ABSTRACT
Biofuel has been identified as nontoxic, biodegradable, and renewable fuel, which can contribute to the minimization of fossil fuel burning and greenhouse gas (GHG) production. This chapter provides the classification of first, second, and third generation of biofuels based on their substrates, products, advantages, and disadvantages. Microalgae can produce different biofuels with high contents and sufficient diversities, they have some problems, such as the growth conditions being relatively expensive with light requirements and CO2 and freshwater supply, the scale-up procedures being complicated, and the growth rate being low compared with that of other microorganisms. Bacteria present advantages in producing biofuels when compared with microalgae. Conventional biodiesels are mainly produced from vegetable oil or animal fat by chemical trans-esterification. The microbial production of bioalcohols, such as 1-butanol and 1-propanol, and biodiesel feedstock, such as fatty acid ethyl esters (FAEEs), has been reported using metabolic engineering strategies.
