FIBRE 101: VISCOSE

How environmentally friendly is viscose and rayon? It's time to get real about cellulose fibres. Image courtesy of Burst

12.08.2017

Fibre 101: Viscose
Courtney Holm


It's often said that cellulose fabrics such as viscose, bamboo and rayon are eco-friendly, bio-degradable and hypo-allergenic. Buzz words like these are thrown around like confetti. The 'natural' properties of these materials are heralded as nothing short of virtuous, as the only logical alternative to thirsty cottons or oil based polyesters and other synthetics. However, I want to talk facts about this fibre so you, dear wearer of fibres, can be informed when buying your next "100% eco-friendly" garment.

But first, some history. What exactly is rayon? And WTF is viscose? Buckle in guys, we are going to get technical. Rayon is the generic name of a cellulose fibre. Cellulose fibres are not 100% natural, nor are they 100% synthetic, but rather somewhere in between. Prior to the invention of rayon, fibres were typically natural (think cotton, linen or hemp) or protein (like wool and silk). Rayon is the oldest cellulose fibre and was developed as a cheap alternative to silk in the 1880s, so it's been around since before synthetic fabrics were even developed (nylon was the first- invented in the 1930s).

There are several techniques used to make rayon, the viscose process being the most commonly used today. Viscose, therefore, refers to the process, the end product fabric is often labelled viscose, rayon or viscose-rayon. Essentially, viscose processing begins with some sort of wood pulp, this could derive from beech wood, eucalyptus, bamboo or even cotton linters. It is here where the naturalness of viscose begins and ends.

Cotton Linters
Cotton Linters. Image by Courtney Holm.


The wood pulp is initially treated with sodium hydroxide to extract and purify the cellulose into alkaline sheets ready for pressing. Those sheets are pressed and shredded into a crumb that is aged for a few days. A chemical called carbon disulphide is added, turning the crumb into cellulose xanthate and becoming yellow in colour. These crumbs are then dissolved in a weak solution of caustic soda, which converts the cellulose xanthate into a honey-coloured, highly viscous liquid (hence the name). The fluid is then ripened and pushed through a spinneret of tiny holes where long strands are extruded and then placed into a chemical bath of sulphuric acid, sodium sulphate and zinc sulphate to harden- also releasing carbon disulphide and hydrogen sulphide. Fibres are then stretched, with a variety of additional chemical processes, including bleaching. If you're still with me, you can see just how much of this fibre is 'man-made'. 

Let's delve a little deeper into those chemicals. Exposure to carbon disulphide can cause damage to the human nervous system, while the disposal of sodium hydroxide and sulphuric acid is a major problem for the environment- especially in places where communities rely on local waterways. These toxic chemicals are released into the air, causing pollution that makes people sick. Often, these chemicals are discharged into local rivers, contaminating the waterways and, in turn, harming plants, animals and humans who come into contact with the water. Fishing communities are greatly effected by polluted water as fish decrease in numbers. Any industry that uses sulphuric acid runs the risk of accidental leaks and many industrial plants do not dispose of it correctly. There’s simply not enough transparency in viscose manufacturing. Even if chemicals are reclaimed, they still pose a serious risk both for the workers who handle it and the communities who live nearby. Identified issues include local river and lake poisoning, toxic littered fibres into villages, highly toxic air quality and regular sickness from pollution, significantly reduced fish in waterways, highly acidic wastewater from factory discharge pipes, illegal dumping and community wells rendered undrinkable.

Viscose Plant Discharge by Changing Markets
Waste Water Outfall near Viscose Plants in China Image by Changing Markets


Recently, the manufacturing of viscose came under fire after an investigation by Changing Markets into the world's largest viscose producers revealed devastating pollution and massive negative social impact in the producing communities. You can read more about that here but- be warned- it's incredibly detailed, so give yourself half an hour to really get into it. 

All that marketing about viscose is simply that, marketing. Want to know something else? Bamboo, the much loved fibre of the "eco-friendly", is usually created using this VERY method. Because the original cellulose is bamboo pulp (a rapidly growing, non-land clearing, minimal pesticide user) it gets some sort of special pass and is marketed as even more virtuous, so much so that instead of being labelled viscose, as it rightly should be, it gets to be called "bamboo". Never mind the fact that there is 0% trace of bamboo left in the fibre after the process is complete. So there's some food for thought. Note here that there are a couple of places producing bamboo in a better way, for example using the lyocell method (quite rare) or the linen process (very time consuming, laborious and even more rare). 

 

After the viscose process, wood status = gone.
After the viscose process, wood status = gone.

 

So, it's looking pretty bleak for viscose. Is there any good news? Yes, yes there is. A great alternative to this chemical-ridden beast is called Tencel. It has a much gentler process, its industry coined name is lyocell, and it produces a cellulose fibre just as versatile as viscose. Tencel has evolved off the back of other cellulose processes like viscose, however by using solvents that are 99.9% reclaimed and re-used, it closes the loop in terms of chemical production and disposal. Tencel is a branded trademark of Lenzing, and although lyocell technically uses the same method, lyocell's name can't guarantee its closed loop status, whereas Tencel can. So, in conclusion, if you are looking for a fibre that uses less water in growing and production than cotton, is as soft as silk and still biodegrades, Tencel could be a great choice for a more environmentally friendly cellulose fabric. 

 

Semi-processed dumped viscose
Semi-processed viscose found by Changing Markets researchers. Image by Muhammad Fajar Fauzan


Keep in mind that no fabric is truly perfect and Tencel is derived from eucalyptus trees, which are cleared for the purpose of fibre consumption. Although Lenzing claim to have their pulp certified from the Forest Stewardship Council and Canopy, there could still be risk of deforestation. Interesting to note is that Lenzing produces both Tencel and Viscose fibres. One of their factories is listed in the Changing Markets report I mentioned before- and not in a good way. It goes to show that even though Lenzing have identified a market for more environmentally friendly cellulose fibres, they aren't ready to give up on their bread-winning Viscose industry just yet. All the more reason, my friends, to only buy the good stuff.

Overall, I give viscose the thumbs down, and certified Lenzing Tencel the thumbs up. What about you? Tell me what you think! As always, you can get ranty or inquisitive by contacting me at hello@abch.world x