Frequently asked questions

Seafields is a UK-based aquaculture company in the Caribbean, turning the challenge of Sargassum seaweed into a powerful global climate solution. We are, to our knowledge, the only seaweed farming business able to capture problematic blooms and preserve their freshness year-round in our unique floating Algaeponix paddocks, removing supply chain uncertainty entirely. This provides bio-based product manufacturers with a dependable, traceable, sustainable feedstock to underpin their green premium. Through our SeaClear model, we intercept and cultivate vast quantities of Sargassum, safeguarding marine ecosystems, driving a circular blue economy, and delivering large-scale, measurable carbon removal.​

Sargassum is a genus of seaweed, best known for its two floating species, Sargassum natans and Sargassum fluitans. Sargassum grows in large mats in the Sargasso Sea, in the north-west Atlantic Ocean. Unlike other species of seaweed, they are free floating during their entire lifecycle and never attach to the seafloor or other hard surfaces. They do not have holdfasts (akin to roots) and self-reproduce at a fast rate. It has small air-filled ‘bladders’ that allow it to float like islands in the sea. Carbon amounts for around 30% of the mass of dry Sargassum. In its natural distribution area, Sargassum is an important habitat for marine life such as shrimps, crabs and sea turtles, eels plus larger fish species such as tuna and marlin.

In 2011, Sargassum from the Sargasso Sea was transported to the equatorial region of the Atlantic Ocean, where it grew in nutrient-rich runoff from newly-established agriculture in the Amazon River basin. This created the perfect environment for Sargassum to proliferate exponentially, creating additional large mats in the tropical Atlantic. Sargassum has now been established in The Great Atlantic Sargassum Belt, extending from the Caribbean Sea all the way to the west coast of Africa.

Each year, starting around April, the seaweed blooms and travels on currents towards the Caribbean and Africa where it washes up on beaches in vast quantities, making it very difficult to manage. Without proper infrastructure and funding many beaches are engulfed in the algae, where it is often left to rot in shallow waters – damaging eco-systems, driving away tourists and releasing sulfuric fumes.

Our marine infrastructure enables us to catch, cultivate, and harvest Sargassum at sea, before it reaches shore, unlocking its potential for carbon sequestration and sustainable industries. By converting Sargassum into biostimulants (a natural fertiliser that enhances crop growth) and a feedstock for biomaterials (such as bioplastics and biofuels), we are building a circular economy for the future. ​

We aim to sell 100% of the biomass. Unsold material will be converted to biochar, with carbon credits pre-sold. The global biochar market operates entirely on forward contracts—none of it sells on spot markets—giving us high confidence in this fallback revenue stream. 

No one is seriously farming sargassum yet because it's perceived as waste. Most market players still focus on kelp or benthic species. But we’re showing that sargassum can be grown and harvested year-round, turning a waste problem into a value opportunity. 

In May 2023, we pivoted our core focus from free-floating open-ocean aquafarms to nearshore moored aquafarms (our SeaClear model). Initially, our R&D efforts had been directed toward free-floating farms, as stationary Sargassum cultivation was widely considered challenging. However, trials in April/May 2023 demonstrated that we could successfully grow and maintain healthy Sargassum in a fixed system. This discovery opened new opportunities: nearshore farms simplify operations at this early stage, reduce risk, and allow us to address shoreline Sargassum management immediately.

In the summer of 2024, we also adjusted our approach to carbon credits. Whilst we continue to believe in the long-term potential of macroalgae-based carbon dioxide removal (CDR), the current investment climate is not yet ready to support the rigorous validation work required. The bankruptcy of Running Tide and Puro.earth’s decision to exclude aquatic biomass from its methodologies highlighted that near-term funding and market appetite for open-ocean carbon sinking are limited. 

Rather than stall, we chose to focus on the immediate opportunity offered by turning Sargassum biomass into valuable products. Within a month of that decision, we partnered with a biochar company (enabling a zero-waste approach, in which we also generate biochar carbon credits); within six months, we secured our first pulp offtake agreement and recently we signed an LOI for biostimulants. In parallel, we are maintaining our collaborative CDR research so that, as standards evolve, we can resume generating sinking-derived carbon credits. Biochar credits, by contrast, already have established methodologies and so can go to market immediately. 

