Subtle Differences Can Mean A Lot.

• Position: SCIENTIFIC DEFINITIONS - Biodegradable, compostable and degradable - Brief article

A paper bag not only is biodegradable, it is compostable; a biodegradable plastic bag is not necessarily compostable, but compostable material always is biodegradable.

Some definitions should not be confused, stresses the American Society for Testing and Materials, West Conshohocken, Pa. It is important to understand the meaning of "compostable" and "biodegradable" because they are not equivalent and should not be used interchangeably:

* Degradable. A material that undergoes significant changes in its chemical structure when subjected to various specific environmental conditions, resulting in a loss of properties that can be measured by standard methods in a given period of time.

* Biodegradable. A material that undergoes degradation resulting from the action of naturally occurring microorganisms, such as bacteria, fungi, and algae. There is no reference to the amount of time...