Optimization of Alkali-Catalyzed Transesterification ofBrassica Carinata Oil for Biodiesel Production

M. Pilar Dorado,*,† Evaristo Ballesteros,‡ Francisco J. Lopez,§ andMartin Mittelbach#

Department of Mechanics and Mining Engineering, EUP de Linares, Universidad de Jaen,C/. Alfonso X el Sabio, 28, 23700 Linares (Jaen), Spain, Department of Physical andAnalytical Chemistry, EUP de Linares, Universidad de Jaen, C/. Alfonso X el Sabio,28, 23700 Linares (Jaen), Spain, Department of Agricultural Engineering, ETSIAM,

Universidad de Cordoba, Avda. Menendez Pidal s/n, 14080 Cordoba, Spain, Institute ofChemistry, Karl-Franzens-Universitat Graz, Heinrichstrasse 28, A-8010 Graz, Austria

Received May 27, 2003. Revised Manuscript Received October 5, 2003

Environmental concerns are driving industry to develop viable alternative fuels from renewableresources. On the other hand, to reduce food surplus, the Agricultural Policy of the EuropeanUnion (EU) obliges the European farmers to leave a percentage of the arable land as set-aside,where can be grown, as an exception, vegetables for nonfood purposes, i.e., energetic ones.Currently, fossil fuels are used in diesel engines and are essential in industrialized places. Inaddition, petroleum-based diesel increases environmental pollution. To solve these problems,transesterified vegetable oil that has been grown in set-aside lands can be considered to be arenewable energy resource. In this sense, this work describes the optimization of the parametersinvolved in the transesterification process of Brassica carinata oil. Gas chromatography was usedto determine the fatty acid composition of Brassica carinata oil and its esters. Results revealedthat the free fatty acid content is a notorious parameter to determine the viability of the vegetableoil transesterification process. In this sense, it was not possible to perform a basic transesteri-fication using Brassica carinata oil with a high erucic acid content. The transesterification processof Brassica carinata without erucic acid required 1.4% KOH and 16% methanol, in the range of20-45 °C, after 30 min of stirring. Our results suggest that the greater the presence of KOH,the lesser the methanol requirements. However, this is valid only under certain limits. Also, ifthe presence of KOH or methanol is lower or higher than the optimal values, the reaction eitherdoes not fully occur or leads to soap production, respectively. Based on this field trial, biodieselfrom Brassica carinata oil could be recommended as a diesel fuel candidate if long-term engineperformance tests provide satisfactory results.

Introduction

More than 350 oil-bearing crops have been identified,among which mainly sunflower, safflower, soybean,cottonseed, rapeseed, and peanut oils are considered tobe potential alternative fuels for diesel engines.1 Nev-ertheless, other unknown oleaginous crops, which arebeing grown in less-favored countries, could performwell as an adequate fuel with chemical and physicalproperties similar to those of diesel fuel.

In addition, the set-aside rules of the European Union(EU) Agricultural Policy specify a minimum area ofobligatory set-aside land of the total arable area (10%in 2001), but also permit up to 50% of the total claimedarea to be put into the voluntary set-aside category.However, increasing the set-aside area could lead toerosion problems and may have an impact on arable

land. Nevertheless, an exception has been introducedinto the rules for managing set-aside land, which allowsfarmers to cultivate crops for nonfood purposes. In thissense, Brassica carinata (Ethiopian mustard) is anadequate oil-bearing crop that is well-adapted to mar-ginal regions (i.e., Andalusia (Spain), which is one ofthe poorest regions of the EU). In fact, this crop, whichis originally from Ethiopia, is drought-resistant andgrown in arid regions such as Andalusia.2,3 Moreover,nonfood cultures in set-aside lands can significantlydecrease the enormous amount of subsidies spent foragricultural overproduction in Europe, which leads toan increase in farmer incomes as well as the creationof new employment. For these reasons, Brassica cari-nata constitutes an interesting alternative to diesel fuelin less-favored regions.

