Potential for land based red algae

Dulse, or Palmaria palmata in Latin, is a red algae that has a relatively high value compared to other macroalgae and is commonly used in food products.

Senior scientist Philip James and colleagues have investigated the necessary conditions to successfully produce dulse with good growth rates and nice colour in the discharge water from land-based salmon production using recirculated water systems (RAS).

− I think this could be a win-win for both salmon producers, new businesses and the environment, says James.

This is what the scientists have found

In the trial, discharge water from SalMar’s land-based facility was used to grow dulse. The research results show that:

• Dulse grew best on 50 percent discharge water from RAS from this facility. That is compared to seawater, 25 percent and 100 percent discharge water from RAS.
• Results show that a dilution rate of 50 percent gave the highest removal efficiency of ammonia and nitrate for this facility. However, for phosphate removal somewhere between 25 and 50 percent RAS water was most efficient.
• Dulse grew equally well in salinity ranging from brackish water to full seawater (equivalent to 10-32 grams salt per kg seawater).

Striking potential

The results show that for every kilo of fish feed used in RAS salmon farming, 257 grams of dulse could be produced. With Norway’s land-based salmon industry consuming around 100,000 tonnes of feed annually, the nutrients in discharge water could provide everything needed for a substantial seaweed industry.

“This underlines the potential for both macroalgae cultivation and utilising RAS nutrients in discharge water as a valuable resource” James says and underlines that challenges remain.

In follow up projects, the scientists will also be testing dulse grown in discharge water from RAS water for nutritional benefits as well as any potential harmful compounds.

The results are from the ValueSøl research project, supported by the Regional Research Fund ARCTIC (RFF). Nofima is working together with the Norwegian University of Life Sciences (NMBU) and SalMar as project partners.