Energy Conversion and Management 81 (2014) 30–40

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Energy Conversion and Management

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Optimization of biodiesel production and engine performance from highfree fatty acid Calophyllum inophyllum oil in CI diesel engine

http://dx.doi.org/10.1016/j.enconman.2014.01.0650196-8904/� 2014 Elsevier Ltd. All rights reserved.

Abbreviations: ASTM, American society for testing and materials; Bsfc, brakespecific fuel consumption; BTE, brake thermal efficiency; CCIO, crude Calophylluminophyllum oil; CI, compression ignition; CIB, Calophyllum inophyllum biodieselblends; CIB10, Calophyllum inophyllum blending 10%; CIB20, Calophyllum inophyllumblending 20%; CIB30, Calophyllum inophyllum blending 30%; CIB50, Calophylluminophyllum blending 50%; CIME, Calophyllum inophyllum methyl ester; CO, carbonmonoxide; DOE, design of experiment; EN, European standard; EGT, exhaust gastemperature; FFA, free fatty acid; FAME, fatty acid methyl ester; H2SO4, sulfuricacid; H3PO4, phosphoric acid; HSU, Hartridge smoke units; NaOH, sodium hydrox-ide; NaHCO3, sodium bicarbonate; NOx, nitrogen oxide; ppm, parts per million.⇑ Corresponding author. Tel.: +60 16 590 3110; fax: +60 3 7967 5317.

E-mail addresses: ong1983@yahoo.com, onghc@um.edu.my (H.C. Ong).

Hwai Chyuan Ong a,⇑, H.H. Masjuki a, T.M.I. Mahlia b, A.S. Silitonga a, W.T. Chong a, K.Y. Leong c

a Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysiab Department of Mechanical Engineering, Faculty of Engineering, Universiti Tenaga Nasional, 43000 Kajang, Selangor, Malaysiac Department of Mechanical Engineering, Universiti Pertahanan Nasional Malaysia, Kem Sungai Besi, 57000 Kuala Lumpur, Malaysia

a r t i c l e i n f o

Article history:Received 26 October 2013Accepted 29 January 2014

Keywords:BiodieselCrude Calophyllum inophyllum oilAlternative fuelEngine performanceEmission characteristicRenewable energy

a b s t r a c t

In the present study, crude Calophyllum inophyllum oil (CCIO) has been evaluated as a potential feedstockfor biodiesel production. C. inophyllum oil has high acid value which is 59.30 mg KOH/g. Therefore, thedegumming, esterification, neutralization and transesterification process are carried out to reduce theacid value to 0.34 mg KOH/g. The optimum yield was obtained at 9:1 methanol to oil ratio with1 wt.%. NaOH catalyst at 50 �C for 2 h. On the other hand, the C. inophyllum biodiesel properties fulfilledthe specification of ASTM D6751 and EN 14214 biodiesel standards. After that, the C. inophyllum biodieseldiesel blends were tested to evaluate the engine performance and emission characteristic. The perfor-mance and emission of 10% C. inophyllum biodiesel blends (CIB10) give a satisfactory result in dieselengines as the brake thermal increase 2.30% and fuel consumption decrease 3.06% compared to diesel.Besides, CIB10 reduces CO and smoke opacity compared to diesel. In short, C. inophyllum biodiesel canbecome an alternative fuel in the future.

� 2014 Elsevier Ltd. All rights reserved.

1. Introduction

The fossil fuel resources are dwindling day by day. Biodiesel isone of the possible solutions to overcome oil shortage and environ-mental issue [1]. Biodiesel have low volatility due to high molecu-lar weight of the triglyceride molecule and have a narrow range ofviscosity changes with temperature [2]. Biodiesel is a clean burningalternative fuel was produced from renewable resources like virginor used vegetable oils, both edible and non-edible [3,4]. Biodiesel isobtained from the chemical transformation of oils (triglycerides)by a transesterification process and many oleaginous vegetablespecies [5]. However, biodiesel produced from edible oils raised

the concerns of feedstock competing with food supply in thelong-term [6]. Therefore, non-edible oils resources are gainingworldwide attention as it is easily available in many parts of theworld especially wastelands that are not suitable for food crops[7]. Besides, the use of biodiesel in diesel engines results in sub-stantial reduction of harmful emission such as unburned hydrocar-bons, carbon monoxide and particulate matters [8,9].

