“Bamboo” fabric has taken the world by storm – people love its luxurious softness, smooth hand and gentle drape, and they also seem to love its eco credentials (as touted by those selling the fabric).
It’s easy to tout bamboo (the plant) as eco friendly, because it is a wonderfully beneficial plant and just might be the world’s most sustainable resource: It’s the fastest growing grass and can grow up to a yard or more per day. Growing bamboo improves soil quality and helps rebuild eroded soil. The extensive root system of bamboo holds soil together, prevents soil erosion, and retains water in the watershed. It doesn’t require replanting after harvest because its vast root network continually sprouts new shoots, all the while pulling in sunlight and greenhouse gases while converting them to new growth. All this without the use of tractors or other machinery using petroleum, and without pesticides or fertilizers.
Bamboo (the plant) produces a huge biomass, both above and below ground. One study found bamboo produces 14 tons of wood per acre, as against 8 for loblolly pine; planted in large groves, it can store four times the CO2 as a stand of trees of similar size, and it releases 35% more oxygen. Currently there are no known genetically modified organism (GMO) variants of bamboo.
But though bamboo the plant can be terrifically sustainable and beneficial, bamboo the fabric can raise environmental and health concerns – but like many issues on the green front, the answer is not black and white. Some bamboo fiber can be green and some is not – and some green bamboo fiber can be woven conventionally and dyed with dyestuffs that contain lead, mercury, or other heavy metals, mutagenic chemicals that change our DNA or endocrine disruptors which affect our hormone balance. And the factory using these chemicals probably did not treat their effluent before returning it to our waterways.
The Federal Trade Commission has finally acted to restrict some of the more outrageous claims being made about textiles, bamboo fabric specifically: they have charged four sellers of clothing and other textile products with deceptive labeling and advertising. Their intention is to demonstrate that unsubstantiated green claims in the clothing and other textile related product categories will not be tolerated. And believe me, that’s a GREAT thing, because claims are being made for “green” textiles of every stripe – often stretching the “green” issue to the limit. But to categorically say bamboo fabric is NOT green is to overstep in the opposite direction. There is some naturally retted bamboo (processed like flax or hemp) on the market though it’s still hard to find. The process used to turn bamboo into a fiber which is used almost exclusively today, the viscose process, can also be eco friendly if the manufacturer makes the effort to capture emissions and treat effluent. We have to stop and take the time to evaluate claims.
Let’s give it a go.
“Rayon” is the generic name for any man-made fiber made from cellulose – man in this case applies a chemical process to transform the cellulose. It’s usually used with cellulose found in very hard and woody plants, such as wood or bamboo, although it can also be made from algae or other types of cellulose. Cellulose is a carbohydrate and the chief component in the walls of plants. There are several chemical and manufacturing techniques to make rayon, but the most common method is the viscose process. In the viscose process, cellulose is treated with caustic soda (aka: sodium hydroxide) and carbon disulfide, converting it into a gold liquid about the color and consistency of honey, called viscose. Viscose is forced through fine holes, called a spinerette, directly into a chemical bath where it hardens into fine strands. When washed and bleached these strands become rayon yarn. Most rayon made today uses this viscose process, which dates to the early 1900s.
Viscose is known as a “regenerated cellulose” fiber – in other words, it is reconstituted from cellulose. Other regenerated cellulosic fibers include lyocell, Tencel®, modal and MicroModal – these are all made from wood. Although the viscose process of making rayon from wood or cotton has been around for a long time, it wasn’t until 2003 that a method was devised for using bamboo for this process.(3)
The reason the viscose process is thought to be detrimental to the environment is based on the process chemicals used. Though sodium hydroxide is routinely used in the processing of organic cotton, and is approved by the Global Organic Textile Standard (GOTS), carbon disulfide can cause nervous system damage with chronic exposure. And that “chemical bath” to harden the threads? Sulfuric acid. These chemicals do not remain as a residue on the fibers – the proof of this is that almost all of the viscose produced can be (and often is) Oeko Tex certified (which certifies that the finished fiber has been tested for any chemicals which may be harmful to a person’s health and contains no trace of these chemicals.)
