Photo: DTU Fødevareinstituttet

Surplus mussles turned into sustainable feed

Wednesday 18 Jul 18


Nina Gringer
Associate Professor
National Food Institute
+45 45 25 66 24

Mussles that are too small to sell as food for humans are turned into sustainable, organic animal feed in a project at the National Food Institute, Technical University of Denmark.

From the start of 2019, EU regulations will require that farmers use only organic feed in the production of organic livestock. However, it is not possible for Denmark to produce the quantity of food needed by the country’s organic livestock producers, unless new types of feed can be identified.

Researchers from the National Food Institute have been studying ways of turning mussels, which are too small to sell as food for human consumption, into a financially viable, sustainable, organic ingredient in chicken and pig feed 

New production lines

The traditional method for processing mussels for human consumption is expensive and time consuming. In this method, the mussels are harvested, boiled and shelled, other species—such as starfish and crustaceans—are removed and the boiled mussels are processed.

The National Food Institute’s researchers have therefore been working to develop a new production line for feed production, which leaves out the expensive cooking process and the time consuming sorting process.

After experimenting with meat grinders, juicers and various equipment from the institute’s testing facilities, the researchers have identified the most promising method. It involves putting the mussels—including the calcium rich shells and any nutritious bycatch—through a meat grinder and then a compact filter, which separates the mass into a liquid fraction and a solid substance. The liquid is then spray dried into a flour, which is mixed with the feed. 

Calculating the financial viability

The method has produced promising results, but the researchers continue working to identify improvements that can increase the amount of liquid, which is separated from the raw material, e.g. by using a different roller in the contact filter.

The institute’s researchers are also studying the nutrient content of the flour, as the price of feed ingredients is dependent on the nutrient content. Results from the analysis as well as experiments to extract more liquid will be used to calculate whether it is financially viable to produce the mussel flour.

The National Food Institute’s collaboration partners at Aarhus University are looking into whether the flour can replace traditional protein sources in chicken and pig feed, and how nutrients in the feed may affect the health of the animals and the quality of the eggs.

Read more

The National Food Institute’s work is part of the research project MuMiPro, which is headed by DTU Aqua. Apart from creating a new, organic feed source from a sustainable raw material, the aim of MuMiPro is to improve the water quality in Limfjorden  by growing mussels that remove nitrogen from the water.

MuMiPro supports the UN’s Development Goal aimed at increasing sustainable production patterns.

In its work package, the National Food Institute works with the Norwegian research institute Nofima, as well as the Danish companies Engredo and Vilsund Blue. Read more on MuMiPro’s website.


During the experiments the National Food Institute has processed four tonnes of mussels that were grown in Limfjorden.

Some of the mussels were the size of a sunflower seed, while others were up to four centimetres long. Mussels have to be at least 4.5 centimetres long to be eligible for human consumption.