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“Sustainable Textiles”: what are next-gen materials, biobased materials and recycled materials? (When is a material truly recycled?)

By Esmee Blaazer


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Here is an example of sustainable textile innovation from the fashion sector: Danish clothing brand Ganni collaborated with Polybion to create a new "bio-leather" blazer made entirely from Celium™, a new material made from bacterial cellulose (July 2023 news) Credits: Polybion

“About two-thirds of the raw materials used in the fashion industry are synthetic materials.

Synthetic materials, also known as artificial or man-made fibers, are basic materials made by humankind in factories. Unlike cotton and wool, for example, these fabrics do not come from nature.

But not everyone knows that synthetic fibers come from fossil-fuel-derived resources,” poses Paulien Harmsen, Senior Scientist Sustainable Textiles at Wageningen University and Research.

Paulien Harmsen is a Senior Scientist Sustainable Textiles. She has been working at Wageningen University and Research (WUR) for 25 years on various projects in the field of biobased materials 'in the broadest sense of the word.' She says that her work aims to see how we can phase out fossil resources.

Harmsen turned her attention to the textile industry about six years ago, a sector she has a personal affinity for, in part due to her interest in making clothes. She explains that in pursuing this hobby, she noticed that there were few beautiful, natural fabrics on the market, when sustainability was becoming a prominent topic of conversation within the fashion industry. This led her to decide to specialize in ‘sustainable textiles.’.

"When we talk about the raw materials of clothing, there is almost always a picture of a cotton plant," illustrates Harmsen. "You almost never see an oil barrel, even though that is more often the reality." Polyester, for example, is made from a polymer from petroleum, more commonly known as crude oil.

Polyester has a prominent position in the fashion industry

Polyester has become increasingly popular: its use within the fashion industry has increased greatly, especially in the past decades.

According to Textile Exchange, a global nonprofit organization dedicated to sustainability in the textile industry, polyester represented 54 percent of total fiber production worldwide in 2022. This makes it the most widely used fiber. Source: Textile Exchange's Materials Market Report 2023 released December 1.

Polyester is particularly prevalent in the collections of major fashion retailers. The raw material is relatively inexpensive. Polyester is strong (and therefore long-lasting), versatile (it can be used for almost any type of garment), and looks beautiful (for example, polyester is smooth and wrinkle-resistant). Polyester is also predominantly found in sports and outdoor clothing due to its lightweight feeling, quick-drying properties, and naturally water-resistant capabilities.

But at the same time, the frequent use of polyester causes several issues. For one, the production of this synthetic raw material is largely dependent on oil. Oil production is a huge burden on the environment, particularly due to the polluting effects of the refining process. Polyester production is also very energy-intensive and requires large amounts of water and chemicals. On top of that, polyester also causes plastic and microplastic pollution.

During the production process and later on also in the use phase (wearing and washing), synthetic garments release tiny particles of plastic called microplastics. As many as 1,900(!) microfibers can come off one synthetic garment per wash. Worldwide, as many as 35 percent of all microplastics released into the environment can be traced back to textile products. And it's not just turning our oceans into plastic soup. Microplastics have been found in our drinking water and food as well as the human body.

[Source: Article'How (not) sustainable is the fashion industry?']

Read more here: ‘What the fashion industry has to do with microplastics pollution (and everything you need to know about EU initiatives to tackle microplastics) ’

Polyester is, therefore, both a pet project and a problem case within the fashion industry. There are also several other commonly used synthetic raw materials, such as polyamide (of which nylon is the best-known example) and acrylic (an artificial alternative to wool).

"The fashion industry actually needs a materials transition," argues Harmsen. "We need to scale back the use of fossil-fuel based synthetic materials and switch to materials that are less harmful to the environment or more sustainable alternatives. Compare it to the energy transition, where we have to say goodbye to gasoline and diesel."

“What are good alternatives [to fossil-fuel based synthetic materials] is, of course, the next question," continues Harmsen. "A question that’s not easy to answer, but for example, you can look to biobased materials or recycled content."

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Image illustrating recycled polyester. Credits: Adidas.