* Author to whom correspondence should be addressed. E-mail:mpdorado@ujaen.es.

† Department of Mechanics and Mining Engineering.‡ Department of Physical and Analytical Chemistry.§ Universidad de Cordoba.# Karl-Franzens-Universitat Graz.(1) Peterson, C. L. Trans. ASAE 1986, 29, 1413-1422.

(2) Kimber, D. S.; McGregor, D. I. The Species and Their Origin,Cultivation and World Production; In Brassica Oilseeds: Productionand Utilization; Kimber, D. S., McGregor, D. I., Eds.; CAB Interna-tional: Wallingford, Oxon, U.K., 1995; pp 1-7.

(3) Mendham, N. J.; Salisbury, P. A. Physiology: Crop Development,Growth and Yield; In Brassica Oilseeds: Production and Utilization;Kimber, D. S., McGregor, D. I., Eds.; CAB International: Wallingford,Oxon, U.K., 1995; pp 11-64.

77Energy & Fuels 2004, 18, 77-83

10.1021/ef0340110 CCC: $27.50 © 2004 American Chemical SocietyPublished on Web 11/13/2003

However, vegetable oils are composed primarily of thefatty esters of glycerol (triglycerides), with a chemicalstructure that differs from diesel fuel. In fact, vegetableoils used as fuel report several problems that have beenidentified, i.e., the high viscosity and high molecularweight cause poor fuel atomization (which leads to in-complete combustion) and low volatility, respectively.4,5

In this sense, the transesterification of vegetable oilsconstitutes an efficient method to provide a fuel withchemical properties that are similar to those of dieselfuel. This chemical reaction resembles the conversionof an organic acid ester into another ester of the sameacid (Scheme 1).

Although it is a well-known process since, in 1864,Rochleder described glycol preparation through theethanolysis of castor oil,6 the proportion of reagentsaffects the process, in terms of conversion efficiency,7and this factor differs according to the vegetable oil.Several researchers have identified the most importantvariables that influence the transesterification reaction,namely, the reaction temperature, the type and amountof catalyst, the ratio of alcohol to vegetable oil, thestirring rate, the reaction time, etc.8-12 In this sense, itis important to characterize the oil (i.e., fatty acidcomposition, water content, and peroxide value (PV)) todetermine the correlation between them and the feasi-bility to convert the oil into biodiesel.12,13

The fatty acid composition of the oils seems to havean important role in the performance of biodiesel indiesel engines. According to Knothe and Dunn,14 satu-rated hydrocarbon chains are especially suitable for

conventional diesel fuel. In this sense, Ethiopian mus-tard presents up to 6% saturated hydrocarbon chains(Table 1), whereas sunflower oil, canola oil, and soybeanoil methyl esters present up to 4.8%-12.1%, 5%-7%,and 4.7%-17% saturated chains, respectively.

Based on the fatty acid composition and many otherparameters, the EU is about to approve the fatty acidmethyl esters requirements and test methods (EuropeanStandard EN 14214). According to this prenorm, themaximum amount of linoleic acid methyl ester can be12%. Also, the iodine value is limited to 120. Theseparameters exclude the use of the biodiesel from sun-flower oil, which is one of the main oleaginous crops thatare grown in Spain and other southern countries of theEU. In fact, research related to biodiesel from sunfloweroil has been seriously criticized. However, some re-searchers have found that biodiesel from sunflower oilperforms adequately in diesel engines.15-17 This obser-vation indicates that more research is needed before theapproval of the future EU standard for biodiesel.

Because the chemical properties of the esters deter-mine their feasibility as fuel, the intent of this work isto investigate and optimize the parameters involved inthe transesterification of Brassica carinata oil for fueluse, to develop a low-cost chemical process, and to deter-mine the influence of the chemical properties of the oilin the transesterification. Transesterification tests were

(4) Goering, C. E.; Schwab, A. W.; Daugherty, M. J.; Pryde, E. H.;Heaking, A. J. Trans. ASAE 1982, 25, 1472-1483.

