Modeling, Simulation, and Optimization of Hydrogen Production from Microalgae in Compact Photobioreactors

This study investigates the possibility of hydrogen production from microalgae depending on temperature, and cultivation medium microalgae, oxygen and carbon dioxide concentrations in compact photobioreactors (PBR). A mathematical model generated a system of time dependent ordinary differential equations (ODE) to predict hydrogen generation in the indirect biophotolysis process originating from microalgae cultivation in tubular compact PBR. The indirect biophotolysis consists of two stages: i) aerobic (microalgae growth with air supply) and ii) anaerobic (consumption of microalgae biomass with hydrogen generation without air supply). A Michaelis-Menten type expression was used to model the rate of H2 generation considering that oxygen and sulfur could inhibit the process. The model was adjusted and experimentally validated against measured H2 production from green microalgae. The maximum rate of hydrogen production from local wild microalgae Tetradesmus obliquus was 6.8 x 10-7 kgH2 kg-med1 d-1. The thermodynamic optimization of the system determined that the optimum time of the anaerobic stage was 11 days and 13 h. The herein obtained results demonstrated that it is reasonable to state that a fundamental anaerobic stage optimum time for maximum large-scale H2 production should be expected in any indirect H2 biophotolysis process, no matter the complexity of the actual system.