The problem comes in disposing of these process chemicals: the sodium hydroxide (though not harmful to humans) is nevertheless harmful to the environment if dumped into our rivers as untreated effluent. Same with carbon disulfide and, certainly, sulfuric acid. Oeko Tex certifies only the final product, i.e.,the fibers or the fabric. They do not look at the production process, which can be devastating. The production could be done in a closed loop process, capturing and reclaiming all the chemicals used during manufacture, but this is seldom done.
And then of course there is the weaving of these viscose fibers into fabric – if done conventionally, the environmental burden is devastating (in terms of chemical and water use) and the fabric itself probably contains many chemicals known to be harmful to our health.
What is the FTC saying in their charge of deceptive advertising? The unsubstantiated green claims they take issue with are:
- The claim that the products are manufactured using an environmentally friendly process.
- As I explained above, the claims may or may not be true. Certainly the standard viscose production process is definitely NOT environmentally friendly, but some manufacturers use new closed loop systems, treat and/or recycle wastewater and capture emissions. Tencel® certainly advertises its environmentally friendly production processes, based on closed loop systems, and a new non-toxic solvent (amine oxide) which, they say, is 99.9% recycled. Tencel® brand takes great pains to differentiate itself from viscose (saying that it is different because it’s based on solvents, but I cannot find what they really mean by this as it seems to me they’re just using different chemicals.) In the lyocell/Tencel process, the wood pulp is dissolved in N-Methylmorpholine N-oxide, then pushed thru spinneets to form individual fibers. Although there is little by-product, the process uses a lot of energy and the solvent used is a by-product of gasoline production.
- The claim that these products retain natural antimicrobial properties of the bamboo plant.
- There has been little research done on viscose made from bamboo. However, many studies have been done by Lenzing Group, which produces Tencel®. One study sponsored by Lenzing found that “bacterial growth on textiles made from cellulosic fibers as compared to synthetic fibers showed lower bacterial growth”. Of course, many claims assert that bamboo’s “natural antimicrobial properties” are retained by the viscose fibers. However, could it be possible that the exceptional water absorption ability of cellulosic fibers retards bacterial growth, as Tencel® claims?
- The claim that they are biodegradable.
- Ohio State University’s Consumer and Textile Sciences fact sheet on lyocell says it is “biodegradeable and recyclable” and Tencel® also makes that claim – as seen in many advertisements about products made from this fiber. Is the bamboo viscose not as biodegradeable and/or recyclable as lyocell and Tencel®, both very similar fibers to bamboo viscose? What is the inherent difference that would preclude the degredation of one and not the other?
The FTC says that “bamboo is not a generic fiber”. Their reasoning is that the products are advertised as being made of “bamboo” when they should be saying the products are made of “rayon” or “rayon from bamboo”:
- The differences between lyocell, Tencel, modal and viscose gets WAY technical; I think it’s sufficient here to note that they are all known by their fiber or brand names, rather than the cellulose source used in production. For example, rayon is derived from wood pulp – and the kind of wood used can vary from beech, pine, spruce and hemlock to Eucalyptus – it’s not known as “lyocell rayon from beech” or “Tencel rayon from beech trees” as the FTC is requiring for “rayon from bamboo”. MicroModal, another regenerated cellulosic fiber, is even classified as “cotton” for importation by U.S. Customs.(6)
I guess I’m glad they’ve finally drawn a line in the sand. Something is always better than nothing. But I’m disappointed that they’re focusing on the fiber and ignoring the processing, because the processing is both a huge environmental burden (if done conventionally) and potentially very harmful to us and our kids. So why stop with the fiber? The Global Organic Textile Standard (GOTS) addresses these issues. If manufacturers were forced (by the market or by federal regulations) to have third party certifications in place, we’d all be healthier and the ecosystem would have a better chance. Perhaps the FTC could spend some effort spreading the word about GOTS and what exactly a GOTS certified fabric is and why it’s better than a fabric (non certified) made with a GOTS certified – or organic – fiber.
Raver, Ann, “A Cane the World Can Lean On”, New York Times, July 5, 2007
 Janssen, Jules A., Technical University Eindhoven, 2000
 US patent 7313906 by Xiangqi Zhou, Zheng Liu, Liming Liu and Hao Geng