(5) Bagby, M. O. Vegetable Oils for Diesel Fuel: Opportunities forDevelopment; American Society of Agricultural Engineers: St. Joseph,MI, 1987; ASAE Paper No. 87-1588.

(6) Formo, M. W. J. Am. Oil Chem. Soc. 1954, 31, 548-559.(7) Freedman, B.; Pryde, E. H.; Mounts, T. L. J. Am. Oil Chem. Soc.

1984, 64, 1638-1643.(8) Peterson, C. L.; Reece, D. L.; Cruz, R.; Thompson, J. A Com-

parison of Ethyl and Methyl Esters of Vegetable Oil as Diesel FuelSubstitute: Liquid-Fuels from Renewable Resources; Proceedings ofAlternative Energy Conference; American Society of AgriculturalEngineers, 1992; pp 99-110.

(9) Isigigur, A.; Karaosmanoglu, F.; Aksoy, H. A. Appl. Biochem.,Biotechnol. 1994, 45, 103-112.

(10) Muniyappa, P. R.; Brammer, S. C.; Noureddini, H. Bioresour.Technol. 1996, 56, 19-24.

(11) Zheng, D.; Hanna, M. A. Bioresour. Technol. 1996, 57, 137-142.

(12) Coteron, A.; Vicente, G.; Martinez, M.; Aracil, J. Recent Res.Dev. Oil Chem. 1997, 1, 109-114.

(13) Anggraini, A. A. Wiederverwertung von Gebrauchten Speiseolen/-fetten im Energetisch-Technischen Bereich -ein Verfahren undDessen Bewertung; Dep. AgrarTechnik, Universitat GesamthochschuleKassel: Witzenhausen, Germany, 1999; p 193.

(14) Knothe, G.; Dunn, R. O. Biofuels Derived from Vegetable Oilsand Fats. In Oleochemical Manufacture and Applications; Gunstone,F. D., Hamilton, R. J., Eds.; Sheffield Academic Press: Sheffield, U.K.,2001; pp 107-163.

(15) Fuls, J.; Hawkins, C. S.; Hugo, F. J. C. J. Agric. Eng. Res. 1984,30, 29-35.

(16) Kaufman, K. R.; Ziejewski, M. Trans. ASAE 1984, 27, 1626-1633.

(17) Harrington, K. J.; D’Arcy-Evans, C. J. Am. Oil Chem. Soc. 1985,62, 1009-1013.

Scheme 1. Transesterification Process Table 1. Chemical and Physical Properties of BrassicaOils

high-erucicBrassica carinata

oilb

Brassica carinataoil withouterucic acidb

fatty acids (%)a

palmitic C16:0(t ≈ 4.118 min)

5.3 ( 0.1 5.4 ( 0.1

palmitoleic C16:1(t ≈ 4.545 min)

stearic C18:0(t ≈ 5.53 min)

0.20 ( 0.01

oleic C18:1(t ≈ 6.167 min)

10.0 ( 0.2 43.2 ( 0.9

linoleic C18:2(t ≈ 7.275 min)

24.6 ( 0.5 36.0 ( 0.7

linolenic C18:3(t ≈ 8.8 min)

16.5 ( 0.3 15.2 ( 0.3

erucic C22:1(t ≈ 13.86 min)

43.6 ( 0.8

Other Propertiesb

free fatty acid (%) 10.81 ( 0.31 2.2 ( 0.2peroxide value (meq) 8.9 ( 0.1 22.5 ( 0.4density (kg/m3) 914 ( 1 921 ( 1kinematic viscosity at

40 °C (mm2/s)118.8 ( 0.9 68.1 ( 0.8

kinematic viscosity at20 °C (mm2/s)

48.6 ( 0.9 32.1 ( 0.6

water content (%) 0.25 ( 0.02 0.20 ( 0.01a Other fatty acids (myristic, margaric, margaroleic, arachidic,

gadoleic, and behenic) were present in amounts of <1%. b Mediumvalue ( standard deviation (n ) 3).

