As wild fish stocks are depleted, fish farms are stepping in to address the global shortage of protein. Although aquaculture emits relatively few greenhouse gases, the industry still has a large environmental footprint. One major challenge is fish sludge, comprised of faeces and uneaten feed.

“We help to turn waste sludge into a circular economy benefit,” says Hallstein Baarset, Business Manager of Waister.

The sludge contains nutrients such as nitrogen and phosphorus, but much of this is released into the sea, wasting valuable resources and contaminating the marine environment.

“As aquaculture grows, it must become greener and pollute the local environment less. We need to restrict the negative environmental impact of side streams from the industry,” says Baarset.

Waister technology dries wet fish sludge from land-based aquaculture and turns it into a biofertiliser for grains, grass, vegetables, fruits, flowers and other crops. The technology is based on a patented, innovative combination of mechanical fluidisation and superheated steam, creating a compact and highly energy-efficient dryer.

“Fish sludge is difficult to deal with. Technology that works on other types of wet matter does not necessarily work well on fish sludge, and many drying solutions in Norway have failed when applied to aquaculture. Our technology has been developed with fish sludge in mind, and after extensive testing, we now have a well-functioning system,” says Baarset.

Waister promotes the circular economy of aquaculture by upcycling waste that would otherwise be discarded. The dry material produced from the fish sludge contains high levels of nitrogen and phosphorus, which make an excellent biofertiliser either alone or as an ingredient in a fertiliser mix. As a result, fish farms cause less environmental harm and encourage sustainable fertiliser solutions. They also improve their bottom line by turning waste into profit.

“Aquaculture is very good at producing proteins, but it also needs to be sustainable. Our technology helps to recycle the nutrients the industry doesn’t need. We are helping the industry to create a circular economy in reality, not just in theory,” says Baarset.

Aquaculture is the fastest growing food production sector, and fish farms will increasingly require solutions that improve resource utilisation and enhance profits. They will also be subject to more and more environmental regulations from national authorities and international bodies such as the UN Food and Agricultural Organization (FAO), which is calling for stricter control of the industry.

Established in 2012, Waister targets land-based, closed-containment system aquaculture, and closed systems at sea a promising new area of application. The company also has solutions for food waste and for brewer’s spent grain.

Today Waister has customers in Chile, Norway and Sweden, and the company is now ready to launch its technology on a larger scale worldwide.