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From sea to soil: seaweed biochar for carbon dioxide removal

Explore the most likely future for the global seafood system within the Blue Economy

To limit global warming to 1.5°C, greenhouse gas (GHG) emissions must be reduced to net zero by 2050. Alongside substantial reductions in fossil fuel emissions, all pathways to net-zero emissions, as outlined by the Intergovernmental Panel on Climate Change (IPCC), involve the removal of carbon dioxide from the atmosphere. In parallel with the climate challenges, we are faced with a nature and biodiversity crisis endangering the ecosystems on which we rely. Hence, implementing solutions that can effectively address both challenges is critical. 


Pyrolysis is a technology that transforms biomass into biochar, fixing the carbon for long-term storage. Farmed seaweed represents a novel feedstock for biochar production and can thus contribute to increased carbon storage. 


To be eligible for carbon crediting, seaweed biochar must be accompanied by well-documented measures that effectively manage and prevent negative environmental and social impacts. For seaweed biochar to become a large-scale negative-emission technology, we must address several knowledge gaps throughout its value chain: 

  • To prevent negative impacts on wild seaweed populations, we need more knowledge about the risk of spreading potential pathogens and genetic material from seaweed farms, as well as strategies for mitigating such risks. 
  • Seaweed biochar, with its higher concentrations of sodium (Na) compared to woody biochar, requires a deeper understanding of optimal application strategies in soil to maximize its beneficial traits while reducing challenges associated with Na concentration.
If these challenges are overcome, and the CO2 uptake and emissions throughout the value chain are documented to be net negative, seaweed biochar could fulfil its potential as a nature-based negative-emission technology benefiting both sea and soil.