Waste not, want not from the seafood industry

How fisheries and aquaculture can cater for change by putting waste to better use

Waste. It's everywhere, even with our seafood.  

One person's trash is another person's treasure, as the old proverb goes. Whether dealing with inedible or less appetising parts of seafood, small business owners, conservation organisations, researchers, and communities are showing that seafood waste doesn't have to be wasteful. 

Healthy treats for hungry pups

When COVID-19 sent Lisbon into lockdown in 2020, Daria Demidenko found herself at home with her two dogs for months. "I was training my dogs a lot and started to look for healthy options to give them as treats," she says. The options, she notes, were slim, which is why she set about learning to make some herself. The key ingredient? Fish waste from a local sushi bar.  

"I was given fish heads, skin, bones, and other parts of the fish that are discarded," Demidenko explains. With some boiling and crushing, and the addition of flour and other ingredients such as chia seeds, Demidenko created dog biscuits. Next, she learned to dehydrate skins to make chips. Then she started Sancho Pancho, a business dedicated to using food waste to create healthy treats for dogs and cats.  

One of the challenges Demidenko now faces is ensuring a steady supply of ingredients in sufficient quantities to keep up with demand. Alongside restaurants, she also looks for partners in fish markets. However, not every business producing food waste has the capacity to process it for reuse. "It's pretty hard to make a deal with restaurants because they don't have a person assigned to sort the food waste, and they don't have storage for it," she explains.

Salmon skin is dehydrated and used as pet treats  (Credit: Daria Demidenko) 

A restoration for success

Over in Hong Kong, Anniqa Law from The Nature Conservancy (TNC) echoes Demidenko's words. "It's extra work for the frontline workers, not only the waiter or waitress but also the dishwashers and chefs," she says. TNC is targeting a specific kind of seafood waste in Hong Kong. Oyster shells.  

"Oysters are what we call a foundational species, creating a habitat for hundreds to thousands of other species," Dr Bayden Russell of the University of Hong Kong explains. Oysters historically formed enormous reefs throughout the region. However, intensive fishing and development destroyed most of them. "Once you lose the physical structure of the oyster reef, you have nowhere for any new baby oysters to settle, so the reef cannot reform," he says.  

Bayden and TNC are partnering with restaurants, aquaculturalists, and local communities to rebuild the reefs with discarded oyster shells. 

Getting shells from plate to reef is a long process. The shells are cleaned and transported to a shell recycling farm, where the shells are left out in the sun for six months to a year. "We need the sun and UV light to kill pathogens and diseases on the shells, so we don't introduce them to our reef," Law explains. Volunteers then place the shells in hemp mesh bags which, alongside live oysters and limestone, are put in the water. 

The team created their first reef next to one of Hong Kong Airport's runways a year ago. Already, the signs are promising. "We've had oyster recruitment, small crustaceans, bivalves, gastropods, fish, and fish eggs…it's just this little ecosystem being built," says Russell. 

Rebuilding the reefs with discarded oyster shells (Credit: Frigatefilms) 

Two-seeing approach

Over in Newfoundland, Canada, a new six-year project seeks to build seafood waste reuse from the ground up. "Around 30-70 weight percent of the landed harvest is wasted. We want to reduce that and put that value back into the local communities," says Memorial University's Dr Kelly Hawboldt. 

The project takes a two-seeing eye approach, "where you look with both a western scientific and Indigenous perspective," explains Hawboldt. "I'm a chemical engineer, so I'm looking at the process of transforming the waste into a product. Working with the Indigenous people, we trade knowledge. You actually get feedback and make a product that's more tangible than if you're just sitting working in a lab," she says.  

The team of researchers and Indigenous partners will explore what has traditionally been done and what could be done in Newfoundland's small coastal communities. There are many aspects to consider. Some are logistical, like getting waste from small fishing boats, which often discard unwanted parts of their catch at sea to save space. Then there are the products themselves, which can include fertilisers, nutraceuticals, and medicinal agents.  

"The processes [to create different products] vary in complexity," says Hawboldt. These can range from grinding shells, which can be done locally, to more complex processes such as extracting lipids from shrimp shells, which may need to be done at regional facilities. "We'll be working closely with our Indigenous partners to make sure that we're addressing needs and wants," says Hawboldt. 

Dr Sam Andrews is a marine ecologist and science writer