*1.2.1. Biodiesel*

Biodiesel has comparable engine performance to petroleum diesel fuel, while reducing sulfur and particulate matter emissions [5, 6]. Biodiesel is a biodegradable alternative fuel derived from renewable sources and is nontoxic in nature [7]. During the manufacturing process, triacylglycerols (TAGs) are transesterified with an acid or alkali catalyst to produce biodiesel and glycerol [8].

**Figure 2.** Biofuels derived from microalgae.

The algal biodiesel production processes fatty acid methyl esters (FAME). The chemical composition of biodiesel is generally produced by transesterification of algal oil in the presence of acid or alkali as a catalyst [5]. The biodiesel from algae can be derived directly from transesterification of algal biomass [9]. Alternately, it can also be produced by two-step process wherein the lipids are initially extracted and later on transesterified, though either of the processes involves lipid extraction through solvents and alcohols like methanol, isopropanol and petroleum ether [8, 10]. The process of direct transesterification is fast and cost-effective technology. Biodiesel generated from microalgae can be an excellent alternative to current diesel crisis, but in order to efficiently produce biodiesel from microalgae, strains with a high growth rate and oil content have to be selected [11].
