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Can microalgae from Brazil make salmon farming sustainable?

Large areas of the Brazilian Amazon rainforest has been cleared for cultivation to meet the rising demand for soybeans in feed production. Picture: Wikimedia Commons

Large areas of the Brazilian Amazon rainforest has been cleared for cultivation to meet the rising demand for soybeans in feed production. Picture: Wikimedia Commons

MICROALGAE - Brazil is one of the most relevant countries to produce microalgae as an alternative to soy in fish feed.

Pål Myhre

The global production of salmon feed is currently at 3.506 million tons. Originally salmon feed consisted mostly of fish meal and fish oil, but gradually, in the absence of fishmeal more and more soybean meal has been added. Now soybean products, with their 649,000 tons (18.5%), are making the largest proportion of the feed and to produce the rising demand for soybeans, large areas of the Brazilian Amazon rainforest has been cleared for cultivation.

Meanwhile, Brazil has, with its 8.400 km long coastline and 16,500 hectares of constructed shrimp farms, achieved great development in its shrimp farming industry during the past 15 years. Normally, the cultivation water of the shrimp farm is full of microalgae (phytoplankton) from which have been inoculated and cultivated prior to the ingression of the shrimp post larvae, and up to 50 % of the shrimp feed requirement could be covered by this microalgae bloom. In other words, there are already large-scale production of algae along the Brazilian coast.

Aurora Algae, one of the key players who bet on large-scale production of omega -3 fatty acid EPA from microalgae Nannochloropsis oculata in Australia, has pointed to Brazil as one of the most relevant countries to produce microalgae, due to the favorable climatic conditions and the immense land availability. Based on the calculations of one of the most recognized algae scientists, Mario R. Tredici at University of Florence, a large-scale cultivation of Nannochloropsis oculata could annually yield up to 30 tons of omega -3 - rich algal oil per hectare. If Brazil adopts its vast potential of 300,000 hectare, nearly 9 million tons of algal oil could be produced, and not to forget the 9 million ton protein fraction that remains after the oil is extracted from the algae biomass which can replace soybean products in salmon feed.

SINTEF has discovered that up to 6% untreated algal biomass can be mixed into salmon feed without compromising growth and digestion of salmon. Even as much as a 12% mixture showed no negative effects on the intestine morphology. A further mixing is likely to require a treatment of algal biomass similar to that made with soy to make it more digestible for the salmon.

Now is the time to intensify the production of algal biomass up the Brazilian coast where conditions are favorable for development on a large scale, nor let the Amazon rainforest take care of its important contribution to the CO2 balance, while algae farms along the coast can absorb huge amounts of CO2 in the production of salmon feed and raw materials for the omega -3 industry.

Then we can hand on heart say that salmon farming has indeed become sustainable again.

Pål Myhre Marine - Design AS - pm@marinedesign.no