The Plan to Turn the Caribbean’s Glut of Sargassum Into Biofuel

IN the Caribbean, summer is supposed to be the season of sun, sand, and crystal clear waters—for decades, Mexican vacation destinations like Cancun, Cozumel, and Tulum have been synonymous with paradise. But then the sargassum began to arrive. For the past 15 years, large quantities of this brownish-colored seaweed have been invading beaches around the Gulf of Mexico every summer, its arrival from the open seas coinciding with high tourism seasons.

Forecasts from the Optical Oceanography Laboratory at the University of South Florida indicate this summer could be the worst on record, with up to 400,000 tons of sargassum predicted to wash up on Mexican coasts. As well as covering up the sand and spoiling the appearance of the country’s pristine beaches, the seaweed releases gases as it decomposes—toxic hydrogen sulfide, as well as the greenhouse gases methane and carbon dioxide.

A study by the Inter-American Development Bank estimates that sargassum drives down local GDP by 11.6 percent in Quintana Roo, the coastal state home to the tourist hot spots of Cancun and Playa del Carmen. The Mexican hotel sector says that it costs them more than $100 million a year to clear sargassum from beaches.

Exactly what’s causing so much seaweed to flood the Caribbean remains a debated topic. Experts have pointed to warmer ocean waters, ever increasing amounts of agricultural fertilizer flowing into the ocean, and changes to ocean currents as potential culprits. But the definitive cause of these algal blooms has yet to be pinned down.

For engineer Miguel Ángel Aké Madera, an expert in nonconventional energies, washed up sargassum needs to be processed in large quantities to stop it being a problem—and in his view, this can be achieved by using it to make biofuel.

“By processing 500 tons of sargassum, 20,000 cubic meters of biogas is obtained,” says Aké Madera, who is the founder and director of Nopalimex, a Mexican company pioneering generating gas and electricity from biomass and farming waste. A cubic meter of biogas can provide the same amount of energy as a liter of gasoline. “An average gas station in Mexico sells between 20,000 and 25,000 liters of fuel daily,” he says. “500 tons of sargassum daily could satisfy an equivalent demand.”

Esteban Amaro, director of the Quintana Roo Sargassum Monitoring Network, agrees that fuel is the best product to focus on. Processing the seaweed into other consumer products is possible, but inadvisable given that the health risks of doing so have not yet been sufficiently studied.

“I believe that sargassum’s purpose is to produce energy, because when it decomposes, it releases many heavy metals such as arsenic, lead, and cadmium,” Amaro says. “Therefore it is better to produce biofuels or biogas than everyday products like clothing or shoes.”

A Potential Source of Carbon Credits

In the race to dispose of sargassum, there is another viable product—Sargapanel, a construction material developed by researchers at the National Autonomous University of Mexico (UNAM). These panels use between 60 and 70 kilos of wet sargassum per piece and offer several advantages compared to conventional paneling: The material is around 33 percent more flexible, has greater resistance to impact, and is a fire retardant. In addition, no chemical additives are used in its production, so it can be recycled: Once its life cycle is over, it can be shredded and reintegrated into the production line.

“With this project, not only do we contribute to reducing the problem … we also generate profits from carbon credits. For every 5 tons of wet sargassum, a carbon credit is generated, and each credit is worth between $10 and $30,” says Miriam Estévez González, head of the group that developed Sargapanel at UNAM’s Center for Applied Physics and Advanced Technology (CFATA) in Juriquilla, Querétaro.

Estévez estimates that if 4,000 tons of dry sargassum were processed into paneling each year, this would generate an annual profit of between $80,000 and $240,000 as well as absorbing the equivalent of 8,000 tons of CO₂. “Making a comparison, we would be removing from circulation about a thousand cars,” she says.

CFATA scientists, in collaboration with academics from other UNAM departments, have also developed several other products, among them Sargabox—cardboard packaging boxes that are also fire-resistant—as well as filters that can be used to remove contaminants from water, including microplastics.

“In the case of Sargapanel, we already have the necessary scientific studies and a registered and scalable utility model that is fully competitive, and we are approaching some companies that are leaders in construction materials,” says Estévez.

