Indirect ocean capture of atmospheric CO2: Part II. Understanding the cost of negative emissions

Negative emissions technologies (NETs), which result in the removal of CO2 from the atmosphere, will be necessary to limit global warming to 2 °C. Unlike point-source CO2 capture, NETs are agnostic to the emission source, and reduce the existing atmospheric CO2 concentration. This enables NETs to address distributed emissions from transportation and past emissions that have led to existing atmospheric CO2 concentrations. Despite their critical necessity, there are relatively few NETs that have been developed, and existing technologies do not have sufficiently detailed techno-economic analyses to allow comparison for the purpose of strategic investment and policy decisions. An analysis was performed of the economic feasibility of a novel platform of candidate NETs – indirect ocean capture (IOC) – through industry-validated economic and chemical process modeling supported by inputs from a prototype system. This manuscript details the development of a high-fidelity estimate of the cost of avoided CO2 emissions from this NET by coupling scaled experiments to economic analyses. For the lowest-cost scenario of co-location with a desalination plant, a likely cost of $604 per metric ton of avoided CO2 (tCO2) was found, and a best-case cost of $373/tCO2. Through improvements to unit processes, creative process optimization, and reduced carbon-neutral electricity prices, the cost of IOC negative emissions may be reduced in the future. Although NETs won’t likely require deployment for several years in order to limit warming to 2 °C, an objective techno-economic assessment of the options on the table will ensure that the best technology is developed and ready when deployment is required.