Quick Key Facts

• Seaweed isn’t the name of one plant, but the term used for thousands of species of marine plants and algae and distinguished by three main categories: red, green and brown.
• Researchers say that sea species produce around 70% of the world’s oxygen, which includes phytoplankton, kelp and algal plankton.  
• Seaweed plays an integral role in absorbing carbon from the atmosphere, storing roughly 200 million tons of carbon each year, making it integral for climate change adaptation.
• In terms of climate change mitigation efforts, seaweed is also being used as a feed additive to help reduce methane emitted from livestock.
• Seaweed reduces pollution. With its ability to absorb toxins, it can be used to treat wastewater as well as reduce harmful nutrient pollution in waterways from agriculture and sewage runoff. Research also shows that seaweed can help reverse ocean acidification that is largely caused by the burning of fossil fuels. 
• While seaweed grows naturally, it can also be farmed. In the last decade, seaweed production has grown to 30 million tons worldwide.
• Seaweed is a nutritional powerhouse and it is used in both food for humans and animals, and found in a variety of medicine and beauty products. 
• Seaweed can be turned into biofuels and bioplastic, to be used as a plastic packaging alternative that is better for the environment.
• Seaweed can be used as a fertilizer and soil conditioner that helps abate the loss of topsoil.
• Extracts from certain seaweeds, like agar and carrageenan, show up in many lotions, soaps and processed foods.

History of Seaweed

Prior to 2020, seaweed, known as macroalgae, was thought to be around 800 million years old, but a green seaweed fossil discovery in Northern China dates back over a billion years, with some scientists believing that it was the ancestor of not just modern day seaweeds, but also land plants such as trees, bushes, grasses and others.

Green seaweed was the first class of seaweed, and over the course of evolution red and brown seaweed emerged. Thousands of different species now belong to each of these categories. 

Seaweed was used for thousands of years to enrich infertile and oceanfront soil in agriculture with the first written record dating back to the Romans. It was also used as medicine and food, and much like today, a dietary staple in Asian countries like Japan, China and Korea.  

Seaweed was also used as traditional medicine by many coastal dwellers and First Nations peoples. 

In some Indigenous cultures, like those in the Pacific Northwest, coastal Salish myths spoke of the interdependence and spiritual kinship between the people and the sea, as well as traditional pathways and marine livelihoods in coastal communities, where it was utilized in fishing, hunting, food preparation and other ways.   

Industrialization of Seaweed

During the 16th century in Europe, kelp, which is a brown seaweed in shallow salt waters, started to become harvested and burned for its sodium compounds (soda), iodine and potassium compounds (potash), which were used to make soaps, glass, fertilizers, linens and eventually explosives. 

Prior to this, potash was traditionally made by using wood ash and water, until wood supplies dwindled and the Scots began to use more kelp, which later was used throughout Europe to meet the demand of the above industries, which devastated traditional farming in coastal communities.  

Germany became one of the highest producers of the world’s potash, after it discovered vast amounts of potash salt that could be mined, but stopped exporting during the outbreak of World War I. The U.S., which was one of its largest buyers, used it for fertilizer on crops like cotton, corn, potatoes, beets and tobacco. 

This led the U.S. to build up its own potash industry by burning kelp like its European counterparts, becoming a major industry along the Pacific in California, while creating gunpowder to ship to the UK during the war. 

Once the war was over, the revival of German imports ended California’s industry. However, the seaweed industry has continued to grow in the U.S. and all over the world.

With its versatility and numerous health benefits, seaweed is found on plates globally, in cosmetics, pharmaceuticals, supplements, is used as a thickener and emulsifier foods and other products, and is now being looked at as a solution for our most urgent environmental challenges.  

Seaweed and the Environment

Researchers say seaweed is responsible for around 70% of the world’s oxygen, and the basis for the ocean food chain, providing critical habitat for fish, birds and marine mammals to find food away from other predators. 

