Caribbean Special Report

Seaweed Biostimulants in the Caribbean: How Sargassum Is Becoming a Soil Treatment

A Dominican Republic company is intercepting the seaweed choking Caribbean beaches at sea and processing it into certified organic biostimulants, displacing petrochemical fertilisers, employing coastal fishermen, and building the region’s first blue biotech supply chain from a problem nobody else wanted.

37.5 Million Tonnes: Why the Caribbean’s Sargassum Crisis Is Getting Worse

In 2025, more than 37.5 million tonnes of sargassum were recorded in the Caribbean, a volume exceeding the combined global production of all seaweed species. The brown, free-floating algae has become one of the region’s most costly environmental problems, fouling beaches, killing marine life, releasing toxic hydrogen sulphide gas as it decomposes, and draining the tourism revenue that dozens of island economies depend on. As water temperatures rise and agricultural runoff continues to feed the Great Atlantic Sargassum Belt, the volumes are not expected to fall.

Most governments have treated it as a disposal problem. Elena Martínez, a Spanish oceanographer with two master’s degrees in applied blue biotechnology, decided it was a supply chain. The same pattern is unfolding in Barbados, where a UWI spin-off is converting sargassum and rum distillery wastewater into Bio-CNG fuel for standard vehicles. It is a signal that the Caribbean’s most visible environmental liability is becoming an industrial feedstock category.

What Are Seaweed Biostimulants and Why Does Sargassum Make a Good Source?

Biostimulants are natural substances that improve how plants grow, absorb nutrients, and cope with environmental stress. Unlike synthetic fertilisers, which feed a plant directly with nitrogen, phosphorus and potassium, biostimulants work by activating the plant’s own biological processes: stimulating root development, improving nutrient uptake efficiency, and building resilience to drought, heat and salinity.

The category has grown rapidly as the environmental costs of synthetic fertiliser dependency have become harder to ignore. Petrochemical-based fertilisers contribute significantly to agricultural runoff into waterways, including the very nutrient loading in the Caribbean that feeds sargassum growth. Regulatory pressure in the EU and US is tightening, organic certification requirements are expanding, and a new generation of premium agricultural and horticultural buyers are actively seeking certified alternatives.

Sargassum turns out to be an unusually rich source of the compounds that make effective biostimulants. The seaweed contains sulphated polysaccharides, betaines, polyamines, amino acids, and auxin-like plant growth regulators. These are the same classes of molecules found in the commercially farmed seaweeds already used to produce biostimulants in Europe and North America. The difference is that in the Caribbean, the raw material arrives in quantities that dwarf any managed harvest operation. Removing it has direct environmental value independent of what is made from it.

How SOS Carbon Harvests Sargassum at Sea Before It Reaches the Beach

The core logistics problem with sargassum is timing. Once it reaches shore and begins decomposing, toxic gas emissions accelerate, the biomass degrades rapidly, and the cost and complexity of collection rises sharply. SOS Carbon, the sister company founded by MIT spinout co-founder Andrés Bisonó León, tackles this at source.

The company’s patented Littoral Collection Module converts existing artisanal fishing boats into high-capacity seaweed harvesters, each capable of collecting up to ten tonnes per hour. The system is designed to be mounted on locally available vessels using the skills of local fishermen, with no specialist equipment imported and no outside labour required. SOS Carbon licenses the technology to operators in Antigua and Barbuda, Puerto Rico and Mexico, collecting rental fees while expanding its harvesting network without bearing the full capital cost of each new vessel.

Martínez arrived in the Dominican Republic after years researching marine and aquatic waste valorisation in Galicia, working on how seaweed compounds yield antibiotic molecules and how fish processing byproducts can be refined into cosmeceutical ingredients. When Bisonó León contacted her looking for deep biotechnology expertise to build out a processing operation alongside his harvesting business, the fit was immediate.

Once harvested, the seaweed is dried and transported to SOS Biotech’s biorefinery in Santo Domingo, where it enters a fully circular processing stream the company says produces no residual waste. The biorefinery currently has annual capacity for 36,000 litres of bio-based product, with a stated path to 100,000 litres through existing infrastructure and a longer-term modular model the company believes could reach 9 million litres per year.

Replacing Petrochemical Fertilisers: What Sargassum Biostimulants Mean for Caribbean Agriculture

The biostimulants SOS Biotech produces are already in commercial use. Marine Symbiotic, which enhances crop metabolism, resilience and overall plant performance, is being sold to agricultural operations and smaller-scale consumers across five locations in the Dominican Republic. USDA organic accreditation has opened the US market, where the company is already supplying five farmers. Marine Soil is a bioactive substrate for hydroponic growing systems. Marine Blossom targets the cut flower industry.

The agricultural import dependency of Caribbean nations gives this particular product category unusual strategic relevance. The region imports the bulk of its agricultural inputs, including synthetic fertilisers derived from petrochemical feedstocks. A regionally produced, organically certified biostimulant derived from a feedstock that is simultaneously an environmental liability represents a genuine import substitution opportunity. This is also what FUNDEMAR’s coral seeding programme in the Dominican Republic demonstrates in its sector: the Caribbean’s environmental problems are increasingly also its most credible commercial opportunities.

The employment dimension is also material. The programme has created formal jobs for more than 130 fishermen across the Caribbean, with Martínez reporting that many now earn two to three times what they made from traditional fishing. This is the kind of blue economy intervention that development finance institutions have been seeking to scale: environmental remediation that also creates durable coastal employment, without requiring the beneficiaries to leave their existing skills and infrastructure behind.

Beyond Agriculture: Cosmeceuticals, Biopolymers and SOS Biotech’s Expansion Into Europe

Agriculture is the current commercial core, but Martínez’s stated ambition runs considerably further. SOS Biotech has already developed Atabey’s Nectar, a cosmeceutical extract that has passed dermatological testing and is ready for market. Sargassum’s polyphenol and polysaccharide content supports multiple cosmetic applications, and the company has recently developed an emulsifier made entirely from seaweed, a formulation breakthrough with implications for the wider natural cosmetics supply chain.

Chlorovita, a nutraceutical, is in development. Escumaqua, a biosurfactant foaming agent, is in the pipeline. Alginaqua, a sargassum-derived biopolymer, is being evaluated by biomaterial companies. Cardboard prototypes from sargassum biomass are under development as a packaging solution. The company is also selling treated sargassum as a raw material to third-party processors, a deliberate open-model strategy. “We are not going to solve the sargassum problem alone,” Martínez has said. “Many people can benefit from this problem and we want to enable a whole new industry.”

The geographic expansion roadmap extends beyond the Dominican Republic. Barbados, Grenada and the US Virgin Islands are next in the Caribbean. Spain and Portugal represent the European opportunity, where Rugulopteryx okamurae, a different invasive seaweed species, is causing accelerating damage to Atlantic coastlines and creating a parallel market for the company’s harvesting and processing model.

SOS Biotech is currently raising $4 million, targeting production scale, product diversification and export market development in the US and EU. Martínez has been explicit about what kind of investment she is seeking: “We don’t just want money. We want investors who will work with us, open doors and understand that this is a Global South solution with global potential.” The company was a finalist in the 2025 Ocean Exchange award competition, which accelerates the adoption of innovative solutions for a sustainable blue economy.

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This article is part of the Caribbean Science and Innovation Report. For related coverage see how a UWI spin-off in Barbados is running cars on sargassum, how the Caribbean is turning its ocean into a research and investment frontier, and how FUNDEMAR is pioneering coral seeding in the Dominican Republic.