To polyester or not to polyester

19 04 2016

Give our retail website, Two Sisters Ecotextiles, a look and let us know what you think.

We are pondering about whether to sell polyester fabrics – largely because people are insisting on it. And there is a lot of polyester being produced:

polyester production

But, when (or if) we sell polyester fabric or blends, we have determined that the fabric must be GRS Gold level certified polyester, because:

  1. GRS is to synthetics as GOTS is to natural fibers.  It is our assurance:
    1. that there is water treatment in place,
    2. that no toxic additives are used as process chemicals, and no finishes (such as fire retardants or stain repellants) are added to the fabric,
    3. and that workers have basic rights.
  2. GRS provides verified support for the amount of recycled content in a yarn. It provides a track and trace certification system that ensures that the claim a fabric is made from recycled polyester can be officially backed up. Today, the supply chains for recycled polyester are not transparent, and if we are told that the resin chips we’re using to spin fibers are made from bottles – or from industrial scrap or old fleece jackets  – we have no way to verify that.  Once the polymers are at the melt stage, it’s impossible to tell where they came from.  So the yarn/fabric could be virgin polyester or it could be recycled.   Many so called “recycled” polyester yarns may not really be from recycled sources at all because – you guessed it! – the  process of recycling is much more expensive than using virgin polyester.  Unfortunately not all companies are willing to pay the price to offer a real green product, but they sure do want to take advantage of the perception of green.   So when you see a label that says a fabric is made from 50% polyester and 50% recycled polyester – well, (until now) there was absolutely no way to tell if that was true. In addition,

The Global Recycle Standard (GRS), originated by Control Union and now administered by Textile Exchange (formerly Organic Exchange), is intended to establish independently verified claims as to the amount of recycled content in a yarn, with the important added dimension of prohibiting certain chemicals, requiring water treatment and upholding workers rights, holding the weaver to standards similar to those found in the Global Organic Textile Standard:

  • Companies must keep full records of the use of chemicals, energy, water consumption and waste water treatment including the disposal of sludge;
  • All prohibitied chemicals listed in GOTS are also prohibited in the GRS;
  • All wastewater must be treated for pH, temperature, COD and BOD before disposal (It’s widely thought that water use needed to recycle polyester is low, but who’s looking to see that this is true?  The weaving, however, uses the same amount of water (about 500 gallons to produce 25 yards of upholstery weight fabric) – so the wastewater is probably expelled without treatment, adding to our pollution burden)
  • There is an extensive section related to worker’s rights.

Polyester is much (much, much, much!) cheaper than natural fibers and it wears like iron – so you can keep your sofa looking good for 30 years. The real question is, will you actually keep that sofa for 30 years?

There is still a problem with the production of synthetics. Burgeoning evidence about the disastrous consequences of using plastic in our environment continues to mount. A new compilation of peer reviewed articles, representing over 60 scientists from around the world, aims to assess the impact of plastics on the environment and human health [1] But synthetics do not decompose: in landfills they release heavy metals, including antimony, and other additives into soil and groundwater. If they are burned for energy, the chemicals are released into the air.

Also please keep in mind, that, if you choose a synthetic, then you bypass the benefits you’d get from supporting organic agriculture, which may be one of our most potent weapons in fighting climate change, because:

    1. Organic agriculture acts as a carbon sink: new research has shown that what is IN the soil itself (microbes and other soil organisms in healthy soil) is more important in sequestering carbon that what grows ON the soil. And compared to forests, agricultural soils may be a more secure sink for atmospheric carbon, since they are not vulnerable to logging and wildfire. The Rodale Institute Farming Systems Trial (FST) soil carbon data (which covers 30 years) demonstrates that improved global terrestrial stewardship–specifically including regenerative organic agricultural practices–can be the most effective currently available strategy for mitigating CO2 emissions.
    2. It eliminates the use of synthetic fertilizers, pesticides and genetically modified organisms (GMOs) which is an improvement in human health and agrobiodiversity
    3. It conserves water (making the soil more friable so rainwater is absorbed better – lessening irrigation requirements and erosion)
    4. It ensures sustained biodiversity

We’re not great fans of synthetics: Polyester is made from crude oil, and is the terminal product in a chain of very reactive and toxic precursors.   The manufacturing process requires workers and our environment to be exposed to some or all of the chemicals produced during the manufacturing process. There is no doubt that the manufacture of polyester is an environmental and public health burden that we would be better off without.