In short, this is not an abandonment of carbon removal, but a strategic redirection to build multiple revenue streams whilst continuing to develop the science and methodologies that will underpin future carbon credit revenues. This new direction is further reinforced by our unique value proposition as the only supplier able to provide a year-round, consistent supply of Sargassum biomass to industry, an immediate gap in the market. 

As you rightly identify, the hurricanes which pass through the Caribbean each year posed a key design challenge to our Engineering Team when developing Seafields in-water hardware. It should be said first of all that in the event of any extreme weather or natural disaster the safety of our team members is always the top priority, and as such if we have to forfeit any assets to ensure this, then we will do so. That being said, all our in-water hardware (i.e. both our AlgaePonix paddocks and deflection barriers) is designed as an assembly of modular sections, allowing a full SeaClear farm to be disassembled by our ground teams within 24-48 hours warning of incoming extreme weather. The floating, surface-level elements can then be towed onshore, where they are stowed safely in containerised storage depots, whilst the seabed moorings can be left in-situ, protected by the depth of water above them. This will, of course, necessitate losing our standing stock of Sargassum, however in the event of a hurricane the seaweed is typically lost anyway, as the large waves push it so deep beneath the surface that it becomes negatively buoyant and sinks. In addition to the above, our in-water hardware has been rigorously designed to operate in a wide range of expected sea states, and as such in scenarios less severe than a direct hit by a hurricane it may often be possible to leave the paddocks and barriers in place, trusting that they will not be pushed beyond their intended design limits. In the event that damage is sustained by the in-water hardware, we have designed all our technology such that certain, less durable components can be easily repaired/replaced by local ground teams, ensuring an anticipated in-service lifespan of in excess of 5 years. 

Studies have shown that the levels of toxic elements are below the legal limits required for use in both the EU and the US, as these elements are removed during the reverse osmosis process. Throughout the filtering stage, all materials are tested to ensure full compliance with relevant regulatory standards, allowing us to certify that our products are safe and approved for agricultural use. For Nitrogren it is a macronutrient for plants and algae. Some of the nitrogen is pressed out of the Sargassum and ends up to be an ingredient in our biostimulant. 

Since 2011, a new Sargassum area has formed, the Great Atlantic Sargassum Belt. This is what is considered the excessive bloom as it is a large amount of Sargassum that previously didn't exist. This area is separated from the Sargasso Sea where Sargassum has been occurring in large quantities for centuries and where Sargassum in protected. Due to the separation in location, we can say with 100% certainty that the Sargassum we work with is from the Great Atlantic Sargassum Belt. However also in the Great Atlantic Sargassum Belt, the Sargassum is a habitat for marine life while it is floating offshore. So the excessive bloom has positive impacts as well as negative ones.  

All negative impacts occur when Sargassum gets close to shore and beaches. Decomposition of Sargassum on the shore creates brown tides and Sargassum debris that is pulled back into the ocean, this can kill seagrass beds, coral reefs, mangroves and marine animals. It also releases hydrogen sulfide gas and methane, one toxic to humans, the other a potent greenhouse gas. Nesting sea turtles and their babies also struggle to utilize beaches inundated with Sargassum.  
 
Our barriers and aquafarms are installed just in front of beaches to prevent the beaching of the Sargassum. The Sargassum we harvest will have beached otherwise and lead to severe negative environmental impacts. Currently hotels that have Sargassum barriers installed have what they call sacrifice zones on the end of their barrier where they let Sargassum accumulate on the beach and have negative effects on the environment. We can install our SeaClear farms in that area and intercept that Sargassum, keep it alive and fresh until it is needed for production of useful and sustainable goods. As such that sacrifce zone will turn into a biodiversity hotspot as our farms attract fish and other marine life in a similar way as Sargassum mats do offshore.  
 
