(143d) Microalgae Cultivation in Bioreactors for CO2 Mitigation from Power Plants Flue Gas and Fuel Production by Supercritical CO2 Extraction

Microalgae can consume CO₂ gas as a carbon source for growth. After the flue gas from power plants is recovered, CO₂ is separated. Part of the CO₂ can be used as a carbon source for microalgae cultivation. Cultivation of microalgae by photosynthesis in bioreactors utilizes CO₂ from power plant flue gas and solar energy as the energy source to produce microalgae, which can be used for biofuel production. Optimizing the culture conditions can increase CO₂ fixation rates. Biofuels from microalgae are similar to vegetable oils, and can thus be considered as potential substitute for fossil oil. There are several different ways for biofuel production from microalgae: supercritical CO₂ extraction, organic solvents extraction, pyrolysis, gasification, liquefaction, and anaerobic fermentation, etc. The utilization of scCO₂ as solvent for biofuel extraction appears more economic than organic solvent extraction, as the captured CO₂ from power plant flue gas can be used for this application. The process is solvent-free, thus avoiding the production of waste solvents. Fuel production from microalgae by scCO₂ extraction is more energy efficient than direct thermochemical liquefaction, which operates at high temperature (300 °C ?350 °C) and under catalyst, e.g., sodium carbonate. However, scCO₂ extraction can also be combined with liquefaction to make the whole process more efficient.