Biodegradation is a chemical process in which materials are metabolised to CO2, water, and biomass with the help of microorganisms. The process of biodegradation depends on the conditions (e.g. location, temperature, humidity, presence of microorganisms, etc.) of the specific environment (industrial composting plant, garden compost, soil, water, etc.) and on the material or application itself. Consequently, the process and its outcome can vary considerably.
In order to be recovered by means of organic recycling (composting) a material or product needs to be biodegradable. Compostability is a characteristic of a product, packaging or associated component that allows it to biodegrade under specific conditions (e.g. a certain temperature, timeframe, etc). These specific conditions are described in standards, such as the European standard on industrial composting EN 13432 (for packaging) or EN 14995 (for plastic materials in general). Materials and products complying with this standard can be certified and labelled accordingly.
Please note that in order to make accurate and specific claims about compostability the location (home, industrial) and timeframe need to be specified.