News & Views
SINTEF research to explore sustainability potential of sludge from salmon hatcheries

Fish feces and residual feed recovered from salmon hatcheries may soon become a sustainable product. 

Salmon smolt is typically produced in flowthrough hatcheries where the water flows through the hatchery tanks without being reused or recirculated. However, most hatcheries in Norway today recirculate and decontaminate their water. Fish feces and residual feed particles are filtered from the output water to form sludge, according to an article by Norwegian SciTech News.

Currently, fish farmers have to pay to have this sludge removed. But soon, according to Dagens Næringsliv, materials contained in the sludge may become a resource that future biomarine businesses could purchase. The sludge may be used as a substrate for the cultivation and rearing of plants and other organisms such as bristle worms which can replace current salmon feed ingredients.

The practice of sludge-based rearing of bristle worms for salmon feed has not begun because there’s uncertainty about the transfer of microorganisms from the sludge into the food chain.

SINTEF, together with the Norwegian Veterinary Institute and the Institute of Marine Research, is currently in the middle of a research project looking into the issue and has yet to identify a bristle worm containing either a bacterium or a virus after eating sludge to which the organisms have been added. 

“If future research gives us the evidence we need to declare bristle worms as risk-free, these annelids may become Norway’s next mass-produced feed organism,” the article from Norwegian SciTech News states.

Sludge recovered from hatcheries is currently used as compost, in manufacturing fertilizers, improving soils and generating biogas. The sludge may be a source of revenue. “This is because of the forecast ‘feed squeeze’ that is now threatening Norway’s plans to increase its future salmon production by four- to five-fold,” Norwegian SciTech News states. 

If sludge generated by the farmed salmon sector can be safely exploited, it could be an important step along the road toward a circular bioeconomy in Norway.