This paper (which has just appeared at Nature but behind a paywall) describes a very interesting idea for mineral carbonation. By heating limestone and various magnesium silicates (olivine, serpentine, augite) at 1200 C, an ion exchange reaction occurs that makes the resulting material highly reactive with CO2. At 1 bar the resulting material completely reacts with CO2 in just an hour, soaking up the CO2 released from the limestone as well as additional CO2. At atmospheric CO2 concentrations it takes longer, but still 1000x faster than normal weathering. The energy needed is claimed to be < 1 MWh/ton CO2, less than half that needed by leading DAC technologies.