This paper reports the construction and performance of an algae biofilm photobioreactor that offers a significantreduction of the energy and water requirements of cultivation. The green alga Botryococcus brauniiwas cultivated as a biofilm. The system achieved a direct biomass harvest concentration of 96.4 kg/m3with a total lipid content 26.8% by dry weight and a productivity of 0.71 g/m2 day, representing a light tobiomass energy conversion efficiency of 2.02%. Moreover, it reduced the volume of water required to cultivatea kilogram of algal biomass by 45% and reduced the dewatering energy requirement by 99.7% comparedto open ponds. Finally, the net energy ratio of the cultivation was 6.00 including dewatering. Thecurrent issues of this novel photobioreactor are also identified to further improve the system productivityand scaleup.
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