Shrinking the carbon footprint of yoga pants

Several biobased chemical makers plan to scale up production of nylon precursors made via fermentation. They are responding to demand from consumer product companies that want to reduce greenhouse gas emissions from yoga pants, athletic clothes, and other plastic products.

The clothing company Lululemon says it will work with the start-up ZymoChem to scale up a fermentation process for adipic acid, a precursor of nylon 6,6. The deal follows a 2021 announcement that the clothing company was partnering with Genomatica, which has technology to produce fermentation-derived hexamethylenediamine (HMD), the other precursor of nylon 6,6.

Genomatica has also been working with the nylon maker Aquafil to demonstrate technology that ferments sugar into caprolactam, which is polymerized to make nylon 6.

Lululemon calls nylon a foundational material for its yoga pants, and in its most recent impact report notes that nylon accounts for more than 30% of the material it uses. And because nylon production emits lots of greenhouse gases, the fiber also represents a significant portion of the clothing maker’s climate impact.

Adipic acid is usually made by reacting nitric acid with a mixture of cyclohexanone and cyclohexanol. The process releases nitrous oxide, a greenhouse gas that, if not destroyed, warms the atmosphere hundreds of times as much as carbon dioxide does. Making caprolactam also emits nitrous oxide.

To make HMD 1,3-butadiene is reacted with hydrogen cyanide to form adiponitrile, which is then hydrogenated to produce HMD, releasing carbon dioxide along the way. Fermenting sugar into nylon precursors could reduce nylon’s greenhouse gas emissions by eliminating fossil fuel feedstocks and steps that create nitrous oxide.

ZymoChem CEO Harshal Chokhawala says Lululemon approached his company after discovering some ZymoChem patents describing a fermentation process for adipic acid. Lululemon invested in ZymoChem’s series A funding round in January 2024 and then ZymoChem started working with the company on proof-of-concept projects.

Chokhawala says he’s confident that at large scale, his company’s fermentation route to adipic acid is efficient enough to compete with the fossil-based one. “In the chemical industry, once you bring a better process to the table . . . the entire industry starts to switch,” he says. “That’s what we want to be. That’s our mission.”

Other companies are also developing sustainable nylon. In November, the chemical firm Toray Industries announced that it was working with PTT Global Chemical to study the viability of large-scale biobased adipic acid production. The companies say they can ferment nonedible sugar into muconic acid and then hydrogenate that into adipic acid. Meanwhile, the start-up OzoneBio is developing a process that uses pyrolysis to convert nut shells and wood waste into adipic acid.

Beyond nylon, last year, the fiber producer Hyosung announced it would use a Genomatica technology to produce biobased 1,4-butanediol, used to make spandex fibers and other plastics, at a $1 billion plant in Vietnam. The biobased chemical firm Qore plans to use the same technology at an Iowa plant, which is set to start production next year.

The scale-up plans from Toray and PTT, ZymoChem, and Genomatica show that sustainable nylon isn’t far behind spandex. But Tiffany Hua, an analyst who covers textile technologies for the intelligence firm Lux Research, says clothing companies have yet to adopt meaningful amounts of any fermentation-derived fiber. Lululemon reports that the biobased nylon used to produce a limited number of shirts in 2023 made up less than 1% of the nylon it purchased during that year.

Working out kinks in these new manufacturing processes will add costs at first, Hua says. But she expects that improvements in strain engineering and fermentation technology will eventually help biobased fibers break into the textile industry.

“What we are seeing here is the very beginning of biobased chemical production,” Hua says. “We won’t expect major production gains until we solve the underlying biological technologies.”