Yuting Zhang, Samuel Krevor, Christopher Aiden-Lee Jackson 

Databases of industrial-scale carbon capture and storage (CCS) identify the size of projects by their capture capacity, but frequently do not specify the amount of CO2 captured or stored over operating periods. We review a variety of publicly available sources to estimate the amount of CO2 that has been captured and stored by operational CCS facilities since 1996. We organise these sources into three categories broadly corresponding to the associated degree of assurance: 1) legal assurance, 2) quality assurance through auditing, 3) no assurance. Data were found for 20 facilities, with an aggregate capture rate capacity of 36 MtCO2 yr-1. Combining data from all three categories, we estimate that 29 MtCO2 was geologically stored in 2019 and there was cumulative storage of 197 Mt over the period 1996-2020. The widely used capture capacity for these projects is in aggregate 19-30% higher than the estimated storage rates suggesting that capture capacity is not a good proxy for storage rates. The difference between capture capacity and storage rates is project-specific and not always a reflection of project performance. This work provides a snapshot of storage amounts and highlights the need for uniform project reporting on capture and storage rates with quality assurance.