1. The truth about recycled polyester - Why we should be critical of recycled polyester

How sustainable is recycled polyester? Is recycled polyester truly better for the environment? What is rPET or bottle-based polyester? When is a garment genuinely considered to be truly recycled or recyclable?

Nowadays, you increasingly encounter garments made from recycled polyester, also known as rPET, which tends to be promoted as a more sustainable choice.

However, whether recycled polyester is more sustainable, and if so, to what extent, is debatable. "I have my reservations," says Harmsen.

Recycled polyester is usually made from PET bottles, meaning old plastic bottles. "It's not that old polyester clothing is turned into new clothing," the expert emphasizes. "That's one of the biggest misconceptions about recycled polyester."

Discarded/unwanted clothing is rarely made into new clothing. Less than 1 percent of used textile waste is made into new apparel.

This percentage is still cited when discussing the amount of old clothing recycled into new in the fashion industry and beyond. However, bear in mind that this percentage comes from a 2017 report by the Ellen MacArthur Foundation, an international organization dedicated to promoting the circular economy through research, education, and collaboration with businesses and government agencies.

"Given the current recycling activities, the current percentage (six to seven years later, ed.) may be higher," points out Harmsen, "although we don't really know for sure."

The fashion industry struggles from time to time with incomplete information regarding sustainability. Vox.com and De Correspondent previously published interesting articles on this topic, and I, the author of this piece, have experienced this firsthand while writing background articles like this one.

If a garment is (partially) recycled and contains polyester, it usually contains bottle-based polyester: plastic bottles from the food industry.

"That these plastic bottles come from a completely different chain is actually undesirable," says Harmsen. "In the original production chain, the bottles are continuously recycled and refilled with beverages." When they are used for the production of recycled polyester for textiles, they disappear from the original cycle.

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Image for illustration. Credits: plastic bottles (source: FU news archive)

"The PET bottles used for textiles eventually become lost material, ending up as trash" continues Harmsen. rPET no longer gets a new life as clothing, and recycled polyester clothing also does not get turned into new bottles. This form of recycling is called 'open loop recycling' or 'downcycling'. The fashion industry should actually aim for a closed-loop recycling system, where materials are recycled within the same production chain and reused for the same purpose over and over. In other words, 'textile-to-textile recycling.' Unfortunately, as you now know, this still happens very rarely.
In open-loop recycling, materials are recycled for a different purpose than they were originally intended, preventing them from returning to the same production chain.

Recycled Polyester? Greenwashing Alert!

The EU has also expressed concerns about claims regarding recycled polyester, as stated in the policy document 'EU Strategy for Sustainable and Circular Textiles,' an initiative by the European Union to promote sustainability and circularity in the textile industry.

Claims about recycled polyester can mislead consumers and hinder the effective reuse of PET bottles, according to the European Commission.

The good news is that the EU is going to further regulate greenwashing - making things appear more sustainable than they actually are - much more tightly.

‘Textile-to-textile recycling’: Why is such a small percentage of discarded clothing recycled into new? What challenges does textile recycling face?

"For recycling, the input stream must be as clean and pure as possible," says Harmsen. "Take the glass and paper sectors. For years, these materials have been collected separately, and their recycling processes work quite well because they are pure materials."

And that is precisely the bottleneck in the fashion industry: modern garments often consist of a mix or blend of different fibers.

"Most garments consist of at least two, three, or four different raw materials," explains Harmsen. According to her, this blending (the industry term for mixing raw materials and fibers for one garment, ed.) is something that has really emerged over the last twenty to twenty-five years. "I think that this is a direct result of the strong growth of synthetic materials in global fiber production during the same period. When I used to buy a pair of jeans, they were just made of 100% cotton, a completely natural material. Now, when you buy jeans, they contain synthetic fibers like elastane or semi-synthetic fibers like viscose."

"If you look at the past twenty to twenty-five years, the production of synthetic fibers has increased significantly. The demand for and use of natural fibers like cotton and wool have remained more or less the same," says Harmsen.

