Dutch seaweed farmers complete world’s first offshore mechanical harvest

Feat marks first step towards large-scale development of commercial seaweed farms in North Sea, says farmers’ group

Dutch seaweed farmers have just completed the world’s first offshore mechanical harvest – marking the start of a dramatic expansion that could see 400sq km of territorial waters set aside by the government, with substantial funding from the European Union.

The aim of the expansion is to challenge the dominance of China and Indonesia in a global market worth €13.5 billion a year, according to the business magazine Fortune; Europe’s current production of 287,033 tonnes represents only 0.8 percent of the worldwide total.

An indication of the potential in this fledgling European market is that the seaweed farmers’ umbrella group, North Sea Farmers, which has about 100 members, has already been joined by Dutch corporate giants, Unilever and Shell, which aim to help turbocharge production over the next decade.

The current site is located about 12km off the Dutch coast, where the farmers have been test-growing kelp on 2m-wide nets hanging below a 50m-long plastic tube floating on the water’s surface, held in place by two anchors and two marker buoys.


For their first mechanical harvest, the fishermen used a converted trawler with an 8m-high electric cutting arm attached. The arm sliced the seaweed from beneath the tubing and dropped it, already bagged in 2m lengths, on to the trawler’s deck.

“This harvest was the all-important first step towards the large-scale development of commercial seaweed farms in the North Sea,” says Eef Brouwers, farming and technology manager at North Sea Farmers.

Financial support for such projects from the EU amounted to €273 million last year and is expected to keep rising.

Apart from the fact that it doesn’t need land, fresh water or fertiliser to grow, seaweed – actually an umbrella term for a group of multi-cellular, macroscopic, marine algae found in various shades of brown, green and red – has myriad uses.

It’s found extensively in the food and beverages industry, in cosmetics, animal feed, agriculture and pharmaceuticals, which explains the interest of large corporate investors.

There are, however, environmental concerns, says Reinier Nauta of Wageningen University in the Netherlands, who says the most compelling are over the nutrient balance of the sea.

The greatest risk is that farming seaweed at scale could cause phytoplankton populations to crash, he warns.

And since these are the building blocks of the marine chain, a decline could be “disastrous’” for fish, seals and porpoises further up the food chain.

Peter Cluskey

Peter Cluskey

Peter Cluskey is a journalist and broadcaster based in The Hague, where he covers Dutch news and politics plus the work of organisations such as the International Criminal Court