Available online at www.sciencedirect.com
Bioresource Technology 99 (2008) 6656–6660
Short Communication
Transesterified sesame (Sesamum indicum L.) seed oil as a biodiesel fuel Abdurrahman Saydut a,*, M. Zahir Duz b, Canan Kaya b, Aylin Beycar Kafadar b, Candan Hamamci b a
Dicle University, Engineering and Architecture Faculty, Mining Engineering Department, TR-21280 Diyarbakir, Turkey b Dicle University, Science and Art Faculty, Chemistry Department, TR-21280 Diyarbakir, Turkey Received 9 March 2007; received in revised form 21 November 2007; accepted 22 November 2007 Available online 21 February 2008
Abstract The sesame (Sesamum indicum L.) oil was extracted from the seeds of the sesame that grows in Diyarbakir, SE Anatolia of Turkey. Sesame seed oil was obtained in 58 wt/wt%, by traditional solvent extraction. The methylester of sesame (Sesamum indicum L.) seed oil was prepared by transesterification of the crude oil. Transesterification shows improvement in fuel properties of sesame seed oil. This study supports the production of biodiesel from sesame seed oil as a viable alternative to the diesel fuel. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Biodiesel; Sesame; Oil extraction; Transesterification; Renewable energy
1. Introduction Sesame (Sesamum indicum L) is an oilseed herbaceous crop of the Pedaliaceae family. It is an economically important oil seed crop which is widely cultivated in many parts of the world, primarily in tropical and subtropical areas of the world, including India, China, Sudan, Burma, Tunisia, Egypt, Thailand, Mexico, Guatemala, El Salvador, Afghanistan, Pakistan, Bangladesh, Indonesia, Sri Lanka, Saudi Arabia and Turkey, and has recently been adapted to semi-arid regions (Elleuch et al., 2007; Koca et al., 2007; Uzun et al., 2007; Wu, 2007). It is an ancient cultivated plant and thought to have originated from Africa and Turkey is known to be the second genetic resource. Sesame (3 321 458 t) are produced in 7 554 200 ha areas in the world. In Turkey, it is grown in 43 000 ha areas and produces 23 000 t (Koca et al., 2007; Uzun et al., 2007). Sesame is widely used in food, nutraceutical, pharmaceutical and industry in many countries because of its high oil, protein and antioxidant contents. Hence, in several coun*
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tries like Germany, China, India and Turkey, ethnobotanical uses against health problems including cancer, cold, colic, etc. are common (Koca et al., 2007). The chemical composition of sesame shows that the seed is an important source of oil (44–58%), protein (18–25%), carbohydrate (13.5%) and ash (5%) (Elleuch et al., 2007). The main constituents of sesame seeds are oil and protein. Oil content ranges 57–63%, and protein from 23% to 25% (Tunde-Akintunde and Akintunde, 2004). The fat of sesame is of importance in the food industry due to its flavour and stability, and because it can be used to cook meals of high quality. Sesame oil contains sesamin and sesaminol lignans in its nonglycerol fraction, which are known to play an important role in the oxidative stability and antioxidative activity (Wu, 2007). The addition of unsaponifiable matter extracted from sesame seed increases the stability of sunflower oil. This stability is more pronounced in the case of unsaponifiable matter extracted from roasted sesame seeds due to a synergistic role. The most abundant fatty acids were oleic (43%), linoleic (35%), palmitic (11%) and stearic (7%) acids, which together comprised about 96% of the total fatty acids (Elleuch et al., 2007). Biodiesel is produced from animal fat, plant oil or waste cooking oil, and that can be used as the basis for a clean
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substitute for fossil fuel without any modification to diesel engines, boilers or other combustion equipments (Canakci, 2007; Gerpen, 2005; Ma and Hanna, 1999; Meher et al., 2006). Oil seeds have been one of the major biomass sources of fuel (Karaosmanoglu, 1999). It is renewable and does not contribute to global warming due to its closed carbon cycle. A life cycle analysis of biodiesel showed that overall CO2 emissions were reduced by 78% compared with petroleum-based diesel fuel. Its additional advantages include outstanding lubricity, excellent biodegradability, superior combustion efficiency and low toxicity, among others (Gerpen, 2005; Holser and O’Kuru, 2006; Ramadhas et al., 2005). The plant oils usually contain free fatty acids, phospolipids, sterols, water, odorants and other impurities. Because of these, the oil cannot be used as fuel directly. To overcome these problems the oil requires slight chemical modification (Canakci, 2007). There are three kinds of catalysts that can be used in transesterification reaction, a strong alkaline catalyst, a strong acid, and an enzyme. The main advantages of using a strong alkali as a catalyst are shorter reaction time and less amount of catalyst required in the manufacturing process of the transesterification reaction (Ma and Hanna, 1999; Meher et al., 2006). In the present study, sesame (Sesamum indicum L.) seed was investigated as an alternative feedstock for the production of a biodiesel fuel. Biodiesel was prepared from sesame seed by transesterification of the crude oil with methanol in the presence of NaOH as catalyst. Properties of sesame seed oil and biodiesel produced by transesterification were within the limits of ASTM and EN standards. 2. Experimental Sesame seeds used in the present study were provided from Agricultural Faculty of Dicle University in Diyarbakir, situated in SE Anatolia of Turkey in 2005. The seeds were cleaned manually to remove all foreign matter such as dust, dirt, stones and chaff as well as immature, broken seeds. In order to preserve its original quality, the sample was stored at an ambient temperature of 25 ± 3°C in sealed plastic bags prior to any conditioning. 2.1. Extraction of sesame seed oil Soxhlet extraction was employed to know the total oil content of the sesame seed. According to the Turkish Standard, traditional Soxhlet extraction was carried out in standard apparatus by standard methods using 250 ml n-hexane and 20.0 g sesame seeds the smallest particle size mixed with 20.0 g sand. After extraction 5 h, the extracts were concentrated and dried, and the solvent was then evaporated.
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molar ratio) and 1.5 g NaOH. The reaction was carried out for 2 h under reflux at 60 °C while stirring. The reaction was carried out using 100% excess methanol, i.e. molar ratio of methanol to oil is 6:1 and catalyst concentration of 0.5%. The reactor was equipped with reflux condenser to condense back the methanol escaping from the reaction mixture. The reaction mixture was then allowed to stand overnight and the methyl ester layer was separated from the glycerol layer using separatory funnel. After completion of reaction, crude glycerol was separated by gravity. The catalyst was removed by hot water washings. Phenolphthalein indicator checked the complete removal of the catalyst. Traces of moisture and unreacted methanol were removed by vacuum distillation. The distillation was continued until the loss in weight of ester was constant thus confirming the complete removal of moisture and unreacted methanol. The crude methyl ester was further purified by distilling-off the unreacted methanol under normal atmospheric pressure, washing several times with water, centrifugation and drying with vacuum destigator. After completion of the transesterification, the reaction mixtures were allowed to cool down to room temperature to produce two phases: crude ester phase and glycerol phase. This phase separation generally occurred quickly and can be observed within the first 10 min of settling, but the ester layer was opaque, indicating that the separation was incomplete. Experimental results showed that given enough time for complete settling, the opaque ester phase could turn crystalline and transparent. This complete separation could take as long as 8–18 h. In fact, during the settling, the transesterification process was still going on. Therefore, the longer the settling time, the more favorable are the separation and the conversion. All chemicals used were of analytical grade unless otherwise stated. 2.3. Analysis of sesame seed oil and biodiesel Kinematic viscosity at 40 °C was obtained using Koehler Kinematic Viscosity Bath Model K 23377 while in warm water bath. Pour point and cloud point were determined simultaneously using Tanaka Mini-Pour/Cloud Point Tester Model MPC-101A/101 L. For flash point, Tanaka Automatic Flash Point Tester Model APM-6T-A was used. Heating value was determined using IKA Calorimeter System C 2000 basic control calorimeter. C and S were determined by Carlo Erba 1108 Model elemental analyzer and Eltra CS 500 Carbon, Sulfur Determinator. Measurements of the density at 15 °C by Metler–Toledo densimeter. The iodine number, cetane number was calculated, while the acid value was obtained by titration (Meher et al., 2006). 3. Results and discussion
2.2. Production procedure for biodiesel Biodiesel derived from sesame seed oil was prepared by reacting 300 g of oil, 60 g CH3OH (approximately 6:1
Sesame oil contains a class of unusual compounds known as lignans, comprised of sesamin, sesamolin, and a small amount of sesamol (Wu, 2007). Sesame oil shows
