Imagine taking a worn-out pair of sneakers or used yoga pants back to the brand that produced them, knowing the polyester material they’re made of will be biologically broken down to its fundamental elements, then used to make a shiny new pair of sneakers or yoga pants or anything, really, that’s made from polyester. Which, incidentally, is a lot of stuff.

This is the future a biotech startup called Carbios and a group of well-known sportswear brands are working toward. The French startup, which has developed an enzymatic process to break down polyethylene terephthalate (commonly known as PET), recently signed an agreement with On, Patagonia, Puma and Salomon meant to accelerate the commercialization of its bio-recycling technology for textiles.

The consortium aims to develop the industry’s first large-scale fiber-to-fiber polyester recycling system, a process that could play a meaningful role in circularity in fashion.

The brands “can use plastics to make fibers, but they don’t have a solution for fiber-to-fiber recycling at scale,” Emmanuel Ladent, Carbios CEO, said in an interview.

At the same time, Carbios has partnered with PET manufacturer Indorama Ventures to build and operate the world’s first commercial-scale bio-recycling plant for PET-based plastic in Lunéville, a commune (or township) in the Meurthe et Moselle region of France. The company expects the facility, which will recycle local plastic waste, to begin operations in 2025.

PET is a polymer derived from oil that is primarily used to produce three products: plastic bottles: carpeting; and apparel. The clothing industry refers to PET as polyester, a pet name for a pet fabric that has become the world’s most commonly used fiber, comprising more than 50 percent of fibers produced globally.

In the United States alone, more than 34 billion pounds of clothing waste is created each year, much of which ends up in the trash.

Often blended with other fabrics, such as cotton, and typically accompanied with fixtures such as buttons, zippers and tags, polyester can be found in all types of apparel, sportswear and footwear. This design complexity makes our clothes and shoes notoriously difficult to recycle using conventional technologies. Many apparel and footwear brands use “recycled polyester” to some degree — in products often marketed as containing “ocean” or “ocean-bound” plastic — but this material comes from conventionally recycled plastic bottles, not from used clothing.

While this practice reduces the amount of single-use plastics that end up burned, landfilled or in the ocean and other waterways, recycled polyester from plastic bottles doesn’t address fashion’s own gargantuan post-consumer waste problem. In the United States alone, more than 34 billion pounds of clothing waste is created each year, much of which ends up in the trash.

A ‘truly circular’ solution

Carbios uses one of a handful of microbes, discovered by various scientists, that have developed a taste for PET. The company’s enzyme was first identified in compost, and has been modified by its own scientists to work faster and operate at high temperatures where PET is softer.

Carbios says its enzyme is also capable of selectively decomposing the polyester material, which makes it possible to recover basically all the polyester found in textile waste, even blended fabrics. And unlike conventional recycling, which degrades the quality of PET, limiting the number of times it can be recycled, as well as the amount that be used in any given product, enzymatic recycling breaks PET down at the molecular level, so it is possible to recreate a virgin quality material that can be recycled over and over again, making the process, in theory anyway, truly circular.

“In the traditional recycling world, the solutions are not circular. You can recycle materials one, two, three times, and then it’s over. With our technology, it’s almost infinite,” said Ladent, who joined Carbios late last year, replacing co-founder and CEO Jean-Claude Lumaret, who’d led the company since its founding in 2011.

French sports gear manufacturer Salomon, whose use of recycled polyester currently maxes out as 38 percent, believes the collaboration with Carbios will allow it to produce a 100 percent recycled polyester product, according to Olivier Mouzin, footwear sustainability manager at the company. “We think we will be able to produce recycled polyester with the same mechanical properties as the virgin one, which is not the case today,” he said.

Under the terms of the two-year agreement, the brands will collect post-consumer garments containing polyester, as well as work on developing sorting and dismantling technologies. In turn, Carbios will provide them with bio-recycled polyester made from those garments.

Mouzin believes it will take several years to reach the point where Salomon might actually produce a product using Carbios’s technology. The best-case scenario might be a small pilot project beginning in 2026 or 2027.

Hungry, hungry enzymes

Scientists have been studying plastic degrading enzymes for a couple of decades.

By the mid-2010s, plenty of these enzymes were known, but it was in 2016 that a key discovery was made. Researchers led by microbiologist Kohei Oda of the Kyoto Institute of Technology in Japan found a bacteria called Ideonella sakaiensis 201-F6, outside a bottle-recycling facility, which could not only break down and metabolize PET, it also could use the plastic as its main source of nutrients.