78 Energy & Fuels, Vol. 18, No. 1, 2004 Dorado et al.

conducted in a stirred tank reactor that was equippedwith a temperature controller and a reflux condenser,to avoid methanol losses.

Materials and Methods

1. Characterization of the Oil. High-erucic and low-erucicBrassica carinata oilseeds were collected and processed bymechanical cold-press extraction. At this point, the crude oilwas not refined any further. The fatty acid composition ofthe oil was analyzed using gas chromatography (GC)(Hewlett-Packard, model 5890 GLC). The chromatograph wasequipped with a flame ionization detector (FID) and a 30 m ×0.25 mm Supelcolwax-10 glass column that was packedwith poly(ethylene glycol) (film thickness of 0.25 µm). Nitrogenwas used as a carrier gas at a flow rate of 1 mL/min. Theinjector and detector temperatures were maintained at 250°C. The column temperature was increased from 165 °C (2 min)to 180 °C at a rate of 4 °C/min (3 min), then to 200 °C at arate of 5 °C/min, and finally to 260 °C at a rate of 15 °C/min;this last temperature was maintained for 2 min. ChemStationsoftware (HP-3365) was used for data acquisition.18 Thechemical and physical properties of Brassica oils are given inTable 1.

2. Transesterification Process. The reaction vessel wascharged with a given amount of Brassica carinata oil (100 g),which was stirred at 1100 rpm and preheated at differenttemperatures. Meanwhile, the solution of methanol (CH3OH)and KOH was added. The mixture was stirred and heated.The time of reaction was varied, to obtain a large range ofmethyl ester yields. Heating and stirring were then stopped,and the product was allowed to settle, to allow the two phasesto be separated. The top phase consisted of biofuel, whereasthe lower phase contained a mixture of impurities. The upperlayer was purified using distilled water and then dried overanhydrous sodium sulfate (Na2SO4) (see Scheme 2). In thissense, 0.5 g of anhydrous Na2SO4 were added for every 100mL of ester, stirred for 15 min, and then was allowed to settleand be decanted. To remove solid traces from biofuel after thepurification step, a filtration process was needed. This stepwas performed with the help of a vacuum pump and a 27-µm-

diameter filter paper (No. 1305, from ALBET (Filtros AnoiaSA, Barcelona, Spain)). For each oil sample, three replicationswere performed.

The optimum of each parameter involved in the process wasdetermined while the rest of them remained constant. Aftereach optimum was attained, this value was accepted andconsidered to be constant during the optimization of the nextparameter. Ester yield results (given as percentages) wererelated to the weight of oil at the start (weight of ester/weightof oil).

Finally, biodiesel fuel properties were determined with thehelp of the standard tests and compared to those of diesel fuel,according to the EN-590 standard and European Standard EN14214 for biodiesel.

Results and Discussion

1. Oil Properties. According to Table 1, the free fattyacid (FFA) content was in the range of 2.2% (forBrassica carinata oil without erucic acid) to 10.8% (forhigh-erucic Brassica carinata oil). High-erucic Brassicacarinata oil showed a significantly high FFA value,compared to samples without erucic acid, probablybecause of the presence of the erucic acid. These FFAcontents should make transesterification of the oilspossible; FFA contents of >3% decrease the conversionefficiency considerably.13 However, Dorado et al.19 foundthat transesterification would not occur if oils with anFFA content of >3% were used. In this work, it was notpossible to perform transesterification of high-erucicBrassica carinata oil; it led to soap formation. It seemsthat the presence of erucic acid was responsible for theobserved high FFA content, and we feel confident thatit was the main obstacle to accomplishing transesteri-fication of the high-erucic Brassica carinata oil. On theother hand, it can be noticed that the absence of erucicacid in the nonerucic Brassica carinata oil has led toan increase in the presence of oleic and linoleic acids(see Table 1).

