Recycling our jeans in the garden

A recent ‘Spiegel Online’ article on sustainable fashion also included mention of compostable jeans. We put a few questions on the subject to Christin Glöckner, who, as a textile researcher in the Department of Hygiene, Environment and Medicine at the Hohenstein Institute for Textile Innovation, spends some of her time messing up jeans and T-shirts for scientific purposes.

Ms. Glöckner, biodegradable clothing is indeed coming into fashion – but seriously! – Why compostable jeans?

Simply because of an awareness of our ecological responsibilities.

Well, now I feel a little naive ….

No you mustn’t feel that! Often, when people think of ecological acceptability, they think only of the manufacturing process and the individual components of a product. In reality, sustainable cultivation of the raw materials, using limited quantities of water and pesticides, sparing use of chemicals in the dyeing process as well as a reduction of energy consumption are all enormously important for the overall ecological footprint of a textile product. But a complete sustainability profile ought also to contain an ecologically acceptable destination for the materials after use. That, moreover, is also the view of the US Environmental Protection Agency (EPA), of whom everyone has now heard since the VW scandal, if they had not done so before. The EPA defines the biodegradability of materials and products as one of the most important factors in assessing their overall environmental performance.

Wirft Jeans nur zur Testzwecken weg: Textilforscherin Glöckner beim Probenzuschnitt im Labor (Quelle: Hohenstein Institute)

Throws jeans away just for test purposes: textile researcher, Christin Glöckner at a sample cutting session in the laboratory (Source: Hohenstein Institute)

What normally happens to jeans that are no longer serviceable?

There are, of course, the traditional paths – a second phase of value creation via the second-hand market or by taking them to the charity shop, and then there’s recycling and thermal reprocessing. Processes such as down-cycling and up-cycling, whereby the original materials are re-used in either lower or higher quality products, are also in the ascendancy. Along with materials and additives that are increasingly more ecologically acceptable, we can now add biodegradability. And then we talk about ‘biodegradable’ products.

Are traditional jeans all biodegradable in principle?

Mostly not; commercially-sold jeans, of course are usually made of cotton, which is a natural fibre and, in principle, therefore, biodegradable. But trousers often also contain elastic man-made fibres to increase the stretch factor. It makes the jeans more pleasant to wear, but it also impacts negatively on their biodegradability. Trouser buttons, on the other hand are not a problem; they are easily removed before the jeans are composted.

Where do the greatest challenges lie in biodegradability research?

We have to be sure that the compostable textiles really do disappear into the soil without trace, i.e. that the materials and the residue from the dyeing and finishing processes don’t have a negative impact on the environment. We therefore look closely at what exactly happens when various fibre-based materials rot – how quickly, or slowly, they break down, what remains of them, which bits are particularly resistant etc. Ecotoxicological analysis plays a major role in this.

Klarer Sieger beim Wettrennen im Verrotten: Polyester (links) gegen Baumwolle (rechts) nach 0, 2, 5, 7, 12 und 14 Wochen (Quelle: Hohenstein Institute)

Clear winner in the rotting competition; polyester (left) versus cotton (right) after 0, 2, 5, 7, 12 and 14 weeks (Source: Hohenstein Institute)

Ecotoxico… what?

“Ecotoxicological” – it comes from ecotoxicology and means the science that deals with the effects of chemicals on the living environment. We need to be sure that no kind of significant or indeed toxic substances, like, say, the man-made-fibre elements in jeans we talked about before, remain in the soil.

Do artificial additives ever biodegrade, then?

That is the major challenge. We have been doing more tests on synthetic textiles recently, which are increasingly expected to be environmentally friendly. Here’s an example: we are currently investigating the biological degradability of carbon fibres in composite fibre materials. In the process, we use special micro-organisms, which can metabolise chemical compounds in biochemical processes. I know it sounds a bit crazy, but it is a way in which a non-biological, artificial component can be degraded micro-biologically – and end up completely absorbed into the relevant materials cycle.

So I could actually simply throw a pair of ‘compost jeans’ away in the garden?

If you don’t mind standing in front of your neighbour without any trousers on, sure!

For everyone who simply can’t get enough of biodegradability, there are a still a few films to watch here and here.

Ronny Eckert

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