There are many ways and procedures to biodiesel fuel fromvegetable oil such as pyrolysis, dilution, microemulsion and transe-sterification [10]. The transesterification process is the most viableand economical process [11]. Transesterification process is using analcohol (methanol, ethanol or propanol) with the presence of alkalicatalyst (sodium hydroxide or potassium hydroxide) to break themolecule of the vegetable oil into methyl or ethyl esters chemicallywith glycerol as a byproduct [12]. Biodiesel produced via transesteri-fication process has proven to be a viable alternative fuel with similarcharacteristics to diesel fuel [13]. Besides, some researchers are usingtwo-step esterification and transesterification processes in produc-ing biodiesel from crude oils with high free fatty acid (FFA) [14]. Dharet al. [15] reported that high FFA of neem oil (20.3%) was converted tomethyl ester using two-step esterification and transesterificationprocess. As a result, the important properties of the biodiesel werewithin the ASTM biodiesel specification. Jena et al. [16] investigatedthat acid pretreatment and base transesterification reaction process

H.C. Ong et al. / Energy Conversion and Management 81 (2014) 30–40 31

is suitable for biodiesel production from mixture of mahua and sim-arouba oils with high FFA. The yield of biodiesel and ester conver-sion was around 98% and 90% respectively.

In this study, non-edible ‘‘Calophyllum inophyllum’’ oil was investi-gated as a potential feedstock for biodiesel production. C. inophyllumis a multipurpose tree belonging to the family Clusiaceae,commonly known as mangosteen family [17]. This plant has multi-ple origins including East Africa, India, South East Asia, Australia,and the South Pacific [18]. Fig. 1 shows the distribution map ofC. inophyllum around the world. It grows in areas with an annualrain of 1000–5000 mm at altitudes from 0 to 200 m. C. inophyllumis a low-branching and slow-growing tree which grows best in san-dy and well drained soils. Its sizes typically ranges between 8 and20 m (25–65 ft) tall at maturity, sometimes reaching up to 35 m(115 ft) [19]. In each fruit, it consists one large brown seed with2–4 cm (0.8–1.6 in.) in diameter [20]. C. inophyllum tree can beplanted at a density of 400 tree/ha with an average oil yield of11.7 kg/tree or 4680 kg/ha [11]. Traditionally, its oil has been usedas a medicine, soap, lamp oil, hair grease and cosmetic in differentparts of the world [21]. Fig. 2 shows C. inophyllum tree, fruit, seedsand kernels.

The objective of this study is to produce biodiesel from crude C. ino-phyllum oil using H2SO4 as acid catalyst and NaOH as alkaline catalyst.After that, the optimization of C. inophyllum methyl ester productionwas studied and its properties as biofuel were analyzed based on ASTMD6751 and EN 14214 biodiesel standards. On top of that, a C. inophyl-lum biodiesel diesel blend properties were tested and the performanceand emission characteristic were conducted in a direct injection dieselengine. It is notable that this study suggests a novel alternative biodie-sel feedstock as energy source in compression ignition engine.

2. Methodology

2.1. Extraction of C. inophyllum seed oil

C. inophyllum seeds were collected from Kebumen, Center Java,Indonesia. After that, the seeds were dried under sunlight until the

Fig. 1. Distribution of Calophyllum in

color of the seeds turn into red-brown. The ideal conditions to pre-serve the kernel are 26–27 �C and 60–70% humidity. Hydraulic ma-chine is used to extract the oil from C. inophyllum kernel seed. Theremaining seed cake after extraction has high commercial valueand can be used either for agricultural or industrial applications.The C. inophyllum oil extracted was found to contain many impuri-ties and chemical compound. Therefore, it is important to undergoa degumming process before converting crude C. inophyllum oil tobiodiesel. The flow chart shown in Fig. 3 is the methodology ap-plied for C. inophyllum biodiesel production process.

