Clean Techn Environ Policy (2013) 15:1063–1068 DOI 10.1007/s10098-012-0570-6
ORIGINAL PAPER
Production of biodiesel as a renewable energy source from castor oil Farah Halek • Armin Delavari • Ali Kavousi-rahim
Received: 23 July 2012 / Accepted: 20 November 2012 / Published online: 27 December 2012 Springer-Verlag Berlin Heidelberg 2012
Abstract The constantly increasing demand for energy can result in a huge crisis at the end of fossil fuels era. To prevent such an awkward situation, studies on finding alternatives have been seriously undertaken since the first oil crisis in the 1970s. Biodiesel, with a history of more than a century, has always been a potential candidate. In this research, the process of producing biodiesel from castor oil, which is a highly adaptable plant to Iran’s climates was studied. Methanol and castor oil as reactants with 10:1 molar ratio and sulfuric acid as catalyst with mass percent of 3 were allowed to react through trans-esterification reaction under mild conditions. The results from gas chromatography–mass spectrometry (GC–MS) showed the purity of more than 94 % esters for any conducted experiments which count as a success for an oil with more complicated structure than other raw vegetable oils. GPC analysis illustrated that the castor oil has a molecular weight of 1,068, which is almost three times that of colza oil. Some significant chemical and physical properties of the product, such as kinematic viscosity, flash point, pour point, etc. were calculated to approve conformity to ASTM D6751 standards. Eventually, the polluted emissions were measured by an Orsat gas analyzer. The outcomes completely corroborate the assumption which claims that adding biodiesel to conventional diesel fuels has a strong influence on lowering CO2, CO, HC, and smoke. Keywords Biodiesel Castor oil Renewable energy Trans-esterification Motor emissions
F. Halek (&) A. Delavari A. Kavousi-rahim Department of Energy and Environment, Materials and Energy Research Center (MERC), P.O. Box 14155-4777, Tehran, Iran e-mail:
[email protected]
Introduction Depletion of fossil-based fuel resources and harmful effects of their use on environment are the two most compelling motives that instigate researchers to focus on ways of finding alternative energy sources instead of oil and the fractions. Among the renewable fuels, the ones that are produced from oilseeds and food waste as the sources are favored by the majority of researchers because of their ability to minimize air pollution and emission of greenhouse gases and also to achieve reduction of dependency on fuel import, which result in reducing the overall energy cost. Vegetable-based fuels are the main alternative sources for fossil-based fuels. Since these bio resources are used mostly in ordinary diesel engines, it is known as biodiesel. There is a variety of vegetable species from different climate regions, which have been used for this purpose including soybean, canola, sunflower, coconut, castor, palm, corn, cottonseed, etc. each of which can carry special amount of oil with its own specific characters. Another possible source is the waste edible oil. In this case, the production seems to be more economic and efficient (Demirbas 2007; Singh and Sharma 2009; Wang and Yang 2007). Recent official statistics show the thriving market for this product in almost 21 countries with a bright future in terms of demand. One common method employed recently for decreasing raw oil’s viscosity in accordance with the standards is to convert oils having one type of ester to modified fuels with more than one ester in their chemical structure, which is known as transesterification reaction. Technically, vegetable oils are formed by triglyceride molecules which, in the three series of equilibrium reaction with an alcohol, such as methanol or ethanol, convert to fatty acid esters or biodiesel. In the first stage, one molecule of ester from triglyceride is replaced by a hydroxide derived from alcohol to form diglyceride. In the second and
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third stages, the processes are the same as the first-stage replacement step, then proceeding further to form monoglyceride and finally glycerin. The important point to note is that every stage yields one molecule of methyl ester or biodiesel so as to enable us obtain the desired product of our objective (Gerpen 2005; Gerpen et al. 2004; Ghobadian et al. 2009).
F. Halek et al.
has greater number of notable advantages compared with other methods such as dilution, microemulsion, and pyrolysis (Banerjee and Chakraborty 2009; Demirbas 2009; Georgogianni et al. 2009; Nezahat et al. 2009). •
Biodiesel, an appropriate alternative for conventional fuels The combustion of biofuels reduces CO2 emission by almost 60 % compared with fossil fuels and also prevents emission of the most dangerous pollutants which are normally produced by conventional fossil fuels (Ghobadian and Rahimi 2006). Many of the developed countries have decided to develop an orientation toward agriculture as a main resource for biofuels. The most significant reasons for choosing biodiesel as a potential alternative fuels can be as follows; (Environmental Protection Agency 2002; He and Bao 2002; Kahraman 2008; Nwafor et al. 2000): •
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Renewability: the gestation period of planting oil seeds and the possibility of extracting oil in the longest scenario is less than a year, while the production of fossil fuels takes millions of years. Reduction of emissions from combustion. Longer engine life caused by combustion of benign and green fuel. Natural decomposition: 99.6 % in less than 21 days and 100 % in 30 days. No need for modifying diesel engines. Higher flash point which results in facile transportation and storage. The absence of aromatics and sulfur compounds. Higher cetane number. Ability to blend with petro–diesel in different levels.
