Author:

Abstract:

Microalgae are generally assumed to achieve much higher areal productivities than agricultural crops. Microalgal biomass is poor in lignocellulose and rich in lipids and proteins, making it a valuable feedstock for biofuels or animal feed production. So far, however, the production cost of microalgae is still high and production is only economically feasible for high-value applications such as food supplements, natural pigments or poly-unsaturated fatty acids. To be able to use microalgae for low-value applications such as feed or fuel production or wastewater and flue gas treatment, the production cost has to be reduced by at least an order of magnitude. A significant reduction in the cost of microalgal biomass production will require cost-efficient methods for harvesting microalgae. We studied flocculation induced by high pH to preconcentrate microalgae, both freshwater (Chlorella vulgaris, Scenedesmus obliquus) and marine species (Phaeodactylum tricornutum, Nannochloropsis salina). In this presentation, the occurring mechanism will be explained in detail. Moreover, it will be shown that there is a significant effect of growth phase and medium salinity. Practical implications such as medium recycling, contamination and its potential consequence for biofuel production will be discussed. Finally, this technique will be compared to other flocculation techniques (electro-coagulation-flocculation and usage of biopolymers) in terms of mechanism, efficiency and implementation possibilities.