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high stability to oxidation compared with other vegetable oils. It can also be used to prevent lipid oxidation in soybean, rapeseed, and sesame oil (Bozkurt, 2007). Sesame seed oil was obtained in 58 wt/wt%, by traditional solvent extraction in our laboratory. The high viscosity, low volatility and poor cold flow properties of triglycerides, which result in severe engine deposits, injector coking and piston ring sticking, have prevented them from being used directly in diesel engines (Marinkovic and Tomasevic, 1998; Szentmihalyi et al., 2002). Sesame seed oil was investigated as an alternative feedstock for the production of a biodiesel fuel. Although the oil content of sesame seeds varies widely, (37–63%), the average percentage of oleic and linoleic acid content in the sesame germplasms and cultivars is very similar (41.3% and 43.7%, respectively) (Baydar et al., 1999). A maximum conversion of 74% (oil to ester) was achieved using 100% excess methanol, i.e. molar ratio of methanol to oil is 6:1 and catalyst (NaOH) concentration of 0.5% at 60 °C. Sesame oil is used as the raw oil to be mixed with methyl alcohol in a molar ratio of 1:6, and the mixture then undergoes transesterification reaction in order to produce biodiesel. The fuel characteristics of the alkyl esters synthesized were evaluated according to ASTM standard methods (Antolin et al., 2002; Holser and O’Kuru, 2006; Ramadhas et al., 2005). The quality of biodiesel is most important for engine part of view and various standards have been specified to check the quality. Fuel properties of methyl esters of sesame seed oil compare well with ASTM D 6751-06 and EN 14214 biodiesel standards (Table 1). The major problem associated with the use of pure vegetable oils as fuel in diesel engines is caused by high fuel viscosity in the compression ignition. High viscosity leads to poor atomization of the fuel, incomplete combustion, cooking of the fuel injectors, ring carbonization, and accumulation of fuel in the lubricating fuel (Karaosmanoglu, 1999). Among the general parameters for biodiesel, the viscosity controls the characteristics of the injection from the diesel injector (Karmee and Chadha, 2005). The viscosity of fatty acid methyl esters can go very high levels and hence it is important to control it within an
acceptable level to avoid negative impacts on fuel injector system performance. Therefore, the viscosity specifications proposed are nearly same as that of the diesel fuel. Higher viscosity of oils had an adverse effect on the combustion in the existing diesel engines (Meher et al., 2006; Ramadhas et al., 2005). Even more than density, this is an important property regarding fuel atomization, as well as fuel distribution. The viscosity of vegetable oils is about ten times higher than that of diesel, with consequent poor fuel atomization, incomplete combustion, carbon deposition on the injectors and valve seats, and fuel build-up in the lubricant oils. This can, therefore, cause serious engine deterioration, hence, it is absolutely necessary to subject the vegetable oils to treatments that diminish the viscosity. Biodiesel not only has proper viscosity, boiling point, and high cetane number, but also is simple to use, biodegradable, nontoxic, and essentially free of sulfur and aromatics. The kinematic viscosity of the biodiesel sample produced in this work 4.2 mm2 s 1. Density is important mainly in airless combustion systems because it influences the efficiency of atomization of the fuel. The results obtained showed that for the condition studied, the biodiesel produced in this study had a density 0.8672 g cm 3. Flash point of a fuel is the temperature at which it will ignite when exposed to a flame or spark. The flash point of biodiesel is higher than the petrodiesel, which is safe for transport purpose (Ma and Hanna, 1999). The flash point of the biodiesel sample produced in this work has been found 170 °C. It is highly lower than flash point of sesame oil (245 °C). Two important parameters for low temperature applications of a fuel are cloud point and pour point. The cloud point is the temperature at which wax first becomes visible when the fuel is cooled. The pour point is the lowest temperature at which the oil specimen can still be moved. The pour point is the temperature at which the amount of wax out of solution is sufficient to gel the fuel can flow. Sesame seed oil ester has higher cloud point and pour point compared to No.2 petroleum diesel. Cloud point and pour point of produced biodiesel are 6 °C and 14 °C, respectively (Demirbas, 2005).