But there is a great quantity of existing polyester on this Earth, and there is only so much farmland that is available for cotton and other fiber crops, even though we have enough land to grow all the food and fiber we like, at least in theory.[2]

The biggest drawback to polyester production is that it requires a lot of energy, which means burning fuel for power and contributing to climate change. But to put that in perspective, Linda Greer, director of the health program at the Natural Resources Defense Council, says you actually release more carbon dioxide burning a gallon of gas than producing a polyester shirt.

However factories where polyester is produced which do not have end-of-pipe wastewater treatment systems release antimony along with a host of other potentially dangerous substances like cobalt, manganese salts, sodium bromide, and titanium dioxide into the environment.

In theory, cotton is biodegradable and polyester is not. But the thing is, the way we dispose of clothing makes that irrelevant. For cotton clothes to break down, they have to be composted, which doesn’t happen in a landfill.

The bottom line is that while the rise of polyester is not good news for the planet, a big increase in cotton production wouldn’t be any better, according to many sources: Both fabrics are created in huge factory plants, both go trough multiple chemical processes to make the final product, and both will be shipped around the globe.         (https://www.sewingpartsonline.com/blog/411-cotton-vs-polyester-pros-cons/)

But we keep returning to one point: there are already polyester bottles in existence. World demand for polyester in 2014 was a bit more than 46 million tons.[3] Only a small percentage of that is used for bottles, but that’s still a lot of bottles – in the United States, more than 42 billion bottles of water (only water!) were produced in 2010.[4] Doesn’t it make sense to re-use some of these bottles?

Mulling over the possibilities. Let us know how you feel.

[1] “Plastics, the environment and human health”, Thompson, et al, Philosophical Transactions of the Royal Society, Biological Sciences, July 27, 2009

[2] Atkisson, Alan, “Food, Fuel and Fiber? The Challenge of Using the Earth to Grow Energy”, December 2008, worldchanging.com

[3] Carmichael, Alasdair “Man made Fibers Continue to Grow”, Textile World, http://www.textileworld.com/Issues/2015/_2014/Fiber_World/Man-Made_Fibers_Continue_To_Grow

[4] http://www.container-recycling.org/images/stories/BUfigures/figure-pngs-new/figure4.png





Should I choose a hemp or linen fabric?

5 08 2015

We are often asked for 100% hemp fabric in lieu of linen fabrics. We offer hemp and adore it, but it may not be the best eco choice.  Make no mistake – we love hemp, we sell hemp fabrics and we think the re-introduction of hemp as a crop would be a boon for American farmers and consumers.

But hemp that is used to produce hemp fabric via conventional methods – as opposed to GOTS methods – is an inferior choice to any GOTS certified fabric. So the overriding difference is not between hemp and any other fiber, but between a GOTS certified fabric versus one that is not GOTS certified, because GOTS certification assures us that the fabric is free of any chemicals that can change your DNA, give you cancer or another dread disease or affect you in other ways ranging from subtle to profound. It also assures us that the mill which produced the fabric has water treatment in place, so these chemicals don’t pollute our groundwater – and that the mill pays fair wages to their workers who toil in safe conditions!

The GOTS certification requires that the fiber used in the fabric be third party certified organic. Organic linen is more available and less expensive then organic hemp, so we often use linen instead of hemp in our fabrics. Using organic linen instead of organic hemp keeps the price lower for you and you do not give up any performance characteristics at all.   Allow me to say that once more: You do not give up any performance at all.

To begin with, do not be confused by the difference between the fiber and the cloth woven from that fiber – because the spinning of the yarn and the weaving of the cloth introduces many variables that have nothing to do with the fibers. Both hemp and flax (from which linen is derived) are made from fibers found in the stems of plants, and both are very laborious to produce. The strength and quality of both fibers are highly dependent on seed variety, the conditions during growth, time of harvest and manner of retting and other post-harvest handling.

Yarns, made from the fibers, are graded from ‘A’, the best quality, to below ‘D’ and the number of twists per unit length is often (but not always) an indication of a stronger yarn.   In addition, the yarns can be single or plied – a plied yarn is combined with more than one strand of yarn. Next, the cloth can be woven from grade ‘A’ yarns with double twist per unit length and double ply into a fabric where the yarns are tightly woven together from cloth that is lightweight or heavier, producing a superior fabric.  Or not.

