Biodegradable plastics
Biodegradable plastics refer to plastics that can be degraded by microorganisms in nature, such as in soil or sand, or under specific conditions such as composting, anaerobic digestion, and aqueous culture. These plastics are eventually completely degraded into carbon dioxide (CO₂), methane (CH₄), water (H₂O), mineralized inorganic salts of all elements, and new biomass. According to the technical requirements of GB/T20197 "Definition, Classification, Marking and Degradability Requirements of Degradable Plastics," the biodegradability rate of biodegradable (degradable) plastics must be greater than 60%.
Compostable plastics
Compostable plastics can be degraded and decomposed under compostable conditions due to biological reactions, and finally completely decomposed into carbon dioxide (CO₂), water (H₂O), and mineralized inorganic salts of the elements they contain, as well as new biomass. The heavy metal content, toxicity test, and residual fragments of the formed compost must comply with relevant standards. The biodegradation rate of compostable plastics must also be greater than 60%.
As can be seen from the definitions, the degradation principles of the two materials are essentially the same. Both primarily undergo degradation through microbial action, breaking down the materials into small molecules and new biomass. In the following, both materials are referred to as "biodegradable plastics.