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Most compostable plastics, made primarily of the polyester known as polylactic acid (PLA), end up in landfills and last about as long as any other plastic. But University of California, Berkeley, scientists have now invented a way to make them break down more easily within a few weeks using just heat and water. The new process involves embedding polyester-eating enzymes in the plastic as it’s made. The enzymes are protected by a simple polymer wrapping. When exposed to heat and water, the enzyme releases the wrapping, starts breaking down the polymer into its building blocks—in the case of PLA, reducing it to lactic acid, which can feed the soil microbes in compost. The polymer wrapping also degrades.
“People are now prepared to move into biodegradable polymers for single-use plastics, but if it turns out that it creates more problems than it’s worth, then the policy might revert back,” said Ting Xu, UC Berkeley professor of materials science and engineering and of chemistry. “We are basically saying that we are on the right track. We can solve this continuing problem of single-use plastics not being biodegradable.” Xu is the senior author of a paper describing the process published in the journal Nature.
Xu said that programmed degradation could be the key to recycling many objects. Imagine, she said, using biodegradable glue to assemble computer circuits or even entire phones or electronics, then, when you’re done with them, dissolving the glue so that the devices fall apart, and all the pieces can be reused.
The work was funded primarily by the U.S. Department of Energy with assistance from the Army Research Office and UC Berkeley’s Bakar Fellowship program.