What about bamboo fabric?

While bamboo has some incredible eco credentials (see related article on bamboo flooring), the fabric version of this popular plant isn’t necessarily as squeaky eco-clean as it might seem.  Furthermore, the hype around bamboo has led to a flurry of greenwashing with exaggerated or deceptive environmental claims.

There are two processes for converting the bamboo plant into a fiber: viscose and retting. The main environmental issue specific to bamboo fabric has to do with how the most common type of fabric is manufactured.

Retted Bamboo

Retting mechanically crushes the plant and then uses nature’s natural tendency to break down materials (aided by bacteria or enzymes) to loosen the fibers from the woody tissue.  Typically used for jute and linen, it is a time consuming and expensive process (compared with modern chemical processing of bamboo) and the resulting product isn’t as soft or shiny.  Sometimes called bamboo linen, this fiber is produced without significant chemical inputs, and so is much more environmentally friendly.  While fairly rare, it is emerging on the market and there are rumors of increasing manufacturers of this production type. 

Viscose Bamboo

Most bamboo fibers on the market are actually rayon, or regenerated cellulose (plant material), and most of those are made using a viscose production process. 

For this method, the plant material is treated with sodium hydroxide (i.e., caustic soda or lye) and then carbon disulfide to get a slurry, called, surprisingly, viscose.  The viscose is then forced through a spinneret to get long strands of fibers, which are hardened in a chemical bath, then washed and bleached. 

This bit of the process isn’t much different from the production of other rayons, and the main chemical used, sodium hydroxide, is approved for by the Global Organic Textile Standard (GOTS), for use with organic cotton.  However, as with other rayons, the quantity of sodium hydroxide used, along with the other highly toxic chemicals, pose serious threats to human health and the environment (in production that is – not in the final product).

While not as sustainable as using no chemicals at all, manufacturing viscose wouldn’t be too bad if the process was ”closed loop”, whereby the chemicals are captured and reclaimed. 

A number of websites suggest that bamboo viscose fiber is made by one company in China, the Jigao Chemical Fiber Company, who owns the patent.  While a Scientific America article suggests that Jigao has a “sophisticated wastewater treatment system”, it is not clear exactly what these means and where the chemicals are disposed, and it is certainly not closed loop.

Other Textile Processes

All fibers are spun into yarns, which are then woven or knitted into fabrics.  Usually, at some point those fibers, yarns, or fabrics are dyed.  Conventional dyes typically contain heavy metals such as lead and mercury, as well as chemicals that cause DNA mutations or are endocrine disruptors.

Again, the issue is the impact on the health of the workers and to the environment.  How are these materials handled during production? Are they treated before leaving the factory.  In many cases they aren’t, and the pollutants find their way into the water system.

Finally, finishes (sometime mechanical, sometimes chemical) are applied to the piece of fabric before it reaches it’s final form.  Again, how are these chemicals handled?

Greenwashing vs Green Bamboo Textile

So is conventional bamboo (rayon) fabric eco-friendly?  Does the fact that the raw material comes from a more environmentally sustainable crop make it a eco textile?  I don’t think so, although it does seem to have an eco advantage over other rayons.

It would be interesting to see a life cycle assessment comparing bamboo rayon to conventional and organic cotton.  Organic cotton can be dyed and finished with the same toxic chemicals as bamboo.  I’m not sure how the bamboo version would stack up.  And, of course, there are a lot of variables (unbleached? natural dyes? no toxic finishes? water conservation measures for the cotton?).

The textile industry is notorious for it’s negative environmental impact.  While the growing and harvesting of bamboo is generally eco friendly, the viscose process negates much of that benefit.  But some companies are really trying to change things, and I expect there will be more options in the future.

So what do you do?

Want soft, luscious bamboo towels or sheets?  Just ignore the hype and enjoy the product, knowing that what you are getting isn’t as environmentally friendly as it claims.

Want truly sustainable bamboo textiles?  Seek unbleached, retted bamboo colored with environmentally sensitive dyes.  There’s a tiny little bit out there, and demanding more will only help grow the market.  Or wait for a ”closed loop” bamboo rayon – maybe even made by an ISO 14001 certified manufacturer – but don’t hold your breath.

Sources:

• Bamboo Boom: Is this material for you?  Scientific America
• Bamboo & the FTC, O Ecotextiles blog
• Bamboo: Facts behind the fiber, Organic Clothing Blog