Introduction to Geological Sequestration - Introduction to Carbon Capture and Sequestration - page 357

Figure 8.1.1 Density of CO 2 as a function of the depth below ground level
The balloons illustrate the change in the density of CO 2 as a function of subsurface
depth. Picture from CO 2 CRC [8.1]. Copyright by CO2CRC, reproduced with
permission.
In Figure 8.1.2 , the difference between sequestering all the fl ue gas
or just CO 2 is illustrated. This simple calculation illustrates why it is
important to capture the CO 2 ; not only does it reduce the total amount of
gas that needs to be sequestered but, unlike fl ue gas, nearly pure CO 2 is
supercritical at sequestration depths and therefore has a much higher
density compared to fl ue gas at the same conditions. This effect of depth
on the density of CO 2 is illustrated in Figure 8.1.1 ; indeed a signifi cant
gain in density can be obtained if we sequester CO 2 below 1.5 km
depths.