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. (C) 2013 Society of Chemical Industry