Megawatts with added mussels -- Exploiting saline synergies

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In a novel approach to exploiting synergies, the developers of two offshore wind stations at opposite ends of Europe are both integrating fish farming activities into their business models. Not only will this provide extra income, but it will also create a mutually beneficial dialogue with the fishing sector.

E-Connection, developer of the Q7-WP Dutch offshore project, is planning to farm mussel seed on the foundation monopiles of its proposed 120 MW development. Special "substrate" nets hanging from the 60, four-metre diameter piles could yield between 300,000 to 600,000 kilograms of mussel seed per year, calculates the Dutch renewable energy agency.

Tests to find the best design for attaching the nets to the piles, which will be manufactured this year, have been successfully concluded, reports E-Connection. Once the wind farm is operational, nets will be hung annually in April and retrieved in September, with the seed mussels being transferred and sown at mussel grounds in the Oosterschelde.

"Originally we had thought of wrapping the foundation piles in the nets as a way of keeping them clean, but we decided that the risk of the piles being damaged was too great, so we plan to hang the nets between the piles," says E-Connection's Mathieu Kortenoever.

A kilogram of seed mussels is worth EUR 1 and a single pile can yield around 5000 kilograms a year. Apart from this additional income stream, adding mussels to megawatts has significant environmental benefits, claims E-Connection. Should the Netherlands reach its targeted 6000 MW offshore capacity, E-Connection says that 15-30 million kilograms of seed mussels could be produced each year. In recent years some 40 million kilograms of seed mussels have annually been fished out of the environmentally sensitive wildlife preserve, the Waddensea. Relieving the pressure on the Waddensea would be good for the birds that live there and for mussel fishermen. It also helps sell offshore wind to the fishing sector, adds project manager Henk van den Boon.

Andalucian doubts

In Spain, the company behind the 200 MW Cape Trafalgar offshore project proposal wants to combine the development with fish farming and shellfish breeding facilities. The plan is to fit underwater cages around the turbines and to lease them out for fish breeding and rearing. While developer Energía Hidroeléctrica de Navarra (EHN) claims the project will provide work for 1325 people, the project is still facing fierce opposition by fishing collectives two years after its inception.

The proposal -- one of only two offshore projects clearly on the table for Spain -- earmarks an area of around 1600 hectares 12 kilometres off Cape Trafalgar near the Gibraltar straits. Local resistance to the project has been strong. Fishing collective protests have been joined by an attack from a local politician, who insists that the majority of citizens in the area are against the project. He claims that at least four tuna fishing businesses could be jeopardised by dredging activities. The politician's own party came out in support of "responsible offshore wind development," however, and the Andalucian branch of Spain's green party is also supportive, saying the project's negative environmental impact is "infinitely inferior to its environmental advantages."

With a water depth of just 20-30 metres, the Trafalgar site was chosen as one of the few Atlantic coast areas suitable for wind development. The only other serious offshore plan for Spain -- from Swiss and German developers Umweltkontor and NEK Umwelttechnik -- overlaps EHN's project.

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