2.2. Degumming process

Gum contains phosphate, protein, carbohydrate, water residueand resin. In order to improve the oxidization stability of the finalproduct, the oil is separated from the gums through the degum-ming process. In this process, the crude oil was heated at a temper-ature of 60 �C and stirring speed of 1000 rpm. Then, 0.5 vol.% ofphosphoric acid (H3PO4, 20% concentration) was added to the pre-heated crude oil. The process was continued with stirring and thetemperature maintained at 60 �C for 30 min. After that, this mix-ture was separated by density separation process using a separat-ing funnel for at least 4 h in which the phosphate compoundsresided at the bottom. These gums were separated from the oiland washed several times with distilled water at 40 �C. After wash-ing, water was evaporated with vacuum pump for 30 min to avoidthe oxidization of oil.

2.3. Esterification process

The degummed C. inophyllum oil has high content of FFA andviscosity. The maximum limit of FFA amount is 2 wt.%. and below.Therefore, a pretreatment process using acid catalyzed esterifica-tion is required for the crude oil with high FFA content beforethe transesterification process. Thus, sulfuric acid (H2SO4) is usedto convert and reduce the FFA content to below 2 wt.%. in the oil.Therefore, two step processes of acid catalyzed esterification

ophyllum tree around the world.

Fig. 2. Calophyllum inophyllum tree, fruit, seeds and kernels.

Fig. 3. Flow chart methodology of Calophyllum inophyllum biodiesel production process.

32 H.C. Ong et al. / Energy Conversion and Management 81 (2014) 30–40

process and base catalyzed transesterification process are used toproduce the biodiesel from C. inophyllum oil with high FFA. Ontop of that, crude C. inophyllum oil was transferred into a preheatedreactor at a temperature of 60 �C. The methanol (9:1 methanol tooil ratio) and H2SO4 catalyst (1 vol.%) were measured and mixedtogether before added into the reactor. The mixture was stirred

constantly using an overhead stirrer with a constant speed of1150 rpm for 3 h. Throughout this process, the temperature waskept constant at 60 �C. After esterification process, the sample oilwas transferred into a separation funnel for 4 h to remove thewater and extra methanol. The upper layer is esterified oil whilethe water and extra methanol were at the lower layer. After that,

H.C. Ong et al. / Energy Conversion and Management 81 (2014) 30–40 33

the esterified oil was washed by using distilled water at 40 �C. Fi-nally, the esterified oil was evaporated with a rotary evaporatorat 65 �C for 30 min to remove residual methanol and water.

2.4. Neutralization

Neutralization process is to purify the gum and organic particlespresent in the esterified oils. It is observed that after esterificationprocess, acid value of the oil is still high which is about 5–10 mgKOH/g. Thus, neutralization is carried out to reduce the FFA con-tent. In the course of preliminary tests, the esterified oil waspoured into double jacketed equipped with a motor stirrer, refluxcondenser and thermometer respectively. Then, 0.23 wt.%. sodiumbicarbonate (NaHCO3) is diluted to 50 ml methanol while stirringand added to the esterified oil. In this process, the reaction wasmaintained at 50 �C for 30 min. The esterified oil was removedfrom the reactor and entered into a separation funnel and left for30 min to remove extra methanol at lower layer.

2.5. Transesterification

After esterification process, the FFA content is reduced below2%. Then, the esterified C. inophyllum oil was measured and placedinto a jacketed reactor. The esterified C. inophyllum oil was pre-heated to the temperature of 50 �C by using a heating circulator.Then 1 wt.%. of alkali catalyst (NaOH) and 9:1 of methanol to oil ra-tio are mixed until all the NaOH has been dissolved. After that, theprepared mixtures of methanol and NaOH were added into the pre-heated crude oil. The mixture was stirred constantly at 1150 rpmby an overhead stirrer during the transesterification process for2 h. In this process, the temperature was maintained at 50 �C.

2.6. Purification and drying

After phase separation of FAME and glycerin, the FAME waspurified and washed gently with distilled water at 40 �C in orderto remove impurities. The mixture was allowed to settle undergravity for 2–3 h in a separating funnel. The lower layer consistsof impurities were drained out. Finally, the product was evapo-rated with rotary evaporator at 65 �C for 30 min to remove residualmethanol and water.

2.7. Optimization of biodiesel production

The design of experiment (DOE) is used to determine the opti-mization condition of transesterification process. This methodwas conducted to determine the optimum condition for methanolto oil molar ratio, catalyst concentration, reaction temperature andtime as well as agitation intensity speed.

