Fish sludge is waste from fish farming, consisting of uneaten fish feed and faeces. The sludge contains important nutrients such as phosphorus and nitrogen, which are essential for all life on earth. However, fish sludge also contains polluting heavy metals such as zinc, nickel and cadmium.

The amount of fish waste is growing as the number of land-based and closed fish farming facilities increases. Much of the waste is disposed of at sea, causing eutrophication, among other problems, and wasting valuable nutrients.

In Norway alone, 27 000 metric tons of nitrogen and 9 000 tons of phosphorus are released from fish farms into the sea each year.

Bioretur’s sludge treatment plants clean, dewater and dry fish sludge on site, converting the sludge from 0.1 per cent dry matter to a highly potent powder (90 per cent dry matter).

Bioretur offers a unique service model as well. The Bioretur agreement encompasses leasing, remote operation and maintenance of sludge treatment plants, as well as transport, handling and processing of the waste into usable resources for soil improvement, fertiliser and biogas substrates.

Bioretur’s technology and services reduce the waste of valuable nutrients, keeping them in a circular ecosystem. The company’s solutions also reduce the use of chemical fertilisers and minimise marine pollution, while enabling fish farmers to shrink their carbon footprint.

The wastewater released from Bioretur’s installations is clean and the dry sludge collected is utilised in several different ways. These include local biogas production and a natural fertiliser called Minorga. Minorga is distributed in Vietnam where the farmlands contain very little phosphorus.

Bioretur is working to become the market leader in sludge treatment for land-based aquaculture. In 2018, 2 000 of the 18 000 fish farming licences awarded in Norway were for facilities on land.

Over the next 10 to 20 years, the Norwegian salmon farming market will grow as more and bigger fish will be farmed in land-based and closed facilities. Internationally, Bioretur expects growth in Canada, the US, Iceland, New Zealand, Scotland, Russia, Chile, and emerging markets.

Bioretur’s clients include aquaculture heavyweights such as Grieg Seafood, Mowi and Russian Aquaculture. Bioretur received the Sustainability Award at the 2019 Aquaculture Awards.