Table 1 Fuel properties of sesame seed oil and its methylester
%C % S (ppm) Kinematic viscosity (40 °C) Heating value (MJ/kg) Density (15 °C) Flash point (°C) Iodine number Neutralization number (mg KOH/g) Pour point (°C) Cloud point (°C) Cetane number
Sesame seed oil
Biodiesel
68.9628 0 25.78 39.5 0.899 245.0 82.45
62.1477 0 4.2 40.4 0.8672 170.0 80.32 0.3 14.0 6.0 50.48
10.0 1.0
ASTM D6751-06
EN 14214
15 ppm 1.9–6.0
10 ppm 3.5–5.0
0.50 max
0.86–0.90 >101 120 max 0.5 max
47 min
51 min
130.0 min
No. 2 petroleum diesel – % < 0.5 2.5–3.5 42.7 0.82–0.86 >55 – – –33 –16 49–55
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Cetane number is indicative of its ignition characteristics. The cetane number measures how easily ignition occurs and the smoothness of combustion. Higher the cetane number better it is in its ignition properties. Cetane number affects a number of engine performance parameters like combustion, stability, drivability, white smoke, noise and emissions of CO and HC (Ramadhas et al., 2006; Meher et al., 2006). Biodiesel has higher cetane number than conventional diesel fuel, which results in higher combustion efficiency. The cetane number of biodiesel varies widely in the range of 48–67 depending upon various parameters including oil processing technology and climatic conditions where feedstock is collected. Cetane number of the biodiesel sample produced in this work has been found 50.48. Neutralization number is specified to ensure proper ageing properties of the fuel and/or a good manufacturing process. It reflects the presence of free fatty acids or acids used in manufacture of biodiesel and also the degradation of biodiesel due to thermal effects. The iodine value is an important measure that allows determination of the unsaturation degree of the fuel. This property greatly influences fuel oxidation and the type of aging products and deposits formed in diesel engines injectors. Analyses of sample of the produced biodiesel revealed iodine value 80.32. The results show that, transesterification improved the important fuel properties of the oil like density, viscosity, flash point, acid value, etc (Table 1). The present experimental results support that methyl ester of sesame seed oil can be successfully used as diesel. Alternative fuel should be easily available, environment friendly and techno-economically competitive. Plant oils, being renewable, are widely available from a variety of sources and have low sulfur contents close to zero, and hence cause less environmental damage (lower greenhouse effect) than diesel. Among the biomass energy resources, the oil seed plants become more important than the other sources because of the climate of Turkey, which permit these types of plants to grow easily (Karaosmanoglu, 1999). Southeastern Anatolia Project is the largest regional development project in Turkey, and also one of the major projects in the world. It consists of dams, hydropower plants and irrigation schemes in the lower Firat (Euphrates) and Dicle (Tigris) basins, and accompanying growth of agriculture, transportation, industry, telecommunications, health and education sectors and services in the region (Bayazit and Avci, 1997). Sesame plant, with some advantages over other plants, is expected to become one of the major oil seed crops upon full implementation of the South-eastern Anatolia Project in the SE of Turkey (Beis et al., 2002). Sesame is usually planted in arid and semi-arid regions of the world and should be considered while planning crop irrigation projects in those regions. The plant is very responsive to environmental conditions and biotic factors such as temperature, humidity, precipitation and soil moisture, all of which can affect its yield and quality (Ucan et al., 2007). The improvement of
