ABSTRACT
The global climate change, rising crude oil price, rapid depletion of fossil fuel reserves, and concern about energy security, land and water degradation have forced governments, policymakers, scientists and researchers to find alternative energy sources including wind, solar and biofuels. The biofuel production from renewable sources can reduce fossil fuel dependency and assist to maintain the healthy environment and economic sustainability. The biomass of currently produced biofuel is human food stock which is believed to cause the shortage of food and worldwide dissatisfaction especially in the developing nations. Therefore, microalgae can provide an alternative biofuel feedstock thanks to their rapid growth rate, greenhouse gas fixation ability (net zero emission balance) and high production capacity of lipids as microalgae do not compete with human and animal food crops. Moreover, they can be grown on non-arable land and saline water. Biofuels are generally referred to solid, liquid or gaseous fuels derived from organic matter [1]. The classification of biofuels is shown in Fig. 1. These classifications are: a) Natural biofuels, b) Primary biofuels, and c) Secondary biofuels. Natural biofuels are generally derived from organic sources and include vegetable, animal waste and landfill gas. On the other hand, primary biofuels are fuel-woods used mainly for cooking, heating, brick kiln or electricity production. The secondary biofuels are bioethanol and biodiesel produced by processing biomass and are used in transport
sectors [1]. The secondary biofuels are sub classified into three so called generations, namely, a) First generation biofuels, b) Second generation biofuels, and c) Third generation biofuels based on their different features such types of processing technology, feedstock and or their development levels [2].
