Why Should I Care About Seaweed?

Hamish Richardson
8 min readJan 31


This week’s deep dive is an attempt to explain why I’ve been pitching scaled European seaweed to anyone that would listen: friends, family, partner, taxi drivers etc. I first came across seaweed in a meaningful way while spearfishing, imersed in the beauty of these swaying kelp (seaweed) forests –something I didn’t even know existed until I started exploring the Cornish coast from the water. This interest grew once I read Eat Like a Fish (Bren Smith’s regenerative seaweed farming bible, and sometimes nuts autobiography) by my seaweed farmer friend (shoutout George, fighting the good fight at Biome Algae).

It’s worth noting from the top that while seaweed hasn’t hit the scope or scale of its potential, it isn’t a new concept. Taking from Bren Smith (this’ll be a recurring theme): “In the eighth century, Islamic scientists extracted the compound Algin from a brown seaweed, and used it to fireproof boats; today, firemen’s clothing is still treated with alginate for fireproofing.”

The global seaweed market tripled from 2000–2018, reaching 32.4 million tonnes with a value of $13.3 billion USD. This is estimated to grow at a compounding annual growth rate in the double-digits over the next 5–10 years.

Ultimately, I’m interested in the untapped potential of seaweed as a driver of carbon avoidance, carbon capture, as well other ecosystem services.

How is seaweed farmed?

Seaweed is farmed, and has been farmed for centuries, at different scales and with different processes. There are seaweed foragers that harvest wild seaweed, artisan seaweed farmers with no wish for scale, as well as farms with the ambition to scale around Europe’s coastlines and onto the high seas.

To avoid me spending my weekend plagiarising GreenWave (Bren Smith’s restorative ocean farming organisation) or Cascadia’s (company scaling seaweed farming in Canada) farming model, I’m going to do a bit of both.

GreenWave’s process of developing a restorative 3D ocean farm — US focus but GreenWave have authority on the restorative (this means the farm is regenerating its ecosystem not damaging it) ocean/seaweed farming:

  1. Lease: Since oceans have common ownership, land is leased not owned, therefore a farmer owns the process not the property.
  2. Permit: Permitting is often described as the hardest and longest part (8–15 months referenced in US). Stakeholders are consulted, from harbourmasters, to tour boat operators, to environmental groups.
  3. Build: A grid system is created with anchors, ropes, and buoys. Anchors are on ocean floor, with vertical anchor lines running up to a buoy, with horizontal lines 6-feet below the surface between the anchor lines.
  4. Seed: GreenWave’s regenerative farm encourages multi-crop (seaweed, oysters, mussels etc), but the core is seaweed, which can be bought as spools of seeded string. See how this is created in the below video.
  5. Maintain: Seaweed needs a balanced amount of sunlight and nutrients. This can be managed by line depth and positioning.
  6. Harvest: Kelp grows, and therefore can be harvested, all year round. However, its qualities (e.g., taste) will change and therefore may be harvested for different reasons.

Cascadia’s farming process:

While these are two different farming styles, the same challenges reoccur. Permits are a challenge to growth, especially in countries with rigorous environmental governance including the US and UK. While this is a good thing, this needs to be balanced with a favourable environment for farming. Seaweed farming also involves high manual labour, amounting to 75% of costs for farms. While this provides jobs, this is an unsustainable job-to-scale ratio as farming operations scale. It’s worth noting than Asian seaweed farming countries achieve scale inefficiently because of the availability of cheap manual labour, not to mention low working standards. Finally, non-specific farming equipment is a challenge for an industry catching up with the progressive farming techniques of terrestrial cousins.

I always like to mention innovating startups and companies where I can, so I’ll continue this trend by mentioning Samudra, who are creating AI & robotics for the seaweed farming industry. Their first product is tech to remotely monitor seaweed farms, so watch this space! I’ll also note industry incumbents AtSeaNova, a Belgian company providing tech to seaweed farmers, including a floating machine that can seed, harvest, and clean seaweed. Other notable innovators are those trying to bring seaweed farming offshore, something that would open the vast oceans as potential seaweed farms, including the Climate Foundation, a US charity exploring floating seaweed farms off the Philippines, and Ocean Rainforest, a Faroe Islands company (supported by WWF).

What can we do with all this seaweed?

To give you a flavour of the potential for this amazing plant, I’m going to rattle through a fraction of the commercial uses of seaweed.

Human food — While seaweed is enjoyed around the world, it’s eaten in vast quantities across Asia. In Japan, 20% of meals include seaweed, which amounts to 1.2 million kilograms of seaweed eaten per day. While there’s a history of European seaweed consumption, from Welsh laverbread, to Icelandic söl, to Catalan u mauru, it’s not yet taken off. Check out BettaFish, making plant-based tuna out of seaweed.

Carrageenan — Worth a mention in its own right, carrageenan is an additive used to thicken and preserve foods, drinks, cosmetics, and drugs. It’s extracted from various red seaweeds. Seaweed deserves some respect for carrageenan considering it’s used to control the melting of ice cream.

Animal feed — Seaweed has been used for animal feed in the Orkney Islands, Scotland, for at least 5,000 years. For sheep and cattle, it created a unami-rich meat. Also, there’s a GHG impact, as it has been found (James Cook University, 2016) that “the addition of a small amount (less than 2% of the total feed) of a macroalgae called Aspparagopsis taxiformis reduced methane production by 99%” (thanks Bren).