Castor It is a flowering plant with large claw-shaped leaves including 5–11 deep serrated lobes. This plant with almost 1-m height has a special ability to grow even under arid conditions and in uncultivated regions. The fruit has a capsule containing three large seeds extraction of which can yield large amounts of oils. Castor seeds include a variety of constituents such as malic acid, glucose, and mostly ricinolein-containing oil (Ashok 2009; Murugesan et al. 2009).
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In this reaction, oxygen atoms are kept attached to the esters’ chain, so that the efficiency of combustion rises, and the emissions are also decreased. Hence, the biofuels produced by this method are known as oxygenated fuels, whereas in the pyrolysis, oxygen atoms are removed due to high temperature. Among the mentioned methods, trans-esterification has the highest yield. The process is not complicated, and there is no need to have special facilities.
After synthesizing the biodiesel, the product should be evaluated by comparing the chemical and physical characteristics with standards such as ASTM D6751. Consequently, those parameters that have the most significant effects on operation need to be determined: kinematic viscosity, flash point, pour point, water and sediment contents, and cetane number (Mustafa and Havva 2008; Sharma et al. 2009, Srivastava and Prasad 2000).
Experimental section In this section, the highlighted results out of series of experiments are mentioned briefly. The main objective is to determine the optimal factors for realizing the most efficient and economic condition, such as oil-to-alcohol (methanol) ratio, amount of catalyst (sulfuric acid), temperature, and time. The materials and instrument used in this research are listed in Table 1. The structure of oil was studied using gas chromatography–mass spectrometry (GC–MS) analyzer. As the free fatty acid (FFA) content is close to 10 %, we decided to use a catalyst that is not sensitive to FFA, and sulfuric acid was chosen consequently (Gerpen et al. 2004). The reactor includes mainly a 2-l flask container with two necks—one for thermometer and the other for coupling Table 1 List of materials and instruments
Biodiesel production Material
Sulfuric acid Instrument
Theoretical basis Reactants including vegetable oil and alcohol through the trans-esterification reaction yield biodiesel. Trans-esterification
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Oil Methanol Heating mantle Distillation tube Volumetric flask Beakers Thermometer
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Fig. 1 Process of biodiesel produced through transesterification reaction from castor oil
distillation tube—for the recovery of methanol. A heating mantle was also employed to maintain the temperature, with the container being kept stirred. For all the couplings, vacuum oil was used for the calibration. To determine the best molar ratio, samples with three different retios are considered: 6:1, 10:1, 15:1. GC–MS analyzer shows that after 90 min, the purity values of the products were, respectively, 70.4, 94.2, and 94.5 %, from which we find that the last two are extraordinarily good in terms of purity; however, considering the economic viability aspect, we concluded that 10:1 was the most optimal alcoholto-oil ratio. Details of the percent composition are as follows: •
ricinoleic acid methyl ester—80.7 %; linoleic acid methyl ester—5.3 %; oleic acid methyl ester—4.9 %; stearic acid methyl ester—1.6 %; and palmitic acid methyl ester—1.7 %.
In another experiment, the result after 3-h was about 97 %. Details of percent composition are as follows: •
ricinoleic acid methyl ester—83.3 %; linoleic acid methyl ester—5.5 %; oleic acid methyl ester—5.1 %; stearic acid methyl ester—1.6 %; and palmitic acid methyl ester—1.7 %.
However, when the reactants were kept under constant reaction condition for more than 3 h, the result illustrated that some of the methyl esters, formed previously, underwent decomposition over time, and so the yield of reaction decreased. Accordingly, the optimum time of reaction was
concluded to be between 90 and 120 min. In addition, the temperature was maintained at a constant temperature of 63 C, just because it is the boiling point of methanol. The stages of the whole process are depicted in Figs. 1 and 2 After production and separation, the characteristics, as mentioned before, should be evaluated for some designated experiments and finally, they are compared with the standards. The results are displayed in Table 2.
