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This mutant enzyme eats old plastic and spits out the materials to make it new again

Recycling plastic is very hard, but not for the enzymes found in bacteria from landfills.

This mutant enzyme eats old plastic and spits out the materials to make it new again
[Photos: courtesy Carbios]

French startup Carbios has developed a mutated bacterial enzyme that can almost completely digest old plastic bottles in just a few hours—helping turn the material into the chemical building blocks to make new plastic. The company has been working with the enzyme in its factory, but now the idea of digesting plastic is getting a boost from the scientific community: A recent study published in Nature validates that the process works.

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Unlike standard mechanical recycling, which “downcycles” plastic into a lower-quality material, the enzymatic process makes it possible to recycle a bottle into a material that’s equal in quality to virgin plastic made from fossil fuels. Mechanical recycling, which involves washing, shredding, and melting plastic, “is limited,” says Carbios CEO Martin Stephan. “To make a transparent bottle with that technology, you need a transparent bottle as a feedstock. And you cannot do that infinitely.” After six or seven cycles of recycling, the plastic might only be good enough to use for something like the plastic on the backing of a carpet, and eventually, it will have to be thrown away entirely.

[Photo: courtesy Carbios]
“At the very end of its life, it will end up in a landfill or incinerator,” says Stephan. “So it’s not a solution for the end of life of plastics, whereas our solution is an infinite recycling solution.” The new process can also turn a black plastic bottle into a white polyester T-shirt, or turn blue polyester into a new green bottle.

[Photo: courtesy Carbios]
The company’s scientists studied thousands of microorganisms at a landfill, eventually discovering some that had evolved enzymes that could break down PET plastic, the most common type of plastic (nearly 70 million metric tons are produced globally each year). The natural process happened slowly, but the team introduced mutations that made it faster. In 10 hours, with the new process, a metric ton of shredded plastic will be 90% degraded.

Even as many brands work to reduce single-use plastic, Stephan argues that plastic still has a place—it can reduce food waste by keeping food fresh longer, for example. But any plastic that remains in use has to be handled differently. That means better infrastructure to collect recyclables and better technology for recycling. “One of the solutions is to give value to waste which has low or no value,” Stephan says. “That’s exactly what we are doing. We’re convinced that by doing that we contribute to reducing plastics pollution, because instead of ending up in the environment, a post-consumer bottle will end up in a bin—there’s value somewhere in a recycling plant using our technology.”

[Photo: courtesy Carbios]

Several large companies, including L’Oréal, Nestlé Waters, PepsiCo, and Suntory Beverage & Food Europe have already partnered with Carbios to help the company move to commercial production. But the company says that the validation of its technology in a respected scientific journal will help bring more partners on board.

The company is currently piloting the process in a large lab, and construction is underway on a demo plant that will begin operation next year to gather more data; the company will then begin to license the technology to plastics producers. Novozymes, a biotech company, will produce the enzyme at scale.

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About the author

Adele Peters is a staff writer at Fast Company who focuses on solutions to some of the world's largest problems, from climate change to homelessness. Previously, she worked with GOOD, BioLite, and the Sustainable Products and Solutions program at UC Berkeley, and contributed to the second edition of the bestselling book "Worldchanging: A User's Guide for the 21st Century."

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