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 and SeaGrow models). 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. Free-floating open-ocean farms remain part of our long-term vision for reaching gigaton-scale carbon removal once the technology matures. 

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.

By cultivating Sargassum we will be reducing the CO2 concentration in the atmosphere. By processing, Sargassum into biochar through our partners we will be locking away carbon for thousands of years. Throughout our work we will be researching, developing, monitoring and fine-tuning the best and most effective methods to sequester 1 Gt CO2 from the atmosphere each year without causing harm to the surrounding environment.

Yes. Whilst other businesses are also planning to operate in the open ocean, we are the only ones looking to simultaneously cultivate Sargassum and extract nutrients from the seaweed before sinking it. Seafields solution is also unique in using ‘Stommel pipes’ to provide a supply of fertilising nutrients to the Sargassum.

A Stommel pipe is a form of artificial upwelling, designed to draw up, or ‘upwell’, nutrient-rich water from the deep ocean to the sea surface. Stommel pipes are driven by buoyancy forces, generated by taking advantage of naturally occurring gradients in temperature and salinity which exist in the ocean (Stommel, Arons, and Blanchard, 1956). As they are driven by naturally occurring differences in temperature and salinity, Stommel pipes do not require a source of power to function, a major advantage over simply pumping water up from the deep ocean.

It’s difficult to visualise the scale of the problem of CO2 in the atmosphere. One gigatonne equals a billion metric tonnes. That is the equivalent to the CO2 emissions of Germany in 1990 or to the 276 million cars driven in the US, which release roughly 1.27 Gt CO2 per year. To return to pre-industrial CO2 levels in the atmosphere, about 1830 Gt CO2 needs to be removed, equivalent to the carbon in the entire biosphere.

Meeting the recent pathways laid out by the IPCC will require total cumulative net CO2 removals of 20-660 Gt CO2 by 2100, an endeavour that would need collaboration at a scale humanity has never seen before. The IPCC stated that “CDR is a key element in scenarios that limit warming to 2°C (>67%) or 1.5°C (>50%) by 2100 (high confidence)”.

In a study from 2019, an international research team found that we would need to plant 1.2 trillion trees (additional to the existing 3 trillion trees alive globally today) to take up the CO2 released in the last 10 years globally (Bastin et al 2019). The Land Gap Report found that the current climate pledges made by countries rely on an unrealistic amount of land-based carbon removals. Land for agriculture and other needs would have to go towards carbon sequestration, with negative impacts on livelihoods, land rights and ecosystems. The geopolitical challenge of this makes it practically unachievable. Lastly, trees take more time than seaweed to grow, and will be affected by droughts and fires.

The global ocean occupies more than 70% of the Earth’s surface, half of which is covered by the 5 subtropical gyres that are rotating lenses of nutrient-impoverished warm water. The Sargassum is retained by the closed circulation of the gyres. Additionally, Seafields is developing a floating barrier system to keep the Sargassum inside the farms.

By shifting activity away from the continental margins to the open ocean, we will be taking pressure off the biodiverse and unique coastal ecosystems, allowing them to recover. In contrast, the surface waters of the vast open ocean are comparatively homogeneous across large areas. Finally, the South Atlantic gyre is not crossed by major shipping routes or whale migration paths, and our farms will take up only a small fraction of the total area of the gyre.

The United Nations Intergovernmental Panel on Climate Change (IPCC) stated in its April 2022 report on mitigating climate change: “The deployment of carbon dioxide removals to counterbalance hard-to-abate residual emissions is unavoidable if net zero emissions are to be achieved.” Alongside using CDR methods to reach net zero, we need to scrub already existing historic CO2 emissions as well. This needs to be done quickly, to avoid reaching key climate tipping points. Current efforts are focused on cutting the 50 Gt CO2 we emit each year, but little thought is given to sequestering the ~1830 Gt CO2 post-industrialisation emissions that remain.

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.

Carbon reduction or reducing carbon emissions is the process of avoiding greenhouse gas being put in the atmosphere or reducing the amount of output.

Carbon capture is a method which catch carbon dioxid emissions directly at the source of pollution like power plants or industrial factories. This captured carbon can either be stored in depots underground or be reused, thereby reducing the amount of carbon emissions that would go into the atmosphere.

Carbon removal is the process of actively removing the carbon already in the atmosphere (often called historic emissions) and storing it permanently. It goes one step further than carbon capture and is vital for tackling the climate crisis since we need to bring atmospheric carbon dioxide concentrations back down from currently 420 ppm to pre-industrial levels of 280 ppm. Seafields approach is to tackle these gigatonnes of carbon dioxide (1 ppm CO2 equals 2.12 gigatonne of CO2) by converting it into Sargassum biomass and biochar.

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.

As carbon is removed from the ocean, we will need to verify that this leads to carbon removal in the atmosphere. When there is a difference in CO2 concentration between the surface ocean and the atmosphere, this difference will be balanced out, however not instantly – it is a process that takes months to years. To estimate how much of the CO2 taken out of the ocean is then pulled from the atmosphere back into the ocean, we need detailed measurement of CO2 concentration in the water and air in our farms. This, paired with modelling of how long the water parcels leaving our farm stay in contact with the atmosphere, will tell us how much of the carbon sequestered by our aquafarms can be considered sequestered from the atmosphere.

