"Biodegradable" Polyesters: Are They For Real?

An update: I was a little bit too gullible before.

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We use way too much polyester in our fashion, that is a fact.

No, nobody needs a polyester sundress, button down, or pajamas. But it’s also a fact that we haven’t yet found a natural, plastic-free way to make a performance sneaker or a lightweight hiking jacket. So even the most outdoorsy climate scientists are currently stuck with at least some synthetic clothing.

In 2024, 28% of post-consumer garments in the U.S. were primarily polyester. And all of those materials are going to the landfill, being burned, or ending up in the environment. (Hello, Ghana.)

There are promising technologies emerging to chemically recycle synthetic fabrics. However, when or if these technologies are scaled, there is a good chance they will still only take in pre-consumer textiles, a.k.a. off-cuts from factories. Clothing is too mixed and chaotic to profitably recycle. In the landfill it will continue to go.

And then, we have the problem of microfibers. When washed, synthetic materials release microfibers into the wastewater treatment system and to septic fields. From there, they are either released with “purified” water into waterways, or stay a part of wastewater sludge, which is eventually applied to large farms as fertilizer.

When worn or used, synthetic materials also release microfibers into the air or into the home, where they accumulate in house dust, so we breathe them in and ingest them.

Microplastics have been found in our bowels, blood, placentas, lungs, and testes. Scientists are just at the beginning of researching the myriad potential health effects of microplastics on our bodies — from cancer, heart disease, and kidney disease; to Alzheimer’s, chronic bowel disease, and fertility.

What’s worse, according to Susanne Brander, an associate professor and ecotoxicologist at Oregon State University, micro and nanofibers are more toxic than microplastics that come in other shapes, such as pellets or beads. “That has been shown in a number of studies,” she says.

Okay, so polyester and nylon aren’t being recycled, are ending up in our oceans and soil, and their microfibers are especially toxic. What if we could make them biodegradable? Voila: there are at least five different companies who have created a synthetic fiber with an additive that makes it break down in the presence of bacteria.

Intrinsic Textiles Group invented the technology behind CiCLO, a proprietary chemical resin mixture that added to polyester or nylon at the factory. It has “biodegradable spots” throughout that attract bacteria that purportedly break it down completely. It’s manufactured in North Carolina.

PrimaLoft Bio, which is marketed as a more sustainable fill for puffy coats, uses recycled PET water bottles and adds another proprietary mix of additives to make it appetizing to microbes.

There’s Amni Soul Eco, a polyamide (nylon) with an additive that is supposed to help it biodegrade within five years in the landfill, and ROICA V550, a partially degradable elastane stretch fiber.

CELYS Compostable Polyester by Intimiti, a company based between Sydney and Shanghai, inserts a chemical in the PET manufacturing process to create “hydrolysable linkages in the polymer backbones, thus greatly accelerating the whole biodegradation rate.” In other words, the polyester breaks down more quickly in the presence of water than regular polyester. It’s manufactured by polyester manufacturers in China.

After an initial flurry of brand announcements and product launches using these “biodegradable” polyester products several years ago, large brands haven’t incorporated these innovations into their general product line.

Something is up.

I dug into the science, interviewed researchers, and had multiple long conversations with these innovators and their scientists to understand what exactly is going on here.

So, can you have your polyester performance gear and biodegrade it too? Let’s find out.