By storing Sargassum in the water as part of our operational approach, Seafields solutions are the only ones which provide a lasting habitat for marine life and therefore not only avoid significant negative environmental impacts but add positive ones. Other remediation/management solutions simply seek to remove Sargassum from the water as rapidly as operationally possible, leaving nowhere for displaced marine life to go. By contrast, any marine life disturbed by Seafields harvesting operations can simply move into the AlgaePonix paddocks (if it is using intercepted Sargassum at the barrier as a habitat), or can move into a different section of the paddock if it is found there, with these paddocks harvested using a 'strip-farming' type approach for exactly this reason. 
 
Sargassum that accumulates behind conventional barriers is typically compacted by wave action, which reduces its value as a habitat for marine life and in some cases even leads to areas with low oxygen content that are detrimental to marine life. By contrast, the Sargassum managed in our AlgaePonix paddocks retains a structure much closer to the natural floating mats found in the open ocean, offering a far better refuge for marine organisms. This makes our approach far more ecologically beneficial than traditional barrier-based solutions. 

Over the next two years we anticipate the majority of our revenue will come from Sargassum management fees. The main reason for this is that Sargassum is still a new feedstock and it takes time for industries that can use Sargassum in their products to change their supply chains. It's a feedstock that's exciting many manufacturers, but still in lab stage of testing for most of the customers in our pipeline. As these progress from lab to factory the orders will increase exponentially, and therefore from 2027/8 we anticipate most of our revenue will come from selling biostimulants, dried seaweed pulp and the refined polysaccharides, alginates and fucoidans (we don't produce these directly but we are in conversations with several partners about revenue share opportunities). We anticipate that carbon credits will always be less than 10% of revenue, but there is a good reason for this. If a customer buys the dried pulp from us, they will most likely want to claim the environmental benefit in their product lifecycle assessment, so if we also sell a carbon credit from the same tonne of seaweed, that would equate to double counting. As such, it's only the low quality Sargassum, waste from other processes and unsold Sargassum pulp that we intend to convert into biochar. Also to be clear, the environment has received the benefit of an carbon emission avoidance or carbon dioxide removal whichever pathway our Sargassum ends up in. 

The harvesting methods we will employ have been developed in collaboration with marine biologists from local universities and have been found to have minimal bycatch. Most mobile animals that live in the Sargassum mats leave these mats as they get closer to shore and of the ones who are still in the mat, most swim away from the harvesting device. Animals that are attached to the Sargassum will be harvested as bycatch, these are bryozoans, hydroids, encrusting worms and nudibranches. Similarly, amphipods and copepods that are less than 2mm long will also be found regularly as bycatch. It is important to note that the few species that are bycatch of the removal methods would have also beached with the Sargassum and died onshore.  

Regarding the design life of our SeaClear farms, we are currently working with an assumed lifespan of 5 years. The ocean is a notoriously harsh environment in which to deploy infrastructure, and we have therefore made this conservative assumption at this stage to ensure the robustness of our financial projections. In reality however, we hope to achieve an in-service lifespan of closer to 10 years, and have designed all our infrastructure such that certain, less durable components can be easily repaired/replaced by local ground teams to extend the design life. The cost of this ongoing maintenance, as well as regular cleaning and inspections which help further extend the design life, is budgeted into the service package we offer to the aforementioned clients.

Once harvested from the water, the Sargassum is transported by truck to our local clients.  For international clients, we dewater and dry the  Sargassum biomass and then containerised for efficient shipping. Initially, we will transport these containers via ocean freight to end-user companies. While shipping does generate emissions, our LCA (life-cycle assessment) for the biomass will take into account the emissions released by shipping, and, whilst this does offset some of the green-benefits of our feedstock, it is still significantly better for the climate than the alternatives. Logistically, shipping containerised Sargassum from the Caribbean back to Europe (where our initial off takers are likely to be sited) is simplified by the fact there are a great many empty containers travelling back out of the Caribbean through the US (thanks to the import surplus of these island nations). In time, as the value chain around Sargassum scales, we anticipate many of the product companies will establish facilities in the Caribbean (and many are already developing plans/costed proposals to do so), simplifying the logistics and vastly reducing the cost/emissions from transport. Plus many of our existing partnerships are with companies based in the Caribbean, enabling simplified transport.

