Carbon Dioxide Biofixation and Biomass Production from Flue Gas of Power Plant using Microalgae Mohammad Matin Hanifzadeh School of Chemical Engineering College of Engineering University of Tehran Tehran, Iran matinhanifzadeh@ut.ac.ir Mohammad Hossein Sarrafzadeh * School of Chemical Engineering College of Engineering University of Tehran Tehran, Iran sarrafzdh@ut.ac.ir Omid Tavakoli School of Chemical Engineering College of Engineering University of Tehran Tehran, Iran otavakoli@ut.ac.ir Abstract— Nowadays greenhouse gas emission induces environmental problems such as climate change worldwide. According to statistics, atmospheric CO 2 concentration increased from 280 ppm in 1800 to 380 ppm in 2004 and power plants account for 22% of global CO 2 emission. Microalgae have potential for up taking inorganic carbon during photosynthesis. They have advantage in containing high oil content which can be used for biofuel production. The effect of other pollutants such as NOx and SOx gases on these microorganisms growth should be evaluated if power plant effluent gas is sought to be injected into a photobioreactor. Among three evaluated microalgae, Chlorella vulgaris, Dunaliella tertiolecta and Scenedesmus obliqus, higher biomass productivity obtained from C. vulgaris. Keywords: Microalgae, Biofuel, CO 2 biofixation, Chlorella vulgaris, Scnedesmus obliqus, Dunaliella teritolecta I. INTRODUCTION Presently Fossil fuels account for about 80% of global energy demands. Excessive application of fossil fuels caused the environmental pollution and health disorders [1]. One of the main results of overusing of fossil fuel is global warming which is considered nowadays as a dilemma worldwide. Climate change is the major effect of increase in gaseous pollutants concentration in atmosphere which can induce catastrophic consequences in future. The main source of carbon dioxide emission, fossil fuels, represents about 75% of total carbon dioxide emission [2]. In this regard, application of renewable fuels is necessary to be replaced by fossil fuels. Biofuels, thanks to their zero emission, provide excellent opportunity for using as an alternative energy source [3]. Microalgae due to their high productivity per hectare and high oil content considered as the main potential alternative energy source which have economically ability to be replaced by previous energy resources [4]. Photosynthetic microorganisms utilize the inorganic carbon dioxide and nutrients for their growth. Therefore, they can be produced near to industrial plants with high pollutants emission such as power plants. The major advantage of establishment of photobioreactor near to other industries is the availability of cheaper inorganic carbon and nutrient resources which economically enhance the production of these microorganisms. Additionally, this can bring about biofixation of carbon dioxide and wastewater treatment simultaneously. Microalgae are generally cultivated in open systems using natural light because they are cheaper than the closed systems. However, these systems have some disadvantages rather than a closed system such as lesser productivity, exposure to external pollution, excessive necessitate of water due to water evaporation and lesser capability to control condition [5]. Some species such as Chlorella and Dunaliella are commercially attractive. Chlorella sp. is applied as health promoting molecules, food additives, animal nutrition and cosmetics. Respectively, Dunaliella sp. can be used in some commercial application such as drug industry, since it includes high amount of beta carotene, food supplements and cosmetics [6]. These species and some species such as Scenedesmus sp. thanks to their potentials of biomass productivity and lipid content are appropriate for biofuel production. Guveia et al. [7] reported lipid content of 5.1%, 16.7% and 17.7%, lipid productivity of 7.4 mg/l/day, 20 mg/l/day , and 15.9 mg/l/day, and also biomass productivity of 0.18 g/l/day, 0.12 g/l/day and 0.09 g/l/day for Chlorella vulgaris, Dunaliella tertiolecta and Scenedesmus obliqus. The rate of biomass productivity and as a result carbon dioxide fixation can be varied by different concentration of gaseous pollutants which exist in power plant effluent gas. Generally, the composition of exhaust gas of power plants after passing through electrostatic precipitator and desulfurization facility consist of 13% CO 2 , 10 ppm or below SOx and 150 ppm or below NOx. Microalgae can tolerate certain amount of these pollutants. Higher concentration can inhibit their growth owning to pH increase in cultural medium and biological reduction in the capacity of algal cell for CO 2 sequestration [8]. In this study, the effect of different composition in flue gas of power plant on the biomass productivity is analyzed by simulation of condition in a laboratorial scale. II. MATERIAL AND METHODS A. Microalgae cultivation The microalgae used in this study were Chlorella vulgaris, Dunaliella tertiolecta and Scenedesmus obliqus. The modified BG11 medium [9] was used for cultivation of Chlorella vulgaris and Scenedesmus obliqus. Dunaliella tertiolecta is cultivated in artificial sea water medium. They were kept in 250 ml Erlenmeyer flask containing 150 ml cultural medium