Seaweed farms have attracted interest across the globe as a potentially scalable solution to climate change. The practice of growing seaweed brings with it a number of economic, social and environmental benefits that have led some to hail it as an ‘eco miracle’.
👉 In this article we’ll explore the many benefits of seaweed farming, while also considering the potential challenges.
What is seaweed farming?
Seaweed farming - otherwise known as kelp farming - is the practice of cultivating and harvesting seaweed or algae. The largest producers are China, Indonesia, and the Philippines, however, in recent years its popularity has grown and seaweed farming is now practiced across the globe.
👉 Global production of seaweed was 10.6 million tonnes in 2000, but has since grown to 35.1 million tonnes in 2020.
There are a variety of different methods for farming seaweed - depending on the climate and country in which it’s grown. Most often it is attached to thin ropes which are then suspended in deep water or between bamboo poles in shallow water. The seaweed anchors itself to the rope with holdfasts.
One of the main motivations for cultivating seaweed is that it doesn't require any feed or other input. All it needs is access to sunlight to survive and grow - making it very attractive to producers from an economic perspective.
👉Studies in the Philippines found that seaweed plots of one hectare could produce a net income that was 5 to 6 times greater than the average wage of an agriculture worker.
What is seaweed used for?
Seaweed has many uses, including:
Chemicals - chemicals found in seaweed are used in a variety of industrial, pharmaceutical, cosmetic, and food products. The most common derivatives are carrageenan (a natural gelling agent) and agar (a stabilizing gel that texturises and thickens).
Food - seaweed is high in fiber and a popular ingredient in a variety of culinary dishes (particularly in Asia). Derivatives of seaweed are also used for a variety of purposes such as water retention, gelling agents, emulsifying agents etc.
Fuel - algae fuel is an alternative biofuel to the more common varieties that use corn and sugarcane.
Environmental benefits of seaweed farming
The rapid rise in seaweed production is also, in part, being fuelled by the growing realization that seaweed has a number of environmental benefits and eco uses. It’s a ‘zero input’ crop that leaves the ocean healthier with each seaweed harvest cycle.
In this next section we’ll explore why seaweed farming is creating so much excitement in terms of climate change mitigation and adaptation.
Seaweed production functions as a form of carbon sequestration. In other words, this means that seaweed is able to capture carbon dioxide from the environment and store it - something that both reduces the amount of carbon in our atmosphere and diminishes ocean acidification.
👉 One square kilometer of seaweed is able to sequester a thousand metric tonnes of carbon dioxide annually.
Seaweed captures the carbon dioxide through photosynthesis, a process that it uses to create energy and to grow. This carbon is then stored as organic matter. Part of this organic matter eventually becomes waste or debris and is carried to the deeper ocean - something that is termed blue carbon.
Due to the low concentration of oxygen underwater (particularly at deeper depths) the plant material can stay buried for decades or longer before breaking down and releasing carbon back into the environment.
💡 To learn more about carbon sequestration why not check out our article on carbon sinks.
Researchers have found that coastal ecosystems (including seaweed farms) are able to sequester 20 times more carbon per acre than land forests.
Ocean acidification prevention
High levels of carbon dioxide in the ocean are also bad news in terms of ocean acidification. The carbon dioxide causes a series of chemical reactions which increase the level of hydrogen ions in the water. The effect of this is that carbonate ions are decreased and the water becomes more acidic in terms of PH.
One of the more significant impacts of this is that certain species such as coral, plankton and mollusks are no longer able to form their shells and skeletons.
Because seaweed farms act as a carbon sink, they are also able to raise the PH of their ocean environment. By reducing the acidity, they support calcifiers (ie. crustaceans), and minimize the risk of coral bleaching.
Seaweed farms are also beneficial in reducing the amount of nitrogen and phosphorus in our oceans. These nutrients have the potential to cause algal blooms which can be toxic to humans, marine animals and birds (these algal blooms are known as HBAs or harmful algal blooms).
When algal blooms grow out of control they deplete the level of oxygen in the ecosystem which can have devastating effects on marine ecosystems. Lack of oxygen can lead to the formation of dead zones.
👉The Gulf of Mexico has a dead zone of around 4,280 square miles. This is a hypoxic area of the ocean where oxygen levels are so low that fish and marine life struggle to survive.
Seaweed farms are able to improve the quality of seawater in a given area by filtering out a variety of inorganic nutrients.
The canopies of farmed seaweed actually soften the impact of waves. By interrupting the energy of the approaching waves, seaweed farms provide a buffer to shorelines and help to minimize coastal erosion.
