Natural fibers are often considered better for the environment than synthetic ones—a long-standing belief in sustainable fashion. But what if that isn’t true?
A new research paper, co-authored by Fashion Revolution co-founder Carry Somers alongside academic and citizen scientists, challenges the fashion industry’s assumption that natural fibers are inherently biodegradable.
Researchers took a sample from the sediment of Rudyard Lake in Staffordshire, UK—a lake fed by rivers historically lined with textile mills, dye houses, and laundries. They found that most of the fibers recovered were natural, with cotton making up over 70% of the fibers recorded over a 150-year period.
This study is the latest in a series over the past decade highlighting the persistence of natural fibers in the environment. It directly challenges the fashion narrative that natural materials like cotton are a better alternative to microplastic-shedding synthetics. Published in iScience, the paper addresses the industry’s use of natural fibers to make “green” claims and calls for sustainable fashion narratives to be guided by science, not assumptions.
“We have to move away from the extreme view that if plastics are bad, natural fibers must be good,” says Somers, whose recent book The Nature of Fashion explores how plants have shaped the industry.
A debate is raging between synthetic fiber producers, natural fiber advocates, campaigners, and policymakers over which type of fiber is less harmful to the environment. According to the Product Environmental Footprint (PEF) methodology—used in the EU to validate green claims—synthetics can have a lower environmental impact than some natural fibers like cotton. This is due to factors such as using less water and land, avoiding pesticides, and offering higher durability. However, critics argue this comparison overlooks key issues like the impact of fossil fuel extraction for synthetics, the renewable nature of natural fibers, and the potential benefits of regenerative agriculture.
In 2024, over 900 signatories representing more than 500,000 farmers worldwide warned that the PEF methodology risks misrepresenting natural fibers as harmful to the environment, threatening the livelihoods of natural fiber producers. Meanwhile, a 2026 paper by the Bremen Cotton Exchange criticized certain UN agencies for allegedly downplaying the impact of oil-based synthetics.
Consumer sentiment among those wanting to shop sustainably has often favored natural materials over plastic-based clothing. So, what should the industry and shoppers make of this new research? The authors clarify that the goal is not to exonerate plastics, but to avoid quick fixes—like simply swapping synthetics for natural fibers—that could lead to unexpected and more complex problems.
Tunnel Vision
As synthetic fiber production has grown to claim 69% of the global fiber market, and with the International Union for Conservation of Nature (IUCN) estimating that synthetic clothing is the leading contributor to ocean microplastics (accounting for 35% of releases), synthetic fibers have become a major focus of research and activism. Studies showing microplastics—tiny fragments including synthetic fibers shed from clothing—in nearly every environment tested, from lake beds and remote mountains to soils and sea spray, have raised significant concern. Research into the potential impacts is ongoing.The potential environmental damage—such as slowing algae growth, reducing soil fertility, and posing risks to human health—has heightened these concerns. In response to growing alarm over microplastics, the fashion industry has promoted solutions like microfiber-catching bags and washing machine filters, while also turning to natural fibers as a supposedly non-polluting, biodegradable alternative. However, unlike composting, which breaks materials down into organic matter within a specific timeframe under controlled conditions, textile biodegradation can occur over an indefinite period. This has led the EU to restrict the use of the term “biodegradable” without verification, and countries like France and Belgium to ban it in marketing. Yet many British and American brands, especially those marketing natural or “plastic-free” fibers, continue to use the label, arguing that natural fibers come from the land or animals.
But the idea that natural fiber clothing harmlessly returns to the earth may be overstated. Researchers point out that, despite the prevalence of synthetics, natural fibers actually make up the majority of fibers found in global seawater samples. Studies by Somers and others show that even after polyester emerged in the late 1970s, cotton remained the dominant fiber in lake sediments. This pattern holds across diverse environments, from penguin habitats in South Georgia to rivers in the UK.