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Image illustrating the composition of our clothing. This photo shows a clothing label of a pair of H&M jeans made from cotton, viscose, and elastane. Credits: FashionUnited

Collected, discarded textiles are "just a big mix of everything and anything." More elegantly put: "The problem is that there are not many 'clean' streams that can be directly used as input for recycling factories. And that makes textile recycling initiatives difficult to get off the ground," says Harmsen.

This mix of materials also makes recycling very complex. In recycling, you have to go back to the basics: the raw materials and fibers. "So even if you want to recycle a cheap fabric like polyester, advanced technology is needed," emphasized Harmsen. "And that is expensive."

Recycling processes are generally divided by type of raw material because each material requires specific methods for processing and reuse.

And then there's another challenge: how do you ensure quality? "When you mechanically recycle clothing, it gets turned into fibers. This degrades the quality," explains Harmsen. "To ensure that new garments have both the desired appearance and the necessary properties, new fibers are almost always added." That, in turn, drives up the cost further.

Recycled fibers are usually more expensive than virgin (read: new) materials. According to Harmsen, the price difference between recycled fibers and new raw materials is an obstacle to scaling up in the textile industry. "The recent bankruptcy of Renewcell, an innovative Swedish company specializing in textile-to-textile recycling, is a clear sign of this."

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Image illustrating recycling. Credits: Photo by Alicia Reyes Sarmiento for FashionUnited, taken during a visit to the Dutch textile recycling facility Brightfiber Textiles and Loop.a life.

According to the expert, the industry needs to take action now, and the use of mono-materials will only facilitate textile recycling. "A garment made of 100 percent cotton or 100 percent polyester is easier to recycle," says Harmsen.

But a market for recycled materials also needs to be created, points out Harmsen. Policymakers could help with this. Again, synthetic raw materials have many attractive properties and are also cheap. "So, something will have to be done about prices if we want to reduce the use of fossil-fuel based synthetics,'" says the expert.

"In any case, clothing is too cheap," stresses Harmsen. "To my knowledge, there are no machines where you put in a piece of fabric, and out comes a shirt." Turning a piece of fabric into a garment takes time and always requires manual labor. This is something that should be more valued, she believes. "With the low prices of clothing, we maintain the idea that a garment is not worth much, along with the current throwaway culture."

At the same time, our addiction to clothing needs to be addressed, according to Harmsen. "The volumes we are accustomed to now (read: the massive amounts of clothing being produced and consumed, ed.) are not sustainable. The earth is simply too small for that."

Harmsen further believes that the industry should be more mindful of the raw materials available ("we should be frugal with cotton, for example, because of its unique properties") and, in addition to recycled fabrics, make greater use of biobased materials.

Harmsen: “If we take a look at what was worn in the past, we can see the possibilities nature offers us.”

2. What are biobased materials?

Biobased materials are (partially or fully) derived from biological sources such as plants, animals, or microorganisms and are produced using renewable natural resources instead of fossil-fuel based materials. They offer a sustainable alternative to traditional materials in various industries, including fashion.

"In the past, before polyester and nylon existed, we also wore clothes,” says Harmsen. “And those materials will still be around in the future - without fossil-fuel based synthetics,” she stresses.

Harmsen sees a future in synthetic materials, but not in fossil-fuel based synthetic materials, she stresses for clarity. Synthetic materials offer properties that natural fibers typically cannot. “It is now up to us to develop [more sustainable] synthetic materials that are both biobased and do not release microfibers that do not break down in nature,” explains the expert.

Regarding animals, you can think of various types of wool and hair fibers, as well as animal hides. “The latter is not textile,” says Harmsen, “but as long as we consume meat, there will be hides and skins to work with.”

For plant sources, you can think of bast fibers found in the stems of plants. Examples include linen, hemp, nettles, and ramie.

Nature is also a source for making semi-synthetic and (fully) synthetic materials, the scientist explains.

For example, there are natural building blocks, cellulose, present at the polymer level of plants, says Harmsen. “You can use these to create new semi-synthetic materials like viscose and lyocell.”

