As I have mentioned each time, Marketplace is a 22 minute show and they did a 10-product countdown, giving them an average of about 2 minutes per product, so they had to leave a lot of information out. This series is me looking to see what other information is out there.
The Eco Collection bath mitt is, according to the manufacturer's product page, a natural bamboo fiber and natural cotton product. They claim antibacterial properties for the natural bamboo fiber, and that it's made using rayon from bamboo.
Marketplace claims that bamboo can be grown sustainably but requires "funky chemical processing" to make a nice soft fiber, and the product package is unrecyclable vinyl.
This may well be the shortest segment they did of the ten—basically saying the above, then moving on. (I didn't time the segments.)
So, I'm going to look at exactly what's so "funky" about the chemical processing required to turn bamboo fiber into rayon.
The primary feedstock for rayon is cellulose, which can be purified from just about any plant, though some are easier than others. Cotton is already nearly pure cellulose when you pick it off the plant, while wood has a lot of other things mixed in (such as lignin) that needs to be removed first. Bamboo likewise has a fair bit of lignin. So, the first step in converting bamboo to rayon is purifying it down to something that is more or less nothing but cellulose. This looks very similar to the chemical wood pulping process for papermaking, although apparently the purity and quality of the cellulose has to be higher than that used for paper. Kraft pulping is a very interesting process in its own right, because it recycles and regenerates a very large portion of its own reagents using self-produced power and often puts power back to the grid instead of consuming it, giving it a (relatively) small ecological footprint. Some of the chemicals used are dangerous, but the pulp is carefully washed to make sure it is all recovered for internal re-use. That stuff can get expensive, so they don't want to lose it to the product.
Once the bamboo is purified down to just cellulose fibers, the actual rayon production process starts. From this point on, it doesn't look to me as though it matters if the source of the cellulose is wood, bamboo, cotton, or any other plant source. Maybe an expert in rayon production can tell us if it's possible to tell the source of the cellulose fibers at this stage, if one happens to be reading here.
Cellulose structure courtesy of Wikimedia Commons.
Viscose rayon, the most common rayon process, has quite a few steps. In terms of eco-friendliness, we want to look at chemicals used, waste emissions, and power consumption.
The chemicals used are:
- NaOH, sodium hydroxide (caustic, caustic soda, lye)
- This prepares the cellulose chains for later reactions, by converting some of the cellulose into sodium salts of cellulose: turning some of the -OH groups sticking out of the chain into -O.Na groups instead; the H knocked off of the cellulose would combine with the OH from the sodium hydroxide to make water. NaOH is highly water soluble and any unreacted chemical can be very easily washed out of the product. NaOH is not toxic so much as highly corrosive and reactive; its danger lies in the fact that at high concentrations it turns fat into soap and even at low concentrations it can raise the pH of a local area outside the range the creatures exposed to it can survive. According to the process description linked above, the caustic is squeezed out of the cellulose, not washed out, so there's a good chance anything that didn't react can be recycled back instead of discarded, and mixed with enough fresh caustic to make up what was reacted.
- O2, oxygen
- This chops the cellulose chains into shorter lengths. It's apparently not explicitly added, they just expose the dried product to open air and let it pull in what oxygen it needs. Oxygen is highly reactive and corrosive too, but a lot of life depends on it. It doesn't look like there's anything volatile in the product at this point, so probably no air emissions from this step.
- CS2, carbon disulphide
- This boots the Na off the oxygen from the NaOH step and attaches the middle carbon of the CS2 there. This is intended to allow the cellulose chains to separate from each other and dissolve in the next step. This is used as a gas, and there are gas emissions from rayon plants as they can't capture and recycle all of it. They've dramatically reduced the emissions as technology improves (and environmental permits get tighter) but there are still emissions. Most of the health effects listed in the document linked above seem to be related to the central nervous system with some cardiovascular effects as well. Along with the carbon disulphide gas is carbonyl sulphide, OCS, which forms when CS2 reacts with oxygen, and hydrogen sulphide, H2S, which forms when OCS reacts with water. H2S has a nasty rotton-egg smell which humans are extremely sensitive to, way below any toxic effects start. Unfortunately it also deadens your sense of smell, so by the time it does get up to toxic levels, you can't smell it anymore. All three gases are toxic to varying degrees. Due to permits and monitoring requirements, emissions are generally below their respective exposure limits unless something bad is happening.
- NaOH again
- This time, the NaOH solution is used to fully dissolve the cellulose with the CS2 attached, which it couldn't do before. Once the cellulose is dissolved, the solution is what's called viscose.
