Seaweed – the future potato

Terrestrial farming continuously take a lot of input, such as fertilizing, watering and heating up greenhouses. Growing seaweed and algae takes none. In fact the water plants convert CO2 from the atmosphere into oxygen and help to clean the water for unwanted output from terrestrial activities like the outlet of nitrogen waste from traditional farming, which usually ends up in the ground water.

Marine plants – ­ the plants in the sea – do not contract pathogens or plant diseases as does their terrestrial counterparts, so no need for pesticides, herbicides or other toxins. Seaweed can be grown on a large scale in a sustainable way, but can also be harvested wild as there in the oceans naturally occur massive quantities of seaweed.

The oceans are running out of fish. Seaweed has a fast reproduction, so there´s not a big chance the same is going to happen with seaweed. Denmark and the Netherlands are among the most intensely cultivated countries in the world. We are running out of space to cultivate. The solution could be to start to grow the Danish oceans.

With 7.000 kilometer of coastline more than 500 species of algae in the Danish seas, many see a great potential in aquaculture. Seaweed could become a giant industry in Denmark – according to Annette Bruhn, researching macroalgae at Havets Hus in Jutland. In many asian countries makes up 10% of of the populations diet. In Asia alone seaweed had a market value of 31,5 billion DKR in 2012.


SeaweedhouseSeaweed House, in Læsø, is made out of seaweed.



Seaweed has endless applications. It can be used for fertilizer, animal feed, to produce salt, to burn for fuel, building materials, isulation, filling for furniture and matresses, tobacco, soda, potash, glass, gun powder, textiles, yarn, seawalls, field boundaries, as well as production of soap and plasterboards. Many probably remember the seaweed matresses from the 1970s.

In Læsø is a house built with seaweed. Realdania Byg, a non­-profit company, is behind this as well as other sustainable building projects. The house look like a wooden log house, as it is built of rolls of eel grass, that look just like wooden logs. Seaweed is a 100% non-­toxic, super-­insulating, fireproof building material, that provide a very good indoor climate and Seaweed House has life expectancy of 150 years.

The edible sea plants are in every way a sustainable, CO2­-positive “crop”, that can be used for bio-­energy, bio-­fuel and bio-­gas.There is a massive interest for seaweed and algae both molecular gastronomy and the food industry, as products like Irish Moss, alginate, carrageenan and agar agar is largely used for stabilator, emulsifier and thickener in a number of foods. Seaweed is a giant unutilized resource for Denmark, that can replace CO2­-­producing materials and products in the future society.




Headchef René Redzepi, one of the pioneers in the new Nordic kitchen, had sea lettuce, dulse, sugar kelp and sea thong on the menu at the worlds best restaurant, Noma. For spice, as salad, with potatoes in rösti, as seaweed-cheese and many more ways. Mielcke & Hurtigkarl had several dishes with seaweed on, both starters, mains and desserts. Red, green and brown seaweeds. Blanched seaweed for instance. Gourmet-restaurants all over the world use seaweed in different ways in fine cooking. Chocolatier Thormar Thorbergsson combine several types of seaweed with chocolate, such as the red algae dulse and the green sea lettuce.

Seaweed has many other use than maki rolls and seaweed salad in the sushi bars. You can make gorgeous pies or omelets with seaweed, risotto with seaweed, stir-fries with seaweed, potato mash with seaweed, seaweed pesto, seaweed pasta and pasta with seaweed, as well as soups and dressings with seaweed. Furthermore you can put seaweed in your baking, for instance bread with seaweed (helps to tough the flour) or seaweed flour. Fried, crispy seaweed is a good alternative to bacon, that won over many people. It even have the distinct scent of bacon when fried.

Desserts with seaweed is more common than you think. As thickener or gelling agent in for instance ice cream, pudding, jello and konfekt, like the Japanese dessert konfekt yökan, made with red azuki beans. Azuki-bean paste you find also as cake filling or filling in Asian buns. Cavi-art is a Danish seaweed product, that not only taste, but also look just like kaviar. Kelp noodles is an exotic gluten free RAW alternative to traditional noodles made with flour. If you soak and cook your chickpeas, lentil or beans with a piece of kombu seaweed, an enzyme from the kombu will neutralize the high content of phytic acid in the legumes, which can make them difficult to digest.


tangchipsSeaweed crisps made of bladderwrack

Seaweed snacks is a super healthy snack, rich in minerals and trace minerals. Roasted dulse was served for snacks in the beginning of the 19th century in Irish and Scottish pubs and is still a common snack in Iceland. You can make your own seaweed snacks roasting pieces of seaweed on a toaster or on a very hot pan until the seaweed just get crispy. The best seaweeds to make snacks are the red algae dulse and porphyra purpurea and the brown algae wakame, bull-kelp and makro-kelp. Alternatively one can roast seaweeds in the oven, tossed in olive oil and sesame seeds beforehand.


