Practical Design of Hybrid Photobioreactor System for Economic Feasibility and Environmental Sustainability

Modern photobioreactors for microalgae-based biofuel production face various budgetary challenges in comparison to its competitor design, the traditional open pond system. Herein, a novel design of a double-chamber hybrid photobioreactor is proposed, featuring low-cost components including a 3-W centrifugal pump and recyclable plastic modules for its solar flank, as well as derivatives from tubular and membrane photobioreactors. The hybrid photobioreactor exhibits reasonable hydrodynamic performance with a circulation time of 120 seconds and a mixing time of 38 seconds. A side-by-side runthrough of Chlorella vulgaris cultivation with the novel hybrid photobioreactor and a standard open pond system was done to compare growth rates and system performance under equal environmental conditions. Resulting measurements show that the hybrid photobioreactor produced a 34.87% comparatively greater amount of C. vulgaris by the tenth day of cultivation, demonstrating a significantly higher growth rate (P < 0.05). In contrast, wet-sludge lipid extraction processes show that the C. vulgaris culture grown in the open pond system held a substantially larger lipid accumulation than that of the hybrid photobioreactor, although the difference was not statistically significant (P > 0.05). The pilot-scale photobioreactor not only costed as little as the open pond system but also incurred 88.6% less expenses compared to a similarly designed bioreactor made of clear PVC material. Consequently, this project demonstrates the candidacy of the proposed low-cost hybrid photobioreactor design for microalgal biofuel production.