The cost of carbon management using ocean nourishment

Purpose – A current estimate of the cost of reducing the concentration of carbon dioxide in the atmosphere by Ocean Nourishment is provided. A scenario of fertilisation of the ocean in regions of excess phosphorous, carried out using a ship to distribute ammonium hydroxide, is examined. Design/methodology/approach – Ocean fertilisation could be deployed to draw down the carbon dioxide already in the atmosphere and store it for millennia in the deep ocean. Findings – The costs of fertilising the ocean with macronutrient depends mostly on the cost of producing the nutrient and the cost of its delivery. Macronutrient fertilisation has been calculated, for a particular scenario, to cost US$20 per tonne of carbon dioxide emission avoided for 100 years. Research limitations/implications – There is a collateral benefit of increased fish stocks, which is not considered here. The ocean, plausibly, has the capacity to sequester more than one Gigatonne per year of carbon (∼3.7 Gt CO2/yr) via macronutrient fertilisation. Practical implications – This modest cost of reducing climate change justifies further research and development of ocean macronutrient fertilisation. Social implications – The modest cost allows climate change to be addressed without serious economic disruption. Originality/value – The study reported is a contribution to mitigation of climate change.