Breaking Down Biodegradable Plastics? Just Add Heat and Water

Scientists have invented a process that breaks down compostable plastics in weeks.
Derya Ozdemir
Breaking down plasticsChristopher DelRe, UC Berkeley

Humanity has an ever-growing plastic problem, and while biodegradable and compostable plastics have been hailed as a solution, they couldn't live up to the hype since they require specific processes to break down. Now, scientists from the University of California, Berkeley have come up with a way of making compostable plastics break down more easily using just heat and water, according to a study published in Nature.

The process takes just a few weeks and has the potential to solve a problem that has created a headache for recyclers for many years since most compostable plastics, which are made mostly of polyester known as polylactic acid (PCL), end up in landfills and last as long as normal plastics.  

How?

Scientists embedded special molecules, which are enzymes that have the ability to degrade the plastic and turn it into lactic acid under specific conditions, in plastic made of PCL, per a press release.

Enveloped in polymers, the enzymes are placed inside the plastic fibers, and when exposed to water and heat, the magic, specifically the breaking down of the plastic, happens. 

"If you have the enzyme only on the surface of the plastic, it would just etch down very slowly," said Ting Xu, UC Berkeley professor of materials science and engineering and of chemistry and senior author. "You want it distributed nanoscopically everywhere so that, essentially, each of them just needs to eat away their polymer neighbors, and then the whole material disintegrates."

During experiments, the team was able to get their special PLA to degrade with six days at 122°F (50°C). The PCL degraded within six days at 104°F (40°C).

The greatest thing about this method is that it can biodegrade up to 98 percent of the plastic into small molecules without leaving behind any microplastics. 

However, does this mean your favorite pieces of clothing made of this material could vanish when they touch water like what happened to that raccoon who washed its cotton candy before eating it?  Well, no. According to the team, the modified polyester doesn’t degrade at low temperatures or during brief periods of dampness. As long as you wash it at a cool temperature, it wouldn't be a problem. Of course, sweating isn't a problem either. 

Plastic, recycling, and the future

 "These results provide a foundation for the rational design of polymeric materials that could degrade over relatively short timescales, which could provide significant advantages for Army logistics related to waste management," explained Stephanie McElhinny, Ph.D., program manager with the Army Research Office.

"More broadly, these results provide insight into strategies for the incorporation of active biomolecules into solid-state materials, which could have implications for a variety of future Army capabilities, including sensing, decontamination, and self-healing materials."

This process of programmed degradation could pave the way for recycling many objects smartly. The team is now investigating how they can apply this method to other types of plastic. If they also gain control on the level of biodegradability, this could enable them to partly biodegrade the plastic and then recycle the rest into new plastic.

"It is good for millennials to think about this and start a conversation that will change the way we interface with Earth," said Xu. "Look at all the wasted stuff we throw away: clothing, shoes, electronics like cellphones, and computers. We are taking things from the earth at a faster rate than we can return them. Don't go back to Earth to mine for these materials, but mine whatever you have, and then convert it to something else."

On the road to get rid of our plastic problem, this is only one of the advances that engineers and scientists are working on. Recently, construction has begun on the world’s first commercial-scale plant to use a new process that can recycle all forms of plastic waste.

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