is Bamboo Rayon?
Bamboo: Facts behind the Fiber
What do conventional fashion designers Diane vonFurstenberg, Oscar de la Renta, Kate O’Connor, Agnes B and eco-fashion designers Amanda Shi of Avita, Linda Loudermilk, Katherine Hamnett, Miho Aoki and Thuy Pham at United Bamboo, Sara Kirsner at Doie Designs, and clothing manufacturers Bamboosa, Shirts Of Bamboo, Jonano, HTnaturals in Canada and Panda Snack, and fabric manufacturers Table Bay Spinners of South Africa, Richfield Tang Knits Ltd. in Mauritius have in common? Bamboo.
In part because of its luxurious softness, smooth hand, flowing and gentle drape, and easy price – at least compared with silk and cashmere – and eco friendly cachet, bamboo has gained entry throughout the fashion industry. But it has been the trumpets heralding bamboo as the latest and hottest sustainable eco-fabric that have been the most strident. And some of the hoopla is justified. Growing bamboo is a wonderfully beneficial plant for the planet and most is naturally organic bamboo. The manufacturing processes where bamboo the plant is transformed into bamboo the fabric are where the sustainability and eco-friendly luster of bamboo is tarnished because of the heavy chemicals, some of which are toxic, that are often required. Very, very little bamboo clothing would qualify as sustainable or organic clothes. Here’s the scoop.
Botanically categorized as a grass and not a tree, bamboo just might be the world’s most sustainable resource. It is the fastest growing grass and can shoot up a yard or more a day. Bamboo reaches maturity quickly and is ready for harvesting in about 4 years. Bamboo does not require replanting after harvesting because its vast root network continually sprouts new shoots which almost zoom up while you watch them, pulling in sunlight and greenhouse gases and converting them to new green growth. And bamboo does this the natural way without the need for petroleum-guzzling tractors and poisonous pesticides and fertilizers.
Bamboo the plant is wonderfully sustainable; bamboo the fabric isn’t so easy to categorize. There are two ways to process bamboo to make the plant into a fabric: mechanically or chemically. The mechanical way is by crushing the woody parts of the bamboo plant and then use natural enzymes to break the bamboo walls into a mushy mass so that the natural fibers can be mechanically combed out and spun into yarn. This is essentially the same eco-friendly manufacturing process used to produce linen fabric from flax or hemp. Bamboo fabric made from this process is sometimes called bamboo linen. Very little bamboo linen is manufactured for clothing because it is more labor intensive and costly.
Chemically manufactured bamboo fiber is a regenerated cellulose fiber similar to rayon or modal. Chemically manufactured bamboo is sometimes called bamboo rayon because of the many similarities in the way it is chemically manufactured and similarities in its feel and hand.
Most bamboo fabric that is the current eco-fashion rage is chemically manufactured by “cooking” the bamboo leaves and woody shoots in strong chemical solvents such as sodium hydroxide (NaOH – also known as caustic soda or lye) and carbon disulfide in a process also known as hydrolysis alkalization combined with multi-phase bleaching. Both sodium hydroxide and carbon disulfide have been linked to serious health problems. Breathing low levels of carbon disulfide can cause tiredness, headache and nerve damage. Carbon disulfide has been shown to cause neural disorders in workers at rayon manufacturers. Low levels of exposure to sodium hydroxide can cause irritation of the skin and eyes. Sodium hydroxide is a strong alkaline base also known as caustic soda or lye. In its dry crystalline form, caustic soda is one of the major ingredients of Drano. This is basically the same process used to make rayon from wood or cotton waste byproducts. Because of the potential health risks and damage to the environment surrounding the manufacturing facilities, textile manufacturing processes for bamboo or other regenerated fibers using hydrolysis alkalization with multi-phase bleaching are not considered sustainable or environmentally supportable.
While specifics can vary, the general process for chemically manufacturing bamboo fiber using hydrolysis alkalization with multi-phase bleaching technology – which is the dominate technology for producing regenerated bamboo fiber – goes like this:
1.Bamboo leaves and the soft, inner pith from the hard bamboo trunk are extracted and crushed;
2.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;
3.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;
4.Roughly a third as much carbon disulfide is added to the bamboo alkali cellulose to sulfurize the compound causing it to jell;
5.Any remaining carbon disulfide is removed by evaporation due to decompression and cellulose sodium xanthogenate is the result;
6.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.
7.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.
This gives some feel for how chemically intensive the hydrolysis-alkalization and multiphase bleaching manufacturing processes are for most bamboo fabrics that are promoted as being sustainable and eco-friendly.
