Kinetic modeling of microalgae growth and CO2 bio-fixation using central composite design statistical approach

The optimum growth (mu), CO2 bio-fixation (R-CO2) rates and the energy ratio (ER) of microalgae Chlorella vulgaris (C.v) were identified using central composite design statistical approach (CCD-SA). mu and R-CO2 parameters including temperature of photobioreactor (T-PBR), concentration of CO2 (C-CO2), nutrients (carbon, nitrogen and phosphorus), gas flow rate (Q(gas)), initial inoculum concentration (INden) and the solar light intensity (I-tot) were considered. Results revealed mild operational conditions in the range 20-25 degrees C, C-CO2 of 2.5-20% (v/v), Q(gas) of 0.5-0.8 vvm and I-tot of 50-200 mu E/m(2).s would generate considerable mu and R-CO2. The highest mu and R-CO2 with a significant ER of 19.5 were generated under CCD-SA optimized parameters of T = 25 degrees C, C-CO2 = 20%, Q(gas) = 0.5 +/- 0.05 (Std. Dev. = 0.04) vvm, total inorganic nitrogen (TN) = 19 +/- 2 (Std. Dev. = 0.1) mg-N/L, Total phosphorous = 7 +/- 1 (Std. Dev. = 0.7) mg-P/L, COD = 20 +/- 2 (Std. Dev. = 0.5) mg-COD/L, INden = 0.52 +/- 0.01 (Std. Dev. = 0.05) mg/L and I-tot = 150 +/- 2(Std. Dev. = 0.6) mu E/m(2)s). Microalgae technology can be considered as a promising technology for CO2 bio-fixation in a large scale with a sustainable value of the produced biomass for biofuel production. (C) 2020 Elsevier B.V. All rights reserved.