The original idea for the offshore aquafarm came from leading oceanographer and emeritus professor Victor Smetacek. Victor was former Head of the Pelagic Ecosystems Division of the Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research in Bremerhaven, Germany, and has published over 20 papers in Nature and Science. He shared his idea for an offshore aquafarm in an interview with The Sargassum Podcast, co-hosted by Dr. Franziska Elmer and Dr. Mar Fernández-Méndez.

Serial entrepreneur Sebastian Stephens, founder of SubSea Environmental Services came across this podcast episode while investigating sustainable fuel for a new airline for island nations. He immediately saw the potential of Victor´s vision and got in contact with him. Soon after, Sebastian assembled a team that included Victor and other experts passionate to bring this vision to life, including Dr. Mar Fernàndez-Méndez and Dr. Franziska Elmer. And so, Seafields was born.

The company’s executive team is composed of leading global scientific and business figures including John Auckland, an experienced entrepreneur who has helped more than 100 companies raise over £60m in investment funding; Randall Purcell, who managed the UN Food Programme’s largest climate adaptation programme and has 25 years' experience at the World Bank and the UN; and Erick Contag, a senior figure in the sub-sea business community.

​We have deployed test farms in St. Vincent and the Grenadines and are now focusing on Antigua and Guadeloupe and other Caribbean islands. ​​

Seafields operations are led by science, though experienced scientists with diverse expertise that build the core strength of our team. Additionally, we seek the advice of an independent Science Advisory Board, comprising preeminent experts in the fields of marine chemistry, biology and ecosystems, from leading research organizations and universities, including the GEOMAR Research Institute at the University of Kiel, the German Centre for Marine Biodiversity Research at the Senckenberg Research Institute and the Alfred Wegener Institute for Polar and Marine Research.

Seafields is part of a broad coalition of Ocean Carbon Dioxide Removal (CDR) researchers and practitioners that has come together under the guidance of Ocean Visions, a collaborative Ocean CDR incubator, that supports innovators competing for Elon Musk’s US $100 million XPRIZE. We are a member of the United Nations Global Compact Safe Seaweed Coalition and the industry sustainability-focused World Ocean Council.

We are a signatory to the United Nations Sustainable Ocean Principles and we are also working with a number of industry partners, including Carbonwave, the largest processor of Sargassum (in which Seafields owns a small stake), the engineering firm 2H Offshore, the large engineering construction firm NOV, and the chemical company BASF through a collaborative Sprin-D grant awarded by the German government. A number of informal Seafields advisors occupy high level positions in industry and policy circles.

Seafields was named by globally popular British music band Coldplay as an associated organisation to support the band’s efforts to make its upcoming tour as sustainable and low-carbon as possible. Coldplay has stated that it will put 10 percent of everything it earns (touring, records, publishing, etc) into a good causes fund. These funds will be split between environmental and socially conscious projects and charities, which includes Seafields.

We are also partnered with various Sargassum focused biorefineries and product companies Carbonwave, Macrocarbon, RubisCO2, Origin by Ocean

And have project partnerships with Montrose Investment Holdngs in SVG.

Aquaculture on the open ocean will open up a new sector for economic growth, generating revenue and healthy jobs, the biostimulant, bioplastic and biofuel markets are set to grow considerably up to 2030.

To reach 1 Gt of CO2 sequestered each year, we need to harvest 14 million tonnes of Sargassum a day, which is almost the entire biomass of the Great Atlantic Sargassum belt (at its yearly peak). In order to harvest 14 million tonnes of Sargassum a day, we need to create a Sargassum stock that is about 300 million tonnes, of which we can harvest the daily growth.

