Although it has similar characteristics to traditional synthetic plastic, both in its lightness and strength, biodegradable bioplastic is a sustainable, low-impact, high-performance alternative for use and service. It enables more sustainable product life cycles within a circular economy model.
One very important quality in determining the degree of sustainability of bioplastic products is compostability. Compostable materials are those that can be organically recycled together with food waste, becoming compost through a process of biological decomposition of organic matter that takes place under controlled conditions.
Biodegradable polymers
Bioplastics are composed of biopolymers, which are produced through biological processes, although they are not necessarily biodegradable. In fact some polymers obtained from natural bio-based sources are not biodegradable. Therefore the use of bio-based raw materials is not sufficient in itself to obtain a biodegradable bioplastic, as they can also be used to produce traditional polymers, e.g. so-called green polyethylene, which behaves like fossil-based polyethylene at the end of its life and is therefore not biodegradable and compostable. These products can be described as ‘plant plastics’ to avoid being mistaken for biodegradable bioplastics.
Moreover it is not always necessary for raw materials to be derived from plants: in fact there is a group of fossil polymers that are perfectly biodegradable and compostable.
The biodegradability of a polymer or plastic material does not therefore depend on whether it is derived from renewable (biomass) or non-renewable (fossil) sources, but on its chemical structure.
Here are some of the main polymers used in the production of biodegradable bioplastics:
BIOPOLYMERS FROM BIO-BASED SOURCES
- Polysaccharides. Represent the most characteristic family of natural biodegradable polymers, or biopolymers. The most common are starch and cellulose. Main applications: food packaging.
- PHAs. The best-known polymers are obtained by synthesis through fermentation within genetically modified microorganisms, starting from sugars or lipids. Main applications: glasses, cups and other paper and cardboard containers.
- PLA (polylactic acid). Thermoplastic polyester that can be obtained by polymerising lactic acid, which in turn is produced through bacterial fermentation of starches. Main applications: plates and cutlery.
- PBS (polybutylene succinate). Semi-crystalline thermoplastic polymers from the aliphatic polyester family. Main applications: films, bags or containers for food and cosmetic packaging.
- PEF (polyethylene furanoate). Aromatic polyester, chemical analogue of polyethylene terephthalate and polyethylene terephthalate. Main applications: bottles, films and fibre
FOSSIL POLYMERS
- PBAT (polybutylene adipate terephthalate). Aliphatic-aromatic copolyester obtained by polycondensation between butanediol (BDO), adipic acid (AA) and terephthalic acid (PTA). Main applications: organic waste collection bags, transparent films, fruit and vegetable bags and agricultural films
- PBS (polybutylene succinate). Semi-crystalline thermoplastic polymers from the aliphatic polyester family. Main applications: films, bags or containers for food and cosmetic packaging.
- PVA (polyvinyl alcohol). A water-soluble synthetic macromolecule polymer obtained by the polymerisation of vinyl acetate. Main applications: paper, textiles, coatings
Biodegradability is the capacity of a material to be broken down into simpler substances through the enzymatic activity of microorganisms. At the end of the biodegradation process, the initial organic substances are entirely converted into simple inorganic molecules: water, carbon dioxide and methane.