Techno-Economic Modeling of CO2 Hydrate Slurry Formation for Carbon Sequestration

Significant carbon sequestration capacity (up to 10 Gigatons/yr) will be needed by 2050 to limit the Earth’s temperature rise to < 1.5 °C. The current worldwide capacity is ∼40MT/yr, which highlights the need for the development of new and scalable sequestration approaches. One novel technology for long-term sequestration of CO2 is the deposition of CO2 hydrates (ice-like solids made with water and CO2) on the seabed (under marine sediments or with artificial sealing). This involves rapid formation of CO2 hydrate slurries in a bubble column reactor (BCR) by bubbling CO2 gas at high flow rates in a BCR with the unreacted CO2 being recirculated; this approach is being pioneered by the present research group. This study utilizes recent experimental results on ultra-fast hydrate formation to conduct a techno-economic analysis of the hydrate slurry-making process. All analysis is conducted for a 1 Megaton/yr sequestration project, which is expected to run for 30 years. Our analysis shows that the total cost of hydrate slurry production is $16.2/ton. Such projects would require an initial investment of $74M, and the energy requirement will be 641 MWh/day. Contributions of each part of the process to the total cost are identified. Our results show that gas recirculation in a BCR contributes minimally (0.04%) to the overall energy requirement. Furthermore, the cost of BCR is only 0.3% of the total investment cost. This suggests that a low conversion of gas into hydrates in each pass of the BCR is not detrimental from a techno-economic standpoint. The findings of this study set the stage for more detailed analysis of hydrates-based sequestration, which is essential to add this technology to the existing bank of established carbon sequestration solutions.