Outdoor Cultivation of the Biodiesel Promising Microalga Scenedesmus obliquus in Municipal Wastewater: A Case Study

Abstract

Despite the promising research findings on microalgae as a feedstock for biodiesel, reduction of its production cost is still a challenge. One possible solution to overcome this problem is outdoor biomass production using wastewater as a growth medium. The present study aimed to evaluate the climate key parameters for Scenedesmus obliquus outdoor biomass production during different seasons, as one of the promising microalgae for biodiesel production. S. obliquus was grown continuously in municipal wastewater using bubble column photobioreactors (PBR) made of plastic sleeves arranged vertically in a pilot area of 6m 2 with a total working volume of ≈850 L. Biomass productivity showed positive correlation with light intensity and temperature (0.824 and 0.697, respectively). On the other hand, a negative correlation was recorded between biomass productivity and rainfall (-0.520). The average monthly biomass productivity increased from 13.6 to 20.9g dry weight (DW) m -2 d -1 by increasing of light intensity/temperature from 6.8 MJ m -2 /14.4°C to 15.8 MJ m -2 /29.6°C, respectively. At high rainfall of 14.5 mm d -1 , the biomass productivity was reduced to 14.0 g DW m -2 d -1 . The monthly biomass productivity ranged between 13.6 up to 20.9g DW m -2 d -1 with annual mean productivity of 17.8±2.8g DW m -2 d -1 . Although the used system showed high efficiency for algae cultivation, high light fluctuation in Shenzhen climate requires continuous regulation of biomass concentration in PBR to enhance the biomass productivity.