Definition and evaluation criteria
The European Environment Agency (EEA) defines biodegradability as "the extent to which a substance can be decomposed by bacteria and fungi, leaving degradation residues that are not toxic".
The same source reminds us that biodegradable is an often misunderstood term. In everyday language, for example, it is often associated with the idea of being harmless. It is a wrong association. During biodegradation, some harmful compounds can take much longer to degrade than others, damaging the environment.
Furthermore, biodegradation can be partial and incomplete, leaving residues in the environment that can even be more harmful than the original material. The accumulation in the environment of non-biodegradable (or poorly biodegradable) substances, such as some biocides contained in the material that biodegrades, can have very adverse effects on the environment.
Finally, it should be emphasized that the main environmental advantage of the biodegradability of a product is the improvement of the quality of controlled waste collection, especially wet waste. Associating biodegradability with reducing the impact of the uncontrolled release of material into the environment can instead be counterproductive and increase uncontrolled landfill. The perception of the lower environmental impact of the gesture of abandoning a waste in the environment - because it is biodegradable - could reduce attention and the commitment not to do so.
In the European Union, – the standard, EN 13432: of 2002 establishes the characteristics for a product to be defined as biodegradable or compostable - the two definitions are not equivalent and must not be confused. The European standard's field of application is packaging and packaging materials, but we can extend it, by analogy, to all products. In the USA, the ASTM standards (American Society for Testing and Materials), the most important being the ASTM 6400, follow the European ones with slightly less stringent requirements on degradation times.
According to EN 13432 to define a biodegradable product, the degradation must concern at least 90% of the basic components of the material within 6 months in the presence of an environment rich in carbon dioxide (the so-called biodegradation in an aerobic environment, the evaluation is more complicated if the biodegradation takes place in controlled industrial plants for the production of biogas). For the definition of computability, the time required is even shorter (3 months). If the product comprises several parts, such as a garment of which different materials may be part, the requirement applies to all the individual parts.
In any case, the process must not release or have as a residue any toxic or dangerous substance; precise specifications are required, such as heavy metal release risk.
In Europe, certifications regarding compliance with European standards EN 13432 and American ASTM 6400 are provided by TÜV Austria (OK biodegradable and OK compostable label) and by the German DIN CERTCO.