Algae, Third-Generation Energy Source: A Comprehensive Review on Methods from Cultivation to Biodiesel Production

An increase in population growth has elevated the energy demand, and diminished fossil fuel sources. Their combustion releases carbon dioxide and contributes to environmental pollution. This has initiated intensive research to find alternative sources for economic and environmental sustainability. Amongst all, biodiesel originating from oil crops is a biodegradable, environment-friendly substitute and has properties similar to fossil diesel. Algal sources are promising substrates that require only sunlight and water for oil production. They could fulfil global demand, reduce the use of petroleum-based diesel and have higher oil productivity than other oil-yielding crops. Therefore, the third-generation production of biodiesel through microalgae is the renewable choice to overcome the energy crisis. This review covers algal cultivation methods, including both open and closed systems, lipid-extracting techniques for taking out algal oil or lipids from microalgae, and biodiesel production by the transesterification process. This article aims to assist in selecting appropriate cultivation and extraction methods for biodiesel generation.