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What are bio-based fibers and what can they do?

By Regina Henkel


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En route to the post-fossil age, conventional, petroleum-based synthetic fibres have long been counted out. But what alternatives are there, which innovations are actually more sustainable and how will the consumption of synthetic fibres develop in the coming years? FashionUnited asked outdoor supplier and sustainability pioneer Vaude.

The current outdoor industry would be inconceivable without synthetic fibres. The vast majority of functional materials are based on synthetic man-made fibres such as polyester and polyamide. How could this change? Outdoor supplier and sustainability pioneer Vaude has just launched a pair of trekking pants made from bio-based polyamide. The yarn used consists of 62 percent castor oil and was developed together with polymer specialist Evonik. Does the future belong to bio-based plastics in the clothing industry? We talked about it with René Bethmann, innovation manager at Vaude.

Mr. Bethmann, what exactly are bio-based fibres or fabrics?

René Bethmann: In short, these are bioplastics or biopolymers. And as far as the current hype is concerned, I find it interesting that plastics have originally always been biobased; rubber for example. Plastics made from petroleum only came along later.

There are quite different bioplastics or biobased fibres out there. How does one distinguish between them?

There is a basic distinction between two approaches: The beginning-of-life, in which case the material origin is biobased, or the end-of-life, in which case the finished material is biodegradable. There are actually also bioplastics that are made from crude oil but that biodegrade quickly. Similarly, plastics made from biobased raw materials such as plants or food waste are not necessarily biodegradable. Chemically, the only way to distinguish between the two variants is to determine the age of the carbons: fossil carbons are very old, while carbons from sugar beets, for example, are much younger.

If one changes the starting material, do the properties of the fibres also change?

That is the exciting thing: In principle, one can develop completely new plastics or replace fossil plastics with bio-based plastics or “rebuilt” them. In the first case scenario, new properties can be achieved that may even be better than those of the original material that one was trying to replace.

Which bioplastics are more suitable for the textile industry?

Fossil-based and biodegradable bioplastics tend to play a minor role in the textile industry because they have a life span that is too short. In my view, rapid biodegradability is only sustainable to a limited extent anyway, because the carbon bound in the material is quickly released again. Recyclability is also only of limited use here, so the carbon is not bound for a long time either. Biodegradability only makes sense for countries that dispose of their waste exclusively in landfills, do not burn it and do not recycle it - although a recycling infrastructure should always be strived for.

We are therefore focusing on bioplastics that have a bio-based material origin and are thus trying to replace fossil plastics. Our goal at Vaude is to use almost exclusively renewable or recycled raw materials from 2024 onwards. The ideal scenario would be a bio-based post-consumer recycled plastic fibre.

How do you rate the new mushroom fibres and imitation leathers that are being hyped right now?

Mycelium is also a biopolymer that biodegrades relatively quickly and therefore still needs many additives to make it last longer. You have to ask yourself whether it is really that sustainable. However, it is an interesting alternative for packaging materials such as Styrofoam, and is also said to be suitable as animal food.

You want to replace fossil plastics with bio-based ones rather than develop new ones. Why do you think that makes more sense?

In my opinion, this is the future. We just have to keep in mind that in the textile industry, we only work with a handful of different synthetic materials, so it seems feasible to find bio-based solutions for them. Completely new materials, on the other hand, need about 20 years until they can be accepted and produced in large volumes. And especially when it comes to recycling, it is an advantage to deal with only a few types of materials. We cannot build up many different recycling streams. But of course it is important that new possibilities are shown with new bio-based plastics, especially if increased functionality can be achieved through them. In this way, we can counteract the image that sustainable materials are always a compromise in terms of performance.

How advanced is the chemical industry in terms of the development of bioplastics?

