Biofuel production from microalgae: a review

The shortage of fossil fuels is actually a major economic issue in the context of increasing energy demand. Renewable energies are thus gaining in importance. For instance, microalgae-based fuels are viewed as an alternative. Microalgae are microscopic unicellular plants, which typically grow in marine and freshwater environments. They are fast growing, have high photosynthetic efficiency, and have relatively small land requirement and water consumption in comparison with conventional land crops biofuels. Nonetheless, selling biofuels is still limited by high cost. Here, we review biofuel production from microalgae, including cultivation, harvesting, drying, extraction and conversion of microalgal lipids. Cost issues may be solved by upstream and downstream measures: (1) upstream measures, in which highly productive strains are obtained by strain selection, genetic engineering and metabolic engineering, and (2) downstream measures, in which high biofuels yields are obtained by enhancing the cellular lipid content and by advanced conversion of microalgal biomass to biofuels. Maximum biomass and high biofuels production can be achieved by two-stage culture strategies, which is a win-win approach because it solves the conflicts between cell growth and biomass accumulation.