Composting
The process of biodegradation under aerobic conditions within a time frame of 6-12 weeks is called composting. Composting of industrial products usually takes place in industrial composting plants, where controlled conditions (e.g. temperature, humidity, aeration) are given.
Bioplastic products correctly certified as compostable (e.g. according to EN 13432) can be diverted to the composting waste stream at the end of their life. Microbes, like bacteria or fungi with their enzymes, are able to “digest” the chain structure of compostable polymers as a source of nutrition. The resulting end products are water, carbon dioxide CO2 and a little biomass.
It is the chemical structure of a polymer, especially the type of chemical bond, that defines whether and to what extent microbes can biodegrade the material in a given time. This is the reason why certain synthetic polymers can also be composted – but most others (like PE, PP, PS, PET) cannot.
Composting pre-requirements and infrastructure
The speed of biodegradation depends on: temperature – 50-70°C are typical for a industrial composting process; humidity – water is required for the process; and the number and types of microbes.
Only if all three pre-requirements are given the speed of degradation is fast. If one element is missing, degradation is almost blocked. In an industrial composting facility, of which many exist in several EU countries and regions, certified bioplastic products are converted into CO2, water and biomass within 6 to 12 weeks. In the food supply chain, in supermarkets or at home, biodegradation occurs at a very low speed in comparison to composting. Organic household waste is collected by source separation from residual waste, such as in bio-bins, and treated in composting plants to produce quality compost.
Compostable bioplastic products can make use of the existing composting infrastructure and thus be recycled organically. However, compliance with the composting system has to be proven by fulfilling the standardised test criteria of EN 13432. For the approval and labelling of bioplastics products based on EN 13432, the industry and other involved parties have developed a certification scheme.
Biodegradation is not “oxo-fragmentation”
Careful distinction is needed between biodegradable plastics and plastic that are advertised as being “oxo-degradable” or “oxo-biodegradable”. The latter products are made of traditional plastics supplemented with specific additives.
The terms „oxo-degradable“ or ‘oxo-biodegradable’ suggest that the products can undergo biodegradation. However, the main effect of oxidation is fragmentation of the material or product into small particles which remain in the environment. Therefore, the term ‘oxo-fragmentation’ better describes the typical degradation process that these products can undergo under specific environmental conditions.
In terms of degradability, European Bioplastics does solely represent companies that produce truly biodegradable materials and products according to acknowledged standards. For more information see our corresponding publications or go to the chapter Oxo-biodegradability.
Form more information on the difference between biodegradable and oxo-fragmentable materials see European Bioplastics’ position paper.
