Recently i learned the difference between biodegradable and compostable. When something is biodegradable, it means it is degradable, but it also means that it can be broken down by the metabolism by micro-organisms. When something is compostable, it means that it biodegrades, but it also means something more: that it will degrade within a certain amount of time, under certain conditions and leave no toxic residue (source Treading My Own Path). Currently the term ‘compostable’ is legally definied but biodegradable is not, meaning that any product can be listed as being biodegradable without having been tested as so.
We all know that natural fibres such as wool, linen, hemp and cotton are both biodegradable and compostable but I’m reading conflicting reports on whether synthetic fabric made from plant fibres such are either biodegradable or compostable.
Ed Mass from Yes it’s Organic says that Rayon, Viscose, Modal and Tencel are biodegradable but worrying Wikipedia states that many kinds of marine creatures eat rayon fibres and that they end up in their bloodstream which can be fatal for them, and a recent ocean survey found that rayon contributed to 56.9% of the total fibres found in deep ocean areas. Information that I received from the company Lenzig indicate that their fabrics Tencel and Model will disintegrated by up to 90% after 6 months, that no more than 10% of the remaining material will be bigger than 2mm and that residual heavy metals and fluorine are below permitted levels. It’s up to you to decide if this level of disintegration and contamination is acceptable to you.
Lenzig’s products have been tested for compostability but we can’t assume this level of disintegration for all forms of rayon or viscose because every manufacturer has their own process for making it. In his post Rayon Recycling, Fred Decker of Demand Media says rayon is compostable and he quotes the a research paper from the Journal of Applied Polymer Science as proof but I don’t have full access to this database so can’t verify it and the abstract seems to suggest that it’s not a cut and dried issue and is heavily dependant on conditions.