high temperature aqueous solvent direct air capture uses the same reaction as the production of cement
more than half of cement emissions come from the calcining process in the production of cement - limestone (CaCO3) is broken down into CaO and CO2. i learned from this technoeconomic paper on direct air capture that one type of DAC (high temperature aqueous solvent) uses the same chemical reaction. a sodium hydroxide (NaOH) solvent is sprayed into the air in the absorption and reacts with CO2 to form sodium carbonate (Na2CO3). to regenerate the solvent, the sodium carbonate is reacted with calcium hydroxide (Ca(OH)2) to form calcium carbonate (CaCO3) and regenerate the solvent (NaOH). the calcium carbonate is then broken to CaO and CO2, the CO2 is collected and the CaO is turned back into Ca(OH)2 to regenerate the solvent again.