OFFSHORE CULTIVATION OF SEAWEED – FIRST HARVEST

Early July seaweed growing in AlgaeCentre Denmark’s offshore cultivation site in Kattegat as part of the MAB4 project was harvested for the first time. The seaweed has been growing on lines in the area since December and the growth has been very good as expected in this area where a constant strong current brings plenty og nutrients to the seaweed.

Healthy sugar kelp

The harvested sugar kelp looked very healthy and the output of 1-2 kilos per meter of line is considered reasonable considering the late start in December. Preferably, the seaweed should be growing in the ocean from October as results from the MAB3 project showed this will increase overall growth.

The harvested kelp was also very clean with almost no epiphytes that is usually a large problem at this time of the year in Danish waters. This increases the commercial value of the seaweed considerably. A quite large amount of naturally occurring sugar kelp was growing on the unseeded main lines increasing the total biomass. This has not been observed to this extent in other Danish seaweed farms.

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Longline cultivation system

The cultivation system consisting of longlines has been put to the test during a winter 2016/2017 with both stormy conditions and very strong currents, and in the next years Aarhus University will evaluate which cultivation systems work best in offshore areas as the one near Grenaa in Kattegat.

Sea lettuce

Also cultivation of sea lettuce was tested in the area with positive results. The algae was put in the water in April and has grown to a size of 15 centimeter and a yield of 200 grams per meter of seeded line. Development of methods to grow sea lettuce in offshore cultivation is part of the Macrofuels project.

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