Seaweed also has the capacity to reduce pollution. With its ability to absorb toxins, it can be used to treat wastewater as well as reduce harmful nutrient pollution in waterways from agriculture and sewage runoff. Research also shows that seaweed can reverse ocean acidification that is largely caused by the burning of fossil fuels. 

One of the larger draws of seaweed these days is also its ability to sequester carbon. 

According to a BBC report, it is estimated that it could sequester 200 million tonnes globally. This kind of sequestration is known as blue carbon, which is carbon captured by ocean and coastal ecosystems.

Seaweed grown as a crop can be sunk into deep water rather than harvested, which offers a strategy for climate change mitigation. 

Blue carbon markets have been popping up globally, with seaweed (kelp in particular) becoming potentially eligible for carbon credits — a sometimes controversial scheme where people can earn credit for sequestering carbon and sell it to companies that want to counteract their own emissions. 

Oceans 2050, an initiative spearheaded by Alexandra Cousteau and Fritz Neumeyer, is leading the global effort to research seaweed carbon sequestration to be able to provide the quantifiable evidence the carbon market needs so that seaweed farmers can monetize their efforts. 

Seaweed Farming 

^{A seaweed farm in Indonesia. Konstantin Trubavin / Cavan Images}

While some have started kelp farming efforts to implement ecosystem restoration, the farming of seaweed has been around for hundreds of years.  

Farmed seaweed is used for a variety of industrial products, food, feed and biofuel. It can be farmed on both on-shore and land-based farms. 

On-Shore Farms

In on-shore farms, farmers grow seaweed using a process known as vertical farming, which means most seaweeds grow on long lines suspended around 4-8 feet below the surface throughout the winter.  Farming offshore not only provides a source of marine permaculture that grows seaweed for products, but also food security, while working to fix the environment. 

According to Scientific American, a single acre of ocean can produce 25 tons of greens and 250,000 shellfish in five months, which suggests that a network of small underwater farms could potentially feed the planet.

California Sea Grant said that the appeal of nearshore environments keeps labor costs low, but the competition for suitable sites from the commercial fishing, shipping and tourism industries has increased interest in off-shore production, including at wind farms. However conditions can be challenging and concerning regarding ecosystem impacts. 

Land-Based Farms

On land-based seaweed aquaculture farms, seaweed is grown in tanks or ponds, where environmental conditions can be controlled. This also provides an opportunity to grow species that cannot be grown on lines. 

Seaweed Aquaculture Regulations  

To farm seaweed it’s important that it follows regulations not to damage the environment.

In 2021, the National Oceanic and Atmospheric Administration, U.S. Department of Commerce and National Marine Fisheries Service put out a state by state guide of seaweed aquaculture leasing and permitting requirements. 

In general, for onshore production, farmers need to register with the Department of Fish and Wildlife, and if a structure is involved on state land, they need to obtain a lease from the State Lands Commission. 

For open-water seaweed production, a state water bottom lease needs to be obtained, along with a complete environmental review for the area and permits for farming. 

Impacts

In the past 20 years, seaweed farming and production has grown exponentially. According to FAO, the global seaweed output (both wild and aquaculture) has increased from 118,000 tons to 359,200 tons from 2000-2019. In 2019, 97% of global aquaculture seaweed came from artificial farming with production led by Asia and Indonesia. 

In North America, 95% of seaweed was obtained from natural sources.

In 2021, Scotland charity Sustainable Inshore Fisheries created a guide to encourage coastal communities to consider both potential positive and negative impacts of seaweed aquaculture sites in local areas and ecosystems.   

Positive Impacts

• Seaweed cultivation offers opportunities for economic activity which can bring jobs and income to coastal communities. 
• Seaweed cultivation may also increase marine biodiversity, as cultivated seaweed will provide both food and shelter for other marine organisms while it is growing.
• Potential carbon sequestration benefits arise from seaweed growth.

