Valorization of aquaculture residues

The demand of sea food is increasing around the world. Seafood provides a number of substantial and valuable nutrition compounds and helps to secure high quality food supply to humans. Nowadays, aquaculture is seen as a strategy to serve the demand of fish while saving resources in open ecosystems. These concepts, however, have an outflow of unused nutrients and excrements, which can assimilated by microbes. This is performed, in case of solid waste streams, in an acid (dark) fermentation. Short carboxylic acids (products of the dark fermentation) are used together with liquid waste streams as effluents in heterotrophic algae cultivations. The final product of this is docosahexaenoic acid, which is a nutrient compound in fish feed, which is usually gained from fish oil and fish meal, along with a high environmental burden.
By this concept, the nutrient circle will be closed to an extent, which was never achieved so far in any aquaculture concept. Emmissions are reduced vastly, while a substitute for fish oil as value-added product is provided. A similar concept is appplied to phopshor and nitrogen: bioaugmented species accumulate these components. By using these microbes directly in fish feed or in a fertilizing broth, regional circles including the aquaculture can be closed.