Considering that the production of nitrogen as a fertiliser is an energy demanding and climate negative process and that phosphate is a limited resource on a global scale, the recycling of nutrients is strategic both from an environmental as well as a socioeconomic point of view. Nevertheless, in the Baltic Sea, mussel farming for nutrient recycling has not gone beyond the pilot stage yet. The main obstacle so far is the lack of economic incentives, which are necessary since no ‘income’ can be generated from nutrient harvesting

Most of the global mussel farming is intended to produce mussels for human consumption. The annual world production of mussels today exceeds 1.5 million tonnes, of which half is produced and consumed in Europe. Cultured mussels have a number of advantages over wild mussels. They do not touch the ocean bottom and are therefore free of the grid that often spoils the taste of wild mussels harvested from the ocean floor. Since they feed from the nutrient-rich water that surrounds them, they taste sweeter, are plumper, more tender, have thinner shells and yield a higher amount of meat.

The blue mussel has a high content of the essential sulphur-rich amino acids methionine, cysteine and lysine, which match the content in fishmeal. They can, when shells are included in the feed, also provide calcium carbonate. At the same time, mussels are an excellent high protein feed for poultry as well as in fish feed and have a fat content of about 8%. Since mussels are at the second step of the marine food chain, the use of mussels instead of fish for feed production also is of large ecological importance at a time when many fish stocks are overexploited on local, regional and global scales.

The nitrogen, phosphorus and potassium levels in mussel biomass make it suitable for use as a fertiliser for grain cultivation. The calcium-rich shells can be used added to farmland as soil enhancer, as they increase pH in acid soil, and contain a number of micro-nutrients such as selenium, copper and zinc Pulverised mussel shells used as soil amendment on farmland have given good results and are of special interest for organic farmers who cannot use commercial fertilisers. Studies have shown crop increases from 25%-50% compared to land that was not fertilised.