On February 28, the governor of the state of Quintana Roo, Mara Lezama Espinosa, announced the formation of the Sargasso Comprehensive Sanitation and Circular Economy Center, whose aim is to shift the macroalgae from being considered a pollution problem toward it being used as an economic and environmental resource. If processed into long-lasting physical products, sargassum can lock away the carbon it draws from the environment to grow; if turned into a biofuel, it can avoid some fossil fuel emissions.

The center will mainly promote using sargassum to produce biogas and organic fertilizers—replacements for products that usually result in greenhouse gases being released when made and used. The center will then sell carbon credits off the back of these emissions reductions.

“There are European countries that cultivate algae to generate energy, but it is different, because they sow it specifically in the sea so that it can develop there and then they can process it. In our case, it is an algae that is caused by natural issues, by the increase of the temperature of the seas, by the effect of climate change due to the irrational use we make of our waste that we dump into the sea,” says Aké Madera. “All this biomass develops in enormous quantities that end up in the Caribbean.”

The Dominican Republic, Jamaica, Guadeloupe, Martinique, and Dominica have developed successful pilot projects for using sargassum for biogas production, but none have done so on a large scale. “They are waiting to see what Mexico does,” says Aké Madera.

Although the center is still under development, two potential sites have been identified in Cancun for its installation. The government of Quintana Roo plans to combine its work with that of wastewater treatment plants, which will produce a blend of sewage and microbes known as “activated sludge” that can be used to make biogas when there aren’t massive quantities of sargassum available.

What if the Sargassum Disappears?

One of the main limitations of Mexico’s proposed sargassum industry is the question of whether such large quantities of the seaweed will always be available.

“There will be atypical years, like the last one, in which little sargassum arrived, due to changes in ocean currents, but it will continue to arrive, if not in Mexico, then in many parts of the Caribbean,” says Estévez. “We have to learn to be with it and give it a real and efficient use.”

For Aké Madera, sargassum, like many other types of biomass, can be used to generate heat energy, electricity, or vehicle biofuel, depending on the processor’s priority. He also doesn’t see a risk in pushing ahead with plans for a sargassum industry. “If at any moment sargassum stops arriving, we can replace it with nopal,” a type of cactus. Aké Madera is the owner of several biofuel patents, among them ones for processing nopal and sargassum, and another, a work in progress, that involves tequila vinasse, a byproduct of producing the popular spirit.

For now, sargassum appears to be here to stay. Scientific forecasts point to ocean temperatures increasing every year, which creates the ideal breeding ground for the macroalgae, though increasingly research is pointing towards ocean current changes also being a key driver behind seaweed overrunning the Caribbean, and predicting how these might shift in the future is difficult.

“The year with the most sargassum in the Mexican Caribbean area was 2018, with 22 million metric tons—that is, what was floating in the entire Atlantic Ocean, from Africa to the Gulf of Mexico and the Caribbean,” says Amaro. “However, records of the University of South Florida, published in May, already indicate 37.5 million tons [is present in the water this year], and in June we surely reached 50 million metric tons.”

Of this floating sargassum, approximately 1 percent reaches the beaches of Quintana Roo, but this is enough to disrupt tourism across wide range of destinations. Among the worst-affected beaches are those of Tulum, Playa del Carmen, Puerto Morelos, Bacalar, Cancun, Cozumel, Isla Mujeres, Mahahual, and Chetumal. Destinations in the north of the peninsula are also affected, but to a lesser extent.

For Amaro, sargassum is the biggest environmental issue facing Mexico, as it poses economic, social, environmental, and health problems. Despite this, he says, it’s also important to recognize that when it is in the sea, in smaller quantities, the seaweed forms an important part of the local marine ecosystem. “Many fish larvae, invertebrates, commercially important fish, and other species such as whales and sharks develop there, depending on the shade of the sargassum and its production of food in the early stages of their life cycles.”

In the future, some sargassum could be harvested from the sea before it hits Mexico’s beaches. On June 9, the Mexican Institute for Sustainable Fisheries and Aquaculture Research proposed classifying the algae as a fishery product and listing it in the country’s National Fisheries Charter, which would allow it to be harvested and marketed. As part of this proposal, the institute sent a research vessel out to sea to sample and analyze floating sargassum, the water it lives in, and the species it supports. Ultimately, the institute said in a statement, this knowledge could one day “enable its identification and capture on the high seas, before it reaches the beaches.”

This story originally appeared on WIRED en Español and has been translated from Spanish.