Woman with read hair wearing protective eye wear and a white lab coat and blue gloves. She is smiling and holding up a red fragment of plastic in one hand.Polyurethane plastics produced from crude oil are ubiquitous – appearing in foam furniture, kitchen sponges, car dashboards, freezers and refrigerators. But crude oil-derived plastics produce toxic by-products during synthesis and are slow to break down in the environment. Now though, researchers at Memorial University in Newfoundland have demonstrated proof of concept for a polyurethane produced using fish heads, bones, skin and guts —parts usually discarded from fisheries and aquaculture industries. The material produced is an orangey-red hued, slightly stretchy plastic.

Green chemist Francesca Kerton, who presented a summary of the fish-waste-to-plastic process with her graduate student Mikhailey Wheeler at the spring meeting of the American Chemical Society (ACS) in April 2021, also co-authored a 2020 paper about the work in Macromolecular Rapid Communications with co-authors Courtney Laprise, Kelly Hawboldt and Christopher Kozak.

Kerton’s interest in fish-based polyurethane stems from a recognition that as aquaculture expands in Newfoundland, so does its waste production. Fish oil extracted from such waste is not typically of nutraceutical grade, so Kerton was curious to investigate its use to create a new polymer.

At the ACS meeting, Kerton described the three steps of the polyurethane production. First, they add hydrogen peroxide to fish oil extracted from Atlantic salmon waste. “This oxidizes the fish oil,” says Kerton. Next, they add carbon dioxide. Finally, they react it with an amine – a nitrogen-containing molecule — which produces the nonisocyanate polyurethane. Their proof-of-concept polyurethane incorporated amines derived from commercially available cashew nut shell waste. Kerton and her students are now screening the utility of alternate amines, including asparagine and histidine.

Their product, Kerton suggests, may one day be used for food wrap or wound dressings. Toxicology and safety testing are yet to come, Kerton notes. Given that some components – fish by-products and cashew nut shells – are linked to allergies in some individuals, this is a safety issue to be studied if the work proceeds to commercial production.

To study the product’s ability to degrade, the team used an electron microscope to examine its surface under various conditions. By adding the enzyme lipase to the material placed in a water solution, degradation dramatically accelerated, as evidenced by large and small cracks that emerged on the surface and the presence of fungi and bacteria, suggesting greater degradability than petroleum-based polyurethane.

The extent to which its degraded pieces are environmentally preferable to microplastics from petroleum-derived polyurethane awaits testing. “We imagine that the polymers break down to fatty acids and other products in the presence of appropriate enzymes – however, we do need to perform these experiments,” says Kerton.

How does its chemical structure compare with that of polyurethane made from petroleum? Many petroleum-based polyurethanes have aromatic groups in their backbone, such as benzene rings. “This gives them a certain amount of rigidity that our material just wouldn’t have because of the nature of the building blocks,” says Kerton. Nevertheless, she added, “compared to some polyurethanes, our materials will be less hard or tough, but at the same time, more stretchable,” describing its flexibility as beneficial for use in applications where we currently use plastic cling-film (Saran wrap).

Theirs is not the first effort to use fish waste to produce plastics. In 2019, University of Sussex, UK, design student Lucy Hughes made a clear biodegradable plastic called MarinaTex from fish waste and red algae, winning the James Dyson award for her work. And at the Universiti Sains Malaysia, Ku Marsilla Ku Ishak, a lecturer from the Polymer Program at the School of Materials and Mineral Resources Engineering, has also developed a bioplastic from proteins in fish waste for use as an alternative to single-use products like planting pots and seedling trays.

“Plastic from fish waste is very likely to get into [the] market,” says Ku Marsilla, noting that many existing products are produced from fish waste, including fish oil, collagen and gelatin. “Research-wise, it is all there,” she says. The challenge, she explains, is the cost of scaling up.

“There’s a lot of negativity out there surrounding plastics,” says Kerton. “Not all plastics are bad. They’re really useful in many applications, and they make our lives better. But I think as scientists, it’s good to take some responsibility and plan for the future.”

“We are able to make a plastic fully biosourced, which makes it better for the environment,” Wheeler says. If all goes well and they attract investment, the team hopes to have pilot plants in two to three years and a product on the market in the next five.