Lyocell: a sustainable fabric solution

Lyocell is a flexible and versatile fibre made from eucalyptus and other wood – and it doesn’t take lots of energy or chemicals to produce. By Jeremy Torr.

  Lyocell thread ready to be made into fabric

Lyocell thread ready to be made into fabric

Singapore, 21 March 2015- Most people assume that clothing textiles can be split into two groups - natural fibres like cotton, wool, hemp, and silk; and manmade textiles such as nylon, polyester, lycra and so on. But there is another option – and one that claims several advantages.

Lyocell is a cellulose-based fibre manufactured from specially-grown wood pulp. An unlike cotton, wool and silk it is very easy, cheap (and energy friendly) to process. The wood pulp – often from quick-growing and arid-zone friendly eucalyptus – is broken down by special amine solutions into semi-liquid paste. The paste is then ejected under pressure from a special spinneret nozzle to form threads; these are flexible and can be woven and manipulated just like natural fibres. Lyocell is the generic name, but you can find it labeled as Tencel on garments and other items such as bedding or curtains.

Lyocell Process

 Eucalyptus chips are treated with amino liquids to form a consistent cellulose pulp then spun into lyocell fibre

Eucalyptus chips are treated with amino liquids to form a consistent cellulose pulp then spun into lyocell fibre

The lyocell process was invented in the 1980s by researchers at textile company Courtalds, and uses a fairly simple process. The eucalyptus wood (extremely fast-growing with low water and minimal pesticide requirements) pulp is soaked in a non-toxic amine oxide solution to make the cellulose paste. Although amine oxide is sourced from hydrocarbon oil bases, it can be 95% purified and reused again and again in the lyocell process, so has a very low environmental footprint. 

This process extracts raw cellulose from the wood pulp, which can then be pumped through the fine nozzle systems to produce the lyocell filaments. The biggest makers, Austrian company Lenzing Fibers, call it a "solvent spun fiber" process that closely mimics the cellulose structure found naturally in wood and twigs.

The result is a “natural” fibre that is soft, smooth, breathable, naturally wrinkle-resistant, and relatively environmentally sustainable. The companies producing it – currently only a few plants in the US, India and Europe produce it – claim lower atmospheric emissions from smokestacks and cleaner and less) wastewater too. The processes that normally accompany other “natural” fibres such as bleaching, washing and sterilizing are absent, making lyocell much more environmentally friendly overall.

Lyocell- The good and bad

Lyocell is also strong and durable. It is the strongest cellulosic fiber when dry, even stronger than cotton or linen and is even stronger than cotton when wet. This means it can cope with many successful machine washes when woven into a fabric.

 Lyocell fibres compare well for smoothness to other natural fabric

Lyocell fibres compare well for smoothness to other natural fabric

The other plus is that lyocell is good for sweaty people. The fibril structure of the threads helps with moisture absorption to “create an optimal skin climate” say the makers. That means less pong, compared to synthetic fibers (which can have hundreds to thousands times higher bacteria count than lyocell) and cotton. Synthetics don’t absorb anything, and cotton only half the sweat of lyocell, say the inventors.

This also means that clothing made of lyocell remains fresh much longer than cotton – several wearings are possible. That in turn means fewer washings and a corresponding saving on water and energy.

The other big plus is that lyocell can be recycled and will also happily and quickly biodegrade given the right conditions – just like the wood it is made from. It can either be burnt to produce energy or digested in sewage plants or your own backyard compost heap. Tests have shown that lyocell fabric will degrade completely in waste treatment plants over a period of just a few days.

Although, as it comes from the nozzles, the thread is quite light in colour, lyocell does not need bleaching to produce a uniform hue, unlike cotton which produces lots of toxic by-products from its chlorine bleaching processes.

In fact bleach is often used in many “natural” fibre manufacturing processes, especially cotton, along with huge quantities of contaminated wastewater. The European Union awarded the lyocell process the Environmental Award 2000 in the category "technology for sustainable developments". And best of all, it is lovely and soft; and takes bright colour dyes well too. Is there no downside to lyocell? OK, just one.

Fluffy pill

The only downside admitted to by the makers of lyocell is that it gets furry. Over time and use it tends to “pill” like polyester garments – especially when washed a few times. This is basically the surface layers of cellulose peeling away – abit like the bark from a tree. The problem is lyocell has a relatively low surface energy, which makes it prone to pilling by weakening surface hairs so they can be fluff up and pill. This tendency can be suppressed using enzyme-based fibre coatings, but adds to the chemical tally and moves it away from that ultra eco-friendly label. The makers do claim most of these enzymes occur in nature and are responsible for the breakdown of vegetation – which still makes them more eco-friendly. Than the harsh petro-chemicals used on many other fabrics.

So that’s lyocell (or Tencel if you need the tradename). Might be worth looking for the label on your next shirt or skirt. If it has lyocell in it, you can look good as well as afford a pat on your own eco-back.

 For more info, go to : www.lenzing.com/en/fibers/tencel.html