Compostable Plastics


Bioplastics came out a little over 15 years ago, creating and continuing to create quite a stir in the environmental community.

Background

Bioplastics include the categories of compostable, biodegradable and degradable plastics, though compostable plastics have been some of the more extensively studied and standardized of the bioplastics. The American Society for Testing & Materials International (ASTM) established standards for compostability (D6400-99) through extended studies and stated that compostable plastics must met at least three essential requirements:

  • They must biodegrade at a rate comparable to yard trimmings, food scraps and other compostable materials;
  • They must disintegrate, so that no large plastic fragments remain to be screened our and;
  • They must disintegrate and biodegrade safely so that the compost is able to support plant growth ("leaves no visible or detectable toxic residue").

Biodegradable and degradable plastics must be distinguished from compostable plastics, as they have different technical definitions and lack standardization testing.

Biodegradable Plastic degrades by naturally occurring microorganisms (bacteria, fungi etc.) over a period of time. There is no specification about leaving "toxic residue," and no requirement for the time span it needs to biodegrade.

Degradable Plastic will undergo a significant change at the chemical level under specific environmental conditions resulting in a loss of some properties. It should be noted that there is no requirement that the plastic has to degrade from the action of "naturally occurring microorganism" nor are there requirements for toxicity, time span, or complete disintegration.

It should be noted that there have been various studies conducted on both degradation and biodegradation in varying environments, such as soil and marine testing. However, standardization results have not yet been set, making it difficult to critique their viability as environmentally sound product ideas.

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