What is the difference between degradable, biodegradable and compostable?

(1) Degradable plastic

Degradable plastics include plastics that can be degraded by physical and biological factors (light or heat, or microbial action). The so-called aerobic degradation (that is, accelerated degradation by catalysts or activators at high temperatures) or photodegradable starch-polyethylene plastics will cause some environmental problems. These materials do not degrade as fast as compostable plastics and may leave debris. These degraded water-repellent fragments have a large surface area and may migrate to groundwater and soil. Some hydrophobic highly toxic substances such as PCB and DDT, such as PCB and DDT, are adsorbed and retained on the surface, making the content of toxic substances as high as 1 of the background content. Millions of times, enough to become a delivery system for toxic substances in the environment. Therefore, it is necessary to ensure that the product is completely biodegradable in a very short time determined by the treatment facility.

(2) Biodegradable plastics

Biodegradable plastics are those that can be completely digested by the microorganisms in the processing system as food for energy (entering the food chain). This complete microbial digestion/utilization is determined by testing whether the carbon element of the test plastic can be completely converted into CO2 through the microbial process occurring in the cell.

(3) Compostable plastic

In addition to being biodegradable by microorganisms, there must be a time requirement for a plastic to be called "compostable" plastic. For example, ASTM 6400 (specification for compostable plastics), ASTM D6868 (specification for biodegradable plastics used for surface coating of paper or other compostable media) or EN 13432 (compostable packaging) standards stipulate that these materials are used in industrial composting environments It should be biodegraded within 180 days. The industrialized composting environment refers to the prescribed temperature of about 60°C and the presence of microorganisms. According to this definition, compostable plastics will not leave fragments longer than about 12 weeks in the residue, do not contain heavy metals or toxic substances, and can sustain plant life.