Now let’s look at some of the differences between hemp and linen:

Hemp and linen fibers are basically interchangeable – there is very little to distinguish flax fibers from hemp fibers.  In fact,  hemp’s fibers so closely resemble flax that a high-power microscope is needed to tell the difference. Without microscopic or chemical examination, the fibers can only be distinguished by the direction in which they twist upon wetting: hemp will rotate counterclockwise; flax, clockwise.  And in general, they tend to have the same properties.

In general, there are many similarities between cloth made from hemp and cloth made from linen:

  • Both linen and hemp become soft and supple through handling, gaining elegance and creating a fluid drape.
  • Both hemp and linen are strong fibers – though most sources say hemp is stronger (by up to 8 times) than linen (even though the real winner is spider silk), but this point becomes moot due to the variables involved in spinning the fiber into yarn and then weaving into fabric.   The lifespan of hemp is the longest of all the natural fibers.
  • Both hemp and linen wrinkle easily.
  • Both hemp and linen absorb moisture. Hemp’s moisture retention is a bit more (12%) than linen’s (10 – 12%)
  • Both hemp and linen breathe.
  • Both hemp and linen are natural insulators: both have hollow fibers which means they’re cool in summer and warm in winter.
  • Both hemp and linen have anti-bacterial properties.
  • Both hemp and linen benefit from washing, becoming softer and more lustrous with each wash.
  • Both hemp and linen are resistant to moths and other insects.
  • Both hemp and linen absorb dyestuffs readily.
  • Both hemp and linen biodegrade.

In general, hemp fiber bundles are longer than those of flax.   So the first point of differentiation is this: the length of the fibers. Hemp fibers vary from 4 to about 7 feet in length, while linen is general 1.5 to 3 feet in length. Other differences:

  • The color of flax fibers is described as yellowish-buff to gray, and hemp as yellowish-gray to dark brown.
  • Hemp is highly resistant to rotting, mildew, mold and salt water.
  • Hemp is also highly resistant to ultraviolet light, so it won’t fade or disintegrate in sunlight.
  • Hemp’s elastic recovery is very poor and less than linen; it stretches less than any other natural fiber.

The biggest difference between hemp and linen might be in the agricultural arena: Hemp grows well without the use of chemicals because it has few serious pest problems, although the degree of immunity to attacking organisms has been greatly exaggerated.  Several insects and fungi specialize exclusively in hemp!  But despite this, the use of pesticides and fungicides are usually unnecessary to get a good yield. Hemp has a fiber yield that averages between 485 – 809 lbs., compared to flax, which averages just 323 – 465 lbs. on the same amount of land.  This yield translates into a high biomass, which can be converted into fuel in the form of clean-burning alcohol.

Farmers claim that hemp is a great rotation crop – it was sometimes grown the year prior to a flax crop because it left the land free of weeds and in good condition.   Hemp, it was said, is good for the soil, aerating and building topsoil. Hemp’s long taproot descends for three feet or more, and these roots anchor and protect the soil from runoff. Moreover, hemp does not exhaust the soil. Additionally, hemp can be grown for many seasons successively without impacting the soil negatively. In fact, this is done sometimes to improve soil tilth and clean the land of weeds.

The price of hemp in the market is far higher than for linen, despite hemp’s yields.   We have no idea why this is so.

The overriding difference is not between hemp and linen, but between a hemp OR linen fabric that has a GOTS certification and one that does not. That means that a conventional hemp fabric, which enjoys all the benefits of hemp’s attributes, also introduces unwanted chemicals into your life: such as formaldehyde, phthalates, heavy metals, endocrine disruptors and perhaps soil or fire retardants.   The GOTS certified fabric is the better choice. If the choice is between a conventional hemp fabric and a GOTS certified linen fabric, we wouldn’t hesitate a second to choose the linen over the hemp, especially because hemp and linen are such close cousins.

 

 

 

 

 

 





Bioplastics

9 04 2012

The first plastic garbage bag was invented by Harry Waslyk in 1950.

