A sustainable approach to the production of farmed seaweed as a source of vegetable protein is being developed in Sweden. The use of food processing industry wastewater as fertilizer can increase the protein content of seaweed, accelerate crop growth and help form a circular food chain for land-based cultivation of this marine crop.

Researchers from University of Gothenburg and Chalmers University of Technology collected wastewater from a salmon farm, a herring processing facility, a shellfish processing plant and an oat milk manufacturing factory. The growth rate and crude protein content of brown kelp and three green seaweed species were determined eight days after the nutrient-rich process wastewaters were added to cultivation systems.

The growth rate and protein content of all four seaweed types increased on exposure to the four process wastewaters, which exerted no detrimental impact on the taste of the plants. Growth rates increased 60% on average and protein content quadrupled.

The study published in Algal Research demonstrates that the seaweed species tested are promising candidates for cultivation in process waters from different food industries, and that use of such wastewater could broaden opportunities for a new circular production route of vegan protein. The costly disposal of food production process waters can be turned into economic revenue by sustainably producing new protein-enriched raw materials via seaweed cultivation.

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