Biodegradable plastics are plastics which can be converted into water, carbon dioxide (CO2) and bio-mass over time with the help of micro-organisms this process is called biodegradation. And because the biodegradability of a plastic lies with the chemical properties of the polymer and not the source of the feedstock biodegradable plastics can be either bio- or petroleum-based.
The length of the biodegradation process is highly dependent on environmental parameters such as humidity and temperature, which is why claiming that a plastic is 'biodegradable' without any further context (i.e., in what timeframe and under what environmental conditions) is misleading.
Compostable plastics are a subset of biodegradable plastics, defined by the standard conditions and timeframe under which they will biodegrade. All compostable plastics are biodegradable, but not all biodegradable plastics would be considered compostable. Compostable plastics are those plastics which have been tested and certified by a third party to adhere to international standards such as ASTM D6400 (in the U.S.) or EN 13432 (in Europe) for biodegradation in an industrial composting facility environment. Compostable plastics will disintegrate within 12 weeks and biodegrade at least 90% within 180 days in a municipal or industrial composting facility.
Approximately 10% of solid material will be left at the end of the six-month-long process in the form of valuable compost, or biomass and water. These standards also ensure that the leftover compost will be free of toxins, so the compost will not cause harm when the facility sells it for gardening or agricultural applications. Oxo-degradable plastics are not biodegradable plastic, but rather a conventional plastic mixed with an additive will quickly fragment into smaller and smaller pieces, called microplastics, but don’t break down at the molecular or polymer level like biodegradable and compostable plastics. The resulting microplastics are left in the environment until they eventually fully break down.ally fully break down.