Brown algae, known as sargassum, are washing up in large amounts on beaches in Brazil, the Caribbean, and the United States. The piles of seaweed harm tourism, fishing, and biodiversity. When the algae decompose, they release gases that can also affect human health.

Brazilian researchers have now found a way to turn this problem into a resource: using sargassum to make lightweight ceramic clay aggregates for construction.

Seaweed as a Raw Material

Until now, sargassum collected from beaches was usually taken to landfills. A research team at the University of São Paulo (USP) decided to give the biomass a new purpose. They tested how algae could be added to ceramic clays, which are already used in construction to reduce the weight of concrete, improve thermal comfort in slabs, and even as gardening substrates.

The team prepared clay samples with 20% and 40% sargassum and compared them with conventional clay. After moulding, the samples were heated in both conventional and microwave ovens. The researchers then measured water absorption, porosity, strength, and environmental performance across the life cycle of each material.

A Lighter, More Sustainable Alternative

The results, published in the Journal of Materials in Civil Engineering, showed that the algae reduced the weight of the aggregates, especially at 40%. Samples fired in microwave ovens met all strength requirements, while those heated in conventional ovens performed less well.

Life cycle analysis showed another advantage. Sargassum-based aggregates scored better environmentally than traditional expanded clay. They reduced the need for natural resources and improved energy efficiency.

Beyond Ceramics: Panels and Tiles

The team also tested other uses for algae. They made particle panels for furniture and construction and produced fibre cement tiles. In some cases, sargassum ash fully replaced limestone, making the materials stronger and more durable, while still meeting industry standards.

Circular Opportunities for Designers

This research shows how marine biomass can shift from waste to resource. For architects, interior designers, and product developers, it opens the door to lighter, more sustainable building components and furniture solutions. At the same time, it helps address the environmental challenges of invasive algae.

Source: Agência FAPESP
Photo: João Adriano Rossignolo/FZEA-USP