Intensified Bio-Oil Extraction from Microalgae Integrating Renewable and E‑Fuel Production

The growing demand for alternatives to fossil fuels is driving research into biofuels and e-fuels (i.e., synthetic fuels made from captured CO₂ and renewable hydrogen via power-to-liquid processes), underscoring their important role in decarbonization and the global energy transition. Microalgae have emerged as a promising resource due to their high lipid productivity (∼80,000 L/ha/year), rapid biomass growth (∼50 g/m²/day), and capacity to capture up to 1.83 kg CO₂/kg biomass. However, challenges related to extraction efficiency, process scalability, and economic viability still limit industrial use. Addressing these issues, this review assesses the recent technological advances in bio-oil extraction from microalgae for renewable and e-fuel production, covering fuel platforms, corefining, and hybrid routes. Research indicates that hydrothermal liquefaction (HTL) as well as ultrasound- and microwave-assisted extraction techniques approach the technical requirements for commercial deployment. Ultrasound- and microwave-assisted extractions achieve lipid yields above 50 wt % (dry basis), while hydrothermal liquefaction enables wet biomass processing with bio-oil yields ranging from 20 to 55 wt %. A comparison with oilseed crops (e.g., soybean: ∼600 L/ha/year; canola: ∼1,200 L/ha/year) reveals that microalgae exhibit superior sustainability and productivity indicators, despite differences in microalgae structure and composition. Based on this review, the adoption of a circular-economy approach is recommended, with biomass pretreatment followed by hybrid extraction, which offers a promising framework to support decarbonization and large-scale e-fuel production.