👉 Kelp forests in Norway have been found to reduce the height of waves by as much as 60%.
Seaweed farms act as temporary forests, providing food and shelter for fish and other marine animals. Some studies indicate that when compared to the surrounding area, seaweed farms house over 70% more species.
When the seaweed is harvested the forest is admittedly lost, however, studies show that marine life is quick to reestablish itself when re-planted.
Given the urgent need to reduce our carbon dioxide emissions and to cut our dependence on fossil fuels, researchers and scientists have turned their focus towards climate-friendly biofuels, predominantly made from corn, canola, and soybeans. However, seaweed has attracted increasing attention in recent years for its potential as an alternative source.
Seaweed holds a number of advantages over the other biofuel options. Namely because it requires little to no input - ie. it doesn't need fertilizer (which is harmful for the environment), nor does it require water (a growing issue as our world heats up and we experience increasing incidences of heatwaves). Not only this, seaweed farms are incredibly space efficient - we don’t need to destroy forest or clear land to make way for them.
Recent experiments have shown that kelp in particular is promising in this area, and several companies are working on developing viable farming techniques to produce seaweed based biofuels.
Seaweed farming also offers a number of more novel environmental benefits. For example, a red variety of seaweed called asparagopsis has been found to be useful at reducing the methane quantity released in the burps of cattle.
👉 By adding a small amount of this seaweed to the cattle feed, beef and dairy farmers can reduce the amount of methane released in the burps of their cattle by between 82 and 98%!
Other benefits of seaweed farming
Seaweed farming doesn’t just result in environmental benefits, it also brings with it a variety of other benefits:
Economic benefits 📈
Climate change is threatening livelihoods across the globe, but perhaps nowhere more so than our coastal communities. With warming waters fish stocks are declining and marine ecosystems are being altered forever. Fishing communities and those who rely on the ocean and its produce as a source of income now face an uncertain future.
Seaweed however, not only actively counteracts the effects of climate change by acting as a carbon sink, it also provides economic opportunity for communities who have traditionally relied on fish stocks.
Seaweed is a very nutritious food. It contains a number of antioxidants (vitamins A,C, and E). It’s also a source of iodine which is essential for the functioning of the thyroid. Some varieties of seaweed possess other nutritional benefits - for example the variety known as purple laver contains B12.
Seaweed is one of the most nutrient dense foods on the planet.
Seaweed has been used in traditional Chinese medicine since at least 300 BC. However, Western medicine also relies on many derivatives of seaweed. Compounds like fatty acids, glycoproteins, alkenes, carotenoids and ketones are just a few examples of the many chemicals that can be extracted from seaweed for use in medicine to treat health issues such as eczema, cancer, renal disorders, asthma, heart disease, ulcers etc.
Seaweed is being explored for a number of different applications that not only present interesting business opportunities but also address some of the world’s biggest sustainability and development challenges.
Seaweed has potential for a number of applications across a wide spectrum of industries - including the cosmetic, food, agricultural, pharmaceutical and energy industry. However, the most headline grabbing application has been its potential to provide an alternative to plastic wrappers.
Developers have created a seaweed based coating that could potentially be used in fast-food packaging instead of plastic. It’s possible that seaweed transforms the global packaging industry and helps to solve our plastic pollution problem.
A note of caution when it comes to seaweed farming
Seaweed farming has a number of environmental benefits and is exciting in terms of its potential to help solve a number of sustainability issues. However, there are those who offer a word of caution.
Scientists point to the fact that seaweed farms are understudied and that we don’t fully comprehend their impact on marine ecosystems. They worry that seaweed farming could replicate some of the harm that farming on land has caused.
👉 Large scale seaweed farms could potentially block sunlight out, preventing it from reaching other marine life below from accessing this vital resource. Not only this, organic debris from the seaweed farm could potentially alter the marine ecosystem below it.
One other issue with seaweed farming is that seaweed is also experiencing the negative effects of climate change. Global warming is causing our ocean waters to heat up which is impacting the survivability of different species and causing huge upheaval in ocean ecosystems. This means that some regions that currently grow seaweed, may find it hard to continue to grow the same varieties in years to come.
This is why although seaweed farming shows incredible potential in terms of climate mitigation and adaptation, it’s necessary to proceed with caution to ensure that we don’t create any unintended and harmful effects on the environment. It’s also essential that we work to reduce the impacts of global warming and to prevent further climate change.
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