Newer manufacturing facilities have begun using other technologies to chemically manufacture bamboo fiber that are more benign and 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 manufacture TENCEL®, uses N-methylmorpholine-N-oxide to dissolve the bamboo cellulose into a viscose solution. N-methylmorpholine-N-oxide is a member of the amine oxide family. Amine oxides are weak alkalines that act as surfactants and help break down the cellulose structure. Hydrogen peroxide is added as a stabilizer and the solution is forced through spinnerets into a hardening bath which causes the thin streams of viscose bamboo solution to harden into bamboo cellulose fiber threads. The hardening bath is usually a solution of water and methanol, ethanol or a similar alcohol. The regenerated bamboo fiber threads can be spun into bamboo yarn for weaving into fabric. This lyocell processing is substantially healthier and more eco-friendly because N-methylmorpholine-N-oxide is supposedly non-toxic to humans and the chemical manufacturing processes are closed-loop so 99.5% of the chemicals used during the processing are captured and recycled to be used again. Only trace amounts escape into the atmosphere or into waste waters and waste products.
Other chemical manufacturing processes for bamboo fabric are appearing such as using acetic anhydride and acetic acid with sulfuric acid as a catalyst to form acetate fiber which is then spun into a yarn.
New nano-technologies are also being introduced into the bamboo clothing industry. GreenYarn, a new startup located in Boston, is developing a bamboo clothing line made from nano-particles of bamboo charcoal. GreenYarn’s “Eco-fabric” is manufactured from 4 to 5 year old Taiwanese-grown bamboo that has been dried and burned in 800 degree C ovens until it is reduced to charcoal. The bamboo is processed – we don’t know how – into fine nano particles which are then embedded into cotton, polyester or nylon fibers. This conventional fiber yarn that contains trapped bamboo charcoal nano particles is then woven into fabrics … mostly socks and blankets now.
Greenyarn’s Eco-fabric is promoted as being anti-bacterial, anti-fungal, anti-static, de-odorizing, breathable, thermal regulating (cool in hot weather and warm in cool weather), and environmentally friendly. Obviously, a significant part of Eco-fabric’s claims to sustainability depend upon the sustainability of the original cotton, polyester or nylon fibers that have been impregnated with the bamboo charcoal nano particles. In a footnote, Greenyarn mentions that the active bamboo charcoal ingredients will only remain active in the clothing for about six months of active use.
Chemically-manufactured bamboo rayon has some wonderful properties which are adored by conventional and eco-aware designers and consumers:
•Bamboo fabric has a natural sheen and softness that feels and drapes like silk but is less expensive and more durable.
•Bamboo clothing is easy to launder in a clothes washer and dryer.
•Because of the smooth and round structure of its fibers, bamboo clothing is soft and non-irritating, even to sensitive skin. Some people with chemical sensitivities can not tolerate bamboo clothing. We are not sure if this intolerance is due to the intrinsic nature of bamboo but it more likely because of other chemicals added or used during the manufacturing and finishing processes of the clothing.
•Bamboo is naturally anti-bacterial and anti-fungal supposedly because of a bacteriostatis agent unique to bamboo plants called “bamboo kun” which also helps bamboo resist harboring odors. “Kun” is also sometimes spelled “kunh”. The bamboo kun in bamboo fabric stops odor-producing bacteria from growing and spreading in the bamboo cloth allowing bamboo clothing to be more hygienic and to remain fresher smelling.
•Bamboo clothing is hypoallergenic.
•Bamboo is highly absorbent and wicks water away from the body 3 to 4 times faster than cotton. In warm, humid and sweaty weather, bamboo clothing helps keep the wearer drier, cooler and more comfortable and doesn’t stick to the skin.
•The structure of bamboo fibers make bamboo fabrics more breathable and thermal regulating than cotton, hemp, wool or synthetic fabrics.
•Bamboo clothing is naturally more wrinkle-resistant than cotton, and while it might still require ironing after washing, bamboo fabric can be ironed at a lower temperature than cotton. Shrinkage during washing and drying is minimal at warm temperatures.
•Bamboo fibers and fabrics absorb dyes faster and more thoroughly than cotton, modal and viscose with better color clarity. Bamboo fabrics do not need to be mercerized to improve their luster and dye-ability like cotton requires.
• Designers such as Kate O’Connor use bamboo fabric as an eco-friendly replacement for silk. Speaking of bamboo eco-fashion, Kate O’Connor calls bamboo fashion “so much cheaper [than silk] and it’s really good for the environment.” “It is the perfect summer fabric” according to Kate O’Connor. Linda Loudermilk, another savvy eco-fashion designer, frequently incorporates bamboo into her eco-fashions. Amanda Shi of Avita has some of the most exciting and originally beautiful eco-fashion in bamboo.
Bamboo the plant and also bamboo the fabric can rate high as an environmentally friendly and renewable resource:
•Bamboo grows rapidly and naturally without any pesticides, herbicides or fertilizers.
•Bamboo clothing (both mechanically and chemically manufactured) is 100% biodegradable and can be completely decomposed in the soil by micro-organisms and sunlight without decomposing into any pollutants such as methane gas which is commonly produced as a by-product of decomposition in landfills and dumps.