Negative Impacts

• Impacts on seabed habitats could result in habitat loss.
• Entanglement of marine mammals and other marine species.
• Impacts on tidal currents and water movement.
• Impacts on genetic diversity from genes from cultivated seaweeds drifting into neighboring wild seaweed communities.
• The introduction of alien invasive species can disrupt natural ecosystems and have significant economic impacts. (Most countries have restrictions placed on the introduction of non-native species.)
• As cultivation of seaweed takes place on long-lines suspended in the water column, cultivated seaweed may reduce the light available to underlying seabed habitats, what is known as seabed shading. This is particularly an issue for cultivation taking place in shallower waters or for larger scale cultivation. 
• Since seaweed removes nutrients from the marine environment as it grows, it may result in nutrient depletion in surrounding waters, with impacts for other marine species or the broader marine ecosystem.  

Seaweed Decline

Though seemingly abundant, seaweed has been listed as endangered in recent years. This has been the result of coastal development that destroys habitats, pollution, heatwaves, storms, overfishing and global warming. 

In 2011, Western Australia lost 43% of its kelps in an extreme heatwave, while Northern California also saw a 93% decline from 2008-2014 according to aerial surveys by the CA Department of Fish and Wildlife.

Indigenous-Led Restoration

On Long Island, the Shinneock Nation own and operate the first native-owned and operated kelp farm on the East Coast. Called the Shinnecock Kelp Farmers, they are reviving traditional practices in an ecosystem their ancestors stewarded for thousands of years before European colonizers and commercial fishing arrived. 

The kelp farmers are getting technical assistance from Greenwave, an ocean farming incubator, who also offers 10 cents a pound for the kelp grown.

Coastal Indigenous tribes are leading restoration efforts on both coasts, alongside those in Hawaii. 

The Limu Hui, a community group in Hawaii, is working to restore 60 plus limu (seaweed) species that have become less common due to environmental changes from climate and colonization, with the goal of restoring the ecosystem and traditional cultural uses to be able to pass down ancestral knowledge to the next generation. 

There are also a number of Tribes in the Pacific Northwest and Alaska who, in addition to connecting to their longtime-stewarded ecosystems, are working on restoration projects to create food sources, sellable products and stable jobs. 

Seaweed Uses

Seaweed is pretty ubiquitous in a number of products, as well as a source of food, and already functions as an environmental solution in a number of areas. Here are some of its uses: 

Methane Reduction in Livestock

Methane, which is one of the leading contributors to climate change, accounts for 30% of all greenhouse gas emissions. One third of those emissions comes from cows, specifically cow burps and flatulence. 

As cows digest food, the microbes in their stomachs produce the methane, but researchers have found that feeding little bits of seaweed to cattle could cut their methane emissions by more than 80%.

Subsequently, scientists at Australian company FutureFeed worked to determine which kind of species of seaweed would be most effective, landing on Asparagopsis taxiformis, a type of red algae.

Since then several companies have popped up offering feed additives, working on how to scale production to meet global demands.

The most recent is Rumin8, an Australian start-up backed by Bill Gates. The company will not farm for it, but rather reproduce it in a lab for distribution to both developed and developing countries.

The more established Blue Ocean Barns, which has labs in both Hawaii and San Diego, produces their product Brominata, which they now distribute with partners such as ice cream giants Ben and Jerry’s, and other dairy and beef farms, with sales approved by the California Department of Food and Agriculture. The company, which received $20 million in funding from Valor Siren Ventures last fall, also certifies carbon credits for corporate partners.

Another Hawaii-based startup, Symbrosia, has recently partnered with algae supplement producer Cyanotech on their product SeaGraze, and has already been running pilot programs with the regenerative ranching collective Carman Ranch and others. 

Livestock Feed

In coastal areas, for hundreds if not thousands of years, sheep, cattle and horses have eaten seaweed, particularly in Europe. Today the availability of seaweed for animals has been increased with the production of seaweed meal, with Norway being one of the earliest producers. 

Besides using seaweed as a means to curb methane in livestock, its dense nutrition also makes it an excellent feed contributing to protein and energy requirements, as well as serving as a prebiotic that could enhance health. 

However, monitoring of the minerals in seaweed is essential, as they absorb heavy metals and if not monitored could become toxic to the animal, as with humans. 

