Currently, the use of fossil fuels dominates the energy sector, but it is highly polluting due to greenhouse gas emissions. To reduce these emissions, several alternative fuels have emerged, such as biodiesel, which can be produced from different raw materials such as algae and waste cooking oil (WCO). This chapter presents relevant information on the use of algae and WCO as feedstocks in biodiesel production, and the characteristic stages of the process using one or the other. It also highlights the challenges in the development of sustainable biodiesel production from these two raw materials. In addition, an analysis of life-cycle assessment reports was also conducted and some environmental impacts (global warming potential, ozone depletion potential, acidification, and eutrophication) of biofuels from microalgae and WCO with homogeneous and heterogeneous catalysts were compared.