Can seaweed save the climate?

WEEDS OF CHANGE: The idea that seaweed can help reduce carbon emissions should not be rejected altogether, but it comes with several shortcomings. This is the conclusion from a study recently published in Reviews in Fisheries Science & Aquaculture.

Centre researchers Max Troell and Patrik Henriksson, together with colleagues from Sweden, Chile and Canada have looked closer at the argument that seaweed can act as “ocean forests” and thus help sequestrating carbon.

They warn that seaweed farming should not be seen as a quick fix for the climate. Doing so may lead to several misdirected investments and shift focus away from further research on needed societal transformation, viable carbon sequestration methods and more substantial benefits related to for instance food production.

Food benefits

A major shortcoming relates to the idea that carbon in seaweed biomass could constitute a carbon sink simultaneously while simultaneously be consumed as food by humans or feed by animals. Consumed seaweed biomass will instead enter the fast carbon cycle and be released back to the atmosphere rather quickly.

Suggestions for sinking of seaweed biomass to the deep sea comes with several uncertainties related to feasibility, economics, ecosystem impacts and ethics, according to the authors. Instead, seaweed can potentially help reduce emissions in other ways, for instance by replacing food that have larger environmental footprints.

Seaweeds are an attractive source of nutritious biomass because they can be grown without additional freshwater, land, and fertilizers, but consumer acceptance, bioavailability and high iodine content make their potential role in global diets uncertain.

“Both wild and farmed seaweeds could potentially play a larger role in our diets as they can provide important nutrients with limited environmental burdens” says Patrik Henriksson.

More research needed

Other decarbonization efforts such as seaweed bioenergy production or reducing methane emissions from ruminants by including certain seaweeds in their feed have potential, but more research is needed.

“There is still a need to understand to which extent diverse seaweed farming systems capture and sequester carbon, which emissions that arise from different farming and processing activities” Troell and his co-authors conclude.

Read Farming the Ocean – Seaweeds as a Quick Fix for the Climate?