Professor Kjell Inge Reitan considers sugar kelp is promising as biofuel. (Photo: Research Council of Norway)
Fish farms' salmon waste could help cultivate shellfish, kelp
Tuesday, November 27, 2012, 00:50 (GMT + 9)
Norway’s aquaculture industry may be highly successful, but its dark side hides rampant coastal water pollution via waste from salmon production. Researchers say this waste is a valuable resource that should be used for new biological production, according to the Research Council of Norway.
In 2009, nearly 1.2 million tonnes of feed went to raise over 1 million tonnes of salmon and salmon trout at Norwegian fish farms. An extensive amount of the feed ended up in coastal waters in the form of respiratory products, faeces and uneaten feed; the value of these organic and inorganic nutrients currently fertilising the ocean is estimated at NOK 6 billion (EUR 816.4 million) annually.
The project “Integrated open seawater aquaculture, technology for sustainable culture of high productive areas (INTEGRATE)” explores whether these waste products can be employed as nutrients to farm kelp or mussels.
“The thinking is that integrated multi-trophic aquaculture (IMTA) will provide significant added value on investments in aquaculture,” explains Associate Professor Kjell Inge Reitan of the Norwegian University of Science and Technology (NTNU), head of the project, “while at the same time reducing potentially negative environmental impacts.”
Now, researchers at the research institute SINTEF have seen good growth of kelp and mussels grown near aquaculture facilities.
Kelp is adept at binding much of the inorganic nitrogen and phosphorous discharged by fish farms, and one of the country’s most common macroalgae species, Laminaria saccharina, or sugar kelp, is specially promising for use as a biofuel and feed additive and for extracting its chemicals. Reitan is collaborating with companies that wish to cultivate it for large-scale bioenergy production.
“Development in this area will need to be driven by players in bioenergy and feed production,” asserted Reitan. “I don’t believe the salmon farming industry will get involved in commercially cultivating kelp in the near future, even though integrated production would give the industry a greener profile and enhance sustainability.”
Researchers estimate the annual potential for IMTA-method kelp at 0.6 to 1.7 million tonnes in Norway and for mussels at 7,200 to 21,500 tonnes. This kind of cultivation would require 82-250 sqkm of marine land; roughly 14 million tonnes of aquatic plants are cultivated annually worldwide.
Kelp cultivation needs to be constant to be efficient, and researchers at SINTEF have managed year-round artificial cultivation of sugar kelp sporophytes (juvenile plants).
“This makes it possible to exploit the kelp’s strong growth potential when conditions are favourable,” said SINTEF Research Scientist Silje Forbord.
They estimate that using IMTA methods to use Norway’s salmon production waste nutrients, four times the current annual 3,000-5,000-ton harvest of farmed mussels could be achieved.
The Research Council’s research programme Aquaculture - An Industry in Growth (HAVBRUK) has launched a research project to find how to design and locate kelp and mussel farming facilities for optimal use of fish farms’ waste nutrients.
By Natalia Real