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A Spoonful of Sugar Makes the PLA Biodegrade

Image courtesy of Alamy/Everyday Images spoonful of sugar
Biodegradable polymers are only truly compostable under industrial conditions. Scientists in the UK have found a way to make PLA break down by adding sugar to the polymer chain and exposing it to UV light.

Although it represents only a fraction of plastics consumption, poly(lactic acid), or PLA, is gaining traction as brand owners chase sustainability credentials. Created using lactic acid from the fermentation of sugars, PLA typically is described as biodegradable. And it is, technically speaking, but only under strict industrial composting conditions. While it may degrade in natural environments, the process can take many, many years. Fortunately, science marches on, and researchers in the UK have found a sweet spot for achieving biodegradability by adding sugar into the PLA chain.

Scientists at the Centre for Sustainable and Circular Technologies (CSCT) at the University of Bath have tweaked the degradability of PLA by incorporating different amounts of sugar molecules into the polymer. They found that adding as few as 3% sugar polymer units into PLA resulted in 40% degradation of the biopolymer within six hours of exposure to UV light.

The technology reportedly is compatible with existing plastic manufacturing processes, meaning it could potentially be tested and adopted quickly by the plastics industry, according to the researchers. A paper has been published in Chemical Communications.

“Lots of plastics are labelled as biodegradable, but unfortunately this is only true if you dispose of them in an industrial waste composter,” said Dr Antoine Buchard, Royal Society University Research Fellow and Reader in Polymer Chemistry at CSCT, who led the research. “If [you] put it into domestic compost heaps, it can last for years.

“Most PLA plastics are made up of long polymer chains, which can be difficult for water and enzymes to break down,” added Buchard. “Our research adds sugars into the polymer chains, linking everything together by bonds that can be broken using UV light. This weakens the plastic, breaking it down into smaller polymer chains that are then more sensitive to hydrolysis. This could make the plastic much more biodegradable in the natural environment, for example in the ocean or in a garden compost heap,” said Buchard.

In the past, scientists have experimented with hydrolysis as a means to enhance PLA degradability, but this is the first time anyone has enlisted light as an agent, according to the researchers.

It’s early days, and it remains to be seen if this research holds up outside the lab. But Buchard is hopeful that “technology could be used in the future to make plastics that are strong when you’re using them, but can break down easily when reuse and recycling are not possible anymore.”

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