Electrophoresis is another potential method for separating the microalgae without the need for chemicals. In this method an electric field directs the microalgae to the external part of the solution. Electrolysis of water produces hydrogen, which adheres to the flakes of microalgae and carries them to the surface. There are several benefits to using this technique, including environmental compatibility, versatility, energy efficiency, safety, and selectivity (Mollah et al., 2004), but the high cost means that this method is rarely used on a large scale (Uduman et al., 2010).

According to Richmond (2004), one of the main criteria for selecting an appropriate pro­cedure to harvest the microalgal biomass depends on the type of bioproduct desired. In prod­ucts of low commercial value, sedimentation through gravity with the aid of flocculants can be applied. However, for high-value products such as human food, aquaculture, or drugs, the use of continuous operation centrifuges is recommended because they can process large vol­umes of biomass. Another criterion for selecting the method of harvesting is the humidity for the biomass (Grima et al., 2003). Gravity sedimentation is usually more diluted than the centrifugation method, influencing the downstream process (Mata et al., 2010).