The Sargassum in the Great Atlantic Sargassum Belt is dispersed over large areas and harvesting the parts that are not near a coast is costly and the fuel required to power the ocean vessels would emit a lot of CO2. While it is possible to determine the fate of Sargassum that is located near shore and only remove what would have landed on beaches and emitted greenhouse gasses, it is not possible to know what the fate of Sargassum far away from the coast would have been – whether it would have sunk naturally or beached – without the intervention.

Sargassum farms will provide a steady source of raw material for companies such as our partner, Carbonwave, for use in a range of products like bioplastic and fertilizer, to secure contracts for their products and employ more people. There are no other companies trying to farm Sargassum, we are therefore a pioneer filling an important niche.

Our barriers are the first to contain Sargassum and will keep the seaweed inside the farms. We recently tested the first barrier prototype off the coast of St. Vincent and are confident of its ability to contain Sargassum even in difficult seas. Our monitoring technologies (GPS and drones equipped with sensors) will make the tracking of our farms possible even under tough conditions.

From our initial trials we don't foresee adverse issues with large marine life entanglement since our structures are flexible, but we will monitor this with underwater cameras in the prototype farms. We are also working on systems to prevent any surface bycatch of smaller marine life.

Our sector would welcome this. We are delivering best practice and would want to support the Article 6 developments to ensure that they drive quality and integrity from the top down.

We are aware of the growing challenge posed by Rugulopteryx okamurae along the southern coast of Spain, and one of our scientific advisors recently highlighted the same research regarding the scale of biomass accumulation from this invasive species. The situation described by the local authorities there is highly reminiscent of that encountered across the Caribbean, with many of the same negative social, environmental and economic impacts experienced in both locations. 

At Seafields, our work to date has focused on free-floating Sargassum in the open ocean. There are important differences between these species that influence our approach: 

• Rugulopteryx is a benthic (bottom-attached) alga, whilst Sargassum is pelagic (free-floating). Our current interception and cultivation systems have therefore been tailored toward the challenges of working with free-floating biomass and might not offer the same performance for a benthic species. 

• Research into Rugulopteryx utilisation pathways is still limited, and its high levels of secondary metabolites, many of which are toxic and bioactive, make it more complex to process into safe, green products. By contrast, Sargassum offers a clearer route to sustainable outputs such as biochar and biostimulants. These pathways avoid landfill entirely, ensure full use of the biomass, and even contribute to long-term carbon removal. 

That said, we are open to exploring pilot deployments of barrier or interception technologies to capture Rugulopteryx as it becomes detached and drifts toward beaches, and (without detailed research) it is likely that a modified version of our current systems could achieve significant impact on the situation in southern Spain. For a genuinely zero-waste solution, however, further work with our scientific team would be essential to study this species in more detail and identify safe, scalable uses for its biomass. 

Health risks from Sargassum arise from gases released as it decomposes. When large amounts wash ashore and begin rotting, they emit hydrogen sulfide (H₂S) and ammonia, which can irritate the eyes, nose, and throat, and at higher concentrations, cause breathing difficulties or exacerbate existing heart and lung conditions.  

At Seafields, our model prevents these risks. We intercept Sargassum whilst it is still fresh and floating at sea, when it cannot produce harmful gases, and process it shortly after collection. This ensures it won’t reach the shore to decompose and impact local communities, underlining the urgent need for a scalable solution to the Sargassum crisis.  

Those most at risk include coastal residents, workers handling beach clean-ups, people with asthma, COPD, or cardiovascular disease, as well as children, older adults, and pregnant women. This reinforces why current beach clean-ups are neither sufficient nor sustainable, and why our in-water storage solution will be transformative for Caribbean islands. 

Safety is at the heart of our operations. We follow strict testing and procedural controls to ensure the highest level of protection for all staff working with Sargassum at any stage of processing. 

All other problematic seaweed species suffer from seasonal supply. We’re the only company globally that can deliver year-round supply of problematic seaweed—a massive competitive advantage in sustainability-driven markets. Most material companies (e.g. sustainable textiles) don’t want farmed kelp—they want impact-driven stories, and we’re the only ones who can provide them.