Recently, technologies that produce biofuels from microalgae are being studied worldwide. Alternative energy development is studied in order to solve energy shortage phenomena. Microalgae as future energy and resource were received worldwide attention. New renewable energy that made of microalgae makes carbon dioxide reduction effect and biofuel production possible. Especially, production of biodiesel based on microalgae biomass is one of the cost-effective approaches, because microalgae can be cultivated with water and carbon dioxide. To commercialize microalgae biofuel, the cost of microalgae product processing must be reduced. Mass culture and economical harvesting of microalgae are methods that can reduce the process cost.
In this study, the separation method was propsed by using ultrasonic waves for effective harvesting of microalgae. Experiments were conducted by considering four variables by ultrasonic separation process using the Taguchi method. These variables were applied to the continuous culture process and combined system to perform the experiments.
Growth curve was approximated for Gompertz model, Logistic model, and baranyi model from microbial growth prediction model in continuous culture. Based on the culture conditions of the estimated specific growth rate, the turbidity of the microalgae in the flat panel photobioreactor (PBR) was measured. Furthermore, an on-off control scheme was applied to the flat panel PBR in order to culture the microalgae continuously on the basis of turbidity. The parameters of the on-off control system were displayed by LabView.
To reduce the cost used in the process, an on?off control was implemented using the continuous culture and ultrasonic separation device to compose one combined system. Experiments were conducted on the combined system to increase production efficiency while simultaneously harvesting and performing mass culture of microalgae. We considered that as a result of these experiments, the production efficiency of biodiesel can be increased by reducing the labor power and consumption expenses that are incurred during the production process.