CaO　and　MgO　are　important　industrial　raw　materials　commonly　produced　by　either　the　decomposition　of　calcium　carbonate　at　about　900　°C,　or　the　calcination　of　dolomite,　a　mixed　calcium　and　magnesium　carbonate,　calcined　either　to　MgO.CaCO3　at　about　750　°C,　or　to　MgO.CaO　at　900　°C.　ln　this　research,　the　decomposition　reaction　of　104–147　μm　dolomite　and　limestone　particles　was　investigated,　both　without　and　with　steam　added　to　the　reaction.　A　series　of　experiments　was　performed　in　terms　of　relevant　parameters　such　as　time,　temperature　and　amount　of　H2O　added.　Reactants　and　reaction　products　were　fully　characterized　and　demonstrate　the　different　morphology　and　specific　surface　area　of　the　raw　carbonate　ores　and　the　calcined　oxides.　Adding　H2O　during　calcination　has　a　significant　positive　effect.　The　calcination　shows　that　steam　can　significantly　accelerate　the　reaction　rate,　and　reduce　the　decomposition　temperature　by　∼100　°C,　thus　reducing　the　cost　of　the　decomposition　by　increasing　the　yield　for　a　given　reaction　time,　while　also　reducing　the　required　sensible　heat　of　the　feedstock　and　combustion　air.　This　ultimately　reduces　the　amount　of　fossil　fuel　or　alternative　energy　carriers,　thus　reducing　the　CO2　footprint　of　the　system.　The　improved　operating　conditions　foster　the　use　of　concentrated　solar　calcination.　The　CO2　footprint　of　the　carbonate　decomposition　can　be　reduced　by　∼4%　in　traditional　kilns,　and　by　as　much　as　20%　if　concentrated　solar　kilns　are　used.　Both　applications　are　currently　investigated　in　pilot-scale　operations.　©　2022　Elsevier　Ltd