Large-scale biodiesel production using microalgae biomass of Nannochloropsis

The aim of this study is to investigate the large-scale algae production using Nannochloropsis sp. in indoor open ponds. One of the key factors in open pond productivity is the uniformity of distribution of nutrients and CO2. Therefore, the effects of paddlewheel speeds (1.4, 2.1 and 2.8 rad s−1) on the productivity were also evaluated. The culture system used in the experiment consisted of three raceway ponds of 2000-L capacity each. Other parameters such as growth medium (seawater), illumination (150 μmol m−2 s−1), pH (7.5 ± 0.2), water level (30 cm), and temperature (25 °C) were kept constant during the two weeks experiments. In general, the results revealed that higher lipid content and biomass can be obtained by varying paddlewheel speeds. With increase in impeller speed from 1.4 to 2.1 rad s−1 the biomass productivity significantly increased, which indicates that microalgae could access more nutrients, CO2 and illumination. The maximum growth of 46 g L−1 m−2 and lipid content of 52% were obtained after 14 days with 2.1 rad s−1. The amount of hydrocarbon was varied from 55 to 70 mg L−1 day−1 cell weight, showing the best combination of biomass productivity and lipid content in indoor conditions. The present study showed the best combination of biomass productivity and lipid content in indoor conditions.

► Higher lipid content and higher biomass can be obtained by varying paddlewheel speeds. ► With the increase in impeller speed from 1.4 to 2.1 rad s−1 the biomass productivity significantly increased. ► The maximum growth of 46 g L−1 m−2 and lipid content of 52% were obtained after 14 days. ► The amount of aliphatic hydrocarbon varied from 55 to 70 mg L−1 day−1 cell weight.