Unit operations applied for microalgae-based solid–liquid separation

The consideration of efficient solid–liquid separation in the context of algae harvesting for biofuels is a critical factor in a holistic scale-up assessment to assure an economically viable process. This chapter will first introduce the range of solid–liquid technologies available for the separation of algal cells from the liquid medium, from the traditional, for example, centrifugation, to more novel flotation and membrane processes. The need for associated operations, including coagulation-flocculation, will be discussed. Subsequently, these pieces of equipment will be evaluated in terms of relative efficiency and economics for algal biomass separation. This will incorporate considerations of the influence of algal characteristics on separation, including cell morphology, cell physiology, and associated algal-derived organic matter. While it is not possible to provide recommendations as to the most appropriate solid–liquid process for algal biofuels, the outcome being highly dependent on the specific context, this chapter will ensure that the reader has an understanding of the various separation methods available and the criteria by which they should assess the suitability of each option given their own particular circumstances.