Techno-economic modeling of carbon dioxide hydrate 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 degrees C. Current worldwide sequestration capacity is only similar to 40MT/yr, which highlights the need for the development of new and scalable sequestration approaches. One promising approach for long-term sequestration of carbon dioxide (CO2) is the deposition of CO2 hydrates (ice-like solids of water and CO2) on the seabed with artificial sealing (or under marine sediments). Technologically, this involves formation of CO2 hydrate foam, transport of the foam to the sequestration site, compaction into hydrate plugs, sealing and then disposal. Critical to the techno-economic success of this concept is the ability to rapidly form hydrates. The present group has achieved very high rates of formation of hydrate foam by bubbling CO2 gas at high flow rates in a bubble column reactor (BCR). This study utilizes recent experimental results on ultra-fast hydrate formation to conduct a detailed techno-economic analysis of the hydrate foam-making process. All analysis is conducted for a 1 Megaton/yr sequestration project with project life of 30 years. Our analysis shows that the energy requirements (assumed as electrical in this study) for hydrate formation equal 260 kWhr/ton and the total cost of hydrate foam production is $36/ton. The biggest cost component is energy, which accounts for 51 % of total cost. A 1 Megaton/yr project will require an initial capital investment of $150 M. Such a project will consume 0.66 million cubic meters of seawater/yr. Contributions of various key processes to the total cost are quantified. Process-wise, the biggest contributors to total cost are refrigeration and gas compression, which account for 41 % and 27 % of the total cost, respectively. Cost of the BCR is only 0.1 % of the total investment cost. Also, gas recirculation in the BCR contributes minimally (0.14 %) to the overall energy requirement. Finally, this study identifies pathways to reduce $/ton costs to increase the viability of this carbon sequestration approach. It is noted that hydrate transportation, compaction and sealing are not included in this analysis which focuses on the techno-economics of rapid hydrate formation only.