(18) Ballesteros, E.; Cardenas, S.; Gallego, M.; Valcarcel, M. Anal.Chem. 1994, 6, 628-634.

(19) Dorado, M. P.; Ballesteros, E. A.; de Almeida, J. A.; Schellert,C.; Lohrlein, H. P.; Krause, R. Trans. ASAE 2002, 45, 525-529.

Scheme 2. Process to Obtain Biofuel

Transesterification of Brassica Carinata Oil Energy & Fuels, Vol. 18, No. 1, 2004 79

The peroxide value (PV) indicates oil autoxidation,which is a property that could lead to catalyst inactivityduring the transesterification process. According toTable 1, the PV ranged from 8.9 meq/kg for high-eruricBrassica carinata oil to 22.5 meq/kg for nonerucicBrassica carinata oil. However, Anggraini13 found that,for transesterification purposes, values up to 30-35meq/kg could be tolerated. In the present work, thekinematic viscosity was significantly higher for high-erucic Brassica carinata oil than that for nonerucicBrassica carinata oil. Nevertheless, in both cases, thekinematic viscosity value was too high to allow the useof straight Brassica carinata oils as fuels. On the otherhand, the water content was very similar in both cases(<1%), which prevents saponification or the hydrolysisof glycerides and makes transesterification possible.13

In this field trial study, only Brassica carinata oilwithout erucic acid was successfully transesterified,thus indicating that the FFA content was the moreoffensive parameter.

2. Catalyst Optimization. To avoid corrosion prob-lems in engine components that are due to the presenceof acid traces, basic catalysts instead of acid catalystswere selected.20 In this sense, two basic catalystssKOHand NaOHswere tested under the same conditions(1.26% catalyst and an excess of alcohol, tested at roomtemperature). However, no ester formation was ob-served using NaOH, unless the reaction time wasconsiderably increased (up to 14 h), compared to KOH(up to 1 h). For this reason, KOH was selected. Theeffect of KOH concentration was studied in the rangeof 0%-2.3% (weight of KOH/weight of oil). Results usingKOH (alcohol over the stoichiometric amount) areshown in Figure 1.

Only nonerucic Brassica carinata oil was successfullytransesterified. As shown in Figure 1, the maximumyield of ester was obtained by adding 0.8% of KOH.However, the ester was opaque, which indicated thepresence of unreacted glycerides.21 The optimum was

achieved using 1.4% of KOH, which produced a 91.9%yield of reddish, crystalline, and transparent ester. Thisamount was greater than the amounts of catalyst usedby other researchers.10,22 Ester formation started after20-40 s of stirring. KOH amounts greater than 1.4%produced a smaller ester yield, because of the presenceof soaps, which prevents ester layer separation, as foundby Coteron et al.12

3. Alcohol Optimization. Preliminary tests wereconducted using both methanol (50% v/v) and ethanol(50% v/v). Under the same conditions (1.4% catalyst,room temperature), it was not possible to achieve esterformation using ethanol (even using an anhydrousalcohol, which led to the formation of soap and gelati-nous layers. Instead, using methanol, both the ester andglycerol layers were easily separated. Anyway, trans-esterification using ethanol occurred slower than thatusing methanol, as reported by Du Plessis et al.23 Inthe present work, methanol was the alcohol selected.The effect of methanol presence was studied in therange of 0%-20% (weight of methanol/weight of oil).Results using methanol are shown in Figure 2.

The methanol:triglyceride molar ratio that is requiredby the stoichiometry should be 3:1. However, as shownin Figure 2, the maximum yield of ester was obtainedby adding 16% methanol (weight of methanol/weight ofoil), which is equivalent to a molar ratio of 1:4.6 (oil:methanol). In contrast, other researchers have found itnecessary to increase the molar ratio up to 1:6, or evento 1:12, to achieve the maximum yield of monoesterproduct from safflower oil or soybean oil.9,21 Our findingsare probably due to the greater amount of catalyst usedin the present work, compared to that in the work ofother researchers.9,21 Ester formation started after 30s of stirring. In this work, methanol amounts of >20%

(20) Ballesteros, E.; Gallego, M.; Valcarcel, M. Anal. Chim. Acta1993, 282, 581-588.

