Optimization of microalgae Scenedesmus SP. growth rate using a central composite design statistical approach

Abstract

In this research, growth rate of microalgae Scenedesmus sp. was modified by optimizing four effective factors. The operational energy efficiency factor (OEEf) of the photobioreactor was also considered in parallel. A central composite design statistical approach was implemented to evaluate the results. These factors were carbon dioxide concentration (0.038 (air), 2.0, 5.0, 7.0, 10.0%), aeration rate (0.2, 0.5, 1.5, 3.0, 4.0 vvm), initial inoculum concentration (0.140–0.430 g/l) and gas diffuser diameter (0.4, 1.0, 2.6, 4.0, 5.0 mm). All the factors were very significant at the defined ranges. The diffuser diameter also showed different effect when either low or high carbon dioxide concentration was applied. The optimized values (6.02% CO2, 0.39 vvm flow rate, 3.7 mm diffuser diameter and 0.180 g/l initial inoculation) would result the maximum growth rate of 0.525 g/l.d and high OEEf of 19.5 which was very significant. It was concluded that microalgae technology is a promising solution for carbon dioxide sink in large scale and biofuel production after optimizing the biomass production rate.