2.8. Biodiesel diesel blends

In this study, C. inophyllum biodiesel was blended with diesel atfour different ratios which are 10%, 20%, 30% and 50% of biodieselat volume basic. The biodiesel blends are used to examine the ef-fect of blending on physicochemical properties and further studyin engine performance and emission characteristic.

2.9. Experimental setup and procedure for engine test

The engine speed varies from 1500 to 2400 rpm with 100 rpminterval range. A SAJ SE-20 Eddy current dynamometer and Auto-ETS 1 controller system was used to determine the engine perfor-mance and speed. The experimental setup and specifications of theengine, dynamometer and gas analyzer used were shown in Fig. 4and Table 1. A BOSCH BEA 150 gas analyzer is used to analyze the

exhaust emissions from the engine such as carbon monoxide (CO),oxides of nitrogen (NOx) and smoke opacity. Each experiment wasrepeated for three times and the mean value was calculated foreach sample. The errors and uncertainties of instruments and oper-ating condition are listed in Table 2. The experiment was con-ducted in Heat Engine Laboratory, Department of MechanicalEngineering, Faculty of Engineering, University of Malaya.

3. Results and discussion

3.1. Properties of crude C. inophyllum oil and biodiesel

The crude C. inophyllum oil is dark green color. In this study, thefatty acid composition of crude C. inophyllum oil and physicochem-ical properties are analyzed and shown in Table 3. The crudeC. inophyllum oil contains higher amount of unsaturated fatty acids(oleic and linoleic) than saturated fatty acids (palmitic and stearic).The comparison of fatty acid composition crude C. inophyllum oilwith other non-edible feedstock is shown in Fig. 5. Crudece:italic>C. inophyllum oil contains gum such as phosphate, protein,carbohydrate, water residue and resin. Therefore, degumming pro-cess is required to separate oil from the gums in order to improvethe oxidization stability of the oil. It is shown that density, viscos-ity, acid value and FFA value decreased after degumming process.Apart from that, transmission has increased and absorbance hasdecreased which attributed to the removal of gum from the oil.

Table 4 shows the physiochemical properties results of pro-duced C. inophyllum methyl ester (CIME) and compared with ASTMD6751 and EN 14214 biodiesel standards. All specified propertiesfrom CIME are in acceptable ranges according to ASTM D6571and EN 14214 standards. The kinematic viscosity of CIME is3.45 mm2/s which was lower than Polanga biodiesel of3.99 mm2/s reported by Sahoo et al. [22]. The density of CIME ob-tained was 877.6 kg/m3. The density of fuel affects the exhaustemissions in which high density fuel will cause an increase in par-ticular matter and NOx emission [23]. Generally, biodiesel fuel hasslightly higher density than diesel fuel. The obtained calorific valuefor CIME was 41.442 MJ/kg and this value is slightly higher thanpolanga biodiesel which is recorded to be 41.397 MJ/kg [22]. Thecold filter plugging point, cloud point and pour point for CIMEare 0.0 �C, 2.0 �C and 2.0 �C respectively. It is observed that the coldfilter plugging point, cloud point and pour point of CIME satisfiesthe biodiesel standards. Apart from that, the physicochemicalproperties of CIME blends with diesel fuel are summarized in Ta-ble 5. The kinematic viscosity of C. inophyllum blends (CIB) in-creases with the rising of biodiesel blending ratio. The blendingratio values are 2.93 mm2/s (CIB10), 3.22 mm2/s (CIB20),3.29 mm2/s (CIB30) and 3.35 mm2/s (CIB50) which satisfies thebiodiesel diesel blends (ASTM D7467) standards. The calorific va-lue of CIB ranges from 40.172 MJ/kg to 42.542 MJ/kg. This was alsoreported in Sahoo and Das [14] which the viscosity and calorific va-lue of polanga blends (PB50, PB60 and PB80) were within the rangeof 3.42–3.72 mm2/s and 41.397–42.542 MJ/kg respectively. Be-sides, flash points measured met the safety requirements for fuelhandling and storage. The observed flash point for CIB10, CIB20,CIB30 and CIB50 were 77.5 �C, 79.5 �C, 82.5 �C and 83.5 �C respec-tively. Generally, the flash point of biodiesel diesel blends is higherthan the diesel which is safe for transport and storage purpose.