Biofuel

Using kelp in the biofuel industry isn’t new. Throughout the 1970s to 1990s, both New York and California were part of the U.S. Marine Biomass program. It began as a response to the energy crisis caused by an oil embargo imposed by the Organization of Arab Petroleum Exporting Countries. 

The program was eventually discontinued because it could not compete economically with fossil fuel production. It was also criticized by the public and media. 

Now utilizing seaweed as biofuel is gaining popularity again amongst researchers as a viable and renewable resource for fuel due to pollution, inflated oil prices and climate change, particularly since it can produce better yields with less resources. 

Plastic Alternatives

Several startups globally are researching and developing alternatives to help solve the plastic crisis. 

In the Philippines, innovators developed a biodegradable plastic wrap alternative extracting carrageenan from seaweeds and pectin from mango peels.

In London, the startup Notpla is designing a seaweed based replacement for other single-use plastics. Their products include sachets for condiments, water and even alcohol; a film wrap for products in your pantry or bathroom, like coffee or toilet paper; and food takeout boxes that replace plastic-based coating with seaweed lining to make them fully biodegradable.

Seaweed is also being used to make sustainable fabric for clothing and eco-friendly shoes to abate usage of plastic-based acrylic, nylon, spandex and polyester, which often ends up in landfills.  

Seaweed as Fertilizer

Seaweed has long been used in coastal communities as fertilizer and soil conditioner. 

Seaweed is beneficial to soil and plants, helping to provide nutrients, and stimulating growth. In general, seaweeds contain 10 times the mineral levels of land-based plants and are particularly rich in iodine and calcium.

There are currently a number of soil fertilizers on the market, but if you live in coastal areas, sustainably harvesting washed up seaweed can be directly applied on garden beds (too salty to plant), or it can be composted or added to compost to mix with the soil later. 

The species of seaweed typically used are sargassum, ascophyllum, ecklonia and fucus.

Wastewater Treatment

Seaweed can be a great bioremediation tool for wastewater due to its ability to absorb toxins. Wastewater from industrial operations, and conventional agriculture operations where livestock waste, synthetic pesticides and other causes pollute waterways, causing eutrophication, which is a process when the environment becomes so enriched with nutrients, it increases the amount of plant and algae growth to waters. Some of that growth is harmful algal blooms. 

Harmful algal blooms occur typically result from the artificial nitrogen and phosphorus in synthetic fertilizer from farms that wash out in the rain and enter waterways. This is harmful to both humans and animals, and those who drink or swim in it can have rashes, fever, liver and kidney damage. 

There are other harmful effects also from industrial and commercial wastewater pollution that contain excess nutrients, which can also cause eutrophication, and heavy metals, which also have detrimental impacts on the environment and human health. 

Seaweed’s ability to absorb heavy metal toxins from these became apparent when seaweed used as food for humans was first being analyzed. The heavy metal content varied according to geographic source and proximity to industrial waste sites. From that research came the idea that they could be used as indicators for heavy metal pollution. 

While there are more expensive and less sustainable ways to treat the water, researchers found that seaweed is a great sustainable and cost-effective source to absorb excess nutrients and heavy metal pollution. 

In China, they found large-scale seaweed farms removed approximately 75 and and 9.5 megatons of nitrogen and phosphorus that prevented eutrophication from agricultural, industrial and sewage wastewater. The World Bank estimated that a global seaweed harvest of 500 million tons by 2050 could utilize around 25 million tons of nutrient absorption generated from feces and fertilizers. 

Seaweed in Cosmetics and Other Products

As mentioned earlier, hundreds of years ago in Scotland, seaweed, particularly kelp, was burned down into an ash that was a practice utilized by many to use as a product in soaps, among other things. 

Now, unbeknownst to most of us, seaweed is part of many of our products. The popular extract from red seaweed called carrageenan is a binding agent used in foods as well as toothpaste. It also makes it into other products as a thickener and emulsifier in shampoos, conditioners, lotions and moisturizers. 

Alginate from brown seaweeds is also used as a thickening and stabilizing agent in many of those products as well, and is said to be a moisturizing agent. 

