Plastics bring great convenience to people's lives, but at the same time, the problem of environmental pollution is becoming increasingly serious. How to balance between convenience and environmental protection has become a common issue facing mankind around the world. Today, we share several plastic degradation methods, hoping to bring you inspiration.
1, light, oxygen degradation and biodegradation
At present, the main ways to degrade plastics are light, oxygen degradation and biodegradation.
Photodegradable and oxygen-degradable plastics are generally mixed with additives in traditional petrochemical plastics to accelerate the fragmentation of plastics under light or higher temperatures. Current photodegradable and oxygen-degraded plastics cannot be fully degraded within a controlled time, and some plastics will still remain in the environment.
However, biodegradation includes the premise that plastics are produced from biomass rather than from petrochemical raw materials. It would be ideal if biodegradation could degrade both plastic products made from petrochemical materials and plastic products made from biological materials. According to reports, 83% of biodegradable plastics are actually "compostable plastics", and its efficient degradation requires a temperature of up to 50 ° C and 55% humidity, but the general environment is difficult to achieve such conditions.
2. Enzymes that can "eat" polylactic acid plastics
Swiss scientists have discovered a new "cold-adapted microbe" that can break down and digest different types of plastic at low temperatures. The discovery is a first step toward developing more cost-effective industrial-scale methods for breaking down plastics, with the hope of eventually eliminating plastic pollution from the planet.
The Swiss scientists traveled to Greenland, Svalbard and the alpine and Arctic regions of Switzerland to sample 19 species of bacteria and 15 species of fungi found on discarded or intentionally buried plastic. Through experiments, the scientists found that at temperatures of 15°C, more than half (56%) of the strains, namely 11 fungi and 8 bacteria, digested PUR, and 14 fungi and 3 bacteria digested PBAT and PLA. However, none of the microorganisms were able to digest PE during the 126-day culture period.
Coincidentally, Xu Ting's team at the University of California, Berkeley, has invented a new way to degrade plastics. They wrap an enzyme that can "eat" plastic in specific molecules, and in just a few weeks, the plastic can be completely decomposed under the action of slightly higher temperatures and water, not only that, the decomposed plastic will become a soil microbial feed, truly become "compostable plastic."
3. Bacteria that "chew" PET plastic
In 2016, a research team led by Yasuhei Oda of Kyoto Polytechnic Fiber University and Kenji Miyamoto of Keio University in Japan discovered that a microbe can swallow terephthate plastic (PET), a type of plastic made from petrochemical products.
The PET-eating bacterium is called Sakaibacterium Osaka. After careful microbiological screening, the Japanese research team found that a bacterium was able to grow in large numbers on PET films, so the bacterium was named Sakai Osaka. The bacteria can "munch" on PET polymers at a mild temperature of 30 ° C. Based on this, the researchers believe Sakai could be used to degrade PET plastic.
However, further research found that these bacteria like amorphous PET, and the actual production and use of plastic products is crystallized PET, so the effect of this bacteria to degrade PET is not ideal. In addition, Sakai bacteria also degrade plastic slowly under natural environmental conditions, and it takes six weeks to completely degrade a small plastic film. For this bacteria to reach the practical stage, it needs to be further optimized before it can actually be used to clean up the world's PET plastic waste. However, Japanese researchers say they can modify the enzyme used by Sakai to make it more responsive and useful.
In this regard, Wu Bian's team at the Institute of Microbiology of the Chinese Academy of Sciences conducted research to optimize the enzymes required for Sakai bacteria to degrade PET plastics, and obtained a re-engineered enzyme with significantly enhanced stability, which increased the degradation efficiency of Sakai bacteria to PET films by 300 times. The research results were published in the January 2021 issue of the journal of the American Chemical Society Catalysis.
4, research and development of self-degradable plastics
The next level of strategy for degrading plastics is to develop and produce plastics that can degrade themselves, and in this regard, Chinese researchers have made some progress.
China South China University of Technology, China Guangdong Juyi New Materials Co., Ltd. and a Chilean company jointly developed to use polyvinyl alcohol as the main raw material of water-soluble shopping bags will be put into production into the market, China is responsible for the production of raw materials, provide technical support, the Chilean company is responsible for the product market and sales. In the future, the raw materials for shopping bags will continue to be the main production base in Qingyuan, Guangdong, and the shopping bags will be made in Chile or other places and sold to the world.
This water-soluble shopping bag has a high load-bearing capacity and cold water solubility, suitable for use in a water-free environment, and can "disappear" when it meets water after use, without pollution. A PVA water soluble bag, degradation only 5 minutes. This is obviously a breakthrough in the degradation of plastic bags, and the world, including China, has a number of universities and enterprises in the development of this technology, as for the actual application of the market, may still take some time.
In addition, there are some biodegradable plastics on the market, but in fact, the complete degradation is still not satisfactory, so the research and application of plastic degradation will be a continuous and major challenge for mankind.
Global plastic production since 2000 is equal to the total plastic production in all the years before 2000, and one-third of the plastic ends up in nature. In 2016 alone, about 100 million tons of plastic waste ended up in nature.
"Plastic not only pollutes ocean waterways and endangers aquatic life, it's in everyone's body." WWF Global Director General Marco Lambertini said that plastic pollution is an urgent global problem, and this finding should be taken seriously by governments around the world, and he urged governments, businesses and consumers to work together to develop international provisions to take measures to tackle plastic pollution at the source.
