Large scale production of lipid for biodiesel from green microalgae using wastewater

Abstract

This study examined the potential for green microalgae to produce lipid that could be used for biodiesel production from wastewater substrate. Green microalgae has the potential to be used in the production of biodiesel because it accumulates 5.3211 g of lipid in 39.2246 g of centrifuged and oven-dried algae biomass, accounting for 13.57% of its dry cellular weight. This was obtained with wastewater substrate under open-culture growth conditions. The wastewater substrate contained phosphate, nitrate, nitrite, ammonia, and sulfate at relatively optimal concentrations for culturing algae. The algae assimilated 95% of these nutrients on average for growth until the stationary phase was reached in 13 days. The most rapid cell doubling time observed was 192 h, and the maximum biomass production rate observed was 0.00057 mg/mg/day, reaching a peak algae weight fraction of 0.00926 mg/mg in 13 days. This study also examined and presented the scale-up of growing green microalgae in an open raceway culture system for obtaining maximum lipid yield from a wastewater substrate. The cost-benefit analysis of designing and building such a system was also presented in this study. The open raceway system described and modeled in this study measured 8 m * 3 m * 0.6 m and had a capacity of 10,000 liters, yielding 0.45 kg of biocrude lipid for each cycle of green microalgae culture harvested.