From Coastline to Compost: Turning Seaweed into a Climate-Smart Resource in Mauritius

Along the endless coastline of Mauritius, seaweed is a common sight. Washed ashore in large quantities throughout the year, these countless species of plants and algae that grow in the ocean, play an important role in coastal ecosystems by providing habitat for marine organisms and helping to mitigate the effects of erosion.

However, when excessive amounts accumulate on beaches, it becomes a challenge, affecting water quality, coastal ecosystems, and the recreational and tourism value of beaches. With around 435 species recorded in Mauritian waters and climate change expected to increase seaweed accumulation, the key question is no longer how to dispose of this biomass but how to use it more effectively.

Seaweed composting offers a practical solution by transforming coastal waste into a valuable agricultural input. Naturally rich in macronutrients, micronutrients, amino acids, vitamins, and plant growth hormones, seaweed contains many elements required for plant development. Instead of being sent to landfills, collected seaweed can be processed into nutrient-rich compost that improves soil health and supports sustainable agriculture. On this score, seaweed composting adheres perfectly to circular economy principles by converting waste into a productive resource that benefits both the environment and farming systems.

In Mauritius, this innovation is being led by the Food and Agricultural Research and Extension Institute (FAREI) under the Ministry of Agro-Industry, Food Security, Blue Economy and Fisheries. The Belle Mare Research Station hosts a dedicated seaweed composting unit designed for research, demonstration and training. Covering around 120 square metres and built at a cost of approximately Rs 1.6 million, the facility can produce between two and four tonnes of compost per cycle. It also functions as a practical learning site where compost production techniques are tested and shared with farmers and entrepreneurs.

The composting process begins with the collection of freshly stranded seaweed, ideally within 48 hours. Common species used include Ulva (such as Ulva lactuca and Ulva reticulata) and Sargassum, both suitable under local conditions. The seaweed is thoroughly washed to remove sand, salt, and marine debris. It is then mixed with carbon-rich materials such as bagasse, dry leaves, sawdust, or wood chips, along with poultry manure, which provides nitrogen and supports microbial activity. The recommended ratio is seven parts seaweed, three parts carbon material and two parts poultry manure.

Using the hot composting method, the mixture is arranged in piles where microorganisms break down the organic matter. The compost is regularly turned to maintain oxygen flow and moisture levels are carefully controlled. Over a period of 14 to 16 weeks, the mixture gradually transforms into a stable, dark, earthy-smelling compost ready for maturation and agricultural use.

The benefits of seaweed compost extend beyond waste management. It improves soil structure, increases water retention, enhances microbial activity, and supplies essential nutrients to crops. Trials conducted by FAREI have yielded positive results in vegetable and fruit production. It is also suitable for seedling preparation, potting mixes, mulching, and landscaping. By reducing reliance on imported chemical fertilisers and using locally available biomass, this eco-friendly practice upholds Mauritius’ shift towards a more sustainable and climate-resilient agriculture.

Through Training of Trainers programmes and hands-on workshops at Belle Mare Research Station, around 200 farmers and women entrepreneurs have already been trained in seaweed composting techniques. These sessions combine scientific knowledge with practical skills, enabling participants to adopt and adapt the technology for their own use.

It is to be noted that seaweed collection in Mauritius is regulated. The Beach Authority is responsible for managing coastal waste collection and usually works with authorised operators. Individuals, cooperatives, or businesses enterprises cannot freely collect seaweed from beaches. Any collection activity requires authorisation from both the Ministry of Environment, Solid Waste Management and Climate Change and the Beach Authority. This regulatory framework has been set up to ensure that seaweed harvesting is carried out sustainably and does not harm or disrupt the coastal ecosystems.

On the whole, seaweed composting perfectly demonstrates how environmental challenges can be transformed into sustainable opportunities. By converting stranded seaweed into a useful agricultural resource, Mauritius is linking coastal management strategy with climate-smart farming practices.

Link for video: https://youtu.be/vYOhdARyOEM

10 July 2026

Email: gis@govmu.org

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Topics: Environment, Innovation