Energy-input analysis of the life-cycle of microalgal cultivation systems and best scenario for oil-rich biomass production

An energy-input analysis of the life-cycle of microalgal cultivation systems was performed to study the oil-rich biomass production from fast-growing microalgae, for biodiesel production purposes. We estimated and compared the energy demands for the algal biomass cultivation in open-ponds (OP) with that required in closed-system photobioreactors (PBR) based on the new technologies. We also present the best microalgal candidates that show the highest biomass productivity and lipid yield indoors (laboratory scale), and discuss their potential to be used for full-scale biodiesel production. The results show that the energy requirements are highly dependent on the final mass concentration and/or using industrial wastes, with PBR cultivation being the largest energy consumer. Our offered scenario to minimize energy inputs and to increase algal-oil yields considers the most ideal cases, which could be the most promising model for energy-efficient biofuel production. Although biodiesel production by any of these systems is still not economically competitive with fossil fuel, recent suggestions on how to increase the efficiency of both systems are discussed, based on our energy-input assessment, with a critical evaluation of all stages for large-scale production of oil-rich microalgal biomass. (C) 2015 Elsevier Ltd. All rights reserved.