Biodegradable plastic products are supposed to be good for the environment. However, since they are specifically made to degrade quickly, they cannot be recycled. With this in mind, scientists in New Zealand have created an innovative way to give them a second life, boosting their environmental credentials.
The research, published in Physics of Fluids, was carried out at New Zealand’s University of Canterbury, where scientists turned biodegradable cutlery into foam. These spoons, forks, and knives are made from PLA bioplastics and considered non-recyclable but can be safely composted after use. The team’s new method squeezes more out of the material before it’s discarded forever.
The novel treatment process involves placing biodegradable cutlery into a chamber filled with CO2. As they cranked up the pressure inside the chamber, the gas dissolved into the plastic. When the pressure was subsequently released, the CO2 expanded inside the cutlery, turning it into foam.
According to the Canterbury scientists, the process is like opening a soda can and releasing carbonation. Interestingly, the team discovered that they could tweak the process to alter the end product. For example, lower pressure in the chamber resulted in bulkier foams with plentiful air pockets.
Heon E. Park, an author of the study, said:
Tweaking temperature and pressure, there is a window where we can make good foams. It’s not that every temperature or every pressure works. We found what temperature or what pressure is the best to make those non-foamable plastics into foams.
Some possible applications for these bulky foams include flotation devices, such as buoys and wall insulation. Foam is an ideal endgame for recycled bioplastics because they don’t require great strength to serve their purpose most of the time, a characteristic that’s significantly compromised via the plastic recycling process. The scientists are optimistic that the technology could be applied to a broader range of materials. “We can expand foaming applications to a lot of plastics, not just this plastic,” said Park.
Biodegradable plastics can take months or even years to break down. Even once disintegrated, microplastics may persist in the environment, leaking into the soil, rivers, ponds, or the ocean. Nevertheless, the team is confident that their findings could help reduce the number of biodegradable plastics ending up in landfills.