Eucalyptus fiber by any other name

2 03 2012

Fibers are divided into three main categories:

  • Natural – like flax, wool, silk and cotton
  • Manufactured – made from cellulose or protein
  • Synthetic – made from synthetic chemicals

The difference between “manufactured” and “synthetic” fibers is that the manufactured fibers are derived from naturally-occurring cellulose or protein, while synthetic fibers are not.  And  manufactured fibers are unlike  natural fibers because they require extensive processing (or at least more than is required by natural fibers) to become the finished product.  The category of “manufactured” fibers is often called “regenerated cellulose” fibers.  Cellulose is a carbohydrate and the chief component in the walls of plants.

Rayon is the oldest manufactured fiber, having been in production since the 1880s in France, where it was originally developed as a cheap alternative to silk.   Most rayon production begins with wood pulp, though any plant material with long molecular chains is suitable.

There are several chemical and manufacturing techniques to make rayon, but the most common method is known as the viscose process. In the viscose process, cellulose is treated with caustic soda (aka: sodium hydroxide) and carbon disulfide, converting it into a gold, highly viscous  liquid about the color and consistency of honey.  This substance gives its name to the manufacturing process, called the viscose process.

The viscous fluid is allowed to age, breaking down the cellulose structures further to produce an even slurry, and is then filtered to remove impurities.  Then the mixture 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.

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)  Suddenly, bamboo was the darling of marketers, and the FTC had to step in to remind manufacturers to label their products as “bamboo viscose” rather than simply bamboo.

Now we hear about fabrics made from  eucalyptus, or soy.  But it’s the same story – the fibers are created using the viscose process.  Because the FTC did not specifically name these two substances in their proclamation regarding bamboo,   marketers can claim fabrics are  “made from eucalyptus”.    The reality is that the viscose process can produce fibers from any cellulose or protein source – chicken feathers, milk and even bacteria have been used (rayon comes specifically from wood or cotton).  But those inputs are not nearly as exciting to the marketers as eucalyptus or soy, so nobody has been advertising fibers made from bacteria.

After the brouhaha about bamboo viscose hit the press, many people did a quick scan of viscose and declared it “unsafe” for the environment.  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.  But 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 environmental burden 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.  And there are emissions of these chemicals as well, which contribute to greenhouse gasses.  And the reason that these fibers can be Oeko Tex certified:  Oeko Tex certifies only the final product, i.e.,the fibers or the fabric.  They do not look at the production process, which is where the majority of the environmental burden is found.  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.

Certainly the standard viscose production process is definitely NOT environmentally friendly, but then there is Tencel ® and Modal ®.   These fibers are manufactured by the Austrian company Lenzing, which  advertises its environmentally friendly production processes, based on closed loop systems.  Lyocell is the generic name for the fibers produced by Lenzing, which are not produced by the traditional viscose process but rather by solvent spinning.

According to Lenzing:

  • There is an almost complete recovery of the solvent, which both minimizes emissions and conserves resources.  Lenzing uses  a new non-toxic solvent (amine oxide) and the cellulose is dissolved in N-Methylmorpholine N-oxide rather than sulfuric acid. Water is also evaporated, and the resulting solution filtered and extruded as filaments through spinnerets into an aqueous bath. Over 99% of the solvent can washed from the fiber and purified for re-use. The water is also recycled.
  •  The by products of production, such as acetic acid, xylose and sodium sulphate are key ingredients in the food and glass industry. Remaining materials are used as energy for the Lenzing process.
  • Tencel ® is made from eucalyptus, which is grown on marginal land unsuitable for food crops; these trees are grown with a minimum of water and are grown using sustainable forestry initiatives.
  • The final fibers are biodegradable and can decompose in soil burial or in waste water treatment plants.

So Lenzing fibers can be considered a good choice if you’re looking for a sustainable fiber – in fact there is a movement to have Lenzing Tencel® eligible for GOTS certification, which we support, because the production of these fibers conforms with the spirit of GOTS.  They already have the EU Flower certification.

But Lenzing does not make fabrics – it sells yarns to mills and others which use the yarns to make fabric and other goods.

