Along coastlines in the Caribbean, the United States, and northern Brazil, massive amounts of brown seaweed called sargassum have become a growing problem.
When it washes up on beaches, the algae rot and release unpleasant gases that can harm health, disrupt tourism, and damage local ecosystems.
Traditionally, the seaweed is simply collected and dumped in landfills, offering no real benefit.
But researchers in Brazil believe they have found a way to turn this environmental nuisance into something useful: lighter, greener construction materials.
A team led by João Adriano Rossignolo, professor of biosystems engineering at the University of São Paulo (USP), worked with collaborators at the Federal University of São Carlos (UFSCar) to test whether sargassum could be incorporated into ceramic clay, a material widely used in construction.
Lightweight ceramic clays are valued for reducing the weight of concrete, improving thermal comfort in slabs, and even serving in gardening products.
The researchers mixed the algae into clay samples at different levels—20% and 40%—while keeping a control sample with no seaweed.
These samples were then shaped and heated, or sintered, at temperatures between 800 °C and 1,000 °C using either conventional ovens or microwave ovens.
The sintering process hardens the clay, making it ready for use.
Once prepared, the samples underwent tests for properties such as water absorption, porosity, and compressive strength.
The team also performed a life cycle assessment, comparing the environmental impacts of conventional expanded clay with the sargassum-based versions, from raw material extraction through final disposal.
The results, published in the Journal of Materials in Civil Engineering, were promising. Adding seaweed reduced the density of the clay, making it lighter—particularly at the higher 40% concentration.
Importantly, only the versions sintered in microwave ovens met all the strength requirements across the temperature range, proving that the right processing method is key.
Environmentally, the sargassum-based clays outperformed conventional expanded clay, thanks to their ability to recycle waste biomass and reduce the use of natural resources.
The researchers concluded that microwave-sintered clay containing sargassum could be a practical alternative that not only lessens environmental harm caused by algae but also makes construction more energy-efficient.
The team went further, exploring other potential applications for the seaweed. They tested its use in making panels for furniture and construction, as well as fiber cement tiles.
By turning the algae into ash, they were able to replace limestone—a common raw material—entirely. According to Rossignolo, panels with up to 30% sargassum and cement tiles with 100% limestone replacement not only met industry standards but also showed improved durability and strength.
By reimagining sargassum as a valuable raw material rather than coastal waste, this research points to a future where seaweed could help make construction materials both lighter and greener, transforming a major environmental problem into part of the solution.
