A comparative analysis of algal biomass densification methods aimed at the biofuel production

The reduced size of the cells (< 30 µm in diameter) and the low cell concentration of microalgae and cyanobacteria cultures (0.5 g/L on average) greatly hinder the densification of the biomass, a crucial step to becoming biofuel production from algal biomass economically viable. To identify the best densification method, about 90 studies applied to 60 different microalgae and cyanobacteria were compiled through an extensive literature survey, classified into eight methods of algal biomass densification, and analyzed regarding the harvesting efficiency, energy consumption, and costs. Low-cost methods (spontaneous settling, autoflocculation, and bioflocculation) can achieve high densification only with specific species and conditions. On the contrary, many species only achieve high densification using high-cost methods (centrifugation, membrane filtration, electrocoagulation). Based on the analyzed data, researchers should focus on selecting species that combine the desired characteristics for the downstream processes with their potential for biofuel production.