(21) De Filippis, P.; Giavarini, C.; Scarsella, M.; Sorrentino, M. J.Am. Oil Chem. Soc. 1995, 72, 1399-1404.

(22) Trent, W. R. Process of Treating Fatty Glycerides. U.S. Patent462,370, 1945.

(23) Du Plessis, L. M.; de Villiers, J. B. M.; Hawkins, C. S. Methodsof Preparing and Purifying Methyl and Ethyl Fatty Acid Esters fromSunflowerseed Oil; SAE: Pretoria, Republic of South Africa, 1983; p9.

Figure 1. Percentage yield of ester relative to oil at start (w/w%), using different amounts of KOH and alcohol over thestoichiometric amount.

Figure 2. Percentage yield of ester relative to oil at start (w/w%), using different amounts of methanol and 1.4% KOH.

80 Energy & Fuels, Vol. 18, No. 1, 2004 Dorado et al.

made glycerol separation difficult, thus decreasing esteryield formation, which was opaque. In this case, esterformation started after 80 s of stirring. The addition of<5% methanol resulted in the creation of a unique andfoamy layer. Methanol amounts up to 10% produced twolayers, although the lower layer was gelatinous and theupper layer was opaque, because of the presence ofunreacted triglycerides, thus indicating that methanolwas insufficient to perform a complete reaction.

4. Reaction Temperature Optimization. The maxi-mum yield of ester was obtained at room temperature.Results revealed that the ester yield slightly decreaseswhen other reaction temperatures are used, especiallywhen the temperature is >50 °C. However, otherresearchers achieved better results using temperaturesabove 50 °C, up to 70-80 °C.9,23 In fact, severalresearchers found that the temperature increase influ-ences the reaction in a positive manner.24

Although a reflux condenser was used to avoid meth-anol losses, the ester yield significantly decreased attemperatures of >50 °C, probably because of a negativeinteraction between temperature and catalyst concen-tration, due to side reactions, such as soap formation.12

Also, Trent22 found that reaction temperatures of >60°C should be avoided, because they tend to acceleratethe saponification of the glycerides by the alkalinecatalyst before completion of the alcoholysis. Becauseof this observation, as well as economic reasons, roomtemperature was selected during transesterification.

5. Reaction Time and Stirring Time Optimiza-tion. To achieve perfect contact between the reagentsand the oil during transesterification, they were mixedtogether.21 The ester yield slightly increased as thereaction time increased. Results revealed that, after 1min of stirring, a suitable phase separation was achieved.The maximum yield of ester was reached after 30 minof stirring, whereas other researchers required up to4 h.23

6. Settling Time Optimization. After the transes-terification was finished, the reaction products wereplaced in a closed vessel, to be decanted. A successfulreaction produces two liquid phases: ester (upper layer)and glycerol (lower layer). When room temperature was>38 °C, which is the usual temperature in most placesin Andalusia (Spain) during the summer, separationbetween the phases occurred within 1-3 h. However,when room temperature decreased to 10-15 °C, severaldays were required for complete settling to occur. Toincrease the pouring-off rate, a temperature increasewas requested, i.e., with the help of a double boiler at40 °C. In this case, complete settling could be reachedin <3 h, probably because of the positive influence ofthe settling temperature. In fact, it was noticed that,after a few days of settling, the opaque ester samplesturned crystalline, and a slight glycerol lower phaseappeared. This could be explained by a certain conflictbetween glycerol solubility and low temperatures. Inconclusion, this problem could be resolved by increasingthe settling temperature or settling time.

