Waister transforms fish sludge into biofertiliser

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 substantial environmental footprint. One major challenge is valorisation of fish sludge, comprised of faeces and uneaten feed.

“We help to turn sludge from farming and processing of fish into a circular economy benefit,” says Hallstein Baarset, CEO 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 and closed-containment 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 mixing air with 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 production. 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.

Waister targets land-based, closed-containment system aquaculture, as well as closed systems at sea. The company is represented by distributors in Chile (Circular Solutions Chile), Italy (Feed From Food) and Australia (Smart Aqua). The longest running machine has more than 35 000 operating hours since 2021. Waister’s technology produces a dried biofertiliser compliant with local regulations for use in agriculture in its key markets, including Norway, Chile and Australia.

Waister has also customers in several European countries and is launching its technology in Africa, Asia and Oceania. In addition, the company supplies solutions for wet food waste, breweries, marine food producers and other businesses that generate organic waste.