So  we’re back to the beginning again, because people totally forget about the environmental impact in the weaving of fibers into fabric, where the water and chemical use is very high –  if done conventionally, the environmental burden is devastating  and the finished fabric itself probably contains many chemicals which are outlawed in other products.

It’s critically important to look at both the fiber as well as the weaving in order to make a good choice.

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Biopolymers and polylactic acid (PLA) – or rather, Ingeo

27 04 2011

Synthetic polymers have experienced almost exponential growth since 1950, and today about 5% of world oil production is used for that purpose.  In fact, we will need 25% or more of the current oil production for making polymers by the end of this century.

Some synthetic polymers are used to make fibers, and they have been around for a while:  rayon was discovered in 1924 and nylon in 1939.  But synthetic use really began to take off only since about 1953,  when polyester was discovered.  Qualities like durability and water resistance make synthetics highly desirable in many applications.  Today synthetics account for about half of all fiber usage.

This, despite the fact that synthetics are made from fossil fuel, and the contaminants from the manufacturing leach into our waterways and pollute the atmosphere, and the fact that they are not biodegradable and therefore don’t break down in landfills.  So recently there has been a spotlight on bio-plastics.

Bio plastics, or biopolymers –  in other words, synthetic plastics produced from biological sources –  are derived from cellulose. Cellulose is abundant – it’s said to make up half of all the organic carbon on the planet.   The most often-used biopolymers  include:

  • natural rubber (in use since the mid-1700s),
  • cellulosics (invented in the late-1800s),
  • and nylon 11 (polyamide – or PA 11) and 6–10 (polyamide 6/10) (mid-1900s).

A recent addition to the list is polylactic acid (PLA).  PLA is made from corn starch (in the United States), tapioca products (roots, chips or starch, mostly in Asia) or sugar cane (the rest of the world).[1]  You’ve probably heard about polylactic acid (PLA),  because Cargill, one of the largest agricultural firms on Earth, has invested heavily in it.  Cargill’s wholly owned subsidiary, NatureWorks, is the primary producer of PLA in the United States.  The brand name for NatureWorks PLA is Ingeo, which is made into a whole array of products, including fabrics.

The producers of PLA have touted the eco friendliness of PLA based on:

  1. the fact that it is made from annually renewable resources ,
  2.  that it will biodegrade in the environment all the way to carbon dioxide and water  –  at least in principle, and
  3. they also cite PLA’s lower carbon footprint.

Let’s take a look at these three claims.

Plant based biopolymers do come from renewable resources, but the feedstock used presents some interesting problems.  In the United States, corn is used to make the PLA. In the US, corn-based biopolymer producers have to compete with ethanol producers of government mandated gasoline blends, raising the cost and limiting availability for both. This problem will become worse in the future as the law requires a doubling of the percentage of ethanol used in motor fuel. Nearly a third of the US corn crop previously used for food was used to replace 5% of gasoline consumption in 2008.[2]

In a world where many people are starving, many say that it seems almost criminal to grow food crops, such as corn, to turn it into cloth. Agricultural lands are often cleared to make way for the growing of crops for the production of polymers. This leads to a continuous shrinking of the food producing lands of the world.  Lester Brown, president of the Earth Policy Institute, says, “already we’re converting 12% of the US grain harvest to ethanol (anticipated to rise to 23% by 2014). How much corn do we want to convert to nonfood uses?”[3]

In addition, most of the corn used by NatureWorks to make PLA is genetically modified, which raises serious ethical issues.

Other critics point to the steep environmental toll of industrially grown corn. The cultivation of corn uses more nitrogen fertilizer, more herbicides and more insecticides than any other U.S. crop; those practices contribute to soil erosion and water pollution when nitrogen runs off fields into streams and rivers.

PLA is said to decompose into carbon dioxide and water in a “controlled composting environment” in 90 days or less.  What’s that?  Not exactly your backyard compost heap!  It’s an industrial facility where microbes work at 140 degrees or more for 10 consecutive days.  In reality very few consumers have access to the sort of composting facilities needed to degrade PLA.  NatureWorks has identified 113 nationwide – some handle industrial food-processing waste or yard trimmings, others are college or prison operations .  Moreover, PLA in quantity can interfere with municipal compost operations because it breaks down into lactic acid, which makes the compost wetter and more acidic.

