In packaging technology, bioplastics are seen as a sustainable alternative to environmentally harmful plastics. But what bioplastics exist, what do they consist of and how are bioplastics produced? Here you will read what you should definitely know about this topic!
Although bioplastics have gained some market shares in the past, they still account for less than 1 percent of total plastics. In 2014, the global production capacity was estimated at 1.7 million tons, by 2019 Bioplastics Europe expects a fourfold increase to 7.8 million tons. "François de Bie, CEO of European Bioplastics, is convinced that the market for bioplastics will grow by 50 percent in the medium term despite the low oil prices. Packaging remains the leading application area for bioplastics, accounting for around 40 percent (1.6 million tonnes) of the total bioplastics market in 2016. The most common examples of bioplastics packaging include starch-based packaging chips or carrier bags. In addition to flexible packaging, there are now biological alternatives for stiff bioplastics, for example for the packaging of creams and lipsticks. The beverage industry is also an important customer for bioplastics.
Types of plastics used
Even the definition of bioplastics is difficult because the term is not protected by law. In the meantime, the distinction between products based on regrowing raw materials, products that are biodegradable and products that combine both properties has established itself. Besides starch, PLA (polyactide) and PHB (polyhydroxybutyric acid) are among the most frequently used thermoplastic bioplastics.
PLA is mainly based on corn and is particularly suitable for short-life packaging films or thermoformed products (e.g. beverage or yoghurt cups, fruit, vegetable and meat trays). PHB is a polyester that can be produced by fermentation from renewable raw materials and has properties similar to those of the petrochemically produced plastic polypropylene. Bio-PET (which is often used for bottles) is chemically identical to conventional PET, but is not based on petrochemical raw materials but on renewable raw materials such as sugar cane. Its great advantage is that the plants for the production of bottles, for example, only have to be adjusted. In general, bioplastics behave similarly to conventional plastics during processing, so that the use of blown film lines and extruders is just as possible as thermoforming and deep-drawing.
No clear winner in the life cycle assessment
Bioplastics undergo similar steps during processing (e.g. polymerisation) as their colleagues do on the basis of crude oil. Their advantage lies in their faster biological degradability, which is between eight and ten weeks, depending on temperatures and environmental conditions. However, according to some critics, if these optimal conditions are not met, this time can be considerably exceeded. For example, PLA requires high temperatures for decomposition, as used in industrial composting plants. In contrast, packaging made of thermoplastic starch can be disposed of in household compost.
A study by the Federal Environment Agency in 2012 therefore does not give a clear view when it comes to the ecological balance, but emphasises the complexity of such an assessment. According to this, bioplastic packaging often shows better results in the life cycle assessment in terms of greenhouse gas emissions and fossil resource consumption, but are generally no more advantageous overall ecologically than corresponding packaging made of fossil plastics. Moreover, biodegradability is not a unique selling point of bioplastics. More than 25 years ago, BASF launched Ecoflex, BASF's first biodegradable and compostable fossil-based plastic, which can also be completely composted.
Is recycling a better alternative?
In general, almost all household packaging is already recycled today, more than half of which (56 percent) is made from materials (around 20 years ago this was only 3 percent). The rate for PET bottles is much better, with 98 percent recycled and returned to the material cycle, so that today each bottle already consists of around 25 percent regranulates. PET and Bio-PET bottles can also be recycled together without any problems.
Nevertheless, the recycling of bioplastics is to be further established. While biobased but not biodegradable plastics such as bio-PE and bio-PET can be recycled with "normal" plastic waste, green plastics often end up being burned or composted. Effective methods for recycling the materials are therefore of great interest. Initial attempts to establish a closed material cycle are now being offered, and there are several pilot projects for corresponding sorting and recycling plants.
Conclusion and outlook
Of the 14 million tonnes of packaging produced annually in Germany, almost 40 percent are made of plastic. Around 1.8 million tons of this is accounted for by short-lived or one-off plastic packaging such as films, bags, carrier bags, sacks or disposable cutlery and dishes. These packagings could also easily be made of starch plastics and polylactides.
Both in Germany and throughout Europe, about half of the 6 million tons of "disposable packaging" could be replaced by bioplastics. However, due to the strong competitive structures on the plastics market, bioplastics are not yet able to keep up with the price level customary in the industry. Nevertheless, the positive growth trend is expected to continue, according to the latest survey by European Bioplastics: the worldwide production capacities for bioplastics will continue to increase in the coming years from around 4.2 million tons in 2016 to around 6.1 million tons by 2021. The proponents have long since moved away from the argument of rapid compostability to the argument of durability and better technical properties.
* Sabine Mühlenkamp is a specialist journalist for chemistry and technology