Since 2011, Grenada has faced annual seaweed onslaughts, after the currents that used to trap sargassum in the Sargasso Sea broke down and allowed the algae to escape. It spread from West Africa to the Yucatán Peninsula, and returned each summer in massive blooms fueled by unusually warm water and fertilizer pollution.

In the open sea, the algae mats provide food and shelter to young fish, turtles and crustaceans. The problem is when it washes ashore, creating a smelly and unattractive mess that is costing millions of dollars a year to clean up.

But there are a range of ideas for turning sargassum into a benefit and not just a cost, at various stages of development.  

Grenada’s prime minister, Dickon Mitchell, held a conference last year to explore innovations. “We believe that we have a unique opportunity in Grenada and in the Caribbean basin to turn the tide on what is viewed as a problem into a solution – and into a solution that can have ripple effects to all of the stakeholders that it has thus far negatively impacted.”

Grenada’s government is working with the European Union and looking for companies that could partner them in creating a multibillion-dollar market for the Caribbean by rebranding the seaweed as a solution to the climate crisis. Last month, the prime minister launched an expression of interest process for companies to propose projects to make his goal a reality.

“We shouldn’t just see sargassum as a menace, but as an opportunity,” says Jerry Enoe, Grenada’s special envoy for oceans. So far, 33 companies have pitched ideas to the Grenadian government, which will pick a few to fund this summer, Enoe said.

One application lies in sustainable construction materials, particularly eco-friendly cement and building components. In Mexico, Sargablock has pioneered methods to create sargassum-based bricks and other construction materials. Their process can produce 1,000 blocks per day, which are ready for use after just four hours in the sun. Another initiative, Sargacreto, also based in Mexico, is developing similar materials.  

Sargassum is also gaining recognition in agriculture as a natural biostimulant whose extracts can enhance plant growth, improve soil health, and increase crop yields without synthetic chemicals – especially valuable for organic and regenerative farming practices. Sarga Agriscience is processing the seaweed into liquid fertilizer that contributes increased yields of maize, tomatoes, and grapes.

A UK-based aquaculture business, Seafields, which has created a water-based farm to catch the sargassum before it reaches land, says its solution could save Caribbean governments and hotels hundreds of thousands of dollars in sargassum removal and support a market in bioplastic and similar materials.

Sargassum is much cheaper to farm than most other seaweed, John Auckland, founder and chief executive of Seafields, told the Guardian. Used as a fertiliser, he says: “It stimulates crop growth by about 10% to 14% and can significantly increase yields for farmers.” He says it is a potential $200bn [£150bn] export market.

“We have successfully tested our pilot farm, where we deployed our innovative barrier technology to contain live Sargassum effectively, ensuring a year-round fresh supply for our partners,” he says. Seafields wants to scale up its farms across the Caribbean region, establishing key partnerships with hotels and coastal communities. 

Sargassum also could make electricity much less expensive. “They use diesel to generate electricity [now], which is very expensive for the local population. We are providing a reliable, cost-effective and sustainable alternative,” says Benjamin Nestorovic, CEO of SarGas.

SarGas installed a biodigester, which uses microorganisms to break down the seaweed into biogas and fertilizer, to fuel the ovens at the True Blue Bay Resort’s House of Chocolate bakery in St George’s. “You can eat chocolate with a good conscience,” Nestorovic says. “Our process produces clean energy and digestate – a valuable organic fertilizer – giving us two products in one.”

The company now has government approval to construct a large-scale biogas facility that would supply a biogas-fueled generator to make electricity for the Grenadian power grid. BIogas pairs well with solar panels, which Grenada is beginning to install, because the sargassum-based fuel can generate electricity overnight. “We complement each other,” he told the Washington Post.

The first planned SarGas generator would use 5,000 to 8,000 tons of sargassum per year, mixed with food waste and pig manure to create a balanced diet for the bacteria. It could generate 160 kilowatts of power, which is about half a percent of Grenada’s peak demand

By saving diesel and preventing methane emissions at the landfill, Nestorovic says it would avoid the equivalent of about 2,000 cars’ worth of greenhouse emissions.

Cover image: Punta Tuna Lighthouse from Punta Tuna Beach showing lots of sargassum. BrickLightning, Wikimedia Commons.

Sources:

How the Caribbean could turn a plague of seaweed into fuel and fertilizer. Washington Post, Apr. 9 2025

Sargassum creating economic crisis in the Caribbean. CTV,  Jul. 5 2024

TRUE BLUE BAY RESORT’S GREEN INITIATIVES.

From foul to fuel: how a seaweed problem could power the Caribbean. The Guardian, Mar. 25, 2025

Sargassum – Transforming a Coastal Menace into an Industrial Wonder. 1 Nov, 2024. Bella Heath, Seafields