Plastics are currently much discussed - not least because of the latest plans of the EU Parliament to ban certain disposable plastic products such as cotton swabs or disposable tableware. The discovery of microplastics in human feces samples also caused much attention.
Bioplastics are often associated with sustainable and environmentally friendly packaging. However, bioplastics are not just bioplastics. And do bioplastics have the potential to replace conventional plastics as sustainable alternatives? The Fraunhofer Project Group IWKS points out facts and takes a stand.
What is bioplastics?
Most of the plastics used today are made from fossil raw materials such as crude oil or natural gas (1). Although flexible and versatile, conventional plastics have the disadvantage of consuming non-renewable resources in production and not being (fully) biodegradable. Since plastic has become an essential material in our society, for example in medical technology, which has to meet high requirements, it cannot easily be replaced by other materials. One way of conserving fossil resources and reducing waste is to use plastics based on natural raw materials. These substances can, but do not have to, be biodegradable (2). There are also plastics that are biodegradable but made from petrochemical raw materials. In order to facilitate differentiation, one often speaks of biobased plastics, i.e. plastics produced from renewable raw materials, and/or biodegradable plastics, i.e. plastics that can be decomposed by microorganisms present in the environment.
Everything organic - so off to the organic waste bin?
So-called biodegradable plastics are now also available in retail outlets, for example as bags for organic waste. These are actually to be disposed of with organic waste in municipal composting plants. However, there are considerable differences between the individual bioplastics. Not all bio-based and biodegradable plastics decompose equally quickly. This depends not only on the material itself, but also on the environmental conditions (e.g. temperature and humidity). For this reason, some municipal waste disposal companies refuse to process bioplastic bags for composting because they do not decompose or do not decompose completely under the conditions prevailing there. This is often difficult for the consumer to see and understand. In the meantime, initial guidance has been provided in the form of standards (e.g. EN 13432) or certifications. These include, for example, the OK Compost Home logo, which identifies products that are completely degradable in domestic compost, as well as the seedling symbol of the European Bioplastics e. V.
Renewable raw material = good for the environment?
Bioplastics usually used today are made of biomass, which is obtained from maize, sugar cane or wood, e.g. for degradable plastic bags. In principle, this has the advantage that the environment is spared by renewable raw materials and therefore a better CO2 balance is achieved, since composting does not involve thermal utilisation. However, there are still some challenges:
- Bioplastics made from corn or sugar compete with food production. This is a serious phenomenon, especially in view of the rapidly growing world population and the sometimes precarious food situation. A look at Germany: In 2017, the area used for industrial and energy crops in Germany amounted to around 2.7 million hectares (3). By way of comparison, in 2017 only around 16.7 million hectares were used for agriculture in Germany (4).
- In the cultivation of renewable raw materials, monocultures are frequently used which result in a high consumption of soil and water, which in turn has to be included in the CO2 balance. Added to this is the energy consumption during production (5).
- The properties of biobased materials are often not yet equivalent to those of conventionally produced plastics (e.g. when used as packaging material for food) (6).
- The separation of bioplastics in automated sorting plants is still very inadequate, whereby these materials are lost to the material cycle through composting and are instead incinerated or disposed of in landfills.
Bioplastics, yes – but only if done properly!
The researchers of the Fraunhofer Project Group IWKS are of the opinion that bioplastics can make a considerable contribution to the relief of resources and the environment. However, there are some basic requirements to be met. The researchers therefore recommend:
- to use alternative bio-based raw materials that do not compete with food production. Only then can bioplastics be used sensibly and sustainably under ecological, economic and social factors (7).
- to support further research approaches such as the consistent use of residues from food production for applications on industrial scale (e.g. from raspberry or apple pomace) (8).
- to further improve the properties of bioplastics according to industry requirements without compromising sustainability (e.g. biobased and biodegradable coatings based on hemicellulose or biogenic adhesion promoters to improve the mechanical properties of sustainable composite materials) (9).
- to create more transparency for consumers through clear labelling on the products, on the one hand in order to open up the possibility of influencing purchasing behavior and on the other hand to guarantee correct disposal.
- biodegradable plastics should be labelled uniformly for automated sorting. Only then, from the point of view of the Fraunhofer Project Group IWKS, does it make sense to feed biodegradable plastics into the recycling cycle.
- active involvement of industry and recycling companies through incentives to develop prototypes and implement them at industrial scale (incentives instead of exclusively prohibitions, approach of Design for Circularity).
(2) Dorner, Michael: Biopolymere – Polymere aus der Natur. München: GRIN Verlag, 2001
(6) Hanstein, S.: Pflanzen für die Bioökonomie – Welche Herausforderungen ergeben sich für die Qualität nachwachsender Rohstoffe? und Faserreiche Nebenprodukte der Pflanzenextraktion als Rohstoffquelle für Verpackungen und verstärkte Kunststoff. 50. Vortragstagung der Deutschen Gesellschaft für Qualitätsforschung (Pflanzliche Nahrungsmittel) e.V. (DGQ, Julius Kühn-Institut, Berlin-Dahlem, 14.-15. März 2016
(7) Hanstein, S.: Regional Implications of the HyperBioCoat Value Chain. European Bioeconomy Congress, Lodz (PL), 07. Oktober 2016
(8) Hanstein, S: Biobasierte Beschichtungen. IWAR-Vortragsreihe "Neues aus der Umwelttechnik und Infrastrukturplanung", Technische Universität Darmstadt, 03. Juni 2017
Hanstein, S: Nachhaltige Verpackungen auf Basis von Kakaoschalen, Beeren- und Apfeltrester. Runder Tisch Kakao an der Bucerius Law School Hamburg, 23. Juni 2017
(9) Hanstein, S.: Exploitation of plant polymers as structural resources - activities of the Business Unit Food and Bio-Based Materials of the Fraunhofer Project Group IWKS Workshop ACTANAT: Wood-Fibre Reinforced PP – Technology and Application, Darmstadt, 08. Juni 2016
Hoffmann, J.: Biobasierte Verbundwerkstoffe – Nutzung von Polysacchariden zur Oberflächenmodifikation Nachwuchskongress Ressourceneffizienz, Pforzheim, 27. Februar 2018
Titze-Frech, K.: Biogene Haftvermittler in naturfaserverstärkten Kunststoffen. Kooperationsforum Biopolymere, Straubing, 24. Oktober 2018