04-09-2012, 05:17 PM
Physical, Mechanical Properties and Oil Content of Selected Indigenous Seeds Available for Biodiesel Production in Bangladesh
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ABSTRACT
This study identifies the physical and mechanical properties and oil contents of seeds of four indigenous plants in Bangladesh, namely the Jatropha, Karanj, Castor, and Rubber. Physical properties such as length, width, thickness, slender ratio, weight and bulk density were measured to find out the size, shape and space required by the seeds. Mechanical properties like hardness and crushing strength of the seeds were determined as well. All these properties are necessary for processing and storage of the seeds for oil extraction. Hardness and crushing strength of the seeds were measured by a Manual Hardness Tester. Oil content was measured by chemical method (Cold percolation method). Among the four types of seeds, Rubber seed was the largest with a length of 21.2 mm followed by Karanj 17.9 mm, Jatropha 17.1 mm and Castor 11.8 mm. The slender ratio of Jatropha, Karanj, Castor and Rubber seeds were found to be 1.8, 1.2, 1.9 and 1.1 respectively. Jatropha and Castor seeds had similar cylindrical shape with rounded tips. Karanj seed was found to be circular and flat. Shape of the Rubber seed was rectangular, inflated but slightly flattened in thickness. Rubber seed was the heaviest (4.3 g), as its size was also biggest followed by Karanj (1.2 g), Jatropha (0.8 g) and Castor (0.2 g), respectively. Hardness were found to be 2.7, 1.9, 1.7 and 8.6 kg for Jatropha, Castor, Karanj and Rubber seeds while crushing strength were 38.1, 26.6, 24.1 and 121.2 kg/cm2, respectively. The oil contents of Jatropha, Karanj, Castor and Rubber seeds were 32.4%, 31.8%, 67.7%, 38.9% by weight respectively. All the four types of seeds contain satisfactory amount of oil which can be extracted commercially and checked for their suitability for the production of biodiesel.
INTRODUCTION
Bangladesh is heavily dependent on import of fossil fuel and coal. Such dependency makes economy of Bangladesh more vulnerable to external price shocks in the international energy market. Price of fuel in the international market has been showing rising trend since last few years. Bangladesh annually imports about 3.5 million tons of different fuel oils. Of them, some 1.3 million tons are crude oil, 1.45 million tons diesel, 380 tons kerosene, 215 tons jet fuel and 155,000 tons petrol and octane (Energy & Power, 2003). The search for alternatives of fossil fuels is a major environmental and political challenge also. A promising alternative source of fuel, called biodiesel, has already been developed and is being used in some countries. Biodiesel is a chemical compound of methyl ester derived from raw or used vegetable oils and animal fats. Biodiesel is considered "carbon dioxide neutral" because all of the carbon dioxide released during combustion is sequestered out of the atmosphere during crop growth. Recent environmental and economic concerns (Kyoto Protocol) have prompted resurgence in the use of biodiesel throughout the world.
Physical properties
Size, shape, weight, density, volume are some of the physical characteristics which are important in many problems associated with design of a specific machine or analysis of the behavior of the products. Size (length & width), weight, bulk density and moisture content of the seeds (Figure 1) were measured at the Processing Lab of the Department of Farm Power & Machinery, Bangladesh Agricultural University. The weight of the selected seeds (20 seeds from each type) were measured by a digital balance (TC-203, Denver Instrument Company, USA, with a readability of 0.001 g) and the average values were tabulated with standard deviation.
Mechanical Properties
The seed hardness was measured at BRRI (Bangladesh Rice Research Institute) by using a manually operated hardness tester (Kiya Seisakusho Ltd. Tokyo, Japan) (Figure 2). The seeds were loaded flat under the indenter which moved vertically. When the seed started to crack then the reading of the tester was observed. There were two load indicators: the black one turned due to pressure and went back to “zero” when the seed broke and the red one remained still after breaking the seed indicating the breaking load or seed hardness. It is expressed as kg force applied. The crushing strength was calculated with respect to the projected area of the indenter used. The diameter of the indenter was 3 mm.
Oil content and cake yield of the seeds
Figure 5 shows the average percentage of oil and cake obtained from the seeds. The figure indicates that Castor seed had much higher oil content (67.7%) followed by Rubber seed, Jatropha seed and Karanj seed respectively. The oil content of Rubber seed was found to be 38.9% while the oil content of Jatropha seed and Karanj seed was similar (32.4% and 31.8%, respectively). All the four types of seeds contain satisfactory amount of oil (based on the proposition by Armstrong,1991; Edward et al., 1994; Foidl et al.,1996 and Svelele,2009) for commercial extraction which can be checked for their suitability for the production of biodiesel.Yield of cake from the seeds were 68.8%, 67.6%, 61.3% and 32.3% for Karanj, Jatropha, Rubber and Castor seeds respectively just in reverse order of the oil contents of the seeds.
CONCLUSIONS
Investigations were made into some basic properties of four different types of seeds obtained from indigenous trees available in Bangladesh such as Jatropha, Karanj, Castor and Rubber useful for the design of processing and extraction system of oil from them. Oil content of these seeds were also determined to check their suitability for commercial extraction. Information on the physical properties (weight, length, width, bulk density and moisture content), and mechanical properties (hardness, crushing strength) of the seeds were recorded. Physical and mechanical properties of the seeds will also help to modify the existing mechanical oil expeller used for Brassica. Among the four types of seeds, Rubber seed was the largest in dimension with a length of 21.2 mm followed by Karanj 17.9 mm, Jatropha 17.1 mm and Castor 11.8 mm. The slender ratio of Jatropha, Karanj, Castor and Rubber seeds were found to be 1.8, 1.2, 1.9 and 1.1 respectively. Jatropha and Castor seeds had similar cylindrical shape with rounded tips. Karanj seed was found to be circular and flat. Shape of Rubber seed was rectangular, inflated but slightly flattened thickness. Rubber seed was the heaviest (4.3 g), as its size was also biggest followed by Karanj (1.2 g), Jatropha (0.8 g) and Castor (0.2 g), respectively. Rubber seeds showed the highest hardness (8.6 kg) followed by Jatropha (2.6 kg), Castor (1.9 kg) and Karanj (1.7 kg) respectively.