(513ah) Can Thermocatalytic Transformations of Captured CO2 Reduce CO2 Emissions?

Thermocatalytic transformations of captured CO₂ into CO, CH₃OH or CH₄ via the hydrogenation reactions are attractive because they are desired to mitigate the anthropogenic CO₂ emission and reduce the atmospheric CO₂ concentration. However, CO₂ hydrogenation technologies inevitably require a source of H₂ and significant energy input, both of which are predominately generated by CO₂-emitting fossil fuels, currently. It is unclear whether the overall process is CO₂ negative and which technology pathway has the most potential to achieve net CO₂ reduction with various energy sources. In this work, we summarize the energy and material balances of various proposed industrial-scale CO₂ hydrogenation processes. The performance of the CO₂-to-CO, CO₂-to-CH₃OH, and CO₂-to-CH₄ processes is evaluated in terms of overall energy consumption, net CO₂ emission, and the levelized cost of CO₂ conversion. Simulation results show that the overall energy consumption and net CO₂ emission of all the proposed CO₂ hydrogenation processes are relying heavily on the sources of energy and hydrogen. Thermocatalytic transformations of captured CO₂ are at present economically unattractive and emit more CO₂ than they convert as the required energy and hydrogen mainly come from fossil fuels. However, the CO₂-to-CO process with energy from natural gas shows the potential to achieve a net reduction in CO₂, as long as the process energy consumption of life cycle assessment (LCA) is decreased to less than 13.0 MJ∙kgCO₂^-1 (currently 17.3 MJ∙kgCO₂^-1). All the CO₂ hydrogenation processes would achieve negative emissions with the availability of carbon-free energy, resulting in a significant CO₂ reduction. Compared with the cost from CO₂ capture and synthesis, H₂ production based on renewable energy shares in the total cost up to 70%, which indicates that a lower cost of H₂ production and a potential CO₂ tax will lead to an economical appealing for the proposed processes.