Biodegradable plastic made from fisheries waste
Like most other commonly used types of plastic, polyurethane is typically made from non-renewable crude oil, and it takes centuries to break down when discarded. Now, however, scientists have created a biodegradable polyurethane-like polymer using fish waste.
Led by Prof. Francesca Kerton, a team at Canada's Memorial University of Newfoundland started with the heads, bones, skin and guts of farmed Atlantic salmon, after the fish had been filleted for seafood sales. Usually, such remains would either be composted or simply thrown away.
The scientists proceeded to extract fish oil from the waste, then added oxygen to that oil in order to create epoxide molecules, which are similar to those found in epoxy resin. Carbon dioxide was then used to link those molecules together, with some help from cashew-shell-derived nitrogen-containing compounds known as amines.
The resulting bioplastic was shown to start biodegrading soon after being immersed in water to which the enzyme lipase had been added – lipase breaks down fats such as those found in fish oil. Even when soaked in plain water, the plastic still quickly began showing signs of microbial growth which should lead to degradation.
Additionally, early tests indicate that the cashew-shell amines used in the production process could be replaced with more readily available, naturally occurring amino acids like histidine and asparagine.
"I find it interesting how we can make something useful, something that could even change the way plastics are made, from the garbage that people just throw out," says graduate student Mikhailey Wheeler, who is working with Kerton.
The research will be presented later this month via the online spring meeting of the American Chemical Society.