The climate crisis debate is incomplete without a discussion on biodiversity and food security where adaptation signifies opportunities for more options like the seaweed. Seaweed farming has emerged as one of the most promising resources due to its remarkable adaptability, short development period, and resource sustainability. Expanding seaweed farms can potentially boost local incomes, food security, and environmental health.
According to Food and Agriculture Organization (FAO) data, the global seaweed output (both aquaculture and wild) has increased nearly threefold from 118,000 tons to 358,200 tons in the past two decades. This signals the commitment to biodiversity, environmental conservation, and economic advantages. According to the World Bank analysis, seaweed farming is particularly important for women, rural populations, and indigenous people.
Unlike terrestrial crops, seaweed doesn’t require fertilizer, pesticides, freshwater, or land, and it grows rapidly -some marine algae can be ready for harvest in as little as six weeks. Seaweeds use the entire water column. This means farmers can grow seaweed using a process known as vertical, or 3D, farming -and reap large harvests from a small area.
Two methods are mainly employed, the line method which is the use of loop or knotted monofilament line or polythene rope tied end to end of two mangrove stakes installed 12 meters apart from each other, into which plants are tied, and the Net method, which is the use of monofilament or polyethylene net measuring 2.5 meters wide by 5 meters long with a mesh of 60cm mesh stretch, suspended 4-8 feet below the surface.
Seaweed farming is the fastest-growing aquaculture sector, popular in Southeast Asia, Canada, the United States, Europe, Tanzania, and Kenya among other African countries. One of the most sustainable types of aquaculture, seaweed farming boosts the production of biomass that can be used for biofuel, bioplastic, livestock feed, and human consumption. The farms can help improve water quality buffer the effects of ocean acidification in surrounding areas, and create forage and refuge habitats for commercially important fish and diversity of marine life.
Eelgrass, mangroves, and salt marshes are known for their ability to store carbon. Seaweeds pull more greenhouse gas from the water than all three combined based on biomass. Seaweeds also gobble up nitrogen and phosphorus. In large quantities, these nutrients cause algal blooms that deplete the ocean of oxygen when they decompose. Excess nitrogen and phosphorus from stormwater runoff and point sources are behind the dead zones that form in the Gulf of Mexico and the Chesapeake Bay.
Additionally, seaweeds act as sponges soaking up what’s in the water. These marine plants could potentially be cultivated to reduce heavy metals and other coastal pollutants. However, seaweeds grown for this purpose would never be eaten. Communities and stakeholders could establish seaweed farms in polluted areas with the sole aim of improving the health of the coastal ecosystem.
Macroalgae aquaculture comprises more than 30 percent of total marine aquaculture production and is valued at 5 percent of the total value of aquaculture. Kenya Marine and Fisheries Research Institute, (KMFRI) helped set up Kibuyuni as the first seaweed model firm in Kenya, which has been in operation for almost a decade now. Other farms have been developed in Mkwiro, Wasini, and Funzi Islands, Gazi, and Mwazaro Beach.
In some cases, seaweed has turned invasive when grown outside its natural range, overgrowing coral reefs, and throwing off the balance of the local ecosystem. This is why it is important to encourage the development of new native species as seaweed farming expands worldwide. It is also important to take into consideration the entanglement of sea animals in seaweed farms. The Centre for Ocean Renewable Energy at the University of New Hampshire is currently testing carbon fibre composite grow lines which are meant to break rather than entangle sea animals.
Partners are investigating the siting requirements, designs, infrastructure, and best management practices. This work will lead to more efficient permitting and allow seaweed farming to expand while also being economically and environmentally sustainable. Seaweed farms occupied only 0.19 million hectares in 2018. Expanding sustainable seaweed farming to 13.39-25.14 million hectares by 2050 could sequester an additional 2.50-4.72 gigatons of carbon dioxide.
