When you burn fuel, the weight of the CO2 aproximately x3 the weight of the fuel [1]. The density of fuel and liquid CO2 is very similar, so the storage tank of the CO2 must be almost x3 the size of the fuel tank. Also, the hard part is not "capturing" the CO2 in a tank for a week, but capturing it for a few thousand (millions) of years because you must change it to a stable chemical form that can be buried.
[1] Fuel is essentially H-CH2-CH2...-H, simplifying many CH2. When burned, the H goes away as water and the C as CO2. So the weight changes from 14 to 44
When you burn fuel, the weight of the CO2 aproximately x3 the weight of the fuel [1]. The density of fuel and liquid CO2 is very similar, so the storage tank of the CO2 must be almost x3 the size of the fuel tank. Also, the hard part is not "capturing" the CO2 in a tank for a week, but capturing it for a few thousand (millions) of years because you must change it to a stable chemical form that can be buried.
[1] Fuel is essentially H-CH2-CH2...-H, simplifying many CH2. When burned, the H goes away as water and the C as CO2. So the weight changes from 14 to 44