Currently, more than 75% of the world energy requirement is fulfilled by burning of conventional fuels such as petroleum, coal and natural gas which are categorized as non-renewable energy sources. The fast depletion of these energy sources leads to shortage, inadequate energy security and increased dependency to the imported oil as well as the increase in their price with the passage of time. The burning of fossil fuels emits green house gases (GHG), particulate matters, toxic volatile compounds and other harmful pollutants. Increased level of GHG such as carbon dioxide (CO2) raised atmospheric temperature and surplus the global warming. Therefore, in order to mitigate the international issues of environmental pollution, global warming and energy crisis there is an urgent need to investigate the renewable and greener source of energy. First Chapter of this dissertation contains general introduction about the drawbacks of conventional energy sources and followed by the benefits of renewable energy derived from different biomasses and biofuels specifically biodiesel. The suitability of feedstock, types of transesterification reaction, selection of alcohol and co-solvent have been discussed. The reported experimental parameters, biodiesel specifications and the current scenario around the globe have been provided. A brief introduction of algae and their classification particularly brown seaweeds have been given which is the selected feedstock for this research work. Second Chapter provides mainly literature survey on homogenous base catalyzed transesterification followed by production of biodiesel from seaweeds and brief introduction of Cystoseira indica and Scinaia hatei. The experimentation described various steps of sample collection and preparation for the extraction of algal oil. The efficiency index of different solvents were developed based on which n-hexane : diethyl ether (1:1) mixture was considered the best solvent system which extract out 2.81 ± 0.43 %w/w and 3.10 ± 0.27 %w/w of the oily contents from C. indica and S. hatei respectively. The refined oily contents were characterized and converted into biodiesel through homogenous base catalyzed transesterification. Fatty acid methyl ester (FAME) yield was obtained 89.0 ± 0.51 %w/w (2.50 %w/w of dried alga) and 90.6 ± 0.36 %w/w (2.81 %w/w of dried alga) from C. indica and S. hatei respectively. The chapter concluded that the seaweeds are renewable and carbon neutral source of energy and this study is helpful to mitigate the issues of energy crisis, environmental pollution and global warming. Third Chapter includes the detail about Dictyota dichotoma, heterogeneous catalysis and nano-catalyzed transesterification. Metal oxide catalysts such as calcium oxide (CaO), magnesium oxide (MgO), silicon dioxide (SiO2) and titanium dioxide (TiO2) were activated and characterized through modern techniques such as Atomic Force Microscopy (AFM) through the the analysis of particle size profile, surface morphology and porosity through topography. D. Dichotoma found to contain 4.02 ± 0.27% w/w of algal oil on dried basis by applying Bligh and Dyer method. The outcome of varying the concentration of catalysts, temperature, reaction time and methanol to oil ratio suggested that the rate of reaction and reaction yield depends on experimental condition of methanolysis to produce biodiesel (FAME). CaO produced high yield of 93.2% w/w FAME under moderate conditions of 5% w/w catalyst, 65° C, 3 hours and 18:1 molar ratio whereas MgO, ZnO and TiO2 produced 92.4%, 72.5% and 31.8% w/w FAME respectively at elevated condition of 225° C. Furthermore, heterogeneous catalysis considered much greener due to significant advantages for example, catalyst recovery and reusability, waste removal of water washing during neutralization step and reduced production cost. Fourth Chapter demonstrates the introduction of Sargassum tenerrimum and discussed the utilization of waste animal shells and bones generating in large quantities worldwide for the development of cost effective catalysts to produce biodiesel. Utilizing these waste materials for catalyst preparation is a renewable, environmental friendly and cost-effective option. Waste chicken egg shell, mussel cover shell and goat bone were domestically collected, cleaned and grounded. These powdered catalysts activated through calcination at 950° C for 6 hours which were insoluble in reaction mixture and their high alkaline values of 10.2 to 11.4 evident the presence of greater number of basic sites necessary for heterogeneous base catalyzed transesterification reaction. Mineral analysis showed 97.09%, 95.42% and 49.84% calcium as oxide in the activated catalysts obtained from egg shell, mussel cover and goat bone respectively as well as comparatively higher contents of 41.46% phosphorous as oxide in the catalyst derived from goat bone. Dried powder of S. tenerrimum extracted through Soxhelt apparatus using n-hexane produced 1.9 ± 0.3% w/w of oily contents which were converted into FAME. The yields so obtained were found to be 89.1%, 93.0% and 73.8% w/w by utilizing waste egg shell, mussel cover and goat bone respectively at 5% w/w catalyst concentration, molar ratio 12:1 (methanol: oil) after 5 hrs at 65 °C reaction temperature.