Evaluation of emissions In this experiment, a Belgium orsat gas analyzer—model AVL4000—was employed to calculate the parameters of pollution (Fig. 3). The analysis included measurement of vol.% of CO2 and O2 and, in addition, the concentrations of HC, CO, and NOx in ppm (Murugesan et al. 2008; Shiwu et al. 2009). As the whole analyzing process needs a volume of product more than a small laboratory sample, the mentioned reaction with 2-l flask container was conducted ten times under same conditions; the products obtained from all of them were then evaluated by GC–MS analyzer to verify the structural resemblance. Carbon dioxide The responses of four different blends to 1,400 and 2,000 rpm are explicitly displayed in Fig. 1. The results
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Fig. 3 Orsat gas analyzer AVL4000
The decreasing slope of 2,000 rpm curve is clearly steeper, which again is because of air-to-fuel weight (A:F) ratio. Unburned hydrocarbons
Fig. 2 a Biodiesel production setup; and b samples of biodiesel
Table 2 Some of the physical and chemical properties of biodiesel from castor oil compared with ASTM Property
Units
Biodiesel from castor oil
Limits
ASTM method
Flash point
C
220
Min 130
D93
Water and sediment
vol.%
0.05
Max 0.05
D2709
Kinematic viscosity
mm2/s
6.2
1.9–6
D445
Copper strip corrosion
–
2
Max 2
D130
Cetane number
–
48
Min 47
D613
Pour point
C
-17
–
D97
confirm the assumption of biodiesel’s contribution to cause the decrease in CO2 emission. Statistically, CO2 emissions in 1,400 rpm for biodiesel blends of 20, 10, and 5 are, respectively, decreased by 3.6, 12.16, and 7.9 %, whereas for the same blends in 2,000 rpm, they are decreased by 21.2, 15.2, and 9.5 %. Clearly, by increasing biodiesel in fuel blend, the CO2 emission decreases which is a sign of better combustion. The differences between 1,400 and 2,000 rpm can be explained by air-to-fuel weight (A:F) ratio. In 2,000 rpm, this ratio is approximately 24.6 which results in better combustion in comparison with A;F ratio = 18.3 in 1,400 rpm.
As in the case of carbon monoxide, the generation of unburned hydrocarbons or incompletely burned hydrocarbon is due to the lack of adequate amount of available air for combustion. The origin of these types of pollutants can be spotted somewhere inside the engines with no combustion flame. The amounts of HC in 1,400 rpm decreased by 50, 37.5, and 12.5 % for biodiesel blends of 20, 10, and 5 %, respectively. The corresponding results under the condition of 2,000 rpm are 60, 40, and 20 %, respectively (Figs 4, 5). According to Fig. 6, adding biodiesel to the final product brings down the amount of produced HC. Outlet smoke from exhaust The study of the amount of smoke released by combustion was carried out by the same analyzing method as applied for the pollutants discussed above The outcomes represent decreasing levels of smoke with the addition of biodiesel. Details of the outcomes indicate a better picture in favor of confirming the assumption. Under condition of 1,400 rpm for blends, and 20, 10, and 5 %, smoke decreased by 29.5, 25, and 12.05 %, respectively. The corresponding results for 2,000 rpm are 34.5, 23.7 and 16.3 % (Fig. 7) Concentration of outlet smoke is decreased with increasing oxygen content and decreasing C/H ratio. Existence of oxygen in biodiesel structure causes to obtain better fuel oxidation. Another reason for decrease in smoke is the lower C/H ratio for biodiesel than for conventional diesel fuels.
Results and discussion Carbon monoxide emission Results Fig. 2 shows the same procedures as above, which were conducted in the analysis for CO in 1,400 and 2,000 rpm. The outcomes confirmed the decline in CO emission.
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Since there exist a variety of oilseeds resources in Iran, biodiesel produced from castor seeds can be treated as a
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Fig. 6 Effect of biodiesel blends on HC emission Fig. 4 Effect of biodiesel blends on CO2 emission
Fig. 5 Effect of biodiesel blends on CO emission
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potential opportunity for investment especially because of the favorable weather conditions for cultivation and also the existence of non-edible species of castor seeds. Analysis for determining structural properties of castor oil was conducted using gas chromatography–mass spectrometry (GC–MS). Results show that about 10 % of oil contains FFA. Trans-esterification reaction was chosen to synthesize biodiesel from reactants including raw castor oil and methanol, in the presence of sulfuric acid as catalyst. The yield is more than 94 %. Significant properties of produced biodiesel are within the ASTM D6751 stipulated limits. Therefore, it is considered as safe for consumption. The largest decreases in the amounts of CO2, CO, HC, and smoke existing in emission gas were observed for B20, which means that increasing the amount of biodiesel in the fuel blend can lower the amount of the released pollutant after combustion. Thus, it can be concluded that B20 is the best candidate as green fuel among all the blends studied in the above experiment.