- This isn't a chemical that's added, but instead a process that removes any gases remaining in the solution. These gases could be air or CS2 and its side products. The gas stream would have to be treated before release, so this is possibly the source of the CS2 emissions mentioned above.
- Spin bath solution: H2SO4 (sulphuric acid, hydrogen sulphate, oil of vitriol), Na2SO4 (sodium sulphate), and Zn2+ (zinc) ions
- The viscose is squirted into this solution through small holes to make fine strands; this solution sets those strands into fixed form by knocking the CS2 back off the cellulose chains so they stick to each other and stop being soluble again. Sulphuric acid and sodium sulphate are a matched pair, and the latter buffers the acid to help maintain a constant pH while the reactions are happening. The acid pushes the actual reaction, and the zinc helps pull the chains together so they can bond into a thread as they fall out of solution. Sulphuric acid is dangerous by being corrosive more than toxic. Sodium sulphate is non-toxic. Zinc is necessary for life but is also toxic outside a narrow range of concentrations. The zinc is recycled by capturing it from the wash water and returning it to the process. Sulphuric acid is non-toxic once neutralized. With zinc recycling, there's a chance of small zinc emissions from this stage, as well as the freed CS2 and its side products mentioned above.
In terms of power, the initial purification down to cellulose takes heat, but if the facility is set up anything like a kraft paper mill, that heat comes from recycled internal power sources. The rayon process itself is done at room temperature, so no heating is required (other than heating the building, which is also done for the safety and comfort of the operators) here. Mixers and pumps would make up the rest of the power use. It doesn't sound like an energy hog, but without a P&ID I couldn't say for sure.
Rayon is a processed fiber with a natural source. With all that processing, the only relevance its original plant form has is in whether or not the feedstock itself is sustainably grown. Bamboo is, in this case, one of the most eco-friendly feedstocks to rayon-making. It does use toxic and dangerous chemicals in its process, all of which are washed out of the final product, leaving nothing but the original feed chemical, cellulose, reformed into a finer, smoother fiber. Well-run rayon plants will have minimal emissions and will recycle as much of those chemicals as they can, and some of them lend themselves well to internal recycling.
The eco mitt package label does say that it's made from bamboo rayon, which is correct, but above that, it says it's made from natural bamboo fibers. Unless it is a blend of natural bamboo fiber and bamboo rayon, this is not correct; once the bamboo is processed into rayon, it's no longer natural bamboo fiber. Likewise, the product page makes the claim that bamboo fiber has antibacterial properties—which is true, but those wouldn't survive the processing to make rayon. Again, IF the product is a blend of both natural and rayon bamboo, then this would be true. Natural bamboo fiber is much coarser than rayon, however; rayon is a product of the search for artificial silk (and it does feel nice and silky to the touch).
Regarding the non-recyclable vinyl package, it turns out that vinyl can be recycled but it may not be something you can put in your blue bin—meaning vinyl in consumer packaging isn't likely to be recycled. Unfortunately, this isn't all that much different from it not being recyclable at all, when it comes to consumer product packaging.
While researching the rayon process, however, I ran across a complaint by the US Federal Trade Commission about false claims made by various companies that bamboo rayon is "natural bamboo fiber" and that it has the antibacterial properties of natural bamboo fiber—exactly the claims made for the Eco Collection bath mitt here in Canada.
My bottom line: bamboo rayon is soft, silky, absorbant, and feels nice, but it's not the eco-friendly product it is frequently claimed to be, although it is the most eco-friendly of the rayon fabrics due to the cellulose source. Since this product is made from bamboo rayon but despite that also claims natural bamboo fiber and the associated antibacterial properties, I'd say it's a case of greenwashing. If Upper Canada Soap offers evidence that it's made from both natural bamboo and bamboo rayon, then I will retract my comments about the antibacterial claims.
I have to admit that after the previous items on the Marketplace greenwashing list and with their so-called "expert" comment (complete with wrinkled nose and disgusted tone of voice) about "funky chemical processing" I went in to this one expecting it to be as ridiculous as some of the other "lousy labels" they assigned that I've covered so far. Their expert seems to really have something against chemicals, despite the fact that all matter is made from chemicals. Maybe as the countdown approaches #1 they will be more consistently correct about claiming something is greenwashing.
10: Raid EarthBlends Multi-bug killer
9: Sunlight Green Clean Laundry Detergent
8: Obusforme EcoLogic Contoured pillow
7: Simple Green All-Purpose Cleaner
6: Eco Collection bath mitt
5: Vim PowerPro Naturals
4: Organic Melt Ice Remover
3: T-fal Natura frying pan
2: Biodegradable J Cloth
1: Dawn Antibacterial Hand Soap