Production Methodology of Biodiesel from Microalgae

International Journal of Applied Engineering Research. ISSN 0973-4562, Volume 8, Number 15 (2013) pp. 1825-1832 © Research India Publications http://www.ripublication.com/ijaer.htm

Production Methodology of Biodiesel from Microalgae Mukesh Kumar*1 and M.P. Sharma2 1

Alternate Hydro Energy Centre, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand- 247667, India. 2 Alternate Hydro Energy Centre, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand- 247667, India.

Abstract Energy is essential for economic development of the world. The global economy runs on the energy. The global economy depends on the fossil fuels but due to limited availability, land and water degradation and highly polluted limited the use of fossil fuels. Biofuel can be an alternative to reduce the dependency on fossil fuel and assist to maintain environment pollution free and economic suitability. Microalgae appear to be the source of renewable biodiesel that is capable of meeting the global energy demands. Microalgae use sun light and CO2 for their growth. Oil productivity of many microalgae greatly exceeds the oil productivity of the other crops. In a large scale plant, release of solvent contributes to the production of atmospheric smog and to global warming and is classified as a hazardous air pollutant. Thus, in order to reduce the waste water pollutant, increasing the FAME yields, reducing the production cost some more production technique should be introduced. This papers review the various production methodology for biodiesel production from microalgae Keywords: Energy, microalgae, In situ, transesterification.

1. Introduction Microalgae are microorganism cell that convert CO2 to potential biofuels and therefore are considered to have the potential to serve as feasible process for CO2 mitigation. These photosynthetic microorganisms are also useful in bioremediation applications and as nitrogen fixing biofertilizers [1-4]. The present review is about on microalgal biodiesel production method from microalgal oil. Microalgae can provide several

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different types of renewable biofuels such as methane, biodiesel and biohydrogen. The biodiesel from edible oil resources is impractical and infeasible as more than 50% of edible oil is imported to meet for food requirement in India. The non edible oil resources like Sal, Mahua, neem, pongamia and jatropha etc are viewed in India as potential feeds stocks for biodiesel. Recently, microalgae is being viewed as future source of biodiesel as it require very less land area, less time (24 hrs to 2 days) for maturity and give about 30 times or more oil yields than terrestrial oil need crops [5]

2. Potential Of Microalgal Biodiesel The enormous amount of burning of fossil fuel has increased the CO2 level in the atmosphere, which causing global warming. Biomass is as an alternative energy source to mitigate atmospheric CO2 through photosynthesis. Algae usually have a higher photosynthetic efficiency than other biomass. Biodiesel from microalgae appears to be a feasible solution in India, for alternative of diesel. The estimated annual consumption of petroleum product in India is nearly about 120 million tonnes per year and only microalgae have the capacity to replace this large volume of oil. It has been estimated that less than 2-3 percent of total Indian cropping land is sufficient to produce enough biodiesel to replace diesel currently used in country due to its high yield of oil per acre of cultivation. Clearly microalgae are superior alternative as a feedstock for large scale biodiesel production as shown in table 1[5]. Table I: Source of biodiesel and land area required for growth. S. No.

Crop

1 2 3 4 5 6 7

Corn Soybean Canola Oil palm Coconut Jatropha Microalgae

Oil yield (L/ha/yr) 172 446 1190 5950 2689 1892 136,900

Land area needed (M ha) 1540 594 223 45 99 140 2

The above table clearly indicates that the oil yield of microalgae is higher than the other edible and non edible oil seeds and land area needed is very less.

3. Algae Cultivation Producing biodiesel from microalgal biomass is generally more expensive than other crops. The cultivation of algae requires light, CO2, water and inorganic salts and temperatures remain within 20 to 30 °C. In order to reduce expense, biodiesel production must rely on freely available sunlight. Growth medium must provide the inorganic elements (nitrogen, phosphorus, iron and silicon) that constitute the algal

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cell. Microalgal biomass contains approximately 50% carbon by dry weight. Carbon is typically derived from carbon dioxide, producing 100 tonnes of algal biomass fixes approximately 183 tonnes of carbon dioxide. Biodiesel production can potentially use CO2 during daylights hours and also use carbon dioxide that is released in power plants by burning fossil fuels [6]. The practicable methods of large-scale production of microalgae are open ponds, Fermenters and tubular photobioreactors.

4. Harvesting of Algae Algal harvesting consists of recovery of biomass from the culture medium that constitutes about 20-30% of the total biomass production cost. Harvesting method include the centrifugation, filtration, combination of flocculation-flotation, ultra filtration sedimentation. Once the algae is harvested and dried, several methods like mechanical solvent extraction and chemical methods can be applied for oil extraction. Solvent extraction is usually applied to get high oil yields from algae [8].

5. Oil Extraction Technique There are various methods to extract the oil from microalgae among them four methods are well known for oil extraction: Mechanical press, Solvent extraction, Supercritical fluid extraction and Ultrasonic assisted.

