Biodegradable plastic

Biodegradable plastics are plastics that are decomposed by the action of living organisms, usually bacteria.

Two basic classes of biodegradable plastics exist:Bioplastics, whose components are derived from renewable raw materials, and plastics made from petrochemicals containing biodegradable additives which enhance biodegradation.

Many people confuse "biodegradable" with "compostable". "Biodegradable" broadly means that an object can be biologically broken down, while "compostable" typically specifies that such a process will result in compost, or humus. Many plastic manufacturers throughout Canada and the US have released products indicated as being compostable. The waste management infrastructure currently recycles regular plastic waste, incinerates it, or places it in a landfill. Mixing biodegradable plastics into the regular waste infrastructure poses some dangers to the environment. However this claim is debatable, if the manufacturer was minimally conforming to the now-withdrawn American Society for Testing and Materials standard definition of the word, as it applies to plastics:

"that which is capable of undergoing biological decomposition in a compost site such that the material is not visually distinguishable and breaks down into carbon dioxide, water, inorganic compounds and biomass at a rate consistent with known compostable materials." (ASTM D 6002)

There is a major discrepancy between this definition and what one would expect from a backyard composting operation. With the inclusion of "inorganic compounds", the above definition allows that the end product might not be humus, an organic substance. The only criterion the ASTM standard definition did outline is that a compostable plastic has to become "not visually distinguishable" at the same rate as something that has already been established as being compostable under the traditional definition.

In January 2011, the ASTM withdrew standard ASTM D 6002, which many plastic manufacturers had been referencing to attain credibility in labelling their products as compostable. The withdrawn description was as follows:

"This guide covered suggested criteria, procedures, and a general approach to establish the compostability of environmentally degradable plastics."

As of 2014^[update], the ASTM has yet to replace this standard.

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