Seaweed as Food and Its Benefits 

Edible seaweed is a staple in many Asian diets and according to the Food and Agriculture Organization of the United Nations, China is the largest producer of edible seaweed, followed by Korea and Japan, but commercial harvesting occurs in another 35 countries with growing popularity in the United States.  

Seaweed is dense with nutrients, containing vitamins such as A, D, E, C and B, and minerals including calcium, potassium, magnesium and iron. It’s also packed with the minerals sodium, magnesium, phosphorus, iodine, potassium, iron and zinc. It also contains a high amount of protein. 

Some studies say that it may help blood sugar control, support healthy thyroid function and promote heart health. 

Common types of edible seaweed are nori, which is typically used to wrap sushi, kombu, sea Moss, hijiki, wakame, dulse and chlorella. 

The extracts carrageenan and agar from seaweed are also used in many foods that aren’t as healthy as a binding agent. Agar is used in icings, glazes, processed cheeses, jelly and jam. Carrageenan is used in ice cream, sauces, processed meats and soy milk. 

Seaweed as Medicine

Medicinal usage of seaweed has been around for thousands of years, with traditional seaweed-based treatments and remedies passed down orally among coastal dwellers from generation to generation. Some were collected in books, with the earliest archeological evidence dated back to 14,000 BCE in modern day Chile. 

Traditional Chinese medicine used hot water extracts of certain seaweeds in the treatment of cancer. Additionally, the Japanese and Chinese cultures have used seaweeds to treat goiter and other glandular problems since 300 BC.

Seaweed was also used in other areas of the world as treatment for wounds, burns and rashes, for abdominal issues, edema, goiter, cold and flu, intestinal problems, inflammation and a host of other issues. Some employed tinctures, infusions, pils, wines, poultices, ash and charcoal.

It was used in the popular 1800s cough syrup Bonnington’s Irish Moss.  

Cultures still use this traditional medicine today, but it has not reached mainstream pharmaceuticals in modern medicine. Research is being done and clinical trials are underway, however, some of which involve potential treatment for Altzheimers, and other research is being done for antimicrobial and anticancer treatments.

Some seaweed compounds, such as alginate, however, are already used regularly in the medicinal field as binding agents, carrier material of medical tablets or wound dressings.   

Policy

According to a study, the rapid expansion of the seaweed industry, combined with rising seawater temperatures and coastal eutrophication, has led to an increase in infectious diseases and pest outbreaks. Despite biosecurity policies to keep the spread of this happening in other global food production, there isn’t anything effective in place for seaweed aquaculture. 

Currently, there is also no federal guidance on the food safety risks of seaweed in its whole form, leaving states unsure how to proceed with their own laws and regulations, which according to the National Sea Grant Law Center, is impeding the growth of the industry.

This year, however, the Coastal Sea Grant Act of 2023 was introduced — which is a bill directing NOAA and the U.S. Department of Agriculture (USDA) to produce a joint study evaluating the benefits and impacts of coastal seaweed farming — and includes the Indigenous Seaweed Farming Fund to reduce cost barriers for Indigenous communities wanting to participate in coastal seaweed farming.

The hope is to also develop regulations based on the study to maximize potential benefits of coastal seaweed farming, and avoid adverse impacts, calling for collaboration with the Interagency Working Group on Indigenous Traditional Ecological Knowledge, Tribes, states, local governments and other federal agencies on best practices.

Takeaway

Seaweed has an incredible number of uses. It’s an integral puzzle piece to the survival of our planet. It serves as a potential mitigator for climate change issues. It’s excellent for our health and used in a number of our everyday products. It’s also a catalyst for enabling the cultural and environmental restoration of ecosystems. 

While there are many benefits seaweed provides health-wise, agriculturally, culturally and environmentally, there still needs to be more conclusive research policies for seaweed production, particularly on environmental impacts of expanded industry.  

In the meantime, the growing interest in the industry because of its health reasons and its ability to help thwart climate challenges is helping it expand globally, and fast.  

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