Analysis of Electrochemical Capture of CO2 From Oceanwater Coupled With Hydrates-Based Seabed Sequestration

Novel energy efficient and scalable carbon capture and sequestration technologies are critical to meeting the goals of the Paris Agreement. In this study, we present a first-order system-level assessment of an integrated carbon capture and carbon sequestration plant that couples electrochemical CO2 capture from oceanwater with co-located long-term carbon sequestration as CO2 hydrates (ice-like solids) on the seabed. Separate recent experimental results associated with electrochemical capture and hydrate formation form the basis for this energetics-focused analysis, which evaluates power consumption of all the key components associated with capture and sequestration. Hydrates can be formed from both pure water as well as seawater, and the implications of including a desalination plant to provide pure water for hydrate formation are studied. All analysis is conducted for a 1 plant which captures and sequesters 1 megaton CO2 annually. Our results indicate the carbon capture will consume significantly more energy than carbon sequestration despite the use of a low-energy consuming electrochemical technique. From a sequestration standpoint, there are clear benefits to forming hydrates at high pressures, since the elevated formation rates reduce the number of hydrate formation reactors significantly. It is also seen that the addition of a desalination plant to provide pure water for hydrate formation (which speeds up hydrate formation) will not affect the energetics of the overall process significantly; however the CAPEX and operational aspects of including a desalination plant need to be analyzed in greater detail. Overall, this study seeds a novel CCS concept which can be deployed via decommissioned oil-gas platforms to capture CO2 from surface oceanwater and store CO2 right below on the seabed after appropriate sealing (artificial or natural).