Industrial processing of herring, shrimp and mussels takes vast amounts of water – which is then chucked out.

In fact, processing one ton of marinated herring takes about 7-8 000 litres of water, a mere drop in the proverbial ocean when you think that processing a ton of peeled shrimp takes about 50 000 litres...

All that water is used to boil shrimp or fillet, salt and marinate herring; so really, the industry carefully makes nutritious fish stock which it then pours down the drain. It could be used to feed fish – or people – as it is rich in proteins, peptides, fats and micronutrients. Pity to waste it, really.

Chalmers' Department of Biology and Biological Engineering started working on this, and the project on Extracting Novel Values from Aqueous Seafood Side Streams (NoVAqua) received financial support from Nordic Innovation. This project ended in 2018 but the research is continuing under the AquaStream project, funded by the European Maritime and Fisheries Fund. They quickly established that standard processing loses up to 15% of the protein contained in the fish, but by treating the waste water it is possible to recover up to 98% of the protein and 99% of those famous omega 3-rich fats we are always being told about. The end product is a semi-solid biomass (which salmon find quite delicious) and a nutrient-rich liquid (which speeds up the growth of microalgae).

Not bad for something which might otherwise make for very healthy rats as the waste water heads to sewage plants…