Asha Singhal, director of the Nature of Fashion Initiative at the Biomimicry Institute, notes that textile fragments and microfibers enter countless environments—often shedding before they are even sold or worn. The wide range of places natural fibers end up challenges the assumption that they will biodegrade easily. “Biodegradation isn’t just about the material,” Singhal explains. “It depends on the surrounding ecosystem—factors like temperature, moisture, and the presence of the right microbes. A fabric might break down in an industrial composting test but persist for decades in a cold ocean or a nutrient-poor landfill.”
Dr. Thomas Stanton, a freshwater scientist and co-author of the iScience paper, adds that low-oxygen sediment conditions in places like Rudyard Lake contributed to the long-term preservation of fibers. “Over the 150-year timeline we studied, textile fibers certainly entered the lake and some eventually biodegraded. We’re not saying all natural fibers last a long time in the environment,” he clarifies. “But this study shows that in low- or no-oxygen conditions, natural textile fibers can persist long enough to have meaningful environmental or ecological impacts.”
This means that through shedding during production, wear, and washing—as well as improper disposal, landfilling, and pollution from the secondhand trade, like the clothing clogging beaches in Accra, Ghana—natural fibers can accumulate in environments where biodegradation is slowed, allowing them to linger and cause harm. The paper warns that excluding natural fibers from pollution research, and assuming they are harmless compared to plastic fibers, is potentially dangerous.
“Fashion is participating in a giant, uncontrolled experiment with ecology,” says Deirdre McKay, co-author and professor of sustainable development at Keele University.
Overlooked Impacts
Discussions about the benefits of natural fibers often overlook that these products are not pure, raw materials taken directly from nature. Finished textiles—regardless of their composition—are typically dyed and heavily treated with chemicals to achieve qualities like durability and softness.Treatments that improve durability can make fibers less biodegradable; a raw fiber will typically degrade faster than one that has been dyed or finished. Even natural dyes are not automatically a solution, as some can contain heavy metals or harm soil health. Testing is always necessary, according to the Stella McCartney team. The brand includes materials in its collections that claim to be biodegradable, such as natural fibers like silk and innovations like the fur alternative Savian and plastic alternative BioCir Flex.
However, the brand only claims biodegradability at the material level, based on fiber or fabric testing, not at the product level, because each component in a garment or bag breaks down differently. Whether consumers understand this nuance is another question. The brand says its priority is extending product life through repair, reuse, and resale, and it handles questions about disposing of biodegradable products individually. Given the confusion around biodegradability, clearer communication may be needed to avoid potential environmental pollution. Beauty brands like Dulcie (formerly Haeckels) offer an example of proactive end-of-life messaging, providing specific guidance for composting, biodegrading, returning, or recycling each product.
Sparxell, a Cambridge-based color technology company that raised $5 million in pre-seed funding in February, aims to help brands create biodegradable products without sacrificing color or finish. Used by designer Patrick McDowell, Sparxell is a cellulose-based pigment, not a dye, which is printed onto garments. It is shipped as a powder for use in existing printing processes. “We use the same material that nature uses to make vibrant colors, like in butterfly wings or beetle shells. Nature recognizes it as natural cellulose, so it biodegrades completely,” says founder and CEO Benjamin Droguet.
The Nature of Fashion Initiative is taking a holistic approach in its research, working backward from decomposition. Partnering with innovators like Netherlands-based EV Biotech and non-profit The Or Foundation, it is piloting decomposition technologies that could transform complex textile waste into materials that can re-enter natural cycles, mimicking natural processes.
Many brands simply assume, often incorrectly, that their natural fiber-based products will biodegrade. Others have taken a more scientific approach to ensure this is the case. Accessories brand Anya Hindmarch released a Return To Nature collection of leather goods after two years of research and development.
