Dissolved and gaseous inorganic carbon sequestration using a close system cell-free ureolytic calcification process

Ureolysis mediated increase of culture medium pH, dissolved inorganic carbon (DIC) by Bacillus pasteurii and subsequent utilization of the cell-free broth on calcification mediated carbon (CO₂) capture was investigated. In an ureolytic process with an initial biomass of 80 mg/l, about 55 % of the original urea (100 mM) in the nutrient broth-NaCl medium was hydrolyzed over 24 h; this increased DIC to 1,145 mg/l and pH to 9.1. The gas phase CO₂ capture experiment, which used the culture medium supernatant in a closed system (liquid phase to headspace volume ratio of 1:3) containing 28.45 % v/v headspace CO₂ (g), was triggered by injecting 50 mM CaCl₂. The calcification process decreased both the headspace CO₂ and the liquid phase DIC to 18.48 % v/v and 942 mg/l, respectively, through precipitation of total 27.41 mM CaCO₃. Although only 21.8 % of the DIC input from ureolysis was actually captured as solid carbonate, solubility trapping (as soluble carbonate in DIC) effectively regulated CO₂ release into the atmosphere.