Resumen: The effluent discharged from Recirculating Aquaculture Systems (RAS) is rich in nutrients such as nitrogen and phosphorus. If not managed properly, it becomes a pollutant; treating it to meet discharge standards is often costly. A recent project by Norway’s Nofima Institute has reframed this effluent as a valuable resource, successfully using it to cultivate the high-value edible red algae Palmaria palmata (Dulse). This provides a novel approach for RAS to achieve “internal recycling” and added value.
Research Highlights: Scientists utilized effluent from a land-based salmon RAS to test its effects on red algae growth at different concentrations. The results revealed that a 50% mixture of RAS effluent and seawater yielded the optimal growth conditions for the red algae, while also achieving the highest removal efficiency for ammonium and nitrate. This finding identifies the ideal balance between nutrient supply from aquaculture wastewater and the algae’s growth tolerance.
Dual Value: Economic and Ecological
Clear Input-Output Ratio: The study indicates that, under experimental conditions, approximately 257 grams of fresh red algae can be produced for every 1 kilogram of fish feed consumed. This provides a direct basis for scaling a complementary algae production system.
High-Value Product: Palmaria palmata is highly regarded in Europe as a superfood, consumed directly in salads or as a seasoning. Its market price is significantly higher than that of conventional aquafeed ingredients.
Closed-Loop Environmental Benefit: The algae absorb nutrients, directly reducing the treatment load and cost associated with the effluent. Furthermore, their growth process sequesters carbon dioxide, thereby reducing the overall carbon footprint of the aquaculture system.
Model Comparison: Traditional Treatment vs. Resource Utilization
Industry Outlook: Norwegian researchers point out that, based solely on the Norwegian land-based salmon industry’s annual consumption of 100,000 tons of feed, the nutrients present in its effluent could sustain a substantial algae industry. This highlights significant potential: RAS facilities could potentially transform into “combined production centers for protein and high-value plants.”
Key Application Points for Farms:
Feasibility Analysis: Initially, test the specific nutrient content (e.g., nitrogen, phosphorus levels) of your own RAS effluent to assess its suitability for cultivating the target algae species.
Process Selection: Consider bioreactor technologies referenced in the research, such as “continuous culture” or “perfusion culture,” based on investment budget and desired level of automation.
Market First: Before investing in the technology, research the local or target market’s acceptance of edible algae and identify potential sales channels to ensure the economic viability of the project.
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