Biodegradation is a natural process in which bacteria, fungi or other organisms alter the chemical and physical properties of substances and break them down into simpler substances such as water, carbon dioxide and ammonia.
Nearly all chemical compounds and other materials are subject to biodegradation. However, the speed of biodegradation varies dramatically, ranging from weeks to centuries or even millennia, according to the type of substance as well as to the temperature, humidity, availability of oxygen and exposure to light. Organic materials generally have a much higher speed of biodegradation and leave much less residue than petrochemicals and other synthetic materials.
A reasonable use of the term 'biodegradable' on products and substances is that they will degrade into carbon dioxide, water, biomass and perhaps also mineral salts when exposed to the appropriate air, moisture and microbial conditions within a matter of months and that the resulting materials will be nontoxic.