Gas balances and growth in algal cultures

Abstract

This chapter reviews some of the most important aspects related to the growthof microalgae with their main substrate, carbon dioxide (CO2), and product, oxygen (O2). Both gases exist in the aqueous nutrient medium in dynamic equilibrium with the incoming CO2 contained in air and in the case of open systems, with the exterior environment. The concentrations of both gases, along with other environmental parameters including light, temperature, nutrients, etc. affect photosynthesis and, consequently, the growth rates and productivities. The effect of environmental conditions and medium composition is reviewed in terms of mass balances initially and then kinetic growth models based on these conditions. Transfer of CO2 and O2 is described and then integrated with cell kinetics highlighting recent developments in models describing dynamic system, along with advanced computational tools used in solving and representing the hydrodynamics in photobioreactors. Finally, an example with experimental results is presented. Detailed procedures to obtain parameters used in microalgal kinetics, mass transfer and hydrodynamics expressions are described and used to validate a dynamic model simulating the performance of an airlift photobioreactor inoculated with Scenedesmus sp.