CEE Oct-Dec 2012

7 MICROALGAE FUEL SOURCE FOR THE F'JTUPE Recent research shows that biodiesel form microalgae is one of the most promising renewable biofuel with the potential to completely displace petroleum-derived transport fuel without adversely affecting the supply of food and other crop products - keeping the environment clean at the same time. *UC Banerjee and Priyanka Mishra ** The global economy thrives on energy. Currently, India is the sixth largest consumer of energy in the world, and will be the third largest by 2030, with its rising population and consequent consumption of power. At the same time, the country is heavily dependent on fossil sources of energy for most of its demand. Due to the limited crude oil reserves, India meets about 72 per cent of its crude oil and petroleum product requirements through imports, which are expected to expand further in the coming years. The continued use of fossil fuels is not sustainable, as they are finite resources and their combustion will lead to increased energy-related emissions of greenhouse gases. This has necessitated the aggressive pursuing of alternative energy sources-solar, wind , biofuel, small hydro and more. Biodiesel derived from oil crops is also a potential renewable alternative to petroleum. However due to the various issues biodiesel from oil crops and animal fats is not an ideal choice. Moreover it cannot satisfy even a small fraction of the existing demand for transport fuel. Recent research shows that biodiesel from microalgae is the most promising renewable biofuel with the potential to completely displace petroleum-derived transport fuel without adversely affecting the supply of food and other crop products, all this whi le keeping the environment clean. In fact the oil productivity of many microalgae like Botryococcus braunii and Schiochytrium greatly exceeds the oil productivity of the best oil producing crops. Microalgae Algae are the most robust organisms on earth, able to grow in a wide range of conditions and are prominently found in water bodies or damp places. Algae are used as food, as biofilters to remove pollutants from waste water and as indicators of environmental change. They are also used in space technology and in laboratory research. Commercially, algae are cultivated for cosmetics, pharmaceutica ls, nutraceuticals, and for aquaculture purposes. Algae are made up of prokaryotic as well as eukaryotic cells. All algae have plastids to carry out photosynthesis like plants. Chemically, algae contain proteins, carbohydrates, fats and nucleic acids in varying proportions. Depending on their type, the proportion of fatty acids in the overall mass of some algae may be up to 70 per cent. It is this fatty acid (oil ) that can be extracted and converted into biodiesel. Algae can be cultivated by two means i.e. ponds and photobioreactors. Algae capture light energy through photosynthesis and convert inorganic substances into simple sugars using the captured energy. For carrying out photosynthesis, algae need sunlight, C0 2 and water. Open ponds and lakes can be used for cultivation. Algae is the third generation feedstock for biodiesel with higher yield than second generation crops. Its yield is about 50 tonne of biodiesel per hectare per year against 2 tonne for competing feedstock such as jatropha. Its lipid content is also very high and better than any other crop. Its oil yield per unit area of cultivation can be further increased and a lot of research is currently on going in this field. Making biodiesel from algae oil is similar to the process of making biodiesel from any other oilseed and one can use the same conversion process to generate biodiesel. Pilot projects forecast that algae can provide more than 10,000 gallons of biodiesel per hectare per year. Recent advances in oi l extraction and transesterification could reduce the cost of making biodiesel from plant oils. Algae can be cultivated by two means i.e. ponds and photobioreactors. Algae capture light energy through photosynthesis and convert inorganic substances into simple sugars. There may be some challenges in converting algae oil into biodiesel using the transesterification process owing to the high free fatty acid (FFA) of algae oil. Using photobioreactors A photobioreactor is a controlled and closed system that enables high productivity of algae. It is a closed system where all the growth requirements of algae cultivation are controlled according to the requirement. The following parameters are generally followed for the growth of algae; temperature 16 - 27 °C, salinity 12-40 g/1 , light intensity 1,000-10,000 lux {depending on volume and density), photoperiod (light: dark, hours) 16:8 (min) 24:0 (max) and pH 7- 9. Photobioreactors facilitate a much better control of the culture environment such as carbon dioxide 33