6. Biodiesel Production Methodology Biodiesel (FAME) was prepared from algal biomass through two methods: first method is oil extraction from algal biomass followed by transesterification and second method is direct transesterification of algal biomass. In this case both dry as well as wet biomasses were used as feed stocks for biodiesel production. 6.1 Extraction Transesterification Method Transesterification of algal oil with simple alcohol has long been the preferred method for producing biodiesel The Transesterification process is most widely use all over the world. The overall Transesterification reaction is given by three consecutive and reversible equations as below: Triglyceride + ROH = Diglyceride + RCOOR Diglyceride + ROH = Monoglyceride + RCOOR + = + In the first reaction the conversion of triglycerides to diglycerides, followed by the Conversion of triglycerides to monoglycerides, and of monoglycerides to glycerol, yielding one methyl ester molecule per mole of glyceride at each step. The complete chemical reaction of the transesterification process is:

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Where R are long-chain hydrocarbons which may be the same or different with R=CH3/C2H5. As seen above, the transesterification is an equilibrium reaction in which excess Alcohol is required to drive the reaction close to completion. 6.2 In situ transesterification In situ transesterification differs from the conventional reaction in that the oil-bearing material contacts with alcohol directly instead of reacting with pre-extracted oil and alcohol. That is, extraction and transesterification done in single step, the alcohol acting both as an extraction solvent and an esterification reagent which enhances the

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porosity of the cell membrane, and would eliminate the need for extraction: yields found are higher than via the conventional route, and waste is also reduced [9].

7. Comparison of in Situ Transesterification Method and Traditional Two-Step Reaction Process Industrial biodiesel production from various oils involves isolation of oilseed glycerides by extrusion or solvent extraction, degumming and refining of the oil, and its alkali-catalyzed transesterification. This technology includes two steps at least extraction and transesterification. In a large scale plant, release of solvent contributes to the production of atmospheric smog and to global warming and is classified as a hazardous air pollutant. Thus, simplification of the oil production or esterification processes could reduce the disadvantages of this attractive bio based fuel. Table II: Comparison of Extraction-transesterification and in situ methods [10, 11, 12] S. No. 1 2 3 4

Insitu Transesterification

5 6

Heating value is high Yield is high Very simple process in operation Due to absence of extraction and dewatering the production cost is low Avoided the potential lipid loss Reduced the waste water pollutents

7

Less time consuming process

Extraction-Transesterification Heating value is low Yield is low Process is complex Production cost is less Lipid loss during process The waste water pollutes the environment Time consumption is high

8. Properties of Biodiesel from Different Oils The properties of different biodiesel, microalgal biodiesel and diesel fuels are given in table III. The table shows many similarities, therefore, microalgal biodiesel is rated as a strong candidate as an alternative to diesel. The transesterification process reduces the molecular weight to one-third, reduce the viscosity by about one-eight, and increase the volatility marginally. The kinematic viscosity of microalgal biodiesel is less compared to other biodiesel. Table III: Properties of biodiesel from different oils [10, 11] Vegetable oil methyl Kinematic viscosity Cetane Heating value Flash point esters (Biodiesel) @ 38°C (mm²/sec) number (MJ/kg) (°C) 4.9 54 33.6 176 Peanut 4.5 45 33.5 178 Soyabean 3.6 63 31.8 127 Babassu

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Palm Sunflower Tallow Microlagal Biodiesel Diesel 20% biodiesel blend

5.7 4.6 4.35 3.06 3.2

62 49 58.5 50 51

33.5 33.5 41 43.8 43.2

164 183 96 166 76 128

9. Conclusion It is concluded from the above literature is that the oil yield of microalgae is higher than the other edible and non edible oil seeds and land area needed is also very less. A comparison between the various cultivation techniques is given to choose the best technique. Release of solvent in extraction-transesterification process, contributes to the production of atmospheric smog and to global warming and is classified as a hazardous air pollutant. In situ transesterification method is a promising method which reduces the disadvantages of extraction-transesterification method. The fuel property of microalgal biodiesel is similar to diesel. So microalgal biodiesel can be an alternative of diesel.

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[10] M.B.Johnson, Z.Wen, “Production of Biodiesel fuel from the microalga Schizochytrium limacinum by direct transesterification of algal biomass”, Energy fuels, Vol.23, pp. 5179-5183, 2009 [11] G.Huang, F.Chen, D.Wei, X.Zhang, X.Chen, “Biodiesel production by microalgal biotechnology”, Applied Energy, Vol.87, pp. 38-46, 2010 [12] M.J.Haas, K.Wagner, “Simplifying biodiesel production: the direct or in situ transesterification of algal biomass”, Eur J Lipid Sci Technol, Vol.113, pp.1219-29, 2011

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