Energy efficiency analysis of CO2 mineral sequestration in magnesium silicate rock using electrochemical steps

A thermodynamic efficiency analysis using the exergy concept is used to assess CO2 mineral sequestration process routes where electrochemical steps (electrolysis and fuel cells) are used to produce aqueous hydrochloric acid and sodium hydroxide reactant solutions. Results from three recent publications on the subject that come to different conclusions are used for this case study. It is shown that including electrolysis as one of the steps of a magnesium silicate mineral carbonation process route results in input energy requirements that will exceed the output of a fossil fuel-fired power plant that produces the CO2 that is bound to (hydro-) carbonates. At the same time, fuel cells are not efficient enough to change this.

► Efficiency of a process with endo-/exothermic and electrochemical steps was assessed.
► Exergy analysis allows for Second Law of Thermodynamics-based efficiency evaluation.
► CO2 mineral sequestration with an electrolysis step seems not energy-effective.
► Fuel cells not efficient enough to compensate for electrolysis energy input needs.