The Untapped Potential of Seaweed Farming White Paper

Seaweed farming presents a multitude of potential benefits, from carbon offsetting and coastal protection to use in aquaculture and as an environmentally friendly textile material. Globally, seaweed farming intensity is rapidly accelerating, with the Food and Agriculture Organisation (FAO) estimating an increase of approximately 230% during the 20-year period from 2000 to 2020 [1]. We are still, however, far from realising the full potential of seaweed, especially in Europe, in which only 0.8% of worldwide production is concentrated. European countries are facing complex and simultaneous challenges such as climate change, sea-level rise, economic instability and unsustainable fishing practices. Against this backdrop, seaweed farming holds great promise, offering a sustainable, multifaceted approach to tackle these issues head-on. Leveraging the benefits of seaweed farming would help to stimulate local economies, improve the sustainability of aquaculture, and contribute to climate change mitigation.

1.  Blue Carbon

Blue Carbon refers to the carbon stored in marine and coastal ecosystems. Seaweed farms, as a part of these ecosystems, can play a significant role in carbon sequestration. Through their rapid growth and photosynthetic activity, seaweeds absorb substantial amounts of carbon dioxide from the ocean and “lock” it into a solid form which can then be harvested or allowed to sediment to the seabed. Scientists have found that seaweeds can be as much as 20 times more effective than plants at this process [2], and several countries including China, Indonesia and the Philippines have already made seaweed based carbon sequestration an integral part of their strategies for climate change mitigation.

Although seaweed farming has a much larger footprint in Asia than Europe, some local schemes are being developed to unlock the climate potential of this untapped resource in the European context. For example, in the UK, public-private schemes such as Seaweed in East Anglia, a joint project between the University of East Anglia (UEA) and the Centre for Environment, Fisheries and Aquaculture Science (Cefas), seeks to stimulate local development of seaweed farms for food, fuel, animal feed and fertiliser [3]. Between 2016 and 2023, seaweed businesses in the UK more than doubled, and this is expected to increase as the public develops a greater appreciation of the benefits. 

For seaweed farming to make an appreciable difference to the carbon emissions of European economies, a massive scale-up from small pilot projects to kilometre-scale farms is required. This will require an investment in people to build the skills and knowledge required, increased funding for seaweed businesses and the informed consent of coastal communities. Ongoing research into the ecosystem benefits and possible negative consequences of largescale seaweed farms also needs to accelerate if we are to ensure that large farms do not inadvertently harm local marine fauna and flora [4].

1. Water Quality and Coastal Protection

Increasing populations and coastal development are leading to elevated aquatic nutrient levels from sewage, fertiliser and agricultural runoff [5]. This artificial nutrient enrichment can cause Harmful Algal Blooms (HABs), events that involve explosive growth of phytoplankton and lead to significant ecological disruptions, including oxygen depletion in the water, the death of marine life, and the release of toxins harmful to both marine and terrestrial organisms. In addition to their effects on the ecosystem, HABs can cause severe economic damage, particularly to fisheries and coastal tourism: 45% of insurance claims for fisheries are due to HAB-caused losses [6], and severe HABs require the closing of beaches to protect human health.