Is Seaweed Farming Sustainable? How Arctic Kelp Grows Without Land, Fresh Water or Fertiliser
Short answer: yes, in the ways that matter most for a food ingredient. Seaweed is one of the lowest input foods we know how to grow. It needs no farmland, no fresh water, no fertiliser and no feed. It grows on sunlight and on the nutrients already dissolved in the sea, and it pulls some of those nutrients, along with carbon dioxide, out of the water as it grows. The part that gets oversold is carbon. The popular idea that kelp permanently locks away carbon and helps reverse climate change does not hold up once the kelp is eaten rather than sunk to the deep ocean. So the honest case for farmed kelp rests on resource efficiency and cleaner coastal water, not on carbon burial.
Below is what the evidence actually supports, where the claims get shaky, and how our own Arctic winged kelp (Alaria esculenta) is grown off Northern Norway.
What makes seaweed farming different from farming on land?
Almost everything you eat starts with three things: land, water and added nutrients. A field of basil for pesto needs soil, irrigation in dry months, fertiliser and usually some crop protection. Seaweed skips all of it. There is no ploughing, no irrigation and nothing sprayed on it, because it hangs in seawater that already carries the nitrogen, phosphorus and carbon the plant needs.
This is not a marketing line. It is the main reason marine scientists take cultivated seaweed seriously as a food source. Both the WWF and NOAA describe farmed seaweed as needing no arable land, no fresh water and no fertiliser, which puts it in a different category from nearly every land crop and from fed aquaculture such as farmed salmon.
| Resource or input | Typical land vegetable crop | Farmed kelp |
|---|---|---|
| Arable land | Required | None, grown at sea |
| Fresh water or irrigation | Often required | None |
| Fertiliser | Commonly used | None added |
| Pesticides | Often used | None |
| Effect on surrounding nutrients | Can add run off (nitrogen, phosphorus) to waterways | Removes dissolved nitrogen, phosphorus and CO2 from seawater |
Two caveats keep this honest. First, no inputs at the farm is not the same as no footprint at all: hatcheries, boats, processing and refrigerated shipping all use energy. Second, the figures above are typical rather than universal, and they vary by crop and region.
Does farmed kelp actually store carbon?
This is where a lot of seaweed marketing goes wrong. Kelp does absorb carbon dioxide as it grows, quickly and in large amounts. The problem is what happens next. For that carbon to count as long term storage, the biomass has to end up somewhere it will not meet the atmosphere again for centuries, which in practice means sinking to the deep ocean. Food does the opposite: when you eat kelp, most of its carbon re enters the fast carbon cycle within months.
Where a farm sits matters too. A study of Norwegian kelp farms found that roughly 90 percent of the particulate carbon shed by the farm settled within about 4 km, close to the coast and the surface, where much of it is broken down again rather than buried. Broader reviews, including a 2024 state of knowledge assessment, conclude that the evidence does not support large scale kelp farming purely to sink carbon into the deep sea.
So we do not claim our condiments are carbon negative, or that eating them removes CO2 from the atmosphere. They do not, and any brand telling you otherwise is running ahead of the science.
So what are the real environmental benefits?
The credible benefits are about resources and water quality, and they are local rather than planetary.
As kelp grows it takes up dissolved nitrogen and phosphorus. In coastal areas loaded with run off from farming and sewage, that uptake can ease the nutrient overload that drives algal blooms and low oxygen dead zones, a service scientists call bioremediation. By drawing down CO2 in the water immediately around the farm, kelp can also slightly buffer local ocean acidification, which is one reason some shellfish growers site near seaweed. Farms add three dimensional structure to open water, which fish and invertebrates use as shelter and feeding ground.
The honest framing: these effects are real but site specific and modest in scale. They make seaweed a genuinely low impact food and a useful tool in the right coastal setting. They do not make it a replacement for cutting emissions on land.
How is Arctic winged kelp grown in Northern Norway?
Our primary ingredient is winged kelp (Alaria esculenta), one of the two species, alongside sugar kelp, that Norwegian research institutions such as SINTEF Ocean have focused on for food. It begins in a hatchery, where microscopic kelp is settled onto twine over roughly 6 to 8 weeks. The seeded lines are then set out at sea on ropes and left to grow through the cold months, drawing on nothing but daylight, cold clean water and the nutrients around them, before being harvested off the Helgeland and Lofoten coast of Northern Norway. Harvest falls in early summer, and the further north you go, the later it comes; on our own lines we harvest in early June. How much we bring in each season depends on demand rather than a fixed target.
The cold, clear Arctic water is not incidental. Slow growth at low temperature is part of what gives northern kelp its firm texture and clean, savoury taste, and the region's distance from heavy industry and dense agriculture supports a cleaner raw material. Winged kelp is also naturally rich in iodine, which is one reason we use it as a concentrated condiment in small amounts rather than as a bulk vegetable.
Where does the world's seaweed come from, and why does that matter?
Almost all of it comes from Asia. FAO figures put global seaweed and algae aquaculture at roughly 35 million tonnes a year, with Asia responsible for about 97 percent of production, led by China and Indonesia. Europe's share is small by comparison, and Norway's is smaller still.
That imbalance is exactly why a Northern European supply is worth building. A short, traceable chain from a named stretch of coast to a finished jar gives you provenance you can actually check, and it keeps processing and food safety standards close to the point of sale. It is a smaller and more costly way to make seaweed food. It is also a more transparent one.
Frequently asked questions
Is eating farmed seaweed better for the planet than eating vegetables?
At the growing stage, seaweed is one of the lowest input foods there is: no farmland, fresh water or fertiliser. A fair comparison still has to include processing and transport, and a jar of condiment is a small part of anyone's diet. Treat it as a low impact ingredient, not a way to offset the rest of your plate.
Does seaweed farming harm wild kelp forests or the seabed?
Cultivation is different from wild harvesting. The kelp is grown on ropes in the water column, not cut from natural reefs, so it does not deplete wild kelp beds. Well sited farms have a light seabed footprint, though like any farming, poor siting or very high density can cause local problems, which is why location and scale matter.
Is your kelp wild picked or cultivated?
Cultivated. It is grown from seeded ropes off Northern Norway, not harvested from wild stands.
Are all four flavours vegan?
Three of the four are. The Seaweed Pesto, the Sea Hummus and the Green Seaweed Puree (green curry) are vegan. The Red Seaweed Puree (red curry) contains fish sauce and is not vegan.
Does farming kelp take resources away from land agriculture?
No. It uses sea space, sunlight and seawater, so it does not compete for farmland, irrigation water or fertiliser. That is one of its clearest advantages.
Taste what cold water kelp does in food
If you want to see what Arctic winged kelp actually brings to the table, the Taster Pack is the low risk way in: one can of each flavour, including the three vegan options and the red curry.
The Taster Pack, all four flavours
One can each of the pesto, hummus and both curries. 299 NOK.
Shop the Taster PackNote on the science: the environmental points above summarise current, peer reviewed research and reviews. Carbon and water quality effects vary by site and farm design, and remain an active area of study.