Microalgae are a promising renewable feedstock for a diverse number of products such as fuels, fine chemicals,
nutraceuticals, and cosmetics. The extraction and processing of biochemicals from microalgae require the handling
of large volumes of feedstock, largely due to the small biomass to liquid ratio, typically b0.1% solids.
This work reviews the developments in microalgae harvesting and details the underlying phenomena of each
technology in relation to key physical parameters such as: size,morphology, surface charge, and density.A critical
appraisal of each method is given in relation to biomass concentration, biomass recovery, energy consumption
and integration into a biorefinery approach. Finally, we detail four microalgae harvesting case studies from
pilot-plants across Northwest Europe. The case studies are: (1) membrane filtration of Scenedesmus sp. used
for protein, carbohydrate and lipid extraction; (2) synergetic harvesting of cyanobacteria by autoflocculation
and passive capillary dewatering for the production of bioactive extracts; and, (3) bioflocculation and filtering
of wastewater-grown microalgae for the production of shrimp feed, biogas and fertilizer. Overall, this review
highlights that there is considerable scope for further innovation in harvesting processes, especially with synergistic
interactions that exploit multiple physical and chemical properties simultaneously.