Fig. 7 Effect of biodiesel blends on outlet smoke
Suggestion • •
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It is advisable to utilize more efficient catalysts such as nano-catalysts. The passageway of fluids mix or any parts of setup in contact, such as filters, diaphragm pump, injector pump etc. should constantly be under observation to prevent erosion mostly caused by acidic catalyst Vibration levels of not only diesel fuels but also biodiesel fuels should be evaluated. Economic optimization for industrial production scales is absolutely necessary. The effects of additives on stability and cold weather performance should be considered. To better understand the process of combustion, both practical and theoretical simulations have to be carried out. Elimination of subsidies for fossil-based fuels and instead, imposition of lower levies of taxes and tariffs for direct or indirect sectors attached to biofuel industries should be considered.
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References Ashok P (2009) Handbook of planet-based biofuels. CRC, New York, p 21 Banerjee A, Chakraborty R (2009) Parametric sensitivity in transesterification of waste cooking oil for biodiesel production—a review. Resour Conserv Recycl 53:490–497 Demirbas A (2007) Progress and recent trends in biofuels. Prog Energy Combust Sci 33:1–18 Demirbas A (2009) Biodiesel from waste cooking oil via basecatalytic and supercritical methanol transesterification. Energy Convers Manag 50:923–927 Environmental Protection Agency (2002) A comprehensive analysis of biodiesel impacts on exhaust emissions. Draft Technical Report Georgogianni KG, Katsoulidis AK, Pomonis PJ, Manos G, Kontominas MG (2009) Transesterification of rapeseed oil for the production of biodiesel using homogeneous and heterogeneous catalysis. Fuel Process Technol 90:1016–1022 Gerpen JV (2005) Biodiesel processing and production. Fuel Process Technol 86:1097–1107 Gerpen JV, Shanks B, Pruszko R (2004) Biodiesel Production Technology. Iowa State University, D. Clements Renewable Products Development laboratory Ghobadian B, Rahimi H (2006) Evaluation of engine performance using biofuel blends. The first Combustion Conference of Iran (CCT1). Tarbiat Modares University, Tehran, Iran Ghobadian B, Najafi Gh, Rahimi H, Yusaf TF (2009) Future of renewable energies in Iran. Renew Sustain Energy Rev 13:689–695
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F. Halek et al. He Y, Bao Y (2002) Study on rape seed oil as alternative fuel for a single cylinder diesel engine. J Renew Energy 28:326–338 Kahraman B (2008) Biodiesel as an alternative motor fuel: production and policies in the European Union. Renew Sustain Energy Rev 12:542–552 Murugesan A, Umarani C, Subramanian R, Nedunchezhian N (2008) Bio-diesel as an alternative fuel for diesel engines—a review. Renew Sustain Energy Rev 12:482–493 Murugesan A, Umarani C, Chinnusamy TR, Krishnan M, Subramanian R, Neduzchezhain N (2009) Production and analysis of biodiesel from non-edible oils—a review. Renew Sustain Energy Rev 13:825–834 Mustafa B, Havva B (2008) A critical review of bio-diesel as a vehicular fuel. Energy Convers Manag 49:2727–2741 Nezahat B, Nebahat D, Dilhan MK (2009) Conversion of biomass to fuel: transesterification of vegetable oil to biodiesel using KF loaded nano-g-Al2O3 as catalyst. Appl Catal B 89:590–596 Nwafor OMJ, Rice G, Ogbonna AI (2000) Effect of advanced injection timing on the performance of rapeseed oil in diesel engines. J Renew Energy 21:433–444 Sharma M, Sarin R, Arif AK (2009) Studies on Guizotiaabyssinica L. oil: biodiesel synthesis and process optimization. Bioresour Technol 100:4187–4192 Shiwu L, Yunpeng W, Shengwu D, Yang Ch, Fenghua C, Fang Ch, Xiaohong W (2009) Biodiesel production from ErucaSativa Gars vegetable oil and motor, emissions properties. Renew Energy 34:1871–1876 Singh B, Sharma YC (2009) Development of biodiesel: current scenario. Renew Sustain Energy Rev 13:1646–1651 Srivastava A, Prasad R (2000) Triglyceride based diesel fuel. Renew Sustain Energy Rev 4:111–133 Wang L, Yang J (2007) Transesterification of soybean oil with nanoMgO or not in supercritical and subcritical methanol. Fuel 86:328–333
