Engineering challenges of ocean liming

The relationship between the level of atmospheric CO₂ (carbon dioxide) and the impacts of climate change is uncertain, but a safe concentration may be surpassed this century. Therefore, it is necessary to develop technologies that can accelerate CO₂ removal from the atmosphere. This paper explores the engineering challenges of a technology that manipulates the carbonate system in seawater by the addition of calcium oxide powder (CaO; lime), resulting in a net sequestration of atmospheric CO₂ into the ocean (ocean liming; OL). Every tonne of CO₂ sequestered requires between 1.4 and 1.7tof limestone to be crushed, calcined, and distributed. Approximately 1tof CO₂ would be created from this activity, of which 80% is a high purity gas (pCO₂98%) amenable to geological storage. It is estimated that the thermal and electrical energy requirements for OL would be 0.6-5.6and 0.1-1.2GJtCO₂^-1 captured respectively. A preliminary economic assessment suggests that OL could cost approximately US$72-159t^-1 of CO₂. The additional CO₂ burden of OL makes it a poor alternative to point source mitigation. However, it may provide a means to mitigate some diffuse emissions and reduce atmospheric concentrations.