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As summarized in a 2022 National Academies report on Carbon Capture and Utilization (Figure ET-22), it takes less energy to store captured COâ‚‚ underground than recycle it back to fuel. Synthetic fuels can be made from COâ‚‚, but the amount of energy needed is at least three times greater than the amount of energy in the original fuel. Renewable energy must be used, or we simply create more COâ‚‚ emissions than we mitigate.

This is evident from the science of thermodynamics: COâ‚‚ and water are the end products of complete combustion. They have no fuel value. Reversing them to recreate fuel by using water electrolysis to generate the hydrogen needed to react with COâ‚‚ to re-form the original fuel, for example, requires more energy input than the original combustion energy released. This is due to inherent inefficiencies in heat and combustion processes.

Gabrielli et al. [2] estimate 10X less energy is required simply to store the captured COâ‚‚ underground after compressing it to a liquefied or supercritical state, compared with using the captured COâ‚‚ to make fuels or chemicals. We therefore consider making synthetic fuels only for the most difficult to decarbonize sectors and uses, such as aviation fuels, or where we need to be able to transport and store renewable energy using existing infrastructure via creation of a synthetic natural gas, or chemicals to move to market.
 
 
 
Figure ET-22:   Carbon Capture and Utilization 
 
References 
National Academies of Sciences, Engineering, and Medicine. 2022. Carbon Dioxide Utilization Markets and Infrastructure: Status and Opportunities: A First Report. Washington, DC: The National Academies Press. .  
 
 
Paolo Gabrielli, Matteo Gazzani, and Marco Mazzotti, The Role of Carbon Capture and Utilization, Carbon Capture and Storage, and Biomass to Enable a Net-Zero-CO 2 Emissions Chemical Industry Industrial & Engineering Chemistry Research 2020 59 (15), 7033-7045 DOI: 10.1021/acs.iecr.9b06579