A 1.2 kW, 2450 MHz resonant continuous microwave processing system was designed and optimized for oil extraction from green algae (Scenedesmus obliquus). Algae-water suspension (1:1 w/w) was heated to 80 and 95 degrees C, and subjected to extraction for up to 30 min. Maximum oil yield was achieved at 95 degrees C and 30 min. The microwave system extracted 76-77% of total recoverable oil at 20-30 min and 95 degrees C, compared to only 43-47% for water bath control. Extraction time and temperature had significant influence (p < 0.0001) on extraction yield. Oil analysis indicated that microwaves extracted oil containing higher percentages of unsaturated and essential fatty acids (indicating higher quality). This study validates for the first time the efficiency of a continuous microwave system for extraction of lipids from algae. Higher oil yields, faster extraction rates and superior oil quality demonstrate this system's feasibility for oil extraction from a variety of feedstock. (C) 2010 Elsevier Ltd. All rights reserved.