Bamboo clothing has gained followers as a sustainable alternative to cotton… but is it really as green as the eco-warriors would have us believe? Or is this just another example of greenwashing?  Well, it’s complicated and the answer lies somewhere in between.  As a raw material, bamboo has many advantages over most other natural and synthetic materials used for clothing. There are, however, major environmental concerns about the way in which most bamboo fabric is currently manufactured.

Bamboo basics:

  • Bamboo is a truly remarkable plant, which, together with hemp, may well save the planet.  Although often referred to as a tree, it’s actually a fast growing grass species that covers around 3 million hectares of land in China (about 2% of the country’s total forest area) and 4 million hectares worldwide.  Bamboo canes can grow a staggering 1 metre per day and, once the plant has reached maturity, it can be continually harvested, with several new shoots emerging after each cane is cut. The root system of bamboo plantations actually helps to retain water and hold soil together; unlike cotton fields, which have to be slashed after harvesting each year, leaving soil vulnerable to water run-off and erosion.
  • Most bamboo plantations rely only on rainfall and don’t have to be irrigated; another huge advantage over cotton, which can require up to 20,000 litres of water per kilogram of fabric produced.
  • Bamboo is not generally susceptible to pests or diseases, so there’s no need to use harmful chemical sprays; in contrast, cotton farming accounts for more than 10% of total pesticide use and nearly 25% of insecticides used worldwide.
  • Bamboo can be grown on marginal land, which is unsuitable for other crops.  It also grows very densely, with yields far exceeding those of other plants.  Bamboo plantations produce around 60 tonnes per hectare, compared to 20 tonnes for most trees and only 1-2 tonnes per hectare for cotton. As global population increases and competition for fertile land becomes more intense, this will become an important issue in the future.
  • Bamboo plantations are powerful greenhouse gas busters, absorbing around 62 tonnes of carbon dioxide per hectare, compared to the 15 tonnes absorbed by an equivalent area of young forest.  They also generate around 35% more oxygen than equivalent stands of trees.

Facts behind the fibre

Bamboo can be processed into the fibres used to make clothing either mechanically or chemically.  Mechanical processing involves crushing the woody parts of the bamboo plant and combing out the natural fibres.  These are then spun into yarn, which is used to make a coarse fabric called ‘bamboo linen’. This is a genuinely eco-friendly manufacturing process, similar to the method of producing linen fabric from flax or hemp.  Unfortunately, the costs involved in mechanical processing mean that you’re unlikely to find bamboo linen outside haute couture designer collections.

Most of the bamboo clothing fabric available in Australia is manufactured in China, by a company that holds the patent on the chemical process for turning the bamboo plant into viscose rayon.  This method of processing involves crushing the plant and treating the cellulose with toxic chemicals to make a thick, viscous solution.  The solution is forced through spinneret nozzles (similar to a shower head) into a chemical bath, where the strands solidify into fibre.  After washing and bleaching, these strands become the rayon yarn used to make fabric.

The bad news

The main chemicals used in the viscose process are sodium hydroxide, carbon disulphide and sulphuric acid.  All of these are harmful to the environment when they are released into the air or enter the waterways as untreated effluent.  Exposure to carbon disulphide can cause a wide range of health issues for factory workers.  Short-term problems include nausea, vomiting dizziness, headaches, mood changes, fatigue, blurred vision and convulsions.  Long-term exposure in the workplace has been linked to neurological damage and reproductive health problems.

In early 2010, the U.S. Federal Trade Commission started to crack down on manufacturers and retailers for falsely labelling rayon products as ‘bamboo’ to appeal to environmentally conscious consumers.  In North America, it’s now a legal requirement to label fabric manufactured using the viscose process as ‘rayon’ or ‘rayon made from bamboo’.  There are no such requirements here in Australia.

An eco-fabric for the future?

While bamboo is a great sustainable material, that soft, stylish 'bamboo' dress in your wardrobe may not be as green as you were encouraged to believe. The good news is that technological advances in manufacturing offer the potential for a genuinely eco-friendly bamboo clothing fabric.  One of the most promising of these is to adapt the process used to produce Tencel® (a brand of lyocell, made from eucalyptus cellulose) to make fibre from bamboo cellulose.  This method of processing has major advantages over the viscose process in that the main chemical used - N-methylmorpholine N-oxide - is thought not to be harmful to humans. It also involves a closed loop manufacturing process, which recycles over 99.5% of the chemicals and water used.

Comment