Natural fibers are better for the environment than synthetics — at least, that’s been a long-held tenet of fashion sustainability. But what if that’s not the case?
A new research paper, co-authored by Fashion Revolution co-founder Carry Somers alongside both academic and citizen scientists, challenges fashion’s historical assumptions that natural fibers are inherently biodegradable.
In a sample taken from the sediment of Rudyard Lake in Staffordshire in the UK — long fed by rivers lined with textile mills, color mills, laundries, and dye houses — researchers found the majority of fibers recovered were natural, with cotton accounting for over 70% of the 150-year fiber record.
The research is the latest in a string of papers from across the last decade that have highlighted the staying power of natural fibers in the environment. It’s a direct blow to fashion’s narrative that natural materials like cotton are better alternatives to microplastic-shedding synthetics. The new paper, published in iScience, directly addresses fashion’s use of natural fibers to make ‘green’ claims, and specifically calls upon the industry to heed the results to ensure sustainable fashion narratives are led by science, not assumption.
“We have to get away from this extreme that if plastics are bad, natural [fibers] must be good,” says Somers, whose recent book The Nature of Fashion investigates how plants have shaped fashion.
A battle rages between synthetic fiber producers and natural fiber producers, campaigners, and activists and policymakers as to which fiber category is less harmful to the environment. According to the Product Environmental Footprint (PEF) methodology — used as the basis for validating green claims in the EU — synthetics have a lower environmental impact than certain natural fibers such as cotton, due to factors including using less water in production, requiring less land, not requiring the use of pesticides, and higher durability. This position is fiercely debated, with critics arguing that such comparisons overlook key points such as the impact of fossil fuel extraction and processing for synthetics, the renewable nature of natural fibers, and the potential benefits of regenerative agriculture.
In 2024, more than 900 signatories representing over 500,000 farmers globally stated that the PEF methodology posed a significant risk to the livelihoods of natural fiber producers by “misrepresenting natural fibers as harmful to the environment”. Meanwhile, a 2026 paper published by the Bremen Cotton Exchange took aim at how select UN agencies allegedly underplay the impact of oil-based synthetics.
An EU Green Claims Directive proposed by the European Commission intended to stop greenwashing, may play to the advantage of producers of synthetic fibres, say farmers. There’s a great deal at stake.
Consumer sentiment among those wanting to shop more sustainably has been to avoid plastic-based clothing in favor of natural materials. What should the industry — and shoppers — make of this new research? The authors say that the intent is not to exonerate plastics, but to avoid the risk of seemingly quick fixes such as swapping synthetic for natural fibers leading to unanticipated and more complex problems.
Tunnel vision
As the production of synthetic fibers has grown to take 69% of global fiber market share, and International Union for Conservation of Nature (IUCN) estimates place synthetic clothing as the leading single contributor to ocean-based microplastics — accounting for 35% of what’s released — synthetic fibers have become a major focus of research and campaigning. Studies showing that microplastics (tiny plastic fragments, including synthetic fibers, which have shed from clothing) have been found in almost every environment tested, from lake beds and remote mountain ranges to soils and sea spray, raised concern. Research into the potential environmental harms, such as slowing the growth of algae and making soil less fertile, not to mention the potential impact on human health, further compounded that concern.
Alongside promoting interventions such as microfiber-catching bags and washing machine filters, the fashion industry’s answer to growing fears about the impact of microplastics has been to lean on natural fibers as a purported non-polluting, biodegradable alternative. Unlike composting, which means breaking down into organic matter within a set timeframe in either home or industrial conditions, biodegradation of textiles can happen over an unspecified timeframe, leading the EU to prohibit the use of the term without validation (because an item isn’t guaranteed to break down into an organic matter in imperfect conditions), and member states including France and Belgium to ban the term in marketing. Yet many British and American natural fiber and ‘plastic-free’ brands, in particular, continue to use the term, citing the basic fact that natural fibers are harvested from the land or animals to support their claims.
But ideas of clothing made from natural fibers returning to the earth and leaving no trace could well be overstated, according to researchers. Despite the dominance of synthetic fibers, the majority of fibers found in seawater samples globally are, in fact, natural. Somers and her fellow researchers found that even after 1979, when polyester fibers first appear in the sample, the majority of fibers in the lake sediment were still cotton. The trend continues in studies in various environments including penguin habitats in South Georgia and UK rivers.
Textile fragments and microfibers end up in countless environments, often shedding before they reach the bin, or even before they reach the consumer, says Asha Singhal, director of the Nature of Fashion Initiative at the Biomimicry Institute. The sheer variety of environments where natural fibers end up poses yet another challenge to the assumption of biodegradation. “Biodegradation is not just about the material itself. It depends on the ecosystem around it, from temperature and moisture to the presence of the right microbes. A fabric might break down in an industrial composting test, yet persist for decades in a cold ocean or a nutrient-poor landfill,” says Singhal.
Dr. Thomas Stanton, a freshwater scientist and co-author of the iScience paper, says that the low-oxygen sediment environment played a part in the long-term fiber preservation in Rudyard Lake.
