Standards for biodegradation tests-hydrobiodegradable and inherently biodegradable polymers

   There is not a standard test of biodegradability of universal validity. For the hydrobiodegradable and inherently biodegradable polymers, it is common the use of patterns for testing compostability. Some standards for compostability are: EN 13432, ASTM D6400, ASTM D5338, ISO 14855 and 17088, and Australian Standard 4736. These are standards for biodegradation in the special conditions found in industrial composting, that require short timescales and rapid CO₂ emissions. There are also standards for biodegradation in soils and aquatic environments but they are less used.

   Finally, the third group of biodegradable polymers consists of oxo-biodegradable materials, that is, those that need to undergo the chemical process of oxidation (combination with oxygen, which leads to breakage of the molecules) before they become biodegradable. In general, all the traditional widely used plastic materials are oxo-biodegradable, that is, over time undergo oxidative degradation, what leads to the breakdown of their molecules into smaller fragments, highly oxygenated, capable of being biodegraded. However the time scale to complete degradation and biodegradation is too long: it takes several decades. To accelerate this process, organic salts (such as stearates) of transition metals (such as iron, manganese and cobalt) are added, so reducing the time required for degradation and biodegradation to some years. Such additives are known as pro-oxidants or prodegrading.

   Until now, these salts have shown no toxicity to animals, plants or microorganisms, being rather micronutrients to them. To this group belong lignin, lignocellulose, natural rubber and polybutadiene (without the need of pro-oxidant additives) as well as traditional plastics, such as polyethylene, polypropylene, polystyrene and PET, all these formulated with pro-oxidant additives.