The key to this ability was a pair of unique enzymes made by the bacteria. The first (PETase) breaks down long PET molecules into smaller molecules, and a second (MHETase) then produces ethylene glycol and terephthalic acid, the chemical building blocks of PET. So Ideonella sakaiensis 201-F6 can completely reverse the manufacturing process that makes PET.

In the traditional recycling world, the solutions are not circular. You can recycle materials one, two, three times, and then it’s over. With our technology, it’s almost infinite.

This discovery energized enzymatic recycling research and led to further advances. While studying the Ideonella sakaiensis PETase enzyme, researchers from the University of Portsmouth in the U.K. and the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) produced a three-dimensional structure of the PETase enzyme that they then tweaked to help them better understand how it worked. In doing so, they inadvertently engineered the enzyme, making it even more efficient at degrading PET.

This research was led by John McGeehan, director of the University’s Centre for Enzyme Innovation, and Gregg Beckham, a senior research fellow and group leader at NREL.

Then in 2020, McGeehan’s team reported that it had linked the PETase and MHETase enzymes together. This “super-enzyme” could eat PET about six times faster than the two enzymes working separately. Other research groups have produced modified enzymes of their own, as has Carbios, whose process was validated on the cover of the science journal Nature that same year.

Scientists use syringe in Carbios lab

Carbios’s scientists studied various enzymes, including Ideonella sakaiensis PETase, but found that the leaf-branch compost cutinase (LCC) outperformed the other enzymes they tested. With the modifications Carbios scientists made, which allow the enzyme to work faster and operate at high temperatures, it remains the state of the art in the literature, Beckham said in an interview.

“To my knowledge, this remains the best enzyme or at least among the best enzymes reported,” he said. Still, Carbios faces a couple of significant challenges, namely energy intensity and cost.

Carbios’ process calls for heat treatment and grinding at low temperatures of the waste PET — the polyester shirt or plastic bottle — before it’s placed in a bioreactor with the enzymes. And the processes of heating and grinding the PET are energy intensive, Beckham said. “There are innovations that are needed to reduce the energy intensity of enzymatic PET recycling,” he said. “The dream is you can take textile waste clothing or plastic bottles and just drop it in the enzymatic reactor and go. I have no idea when or even if we’re going to get there, but that would be super cool.”

Then there’s the cost, which Mouzin acknowledges is a challenge. “But we need to explore it with Carbios. We need to work on that if we want to preserve the planet,” he said.

Given the extreme interest in this concept from industry, enzymatic recycling has the potential to scale relatively quickly, said Beckham, who is also the CEO of the BOTTLE Consortium, a U.S. Department of Energy (DOE)-funded research initiative that launched in 2020 to help drive commercialization of various new technologies (including but not limited to enzymatic recycling) to address the plastic waste problem.

BOTTLE, which stands for “Bio-Optimized Technologies to keep Thermoplastics out of Landfills and the Environment,” is made up of five DOE national laboratories and five universities, four in the U.S. and McGeehan’s team in the U.K. The consortium is working with industry partners, including Amazon, Patagonia, the Ocean Foundation, Kraft and Heinz, in its efforts to accelerate such technologies.    

The University of Portsmouth has also set up Revolution Plastics, which aims to forge links between academics and industry and has a joint Ph.D. project with Coca-Cola.

In terms of the commercialization of enzymatic recycling of plastic, Carbios is the furthest along. The startup has been making progress for several years, largely through partnerships with larger companies. In 2017, Carbios and L’Oréal (French) co-founded a consortium to help industrialize its bio-recycling process for plastic packaging, which led to the creation of food-grade, proof-of-concept bottles with consortium partners PepsiCo, Nestlé Waters and Suntory Beverage and Food.

Then in September 2021, Carbios opened a demonstration plant in Clermont-Ferrand, France, where it’s been testing its system for plastic bio-recycling. This led to the partnership with Indorama Ventures, one of the largest PET manufacturers with 22 percent of the market, to build and operate a commercial-scale plant. The roughly $206 million facility will have a processing capacity estimated at 50,000 tons of PET waste per year, or the equivalent of 2 billion bottles. Carbios also expects the plant to create roughly 150 direct and indirect full-time jobs.

And there’s more to come, Ladent said.

“Next year we plan to start licensing our technology, and I hope that soon we’ll have a license in the U.S.,” he said. “We would like to start production in the U.S. in 2026 or around that time frame.”

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