We at rezemo use the bioplastic PLA proportionally as raw material for our sustainable coffee capsule made of wood. Bioplastics, colloquially also called bioplastics, are on everyone's lips. They promise independence from fossil resources and are supposed to stop the increasing littering of our oceans. But what is actually hidden behind the term "bioplastics" and what can these miracle materials achieve?
When is a plastic called "organic"?
The definition of bioplastics is not as clear-cut as one might think. A bioplastic consists either of renewable raw materials, is biodegradable or both. Conversely, this means that a plastic made from petroleum can also be called a bioplastic if it is degradable. In contrast, a biobased plastic is not necessarily biodegradable.
Fig. 1: Classification of bioplastics (own presentation)
However, biodegradable does not mean that the bioplastic bag can be disposed of in the domestic compost. In order to obtain an appropriate seal such as "ok biocompostable", the plastic must decompose under defined conditions in industrial composting plants. At approx. 60°C, the temperatures here are significantly higher than on the compost in your own garden. Furthermore, bioplastics do not normally contribute to the formation of humus, as classical compost materials do. Biodegradable only means that decomposition takes place down to the basic molecules CO2 and H2O.
Do bioplastics decompose into microplastics?
When hearing the word decomposition, many people have to think directly of the term "microplastic". So does the biodegradable plastic decompose to. Microplastics? Because that would not be a desirable decomposition product at all. Fortunately, the answer is: this is not the case.
Microplastics are defined as solid, insoluble, particulate and non-biodegradable synthetic polymers smaller than 5 millimetres[1]. They are formed by the physical decomposition of larger pieces of plastic. Due to the influence of wind, sunlight and mechanical forces, the plastic is ground into smaller and smaller particles. However, the molecular structure remains unchanged. Biological degradation, on the other hand, corresponds to chemical decomposition. Molecular bonds are destroyed here, so that harmless degradation products such asCO2 and H2O are produced in the end.
Fig. 2: Variants of plastic degradation (own presentation)
Advantages of bioplastics
A major advantage of biodegradable plastics is therefore that they do not Microplastics decompose, or that the microplastic particles that are initially created are broken down into harmless molecules in the further course of the process. Unfortunately, this process takes a very long time, especially in nature, so that biodegradable plastics cannot really offer a solution to the problem of waste. However, for suitable applications (as organic compost bags or for repackaging fruit and vegetables) they can be a great alternative. However, to really reap the benefits, composting facilities must then be enabled to break down these bioplastics. Currently, not all composting facilities are able to provide the necessary conditions in terms of temperature and retention time. Therefore, a large proportion of biodegradable plastics are sorted out and subsequently incinerated. In addition, it should at best be possible to distinguish the bioplastics visually from the conventional alternatives, as otherwise they may be inadvertently sorted out in the composting plant.
Which raw materials are used to produce bioplastics?
Biobased plastics are mainly produced from renewable raw materials raw materials. Bioplastics are often based on starch (polylactic acid PLA, thermoplastic starch TPS) or cellulose (cellulose regenerates such as viscose, cellulose hydrates such as cellophane). Corresponding raw materials are either starchy (corn, wheat) or rich in cellulose (wood). If you want to know more about renewable raw materials and their advantages, you will find a special Contribution on our blog.
Another option currently being researched is the use of microorganisms for the production of bioplastics. For example, specific microbes can produce the biopolymer polyhydroxybutyrate (PHB) from substances in wastewater. This biopolymer is similar in its properties to the widely used polypropylene (PP). These concepts are currently still in their infancy, but offer huge potential for future generations of bioplastics.
Fig. 3: Worldwide production capacity of bioplastics (https://www.european-bioplastics.org/market/)
Conclusion
Bioplastics do not offer the solution to all the problems that conventional plastics present us with. Nevertheless, there is immense potential in particular in the use of renewable raw materials immense potential. Currently, bioplastics cannot yet compete with conventional plastics in terms of cost. Through increased research and the growing demand for "green" alternatives, this price difference will become smaller in the future. Little by little, we will see more and more bioplastics on our supermarket shelves.
At rezemo we use the bioplastic PLA together with wood chips for our sustainable wooden capsules and are thus a pioneer in the use and processing of bio-based materials.
[1] https://www.bund.net/themen/meere/mikroplastik/hintergrund/