In the context of the increasingly depleted petroleum resources and the global promotion of low-carbon environmental protection, bioplastics have incomparable advantages over traditional plastics in terms of resource utilization and degradability. Industry and governments are beginning to propose "degradable plastics" as an alternative to traditional plastics. However, in the face of a mix of degradable plastics with various names on the market, the public, and even related practitioners are often confused.
Can these advertised degradable plastic materials really be completely decomposed in a certain environment?
In March 2019 last year, the EU officially passed a number of proposals for single-use plastic products, including the prohibition of oxidatively degradable plastics (Oxo-degradable plastics). /904, which includes a ban on the circulation of single-use plastic products made from oxo-degradable plastics in EU member states. Why is the EU banning this degradable plastic?
In fact, as early as 2017, an initiative by the Ellen MacArthur Foundation to ban oxidatively degradable plastic packaging was supported by more than 150 companies and organizations, including well-known brands: Unilever, Nestlé, and Pepsi, environmental NGOs Greenpeace and WWF, and M&S.
So, why have there been constant calls to ban oxidatively degradable plastics internationally in recent years?
01
What is oxidatively degradable plastic?
According to a report by the European Plastics Association (Plastic Europe) [2], oxidatively degradable plastics (Oxo-degradable plastics) are based on traditional plastics, adding chemical additives to make them degrade under aerobic conditions, And accelerated decomposition under the conditions of light and/or heat, it is also proposed that a more appropriate name for oxidatively degradable plastics may be thermo- or photo-fragmentable plastics.
The environmental charity Ellen MacArthur Foundation mentioned in its oxo-statement that oxidatively degradable plastics and similar materials are marketed under various names, including oxidatively biodegradable, photo/thermally degradable, Plastics that can be oxidatively cracked or contain pro-oxidative additives, etc. These terms can be confusing. Based on available evidence, plastic packaging that claims to contain chemical additives (both organic and inorganic) that accelerate biodegradation, including enzyme-mediated degradable plastics, can also create problems similar to oxidatively degradable plastics.
02
The hazards of oxidatively degradable plastics
According to the United Nations Environment Programme's "Biodegradable Plastics and Marine Litter" report [3], the initial degradation of oxidatively degradable plastics may produce many small fragments (ie microplastics) , but the fate of these small fragments is little known. . As with all degradation, the rate and extent of how plastic breaks down and is transformed by microorganisms depend on the surrounding environment. However, there is no conclusive public evidence that, with the exception of industrial composting, oxidatively degradable plastics can be completely mineralized and degraded in the natural environment.
Fig. Plastic debris in the ocean
A 2010 UK government assessment concluded that the environmental impact of oxidatively degradable plastics was not reduced compared to conventional plastics. The recommended options for disposal of waste oxidatively degradable plastics are incineration (preferred) or landfill. "These oxidatively degradable plastics do not degrade for 2-5 years, and they remain visible waste until they degrade."
In April this year, a research report released by the University of Plymouth showed that several different types of plastic bags claimed to be degradable were placed in open environments, soil, ocean and laboratory environments, and their degradation effects were monitored for 3 years. Results It was found that in addition to composting, the degradation of degradable plastics was satisfactory, and the plastics treated by other methods (including oxidative biodegradation) were not satisfactory.
The picture shows the oxidative biodegradable plastic bags stored in the seawater environment (top picture) and soil environment (bottom picture) for 3 years,
It is no problem to carry objects weighing 2.25 kg (Photo: The research team of the University of Plymouth)
Also, oxidatively degradable plastics are not suitable for composting environments. Composting requires not only materials that are biodegradable, but also that these materials can eventually become part of the fertilizer and provide nutrients to the soil. Research has shown that oxidatively degradable plastics are not suitable for any form of composting or anaerobic digestion and do not meet current EU compostable packaging standards. The residual plastic fragments and possible microplastics of oxidatively degradable plastics will adversely affect the quality of composting.