1950!  Mr. Waslyk could not have predicted how much havoc his plastic child would wreck in a mere 62 years.[1]

We’ve all seen the pictures of birds stomachs filled with plastic detritus and read about the Great Pacific Gyre, but I just read a new twist to that story:    the Emirates News Agency reported that decomposed remains of camels in the desert region of the United Arab Emirates revealed that 50% of the camels died from swallowing and choking on plastic bags.  “Rocks of calcified plastic weighing up to 60 kilograms are found in camel stomachs every day,” said Dr. Ulrich Wernery, Scientific Director, Central Veterinary Research Laboratory in Dubai, whose clinic conducts hundreds of post-mortems on camels, gazelles, sheep and cows in the UAE.  He adds that one in two camels die from plastic.[2]

Plastic has become so ubiquitous, in fact, that plastics are among the debris orbiting our planet. Unfortunately, our wildlife and domestic animals are paying the price now; I think we ourselves will see changes in future generations.

It’s no wonder we’re scrambling to find alternatives to plastic, and one hot topic in the research area is that of bioplastics.

Bioplastics are made (usually) from plant materials.  Enzymes are used to break starch in the plant into glucose, which is fermented and made into lactic acid.  This lactic acid is polymerized and converted into a plastic called polylactic acid (PLA), which can be used in the manufacture of products  ( PLA is about 20% more expensive than petroleum-based plastic)  or into a plastic  called polyhydroxyalkanoate, or PHA (PHA biodegrades more easily but is more than double the price of regular plastic).

The bioplastic market is expanding rapidly and by 2030, according to some estimates, could account for 10% of the total plastics market.   In the world of fabrics and furnishings, the new biotech products which are being heavily promoted are Ingeo and Sorona, both PLA based fibers with a growing share of the fabric market; and soy-based foam for upholstery.    Toray Industries has announced that they will have the first functional performance nylon and polyester textiles based on biomass ready for the 2013/14 season.  They are 100% bio-based fabrics [3] based on the castor plant, which is very robust, growing in dry farming areas and requiring significantly fewer pesticides and herbicides than other crops.

So it’s no wonder that there has been much discussion about bioplastics, and about whether there are ecological advantages to using biomass instead of oil.

The arguments in favor of bioplastics are:

  • They are good for the environment because there is no harm done to the earth when recovering fossil fuels. Also, in this process there are very few greenhouse gas and harmful carbon emissions. Regular plastics need oil for their manufacturing, which pollutes the environment.
  • They require less energy to produce than petroleum-based plastics.
  • They are recyclable.
  • They are non toxic.
  • They reduce dependence on foreign oil.
  • They are made from renewable resources.

These arguments sound pretty good – until you begin to dig  and find out that once again, nothing is ever as simple as it seems.

Regarding the first two arguments (they are good for the environment because they produce significantly fewer CO2 emissions and less energy) –  there have not been many studies which support  this argument until recently.  Recently,  several  studies have been published which seems to support that  this is indeed the case:

  1. 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.”[4]
  2. University of Pittsburgh researchers did an LCA on the environmental impacts of both petroleum and bio derived plastics, assessing them using metrics which included  economy, mass from renewable sources, biodegradability, percent recycled, distance of furthest feedstock, price, life cycle health hazards and life cycle energy use. They found that  biopolymers are the more eco-friendly material in terms of energy use and emissions created.  However, they also concluded that traditional plastics can actually be less environmentally taxing to produce when taking into account such things as acidification, carcinogens, ecotoxicity, eutrophication, global warming, smog, fossil fuel depletion, and ozone depletion.[5]
  3. A study done by the nova-Institut GmbH on behalf of Proganic GmbH & Co.[6]showed unambiguously positive eco advantages (in terms of energy use and CO2 emissions) for bio based polymers PLA and PHA/PHB over petrochemical based plastics.  According to the report, “the emission of greenhouse gases and also the use of fossil raw materials are definitely diminished. Therefore the substitution of petrochemical plastics with bio-based plastics yields positive impacts in the categories of climate change and depletion of fossil resources.”  The results include:
    1. Greenhouse gas emissions of bio-based plastics amount to less than 3 KG of CO2 equivalents per KG of plastic, less than that of petrochemical based plastics which produce an average of 6 KG of CO2 equivalents per KG of plastic..
    2. the production of bio-based polymers, in comparison to all petrochemical plastics examined, leads to savings in fossil resources. The biggest savings potential can be found in comparison with polycarbonate (PC). The average savings potential in the production of PLA amounts to 56 ± 13 megajoules per kilogram of plastics here.
    3. The production of bio-based polymers in comparison with the production of petrochemical plastics in most cases also leads to greenhouse gas emission savings. The biggest greenhouse gas emission savings can be found again when comparing bio-based polymers to polycarbonate (PC). For PLA, the average savings potential in this case amounts to 4.7 ± 1.5 kilograms of CO2 equivalents per kilogram of plastics. For PHA, the average savings potential in this case amounts to 5.8 ± 2.7 kilograms of CO2 equivalents per kilogram of plastics. In comparison with PET and Polystyrene (PS), considerable savings potentials ranging between 2.5 and 4.2 kilograms of CO2 equivalents per kilogram of plastics are to be found in the production of bio-based polymers. The lowest savings potential are to be found when comparing bio-based polymers with polypropylene (PP).

