Currently, fossil fuel sources (petroleum oils or gas and coal) provide 90% or more of total energy consumption that creates environmental issues in society and the world. So, developing alternative and pollution free fuel sources for the world that can help in more energy security and clean environment development for all the biotic components of the earth via the mitigation of toxic gases or particulate matter is needed. Microalgal diesel is reported as a renewable energy source (that comes in third generation biofuel) with reduction up to 80% of toxic or polluted gases or particulate matter. There are several sources of raw materials (cooking oil, vegetable oils, or many other sources of lipids) used for biodiesel synthesis that also utilize chemical processes (transesterification) for conversions and then use fuel energy sources for transportation tasks. Many other biofuels can be made up using chemical reactions, fermentation, and heat energy to breakdown starches, sugars, and other complex carbohydrates and biodiesel can be refined to produce fuel energy for daily energy requirements. Except for biodiesel, other biofuels (bioethanol or n-butanol) are frequently used as pure or blended with gasoline fuels for transportation tasks. Biodiesel can be derived from fats or lipid contents that are synthesized by green plants, including algal or microalgal species. Biodiesel can be derived from waste oils and can also be extracted from grasses, algae, animal wastes, cooking oil, wastewater sludge, or others. This chapter discusses several parameters for microalgal biomass cultivation and extraction and also transesterification processes that are used for biodiesel synthesis.