From the Baltic to the North Sea: Expanding WIN@sea Brings Seaweed Farming Closer to Local Fishermen

We’re building the knowledge base to potentially make multi-use the future standard for offshore energy developments across Europe

Demonstrating the potential of multi-use at sea

Launched in 2023 at Scandinavia’s largest offshore wind farm, Danish Kriegers Flak, the WIN@sea project is part of the EU-funded OLAMUR initiative. Although low salinity in the Baltic Sea has limited the seaweed yields, the project successfully showed how renewable energy operations could work alongside marine aquaculture, creating opportunities to reduce costs and emissions.

“From shared vessel operations to routine monitoring, our first season at Kriegers Flak demonstrated how effectively different marine sectors can collaborate,” says Annette Bruhn, senior researcher at Aarhus university and WIN@sea project leader. “While the harvest was modest, we gained valuable insights into operational efficiencies, reducing both the travel needs for aquaculture operations and associated emissions and costs for seaweed producers. This clearly indicates that multi-use offshore farming has promising potential.”

Even unexpected challenges, like vessel collisions with seaweed lines, became opportunities to test resourceful solutions. By integrating seaweed farm repairs into Vattenfall’s existing maintenance schedules, the project team efficiently redeployed cultivation lines, reducing costs and environmental impacts through fewer vessel movements.

Mussel farming can help filter the water

With low salinity conditions posing ongoing challenges for seaweed growth in the Baltic Sea, the WIN@sea partners are also looking at alternative or additional species that thrive under these conditions—particularly blue mussels, which offer similar regenerative benefits. Mussels can help filter excess nutrients from the water and improve overall water quality. By combining seaweed and mussel farming, the project aims to diversify production, strengthen ecosystem health, and uncover additional economic opportunities for local coastal communities.

Better harvests in the North Sea 

Building on the experiences from Kriegers Flak, WIN@sea has now expanded to the North Sea at Vesterhav Syd, Vattenfall’s newest offshore wind farm off Denmark’s west coast. Here, conditions differ significantly: the nutrient-rich, higher-salinity waters favour the growth of robust seaweed species, though strong currents and high wave present new operational challenges.

“At Vesterhav Syd, we’re growing sugar kelp, a seaweed species that thrives here,” explains Mads Hecter from Kerteminde Seafarm ,who has more than seven years of experience deploying and harvesting seaweed in Denmark. “But, this location demands robust equipment capable of withstanding winter storms and waves of up to seven metres. Despite this, our seaweed seedlings deployed in December are already growing well, reaching between five and ten centimetres at our latest inspection in early March. We anticipate our first North Sea harvest in April.”

By expanding offshore farming into the North Sea, WIN@sea highlights the transferability and scalability of multi-use offshore wind farms.

Growing enthusiasm among local fishermen

A particularly encouraging development at Vesterhav Syd is growing enthusiasm from local fishing communities. Recent discussions with fishermen have shown interest in the economic possibilities offered by multi-use projects.

“For fishermen, especially those with less activity during winter, multi-use offshore farms offer promising new economic opportunities and utilization of the fishing vessels,” says Torben Lindberg Strømgaard, Business Development Manager at Port of Hvide Sande, where Vattenfall has its local operations. “Some fishermen are keen to become involved in the Vesterhav seaweed project and the WIN@sea project team has been very open to share their knowledge and experience with the local fishing community. 

“Together, we are exploring exciting possibilities, such as supplying high-end restaurants focused on products derived from offshore seaweed farming at Vesterhav. From our perspective, multi-use offshore farms have the future perspective of being an important driver for developing the fishing industry and creating new jobs, both offshore and onshore.”

Beyond energy: environmental restoration potential

WIN@sea extends beyond renewable energy production and sustainable food cultivation. Offshore seaweed – or mussel - farming, also known as regenerative ocean farming, can positively influence marine environments by absorbing excess nutrients from the water, potentially helping to improve water quality. 

“Multi-use offshore farming is not only a promising business concept; it may also contribute positively to marine ecosystems,” emphasises Vattenfall Bioscience expert Tim Wilms. “Healthier water conditions could encourage marine biodiversity recovery, helping to restore marine habitats.”

A vision for Europe’s sustainable offshore future

Ultimately, WIN@sea seeks to create a model for integrating marine aquaculture with offshore wind energy across North European waters, aiming to reduce spatial conflicts between maritime sectors and support ambitious nature goals.

“Our ambition with WIN@sea is to help demonstrate how offshore wind farms could evolve into hubs supporting multiple sustainable industries,” concludes Tim Wilms. “With each new harvest, innovative solution, and local partnership, we’re building the knowledge base to potentially make multi-use the future standard for offshore energy developments across Europe.”