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

Abstract

The optimum growth (μ), CO2 bio-fixation (RCO2) rates and the energy ratio (ER) of microalgae Chlorella vulgaris (C.v) were identified using central composite design statistical approach (CCD-SA). μ and RCO2 parameters including temperature of photobioreactor (TPBR), concentration of CO2 (CCO2 ), nutrients (carbon, nitrogen and phosphorus), gas flow rate (Qgas), initial inoculum concentration (INden) and the solar light intensity (Itot) were considered. Results revealed mild operational conditions in the range 20–25 °C, CCO2 of 2.5–20% (v/v), Qgas of 0.5–0.8 vvm and Itot of 50–200 μE/m2·s would generate considerable μ and RCO2. The highest μ and RCO2 with a significant ER of 19.5 were generated under CCD-SA optimized parameters of T = 25 °C, CCO2 = 20%, Qgas = 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 Itot = 150 ± 2(Std. Dev. = 0.6) μE/m2s). 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.