For more than 20 years, biodegradable plastics have been a part of our everyday life. Bags, packaging, daily products, they represent a market of approximately 1 million tons at global level. Nonetheless, the notion of biodegradation which describes their end-of-life properties is often confused or misused.
HOW TO WELL DEFINE THIS TERM?
Biodegradability is a property related to the material chemical structure and is independent of the polymer origin. So, it is important to make the difference between the notions of biobased (use of biomass for polymer production) and biodegradable. Indeed, a petroleum-based polymer can be biodegradable (ex: PCL) or on the contrary, a polymer can be biobased but not biodegradable (ex: bio-based PE).
Biodegradation is the decomposition (fragmentation and assimilation) of a material under the action of micro-organisms (ex: bacteria, fungi). It results in the formation of water, carbon dioxide, methane and biomass which do not represent any kind of hazard for the environment. This decomposition can be anaerobic (without oxygen) or aerobic (with oxygen).
When mentioning the end of life of bioplastics, terms of composting and compostability are often used. They referred to the realisation of the biodegradation action in specific conditions and in an aerobic environment. A distinction should be made between home composting and industrial composting:
- Industrial composting is carried out on dedicated platforms where temperature and humidity conditions among other, are rigorously controlled.
- Home composting is carried out in less or not controlled conditions, for example at a private home.
The material capability to be used in these two frameworks depends today, on the respect of these two main standards:
- Standard EN 13432: 2000 which deals with packaging recovery through industrial composting and biodegradation.
- Standard NF T 51-800: 2015 which deals with specifications for plastics qualified for home composting.
Today, this last one is used as a reference for the different regulations put in place notably in France (cf. article single-use plastics), regarding the usage of plastic materials for disposable applications.
Nonetheless, the standard NF EN 13432 often remains as the reference in the matter of biodegradability. Biodegradable plastics have to fulfil several criteria in order to meet the standard:
- Composition (according to EN 13432): the standard establishes a minimum solid volatile rate (50%), as well as a maximum content in heavy metals and fluorine acceptable in the initial material.
- Disintegration (according to ISO 16929): it is the ability of the product to fragment itself under the effect of composting. The refusal threshold is 10% of the initial weight above a 2mm sieve after 12 weeks of trial.
- Biodegradability (according to ISO 14855:1999): the acceptable biodegradability threshold is at least 90% total, or 90% of the maximum disintegration of a reference substance in less than 6 months.
- Final compost quality and ecotoxicity (according to OCDE 208): it must not be modified by the packaging materials added to the compost and must not be a hazard for the environment. The standard imposes to make ecotoxicological tests on the final compost and requires a performance of at least 90% of the corresponding reference compost.
SEVERAL DIFFERENT END-OF-LIFE ENVIRONMENTS FOR BIODEGRADABLE PLASTICS
In order to represent the largest variety of end-of-life environment, the criteria of disintegration and biodegradability of the EN 13432 standard have also been adapted.
Thus, each different biodegradation environment possible for biodegradable plastics, has their own requirements even though the composition and ecotoxicity criteria remain the same as described in EN 13432 standard:
|Biodegradation condition||Temperature||Biodegradation (more than 90 %)||Disintegration (less than 10% above 2 mm)|
|Industrial composting||50 – 70 °C||Less than 6 months||Less than 12 weeks|
|Home composting||20 – 30 °C||Less than 12 months||Less than 6 months|
|Soil biodegradation||20 – 25°C||Less than 24 months||No requirement|
|Water biodegradation||20 – 25°C||Less than 56 days||No requirement|
|Marine biodegradation||20 – 25 °C||Less than 6 months||Less than 84 days|
The fulfilment of these different criteria gives access to labels commercialized by certification organisms.
Biodegradable plastics have their own degradation kinetic depending on the considered biodegradation environment and thus variable shelf-life in use. The choice of the right material for the right application has to be done considering usage conditions and expected end-of-life.
About us: NaturePlast is a french company based in Normandy (IFS-14), specialized in bioplastics. With more than 10 years of experience in this field, the company has the most extensive portfolio of raw materials and biobased and/or biodegradable compounds in Europe. With its daughter company BiopolyNov, they provide support to industrialists from the origin to the industrialisation of their innovative project. Thanks to their R&D expertise acquired during the years, NaturePlast and BiopolyNov are renowned major player in the development and production of formulations for clients and collaborative projects.