Two different product groups fall under the term “bioplastics”: “biobased” plastics and “compostable” plastics.
Bio-based plastics are partly or entirely made of renewable raw materials. Polylactic acid (PLA), polyhydroxyalkanoate (PHA), starches, cellulose, chitin and gelatin for example, belong to this group. Bio-based plastics can be biodegradable – but they are not always. Among the bio-based but not biodegradable plastics are biopolyethylene, natural fiber plastics and composites of wood and plastic.
Biodegradable and compostable plastics can be biodegraded by microorganisms. Special bacteria give off enzymes which break down the material’s flexible polymer chains into small parts. These are then digested by the bacteria together with other organic material such as organic waste. Water, carbon dioxide and biomass remain. Compostable polymers can, but need not be produced from renewable raw materials. They can also be based on crude oil. The biodegradability does not depend on the raw material, it depends entirely on the chemical structure of the polymer.
The term „biodegradable“ is often used without clearly stating its meaning. It is important to always mention the environmental conditions where the biodegradation happens and how it takes place. Biological degradation depends on natural microorganisms. That is why any statement on the biodegradability can only be given for the respective environmental surrounding, which can be e.g. an industrial composting facility, a home-compost heap or agricultural soil. General statements on the environmental degradability cannot be regarded as reliable. The proof of the complete biological degradability is verified by independent certificates based on approved standards.
In different countries, there are special certification methods which independent institutes use to test biopolymers according to their biological degradability, chemical safety and eco-toxicity. Only when a material meets the clearly defined test criteria in standardized test conditions may it be marked e.g. as compostable or biodegradable in the soil.
- EU: DIN EN 13432
- USA: ASTM 6400
- Japan: Green PLA
- Australia: AS 4736