A bit of sugar to save the climate: scientists create degradable plastic

Many plastic products labelled as biodegradable are available on the market. However, what manufacturers don’t tell consumers is that they are only compostable under industrial conditions.

For instance, polylactic acid (PLA), a plastic which is derived from sugar cane or corn starch, has been in vogue for a few years. It’s been mooted as a popular alternative to plastics derived from crude oil products – as it is renewable and sustainable. 

While PLA is labelled as biodegradable, in reality it only degrades under industrial composting conditions of high temperature and humidity, unlikely to be achieved in domestic compost heaps. PLA also has limited degradability in natural environments, e.g. in soil or in seawater.

As the climate change debate heats up, people from all walks of life are concerned about plastic waste that overflows from landfills and pollutes rivers and oceans. 

PLA is used, a news release notes, “in everything from disposable cups and tea bags to 3D printing and packaging.”

Scientists at the UK-based University of Bath wanted to make plastics biodegradable in natural conditions, and they have come up with a method of making plastics break down using only UV (ultraviolet) light.

Researchers at Bath University’s Centre for Sustainable and Circular Technologies (CSCT) have figured out a way to make these plastics more degradable in the natural environment.

All they had to do to “tweak” the degradability of the plastic was to incorporate different amounts of sugar molecules into the polymer.

The scientists discovered that by adding as little as three percent sugar polymer units into PLA ended up making the plastic degrade by 40 percent within six hours of exposure to sunlight. They published their findings in Chemical Communications.

This is quite a positive development as the technology is compatible with existing plastic manufacturing processes – that means it has the potential to be tested and welcomed by the plastics industry.

The team says they hope their findings will be used in the future by the plastics industry to make more environmentally friendly plastic products by having them be more degradable.

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

“Most PLA plastics are made up of long polymer chains which can be difficult for water and enzymes to break down. Our research adds sugars into the polymer chains, linking everything together by bonds that can be broken using UV light,” he explains.

“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,” he adds.

“Previously scientists have looked at enhancing the degradability of PLA to water – hydrolysis - but this is the first time anyone has looked at using light.

“This strategy remains to be translated to real-life plastics objects and tested with sunlight, but we hope our 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.”