Bioremediation with aquatic biomass

The SUBMARINER Network has identified mussel and macroalgae cultivation and harvest as possible routes to realising two of its visions for 2030: marine resources as a part of the Baltic Sea Region sustainable energy and biomass portfolio and maintaining the Baltic Sea Region’s natural capital. Mussel and algae cultivation not only alleviate eutrophication in the Baltic Sea by taking up nutrients, they are also excellent substitutes for human food and animal feed. Around the Baltic Sea, innovative projects are being implemented, where aquatic biomass play an important role in remediating eutrophication – both off and on land.

Mussel farming in Sankt Anna, Sweden

Taking his boat out to the islands and waters of the Swedish east coast archipelago, the fisherman and entrepreneur Mats Emilsson notices dramatic changes in the Baltic Sea environment. Growing up as the 10th generation on the island Vänsö, Mats is very familiar his home environment and is well aware of the rapid decline of the water quality or how the sea bird population has decreased with 70% over the last 30 years.

When the Country Administrative Board in Östergötland approached Mats about establishing a mussel farm to improve water quality, he didn’t hesitate to say yes. Mussels act as natural filters by feeding on phytoplankton, effectively removing nutrients from the water body. Together with land-based measures, mussels can become one important factor in alleviating eutrophication in the Baltic Sea.

Finding the right location is key to successful mussel farming. Mats used his extensive knowledge of the local ecosystem to choose the appropriate bay, tools and ropes for the mussel farm. It paid off - over the last two years, mussels have thriving on their longline in the bay. With two months left until harvest, one meter rope is home to about 2 kg of mussels. Considering that there are 24.000 m of rope, that adds up to about 48 tons of mussels.  

To Mats, mussel farming is first and foremost a job. Living in the archipelago means having to be flexible to support oneself, now that the fishing industry is almost gone, islanders make a living through tourism. Most, however, move to the mainland to look for a job. Mussel farming could be an opportunity for more people to stay in the archipelago, after all, knowledge and experience is plentiful.  

Mussel farms are not yet economically viable, but Mats hopes that the state will provide some kind of compensation for the ecosystem service that mussels provide. One simple solution could be the state subsidising mussel meal as animal feed by paying the difference in price to conventional feed. Sustainable sea activities, practiced by the archipelago inhabitants for hundreds of years could continue on to the next generation.

Seaweed turned into animal feed - an advantage for both beach-lover and farmer

For most beach-lovers, seaweed represents a foul-smelling annoyance rather than an opportunity to reduce negative environmental impacts in the sea. Located along the coast of south Zealand, Guldborgsund municipality has a particularly prominent seaweed problem. Each year tons of seaweed are washed on to its 328-kilometre-long shoreline, a popular destination for locals and tourists alike, costing the municipality money and resources to clear away.

Looking for way to create an opportunity out of a challenge, Anne Holl Hansen of Bio-economic Hotspot Guldborgsund developed, together with Danish Technological Institute (DTI), the bio-economy concept “BIOFISK – bioeconomy in organic feed innovation for beach municipalities”. Beach-cast seaweed, collected from the beach is being analysed for its potential as a feed component, to be used as feed for insects (Black Soldier Fly larvae) or for adding directly into a feed.  The fully grown, well-fed larvae will be turned into high-quality and sustainable animal feed for the aqua/agricultural sector (or possibly even other products, such as glue!), potentially providing a local product to replace part of the large quantities of soy and maize protein imported from South America by Danish farmers.  To implement such a project on full scale, BIOFISK aims to attract investors and producers in the feed industry to invest in sustainable feed proteins originating from beach-cast seaweed, such as larvae.

If fully implemented, BIOFISK will do both the municipality and the environment a favour. Beachgoers will be able to enjoy a day on the beach without being accompanied by the foul smell of rotting seaweed and farmers can reduce their imports of feed, as well as their environmental footprint.

BIOFISK also illustrates the synergies between blue bioeconomy and agriculture. Just like mussels, seaweed extracts nutrients from the sea and provides a nutritional base for future feed.

Pigs and microalgae working in symbiosis

Another project illustrating the symbiosis between bioremediation and aquaculture was the Danish project Grønne Grise (Green Pigs), funded by Grønt Udviklings- og Demonstrationsprogram (GUDP) under The Danish Agricultural Agency, Foreningen Plan Danmark and Green Center in Holeby. Denmark is a world leader in pork production, and with it comes high levels of emissions. By cultivating microalgae in the emitted nutrients, the project demonstrated that it is possible to produce algae biomass with a very high protein content of up to more than 55%.

By upscaling the results from the project to one hectare, it will be possible to produce about 40 tons of protein rich algae biomass, while reducing the emissions with 70 tons CO2 and more than 3 tons nitrogen. This way is can be possible to reduce the environmental impact of the pork production and control the amount of emissions from the production. Not only do algae take up nutrients and reduce emissions, a large-scale cultivation would reduce Denmark’s reliance on imported soy protein.  

These three cases have shown us how sea-based measures can improve the environmental status of the Baltic Sea as well as its coastal environment. For more such innovative and sustainable initiatives to happen, stakeholders, in particular, sea-farmers, need an incentive to carry on after project funding has run out. After all, bioremediation through aquatic biomass such as mussels, seaweed and algae will play an important role in improving both the health of the Baltic Sea and the regional economy.


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