Plastic & Co. From Nature

Cellulose nanocrystals: implants from nature

Cellulose – a substance that plants have been producing in their cell walls for millions of years – is the main chemical component of wood. But it is also to be found in algae, fungi or bacteria. We can use it as a source of energy, as a building material or to make clothing. Scientists have isolated tiny structures from cellulose, so-called nanocrystals. In relation to their weight, nanocrystals are about eight times as strong as stainless steel and about as rigid as glass fibre. Since another feature of these crystals is their electrical conductivity, researchers are also working on potential applications in electronics. In 2017, for example, using cellulose nanocrystals, ETH Zurich and Harvard University jointly developed eco-friendly ink for 3D printers. It can also be used potentially in the manufacture of prostheses and implants or in the automotive industry. [1][2][3][4]

Artificial mother-of-pearl: robust material

It shimmers in the most beautiful colours: nacre, the innermost layer of shells or snails, is not only aesthetically pleasing, but also highly stable. It is made up of miniature lime platelets lying on top of each other that are held together by organic materials. In 2016, scientists at the University of Konstanz and the University of Science and Technology of China (Hefei, China) were the first to reproduce the structure of natural nacre artificially. In doing so, they used the exact same components that occur in nature: lime, chitin and silk gel. With their new procedure, the chemists created a biomineral whose properties are almost identical to natural mother-of-pearl: hard and shatterproof. [5]

Trousers from the sea

Cellulose and brown algae are the rather unlikely ingredients of clothing made of SeaCell, a material developed by a Thuringian company named smartfiber. To produce the material, seaweed is harvested in Icelandic fjords, but only the upper portion of the seaweed sheets (or brown algae) is cut every four years to ensure that the seaweed can sprout again. The seaweed is then dried, ground and combined with cellulose fibres from sustainably grown wood. The material is carbon-neutral and completely biodegradable. [6][7] It is produced in a closed circulatory system that generates zero chemical waste. Among other things, SeaCell is used to manufacture and market sports and leisure clothing.

Vegan leather alternative: sustainable bags made from apple pomace

Apples are not only delicious – they can also provide a sustainable alternative to leather. For this reason, a South Tyrolean family business named Frumat has developed “AppleSkin”. This vegan material is produced from the solid residues generated during apple juice production. Seeds and skins are first dried and ground into a very fine apple powder. This powder is then mixed with a polyurethane binder and applied to a roll of cotton fabric, before everything is put in an oven and “baked”. This makes the material robust and weather-resistant. The next step involves the AppleSkin being embossed to give it a leather-like texture, although other textures can also be produced according to individual desires. The vegan material is used, among other things, to make recyclable shoes, bags, furniture or book covers. To date, the material is not biodegradable. [8]

Not all bioplastics are the same

A major focus in the development of sustainable materials is on biodegradable plastics made from renewable raw materials. Most plastics are produced from fossil raw materials, such as crude oil. In recent times, however, many ideas and alternatives have been developed for producing this flexible and durable material from renewable materials. Bioplastics can be based, for instance, on algae, orange peel, pine needles, corn, wheat or biological waste and proteins. One type of bioplastic is even made from the shells of shrimp and crab in combination with a silk protein.

However, not all bioplastics are the same. Experts distinguish between three variants. Firstly, biological, non-degradable plastics, which are partly made from renewable raw materials, but also from crude oil. Secondly, crude-oil-based plastics that are made biodegradable through additives. Thirdly, plastics that consist entirely of renewable raw materials and are biodegradable. The Umweltbundesamt, Germany’s central environmental authority, considers only the third category as being truly sustainable. Until now, bioplastics have mostly been produced on the basis of starch, which is a component of plants such as corn (this type of bioplastic makes up 80 per cent of all bioplastics on the market). [9] Bioplastics produced without crude oil release no fossil CO₂ if the plastic is incinerated during waste disposal.

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How eco-friendly is bioplastic?

Retrieving the basic materials for plastics and suchlike from the field or from the sea, for example in the form of algae, seems like a possible option for the future. However, there are also critical voices. At the University of Bonn, for instance, scientists investigated how eco-friendly and climate-friendly bioplastics are in the first place. [10] In their study, they simulated possible developments in the event of a future increase in the production of bioplastics. “The production of large quantities of bioplastics would change land use,” says Neus Escobar of the University of Bonn’s Institute of Food and Resource Economics. [11] “On a global scale, this could lead, for instance, to an increase in the conversion of forest land into farming land. Forests, however, sequester considerably more carbon dioxide than, say, corn or sugar cane, if only because of their larger biomass.” Such an effect has already been observed with biofuels, for the production of which forests were cleared. [12]

“Increased use of bioplastics from cultivated crops doesn’t seem like an efficient strategy to save the climate,” Escobar says. Switching to bioplastics would also lead to rising food prices as agricultural land would become scarcer. [13] The balance could presumably be different if, for example, plant waste were used for bioplastics production, says Escobar. Therefore, he thinks it advisable to concentrate research on this type of bioplastic and to develop the corresponding procedures to market maturity. [14][15]

However, using renewable raw materials can not only lead to competition for land, but may also turn into an economic burden for companies – for example, if eco-friendly materials are more expensive than other materials. Experts speak of a trade-off, a conflict between the goals of sustainability and profits. So-called rebound effects are criticised too: the use of renewable raw materials in plastics production, for example, can reduce the price of crude-oil-based plastics – and thus lead to an increase in the consumption of this fossil fuel. The consumption of bioplastic itself may also increase because, thanks to the positive image, consumers buy more and more “green plastic” – and thereby end up harming the environment.