There’s never only one side to any story. Bamboo fabric is a classic example of a product that on the surface sounds very green. Bamboo plants grow incredibly quickly, can be planted in areas unsuitable for other crops, and rarely need any pesticides or herbicides. But issues arise with the way the fibres are processed and the fabric manufactured.
The most popular manufacturing process involves sodium hydroxide and carbon disulfide, both highly toxic chemicals to humans, and when released into the environment. The majority of bamboo fabric production takes place in China, a country not renowned for worker’s rights or environmental respect.
Bamboo fabric may have something to learn from another material that’s been produced quietly, with little environmental fanfare, for the last twenty years. Lyocell, sold as Tencel, is a fabric made from wood pulp. Tencel and Tencel blends drape well and are used predominantly in dresses and formalwear.
Tencel is manufactured in a proprietary process by the Lenzing Group, a international group of companies based in Austria. Lenzing describe themselves as “committed to the principles of sustainable management and very high environmental standards.” Tencel is manufactured in a similar way to bamboo fabric, but with important differences that may be the solution to green bamboo fabric manufacturing.
Here’s the recipe. First, take some wood pulp. Lenzing’s pulp mill uses hardwood – mostly birch and oak – from sustainable forestry plantations. The trees are chemically pulped and bleached. Lenzing say they utilise a closed-loop process and don’t use chlorine bleach to minimize environmental impact. However, Lenzing also buys wood pulp and their website becomes vague as to what conditions their suppliers’ wood pulp is manufactured under.
Next, the wood pulp is turned into fibres through a process called “solvent spinning”. Wood pulp is dissolved in a chemical called N-Methylmorpholine N-oxide (NMNO). The liquid is squirted through thousands of tiny holes in a spinneret, forming individual Tencel fibers. The spun fibres are washed, the NMNO is retrieved from the water, and it is purified, and reused in a 99% closed-loop process. NMNO can be toxic, but much less so than the sodium hydroxide and carbon disulfide used for processing bamboo. Small quantities of NMMO are actually produced in the body as a metabolite of several common drugs.
With a sustainable source of wood pulp, Tencel manufacturing has a much lower environmental impact than bamboo fabric. But despite considerate forestry practices, tree farms are more damaging to the ecosystem than growing bamboo. When natural forests are cleared for farms the local ecosystem suffers from the reduction in bio-diversity in the area. Bamboo is the slight winner here: it naturally colonises areas other plants find challenging and often grows with few other species for company, so it has less environmental impact when planted as a monocrop on a farm. Bamboo also grows much faster than hardwood trees, processing many times more CO2 from the environment than trees can.
Bamboo can be grown ecologically, and because of the increasing popularity of bamboo, companies are developing new, greener, ways to process the fibres ecologically, inspired by Tencel processing. Companies like Pure Bamboo are using new closed-loop processing methods, and hopefully more will follow.
Tencel is currently more eco-friendly to manufacture, and – depending on your standards – acceptably eco-friendly to grow. But bamboo fabric has the potential to be a true eco-friendly cloth.
For more on Tencel, What is Tencel on Wisegeek.
This post was written by one of Green Cotton’s contributing writer’s Brit.