Seaweed Farms: A Tasty Solution to Climate Change?

Seaweed farms are the latest trend in climate change solutions, with Europe investing millions into them in the hope that they will absorb and store carbon.

Author: Amelia Elamradi
Artist: Sylvia Tsai
Editor: Daniel Jacobson

Within a decade, a boat trip in European waters might just involve a view of expansive rows of seaweed attached to ropes under the ocean’s surface. This is because of the European Commission’s new goal to create large-scale seaweed farms, specifically to farm 8 million metric tons of seaweed annually by 2030. Funding for seaweed farm projects has increased in the past couple years, including the €1 million provided by the EU for the AlgaeDemo project planned to cover up to two hectares of the North Sea. 

Why the need for seaweed?

Part of the current seaweed demand is that seaweed is extremely versatile, as it can be used in food such as sushi, medicinal products, natural fertilisers, packaging, biofuel production and carbon sequestration. 

However, the benefit most talked about is seaweed’s ability to capture carbon from the air during photosynthesis and store it within its biomass, lowering the carbon dioxide levels in our atmosphere. Less carbon dioxide means we can reduce the amount of heat trapped in our air by this greenhouse gas, and prevent further global warming. 

The benefits do not stop there: the carbon captured can remain fixed into the seaweed. When this aquatic plant dies, it drifts to the ocean floor and is buried as deep sea sediments. Deep in the ocean, little oxygen means that the seaweed with stored carbon takes centuries, or potentially millions of years, to decay, therefore keeping that carbon in the ocean, and not in our atmosphere. This is the plan for seaweed farms focused on carbon credit schemes, in which investors compensate for the carbon they release by investing in projects that sequester carbon.

For other seaweed farms, even though carbon isn’t sequestered via the natural process of seaweed detritus sinking, and is instead harvested for production, the use of seaweed may prevent environmentally-damaging practices. If seaweed is harvested to be used as a biofuel, we can avoid relying on fossil fuels, which led to the release of 36.3 billion tonnes of carbon in 2021. If seaweed is used to create packaging, we can reduce plastic use. Traditional plastics take centuries to decay and eventually end up in our ecosystems as microplastics. Furthermore, if seaweed is used as a fertiliser, there will be less need for artificial fertilisers, which cause environmental damage when they run off into our waterways. Most notably, this run-off causes excess growth of algae, taking oxygen and sunlight from other animals and plants, in a process called eutrophication.

Is there a catch?

Whilst seaweed farms offer substantial benefits, there may be other factors to consider. For example, marine biologists have highlighted the possible risk of introducing diseases that may accompany large-scale seaweed farms, and the need to maintain genetic diversity. Seaweed farming methods must remain sustainable for the seaweed crop to be environmentally favourable.

Furthermore, seaweed farms may actually be a carbon source instead of a carbon sink. Researchers have proposed that the surrounding ocean waters will bring in plankton and other organic material, therefore creating an ecosystem with an abundance of food for various species. Eventually, if this reaches the scale of a whole ecosystem, there will be many creatures releasing carbon dioxide as they respire, perhaps even more carbon than the seaweed is able to absorb.

Are seaweed farms the answer to climate change?

Considering its many uses, seaweed may be very promising as an alternative to other very environmentally damaging practices and materials, such as plastic and artificial fertilisers. In terms of the effect on climate change, further research would be useful to ensure the many farm developments can continue with confidence in its benefits. However, if it turns out seaweed farms aren’t as beneficial as we thought, authorities would need to take a step back to reevaluate, and put a hold on the mountain of investments being piped into them. Nevertheless, the majority of public opinions and scientific studies praise seaweed farming and it’s reassuring to see authorities such as the European Commission beginning to take action to tackle climate change.

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