The new Aqua Seaweed Menu at Aqua Kyoto, London Picture   -  David Bebber
The new Aqua Seaweed Menu at Aqua Kyoto, London Picture – David Bebber


Seaweed was used for salt and for spice, as seaweed contain many salts such as iodine and potassium. Seaweeds are high in umami flavour because of the content of the amino acid mono-sodiumglutamate (MSG) which is also in high concentration in for instance mushrooms, cheese and meat. Some species of seaweed is sweeter cause of the high mannitol-content, such as sugar kelp or sweet kelp, Saccharina latissima. or Laminaria saccharina.

According to scientists from Sheffield Hallam University changing the kitchen salt with dried, ground serrated wrack or bladder wrack, the salt of which is 96,5% potassium, which lowers blood pressure and in many ways promote health. Regular table salt, NaCl, has sodium and chloride, which cause high blood pressure.

You often find gourmet salt with seaweed flakes, but one actually don´t need the salt, as most seaweeds enhance flavour enhance flavour by itself cause of the high level of the amino acid glutamic acid, a natural flavour enhancer.

You can make your own seaweed salt just by collecting serrated wrack or bladder wrack and dry or roast it in the oven. If you have a toaster, you can toast the seaweed for 3 min so it becomes so crispy you can grind it up in a stone mortar. Sea vegetables can be dried easily and can keep very well.

There are different kinds of seaweed on the market, flaked to sprinkle over the food as an alternative to salt, to boost the food or to add umami flavor. Typically you can find nori, wakame, sea lettuce and dulse.


drieddulseRed seaweeds have a deep, more sulphur-like taste and aroma.


Sea plants are eaten all over the world and Judith Cooper Madleners book The Sea Vegetable Book describe recipes with 25 different seaweeds, both brown algae, red algae, green algae and blue green algae from all over the world.

There´s a long tradition for eating seaweed in Japan, Korea, Kina og Philippines, North America (Nova Scotia, Maine, British Columbia and Californien for instance), but also places in Western Europe such as Bretagne, Ireland and Wales kept the tradition of eating seaweed.

Northwest coast indians ate a dried, fermented seaweed cake made of the red algae Porphyra and a dessert made of dried, pulverized mixed with water and boiled or whipped to a foam.

Laverbread is an old dish from Wales. “Laver” is the name of the red algae which is boiled to a puré and spread on toast, with garnish.

In Iceland they eat dulse dried as snacks, in salads, in bread, in skyr, cooked with milk and in oatmeal. Or as “sauer-seaweed”, the local sauerkraut by letting the seaweed ferment in a hole in the ground through winter.

In the healthfood shops you can buy seaweed tea, or you can make it yourself with dried seaweeds and boiling water. You can even get seaweed wine and seaweed beer.


Kelpie4Kelpie seaweed beer with bladder wrack from the Scottish brewery Heather Company.



Fertilizing the fields with seaweed has been practiced for centuries, especially in costal areas. On top of adding a lot of minerals and trace minerals, seaweed improve the soil as it makes it clump together, which makes it more porous and this improves the circulation of air and water and improve the terms for the activity of the earth worms.

Algae and seaweed should furthermore improve the resistance to frost and attacks from insects and fungus. Today brown algae are used for fertilizer, both liquid and dried, as the organic mindset against chemical fertilizers is rising, as these toxins ends up in the ground waters as nitrite and nitrate. Seaweed do not pollute like traditional fertilizer, and it has all the minerals and trace minerals., not only sodium, potassium and phosphorous.

Seaweed is applied in agriculture, not just for fertilizer, but also for animal feed, especially winter feed or as an alternative to grazing for horses and cows, for instance, as it was discovered that these animals went for seaweed at the beach by themselves, Also in the form of seaweed flour seaweed is used to feed pigs, sheep and hens because of the high nutritional value. Seaweed is a sustainable alternative to having to grow large pieces of land and big quantities of crops for just animal fodder.






Why not use the local seaweeds instead of importing expensive seaweed from the East?

Where can one find seaweed? You can collect fresh seaweed washed up on the Danish beaches or harvest it in the oceans. Free of charge.

Macroalgae grown in all Danish oceans. Because of the large fluctuations in salinity from Vesterhavet to Kattegat and Østersøen, there is big diversity and variation in the different locations.

Most of the washed up seaweed you find at the beaches is seagrass which grows at the bottom of the ocean. The most common species of seaweed in Denmark the brown algae bladder wrack, serrated wrack and sugar wrack, green algae such as sea lettuce and chlorophytes as or red algae like carrageen and dulse.

