With the plastic pollution problem attracting widespread attention around the world, degradable plastics are seen as the golden key to solving white pollution.
However, are degradable plastics really degraded in the existing plastic recycling system? How much do degradable plastics, which are costly compared to traditional plastics, contribute to the fight against plastic pollution? And how cost-effective is it?
Degradable ≠ unconditional degradation
Degradable plastics is a general term for a large group of degradable materials that can be degraded into environmentally sound substances under specific natural environmental conditions after use. Degradable plastics first appeared in the 1960s, and have gone through the stages of development in which they were mixed with conventional plastics, degraded by light and heat conditions, and degraded by microbial enzymatic reactions. Degradable plastics mixed with traditional plastics (e.g., polyethylene, polypropylene) can only make the traditional plastics disintegrate more easily into tiny fragments, producing more microplastics to pollute the environment, and therefore cannot be considered degradable. Photo-thermal degradable plastics are poorly degradable and are constrained by natural conditions such as temperature and light intensity. For example, mulch buried in the ground will have little or no effect on decomposition due to the absence of light. Therefore, only in the biological conditions of degradable plastics, also known as biodegradable plastics, is truly degradable plastics, only to have the value of the prevention and control of plastic pollution.
People often have a misunderstanding that degradable plastics can be degraded in any natural environment. In fact, degradable plastics have degradation characteristics only when they enter a specific environment, and they are not degradable under any natural conditions.
Different degradable plastics can be degraded under composting, soil burial, fresh water and other conditions. However, compared with the soil environment, the marine environment is characterized by high salinity and low microbial density, and those plastic products that can be degraded by microbial enzymatic reactions on land will often degrade and fail in the marine environment.
