Overview of Microalgae Production Technologies

Abstract

Microalgae are fast becoming a favoured feedstock for the production of advanced biofuels including biodiesel, biocrude, bioethanol, biomethane, green diesel and biojet fuels. Algae for their growth require sunlight, COfrom waste streams, unproductive lands and poor quality waters which include seawater, brackish water and agricultural, municipal and industrial wastewaters. Algae biomass is rich in lipids, carbohydrates and proteins. Currently more emphasis is given to extract lipids from the algal biomass to produce drop-in fuels. Algae can be cultivated through photoautotrophic and mixotrophic mode of nutrition using open raceway ponds and photobioreactors (PBRs). Heterotrophic mode of nutrition requires closed bioreactors and needs organic carbon sources which may prove to be costly for biofuels production. Harvesting of algae is a major energy consuming process in the fuel production path. Techniques such as centrifugation, filtration, flocculation, flotation and electrocoagulation-flocculation are assessed for their energy efficiency and cost effectiveness for commercial-scale operations. Downstream processing of algal biomass including cell disruption and extraction requires innovative technologies. This book chapter discusses algae biomass cultivation, harvesting, cell disruption (techniques such as bead beating, sonication, and pulsed electric field) and extraction technologies (using solvents, ionic liquids, subcritical and supercritical fluids) in great detail for biofuel production.