3.2. Effect of biodiesel properties on combustion characteristics

Typically, non-edible oil has high percentage of double carbonchain and has a greater degree of unsaturated fatty acid than satu-rated fatty acid [24]. As a result, this structural fatty acid composi-tion will influence the physicochemical properties of biodiesel

Fig. 4. Schematic diagram of experimental setup.

Table 1Technical specification of the test engine, dynamometer and gas analyzer device.

Technical specification of diesel engineType TF 120 M YanmarInjection system Direct injectionCylinder number 1Cylinder bore � stroke volume 92 mm � 96 mmDisplacement 0.638 lCompression ratio 17.7:1Maximum power 7.7 kWMaximum engine speed 2400 rpmCooling system Water coolingInjection timing 17.0 bTDCInjection pressure 200 kg/cm2

Technical specification of dynamometerMaximum power 20 kWMaximum speed 10,000 rpmMaximum torque 80 N mWater consumption for maximum

power14 l/min

Water pressure 23 lbf/in2

Electricity requirement 220 V, 60 Hz, 0.5 A

Technical specification of the dynamometer control unitModel Auto-ETS1 OM12CAccuracy 0.1%Precision 0.005% ± 1 digitWeight measurement Linear (load cell)Speed measurement SensorScreen type 7 Segment 5 LED Character height

10 mm VDCPower ±10% @ 50 mA max.Operation temperature 0–70 �COperation voltage 230 VAC ± 10% 50–60 HzOutput PC interface with Dyno2000x software

Measurement rangesExhaust component Measurement range Resolution

CO 0.000–10.00 vol.% 0.001 vol.%NO 0–5000 ppm vol. 61 ppm vol.

Smoke opacity meter moduleMeasured quantity Measurement range ResolutionDegree of opacity 0–100% 0.1%

Oil temperatureMeasured quantity Measurement range ResolutionTemperature �20 to +150 �C 0.16 �C

Table 2List of measurement uncertainty.

Measurement Accuracy Uncertainty (%)

Torque ±0.1 N m ±0.33%Speed ±1 rpm ±0.05%EGT indicator ±1 �C ±0.20%NO ±1 ppm vol. ±0.63 ppm vol.CO ±0.001 vol.% ±0.54 vol.%Smoke ±0.1% ±3.65%

Table 3FAC and physicochemical properties of crude Calophyllum inophyllum oil.

Fatty acid Formula Structure wt.%

Lauric acid C12H24O2 C12:0 0.1Myristic acid C14H28O2 C14:0 0.1Palmitic acid C16H32O2 C16:0 14.2Sapienic acid C16H30O2 C16:1 0.3Stearic acid C18H36O2 C18:0 15.9Oleic acid C18H34O2 C18:1 39.8Linoleic acid C18H32O2 C18:2 28.1Linolenic acid C18H30O2 C18:3 0.2Arachidic acid C20H40O2 C20:0 0.8Saturated acids 31.1Unsaturated acids 68.5

Property Calophyllum inophyllum

Before degumming After degumming

Viscosity at 40 �C (mm2/s) 53.17 43.96Density at 15 �C (kg/m3) 951.0 949.0FFA (%) 29.65 21.47Acid value (mg KOH/g) 59.30 42.94Flash point (�C) 195.5 188.5pH at 26 �C 3.93 4.27Refractive index 1.479 1.4639Transmission (%T) 35.2 82.6Absorbance (abs) 0.582 0.099Colour Dark green Reddish yellow

Note: Carbon number with ‘zero’ double bonds are saturated fatty acids, with ‘one’double bonds are monosaturated and with ‘two’ and ‘three’ double bonds arepolyunsaturated fatty acids.

34 H.C. Ong et al. / Energy Conversion and Management 81 (2014) 30–40

such as viscosity, density and calorific value [23,25]. Kinematic vis-cosity will affect the operation of fuel injection of engine particu-larly at low temperatures when viscosity increases and affects

the fluidity of the fuel [26]. Moreover, high viscosity of biodieselwill cause the insufficient fuel atomization which lead to formationof engine deposits and soot. Besides, density also will influence theefficiency of the fuel atomization for combustion systems [27,28].The viscosity and density of CIME are 3.45 mm2/s and 877.6 kg/m3

Fig. 5. Comparison of FFA composition of Calophyllum inophyllum and other non-edible feedstock.

