Quantitative evaluation of bubble-column photo-bioreactors for bio-diesel production from microalgae using computational fluid dynamics

Renewable energy has been interested as a countermeasure for the fossil energy depletion and carbon dioxide reduction. Bio-diesel is one of the most desirable renewable energy because it can be an alternate diesel to petroleum. However, the bio-diesel from soybean or corn, for example, can be confronted with food crisis. Microalgae have recently been researched as a new bio-diesel source which contains higher growth rate than other plants. Microalgae residue also could be used for value-added products such as cosmetics, health functional food or pharmacy. Because pond production system has limitations in unstable weather conditions and insufficient land availability especially in Korea, photo-bioreactors is essential for their cultivation. In this study, computational fluid dynamics (CFD) was used to design an enhanced bubble-column PBR for mass production of microalgae. Multi-phase models including bubble movement, time step independent tests, and surface tension were considered to develop the CFD model. The model was enhanced and validated through Particle Image Velocimetry tests. Various types of PBRs were simulated and compared quantitatively based on the evaluation method of mixing efficiency in the PBRs. This research can be used as basic techniques for microalgae production on a large scale.