So I will accept the arguments that biobased plastics produce fewer  greenhouse gases and harmful carbon emissions and require less energy to produce than petroleum-based plastics .  They also certainly reduce our dependence on foreign oil.

But are they better for the environment?  Are they recyclable or biodegradeable?  Are they safe?  Are plastics producers aware of the impact of promoting bioplastics as a replacement for plastics? We think that  bioplastics are useful for certain purposes, such as medical sutures or strewing foil for mulching in agriculture – but as a replacement for all plastics?

Next week we’ll take a look at the arguments against bioplastics.


[1] Laylin, Tafline, “Half of UAE’s Falaj Mualla Camels Choked on Plastic Bags”, Green Prophet blog, June 11, 2010.

http://www.greenprophet.com/2010/06/camels-choke-on-plastic/

[2] Ibid.

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

[5] Tabone, Michaelangelo D., et al; “Sustainability Metrics: Life Cycle Assessment and Green Design in Polymers”, Enviornmental Science and Technology, September 2, 2010.





Biodegradeable or compostable?

1 12 2010

There is no legal definition of “biodegradable,” so the term has been used loosely by some manufacturers.  The American Society for Testing and Materials defines the term as “a degradation caused by biological activity, especially by enzymatic action, leading to a significant change in the chemical structure of the material.”

The Biodegradable Products Institute (BPI) cites a 2006 American Chemistry Council study showing that most consumers believe a product labeled “biodegradable” will go away completely and on its own in a year or less. The BPI says many consumers also believe that these products will “biodegrade” in landfills.

Because it seems a desirable product attribute, the term “biodegradable” has been applied to a wide range of products—even those that might take centuries to decompose, or those that break down into harmful environmental toxins.   Biodegradability is definitely perceived as  a positive trait, yet it could be applied to virtually anything because anything is biodegradable, given enough time.  The Federal Trade Commission (FTC) in the U.S., however, has issued some general guidelines on what types of products qualify as legitimately biodegradable, and has even sued companies for unsubstantiated, misleading and/or deceptive use of the term on product labels.

According to the FTC, only products that contain materials that “break down and decompose into elements found in nature within a reasonably short amount of time after customary disposal” should be marketed as “biodegradable.”

But the FTC acknowledges that even products appropriately labeled as biodegradable may not break down easily if they are buried under a landfill or are otherwise not exposed to sunlight, air and moisture, the key agents of biodegradation. In fact, in landfills materials degrade very, very slowly – if at all!  This is because modern landfills are designed, according to law, to keep out sunlight, air and moisture – the very ingredients needed for materials to biodegrade. This helps prevent pollutants from the garbage from getting into the air and drinking water, and slows the decomposition of the trash. In Dr. William Rathje’s book entitled “Rubbish,” he sites that “The truth is, however, that the dynamics of a modern landfill are very nearly the opposite of what most people think…Well designed and managed landfills seem to be far more apt to preserve their contents for posterity than transform them into humus or mulch. They are not vast composters: rather they are vast mummifiers.” In his book, Dr. Rathje talks about doing excavations on 15 landfills throughout North America. From those digs, they found 40 year old newspapers that were still legible, 5 year old lettuce and a 15 year old hot dog. From these studies it seems fairly clear that even organic materials take a very long time to break down in landfills let alone plastic or other items.  The reality is if any product ends up in a landfill, it will not degrade.

