Pros and cons bioplastics - Which substances do not harm the environment or health?
Plastic is considered to be the biggest environmental problem next to climate change. Plastic waste destroys the oceans, accelerates global warming and the extinction of species. Microplastics damage the health of plants, animals and people. But as environmental awareness grew, so did the initial hope that bioplastics could offer a saving alternative.
However, many of these substances have now come under criticism because some are neither biodegradable nor harmless.1 In fact, however, it is a problem of understanding that goes hand in hand with the question of the correct definition.
What exactly is a bioplastic?
Bioplastics have a longer history than what we are familiar with as plastics today, namely plastics made from fossil fuels such as crude oil. The first factory producing celluloid opened as early as 1869. This plastic is based on cellulose, a renewable raw material obtained from plants. The entire history of cinema, for example, is closely linked to celluloid, from which films are made, right up to the digital age. In addition, everyone is familiar with cellophane, which was produced en masse as early as 1923 for transparent films and many other products.
The basis for bioplastics are mainly vegetable oils and fats, sawdust, food waste, straw, grain, corn, bamboo and potatoes. These provide basic materials such as sugar, starch, cellulose and lignin. They are now used to make a wide variety of products, from disposable crockery, bin liners and packaging materials to furniture.
For a long time, these plastics made from renewable resources were replaced by cheaper plastics based on mineral oil, such as bakelite. Only the ecological crisis brought them back into consciousness. From 1980 onwards, new bioplastics were developed, such as polyactides (PLA), cellulose acetate and thermoplastic starch (TPS).
Important distinction between bio-based plastics and biodegradable plastics
Nevertheless, these substances do not necessarily have to be sustainable, for example if they cannot be degraded. For this reason, a distinction is also made between biologically based plastics (i.e. they are obtained from plant products) and biodegradable or compostable plastics. These can, but do not have to consist of biopolymers that can be decomposed using microorganisms.
Only some of the materials often referred to as bioplastics fulfil ecological criteria. Biodegradable plastics can also lead to the generation of greenhouse gases such as methane.
Biobased plastics, in turn, can have disadvantages due to the energy required for their production or due to the deprivation of agricultural land for food production. Only certain materials are actually compostable within 12 weeks in the sense prescribed by the technical standard DIN EN 13432. Therefore a more detailed understanding of these plastics is very important.
How are bioplastics exactly defined?
The International Union of Pure and Applied Chemistry (IUPAC) recommends the term "biobased polymers" to distinguish them from polymers made from fossil materials and to replace the disreputable term "bioplastics". It points out that biobased polymers are not considered to be superior as long as this is not proven on the basis of the life cycle of the material. 2
Consequently, high demands must be made on bioplastics in order for them to stand out positively from conventional plastics. The developments of recent years with new materials, also known as novel bioplastics and drop-ins, such as the "liquid wood" made from lignin, give rise to great hope.
Which bioplastics have sustainable qualities?
Of the biodegradable plastics developed in recent years, "the bio-based starch plastics, polyactide and polyhydroxy fatty acids as well as fossil-based polyester have become particularly popular. 3
- Starch and starch blends
Plastics obtained from starch play an important role: "Thermoplastic starch (TPS or starch blends) is currently the most important and most common bioplastic. Its share of the total bioplastics market is approximately 80 %". 4 It is produced from potatoes, wheat and maize, and is used to make plant pots, drinking cups or carrier bags, for example. However, bioplastics rubbish bags do not belong in the compost or in the organic waste bin, but must be disposed of with the residual waste.
- Polylactic acid
In addition, polyactide (PLA) is increasingly used. "Polyactide (PLA) or polylactic acid is a biodegradable polyester and is polymerised from the monomer lactic acid. 5 PLA can be easily processed into films, bottles and trays, but is also used for implants and sutures in medicine.
TPS and PLA combine two important features for an advantageous biobased plastic: they are biologically based and biodegradable.
- PHF or PHB (polyhydroxybutyric acid)
Polyhydroxybutyric acid (PHB) or generally the "polyhydroxy fatty acids (PHF) are also enjoying increasing popularity. They are thermoplastic polyesters obtained by the action of bacteria or fungi on sugar or starch.". 6 These lead to products with very good mechanical properties.
Liquid wood: Example of a sustainable bioplastic made of lignin
Lignin is a raw material contained in wood waste that gives plants the necessary strength. It is well suited for the production of very valuable biobased plastics. The brand product Arboform®, which is also known as liquid wood, was created in 1998. After the turn of the millennium, applied research was carried out at the Fraunhofer Institute, which led to the development of further lignin-based plastics. 7 This also led to the development of Arboblend®, a biodegradable material consisting of a formulation of various biopolymers. These biobased plastics combine several important characteristics for sustainability: The processing of lignin conserves resources and at the same time does not burden the environment with plastics that are difficult to degrade. There are now many applications for this, from musical instruments to household goods. But also in Albfilter's water filters, the liquid wood used underlines their sustainability.
Bioplastics or biopolymers, as terms, require a precise delimitation with regard to their origin and the possibilities of degrading them in an environmentally compatible way. After a phase of scepticism, numerous new developments of biopolymers over the last 20 years have raised hopes of their use as a sustainable alternative to conventional plastics. Consumers, for their part, can contribute to a better ecological balance of bioplastics through the proper use and reuse of products.
Related articles and products
- IopScience: "Land use mediated GHG emissions and spillovers from increased consumption of bioplastics" WWW: https://iopscience.iop.org/article/10.1088/1748-9326/aaeafb/meta (06.12.2018)
- Wikipedia: "Bioplastic" WWW: https://en.wikipedia.org/wiki/Bioplastic#cite_note-IUPAC2012-5 (11.07.2020)
- Federal Environment Agency: "Biodegradable plastics" WWW: https://www.umweltbundesamt.de/sites/default/files/medien/publikation/long/3834.pdf (08/2009)
- ibid. (3)
- ibid. (3)
- ibid. (3)
- Fraunhofer Institute: "Enzymatic modification of lignin" WWW: https://www.igb.fraunhofer.de/de/forschung/industrielle-biotechnologie/bioprozessentwicklung/etablierung-und-scale-up-von-technischen-enzymprozessen/Enzymatische-Modifikation-von-Lignin.html (No date given)