Optimisation of carbon dioxide sequestration into bio-foamed concrete bricks pores using Bacillus tequilensis

The current technologies used for reducing CO2 emission are not sufficient to sequestrate the high amount of CO2 in atmospheric. This research rolls up a new direction of CO2 sequestration process in bio-foamed concrete bricks (B-FCB) using Bacillus tequilensis 401 as an acceleration factor of natural carbonation. The strain of B. tequilensis 401 was isolated from cement kiln dust (CKD) and adapted to B-FCB environment. It produces carbon anhydrase (CA) and urease enzymes to accelerate sequestration process of CO2. The sequestration of CO2 into B-FCB was optimised based on; concrete density (D), B. tequilensis 401 concentration (B), temperature (T), and CO2 percentage (CO2). Two methods were used in design of experiments (DOE) by Minitab 18 included; 2(k) factorial design and Response Surface Methodology (RSM) analysis. The results reveal that the factors exhibited significant effects on sequestration process. The optimal carbonation depth of B-FCB was 12.2 mm under the following conditions: 20 % of CO2, 3 x 105 cell/mL of B, 40 degrees C of T, and 1300 kg/m(3) of D at 28 days. B. tequilensis 401 in BFCB increased carbonation depth by 30 % compared to FCB at 28 days. The increase in carbonation depth resulted in increased formation of calcium carbonate (CaCO3) in B-FCB compared to FCB, which is confirmed by microstructure analysis using SEX, EDX, and XRD.