Maximum hydrogen production from genetically modified microalgae biomass

A transient mathematical model for managing microalgae derived H$_{\mathrm{2}}$ production as a source of renewable energy is developed for a well stirred photobioreactor, PBR. The model allows for the determination of microalgae and H$_{\mathrm{2}}$ mass fractions produced by the PBR in time. A Michaelis-Menten expression is proposed for modeling the rate of H$_{\mathrm{2}}$ production, which introduces an expression to calculate the resulting effect on H$_{\mathrm{2}}$ production rate after genetically modifying the microalgae. The indirect biophotolysis process was used. Therefore, an opportunity was found to optimize the aerobic to anaerobic stages time ratio of the cycle for maximum H$_{\mathrm{2}}$ production rate, i.e., the process rhythm. A system thermodynamic optimization is conducted with the model equations to find accurately the optimal system operating rhythm for maximum H$_{\mathrm{2}}$ production rate, and how wild and genetically modified species compare to each other. The maxima found are sharp, showing up to a \textasciitilde 60{\%} variation in hydrogen production rate within 2 days around the optimal rhythm, which highlights the importance of system operation in such condition. Therefore, the model is expected to be useful for design, control and optimization of H$_{\mathrm{2}}$ production.