Energy analysis of extractive-transesterification of algal lipids for biocrude production

Algae biomass is the most promising feedstock for biofuel production since it can provide a sustainable route to achieve independence from fossil fuel sources. Energy-positive biofuel production from algal biomass has been the major goal for many researchers in recent years. The search for efficient extraction and chemical conversion methods that produce high energy ratios has become an important endeavor in this field. In this regard, microwaves and ultrasound have been utilized as convenient mechanisms in algal biodiesel production. However, none of the studies reported on the energy analysis of the extraction and transesterification methods. Energy analysis of the extractive-transesterification processes using microwave (with ethanol and with ethanol and hexane as co-solvent) and ultrasound irradiations to produce biocrude from microalgae (Chlorella sp.) is presented in this paper. Power input and reaction volumes were varied to study the effects of power density and intensity on the biocrude yields. Results from this analysis show that a biocrude yield higher than 90% could be obtained with an energy input to output ratio of less than one when microwave irradiation is used as the heating mechanism.