Executive Summary : | Recently the rise in population has had many harmful impacts on our environment, mainly the dependency on fossil fuels for transportation, leading to greenhouse gas emissions. Global warming is the main reason for the depletion of natural fossil fuels. The need for change towards sustainable and renewable energy can be arranged by following third-generation microalgae-based biomass for fuel production. Microalgae-based biofuel production facilitates many advantages, i.e., cultivation of microalgae in wastewater that replaces artificial media cost and, on the other hand treating the wastewater as phycoremediation and high-value algal biomass will be generated. Many developed nations have accepted biodiesel and bioethanol as promising biofuels for CO2 mitigation. Microalgae known for their ubiquitous nature have been recognized as a fast growers and photosynthetic. They can produce high-value bio-compounds that accumulate in starch, lipid, protein and carbohydrate. The microalgae Chlorella sp. and Scenedesmus sp. have high lipid content as a monoculture. However, co-cultivation significantly increases lipid productivity compared to monoculture. Chlorella sp. consists of high glycogen percentage that transforms glucose into bioethanol. Microalgae-based treatment was a more suitable method of meagre operational cost, and it leads to biomass generation, which can be used further for deriving valuable products. Cultivation of microalgae in various wastewater offers many advantages and is highly recommended per the present energy and phycoremediation scenario. Considering the fact, the proposed study reverse osmosis rejection will be used to co-cultivate microalgae. Using reverse osmosis reject offers dual benefits; possible reclamation of RO reject by microalgae and high-value biomass will be generated for biohydrogen and carbon dots production. Biomass pretreatment is an essential step in microalgal-based biorefinery that demands considerable energy, making the biorefinery process unattractive for scaling up. Hence, in this research, an attempt is made to replace pretreatment with hydrothermal liquefaction. The algal-based hydrochar will be utilized for carbon dots production, and crude will be explored further for its potential as a substrate for dark fermentation. Nanoparticles will be used to enhance biohydrogen production during dark fermentation. Hydrogen fuel is still in development and has yet to be widely used. It is still considered an alternative energy source but needs more research and development to become cost-effective and build the necessary infrastructure for hydrogen fuel distribution. |