H.C. Ong et al. / Energy Conversion and Management 81 (2014) 30–40 35

and those values were close to diesel fuel (2.95 mm2/s and840.0 kg/m3) which give advantages to engine combustion andperformance. Besides, the cetane number is a measure of the igni-tion quality of diesel fuel during combustion ignition [28]. It maybe used in combustion and is possible reason to complete combus-tion [29,30]. On other hand, it provides information about the igni-tion delay time of a diesel fuel upon injection into the combustionchamber and high cetane implies short ignition delay [31]. Gener-ally, the cetane number of biodiesel is higher than diesel fuels [25].The cetane number for CIME (59.5) and CIB10 (52.6), CIB20 (53.7),CIB30 (55.5) and CIB50 (56.5) were higher than diesel fuel (49.7).Fuels with low cetane number tend to cause the knocking andincomplete combustion which shows increased gaseous and par-ticulate exhaust emissions. Moreover, combustion of fuel contain-ing sulfur causes sulfur oxides emissions. Most of the vegetable oilsand animal fat-based biodiesels have very low levels of sulfurcontent including C. inophyllum biodiesel [10,32].

Table 4Physiochemical properties of Calophyllum inophyllum methyl ester (CIME) and polanga bio

Property Units ASTM D6751 EN

Viscosity at 40 �C mm2/s 1.9–6.0 3.5Density at 15 �C kg/m3 880 86Acid value mg KOH/g Max. 0.50 MFlash point �C Min. 130 MPour point �C �15 to 16 –Cloud point �C �3 to 12 –Cold filter plugging point �C 19 MCalorific value MJ/kg – 35Oxidation stability hour Min. 3 MCetane number – Min. 47 MIodine value g I2/100 g – MCondrason carbon residue wt.% Max. 0.05 MCopper strip corrosion – Max. 3 MWater content vol.% Max. 0.05 MSulfur content wt.% Max. 0.05 MSulfated ash wt.% Max. 0.02 MFAME content wt.% – MMethanol content wt.% Max. 0.20 MTotal contamination mg/kg – MPhosphorus content ppm 10 4Group I metals (Na + K) mg/kg Max. 5 MGroup II metals (Ca + Mg) mg/kg Max. 5 MCarbon wt.% 77 –Hydrogen wt.% 12 –Oxygen wt.% 11.00 –

a mg/kg.b Sahoo et al.

3.3. Optimization of C. inophyllum biodiesel

3.3.1. Effect of methanol to oil molar ratio and temperatureIn Stoichiometry, the transesterification reaction requires 3 mol

of alcohol with a mole of triglyceride to produce 3 mol of fatty es-ters and 1 mol of glycerol [33]. However, it is necessary to use ex-cess alcohol from the reaction mixture in order to shift the reactionto the right. The surface contours of ester yield versus molar ratioand temperature are plotted in Fig. 6. The methanol to oil molar ra-tio varied within the range of 3:1–15:1 for C. inophyllum oil andtemperature was varied from 40 to 60 �C. A comparison amongthese plots shows that the maximum yield of ester is achieved at9:1 and 50 �C for methanol to oil molar ratio and temperaturerespectively. The maximum methyl ester yield was found to be98.92% and the increase in methanol ratio after 9:1 M ratio didnot affect the methyl ester yield. Besides, it is showed that temper-ature reaction above 50 �C will cause a decrease in methyl ester

diesel.

14214 CIME Polanga biodieselb Test method

–5.0 3.45 3.99 ASTM D4450–900 877.6 869 ASTM D127ax. 0.5 0.34 – ASTMD664in. 120 165.5 – ASTM D93

2.0 4.3 ASTM D25002.0 13.2 ASTM D2500

ax. +5 0.0 – ASTM D637141.442 41.397 ASTM D240

in. 6 14.27 – EN 14112in. 51 59.5 – ASTM D6890ax. 120 106.5 – EN 14111ax. 0.3 0.03 – ASTM D4530in. 1 1a – ASTM D130ax. 500a 0.015 – EN ISO 12937ax. 10a 6.23 – ASTM D6667ax. 0.02 0.001 – ASTM D874in. 96.5 98.7 – EN 14103ax. 0.20 0.01 – EN 14110ax. 24 8.5 – EN 12662

3 – EN 14107ax. 5 2 – EN 14538ax. 5 <1 –

72 – ASTM D529112.2 –11.80 –

Table 5Physiochemical properties of diesel fuel, Calophyllum inophyllum biodiesel and its blends.