Fertiliser — Seaweed is an age-old organic fertiliser, rich in nutrients including nitrogen, potassium, phosphate and magnesium. Since 85% of fertilisers eventually end up in our oceans, rivers, and lakes, it makes sense to use a circular product — while kelp still releases nitrogen as a fertiliser, it also captures it when farmed.

Biofuels — Approx 50% of seaweed’s weight is oil, which can be used for vehicle biofuel. Putting it’s potential into perspective, seaweed biofuel yields up to fifty times more energy per acre than other crops like corn. However, kelp biofuel is yet to be commercialised. Also, researchers at the Georgia Institute of Technology have found an alginate, extracted from seaweed, can improve the storage power of lithium-ion batteries by a factor of ten.

Bioplastics — Companies like Notpla, which recently won The Earthshot Prize, are creating seaweed based biodegradable packaging.

Hot topic: seaweed for carbon capture and storage

The question of seaweed as a vessel for carbon capture and storage is an age-old tale of innovation on the brink of breakout. On one hand, seaweed has a massive carbon capture potential, estimated at 173 million tonnes of carbon per year, and on the other hand, no one has cracked the storage part yet.

It’s a hot topic. When I talk to my friends about seaweed, they seem to have heard it grows at a mythical 7m per day, and that we’re on the brink of turning every available metre of the world’s oceans into seaweed carbon farms. While I’m very excited about the future of seaweed, I would point people to a recent podcast with Dr Thierry Chopin — Seaweed’s role as climate solution, Hype vs Science — where he balances counterproductive hype with considered science-based progress.

Also, because why not, here’s Thierry’s ice bucket challenge:

Explaining the simple science behind seaweed’s carbon capture — through photosynthesis (the same as plants and trees on land) the seaweed uses sunlight to grow and capture carbon from the atmosphere. Once the seaweed has captured its maximum capacity of CO2 (approximately six months), it’s harvested, and the carbon is captured in the seaweed’s biomass to then be permanently stored somehow.

This is when it gets tricky, with companies across the board struggling with storage. In my limited research, there are two possible ways of storing this carbon.

  1. Biochar — Biochar is a solid charcoal like substance, created when organic biomass is heated to temperatures of 250°C in a zero-oxygen environment. This solid carbon-rich substance can then be used as a fertiliser on soil, sequestering carbon for approx. 2,000 years. Check out this paper on commercial seaweed for biochar.
  2. Sunk biomass — Harvested seaweed is collected, contained, and sunk to the bottom of the sea at depths of 1,000 metres. At such depths, the material resides and is captured in the seabed sediment. Check out Running Tide in Maine, US.
  3. Other? — If anyone knows of any other methods, envisaged or otherwise, of storage please let me know.

I’m not going to go into detail here, but there are differing opinions on the net carbon capture of seaweed. For example, one paper notes that seaweed ecosystems may not mitigate CO2 emissions if you look at the whole ecosystem they contribute to (e.g., invertebrates consume organic matter and produce CO2).

Ecosystems services

I’ve run out of time to do this section justice — maybe this needs a whole blog to itself at some point — but I’d just like to point out that seaweed farming provides vast ecosystem services.

If interested (everyone should be!), check out BlueCs, which is a startup monetising ecosystem services so they can be traded , with revenues redistributed to the producers operating the regenerative practices generating the ecosystem services.

Here are a few. I would have liked to write more on this, but I’ve run out of time and my fans need their weekly blog.

Who is investing in seaweed?

European investment in seaweed is growing, increasing 24x from 2010 (€900k) to 2020 (€21.6m).

Most of this is in early-stage financing, in the form of grant funding, angel investments, and venture capital companies (VCs). As the industry matures, transactions will evolve from mainly venture capital funding to later-stage private equity and debt funding, traditionally reserved for larger sums and more mature businesses.

Venture capital (VC) and private equity (PE) — VCs and PEs have been particularly interested in companies with high value-add products, deploying more than 90% of capital to consumer goods / value add goods companies, especially in bioplastics and pharmaceuticals. For example, Astanor Ventures invested £4m into Notpla.

Accelerators & Incubators — Business model of providing sweat equity (equity for business advice and support) as well as potential for investment, there are many accelerators & incubators in Europe investing in seaweed. For example, Norwegian Katapult Ocean incubated Oceanium.

Grants — Public entities remain among the biggest investors in the European seaweed space, playing fully the role of catalytic capital. These public entities are either: Supra-national bodies (European Union’s European Maritime and Fisheries Fund); National entities (UK’s Innovate UK); or Subnational bodies (UK’s Cornwall & Isles of Scilly Investment Fund).

Corporates — Corporates investing in seaweed are doing so to secure a sustainable supply in an increasingly competitive landscape (for example, Orkla investing in Arctic Seaweed), as well as develop value-add products (for example, Unilever investing in Lactam).

I’m glad to see the UK putting its money where its mouth is — taken from Seaweed for Europe

Thanks to Seaweed for Europe — coalition seeking to accelerate and scale the European seaweed industry by driving innovation and investment, led by Systemiq — for their report, Investor Memo — The Case for Seaweed Investment in Europe.

For those looking to dig some more, this is a useful tool mapping seaweed investors: Phyconomy Database

If you’re looking for investment or to invest in the seaweed space, please get in touch (add and message on LinkedIn). I’ve been researching and networking within the seaweed space for some months now, so am happy to chat and make relevant introductions.