A cling film made from an invasive seaweed can withstand high temperatures yet is still easily compostable. The material could eventually become a sustainable choice for food packaging.
Large quantities of thin plastic films, like those for wrapping produce or baked goods, are used every year. Most end up as garbage, either because they require specialised recycling facilities or can鈥檛 be recycled at all. Some biodegradable plastics do exist, but they can take months or even years to decompose. at the University of Leeds in the UK and his colleagues wanted to create a thin plastic that can be easily composted instead.
They started with a brown seaweed called sargassum (Sargassum natans), an invasive species that inundates the shores of Trinidad and Tobago where Ward is from. Sargassum contains long, chain-like molecules similar to those that make up conventional plastic, which made it a good raw material. The researchers mixed it with some acids and salts to get a solution full of these molecules, then blended in chemicals that thickened it and made it more flexible and pliable.
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The team shaped this material into thin films, then tested how it held up when heated or thrown in the composting bin. The bioplastic could sustain heat up to 230掳C but in conditions like household composting bins over 90 per cent of it degraded in less than three weeks. For composting conditions like in industrial facilities the process took only 11 days 鈥� about a third as long as it takes the best existing biodegradable plastics to degrade, says Ward.
Additionally, when left in water for 10 days, the film didn鈥檛 leach out any chemicals, which implies that it could safely touch moist food, like cut fruits, for a few days, says at Imperial College London, part of the team. However, he says that they need to run more tests to see whether it could also be suitable for longer uses, like wrapping candies that can be stored for months.
at the Ohio State University says that making the new film in large quantities in industrial facilities may require tweaking its properties. In factories, plastics are turned into thin films by being blown into large bubbles first, so they must start off being very flexible. And starting with sustainable ingredients like overabundant seaweed may not be enough to make the final plastic product sustainable, says Vodovotz. Researchers must evaluate how much energy and water would be used during the production process if it were done in large quantities, she says.
鈥淪tudying the whole supply chain really is where ideas for sustainable materials make it or don鈥檛. We want to find one best application for our material and study the environmental impact of pursuing it from the lab to the consumer,鈥� says Lee.
The team presented the work at a meeting of the聽聽in Indianapolis, Indiana, on 26 March.
