BIODEGRADABLE PLASTICS

BIODEGRADABLE PLASTICS

Biodegradable plastics are plastics that are capable of being decomposed by bacteria or other living organisms.

Two basic classes of biodegradable plastics exist: , Bioplastics whose components are derived from renewable raw materials and plastics made from petrochemicals with biodegradable e additives which enhance biodegradation.

The classes of biodegradable plastics considered, in terms of the degradation mechanism, are:

1) Biodegradable

2) Compostable

3) Hydro-biodegradable

4) Photo-biodegradable

5) Bioerodable

BIODEGRADABLE

Biodegredation is degradation caused by biological activity, particularly by enzyme action leading to significant changes in the materials chemical structure. In essence, biodegradable plastics should break down cleanly, in a defined time period, to simple molecules found in the environment such as carbon dioxide and water.

COMPOSTABLE

Compostable plastics are a subset of biodegradable plastics.

Compostable biodegradable plastics must be demonstrated to biodegrade and disintegrate in a compost system during the composting process (typically around 12 weeks at temperatures over 50°C). The compost must meet quality criteria such as heavy metal content, ecotoxicity, and no obvious distinguishable residues caused by the breakdown of the polymers.

HYDRO-BIODEGRADABLE AND PHOTO-BIODEGRADABLE

Hydro-biodegradable and photo-biodegradabe polymers are broken down in a two-step process - an initial hydrolysis or photo-degradation stage, followed by further biodegradation. Single degradation phase ‘water-soluble’ and ‘photodegradable’ polymers also exist.

BIOERODABLE

Many polymers that are claimed to be ‘biodegradable’ are in fact ‘bioerodable’ and degrade without the action of micro-organisms – at least initially. This is also known as abiotic disintegration, and may include processes such as dissolution in water, ‘oxidative embrittlement’ (heat ageing) or ‘photolytic embrittlement’ (UV ageing).