After my recent post on bamboo fabrics Graham left a comment stating that bamboo might not be as environmentally friendly a fabric as I had first thought. Had I been greenwashed? Is bamboo eco friendly? Well after some research I discovered the answer is yes and no.
The process of producing the raw bamboo does have a low environmental impact. However when it comes to processing the bamboo into a fabric there can be a significant ecological impact. Basically there are 2 ways in which bamboo can be turned into a fabric, mechanically or chemically.
Mechanical Processing of Bamboo
Mechanical processing involves crushing the bamboo plant and then using natural enzymes to break down the bamboo into a pulp which can then be combed and spun into yarn. Bamboo fabric produced in this manner has a low impact and is generally known as bamboo linen. However this is not generally used for clothing due to the fact it is more labour intensive and costly.
Chemical Processing of Bamboo
There are a few different chemical processes that bamboo can go through to be transformed into fiber, some of these are more eco-friendly than others.
Hydrolysis alkalization with multi-phase bleaching
The process used for producing bamboo fabric is known as hydrolysis alkalization with multi-phase bleaching. It consists of the following stages;
- Bamboo leaves and the soft, inner pith from the hard bamboo trunk are extracted and crushed;
- The crushed bamboo cellulose is soaked in a solution of 15% to 20% sodium hydroxide at a temperature between 20 degrees C to 25 degrees C for one to three hours to form alkali cellulose;
- The bamboo alkali cellulose is then pressed to remove any excess sodium hydroxide solution. The alkali cellulose is crashed by a grinder and left to dry for 24 hours;
- Roughly a third as much carbon disulfide is added to the bamboo alkali cellulose to sulfurize the compound causing it to jell;
- Any remaining carbon disulfide is removed by evaporation due to decompression and cellulose sodium xanthogenate is the result;
- A diluted solution of sodium hydroxide is added to the cellulose sodium xanthogenate dissolving it to create a viscose solution consisting of about 5% sodium hydroxide and 7% to 15% bamboo fiber cellulose.
- The viscose bamboo cellulose is forced through spinneret nozzles into a large container of a diluted sulfuric acid solution which hardens the viscose bamboo cellulose sodium xanthogenate and reconverts it to cellulose bamboo fiber threads which are spun into bamboo fiber yarns to be woven into reconstructed and regenerated bamboo fabric.
What are the effects of the chemicals used to process bamboo?
At very high levels, carbon disulfide may be life-threatening as it affects the nervous system, at low levels of carbon disulfide can cause tiredness, headaches and nerve damage. It has a quick affect on wildlife especially aquatic life and has long term effects including; shortened lifespan, reproductive problems, lower fertility, and changes in appearance or behaviour.
sodium hydroxide (NaOH)
Low levels of exposure to sodium hydroxide can cause irritation of the eyes and skin while high levels can chemical burns, scarring, and blindness.
So we can see that the chemicals used in the hydrolysis alkalization, the most common method of producing bamboo fabric definitely can have an impact both on the environment as well as the workforce.
Other methods of chemically processing bamboo
Newer manufacturing facilities have begun using other technologies for processing bamboo which are more eco-friendly. The chemical manufacturing process used to produce lyocell from wood cellulose can be modified to use bamboo cellulose. The lyocell process, also used to uses N-methylmorpholine-N-oxide. This lyocell processing is much safer for workers and more eco-friendly due to the N-methylmorpholine-N-oxide is claimed to be non-toxic to humans and the chemical manufacturing processes are closed-loop so 99.5% of the chemicals used during the processing are collected and recycled to be used again.
The commercial growing of bamboo is quite an eco-friendly process, however the way in which it is processed and turned into fabric currently is not, as well as having health consequences for the workers involved.
I do however believe bamboo does have a future as an environmentally friendly fabric. The bamboo should be easily sustainable, the material has fantastic properties all that is needed is for manufacturing processes to become more eco friendly, which seems to be starting to happen. So in my opinion there definitely is a future for truly “green” bamboo fabric.
Before I finish I have to thank Graham for commenting and providing the impoteus to write this article. “Question everything people!”