Rum and Sargassum: Turning Problems into Solutions

Written by: Lindsey Myhre

Edited by: Olabisi Olawole

Junior Division

Introduction

Amidst the heap of climate-related challenges Barbados faces, three have converged within one innovative initiative. On Caribbean beaches, heaps of rotting Sargassum seaweed cover beaches. This threatens the tourism industry, on which many islands like Barbados depend, as well as proves a nightmare for fishing - another major source of income. Inland, the Caribbean's infamous rum production generates hundreds of millions of liters of wastewater annually, a heavy stressor on the health of surrounding ecosystems. Such problems are layered onto the unremitting obligation to cut out fossil fuels, especially as Barbados pursues its Sustainable Development Goal of becoming fossil-fuel free by 2030. The Rum & Sargassum biofuel initiative, led by Dr. Lagena Henry and her research team at the University of the West Indies (UWI), has addressed these three problems with one solution: biofuel made from locally sourced waste. Its integrated design provides an exemplary system-based solution.

Rum & Sargassum to Biofuel: How does it work and what impact can this have?

In 2011, the free-floating seaweed that forms large mats at the ocean’s surface, Sargassum, shifted from pesky scattered blooms in the Sargasso Sea to inundations at unprecedented scales. Since this turning point, Sargassum has carpeted beaches in the West Indies, killing fish, blocking ships, and raising public health concerns associated with the release of hydrogen sulfide as it rots on the beach (Bennett et al., 2025). What is responsible for this shift is still debated, with the recent leading theory holding that the culprits are rivers like the Amazon, which input excessive nutrients into the oceans, in addition to atmospheric nutrient inputs such as Saharan dust. Whatever the cause, the management of Sargassum along its shores has become a costly, unpredictable, and urgent responsibility for each island. So much so that in 2018, the government of Barbados declared Sargassum seaweed a national emergency. But Sargassum just so happens to be rich in organic compounds needed for anaerobic digestion used in biogas production. Researchers such as Dr. Legena Henry recognized it as a fantastic alternative to sugar cane and declining production in Barbados as a source of biofuel (Henry et al., 2021). The commodification of Sargassum has the potential to do wonders for the management of the blooms. After all, pricing a natural resource surely encourages its depletion.

At the same time, wastewater from the rum industry is optimal for producing biomethane, making it the most practical option for large-scale anaerobic digestion in the water-scarce Caribbean. Rum distillery wastewater has high levels of organic compounds causing a high chemical oxygen demand (COD). When this enters surrounding aquatic systems, it can create anoxic conditions. Its decomposition can also produce toxic compounds such as hydrogen sulfide (EPA, 2009). This waste has been notoriously difficult to treat and dispose of. Together, these two problems have become a green energy solution. An SDSN report estimates that if it were to supply Barbados’ annual transportation demand, it would need 685 million liters of rum distillery waste and 105,759 tons of fresh Sargassum. For once, a means of sustaining the population’s rampant energy demands is in no short supply. If fully implemented, this could avoid up to 1 million metric tons of CO2 emissions each year (SDSN Caribbean, 2022).

The process relies on anaerobic digestion of Sargassum and rum distillery wastewater. The two are combined in a digester where microorganisms break down the organic matter in oxygen-free conditions, producing biogas - a mixture of methane and CO2. The biogas is processed to produce biomethane, which can be compressed and used directly in CNG vehicles or existing natural gas pipelines, requiring no new infrastructure (Henry et al., 2021). With an estimated 20 million tons of Sargassum in the region and 800 million liters of wastewater being treated per day, the UWI research team recognized a way to turn climate issues against one another. “It’s a homegrown climate solution,” Henry said when first showcasing the project in 2019 at the Global Solutions forum in New York. “Barbados has the ingredients to produce its own clean fuel from what we already have too much of”.

Is this realistic? What are the setbacks?

However, like all emerging solutions, biomethane has its setbacks. The most important consideration is the feasibility of CNG engines. Electric Vehicles would be in direct competition with biofuels since EVs are the current forerunner as the carbon-neutral solution for Barbados’ transport sector (Edgehill et al., 2014). Barbados’ goal of being fossil fuel-free by 2030 is undeniably focused on electric transport and energy production. But realistically, electric vehicles alone cannot cover every sector, especially with Barbados’ limited grid storage. Green energy solutions must consider the benefits of a diversified energy matrix. Biomethane offers an alternative to gasoline and diesel that is already compatible with existing natural gas pipelines. For those with a CNG engine, it is compatible with existing cars as well. The manufacturing of EVs is more costly than converting existing international combustion vehicles to CNG. Rum & Sargassum promotes an affordable, 4-hour engine conversion to CNG. The estimated cost is 1,500 BBD compared to approximately 5,000 BBD per EV (Henry et al., 2021). Additionally, for the grid to supply energy for EVs at the scale needed to meet the 2030 target, it would require significant fossil fuel imports until solar and wind energy could catch up. The bio-methane-powered CNG vehicles are envisioned as a complementary approach within Barbados’ goal of being fossil-fuel free, highlighting its use of existing infrastructure. As Dr. Henry put it at the project’s launch: “This is how we make any car in Barbados a renewable energy car.”

Other limitations arise around the issue of scaling up. The logistics of providing sufficient digester infrastructure for biomethane at a national level, and of collecting large volumes of sargassum are complex. Rum & Sargassum removes sargassum from deep-water areas of the Barbados EEZ at road-traffic scale before it beaches (Rum & Sargassum, n.d.). But can this be realistically done on the scale of hundreds of tons?

Conclusion: A Triple-Win Solution Combating Waste, Sargassum Blooms, and Fossil Fuels

Despite setbacks, what Rum and Sargassum offers is a triple-win systems-thinking solution. It transforms two waste streams into renewable fuel, cleaning the shores by valorizing Sargassum blooms, and reducing industrial pollution by using rum distillery wastewater. It cuts emissions and reduces reliance on imported foreign fossil fuels while strengthening local industry. As Rum and Sargassum takes off, whether or not biomethane becomes a dominant energy source in Barbados, the initiative deserves recognition for embodying the kind of circular-economy thinking the world so sorely needs.

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References

Bennett, M., March, A., Li, H., Lallemand, P., Maréchal, J.-P., & Failler, P. (2025, May). Qualitative and quantitative assessment of Sargassum valorisation solutions for the Caribbean. Journal of Environmental Management, 381, 124954. https://doi.org/10.1016/j.jenvman.2025.124954

Legena, H., McKenzie, B., Goodridge, A., Pivott, K., Austin, J., Lynch, K., Spencer, S., Cox, F., Holder, N., Murray, R., Prado, V. R., & Ravillard, P. (2021, May). Experimental evidence on the use of biomethane from rum distillery waste and Sargassum seaweed as an alternative fuel for transportation in Barbados. Inter-American Development Bank. https://doi.org/10.18235/0003288

Rum & Sargassum. (n.d.). Story. https://rumandsargassum.com/story/https://rumandsargassum.com/story/

SDSN Caribbean. (2022, June 13). Rum and Sargassum: The biofuel potential for Barbados and beyond. https://www.unsdsn.org/news/rum-and-sargassum-the-biofuel-potential-for-barbados-and-beyond/

U.S. Environmental Protection Agency. (2009). Wastewater technology fact sheet: Distillery wastewater treatment. https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P100U83P.TXT