(Bloomberg) -- As apparel brands face pressure to curb fashion’s enormous waste problem, many are turning to resale programs that let consumers cash in on used duds. But companies that make intimates don’t typically have that option: When underwear is past its prime, the obvious solution is to toss it, adding up to billions of pounds of textile waste over time.

What if there was another way?

Los Angeles-based Kent says there is. For two years, the company has been selling a line of “fully compostable” underwear made from 100% pima cotton, which has longer fibers and is known to last longer than traditional cotton blends. Customers can buy Kent undies for about $25 apiece online or in Madewell stores, and at Nordstrom and Anthropologie within the next year.

When a pair of Kent undies are ready for decommissioning, they can be dropped into a regular compost bin or mailed back to the company, which works with a partner in southern California that repurposes the briefs into soil (more on that later). Since launching in 2020, Kent says it has sold 17,500 pairs and earlier this year the company received $200,000 and a valuable nod from investor Daymond John on TV show Shark Tank.

As apparel goes, underwear might seem simple. But it’s emblematic of the challenges facing companies looking to repurpose used clothes. While Kent’s secret is using 100% cotton — with zero other materials, synthetic dyes or softeners — customers tend to prefer underwear that’s also stretchy, which requires the use of spandex or elastane. Neither is compostable or recyclable, and both have a low melting point that makes it difficult for the shredders used in textile-recycling plants to process in any large quantity, says Jessica Schreiber, founder and CEO of Fabscrap, a New York City-based company that specializes in textile recycling and reuse.

Most intimates come from “fossil fuel-based non-renewable resources,” says Rachel Kibbe, executive director of the American Circular Textiles Group, which is pushing for policy regulation in the textile industry, and CEO of consulting firm Circular Services Group. “They’ve enabled stretch and support and function that consumers have come to love. But they also are not recyclable at all. The technology doesn't exist.” The problem is particularly acute for women’s underwear, which usually has elastic fibers throughout, whereas men’s boxers often have an elastic band that’s easier to remove.

Underwear and other stretchy garments that arrive at textile-recycling facilities are thus rarely shredded; instead they’re repurposed into padding in products like car seats, punching bags and pet beds. Intimates brands that include New York City-based Knickey and Parade run take-back programs for this type of downcycling, and customers who turn in old undies get a discount or credit for their next purchase. But demand for that kind of insulation is far lower than the supply of excess garments, and other solutions are needed.

“We want all products to have an easy end of life, and for some areas that's more difficult and for intimates, that's particularly true,” says Michelle Tarry, vice president of responsible sourcing and sustainability at American Eagle Outfitters Inc., owner of the Aerie intimates brand. “It's the stretch. A lot of these products have spandex, which makes products more difficult to recycle.”

Spandex isn’t the only culprit. Most women’s underwear also contains polyester and nylon — increasingly prevalent in textile production as a cheap alternative to natural fibers like cotton. Some intimates have also been found to contain high levels of BPA and PFAS chemicals, which can be associated with endocrine disruption and prostate and breast cancers at high levels, according to Jimena Díaz Leiva, science director at the Center for Environmental Health.

“Another ancillary consequence of [materials like polyester and nylon] is they release microfibers into natural environments, both when you produce them in upstream production along with washing,” says Kibbe. “As they decompose, they release tremendous amounts of greenhouse gas emissions like methane into our ecosystems.”

Kent isn’t alone: A number of underwear retailers are looking for ways to reduce the environmental footprint of their products. Philadelphia-based The Big Favorite, which also makes its undergarments with 100% pima cotton, offers a take-back program and is working to recycle the cotton from used clothing into threads that would produce new garments, says founder and CEO Eleanor Turner. Intimates giant Victoria’s Secret & Co. is looking at ways to reuse scrap spandex in its products, while also researching biosynthetic materials made from corn and Tencel, a fabric derived from eucalyptus.

Underwear that can be composted is far from a silver bullet, and presents its own challenges. Most Americans don’t have access to a compost bin, and for the time being many municipal composts will only accept food scraps. Analysts have also expressed sanitation concerns over composted undergarments becoming part of a soil system that is also used to grow food.

Kent underwear composted through the company is used in regenerative farming, and CEO Stacy Grace says limited access to composting is why Kent invested in its own infrastructure. She also notes that one Kent customer made inroads in getting their undies accepted at municipal composts in Boston. But would-be buyers may still feel weird about dropping their underwear in a compost bin alongside banana peels and coffee grounds, and there’s an understandable discomfort baked into the idea of mailing back used underwear.

Even harder than recycling underwear: recycling a bra. That’s because bras contain tiny pieces of plastic and metal that have to be removed piece by piece, a labor-intensive and expensive process. Their padding is also typically made from polyurethane, which can’t be recycled.

Easier disassembly would help. One company called Resortecs makes heat-dissolvable stitching, for example, though at the moment it’s too expensive for most brands to implement at scale. And even that wouldn’t solve for the plastic clasps and wires.

“Those parts are very small and it would be a significant challenge for a facility to get the volume of those materials that justifies the cost of processing,” Kibbe says.

Unlike underwear, however, there is a market for secondhand bras. Aerie, for example, has a take-back program in over 400 stores that donates used bras to Free the Girls, a program that supports victims of sex trafficking. Victoria’s Secret is also piloting a take-back program in 14 stores in Florida for products other than accessories and underwear.

In addition to posing fewer sanitary concerns than underwear, bras tend to be far more durable. Indeed, while improving intimates’ recyclability will require innovation in both materials and disposal methods, at the moment focusing on durability may be the best way to keep undergarments out of landfills for longer.

“These items that typically people don't want to replace, they only replace them because they wear out,” says Laura Balmond, fashion lead at the Ellen MacArthur Foundation. “There should be a big focus on how you make things more durable.”

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Author: Olivia Rockeman