Our science team has extensive experience in monitoring climate change impacts in the carbon and nutrient cycles in the open ocean. They are aware of the challenges that ocean CDR Measurement Reporting and Verification (MRV) pose (e.g. accuracy of partial pressure of carbon dioxide (pCO2) measurements, considering the dilution of the signal, etc.) and are planning to use international monitoring networks (e.g. Argo floats, sail drones and satellites) as well as developing novel tools to improve the monitoring resolution for large scale operations. Using a combination of water and air sensors, we will monitor the air-ocean CO2 influx in our farms and control sites.

Seaweed and kelp do not attach to soil, most attach to rocky substrates. The Sargassum natans and fluitans that we work with are free floating for their entire life cycle. Therefore, the above statement is a bit misleading and confusing.

While mangroves and seagrasses sequester carbon in the soil right below them, when their leaves or blades fall off, seaweed and kelp biomass is moved to either these same coastal soils and sequestered there or moved to the deep sea. While the infinite ability of the mangrove’s soils to sequester carbon is a huge advantage and makes these soils far superior to terrestrial soils, which have a maximum amount of carbon they can sequester, this does not disadvantage seaweed sequestration. Seaweed sequestration is done either in the same soils as mangrove and seagrass sequestration or in the deep sea where carbon is locked away for much longer and better protected against being dredged up.

Mangroves sequester about 7 tonnes CO2 per hectare per year (Alongi, 2020) while the Sargassum in our farms will sequester about 107 tonnes CO2 per hectare per year. Therefore, per unit area the fast-doubling rate of Sargassum is able to produce much more sequesterable biomass than mangroves. We plan to sink this biomass to the abyssal plain. In terms of permanence, deep sea sinking is highly advantageous compared to the soils of the mangrove forests, as sequestration rates for 1000 years can be guaranteed while mangrove soils have to be protected against being destroyed for other uses such as hotel, housing and shrimp farm construction.

Another advantage of working with Sargassum, as mentioned above, is that it is free-floating. As such, it does not need to attach to rocks, unlike other seaweeds, nor does it require soil to grow, unlike mangroves and seagrasses. This makes it possible for Sargassum to grow in the open ocean which covers a much bigger area than the shallow coastal waters suited for growth of mangroves, seagrasses and benthic seaweeds.

Each project using blue carbon plants has a vital part to play. We need mangrove and seagrass restoration and protection projects as well as seaweed farming. The colossal task of removing CO2 from the atmosphere needs all hands on deck.

Compared to other sinking biomass approaches (e.g. phytoplankton or loose seaweed biomass), the amount of carbon sequestered in our bales is easy to monitor by weight and carbon content. The two main challenges are to estimate the amount of CO2 taken out of the atmosphere and the remineralization rate of our bales at the deep sea. To monitor atmospheric CO2 uptake at the ocean surface we will use pCO2 sensors. In addition, we will monitor temperature, salinity, pH, current speed, and oxygen in situ with our fully equipped CTD (Conductivity-Temperature-Depth Probe). The deep-sea depots will be equipped with cameras and oxygen sensors to assess macro and micro benthos consumption. All this will give us a precise indication of the fate of the biomass in the deep sea.

Our lab results show that Sargassum processed for nutrient recovery decomposes slower than fresh Sargassum, which will lead to less remineralization of our bales compared to Sargassum that sinks naturally. This, together with the fact that on tightly compressed bales the amount of space for bacterial remineralization will be significantly reduced, suggests there will be negligible remineralization rates of the carbon stored in the bales in the deep sea. Recent studies have shown that remineralization rates in the deep sea are much lower than previously reported (Amano et. al., 2022). Furthermore, on the Sargasso Sea floor, four times more Sargassum is found than at the surface (Baker et, al. 2018), indicating a long-term accumulation of biomass that is not consumed. The small percentage of remineralized CO2 that does occur, would take an average of 900 years to reach the surface of the ocean. Until then it is locked away (Siegel et. al., 2021).

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. 

When we talk about the Great Atlantic Sargassum Garbage Patches, we’re referring to a future state where Sargassum farms are deployed in the South Atlantic gyre where one of these garbage patches accumulates. The idea is that these farms, over time, will become hubs that both grow floating Sargassum into a managed resource and act as collection points for plastic that naturally accumulates in those gyres. 

In this context, the plastic removal is largely passive: as the farms hold the drifting Sargassum, they also catch floating plastics that are found in large amounts in the gyre. Sargassum mats are known to trap plastic so more plastic will stay stuck in the Sargassum farms than floating away from it. Once collected, the plastics will be separated from the seaweed, cleaned, and sent to partners for recycling or upcycling, while the Sargassum itself is processed for its many uses. 

This concept is still at a visionary stage, our current work is focused closer to shore, intercepting harmful influxes, but the long-term ambition is to use our Sargassum aquafarms to trap floating plastic and turn them into managed systems that remove waste and create value rather than damage. 

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.