It looks like most PLA will end up in landfills, where there is no evidence it will break down any faster than PET.  Glenn Johnston, manager of global regulatory affairs for NatureWorks, says that a PLA container dumped into a landfill will last as long as a PET bottle.[4]

In fact, manufacturers have changed their stance: PLA is now defined as “compostable” instead of biodegradable, meaning more heat and moisture is needed to degrade PLA than is found in your typical backyard compost bin.

So far, biopolymer producers have had problems demonstrating that their materials have smaller carbon footprints than fossil fuel-derived polymers.   The energy inefficiencies of planting, growing, and transporting biological feedstocks mean more total energy is likely consumed to produce a unit of biopolymer than to make a unit of an oil or gas-based polymer.

However, Ramani Narayan of Michigan State University  found that “the results for the use of fossil energy resources and GHG emissions are more favorable for most bio based polymers than for oil based. As an exception, landfilling of biodegradable polymers can result in methane emissions (unless landfill gas is captured) which may make the system unattractive in terms of reducing greenhouse gas emissions.”[5]

Dr. Narayan recommended that, relative to their conventional counterparts, green polymers  should:

  • save at least 20 MJ (non-renewable) energy per kg of polymer,
  • avoid at least 1 kg CO2 per kg polymer and
  • reduce most other environmental impacts by at least 20%.

From this point of view, he says,  green plastics  can be defined in a broad and target-oriented manner.

But  carbon footprints may be an irrelevant measurement, because it has been established that plants grow more quickly and are more drought and heat resistant in a CO2 enriched atmosphere. Many studies have shown that worldwide food production has risen, possibly by as much as 40%, due to the increase in atmospheric CO2 levels. Therefore, it is both ironic  and a significant potential problem for biopolymer production if the increased CO2 emissions from human activity were rolled back, causing worldwide plant growth to decline.  This in turn would greatly increase the  competition for biological sources of food and fuel –  with biopolymers coming in last place.[6]

A further problem with biopolymers (except for future PE/PP made from sugar cane) is that  they require additional sorting at commercial recycling centers to avoid contaminating other material streams, and, although segregated collection helps, it is complex and increases costs.

In the final analysis, newer biopolymers don’t yet perform as well as oil based polymers, especially in terms of lower heat and moisture resistance, so the user might feel green but gets results that are less sustainable and more limited in use.  PLA remains a boutique polymer, and some see the best value proposition for biopolymers to be where their use is based on their unique properties, such as in medical and dental implants, sutures, timed released chemotherapy, etc. , because  PLA will slowly come apart in the body over time, so it can serve as a kind of scaffold for bone or tissue regrowth or for metered drug release.  But this is a small and specialized market.

But still, the potential and need for plastic alternatives has become acute:  The SPI Bioplastic Council anticipates that the biopolymer market will exceed $1 billion by 2012 – today it is half that.   Bioplastic remains “a sector that is not yet mature but will be growing fast in the coming years,” says Frederic Scheer , CEO of Cereplast and the so-called ‘Godfather of Bioplastics.’  It has not matured because of high production costs and the restricted capacity of biomass-based polymers.

But  according to The ETC Group, there are already concerted efforts, using biotechnology,  to shift global industrial production from a dependence on fossil fuels to biomass – not only for plastics but also for power, chemicals, and more.  It sounds good – until you read their report, which I’ll cover next week.


[2] Jones, Roger, “Economics, Sustainability, and the Public Perception of Biopolymers”, Society of Plastics Engineers, http://www.4spepro.org/pdf/000060/000060.pdf

[3] Royte, Elizabeth, “Corn Plastic to the Rescue”, Smithsonian,  August 2006

[4] Ibid.

[5] Narayan, Ramani, “Review and Analysis of Bio-based Product LCA’s”, Department of Chemical Engineering & Materials Science, Michigan State University, East Lansing, MI 48824

[6] D. B. Lobell and C. B. Field, Global scale climate-crop yield relationships and the impacts

of recent warming, Env. Res. Letters 2, pp. 1–7, 2007  AND

L. H. Ziska and J. A. Bunce, Predicting the impact of changing CO2 on crop yields:

some thoughts on food, New Phytologist 175, pp. 607–618, 2007.