It's all in the details, not really as simple as the napkin math. The CO2 capture step obviously doesn't use ALL the energy released from burning the fuel. You'

It's all in the details, not really as simple as the napkin math. The CO2 capture step obviously doesn't use ALL the energy released from burning the fuel. You're not converting the CO2 back into fuel, just capturing it and sequestering it somehow. It's a question of capital and operating expense (and risks) of the process overall.