nylon can be dissolved in a strong acid solution, but the mix of chemicals generated isn’t valuable enough to make this commercially useful.

Now, Wierckx and his colleagues have used a combination of genetic engineering and laboratory evolution to create a strain of the bacterium Pseudomonas putida that can break down the various compounds that are produced once nylon has been dissolved and turn them into something useful.

The bacterium is already known for degrading oil-based materials and in spills. It is also showing promise at breaking down plastics.

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Wierckz and his colleagues took a strain known as P. putida KT2440 and gave it genes to help it metabolise various chemicals in dissolved nylon. They then cultured bacteria in the lab on these chemicals again and again until they found a strain that thrived. The researchers continued to modify and culture it until they had bacteria that could use the compounds in nylon to create useful products, such as polyhydroxybutyrate – a biodegradable plastic that isn’t harmful to living tissues.

“T��� Pseudomonas consumes almost all the pre-treated plastic,” says Wierckx. “What we can measure is that about 80 to 90 per cent is being consumed, but I think that is an analytical limitation, and it’s actually consuming almost everything because we don’t see anything left there.”

But improvements are needed before this technique could be used commercially, says Wierckx. For example, the amount of useful product is still only about 7 per cent of the dry bacterial biomass at the end.

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Improving that will require further modification of bacteria and adjusting the chemicals used to tweak what is fed to the microorganisms, he says. “It’s probably going to be 10, 20, 30 years until we see this happening.”

We don’t need to worry that the bacteria will one day dissolve our underwear, though, says Wierckx. “It’s not going to eat all the plastics in our clothing and cars. We need to pre-treat the plastic so it becomes digestible.”

This also means we can’t yet use the bacteria to clean up old fishing nets in oceans. But Wierckx hopes that having this recycling process will encourage the future collection of old nets, clothing and car engines, which contain heat-resistant plastics, so they can be recycled.