Modeling Microalgae growth with Breakage Equation

Biofuels such as biodiesel and bioethanol, from microalgae are considered as one of the alternative fuel sources, which can replace petroleum. Therefore, a number of kinetic studies have been previously carried out to model the overall mass growth rate of microalgae. However, these studies failed to address more fundamental aspects such as microalgae population growth. The cell growth of a single-cell microalga is divided into four stages – “growing”, “ripening”, “maturing” and “division”. It has been found out that microalgae growth rate varies at different stages. In order to address such problems, a novel growth model based on the breakage equation has been initially developed until the stationary phase of the microalgae growth cycle. The breakage equation is widely used to model crystallization processes for representing size and population growth. In this paper, the model has been further developed to represent the entire lifecycle of microalgae that is, including the death phase of the growth cycle. The parameters obtained by using this model are specific to Chlorella vulgaris. The newly developed model is able to determine the population size distribution and the number of cells at a specific time. The model has been verified by experimental data by taking the measurements of mass concentration, number of cells, and size distribution at specified operating conditions.