Marine Carbon Dioxide Removal: A Potential Solution

• The ocean has absorbed 25% of anthropogenic carbon dioxide emissions and over 90% of the excess heat generated by greenhouse gases.

• The ocean’s capacity to absorb carbon comes at a cost: ocean acidification, disrupted biogeochemical cycles, pollution, and harm to marine ecosystems.

• The ocean’s natural carbon and heat absorption processes are slow and carry ecological consequences.

• Marine carbon dioxide removal (mCDR) is increasingly being considered to complement emissions reductions and address lingering carbon dioxide burdens.

• Marine carbon capture strategies fall into two categories: biotic approaches (taking advantage of living systems) and abiotic approaches (manipulating physical or chemical properties).

• Biotic solutions rely on the inherent potential of ecosystems to sequester carbon while supporting biodiversity conservation and coastal protection.

• Abiotic techniques offer greater scalability and permanence, such as biomass burial at sea and reducing the acidic nature of the seas through ocean alkalinity enhancement (OAE).

• Despite its promise, mCDR is fraught with uncertainties and potential side effects. Techniques like ocean iron fertilisation, macroalgae cultivation, and OAE raise concerns about their consequences for marine biodiversity.

• Overcoming public scepticism and measuring how much carbon is captured and stays buried remains a challenge due to the cost of monitoring the seas.

• The Indian Ocean holds untapped potential for deep carbon burial, potentially capturing 25-40% of the marine carbon dioxide.