Conventional plastics are one of the biggest sources of white pollution because they require a very long time to degrade under normal environmental conditions. Biodegradable plastics have been invented as an alternative. In the following, we will introduce the seven most typical biodegradable plastics.
1. Polylactic Acid (PLA)
Polylactic acid (PLA) is a new type of biodegradable material produced from renewable plant resources such as corn starch. PLA has its largest application in food packaging and 3D printing—two of its most common applications. It is highly biodegradable, as it can be completely broken down by microorganisms in the environment to ultimately convert into carbon dioxide and water without leaving any pollution for the environment. This biodegradable plastic is highly renowned for its environmentally friendly effect. PLA accounts for 45.1% of biodegradable plastics, which makes it the leading material among them.
PLA degradation occurs in two steps:
- Chemical hydrolysis to lactic acid monomers.
- Microbial degradation of lactic acid to CO₂ and water.
For example, food containers based on PLA can degrade completely in just 60 days, achieving both ecological and economic benefits.
2. Polyhydroxyalkanoates (PHA)
PHA is a family of biodegradable polyesters that are produced by microorganisms through fermentation of different carbon sources. The most common ones are:
- Poly-3-hydroxybutyrate (PHB)
- Polyhydroxyvalerate (PHV)
- PHB/PHV copolymers (PHBV)
Uses: Disposable tableware, non-woven cloth, packaging films, agricultural mulch films, toys, coatings, adhesives, and fiber.
3. Poly-ε-caprolactone (PCL)
PCL is a low-melting polymer (62°C) obtained by ring-opening polymerization of ε-caprolactone. PCL biodegradability was investigated as early as 1976, where its complete degradation by microorganisms in aerobic and anaerobic environments was confirmed.
Unlike PLA, PCL is hydrophobic but less degradable. It is also easier to synthesize and less expensive. PCL has great processing properties and can be cast into films and other products with common plastic-making machines.
4. Polyester-Based Plastics – PBS/PBSA
Polybutylene succinate (PBS) is manufactured primarily from butanediol and succinic acid. It can be made from renewable resources like starch, cellulose, and glucose by fermenting them or directly from petrochemical feedstock, hence enabling a sustainable “from nature, back to nature” strategy. It also saves costs significantly through fermentation-based manufacturing.
Advantages of PBS over other biodegradable plastics:
- Good heat stability (appropriate for food service applications).
- Low processing requirements.
- Excellent hydrolysis resistance and storage stability.
Uses: Packaging, tableware, cosmetic and pharmaceutical packaging, disposable medical devices, agricultural films, slow-release fertilizers, and biomedical materials.
5. Aliphatic-Aromatic Copolyesters
Aliphatic-aromatic random copolyester Ecoflex is manufactured by the German company BASF from adipic acid, terephthalic acid, and 1,4-butanediol. BASF has also produced polyester-starch-based biodegradable plastic goods with an annual capacity of 140,000 tons.
6. Polyvinyl Alcohol (PVA)
Water-soluble PVA film is a new-generation plastic material that is gaining international attention. Leveraging PVA’s film-forming property and double water & biodegradability, it dissolves completely in CO₂ and H₂O, and therefore is indeed a very green, high-tech packing material. PVA films are widely applied in packaging.
7. Carbon Dioxide Copolymer
This novel synthetic material is prepared by copolymerization of CO₂ (as a monomer) and epoxides in the presence of a bimetallic PBM-type catalyst to form aliphatic polycarbonate (PPC). After post-processing, it is a CO₂-based resin material. The optimization of applications is being researched.
All seven biodegradable plastics are at the frontier of material technology for a sustainable future, offering eco-friendly substitutes for normal plastics with a smaller ecological footprint.