Only few species of seaweed are not edible, for instance the bluegreen algae which has toxins that attack the liver, the nervous system and cause skin irritation with swimmers, if they are in high concentration in the waters.BLADDERWRACK OR SEA LETTUCE?

Why not use the local seaweeds instead of importing expensive seaweed from the East?

Where can one find seaweed? You can collect fresh seaweed washed up on the Danish beaches or harvest it in the oceans. Free of charge.

Macroalgae grown in all Danish oceans. Because of the large fluctuations in salinity from Vesterhavet to Kattegat and Østersøen, there is big diversity and variation in the different locations.

Most of the washed up seaweed you find at the beaches is seagrass which grows at the bottom of the ocean. The most common species of seaweed in Denmark the brown algae bladder wrack, serrated wrack and sugar wrack, green algae such as sea lettuce and chlorophytes as or red algae like carrageen and dulse.

Only few species of seaweed are not edible, for instance the bluegreen algae which has toxins that attack the liver, the nervous system and cause skin irritation with swimmers, if they are in high concentration in the waters.


dulseDulse – one of Denmarks most delicious seaweeds..



As Earth was created 4,5 billion years ago, there was an different atmosphere altogether. Life was prokaryote bacteria. For about 2,5 billion years ago a change took place as new lifeforms emerged, the oxygen producing microalgae. And later the macroalgae. These little photosynthetic organisms in the ocean were the first plants could convert carbondioxid (CO2) into oxygen and organic matter, carbohydrates (C6H12O6) when exposed to sunlight. No other event in the history of Earth has changed the earths climate, surface and atmosphere as much as the appearance of bluegreen algae and later plants and photosynthesis and thus oxygen. More complicated organisms emerged with oxygen, such as fungi and animals that need oxygen.

It is estimated, that algae are responsible for 90% of the oxygen in the atmosphere up to 80% of the organic production on Earth. Macroalgae produce up to 14 kilo of organic carbon per m2, in comparison to terrestrial plants, that only form about 1 kilo. Some species of seaweed can grow to be 30-50 meter long and the productivity in macroalgae is so high that the largest brown algae can grow up to half a meter a day, which is a couple of centimeters a day.

The plants are producing the oxygen in the atmosphere that we breathe. Seaweed are making photosynthesis when exposed to sunlight, producing sugars and oxygen from carbon dioxide, the raising the oxygen content and lowering the content of CO2 in the water accordingly. If not for the waterplants we would have oxygen depletion in the waters and dead fish floating around.

Seaweed are found growing down to 250 meters under the surface of the ocean, where there literally is no sun. There has even been found a red algae making photosynthesis at a depth of 268 meters, where only 0,0005% of the sunlight can reach and there is pitch black. Another remarkable detail is that seaweed can dry out, loosing up to 90% of its water and still continue photosynthesis a couple of hours after being put back in water.





Seaweed has all the minerals of the sea. Calcium, potassium, magnesium, sodium, phosphorous, iodine, iron etc., and also more than 60 trace minerals, such as manganese, zinc, chromium, chloride, copper, selenium and molybdenium.

The mineral content is ten times that of terrestrial plants. Actually seaweed contain 14 times more calcium than milk by weight. And is a better source of iron than spinach. Seaweed contain more vitamin C than citrus fruits and more vitamin D than milk.

The protein content is likewise high in seaweed and algae, and considered high quality protein. Porphyra has a protein content of 47%, most seaweeds up till 25% protein, like Laminaria (25,7%). Red algae usually have between 15.5-21.3% protein. Both the green algae chorella and the bluegreen algae spirulina are so rich in protein, that more than 60% of the dry weight is protein and both are what you call “a complete protein”, meaning it has all the 8 essential amino acids, that we humans are not capable of synthesizing and are dependent on getting through our diet.

On top the the high mineral- and protein content, seaweeds has a high fiber content as well as a high content of more than 12 vitamins. Nori and winged kelp has a high content of vitamin A. All seaweeds are rich in vitamin C, vitamin E and the B-vitamins. Vitamin B12 synthesized by bacteria living on the surface of the surface of the algae..

There is not exceedingly many food sources of vitamin D out there, but seaweed is one of them, and hence the levels in the food chain that live off seaweed and algae, like fish. Vitamin D in the form of ergosterol. As you may know D-vitamin is fat-soluble and is therefore found in high concentration in fish oil.

Some people may wonder where the eskimos get their vitamin C from, as there there isn’t too many fresh fruit and vegetables growing in Greenland, which is covered in ice and snow most of the time. The eskimos in Greenland were eating seaweed, particularly in the winter. That was their source of vitamin C. The Nordic vikings brought dried seaweed on long sea voyages. That´s how they managed not to get vitamin C deficiency and scurvy.