But the fact that a product breaks down – if it does indeed break down – may not be as important as what the product breaks down into. In a perfect would all products would break down to CO2 and H2O. But it gets more complicated as we increase the number and kinds of chemicals. The banned pesticide DDT is hazardous and toxic in its own right. And it does biodegrade, though rather slowly. The problem is that its breakdown products of DDD and DDE are even more toxic and dangerous than the original DDT.
So just because a product or ingredient is biodegradable does not mean it is healthy or safe for people or the environment – especially if it leaches harmful chemicals into the ecosystem. Under this definition, even regular oil based plastic can be advertised as “biodegradable” because at some point, sooner or later, it is going to break down into small pieces.

“Compostable”, on the other hand, has a definition that is rigorously governed by the standards ASTM D-6400, ASTM D6868, and EN13432.   The term “compostable” covers four areas:

1.      Biodegradable – i.e.,  60 – 90% of the product will break down into CO2 within 180 days in a commercial composting facility.

2.      Disintegration – this requires that 90% of the product will break down into pieces that are 2mm or smaller

3.      Eco-toxicity – the product will not deposit heavy metals that are toxic to the soil beyond that found in typical compost.

4.      Compostable products have the added implication that when they break down they turn into humus, which provides valuable nutrients to the soil.

So, while some products are considered biodegradable, they may not be considered compostable because they either don’t meet the heavy metal requirements,  don’t break down in a timely fashion or don’t contribute valuable nutrients which improves the soil.

Composting of organic waste makes sense, but compostable plastic for shopping bags, food packaging, fabric, etc. does not, because:

1.      It is up to 400% more expensive than ordinary plastic;

2.      it is thicker and heavier and requires more trucks to transport it;

3.      recycling with oil-based plastics is impossible;

4.      it uses scarce land and water resources to produce the raw material, and substantial amounts of non-renewable hydro-carbons are burned and CO2 emitted, by the tractors and other machines employed.

5.      If buried in landfill, compostable plastic can emit methane (a greenhouse gas 23 times more powerful than CO2) in anaerobic conditions.

Many industrial composters of organic waste around the world do not want plastic of any kind in their feedstock, because it is difficult to separate biodegradable plastic from ordinary plastic. Home composting of plastic is not encouraged, as it will often be contaminated with food residues, and temperatures may not rise high enough to kill the pathogens. Compostable plastic is useless in compost because 90% of it has to convert to CO2 gas in order to comply with ASTM D6400 and the other composting Standards. It therefore contributes to greenhouse gases but not to the improvement of the soil.

Meanwhile, you can follow Dave, who  buried an advertised Paper Mate  biodegradable pencil in his backyard last summer and says he will report on it’s degradation over time.  Click here to read more and follow the story!

So how does this apply to fabrics?  Well, for starters the companies that make PLA (polylactic acid) based polymers – those corn based bio plastics – advertise that their products are biodegradable.   PLA is said by the manufacturer  to decompose into carbon dioxide and water in a “controlled composting environment” in fewer than 90 days. What’s a controlled composting environment? It’s not exactly your average backyard bin, pit or tumbling barrel. It’s a large facility where compost—essentially, plant scraps being digested by microbes into fertilizer—reaches 140 degrees for ten consecutive days. So, yes, as PLA advocates say, corn plastic is “biodegradable.” But in reality very few consumers have access to the sort of composting facilities that can make that happen. NatureWorks (the largest manufacturer of PLA, owned by Cargill Dow)  has identified only  113 such facilities nationwide.

Moreover, PLA by the truckload may potentially pose a problem for some large-scale composters.  And there is no evidence that  PLA breaks down any faster than PET or other plastics in a normal landfill environment.  (Read more about PLA and biodegradability here.)

And unless the chemicals used during processing of your fabric are such that there are no chemicals which would combine with other chemicals to form molecules of anything other than water, carbon dioxide and safe organic material – then it cannot be called compostable.  If the chemicals used during processing contain, for example, heavy metals in the dyestuffs – then those metals become available to your plants in the garden – and that again knocks it out of the “compostable” set of products.  That might be o.k. if you’re growing roses rather than radishes, but if you plan to eat those plants I’d look elsewhere as a way to dispose of your fabric.  Certified fabrics  made of natural fibers which look at the chemical inputs of processing (such as GOTS and Oeko Tex) would be o.k. for use in a vegetable garden – because they have been tested to be free of toxic inputs – and they could be called “compostable”.

Resources:

The Biodegradable Products Institute, www.bpiworld.org

US Composting Council  http://www.compostingcouncil.org