12. Technoenergetic and Economic Analysis of CO₂ Conversion

Mere improvements in energy efficiency and development of alternative energy sources may not be sufficient and timely to reverse the continuing rise of the CO₂ emissions before it crosses dangerous levels. Given the mixed feelings on the geological sequestration of captured CO₂ and the scale of worldwide CO₂ emissions, the idea of utilizing CO₂ to produce fuels and chemicals is receiving increasing attention as a potential long-term solution to this problem. The source of hydrogen is vital for producing fuels and chemicals from CO₂. We consider both renewable (i.e., solar) and nonrenewable (i.e., fossil fuels) sources of hydrogen and identify several fuels and chemicals that can be produced from CO₂ while meeting the hard constraint of net zero CO₂ emission. Taking a small, geologically disadvantaged, and developed city-state of Singapore as an example, we analyze and compare thermodynamically feasible production of fuels/chemicals, whose global demands can make a significant dent in CO₂ emissions. We also identify the hydrogen source and the cost at which it will make economic sense under various carbon tax regimes.