Biodegradable plastic is a material that gets dissociated biologically due to bacteria or microorganisms either underground or in air

The conventional plastic resin synthesized by petroleum chemistry cannot be dissociated by bacteria, and are considered to remain permanently as waste. However, due to the recent advances in chemical technology, plastic resin materials have been developed that are dissociated into water and carbon dioxide. Some of such materials have already been made into commercial products and are being used in various injection molded items.

After using the molded items produced from a biodegradable plastic resin, they are buried underground, or are mixed with kitchen garbage as compost and left to decompose. These are ideal materials for preserving the earth's environment and for preventing global warming.

In order to use biodegradable plastics resin in industrial products or as packaging materials, while it is necessary that they have a certain strength and heat resistance, and satisfy the standards related to food and hygiene, products satisfying these requirements are being successfully commercialized one after the other.

The tableware used in the restaurant in the Aichi World Expo held in March of 2005 were made of biodegradable plastics, and this fact was clearly stated in the administrative policy speech by the then Prime Minister Koizumi during the normal Diet session held in February 2005.

It is considered that the practical realization of biodegradable plastics resin will progress at a very fast pace in the fields of electrical home appliances, interior decoration parts of automobiles, tableware etc, and in various other fields in about three years from now.

Some of the major biodegradable plastic materials are described below.

■ Poly-lactic acid (PLA)

This is a plastic resin that is synthesized only from starch produced from corn or potatoes, and is a material whose commercialization has progressed most.
Grades have appeared that can improve the heat resistance and strength, and are being used practically in parts of electrical home appliances, computer products, returnable food containers (bowls, cups, etc. that can be used in dish washers).
In the case of heat resistant grades, although problems have been pointed out that it is necessary to maintain the mold temperature at 110 to 120°C, and that separating from the mold is very difficult, production methods have been developed to solve these problems.

■ Poly butylene succinate (PBS)

This is a biodegradable plastic resin made from soft biomass of which succinic acid is a typical constituent. While poly-lactic acid is suitable for high hardness molded items, PBS is suitable for soft molded items.

■ Poly vinyl alcohol (PVA)

■ Poly glycolic acid