Apr 23, 2021 07:00:00

A new biodegradable plastic is developed that can be composted in just a few days with just the addition of water and heat.

Biodegradable plastics are plastics that are decomposed to a level that does not adversely affect the environment by the action of microorganisms, and are expected to be a solution to the global plastic pollution problem. On the other hand, the biodegradable plastics that have been developed so far have problems such as not being sufficiently decomposed by general composting work, but a new research team at the University of California said, 'Add water and heat. We have developed a plastic that can be decomposed in just a few days by simply putting it in a composter (a device that composts kitchen waste).

Near-complete depolymerization of polyesters with nano-dispersed enzymes | Nature
https://www.nature.com/articles/s41586-021-03408-3

New process makes'biodegradable' plastics truly compostable | Berkeley News
https://news.berkeley.edu/2021/04/21/new-process-makes-biodegradable-plastics-truly-compostable/

Biodegradable plastic that can break down in your compost developed by scientists --ABC News
https://www.abc.net.au/news/science/2021-04-22/biodegradable-plastic-compost-enzymes-environment-soil-green/100082958

According to a 2015 study , most of the world's waste plastic is sent to landfills, with only 9% being recycled. Biodegradable plastics, which are decomposed to a level that does not adversely affect the environment with the help of microorganisms, are attracting attention as a method to solve the problem of such plastic waste, but there are also problems with this.

Common plastics are composed of polymers that are densely packed with molecules, and although they are highly durable, they cannot be decomposed by the penetration of water and soil microorganisms, and remain in the environment even after disposal. Biodegradable plastics are attracting attention as a material to solve this problem, but many can only be decomposed in industrial composting facilities that maintain tightly controlled temperatures and conditions and are simply dumped in soil or the ocean. If it is, it may cause environmental pollution equivalent to that of conventional plastics.

To solve this problem, a research team led by Ting Xu of the University of California has been looking for ways to use 'enzymes' to increase the biodegradability of plastics. The biodegradable plastic newly developed by Xu et al.'S research team 'decomposes the polymer into the entire resin beads of polycaprolactone (PCL) and polylactic acid (PLA), which are widely used as raw materials for biodegradable plastics. Disperse the enzyme. '

by Adam Lau / Berkeley Engineering

If the enzyme that decomposes the polymer is dispersed throughout the biodegradable plastic in advance, the decomposition will proceed even while it is being used for its intended purpose. So the research team decided to wrap the enzyme in a specially designed polymer called random heteropolymers (RHP) to embed nanoparticles throughout the resin beads without breaking down the plastic. In addition, since the effective enzyme is different between PCL and PLA, it is said that an enzyme called

lipase is used for PCL and proteinase K is used for PLA.

The enzyme covered with RHP does not change the properties of the plastic, and it seems that only water and a little heat are added to cause the deterioration of RHP. According to the research team, when composting newly developed biodegradable plastic with a small amount of tap water in a household composter, 98% of the plastic deteriorated and fell apart in just a few days. Enzymatic decomposition of plastic is said to be faster under the conditions of an industrial composting facility.

The photo below is the photo on the left immediately after putting the newly developed biodegradable plastic using PLA into the compost, and the photo on the right one week after putting it in the compost. You can see that PLA plastic is rapidly decomposed by the action of enzymes.

by by Adam Lau / Berkeley Engineering

Xu said the new approach of using RHP to disperse enzymes that break down plastics to create highly biodegradable products in a wide range of areas, from polyester clothing to electronic adhesives. Claims that it can be applied. “We want to work with the industry to move this forward and extend it to the top of grocery stores and countertops,” said Xu.