“There’s no doubt that over the 150-year timeline we’re looking at, textile fibers will have entered the lake and ultimately biodegraded. We’re not saying all natural fibers will persist in the environment for a very long time,” he says. “What this study is highlighting is that in lower and [no-oxygen] conditions, natural textile fibers have the potential to persist over a timescale that might be environmentally or ecologically meaningful.”
This means that through shedding during processing, wearing, and washing; improper disposal; landfilling; and pollution from the secondhand industry — such as that seen on the beaches of Accra, Ghana, which is clogged with unwanted clothing — natural fibers can end up in various environments that hinder biodegradation and exist long enough to cause harm. Excluding natural fibers from pollution research and assuming they will not cause environmental harm alongside their plastic counterparts is potentially dangerous, the paper warns.
“Fashion is participating in a giant, uncontrolled experiment with ecology,” says Deirdre McKay, co-author and professor of sustainable development at Keele University.
Unknown harms
Often, conversations about the merits of natural fibers fail to acknowledge that the products in question are not pure raw materials extracted from natural sources. Finished products — no matter the composition — are typically dyed and heavily treated with chemicals to ensure qualities like durability, softness, and water repellence.
“Treatments that improve durability can make fibers more resistant to [biodegradability]; a raw fiber will typically degrade faster than one that has not been dyed or finished. Even natural dyes are not automatically a solution, as some can contain heavy metals or affect soil health. Testing is always necessary,” the Stella McCartney team told Replica Handbag Store Business via email. The brand features a selection of materials that claim to be biodegradable within its collectsions, including natural fibers such as silk, and material innovations including fur alternative Savian and plastic alternative BioCir Flex.
However, it only claims biodegradability at the material level based on fiber or fabric testing rather than at the product level, because each component in a garment or bag will break down differently. Whether this nuance lands with consumers is another question. The brand says its priority is extending product life through repair, reuse, and resale, and that it handles requests for what consumers should do with biodegradable products on a case-by-case basis. Given the confusion around biodegradability, however, more direct communication may be warranted to avoid potential environmental pollution. Beauty brands such as Dulcie (formerly Haeckels) offer a blueprint for what proactive messaging around end-of-life could look like. It provides product-by-product guidance for composting, biodegradation, returning, and recycling.
Sparxell, a Cambridge-based color technology company that raised $5 million in pre-seed funding in February, aims to enable brands to create biodegradable products without holding back on color or finish. Used by Patrick McDowell, Sparxell is a cellulose-based pigment, rather than a dye, which is printed onto garments and shipped as a powder to be used within existing printing processes. “We use the same material that nature uses to make vibrant colors around us [such as] butterfly wings, or beetle shells. Nature recognizes it as the cellulose you would find in nature, and therefore it biodegrades fully,” says founder and CEO Benjamin Droguet.
The Nature of Fashion Initiative is taking precisely such a holistic approach in its research — but working from decomposition backward. Partnering with innovators such as Netherlands-based EV Biotech and fashion development non-profit The Or Foundation, it is piloting decomposition technologies that could transform more complex textile waste into outputs that can reintegrate into natural cycles, mirroring natural processes.
How brands are responding
Many brands simply assume, often wrongly, that their natural fiber-based products will biodegrade. Others have taken a more scientific approach to ensure this is actually the case. Accessories brand Anya Hindmarch released a Return To Nature collectsion of leather goods after two years of research and development.
“The collectsion is designed to biodegrade, compost, and return to the earth, nourishing the soil at the end of its useful life,” says the brand’s namesake founder. Measures to ensure biodegradability at the product level include making all products hardware-free and coating them with natural wax oils rather than synthetic polyurethane and acrylics. At the material level, leather is tanned with Zeology, a chrome-free and heavy metal-free tanning agent developed by Netherlands company Nera Tanning, side-stepping one of the most toxic parts of the leather-making process. “In testing, when industrially composted, the leather was found to nourish the soil, delivering 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 carried out externally, according to International Organization for Standardization (ISO) standards, measuring the carbon dioxide that is released when bacteria and fungi consume organic materials to confirm biodegradation. The iScience paper co-authors advocate for such an approach that specifically tests for the signals of biodegradation. Visual tests — often used by brands on sustainability pages and social media to show how a product disappears over a certain amount of time — can be misleading, they say.
“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.
Contrary to Hindmarch’s low-input approach and the broader sway toward natural materials, fashion and materials science company Pangaia turned to AeoniQ yarn from Swiss chemistry company HeiQ to make its biodegradable collectsion, released in October 2025. (Like Stella McCartney, the brand has verified biodegradability to the fiber level rather than the whole product level.) The cellulosic yarn is made from inputs including 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. 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 such as temperature, microbial activity, and oxygen availability considered to reflect realistic conditions, according to Pangaia Collective.
That the 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 — shows the nuance at play in the natural versus synthetic materials debate. But the scientific community and the fashion industry should view the research as an opportunity to build an evidence base for more informed decisions rather than seeing it as an inconvenience, the co-authors say. “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.
