Definition :
The deep ocean CO2 injection consists in injecting CO2 into the deep ocean below 3000 m. More than 75% of the oceans have a depth below 3000m allowing large amount of storage. At 3000 m depth, the water column leads to a pressure around 300 bars. At this pressure, the CO2 is liquefied and denser than water, thus sequestrated in the depths of the oceans. It is mentioned that 20% of the injected CO2 might be released over a period of 200 years. Moreover, the CO2 injected in deep oceans might impact life and biodiversity which is a strong societal concern.^1
The overall cost varies between 2.2$ / tCO2 for direct injection and up to 15.7$ / tCO2 for boat dispersal.^3
^1: IPCC, https://www.ipcc.ch/site/assets/uploads/2018/03/srccs_chapter6-1.pdf ^2: Ocean Storage of CO2, The Liquid Grid, http://theliquidgrid.com/2018/07/22/ocean-storage-of-co2 ^3: Ocean Storage of CO2, The Liquid Grid, https://www.ipcc.ch/site/assets/uploads/2018/03/srccs_chapter6-1.pdf