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What is Seaweed Farming?
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Seaweed might look like an unlikely contender for a potentially scalable solution to climate change, but this slimy-looking brown kelp is starting to attract interest across the globe. Capable of storing carbon, protecting local communities from the impacts of climate change, and even offering a potential solution to the growing plastic crisis, seaweed farming offers a range of environmental benefits.
In this article, we’ll cover:
- What seaweed farming is and why it’s growing globally
- How seaweed is farmed using different methods
- What seaweed is used for across industries
- Environmental benefits and climate change potential
- Other benefits, from economic to health impacts
- Challenges and risks of large-scale seaweed farming
What is seaweed farming?
Seaweed farming, also referred to as kelp farming, is the practice of cultivating and harvesting seaweed or algae. Traditionally, the practice was mainly found in South East Asia, in countries such as China, Indonesia, and the Philippines, however, in recent years, its popularity has grown and seaweed farming is now practised across the globe. In fact, it's the fastest-growing aquaculture sector worldwide.
👉 Global production of seaweed was 10.6 million tonnes in 2000, but has since grown to 35.1 million tonnes in 2020.
How is seaweed farmed?
There are a variety of different methods for farming seaweed, depending on the climate and country in which it’s grown.
Longline farming
Seeded ropes suspended between buoys let seaweed grow freely in open water.
Widely used for scalable production — simple to set up, fast to harvest, and gentle on the seabed.
Net farming
Seeded nets hung vertically or horizontally form dense, high-yield mats.
Great in energetic waters — maximises space, boosts yields, and keeps harvesting straightforward.
Raft farming
Floating rafts support ropes or nets suspended just below the surface.
Low-cost and adaptable for shallow coasts — ideal for smallholders and community farms.
Bottom planting
Seedlings are pegged directly into the seabed in shallow, sheltered areas.
A low-tech method suited to hardy, substrate-clinging species — minimal kit, local ecosystem fit.
IMTA
Seaweed grown alongside shellfish or fish in a balanced, circular system.
Enhances water quality by absorbing nutrients, cuts waste, and diversifies farmer income streams.
“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.”
👉 Did you know? 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.
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What is seaweed used for?
Seaweed has many uses, including:
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Chemicals
Chemicals from seaweed feed industrial, pharma, cosmetic, and food sectors. Key derivatives include carrageenan (natural gelling agent) and agar (stabilising gel for texture and thickening).
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Food
Seaweed is fibre-rich and widely used in Asian cuisine. Its extracts also act as water retainers, gelling and emulsifying agents across many products.
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Fuel
Algal biofuel offers an alternative to land-intensive biofuels (e.g., corn, sugarcane) by converting seaweed biomass into liquid fuels or biogas.
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Bioplastics
Polymers from seaweed (e.g., alginate) can be used to make biodegradable films, packaging, and coatings—reducing reliance on fossil-based plastics.
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Fertilisers & soil
Seaweed extracts are used as bio-stimulants and fertilisers—improving soil structure, nutrient uptake, drought tolerance, and plant resilience.
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Animal feed
As a feed additive, seaweed can improve animal health and, in some cases, help reduce enteric methane when used in controlled formulations.
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Bioremediation & carbon
Seaweed absorbs excess nutrients and CO₂, supporting water quality and offering potential blue-carbon co-benefits when responsibly managed.
What are the environmental benefits of seaweed farming?
The rapid rise in seaweed production is also, in part, being fuelled by the growing realisation 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.
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Carbon sequestration
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.
👉 Did you know? One square kilometre of seaweed is able to sequester around 1,000 metric tonnes of carbon dioxide every year.
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.
“Researchers have found that coastal ecosystems (including seaweed farms) are able to sequester 20 times more carbon per acre than land forests, making them one of the best natural carbon sinks. ”
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 that 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 minimise the risk of coral bleaching.
Water filtration
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.
👉 Did you know? The Gulf of Mexico has a dead zone of around 4,280 square miles. This hypoxic area has oxygen levels 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.”
Shoreline protection
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 minimise coastal erosion.
👉 Did you know? Kelp forests in Norway have been found to reduce the height of waves by as much as 60%.
Improved biodiversity
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 replanted.
Biofuel potential
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 other biofuel options. Namely because it requires little to no input - ie. it doesn't need fertiliser (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 forests 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. ”
Methane reduction
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.
👉 Did you know? By adding a small amount of this seaweed to cattle feed, beef and dairy farmers can reduce the methane released in their cattle’s burps by between 82% and 98%!
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Other benefits of seaweed farming
Seaweed farming doesn’t just result in environmental benefits, it also brings with it a variety of other benefits, including:
Economic benefits
Climate change is threatening livelihoods across the globe, but perhaps nowhere more so than in 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, but it also provides economic opportunity for communities that have traditionally relied on fish stocks. In many regions where fish stocks have declined, seaweed farming offers an alternative and sustainable source of income, helping to support local livelihoods while protecting marine ecosystems.
Health benefits
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, offering a unique mix of essential minerals and beneficial compounds rarely found together in other foods. Its combination of bioactive compounds, fibre, and plant-based proteins makes it a valuable addition to a balanced diet, and research suggests some varieties may also support gut health and metabolic function.”
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Medicinal purposes
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.
Innovation
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 industries. 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.
👉 Did you know? Large-scale seaweed farms could potentially block sunlight, preventing it from reaching other marine life below. In addition, organic debris from the farms could alter the surrounding marine ecosystem.
Another 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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What about Greenly?
At Greenly, we help companies navigate the transition to a more sustainable future by measuring, managing, and reducing their environmental impact.
Our suite of sustainability services includes:
| Greenly's Services | What It Means |
|---|---|
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Carbon footprint assessments
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Track and analyse your company’s emissions across Scope 1, 2, and 3, gaining insights to manage and reduce your overall footprint. |
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Life Cycle Assessments (LCA)
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Understand the environmental impact of your products from raw materials to end-of-life and identify opportunities for sustainable design. |
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Sustainability reporting support
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Ensure compliance with key frameworks like CSRD, ESRS, TCFD, and IFRS by preparing clear, data-driven sustainability reports. |
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Supplier engagement
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Improve supply chain sustainability by assessing suppliers’ emissions and encouraging low-carbon practices across your network. |
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Custom decarbonisation strategies
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Develop tailored action plans to reduce emissions, improve efficiency, and achieve your long-term sustainability goals. |
Get in touch with us today to find out more.
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