The harvesting of biomass is the removal of biomass from the culture medium. This process can involve one or more steps, including chemical, physical, or biological methods. The tech­niques of recovering microalgal biomass from the culture medium can contribute to 20-30% of the total cost of the biomass (Mata et al., 2010). Some techniques for harvesting the biomass include sedimentation, flocculation, centrifugation, filtration, flotation, and electrophoresis. The costs of these operations are relatively high due to the low initial concentration of biomass and the fact that the cells are negatively charged and due to an excess of organic material, which contributes to its stability in a dispersed state (Brennan and Owende, 2010).

The selection of an appropriate harvesting method depends on the properties of the microalga, the cell density, size, and the desired specifications of the final product. The harvesting of the biomass has two steps: separation of the microalgal biomass from the culture medium and the concentration of biomass with removal of excess medium (Amaro et al., 2011).