Seaweed

Seaweed is consumed across the world, particularly in East Asia, e.g. Japan, China, Korea, Taiwan and Southeast Asia, e.g. Brunei, Singapore, Thailand, Burma, Cambodia, Vietnam, Indonesia, Philippines, and Malaysia[8], and also in South Africa, Belize, Peru, Chile, the Canadian Maritimes, Scandinavia, South West England,[9] Ireland, Wales, Hawaii and California, and Scotland.

Gim (김, Korea), nori (海苔, Japan) and zicai (紫菜, China) are sheets of dried Porphyra used in soups, sushi or onigiri (rice balls). Chondrus crispus ('Irish moss' or carrageenan moss) is used in food additives, along with Kappaphycus and Gigartinoid seaweed. Porphyra is used in Wales to make laverbread (sometimes with oat flour). In northern Belize, seaweed is mixed with milk, nutmeg, cinnamon and vanilla to make "dulce" ("sweet").

Alginate, agar and carrageenan are gelatinous seaweed products collectively known as hydrocolloids or phycocolloids. Hydrocolloids are food additives.[10] The food industry exploits their gelling, water-retention, emulsifying and other physical properties. Agar is used in foods such as confectionery, meat and poultry products, desserts and beverages and moulded foods. Carrageenan is used in salad dressings and sauces, dietetic foods, and as a preservative in meat and fish, dairy items and baked goods.

Seaweed-covered rocks in the United Kingdom

Seaweed on rocks in Long Island

Alginates are used in wound dressings (see alginate dressing), and dental moulds. In microbiology, agar is used as a culture medium. Carrageenans, alginates and agaroses, with other macroalgal polysaccharides, have biomedicine applications. Delisea pulchra may interfere with bacterial colonization.[11] Sulfated saccharides from red and green algae inhibit some DNA and RNA-enveloped viruses.[12]

Seaweed extract is used in some diet pills.[13] Other seaweed pills exploit the same effect as gastric banding, expanding in the stomach to make the stomach feel more full.[14][15]

Algae's strong photosynthesis creates a large affinity for nutrients; this allows the seaweed to be used to remove undesired nutrients from water (as for instance in dead zones). Seaweed also generates oxygen, which benefits hypoxic (=oxygen-poor) dead zones.[16] Nutrients such as ammonia, ammonium nitrate, nitrite, phosphate, iron, copper, as well as CO₂ are rapidly consumed by growing seaweed. Reefs and lakes are naturally filtered this way (seaweed is consumed by fish and invertebrates), and this filtering process is duplicated in artificial seaweed filters such as algae scrubbers. China could remove its entire phosphorus effluent by increasing seaweed production by 150%.[17]

Modern floating algae scrubber/cultivator on a reef pond

Seaweed (macroalgae), as opposed to phytoplankton (microalgae), is used almost universally for filtration purposes because of the need to be able to easily remove (harvest) the algae from the water, which then removes the nutrients. Microalgae require more processing to separate from the water than macroalgae do; macroalgae is simply pulled out.

Marine species of Cladophora, Ulva (sea lettuce) and Chaetomorpha are preferred for filtration. Freshwater filtration applications commonly involve species such as Spirogyra.

"Ocean afforestation” is a proposal for farming seaweed for carbon removal. After harvesting the seaweed decomposes into biogas, (60% methane and 40% carbon dioxide) in an anaerobic digester. The methane can be used as a biofuel, while the carbon dioxide can be stored to keep it from the atmosphere. Seaweed grows quickly and takes no space on land. Afforesting 9% of the ocean could sequester 53 billion tons of carbon dioxide annually (annual emissions are about 40 billion tons).[17]

The approach requires efficient techniques for growing and harvesting, efficient gas separation, and carbon capture and storage. The Advanced Research Projects Agency for Energy has a $22 million program called Macroalgae Research Inspiring Novel Energy Resources (MARINER) supporting innovations that could aid a seaweed industry.<, ref name=":1" />

Other seaweed may be used as fertilizer, compost for landscaping, or to combat beach erosion through burial in beach dunes.[18]

Seaweed is under consideration as a potential source of bioethanol.[19][20]

Seaweed is lifted out of the top of algae scrubber/cultivator, to be discarded or used as food, fertilizer, or skin care

Alginates are used in industrial products such as paper coatings, adhesives, dyes, gels, explosives and in processes such as paper sizing, textile printing, hydro-mulching and drilling. Seaweed is an ingredient in toothpaste, cosmetics and paints. Seaweed is used for the production of bio yarn (a textile).[21]

Several of these resources can be obtained from seaweed through biorefining.

Seaweed collecting is the process of collecting, drying and pressing seaweed. It was a popular pastime in the Victorian era and remains a hobby today. In some emerging countries, Seaweed is harvested daily to support communities.

Women in Tanzania grow "Mwani" (seaweed in Swahili). The farms are made up of little sticks in neat rows in the warm, shallow water. Once they harvest the seaweed, it is used for many purposes: food, cosmetics, fabric, etc.

Seaweed is sometimes used to build roofs on houses on Læsø in Denmark[22]

Seaweeds are used as animal feeds. They have long been grazed by sheep, horses and cattle in Northern Europe. They are valued for fish production.[23] Adding seaweed to livestock feed can substantially reduce methane emissions from cattle.[24]

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  Onigiri and wakame miso soup, Japan
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  Laverbread and toast
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  Small plots being used to farm seaweed in Indonesia, with each rectangle belonging to a different family