Furthermore seaweed has a lot of water-soluble fiber. The ones that are supposed to be good for the digestion, as they speed up the passing of the food through the stomach and the intestines and improve the assimilation of minerals. A whole 25-75% of the dry weight is actually fiber.

Fresh seaweed packed with enzymes and these enzymes are also kept in dried seaweed. Not in cooked or roasted forms.

Seaweed is not just rich in essential fatty acids, omega 3 and omega 6, but have even the ideal ratio between the two, which is around 0,3 – 1,8. The ratio between omega 3 and omega 6 is for most people 0,05, so generally get too much omega 6 and too little omega 3.

It is the omega 6-fatty acid AA and the omega 3-fatty acids EPA and DHA in seaweed, that is the source of the same in fish and hence fish oil. This is where the fish get their essential fatty acids from. From the lower levels of the food chain.

In addition to essential fatty acids, seaweed contain other kinds of beneficial fats such as plant sterols like fucosterol and desmosterol, which lowers the uptake of cholesterol from the food and hence lowers the level of cholesterol in the blood and lowers high bloodpressure.

Algae and seaweed contain a number of plant pigments which give red algae, green algae and brown algae their color, for instance the green chlorophyll and the yellowbrown carotenoid fucoxanthin i brown alagae. These compounds are very coveted as they are said to be extremely healthy.

In particular the red seaweeds are rich in taurine, an amino acid which is important for forming bile salts that bind cholesterol so it is excreted, lowering the cholesterol in the blood.





As algae and seaweed are very old life forms and has existed for hundreds of millions of years, through which they have developed some unique and effective defenses that protect the algae from microorganisms. These defenses are bioactive compounds, which possibly can be used by humans, like iodine.

Some of the compounds are specially interesting. In Ole G. Mouritzens book Seaweeds: Edible, Available & Sustainable” you can read about many of these compounds, for instance the polypeptide named kahalalid F, has anti-viral effect and may be a part of the explanation of why HIV/AIDS is less frequent in populations eating seaweed, like Japan and Korea and the African state Chad, where a big part of the population eat bluegreen algae. The frequency of HIV/AIDS is only 2-4% here, in comparison to 10% in the rest of Africa.

Carrageenan from red algae is mentioned as having a well documented anti-viral effect against for instance herpes, HIV and HPV-virus and the polysacaccharide fuciodan from brown algae, has shown to suppress colonization by Helicopacter pylori in the stomach and thereby prevent ulsers.. Carrageenan not only protects you from HVP-virus, but has shown to be more effective against the subsequent cervical cancer than the medicine on the market today. Seaweed contain a number of terpenes, with anti-bacterial and anti-cancer effect, as well as glycolipids and polysaccharides (especially fuciodan), which has shown to surpress the growth of tumors.

Brown algae contain certain tannins and polyphenols, while green algae and red algae contain for instance acrylic acid and bromophenols, which all contain natural defense against microorganisms and has shown anti-bacterial effect.

Japanese women living in Japan generally has low frequency of breast cancer and thyroid cancer, actually eight times lower than for women in United Kingdom. Where these women to immigrate to countries where they would take on a western lifestyle with only little seaweed in the food, they have same rist of breast cancer as the women in the Western world.

The iodine in many seaweeds, especially Kombu, should balance the thyroid activity and prevent and help thyroid cancer. Eating seaweed is said to lower the cholesterol and have a detox effect effect on the body. The content of antioxidants in seaweed is extremely high, which alkalize the blood, and alginic acid absorb toxins from the digestive tract.

Research at the Hokkaido University show that the compound fucoxanthine, which is found in Wakame, effectively burn fat. Also the algae Bladderwrack are used to promote weight loss on a large scale. Spas all over the world usually have one or more forms of algo-terapy such as algae masks, algae wrappings og algae baths, which are supposed to be good for a number of illnesses such as arthritis, eksema, astma and a number of skin disorders.

According to a study at McGill University in Montreal, seaweeds and algae provide a substance called aliginic acid that helps the body eliminate toixins. When exposed to nuclear radiation people take iodine supplements or eat foods high in iondine, because if the body is saturated with natural iodine from seaweed, it will more readily excrete radioactive iodine taken in from the air, water or food in the proximity after a nuclear blast. This prevents radiation poisoning of the thyroid as sea vegetables helps discharge radioactive elements and the body will change the radioactive iodine in the thyroid with the good iodine from seaweed. People in Nagasaki is said to have survived the atomic bombing in August of 1945 because they protected themselves against lethal doses of radiation on a diet of brown rice, miso soup, seaweed, and sea salt.

If you want to try cooking with seaweed, here´s some easy recipes with Arame and Nori seaweed.




Seaweeds: Edible, Available & Sustainable, Ole G. Mouritsen, 2013, University of Chicago Press


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