Improving the Energy Balance of Hydrocarbon Production Using an Inclined Solid-Liquid Separator with a Wedge-Wire Screen and Easy Hydrocarbon Recovery fromBotryococcus braunii

The green colonial microalgaBotryococcus brauniiproduces large amounts of hydrocarbons and has attracted attention as a potential source of biofuel. When this freshwater microalga is cultured in a brackish medium, the hydrocarbon recovery rate increases; furthermore, the colony size becomes large. In this study, the effects of such changes on the energy balance of harvesting and hydrocarbon recovery were studied via filtrate experiments on an inclined separator and extraction from a concentrated slurry. The inclined separator was effective for harvesting large-colony-forming algae. The water content on the wire screen of slit sizes larger than 150 mu m was 85% could be achieved. The input energy of the harvesting using the brackish medium with this separator was approximate to 44% of that using the freshwater medium with vacuum filtration, while the input energy of the hydrocarbon recovery using the brackish medium was approximate to 88% of that using the freshwater medium with pre-heating beforen-hexane extraction. Furthermore, the energy profit ratio of the process in the brackish medium was 2.92, which was approximate to 1.2 times higher than that in the freshwater medium. This study demonstrated that filtration techniques and hydrocarbon recovery fromB. brauniiwith a low energy input through culture in a brackish medium are viable.