Bioplastics and other new materials offering environmental advantages have created a bit of confusion with the terms related with their source and end of life. I would like to shed some light in some of vocabulary used, starting with perhaps the less defined and yet more important word:
Bioplastic: Plastic obtained from natural and renewable sources
Most bioplastics are biodegradable and compostable, but they do not need to be in order to be classified as bioplastics. Similarly, not all bioplastics are sustainable. In Brazil, for example, there has been a lot of interest in obtaining traditional plastics from soy and other fast growing crops. Even though it sounds great, there are concerns about the impact these crops may have on the rain forest surface.
To better understand the differences between new bioplastics, it is important to have some concepts clear. I have divided the vocabulary in two main aspects: sourcing of the raw materials and degradation process of the bioplastic.
Degradation vocabulary
Biodegradable: Material that breaks down under the action of micro organisms to yield carbon dioxide, water and biomass. It is used quite widely, as most materials are biodegradable if given enough time and appropriate conditions. The fast biodegradability of organic waste is used to dispose of it, both in composting or dumping installations. However, the degradation process for each method is different:
- anaerobic degradation: It occurs in the absence of oxygen in dumping sites. It yields lignin, cellulose fibres and methane. The latter is more harmful to the ozone layer than carbon dioxide. With the right installations, methane can be collected and used to produce clean energy. Sadly, collection of methane is still limited in dumping sites through Europe.
- aerobic degradation: It occurs in the presence of oxygen and it yields carbon dioxide and compost. As small organisms start to break down the material, they ease further degradation, which is exothermic. The high temperatures generated speed up the composting process. Home composting is one of the most environmentally sound methods of disposing of your garbage, as rubbish is not transported around. There are very few industrial composting facilities in Europe.
Compostable: Specific form of biodegradable material, that breaks down within a certain period of time under composting conditions. Since this is a bit vague, there are several standard methods to certify the compostability of a material. European Bioplastics asks members to certify their products following these standard norms. An industrial agreement was signed by European Bioplastics to promote certification.
- EN 13432: Requirements for packaging recoverable through composting and biodegradation – Test scheme and evaluation criteria for the final acceptance of packaging
- EN 14995: Plastics – Evaluation of compostability – Test scheme and specifications
Hydrosoluble: Material capable of dissolving in water. This is not very common in the case of plastics, which leads to littering of rivers and coastal areas, a few examples if you follow this link. Hydrosoluble plastics are rare and costly. An example is the blend of PVA/PVOH produced and commercialised by Spanish company Plasticos Hidrosolubles, of which I’ll soon write .
Oxodegradable/photodegradable: Some materials will just oxidise in contact with air or when exposed to sunlight. Most plastics are fairly resistant to both processes in the short term. There are, however, additives designed to accelerate them, usually metallic ions. Plastic additivise in this manner fragments itself rather than degrading. The small size particles obtained can easily pollute soil and water. The so-called oxodegradable plastics are not compostable.
Sourcing vocabulary
Up to now oil has been the traditional source of raw materials for plastics. This is quickly changing not only for plastics, as the chemical industry shows great interest in the biorefinery business model. The vocabulary concerning the origin of bioplastics has not been formally defined, as is the case for degradation, and can be confusing, even misleading. To guide you through, a few more definitions:
Renewable: Natural resource, either material or energy, that can be replaced at the same pace it is consumed. The main resources used to manufactured bioplastics are renewable, like corn, potato, sugar cane, etc.
Partially renewable: This is not really a definable concept, but more a tag given to those materials that are partially sourced from renewable resources. Starch-based materials, like Mater-bi from Novamont, are actually a blend of synthetic polyesters and starch based material. Of course, the final aim of serious bioplastic producers is to reduce the synthetic percentage to nothing.
Sustainable: Actions and products that cover our current necessities without endangering future generations. Sustainable is, like bioplastic, a not very well defined term in the industry and can be applied to almost any product. A product or material can be labelled sustainable because it reduces carbon dioxide emissions, because it comes from renewable sources or because it reduces waste.
A warning word
The lack of harmonised definitions for some of these concepts can lead to misunderstandings, but also to abuse. Almost any product can be tagged sustainable, even the ones that are not environmentally sound. Industry should adopt normalised standards with regards to minimum renewable content of bioplastics, for example. There are already movements within bioplastic producers towards standardisation with regards to compostability, so why not about the true essence of a bioplastic?
Other sources of information
ERRMA (European Renewable Raw Materials Association)
