                        ! Page 66 of 153 " !## $% Energy Balance and Exergy analysis of large scale algal biomass production K. Sudhakar 1* , M. Premalatha 2 K.Sudharshan 3 1 Energy department, Maulana Azad National Institute of Technology, Bhopal, India 2 CEESAT, National Institute of Technology, Tiruchirapalli, India * Corresponding author; e-mail: sudha_k@sify.com; tel.: +62-21-7560929; fax: +62-21-756-0549. Abstract: Microalgae Technology for the production of biochemical and bio fuels is emerging rapidly. Large-scale production facilities are necessary to fulfil the expected future demand for biodiesel and biochemical produced with algae. The present study assesses the sustainability of biofuel produced from microalgae and examines the environmental feasibility of a large-scale production through the use of energy balance and Exergy analysis adopting Life Cycle concept.Estimates of energy requirements for cultivation, harvesting, and oil extraction for algae biodiesel production are developed. Energy output in the form of algal biodiesel and the total energy content of algal biomass are compared to energy inputs required for algal cultivation & processing. Exergy analysis of algal-biodiesel cycle shows the overall process to be renewable. The results obtained indicate the energy content of the algae produced exceeds the energy required for cultivating algae. Keywords: Biodiesel, Large open pond, Life Cycle Analysis, Microalgae, Net energy Ratio 1. Introduction Without a doubt, the world is now dependent on alternate sources of energy. Eukaryotic microalgae represent a promising alternative renewable source of feedstock for biofuel production. With over 40,000 identified species; microalgae are one of the more diverse groups of organisms on Earth. Algae has seemed like a great renewable energy source because it's extremely efficient at creating energy from sunlight and it could potentially form closed loops for power plants - absorbing exhaust while creating new fuel. (Sheehan, 1998). hey naturally produce large quantities of biomass and many biomaterials, including lipids/oil. The theoretical maximum biomass and oil production of from microalgae has been calculated at 240 T ha -1 yr -1 and 57, 000 L ha -1 yr -1 for Indian Conditions.(Sudhakar.et.al .,2012), Algal biomass residues derived from the oil extraction process can be used to produce ethanol, and methane, and high-value biomaterials, such as biopolymers, carotenoids, and very long-chain polyunsaturated fatty acids.(Raja.R.et al.,2008) Microalgae naturally remove and recycle nutrients (such as nitrogen and phosphorous) from water and wastewater and carbon dioxide from flue-gases emitted from fossil fuel-fired power plants, providing an added environmental benefit (Li.Y.et al.,2008) The integration of wastewater bioremediation and carbon sequestration with biofuel production has not been demonstrated on Industrial scale. The micro algal research and development effort couples the use of microalgae for biofuels production with environmental bioremediation. However there are many challenges to be addressed which include refinement of the cultivation process, downstream processing of biomass and development of an economic feasibility model for commercialization of algae-based biofuels and biomaterials.Algae may be grown in large open raceway ponds or closed photo bioreactors. A number of closed photo bioreactors are being investigated, for cost-effective production of the algae. These include horizontal tubular, vertical tubular, thin film and helical/inclined systems. Productivity is higher in the case of algae cultivated in a photo bioreactor, but capitals and operating expenses are significantly higher than for open systems.(Chisti.Y.,2007) Fig. 1, Shows algae cultivation systems. (a)Open Pond (b) Tubular Photo bioreactor Fig 1: Algae Cultivation System Over the past two decades, algal-based biofuel research has progressed from outdoor large open pond to large-scale photobioreactor design and optimization, and downstream processing (i.e., harvesting, dewatering, and drying), to algal oil extraction. At the moment, algal biodiesels are not commercially produced and no economically viable production processes exist. Hence there exist many unknowns associated with the algae biodiesel production .Based on the state of the technology, there exists a need to quantify the energy and environmental sustainability effects of microalgae-to- biofuel process. PAPER CODE: OP-027