Marine permaculture cultivation, sinking and storage of deep blue seaweed biomass carbon in Australian EEZ waters

  • 44 pages

  • Published: 1 Sep 2023

  • Author(s): Climate Foundation team

  • ISBN: 978-1-76053-394-6

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Scaled offshore marine permaculture to grow seaweeds is widely recognised as an emerging sector with large potential to meet a range of environmental objectives.

Many species of seaweed (macroalgae) have multiple economic uses and the scale-up potential of marine permaculture systems is evident. The carbon sequestration potential of seaweed has been demonstrated, with the blue carbon potential in offshore seaweed mariculture through deep ocean sequestration as high as 30 t CO2e per hectare per year. These sequestration rates are important as options for businesses and governments to meet their national and international obligations to reduce greenhouse gas emissions. AgriFutures Australia co-invested with the Climate Foundation to gather new data on marine permaculture systems and their potential as a sequestration technology.

This project investigated construction of a marine permaculture platform, seaweed growing, carbon sequestration rate measurement and optimal conditions for carbon sinking. The results from the research demonstrate that a cost-effective, reliable approach to measuring the export of seaweed biomass falling off seaweed platforms during growth and sinking through the water column for long-term sequestration could be achieved.

Further, the project provides reliable data on potential sequestration rates over long periods of time (months). This measurement phase is critical to any future carbon sequestration method as well as a key design principle for growing seaweed using marine permaculture systems. The project also provides evidence that when seaweed biomass migrates to deep ocean conditions, the carbon can be sequestered for many years, even if immediately and entirely remineralised. This observation is important to ensure future blue carbon methods can monitor, report and verify deep ocean sequestration.