Microwave-Assisted extraction of lipids from Chlorella sp. using green solvents for sustainable biodiesel production

Abstract

Microalgal lipids are a promising renewable feedstock for sustainable biodiesel production, but conventional extraction methods are limited by long processing times, high energy use, and fossil-based solvents. This study evaluated microwave-assisted extraction (MAE) with four green solvents (2-MeTHF, ethanol, D-limonene, and a deep eutectic solvent) for lipid recovery from Chlorella sp. across 50–80 °C and 5–30 min. The highest yield, 28.7 ± 0.9% DW using 2-MeTHF at 65 °C/15 min, exceeded the Bligh & Dyer method (26.5 ± 0.8%) while cutting extraction time by over 95%. Kinetic modeling confirmed pseudo-first-order and Fickian diffusion behavior (R² > 0.96), and Response Surface Methodology identified an optimal region at 68–72 °C and 14–18 min (predicted yield 27.9–29.1%). Energy consumption at optimal conditions (∼0.42 kWh/g biomass) was substantially lower than Soxhlet extraction (1.47 kWh/g). 2-MeTHF also showed the most favorable neutral lipid fraction and lowest residual solvent levels (<5 ppm). These results identify MAE with green solvents, particularly 2-MeTHF, as an efficient and sustainable strategy for microalgal lipid extraction within a circular bioeconomy framework.