7. Purification Step Optimization. It is importantto remove impurities that are present in the ester layer,i.e., soaps, KOH traces, methanol traces, and free

glycerol. Otherwise, a high content of free glycerol canresult in separation of the glycerol, causing problemsduring storage, in the fuel system or produce higheraldehyde emissions.25 In the present work, washing withdistilled water, gentle stirring for 4 min, and settlingin a vessel (to allow decanting) was applied to removemineral contaminants in the ester. After this step, twolayers were formed. The upper layer was made ofbiofuel, and the lower layer was made of water andimpurities. This process was repeated until the lowerphase had a pH value that was similar to that ofdistilled water, thus indicating that only water waspresent and that the impurities were removed in theformer washing. Preliminary tests were conducted byadding 2, 4, or 15 mL of distilled water to the ester (2.27,4.55, or 17.01 wt % of ester, respectively) and allowingthe mixture to settle in a vessel, to be poured off. Afterthe settling was completed, the ester layer appearedopaque, and a second washing process was performedto achieve a more suitable and crystalline sample ofester (Figure 3). However, by adding 10 mL (11.36%)or 15 mL (17.01%) of distilled water, no more washeswere needed. For economic reasons, washing one timeusing 11.36% of distilled water at 25 °C was consideredto be the best choice. Also, washing more than one timeabove room temperature is not economically sound,because of the additional cost, although other research-ers found it necessary to wash several times or use washwater at temperatures up to 90 °C.23,24,26,27 In Figure 3,on the x-axis, the first addend of each sum indicates thepercentage of distilled water used during the first stepof the washing process. The second addend indicates thepercentage of distilled water used during the second stepof the washing process, which is needed to achieve apH value of the lower layer that is similar to thepH value of the distilled water, thus indicating thatno impurities were present in the ester layer afterthe previous washing step. As in Du Plessis et al.,23

losses of esters during the washing process were<6%(2%-3%).

8. Fuel Specifications. The fuel properties of thebiodiesel from Brassica carinata oil without erucic acidwere determined with the aid of standard tests. Thebiodiesel properties were determined to be similar tothose of diesel fuel (according to standard EN-590) andwere especially similar to those of the EN 14214standard, thus indicating that methyl esters fromBrassica carinata oil without erucic acid have adequatevalues, compared to diesel fuel (Table 2). The iodinevalue does not meet the EN 14214 standard. However,this parameter (which is related to biofuel storageperformance) has not been accepted by the Spanishgovernment, because it excludes sunflower oil (whichis one of the main Spanish oleaginous crops) from beingused as biodiesel. In this sense, to determine theimplications of this parameter, research concerning theperformance of diesel engines is needed.

The cold filter plugging point (CFPP), pour point (PP),and cloud point (CP) are three important parametersthat are associated with the engine behavior in cold-weather operating conditions. However, instead of the

(24) Karaosmanoglu, F.; Akdag, A.; Cigizoglu, K. B. Appl. Biochem.,Biotechnol. 1996, 61, 251-265.

(25) Mittelbach, M. Bioresour. Technol. 1996, 56, 7-11.(26) Purcell, D. L.; McClure, B. T.; McDonald, J.; Basu, H. N. J.

Am. Oil Chem. Soc. 1996, 73, 381-388.(27) Canakci, M.; Van Gerpen, J. Trans. ASAE 1999, 42, 1203-1210.

Transesterification of Brassica Carinata Oil Energy & Fuels, Vol. 18, No. 1, 2004 81

CP and PP, the European Standard EN 14214 onlyincludes the CFPP determination. In this sense, non-erucic Brassica carinata oil methyl ester provides asuitable fuel for cold-weather use. The CP and PP valuesfor nonerucic Brassica carinata oil methyl ester are alsomore appropriate than those for cottonseed methyl ester(PP ) -4 °C), soybean methyl ester (CP ) +2 °C, PP )-1 °C), sunflower methyl ester (CP ) 0 °C, PP ) -4°C), or rapeseed methyl ester (CP ) -2 °C, with an alsoappropriate PP value of -9 °C).14

According to the Conradson carbon residue (CCR)content, which represents the carbon-forming tendencyof fuels, the biodiesel from Brassica carinata oil exhib-ited a value over the No. 2 diesel fuel specification (EN590). This could lead to the formation of deposits at the

injector and combustion problems. For this reason, along-term performance test should be performed toverify the formation of abnormal carbon deposits or anyproblems related to incomplete combustion that couldrequire a more frequent cleaning.