It is even possible to make biobased synthetic materials, continues the expert. "For that, you need chemical building blocks, which can be derived from sources like sugar beets or corn." A specific example is PLA (polylactic acid), which is used in sportswear.

3. Next gen materials: an emerging trend of innovative materials

Furthermore, there are also several innovative developments underway, says Harmsen. These unconventional raw materials are referred to as next gen materials (short for the next generation materials).

"We are now quite familiar with animals and plants (see paragraph 2, ed.), but the potential of fungi, for example, is not yet well known," says Harmsen. The sector is currently experimenting on a small scale with 'mushroom leather'. "It is still very niche but promising," believed Harmsen. "Fungi grow quickly and can also decompose in nature." She sees a future in it.

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An example of a next-gen material: biomaterial mushroom leather from MycoWorks. MycoWorks cultivates mycelium (fungus roots) for 'luxury leather.' Credits: MycoWorks, Lindsey Filowitz.

What’s next? Looking to the future
Sustainable textile expert looks ahead

Awareness and increasing action within the industry

“Alongside innovation (see paragraph 3, ed.) in the sector, you can see that more sustainable fibers/materials are becoming increasingly popular among smaller companies in the industry and also among end consumers,” says Harmsen. “It’s a clear trend.” The materials transition has thus already begun. “It may be slow, but the beginning is there,” notes Harmsen.

Responsible business practices are also high on the EU's agenda, she emphasizes. Many laws are in the pipeline to promote sustainability: addressing issues such as greenwashing, waste/destruction, and fast fashion.

Requiring more transparency will also further improve matters, the expert believes. “Currently, fashion companies can purchase materials without being in direct contact with the primary parties in the textile supply chain - such as cotton farmers, for example.”

In conclusion, she focuses on what’s to come. “When more fashion companies in the industry start working with materials other than fossil-fuel based synthetics, it might take some getting used to (since the appearance and properties of garments depend, among other things, on the fibres used. Polyester is generally smoother and shinier than viscose, for example, ed.),” Harmsen concludes. “However, I am confident that they will continue to create beautiful things. After all, the textile industry is synonymous with creativity.”

Next gen material Mirum from Natural Fiber Welding (a plant-based Leather alternative) Credits: Pangaia Lab; Pangaia and Natural Fiber Welding air-gilet made from Mirum and Flwrdwn
Background: How do fashion brands actually choose which textile fibers to use for their garments?

"It depends," said Monique Wertheym, a textile specialist at Detex and TMO Fashion Business School lecturer, in a previous interview. "Most fashion brands are design-driven. In that case, styling determines the look of a fashion collection. Then the sourcing manager or product developer says, 'If you want the collection to look like this, I need these raw materials/fibres.'"

For fashion companies that are purchase or price-driven, it's the other way around. "In that case, they say, 'I need something warm for the winter.' A clothing brand in the lower price segment will then choose acrylic, while one in the higher price segment will choose mohair or cashmere," according to Wertheym.

Read more about raw materials and the ‘technical construction’ of garments in the background article ‘From Fiber to Garment’.

- Interview with Paulien Harmsen, Senior Scientist Sustainable Textiles at Wageningen University & Research (WUR), on March 25, 2024.
- The report ‘Materials Market Report 2023’ by Textile Exchange, published on December 1, 2023
- The report 'A New Textiles Economy: Redesigning fashion’s future' by the UK sustainability think tank Ellen MacArthur Foundation, published in 2017.
- European Commission briefing 'EU Strategy for Sustainable and Circular Textiles,' from Brussels, dated March 30, 2022,
- The FashionUnited archive.
- Some parts of this article were generated using an artificial intelligence (AI) tool and then edited.

Stella McCartney is a prominent name in the fashion industry known for choosing sustainable and animal-friendly raw materials. The fashion designer never works with leather or fur. In her Spring/Summer 2024 collection, she presented accessories 'made from by-products of Veuve Clicquot's champagne production.' It is an alternative to animal leather made from grapes. Credits: Stella McCartney & Veuve Clicquot (press release April 16, 2024, via Tandem.be).
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