Biodegradable plastic

Many plastic manufacturers throughout Canada and the US have released products indicated as being compostable. However this claim is debatable, if the manufacturer was minimally conforming to the now-withdrawn American Society for Testing and Materials standard definition of the word, as it applies to plastics: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) ^[4]

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.