“The collection is designed to biodegrade, compost, and return to the earth, nourishing the soil at the end of its life,” says founder Anya Hindmarch. To ensure biodegradability at the product level, all products are made without hardware and coated with natural wax oils instead of synthetic polyurethane and acrylics. At the material level, the leather is tanned with Zeology, a chrome-free and heavy metal-free tanning agent developed by Dutch company Nera Tanning, avoiding one of the most toxic parts of leather production. “In testing, when industrially composted, the leather was found to nourish the soil, producing 20% stronger plant growth than a control compost. It biodegraded only 10% slower than pure collagen, meaning it breaks down nearly as quickly as untanned skin,” says Hindmarch.
Testing was conducted externally according to International Organization for Standardization (ISO) standards.To confirm biodegradation, scientists measure the carbon dioxide released as bacteria and fungi consume organic materials. The authors of the iScience paper advocate for this method, which specifically tests for the signals of biodegradation. They caution that visual tests—often used by brands on sustainability pages and social media to show a product disappearing over time—can be misleading.
“There’s a difference between breaking up into smaller and smaller pieces, which is what chunks of plastic do on beaches, and breaking down, in the biodegradable sense, into carbon dioxide and water,” says McKay.
In contrast to Hindmarch’s low-input approach and the broader trend toward natural materials, the fashion and materials science company Pangaia used AeoniQ yarn from Swiss chemistry company HeiQ to create its biodegradable collection, released in October 2025. (Like Stella McCartney, the brand has verified biodegradability at the fiber level, not the whole product level.) The cellulosic yarn is made from inputs like wood pulp, textile waste, and agricultural waste.
“While many textiles today may come from renewable sources, that doesn’t necessarily mean they are able to break down naturally at end-of-life. Through partnerships with material innovators, we explore and apply materials that have been developed with biodegradability considerations,” Pangaia Collective said via email. According to the brand, claims of biodegradability in industrial and home composting, soil, water, and marine environments have been certified by TÜV Austria and Oeko-Tex per HeiQ, with parameters like temperature, microbial activity, and oxygen availability considered to reflect realistic conditions.
The fact that fibers from a 100% cotton T-shirt may persist in the environment for decades—while those from a highly processed, polyester-like yarn may not—highlights the nuance in the natural versus synthetic materials debate. However, the co-authors suggest that the scientific community and the fashion industry should view this research as an opportunity to build an evidence base for more informed decisions, rather than seeing it as an inconvenience. “I think it’s so important that we start to engage with that complexity,” says Somers.
“Research that challenges assumptions is essential for progress,” adds the Stella McCartney team.
Frequently Asked Questions
Of course Here is a list of FAQs about what happens when natural fibers dont break down written in a natural tone with clear direct answers
Basics Definitions
1 Wait I thought natural fibers always broke down Dont they
Not always While fibers like cotton wool and linen come from plants or animals and are biodegradable in theory they often dont break down properly in modern landfills or when mixed with synthetic materials
2 What does break down or biodegrade actually mean here
It means microorganisms like bacteria and fungi can digest the material turning it into water carbon dioxide and organic matter that safely returns to the earth
3 What are some common natural fibers
Cotton linen hemp jute silk and wool
Common Problems Consequences
4 Whats the main reason a natural fiber item wouldnt break down in a landfill
Landfills are designed to be dry and airtight to prevent contamination This mummifies trash instead of letting it decompose Without oxygen moisture and microbes even a cotton tshirt can sit for decades largely intact
5 What if I just toss it in nature like out a car window
Please dont Littering is harmful An apple core might decompose quickly but a cotton sock or a hemp bag could take months or years during which it can be eaten by animals leach dyes or simply pollute the landscape
6 Does blending natural fibers with synthetic ones cause a problem
Yes this is a huge issue A 50 cotton 50 polyester blend shirt wont biodegrade properly The synthetic fibers dont break down and can contaminate the composting process leaving behind microplastic fragments
7 What about dyes chemicals and finishes on the fabric
Many conventional fabrics are treated with chemical dyes formaldehyde or waterproofing These chemicals can leach into the soil or water as the fiber breaks down causing pollution
8 So if it doesnt break down is it just like plastic
Its not the same as a plastic bag that lasts for centuries but the