Emerging concepts in carbon dioxide storage

Finding means of storing and transporting captured carbon dioxide (CO2) has become increasingly important. Not all capture technologies (sources) can be co-located with sequestration options (sinks), and the development of an expansive CO2 pipeline network to connect sources and sinks requires significant time and capital. Additionally, temporary storage of CO2 in a solid or liquid state could prove useful for allowing today’s capture technologies to come online before permanent and ideally lucrative CO2 sequestration options open up. There are several methods for reversible solid-state and chemical CO2 storage, but their advantages and limitations have yet to be reviewed. This article focuses on the physical and chemical aspects of CO2 storage via liquid and solid chemical carriers and sorbents, and gives an overview of the energetics around their use, as well as prospects for their future development. Exciting opportunities for co-transporting hydrogen with CO2, for energy efficient long-distance transportation, and for coupling capture and multi-year storage could open up new options for carbon supply chains. Key findings of the analysis are the remarkable storage capacity of oxalic acid and formic acid (CO2-density of 1857 kg/m3 and 1152 kg/m3, compared with condensed liquid CO2 at 993–1096 kg/m3, respectively), the relative scalability and compatibility of carbonate salts for stationary storage with direct air capture, and the potential promise of multiple carriers for CO2 transportation. Solid sorbents do not achieve such ultra-high storage capacities, but could improve storage over compressed gas tanks on a capacity and energetics basis.