PROTEIN-BASED BIOPLASTICS profile
by Charlotte Bolinski, Amon Zänker & Sophia Reißenweber
Description of the material:
Proteins consist of amino acids and are built up and broken down by enzymes. Depending on the protein source, they differ greatly in their composition. Proteases are enzymes that cut up other proteins. Through cross-linking of amino acids by a certain enzyme, water-resistant protein bioplastics can be created. Plasticisers, such as glycerol, can be used to control and adapt material properties and textures. The spectrum of potential raw materials suitable for the production of protein plastics is very wide. They can be of animal origin (casein, fibroin, collagen, keratin) or of plant origin (gluten, algae, oil).
Properties of the material:
– short durability
– water resistant or soluble in water
+ biodegradability as an additional option at the end of the product life
+ edible with high nutritional value
+ simple methods of production
+ simple processing options
+ short life span
+ transparent/translucent (casein)
– gluten intolerance / coeliac disease
– competition with the use as animal feed
– contamination possible (fungi/bacteria)
– poorly recyclable
– good barrier properties (casein)
Possibilities/obstacles of recycling:
Recycling could be rather difficult for certain products, which consist mainly of protein, as the material is relatively short-lived without chemical additives and natural environmental influences already degrade the bioplastic after longer storage. In the case of strong humidity, it loses stability and dissolves. A high-quality recyclate would therefore only make sense to a limited extent for certain proteins through suitable additives or production processes. Many questions are still open here, as protein structures differ greatly from one another and are sensitive.
Envisaged areas of application:
In the food sector: as food packaging, nutrient supplier for humans and animals
In transport logistics: as a filler or protection in shipping/transport logistics
As an alternative to chemical binders/adhesives: as a substitute for chipboard, for other semi-finished products, e.g. in trade fair construction
Agriculture: as nitrogen storage / fertiliser, mulch films, plant binders, vine clips, etc./.
Horticulture: as flower pots, supports, etc.
Forestry: as protective sleeves for young trees, identification tags, etc.
Fishing equipment for single use: as mussel nets, fastening clamps, etc.
Recreation : fireworks, filling for hunting cartridges, etc.
Regional importance of the material:
Possible protein suppliers are based locally. Waste products from the food industry (e.g. whey; gluten) could be used to produce protein bioplastics.
It is possible to intervene in the current value chain from the waste materials of the dairy industry or grain processing and to generate a higher-value product from the waste material, which would be nutritionally utilised by livestock farms or consumers after use.
Likewise, edible materials could be integrated into the product cycles of industry in order to avoid packaging.
Motivation for the development of the material:
Proteins can be used to create plastics that are very quickly degradable and have a high nutritional value. Especially in the food industry, the use of packaging is extremely high and the material life cycle of oil-based plastics is relatively short.
Alternative binders are also advantageous in the production of semi-finished products in order to obtain a higher-quality recyclate and to find alternatives for the conventional adhesives that are hazardous to health.
Variants of the material:
Depending on the starting protein, various plastics with different material properties can be generated using different methods. In combination with sand and wood, proteins act as binders and can thus be used as degradable composites. It is also possible to spray protein layers onto packaging or products, but also to cast new plastic films. Baking in the oven gives the gluten material foamy properties. The addition of glycerine increases the elasticity of the plastic.
– Binder (gluten + wood/sand/…)
– Foam (gluten)
– Film (casein, collagen)
– Spray (casein, eggshells)
Procedure of production / processing:
Binder: protein is mixed together with sand / wood, heated and pressed into shape.
Gluten foam: Caustic soda is first dripped onto gluten, with which it reacts and shapes spheres. These are baked at 150°C in the oven for 10min. The material can then be moistened and baked again with several spheres in a mould so that they form a volume body. Precise temperature control during production is essential for the success of the process, otherwise the proteins will be destroyed.
Casein film: Casein is heated with water and glycerine, then poured into Teflon trays and dried.
Interpretation of the term bioplastic:
As early as 1897, a protein bioplastic made from milk components was used to produce galalith. Protein plastics belong are biobased (from renewable raw materials) and biodegradable.
Consumers can dispose of the plastic in the usual way in their own compost or in the bin for organic waste.
– within 20 days
– soluble in water
– digested in the human/animal body within a few hours
– by microorganisms/ enzymes
Biodegradability can be used to add new functionalities to the product. For example, useful additives can be added that are released during or at the end of the product‘s life. Thus, biodegradability offers technical advantages not only at the end of life, but also during use.
Foil can be printed, coloured (possibly food colouring), welded, thermoformed, embossed, … (further experiments possible)
Gluten foam balls can be formed into various shapes, additives (colour, taste) can be tested, the production process must be optimised, …
Sand or wood can be used as a filler and pressed into various shapes to fulfill a wide variety of functions.
Questions that arise:
Besides wood and sand, which raw materials would also be worthwhile to be bonded with proteins as binders?
How do I extend the service life and elongate degradation?
In which industrial sector does the utilisation of by-products and waste materials from different biomasses for bio-plastic production make sense, which are not in competition with livestock farms?