A look at current figures is interesting here: in 2020, the chemical industry produced 360 to 380 million tonnes of fossil plastics worldwide, plus 20 to 40 million tonnes of recycled plastics and four million tonnes of bio-based plastics. According to studies, all sectors will continue to grow until 2025, with annual growth rates of three percent for fossil plastics, ten percent for recycled plastics and eight percent for bio-based plastics. This means that our demand for plastics will continue to rise, and it is absolutely clear that we cannot meet this demand from fossil raw materials alone. According to studies, we will produce about 1,200 million tonnes of plastic in 2050, and only a small part of that will be bioplastics. By far the largest share will then be recycled materials.

What significance does the textile industry and its efforts to become more sustainable have for the chemical industry in general?

Compared to the packaging or automotive industry, the textile industry actually plays a relatively small role for chemical companies. This also means that the chemical industry has little interest in developing or producing products solely for the textile industry, which is very price-sensitive. What has been happening increasingly in recent years, however, is the development of lighthouse projects.

We are currently seeing a shortage of recycled fibres, how are demand and supply for bioplastics at the moment?

Yes, it has indeed become more difficult to get recycled materials because some big beverage companies have already started to establish their own closed systems for their bottles - which means less waste is produced. At the same time, more and more large textile companies are announcing that they want to switch to recycled fibres. So the demand is higher than the supply. We have a similar situation with biopolymers. For example, Lego has switched to bioplastics for parts of its products, and of course we're talking about completely different volumes.

Vaude also launches products made of bioplastics. What kind of products are these?

We have developed various products from bioplastics - together with our suppliers from the preliminary stage. For example, a polyamide made from castor oil. The castor plant is an undemanding plant that even grows wild in many regions. It is cultivated in India and China, mainly by small farmers. The natural cosmetics industry uses the oil from the beans, but it can also be used to produce a bio-polyamide with a carbon footprint that is reduced by about half. From the oil we make fibres for clothing and plastic parts like zips, buckles and hooks. We have also developed a membrane that consists of 25 percent bio-based polyurethane, the starting material here being coffee grounds. For the spring/summer 2022 season, we will present a bio-based plastic in the footwear sector, which we have developed together with our partners.

How time-consuming is such an in-house development?

Very time-consuming. That's why there are not yet so many companies working with bio-based plastics, because it's an enormous expenditure of time and money. The challenges are really not to be underestimated because machines have to be adapted in part, the colour formulations et cetera. With Covestro, for example, we have been working for three and a half years on a new type of biobased material that is made from European corn and old cooking oil. The first products will be on the market in March 2022. This is pioneering work. It is hardly feasible for companies that actually only work with fabric manufacturers.

Does it matter for textile labelling what the plastic is made of? Should we expect ever longer labels?

No, it doesn't matter. For example, polyester and polyamide designate material families that classify different types of materials such as PET. For the customer, it is therefore not obvious whether it is bioplastic or not. This would have to be communicated separately. But it is important to note that if one wants to call a material biobased, it has to be more than 50 percent biobased, otherwise one could only communicate it as a biobased share.

With plant-based plastics, one always hears the criticism that their cultivation would compete with the cultivation of food as the population grows. How do you see that?

The problem is rather the enormous livestock farming. In Germany, for example, we used more than half of all agricultural land for animal husbandry in 2015. Food is actually grown at only 26 percent. Energy crops account for 13 percent of the rest, industrial crops for two percent and fallow land for one percent. Furthermore, if we switch to e-mobility, we will also need fewer plants for fuel and energy production. According to studies, bioplastics would require no more than five percent of global agricultural land if they replaced all fossil plastics. However, this scenario would not come to pass.

Do you have a goal, what are you working on long-term?

In the long run, it would be important to produce the raw materials where they are used. For example, the granulates could be produced here in Germany - even if they then have to be transported to Asia to be spun there. There are hardly any spinning mills here and in some cases the know-how is no longer available. But granules can be produced very well here, with renewable energy and clean processes. You could collect the products here at the end of life and recycle them. We have to start processing our waste here.

The trekking pant is made to 62 percent of castor oil

Photos: Vaude

This article was originally published on FashionUnited.de. Edited and translated by Simone Preuss.

Sustainable Fashion