Why biodegradable does not mean it is compostable and compostable does not mean it is sustainable
A big mistake: Bioplastic also means biodegradable and biodegradable means compostable. And if something is compostable, it can go in the organic waste garbage can or in the compost.
Plastic bags for the organic waste garbage can, flower pots made of compostable plastic and biodegradable plastic packaging are marketed as environmentally friendly and sustainable – but they should be questioned critically!
Not all plastic is the same
Conventional plastic is made from fossil raw materials such as petroleum and, as everyone now knows, represents a major environmental burden. Bio-based plastics offered a first alternative to conventional plastic products. This is because bioplastics are made from natural raw materials such as starch and sugar and are partly processed by microorganisms such as bacteria. However, several studies have shown for years that bio-based plastic does not save more CO2 emissions in the long term than conventional plastic. In addition, it consumes important resources in agriculture and industry. So another alternative is needed: What about biodegradable plastic products and what does biodegradable even mean?
Biodegradable products …
… certify themselves by their behavior to degrade into naturally occurring end products. In the case of plastic, the end products are mostly CO2 and water.
Important to know: Biodegradability depends on the chemical structure of the plastic and not on its based raw materials.
This means that there are also petroleum-based plastics that are biodegradable. But: Not every bioplastic is biodegradable.
Bio-based plastics often have the same chemical structure as petroleum-based plastics in order to fit better into the already established production scheme and to be processed as well as recycled with petroleum-based plastics.
Biodegradable plastic products differ in their chemical structure from plastic products commonly used in the industry. Industrial capacity for the production, as well as recycling, of these “different” plastic products is limited (unless they have the same chemical structure as conventional plastics) and they often are sorted out and burned .
About 0.6% of the total plastic production is bio-based. Of this, only 58% is biodegradable (European Bioplastic and PlasticsEurope, 2020).
But why recycle the plastic at all if it is biodegradable?
Das Verfahren zur Kompostierung von biologisch-abbaubarem Plastik ist in Deutschland zum jetzigen Zeitpunkt noch nicht ausgereift.
So muss es in der gelben Tonne entsorgt werden, kann in Sortieranlagen aber nur schwer von anderen Kunststoffen differenziert werden. Daher wird es oft aussortiert und verbrannt – nachhaltig ist das nicht. In die Biotonne darf es ebenfalls nicht, da das biologisch-abbaubare Plastik in den Sortierungsanlagen als Restmüll identifiziert, aussortiert und anschließend ebenfalls verbrannt wird.
Genauso ungeeignet ist der Kompost zuhause, da im Kompost die erforderlichen Bedingungen (wie z.B. hohe Temperaturen und Druck) nicht gegebenen sind.
Denn: Zum Einen wird für den Abbau des Plastiks viel Sauerstoff benötigt, ansonsten bildet sich umweltschädliches Methan. Zum Anderen kann sich das Plastik unter normalen Wetterbedingungen nur schwer abbauen. Wird Plastik nicht komplett in CO2 und Wasser zersetzt, bleiben Mikroplastikpartikel zurück, die für Umwelt und Mensch schädlich sind. Hinzu kommt, dass auch biologisch abbaubaren Kunststoffen eine Behandlung durch Schadstoffe während der Produktion nicht erspart bleibt.
Another option: compostable plastic
Biodegradable is not the same as compostable. But compostable always means biodegradable and the degradation must always meet certain standards. The germination symbol indicates whether plastic is compostable.
European standards (EN 13432) specify a necessary decomposition percentage of 90% of the plastic within 6 months at 60 degrees Celsius as a guideline value in order to title a product as compostable. After 3 months, the degree of decomposition should be so advanced that only 10% of the pieces are larger than 2mm. However, such benchmarks are only practicable in composting plants, where it is preferred to burn the plastic in order to gain thermal energy from the process.
So the same problems can be found with compostable plastic just as it can be found with biodegradable plastic.
The best option: compostable bio-based plastic?
Compostable bio-based plastic may have some advantages over conventional plastic. The plastic is made from natural resources and can reduce the charge on waste management by being degradable.
However, an environmental impact occurs in the extraction of the natural raw materials. Fertilizers, pesticides, arable land and water are needed, which leads to acidification and over-nutrition (formation of too much plankton, etc.) of the ecosystems. In particular, arable land and water are valuable commodities that are taken away from food production, further increasing agricultural pressure. The compostable bio-based plastic also generates greenhouse gases during the production process and, as an end product, ultimately decomposes largely into CO2 and water. A microplastic content cannot be ruled out either and poses a risk to humans and the environment due to the containing pollutants. Since compostable bio-based plastics are also difficult to recycle, they do not contribute to the material cycle and are therefore not sustainable.
So there is no such thing as “environmentally friendly” plastic?
Ergo: Compostable bio-based plastic is probably the best possible alternative in the field of plastic products today. However, it harbors many difficulties and does not perform significantly better than conventional plastic in terms of its carbon footprint.
👉 Therefore, it is better to use no plastic at all than “eco-friendly” plastic.