Finally, regarding to the low presence of free glycerol,it can be seen that the glycerol removal was successfullyperformed (see Table 2), thus indicating that thepurification step was adequate.

Conclusions

A low-cost transesterification process of Brassicacarinata oil has been described. An oil:methanol molarratio of 1:4.6, the addition of 1.4% of KOH, a reaction

Figure 3. Ester pH after washing one and two times with distilled water (percentage of ester weight).

Table 2. Fuel Specifications of Nonerucic Brassica Carinata Oil Methyl Esters, Diesel Fuel (EN-590), and BiodieselEuropean Standard (EN 14214)

Value

parameter test methodbiodiesel, EuropeanStandard EN 14214

diesel fuel,EN-590

nonerucic Brassica carinataoil methyl esters

Distillate Propertiesdistillate content at 250 °C (vol %) ASTM-D-86 <65 0distillate content at 350 °C (vol %) ASTM-D-86 >85 83.60temperature, 95 vol % (°C) ASTM-D-86 360 357.2

Other Propertiesdensity at 15 °C (kg/m3) EN ISO 3675 860-900 820-860 888.8kinematic viscosity at 40 °C (mm2/s) ASTM D445*IP-71*BS188 3.5-5.0 2-4.5 4.83iodine value UNE 55.013 <120 138flash point (°C) ASTM-D-2709 >120 >55 163cetane number, CNa ASTM-D-613 >46cetane index, CIa ASTM-D-4737/96a >51.0 56.9water content (mg/kg) ASTM-D-1744 <500 <50cold filter plugging point, CFPP (°C) IP-309/96 depends on the climate -9cloud point, CP (°C) ASTM-D-2500 -9pour point, PP (°C) ASTM-D-97 -6Conradson carbon residue (wt %) ASTM-D-4530 0.15 1.73copper corrosion (3 h, 50 °C), degrees ASTM-D-130 Class 1 1 1agross heating value (MJ/kg) ISO 1928 39.55acid value (mg KOH/g) EN 12634 <0.5 0.1free glycerol (wt %) NF-T-60-704 0.0008 <0.02

a The equations for predicting the cetane number (CN) are not applicable to biodiesel. As an alternative method, the cetane index (CI)is used for biodiesel.

82 Energy & Fuels, Vol. 18, No. 1, 2004 Dorado et al.

temperature in the range of 20-45 °C, and 30 min ofstirring are considered to be the best conditions todevelop a low-cost method to produce biodiesel fromBrassica carinata oil. The impurities, including glyceroltraces, are removed after the biofuel is washed with11.36% of distilled water at 25 °C. Results show thatthe presence of erucic acid increases the free fatty acid(FFA) content and prevents the conversion of Brassicacarinata oil in its methyl ester. Also, our results suggestthat there is a correlation between the amount ofmethanol required to perform the transesterification ofthe oil and the amount of KOH. In this sense, thegreater the presence of KOH, the lesser the methanolrequirements. However, this is valid only under certainlimits. In fact, if the presence of KOH or methanol isless than the optimal values, the reaction does not fullyoccur. Similarly, amounts of KOH or methanol that are

greater than the optimal values lead to soap production,which prevents separation of the ester layer. Also, acertain conflict between glycerol solubility and lowtemperatures was observed. This is an important factorto consider while promoting the separation of biodieseland glycerol. Finally, based on this field trial, biodieselfrom Brassica carinata oil could be recommended as adiesel fuel candidate, if long-term engine performancetests provide satisfactory results.

Acknowledgment. The authors thank KOIPESOL(Spain), which provided Brassica carinata oil sam-ples for testing, and REPSOL-YPF, which performedanalytical analysis to determine the biofuel specifica-tions.

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