Optimization of microalgae oil extraction under ultrasound and microwave irradiation

BACKGROUND Microalgae are one of the most promising biofuel sources that the world has to offer; nevertheless the conversion process is hampered by technical and economic problems that are mainly related to de‐watering and extraction. The efficiency of the process can be dramatically improved by means of non‐conventional techniques such as ultrasound (US) and microwaves (MW). Scaling‐up feasibility is strictly linked to reactor efficiency, energy consumption, environmental impact and overall cost. In the present work, the optimization of lipid extraction from Nannochloropsis gaditana microalga is investigated. RESULTS A series of selected solvent mixtures and procedures have been tested and compared. Conventional extraction procedures with chloroform/methanol mixtures and fast US‐ and MW‐assisted extractions with methanol gave comparable fatty acid (FA) w/w% from dried microalgae. The highest extraction yield and lowest energy consumption was found to occur under MW irradiation, especially at high temperatures and under pressure. CONCLUSION This study highlights the advantages of US‐ and MW‐assisted lipid extraction from microalgae, both in terms of efficiency and operational costs. © 2013 Society of Chemical Industry