Mineralization of Gaseous CO2 by Bacillus megaterium in Close Environment System

Implication of ureolytic biocalcification process as an efficient carbon dioxide sequestration technology was evaluated with Bacillus megaterium culture growing in a closed environment system. In three experimental sets containing either 35 % v/v CO2 in headspace (set 1) or 50 mM urea in solution (set 3) or both (set 2), change in headspace CO2, soluble calcium, and pH were monitored during 8 days of incubation. In absence of urea, headspace CO2 content continued to increase in set 1 (up to 48 % v/v) without any carbonate precipitation. However, carbonate precipitation were obvious in urea containing sets (sets 2 and 3) utilizing all the added calcium (25 mM) in just 2 and 6 days, respectively. No headspace CO2 could be detected in set 2 at the end of experimental period, and analysis suggested that this was majorly (>53 %) attributed to the solubility trapping phenomenon. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis revealed that the precipitates were made up of calcite and major fraction of vaterite polymorph of CaCO3.