What are bioplastics?
Material types, terminology and labels – an introduction
Bioplastics – a family of materials
Bioplastics are not just one single substance, they comprise of a whole family of materials with differing properties and applications. According to European Bioplastics a plastic material
is defined as a bioplastic if it is either biobased, biodegradable, or features both properties.
-Biobased: The term “biobased” means that the material or product is (partly) derived from biomass (plants). Biomass used for bioplastics stems from e.g. corn, sugarcane, or cellulose.
-Biodegradable: Biodegradation is a chemical process during which micro-organisms that are available in the environment convert materials into natural substances such as water, carbon dioxide, and compost (artificial additives are not needed). The process of biodegradation depends on the surrounding environmental conditions (e.g. location or temperature), on the material and on the application.
The property of biodegradation does not depend on the resource basis of a material, but is rather linked to its chemical structure. In other words, 100 percent biobased plastics may be non-biodegradable, and 100 percent fossil based plastics can biodegrade.
In short, contrary to conventional fossil-based plastics, bioplastics are (partly) biobased, biodegradable, or both.
Material types – three main groups
The family of bioplastics is roughly divided into three main groups:
- Biobased or partly biobased non-biodegradable plastics such as biobased PE, PP, or PET (so-called drop-ins) and biobased technical performance polymers such as PTT or TPC-ET
- Plastics that are both biobased and biodegradable, such as PLA and PHA or PBS
- Plastics that are based on fossil resources and are biodegradable, such as PBAT.
The graph “material coordinate system of bioplastics” depicts typical bioplastics and how they are classified according to their biodegradability and biobased content.
Established examples of bioplastic materials
Biobased, non-biodegradable polyolefines and PET (“drop-in” solutions)
Commodity plastics like PE, PP and PVC can also be made from renewable resources – often from bioethanol. Bio-PE is already produced on a large scale (200,000 tonnes p.a. by Braskem, Brazil; further projects planned by Dow Chemicals). Bio-PP and Bio-PVC are soon to follow. The partially biobased polyester PET is used both for technical applications and for packaging (mainly for beverage bottles, e.g. by Coca-Cola). As the value-added chain only requires adaptation at the outset, and the properties of the products are identical to their fossil versions, they are also referred to as ‘drop-in’ bioplastics. The period from development to commercialisation has thus been considerably shortened.
Biobased, non-biodegradable technical/performance polymers
This large group contains many specific polymers such as biobased polyamides (PA), polyesters (e.g. PTT, PBT), poly¬urethanes (PUR) and polyepoxides. Their use is most diverse. Some typical technical applications are textile fibres seat covers, carpets), automotive applications like foams for seating, casings, cables, hoses, and covers – to name but a few. Usually, their operating life lasts several years. Therefore, they are referred to as durables, and biodegradability is not sought-after.
Biobased, biodegradable plastics
They include starch blends made of thermo-plastically modified starch and other biodegradable polymers as well as polyesters such as polylactic acid (PLA) or polyhydroxyalkanoate (PHA). Unlike cellulose materials (regenerate-cellulose or cellulose-acetate), they have been available on an industrial scale only for the past few years. So far, they have primarily been used for short-lived products such as packaging, yet this large innovative area of the plastics industry continues to grow by the introduction of new biobased monomers such as succinic acid, butanediol, propane diol or fatty acid derivatives.
Several materials in this group, such as PLA, are currently pointing towards new ways – away from biodegradation and towards end-of-life solutions such as recycling. The renewable basis of these materials is now at the focus of attention and technical development. Pilot projects aim to establish recycling processes and streams. This dynamic development proves, that bioplastics have the potential to shape the plastics industry, and to produce new future-bound and competitive materials.
Biodegradable, fossil-based plastics
They are a comparatively small group and are mainly used in combination with starch or other bioplastics because they improve the application-specific performance of the latter by their biodegradability and mechanical properties. These biodegradable plastics are currently still made in petrochemical production processes. However, partially biobased versions of these materials will surely be produced in the near future.
Standards, certification and labels
How can one measure the biobased part of bioplastics? Which standard, methodology, terms and labels should be applied? There is still a lot of confusion in the international market, because around the globe standardisation processes have proceeded at a differing pace.
Below, the status quo in Europe will be outlined, and relevant independent third party labels for bioplastics are listed. However, the list does not reflect any specific recommendation of European Bioplastics.
Companies with biobased bioplastics can either indicate the “biobased carbon content” or the “biobased mass content” of their products. As these units of measurement differ, the typical numeric percentage value will differ, too, and must be taken into account, especially when drawing comparisons.
A well-established methodology to measure the biobased carbon content in materials or products is the 14C-method (EU standard: CEN/TS 16137, corresponding US-standard: ASTM 6866). Certification schemes and derived product labels based on the European and the U.S. standard are in place – for example by the Belgian certifier Vinçotte or the German DIN CERTCO.
A material or product can also be specified as biobased by indicating its biobased mass content. This method is complementary to the 14C-method, and takes chemical elements other than the biobased carbon into account, such as oxygen, nitrogen, and hydrogen. The French Association Chimie du Végétal (ACDV) has introduced a corresponding certification scheme and the European Committee for Standardization (CEN) is currently developping a standard.
It is misleading to merely claim biodegradability without any standard specification. If a material or product is advertised to be biodegradable, further information about the timeframe, the level of biodegradation, and the surrounding conditions should be added.
Wherever possible, European Bioplastics recommends to focus on the more specific claim of compostability, and to back it up with corresponding standard references (ISO 17088, EN 13432 / 14995 or ASTM 6400 or 6868), a certification and labelling (seedling label via Vinçotte or DIN CERTCO, OK compost label via Vinçotte).
If a product is specified to be compostable, the claim is not only unambiguous, but there is another big benefit: It differentiates itself from products marketed to be “oxo-biodegradable” or similar claims. Products marketed as oxobiodegradable do not fulfil the requirements of EN 13432 on industrial compostability, and are therefore not allowed to carry the seedling label.
Bron: european-bioplastics.org / Berlin / Jan. 2015