Plastic recycling technologies can be divided into two categories: physical methods (material recycling and heat recycling) and chemical methods (chemical recycling). Among them, the recycling and reuse of materials is relatively simple and low-cost. For example, the current recycling rate of PET bottles is more than 90%. However, the recycling of materials cannot avoid the degradation of the quality of repeatedly recycled plastic products, which greatly limits the recycling.
Chemical recycling and reuse can be divided into gasification, oilification, and methanol recovery of waste plastics, and monomerization and oligomerization of waste plastics. From the perspective of circular economy, the latter has greater advantages. Chemical recycling is also feasible for the recycling of biodegradable plastics. This is because most biodegradable plastics are formed by the combination of ester bonds and amide bonds that are prone to hydrolysis. Depolymerization is easier to occur, so it is easier to monomerize and recover. Therefore, how to deal with biodegradable plastics at present Research on chemical recycling and reuse is also gradually increasing.
Regardless of whether biodegradable plastics are produced by microorganisms, natural substances or chemically synthesized, they must be recycled as much as possible. This is because the biodegradable plastics are recycled, and the energy consumption and carbon dioxide production will be relatively small in the overall life cycle. In this regard, bio-based polymers such as polylactic acid (PLA) are the same. In the production of these substances, the fermentation process and the chemical conversion process of the products require corresponding energy, so it is even more necessary to seek recycling-type recycling.
The recycling and reuse processes applicable to biodegradable plastics include reuse, material recycling, heat recovery and reuse, chemical recycling and reuse, and biological recycling and reuse (Figure 8-1). There are still many petroleum-based biodegradable plastics. In the future, with the development of biomass manufacturing technology, it is expected to gradually become bio-based biodegradable plastics. However, due to the limited resources, even for bio-based biodegradable plastics, we must continue to study the simplification of manufacturing engineering and life cycle cycles, the reduction of moving materials, the higher performance and higher skills of materials, and the recycling technology and The corresponding system.