Indian Journal of Geo-Marine Sciences Vol. 45(7), July 2016, pp. 823-829 Review Article on Microalgae: Future biofuel Priyanka Patel, Swetal Patel & R. Krishnamurthy * C. G. Bhakta Institute of Biotechnology, Maliba campus, Uka Tarsadia University, Bardoli, Dist. Surat, Gujarat -394 350, India. [*E-mail: krishnamurthy@utu.ac.in, krishnashanti@gmail.com] Received 22 May 2013; revised 25 February 2014 Uses of non renewable sources like petroleum increase the production of green house gases and global warming. To overcome these problems use of renewable sources is necessary. Microalgae are a renewable source of energy. We can produce biofuels like lipid, methane, bioethanol and hydrogen from them; they are more efficient than conventional plants and can be cultivated using simple methods. Main focus of this review article is to point out the role of microalgae in the production of biofuels, their biosynthesis and comparison of algal biofuel with other sources. [Key words: Petroleum, Microalgae, Biofuel, Methane, Bioethanol] Introduction Microalgae are classified as the most primitive form of plants. The mechanism of photosynthesis in microalgae is similar to that in higher plants, but they are usually more efficient converters of solar energy because of their simple cellular structure. They normally grow in suspension within a body of water 1 . They can double every few hours during their exponential growth period 2 .They commonly double every 24 hrs. During the peak growth phase, some microalgae can double every 3.5 hrs 3 . Microalgae are veritable miniature biochemical factories, and appear more photosynthetically efficient than terrestrial plants 4 and are efficient CO 2 fixers 5 .The ability of algae to fix CO 2 has been proposed as a method of removing CO 2 from flue gases from power plants, and thus can be used to reduce emission of GHG. Many algae are exceedingly rich in oil, which can be converted to biodiesel. The oil content of some microalgae exceeds 80% of dry weight of algae biomass 6 .The development of biofuels as a substitute fuel to supplement or replace conventional diesel is receiving great attention among researchers and policy makers for its numerous advantages such as renewability, biodegradability and lower gaseous emission profile. Also, concerns over increasing energy demand, continuous global warming effects, declining petroleum reserves, petroleum price hike and scarcities have raised the need to search for alternative renewable fuels 7-11 . This article will focus on the characterization, benefit and future applications of microalgae as an eco friendly and economically viable platform for the production of biofuels. Biofuels: Definition, Classification and Characterization The term biofuel is referred to a solid, liquid or gaseous fuel that is predominantly produced from biorenewable feedstocks 10 . The most common renewable liquid transportation fuels are bioethanol and biodiesel. These biofuels can replace gasoline and diesel respectively, in today cars with little or none modifications of vehicle engines. Biofuels can be classified based on their production technologies and feedstock: first generation biofuels (FGBs), second generation biofuels (SGBs), third generation biofuels (TGBs), and fourth generation biofuels (FoGBs). FGBs are produced from sugar, starch, vegetable oils or animal fats, while SGBs are made from non-food crops, like wheat straw, corn and wood. Fuels produced from algae, also called algal oils, are classified as TGBs. Finally, FoGBs include crops that are genetically engineered to consume more CO 2 from the atmosphere than the amount of CO 2 that will be produced during their combustion as biofuels. Moreover, some fourth generation technology