•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.
•Bamboo grows naturally without the need for agricultural tending and large diesel exhaust-spewing tractors to plant seeds and cultivate the soil.
•Bamboo plantations are large factories for photosynthesis which reduces greenhouse gases. Bamboo plants absorb about 5 times the amount of carbon dioxide (a primary greenhouse gas) and produces about 35% more oxygen than an equivalent stand of trees.
•Bamboo fabrics and clothing can be manufactured and produced without any chemical additives although eco-certification such as Oeko-Tex is necessary to insure that the manufacturing and finishing processes are healthy.
•Currently, there are no known genetically modified organisms (GMO) variants of bamboo. Let’s hope it stays that way.
The bottom line on bamboo. The growing of bamboo is environmentally friendly but the manufacturing of bamboo into fabric raises environmental and health concerns because of the strong chemical solvents used to cook the bamboo plant into a viscose solution that is then reconstructed into cellulose fiber for weaving into yarn for fabric.
Bamboo clothing marketers have found a variety of ways to put the most eco-friendly and sustainable face on the manufacturing of bamboo fabric. The dominant manufacturing process of hydrolysis alkalization and multi-phase bleaching is generally referred to as a rather benign process utilizing caustic soda and bleach. The chemicals used are known to create a variety of health problems and neural disorders which can be hazardous to the health of fiber manufacturing workers. If the manufacturing facility lacks adequate pollution control systems – all too common in developing countries where regulations and enforcement are nearly non-existent – then these toxic chemicals can escape into the atmosphere through air vents and smokestacks and into waterways through inadequately treated waste water disposal systems.
Some bamboo fiber manufacturing facilities trumpet their sustainability and green credentials by establishing ISO 9000 Quality Management policies and ISO 14000 Environmental Management policies. This is largely a PR red herring tossed by the manufacturing facilities and marketers because these ISO standards do not mean that the facilities, their manufacturing processes or their fabrics have been certified by any of the international certification bodies such as SKAL, Soil Association, Demeter, KRAV, or OKO-tex.
The International Organization for Standardization, ISO, is an international NGO that defines industrial and commercial standards. ISO 14000 gives the requirements for an Environmental Management System. This means that ISO 14000 “…is a tool for helping organizations to implement good environmental practice and to aim for continual improvement of their environmental performance” according to an ISO press release.
ISO 14000 does not certify that a company’s manufacturing processes are sustainable or environmentally friendly. ISO 14000 is simply a generic set of standards and tools to help businesses – any kind of business such as financial services or media companies and not just manufacturing companies – define their environmental concerns and how to meet them. ISO 14000 does not guarantee that once a company has defined their Environmental Management System that they will meet their goals. There is also no guarantee that a company’s implementation of their Environmental Management System using ISO 14000 will meet the criteria for sustainability. ISO has posted an interesting introduction to ISO 14000 on YouTube. Because ISO 14000 is a very “flexible” standard, it is impossible to know what and how a company is actually implementing their ISO 14000 Environmental Management System.
Some manufacturers also boast that they have implemented ISO 9000 as if this improves their “green” credentials. ISO 9000 is another set of generic standards and tools for defining and implementing a company’s quality management system. The domain of ISO 9000 is quality management and has nothing to do with environmental issues.
ISO 14000 and ISO 9000 are important and useful tools and standards but, without knowing the specifics of a company’s ISO 14000 implementation, it is impossible to know if their manufacturing processes are actually sustainable and conform to environmental regulations. Also, environmental regulations, controls, enforcement and attitudes vary greatly from country to country as does transparency into what really happens within a country’s manufacturing facilities. For example, getting reliable data and information from garment manufacturers in China, where most clothing is now manufactured, is very difficult.
What to do? If you are thinking of purchasing bamboo clothing or any clothing that has been made outside the U.S., look for certification from an independent and reliable certification company such as Oeko-Tex, Soil Association, SKAL, KRAV or similar organic or sustainable certification body. Currently, the Oeko-Tex label is the most comprehensive label for insuring that the garment is healthy for consumers but it does not certify the manufacturing processes that produced the garment as being environmentally friendly and sustainable.
Some people many find our critique of the environmental and human health impact of bamboo clothing to be harsh but we based our statements on the best research that we could find from medical research journals, trade information, patent applications and consumers’ experiences. We tried contacting a number of bamboo fiber manufacturers for additional information on their manufacturing processes but we received only bland statements about how they satisfied all governmental environment regulations or just radio silence. We would be highly appreciative of any documented facts from bamboo fiber and fabric manufacturers that correct any of our findings and we promise to publish your corrections. Bamboo fabric and clothing has wonderful potential as a sustainable and environmentally friendly product if it can demonstrate that it is sustainable and friendly to the health of the planet, manufacturing and garment workers, and consumers.