Carbonation of chrysotile mining residues (CMR) was studied to expose the role of residue size and mineralogy, gas composition, liquid saturation and watering schemes in saturation-controlled porous beds. CO 2 uptake dynamics and evolution of carbonating residue were monitored in situ in terms of gaseous CO 2 absorbed and relative humidity, bed liquid saturation, electrical conductivity, pore-water pH, and pressure drop. CO 2 uptake was contributed both by facile carbonation of chrysotile fines and “domestic” brucite, and slow-paced carbonation of coarser magnesium silicate particles. Chrysotile carbonation was a function of fiber length while inhibited lizardite carbonation was indirectly observed. A CO 2 -lean carbonation regime was identified where CO 2 uptake increased linearly with the CO 2 fraction. This enabled extrapolating at very low CO 2 gas contents to assess CMR carbonation under natural atmospheric conditions. Reduction of saturation and backmixing in the liquid proved effective for the proliferation of Mg-supersaturated zones to enhance carbonation. Maintaining low liquid saturation via periodic liquid additions translated into improved carbonation because of inhibition of silanol-polymerization passivation. Partial pore saturation proved effective in stimulating carbonation, both in flow-through and in diffusive modes, especially at lower CO 2 fractions thus foreseeing implementation of useful optimization strategies to enhance ambient carbonation of CMR heaps.