Learn more about seaweed

What is seaweed and kelp?

Seaweed and kelp are a collective term for ‘macroalgae’ or ‘plants’ at sea. Unlike 'microalgae', they are visible to the naked eye. The group, which is also called sea vegetables, is very diverse with over 10,000 species globally and approx. 450 in Norway.


As food, one can compare seaweed and kelp with fruits and vegetables. The different sea vegetables have many different flavors, characteristics, textures and colors, and differ from each other in the same way as apples, pumpkins and herbs.


While kelp is a group of large perennial brown algae, which mostly grows below the coastal zone, seaweed is the term for a common family of brown algae, which we almost always find in the coastal zone. All three main groups are represented with species from the upper tide up to 50m depth. Of all 450 species of seaweed in Norway, none are inedible, but so far only a few have a tradition of being used as food. As of today, winged kelp and sugar kelp are the two species that are grown commercially. Other varieties, such as large kelp and pig seaweed, grow wild, and are harvested from the open sea for the production of, for example, alginate and seaweed flour.


Alginate is a substance extracted from seaweed and kelp that has good binding properties. They are used in hundreds of ways, for everything from soft drinks to jellies, omega 3 capsules and dentures. Commercial cultivation of seaweed and kelp has a long tradition in Asia but is fairly new in Europe. Outside Norway, it is now grown i.a. in the United Kingdom, Denmark, France, and Portugal, but most manufacturers are still in a testing phase. The Norwegian kelp has the potential to excel through very high quality.

What is it used for?


The uses for sea vegetables are many. Seaweed and kelp are used as vegetables, for fish and animal feed, and for plant fertilizers in agriculture. Alginate from the stalks of large kelp is central to "molecular gastronomy", which was founded by the Spanish master chef Ferran Adria. Every day we consume some substances from sea vegetables through products such as ready-made dressings, mayonnaise and ketchup. Today, seaweed and kelp are mostly used as a supplement to food in Norway, but new uses are constantly being explored. Seaweed is well suited as a flavor enhancer and spice. And whole, like vegetables and snacks. In the East, where people have a long tradition of eating sea vegetables, the use of seaweed and kelp as a health food has multiplied over a ten-year period, and the plants have become a luxury item in the beauty industry. Today, the industry is developing rapidly, and research is being carried out into how kelp can be used for biofuels, power production and to clean fjord areas through the utilization of emissions from fish farming.

What does it taste like?


Sea vegetables contain special flavours and are known for a lot of umami. Due to these flavour properties, and the natural glutamate content, kelp is excellent as a salt substitute.


The sugar kelp is thin and delicate and has a sweet taste. This is where it got its name from. The sugar kelp is therefore well suited for pastries such as biscuits, cakes and tarts, and can be used for kraft, dashi or chips. It is well suited as an accompaniment to fish, meat, cheese and vegetables.


The winged kelp resembles long feathers and has a hard midstripe. Winged kelp is excellent for miso soup, rich vegetable soups and stews. It is rich in calcium and has a chicken-like taste with rice. Winged kelp is well uncooked for salads if marinated in lemon juice.



As a coastal nation, we Norwegians have always lived by the sea. Of cod, saithe, crabs and scallops, and seaweed and kelp. The use of sea plants dates back several thousand years, to when we lived by hunting and fishing, and harvesting wild plants was an important source of food. In Chinese literature we can trace its use back to 600 BC. It was the monks from Ireland who brought with them the tradition of using spills to Norway. In the 16th century, seaweed and kelp were ground, mixed with flour and boiled into porridge. It was said that the poor had cranberries, shells and seaweed as their best food. 400 years later, a seaweed flour factory was established in Western Norway. Spills were used to feed sheep and other animals until 1950, and it was discovered that the sheep got a better immune system when they grazed on it. Because of this, good deposits of spills could increase the value of a farm.


The new oil


There are about 250,000 species of animals and plants in the ocean that we know of, and there are probably up to 750,000 other species that we have not yet discovered. Seaweed and kelp production in Norway represent the start of a new adventure and is still somewhat undiscovered and mysterious. Because even though we have long traditions for the use of kelp in Norway, the traditions have disappeared with the development, since we have been less dependent on the knowledge about the utilization of local resources. Now a changing climate perspective is forcing new ideas, methods and needs. By 2050, there will be nine billion people on the planet, all of whom will have access to enough and healthy food, energy and fuel. Researchers estimate that we must increase food production by 60%. This is one of the reasons why the opportunities in the sea must be better utilized. Today, the ocean accounts for only 2 percent of what we eat, while covering more than 70 percent of the globe. It gives us a sea of opportunities.



The nutrient content of sea vegetables varies with the species, season, age of the plant, pre-treatment and the growing area - which involves all of the growing conditions and ecosystem around - a kind of ‘terroir. This makes the cultivation of kelp an exciting but unpredictable project.


It is only ten years since the first research projects were started, and there is still a lot of trial and error as if to get more answers about the kelp’s life and development. Working with sea vegetables therefore still involves a high risk for the entrepreneurs who take the lead.


Seaweed products can contain thousands of times as much iodine as other foods, making seaweed and kelp a wonderful source of this vital mineral. Iodine is an element that has important functions in the body and affects i.a. the function of the thyroid gland.


Both too low and too high iodine intake can have serious health effects. A moderate intake of kelp is therefore recommended. The iodine level in the kelp is reduced by heat treatment.



With all the nooks and crannies, the Norwegian coastline is more than 40,000 km and consists mostly of hard bottom, where the seaweed can attach itself. This contributes to Norway having Europe's largest stock of sea vegetables. Like plants on land, seaweed and kelp grow with energy from sunlight and with the conversion of CO2 into oxygen. But unlike agricultural production, it is not necessary to fertilize kelp in aquaculture. All the nutrients it needs are naturally found in seawater. Worldwide, the natural kelp forest is considered to be one of the most productive of the world's wild plant communities. When it comes to CO 2 uptake, the wild kelp forest is 5-6 times more efficient than rainforest per tonne. The kelp forest, Norway's rainforest, is an important hiding place for fry, wrasse, cod and saithe, and several types of small crustaceans. Seaweed is a local and short-lived source of sustainable nutrients.



The cultivation of kelp begins in October-November before the sun disappears completely. Then the growers sow microscopic kelp seeds or cuttings on ropes that are placed horizontally below the sea surface at a depth of 1-2 meters. When the sun returns in February, the plants gain momentum. The kelp grows in the winter and into the spring and is harvested in April-May. Then the individuals are 1.5 to 3 meters long. A kelp leaf can be fully grown within 8-12 weeks. The kelp leaf is annual while the stem is perennial. The first kelp cultivation trials were carried out in 2009, and the industry is still in its infancy.