Seaweed farming for profit

Published on
August 17, 2011

Of the many aquaculture discussions that take place on SeafoodSource, there is rarely any mention of the second largest aquaculture industry in the world — seaweed. With a global production of 17.3 million metric tons, seaweed aquaculture is second only in volume to the farming of freshwater fish. The vast majority is grown in Asia, which accounts for 17.1 million metric tons or 98.8 percent of total production, with China the largest producer. 

Seaweeds of various different species are well known in Asian cuisine, and seaweed extracts such as carrageenans, alginates and agars are used in a vast array of manufactured foods. Whether we know it or not, we probably consume seaweeds in one form or another every day of the week, particularly if we drink beer, eat ice cream or clean our teeth.

Techniques for growing seaweeds are well established and relatively simple. Species are available for every type and temperature of water; they require no feed, they grow fast, they reduce eutrophication, they absorb carbon, they are simple to harvest, and the culture equipment is cheap and simple. So why don’t we grow them in any appreciable quantity in Europe and North America?

The answer is not just simple economics, but seems to be a combination of labour costs, lack of access to the large areas required, a lack of investment into methods of mechanisation and no history of growing what is seen as a low status product. It might also be that we are missing a trick by imagining seaweed is something that has to be grown “somewhere else.”

However, this picture looks set to change in the next decade or so. Already there are artisanal growers of edible seaweeds in Europe and North America tapping into high value niche markets for locally grown products. Names such as Dulse, Laver, Dillisk, Irish Moss, Dabberlocks and Sea Lettuce are becoming as well known in the UK as Nori, Wakame and Kombu are in Japan. The use of seaweed as a human food is where the highest prices are to be found, and there seems to be growth potential for this market. We will undoubtedly see more entrepreneurs starting farms to supply fresh and dried locally grown seaweeds in the near future.

Besides these small scale developments, it is more likely to be new and innovative uses of seaweeds that will drive the major growth of macro algae aquaculture, and a project taking place in Scotland and Ireland is breaking new ground. These two countries have a long history of exploiting wild seaweed resources for food and fertilizer, and in early 19th century Scotland, as many as 40,000 people depended on kelp harvesting for a living. Much of the crop was burnt to produce kelp ash, which was important in the manufacture of soap and glass.

The current project, BioMara, does not depend on wild harvests but aims to grow kelp on farms, with the seaweed attached to floating lines. The resulting crop will be processed in a digester to extract energy in the form of biofuels such as methane and ethanol.

Another use of seaweed perhaps of more interest to Seafood Source readers, is as an ingredient in aquaculture feeds and a major project is underway in Ireland to investigate this potential. Seaweeds contain proteins and the vital omega 3 oils which are in increasingly short supply for fish diets.

If the alchemy of extracting these oils in an economic way can be cracked, then the next generation of seaweed farms may well be supplying the next generation of finfish farms and we may see farms proliferate in Europe. Seaweed might then become a more popular discussion subject in this forum.

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