This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Scientists have developed a way for certain types of compostable plastic to break down much faster in marine environments, from shallow coastal waters to the deep sea. The breakthrough comes from tiny enzymes embedded in the plastic that help degrade it from within.
As the name suggests, compostable plastics are a type of biodegradable plastic designed to decompose completely due to the action of microorganisms in a composting setting, such as an industrial composting facility. And although they degrade in compost, they can persist for a long time in cold marine environments. Every year, millions of tons of plastic end up in the ocean, where they can remain for decades and threaten marine life and ecosystems.
So to help tackle this problem, researchers led by Tadahisa Iwata at the University of Tokyo set out to make compostable plastics degrade rapidly in the sea without losing their strength during use. They published details of their research in the journal Nature. A Research Briefing in the same edition also summarizes the work.
The scientists took four types of compostable plastic (PBS, PBSA, PCL, and PBAT) and melted them down. Mixing enzymes into molten plastic is usually difficult because extreme heat destroys delicate proteins. However, the team solved this by using heat-stable, freeze-dried forms of Candida antarctica lipase B and Humicola insolens cutinase.
They then shaped these materials into films and microbeads to simulate plastic waste and microplastics ready for testing in real-world settings. To see whether they would degrade relatively quickly, the scientists deployed the samples in different marine locations, including shallow coastal waters and deep-sea floors. And they monitored them over periods ranging from one month to 18 months.
Overall, the results were promising, though they varied by polymer, enzyme and location. At 757 meters (2,483 feet) deep, films of three types of plastic containing 3% cutinase lost nearly all their mass within five months, while enzyme-free controls barely changed. Microbeads containing cutinase also showed signs of degradation at this depth.
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