ABSTRACT
The rising energy demand with the increasing population and the exponential consumption of fossil fuels are leading to economic and environmental crisis. Alternate renewable energy sources are gaining attention over the last few years to supplement the energy demand and to reduce the carbon emissions. Due to their quick growth, microalgae have the potential to absorb CO2 with a special ability to generate biofuels. This chapter briefs the potentiality of algae as a renewable energy resource and covers the aspects of its cultivation, concurrent waste treatment with CO2 mitigation, and conversion to biofuels through hydrothermal liquefaction. Algal metabolism has been detailed, which includes harvesting of light, nutrients from the wastewater, and CO2 from the atmosphere or flue gas mixture. Wastewater effluents from different industries can be treated in simultaneous CO2 fixation from the atmosphere. This chapter includes the algal cultivation (open and closed ponds, waste stabilization ponds, and photo-bioreactors) and harvesting (mechanical, chemical, electrical, and biological) methods. Hydrothermal liquefaction, a thermochemical process, has been discussed for algal conversion to bio-oils. Algal biomass undergoes depolymerization followed by degradation and then recombination of fragmented components to yield biofuels. Both homogeneous and heterogeneous catalysts find their application to enhance the bio-oil yields.