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oil content is of great importance in the breeding of sesame (Baydar et al., 1999). 4. Conclusions Sesame (Sesamum indicum L.) is one of the oldest edible oil crops and its seeds, used as a food source, contain up to 60% fat. Fuel properties of methylesters of sesame oil compare well with ASTM and EN biodiesel standards. Sesame oil has good potential as alternative diesel fuel, but its use in direct-injection engines is limited by high viscosity, low volatility and the polyunsaturated character of the triglycerides. Sesame seed oil transesterification is one approach to viable sesame seed oil-based fuel. This study used sesame oil as the raw oil to mix with methanol and sodium hydroxide (NaOH) to undergo a transesterification reaction. Sesame seed oil have about 7.5% less heating value than that of diesel oil due to the oxygen content in their molecules. Viscosity and density of methyl esters of sesame seed oil are found to be very close to that of diesel. The calorific value of biodiesel is found to be slightly lower than that of diesel (5.4%). The present experimental results support that methyl ester of sesame seed oil can be successfully used as diesel. References Antolin, G., Tinaut, F.V., Briceno, Y., Castano, V., Perez, C., Ramirez, A.I., 2002. Optimization of biodiesel production by sunflower oil transesterification. Bioresource Technology 83, 111–114. Bayazit, M., Avci, I., 1997. Water resources of Turkey: potential, planning, development and management. International Journal of Water Resources Development 13 (4), 443–452. Baydar, H., Marquard, R., Turgut, I., 1999. Pure line selection for improved yield, oil content and different fatty acid composition of sesame, Sesamum indicum. Plant Breeding 118, 462–464. Beis, S.H., Onay, O., Kockar, O.M., 2002. Fixed-bed pyrolysis of safflower seed: influence of pyrolysis parameters on product yields and compositions. Renewable Energy 26, 21–32. Bozkurt, H., 2007. Comparison of the effects of sesame and Thymbra spicata oil during the manufacturing of Turkish dry-fermented sausage. Food Control 18, 149–156. Canakci, M., 2007. The potential of restaurant waste lipids as biodiesel feedstocks. Bioresource Technology 98, 183–190. Demirbas, A., 2005. Biodiesel production from vegetable oils via catalytic and non-catalytic supercritical methanol transesterification methods. Progress Energy Combustion Science 31, 466–487. Elleuch, M., Besbes, S., Roiseux, O., Blecker, C., Attia, H., 2007. Quality characteristics of sesame seeds and by-products. Food Chemistry 103, 641–650. Gerpen, J.V., 2005. Biodiesel processing and production. Fuel Processing Technology 86, 1097–1107. Holser, R.A., O’Kuru, R.H., 2006. Transesterified milkweed (Asclepias) seed oil as a biodiesel fuel. Fuel 85, 2106–2110. Karaosmanoglu, F., 1999. Vegetable oil fuels: review. Energy Sources 21, 221–231. Karmee, S.K., Chadha, A., 2005. Preparation of biodiesel from crude oil of Pongamia pinnata. Bioresource Technology 96, 1425–1429. Koca, H., Bor, M., Ozdemir, F., Turkan, I., 2007. The effect of salt stress on lipid peroxidation, antioxidative enzymes and proline content of
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