 In other words, these plastics cannot be claimed as “biodegradable” (as defined by both American and European Standards) due to the fact that they cannot biodegrade naturally in the biosphere.An example of a non-biodegradable compostable plastic is polylactic acid (PLA).The ASTM standard definition outlines 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.