Property Unit Diesel fuel Biodiesel blends Calophyllum inophyllum blending

Test method Limit (ASTM D7467) CIB10 CIB20 CIB30 CIB50

Viscosity at 40 �C mm2/s 2.95 D445 1.9–4.1 2.98 3.22 3.29 3.35Density at 15 �C, max. kg/m3 840.0 D6890 858 850.5 851.6 853.8 857.9Flash point �C 70.5 D93 52 77.5 79.5 82.5 83.5Cloud point �C �2 D2500 – �1.0 0.0 1.0 1.0Oxidation stability hours 26.5 EN14112 6 25.61 23.22 19.27 18.26Acid number mg KOH/g 0.051 D664 0.3 0.18 0.18 0.21 0.24Cetane number – 49.7 D6890 Min. 47–51 52.6 53.7 55.5 56.5Calorific value MJ/kg 45.825 EN14214 35 42.542 41.523 40.446 40.172Conradson carbon residue mass% 0.821 D524 0.35 0.030 0.025 0.016 0.010Sulfate ash content, max. mass% 0.08 D2709 0.05 <0.001 <0.001 <0.001 <0.001Sulfur, mg/kg max. mg/kg 14.9 D1298 10 3.9 3.7 3.26 2.18Water and sediment, max. % v/v 0.003 EN14078 0.05 0.0052 0.0059 0.0068 0.0085Copper strip corrosion – 1 EN2160 Class 1 1a 1a 1a 1a

36 H.C. Ong et al. / Energy Conversion and Management 81 (2014) 30–40

yield as well as increasing molar ratio to 12:1. This is becauseexcessive methanol and high temperature is not favorable for thepurification as synthesized biodiesel. Moreover, much energy andcost were needed to recover the large amount of unreacted meth-anol during separation process. Ma and Hanna [3] evaluated thathigher temperature and time will burn alcohol and cause a reduc-tion in methyl ester yield.

3.3.2. Effect of catalyst concentration and methanol to oil molar ratioAlkali alkoxides are most effective catalyst in transesterification

process compared to acidic catalyst. Transmethylation occurs inthe presence of both alkaline and acidic catalysts [34]. Being lesscorrosive to industrial equipment, alkaline catalyst is preferred inindustrial processes. Fig. 7 shows the yield of biodiesel versusNaOH concentration at different methanol to oil molar ratio. Thealkali catalyst concentration in the range of 0.5–1 wt.% and molarratio 3:1–15:1 has ester yield of 94–99%. In this study, the opti-mum process was found at 9:1 M ratio with 1 wt.%. of NaOH cata-lyst concentration and produced 98.01% of methyl ester yield.However, the conversion methyl ester reached 89.33% with 0.5–0.75 wt.%. of NaOH catalyst and 3:1–6:1 M ratio because lowamount of catalyst were not reacted with oil completely. Moreover,the ester yield decreases with the increase of NaOH catalyst con-

Fig. 6. Effect of methanol to oil molar ra

centration after 1.25 wt.% and 12:1 M ratio. Hence, increasingNaOH catalyst will cause insolubility to oil and methanol wouldachieve heterogonous phase for ester yield. Consequently, the in-crease of alkali catalyst causes the ester yield to decrease due toformation of emulsion and saponification to the gel formation.

3.3.3. Effect of reaction time and methanol to oil molar ratioThe effect of reaction time versus molar ratio to reduce viscosity

of methyl ester is shown in Fig. 8. The effect of reaction time wasobserved using varying time parameter at 1–3 h. The viscosity ofC. inophyllum achieved 3.45 mm2/s for 2 h and increase to3.80 mm2/s after 2 h of reaction. It was also observed that increas-ing reaction time beyond 2 h did not have much effect on reducingthe viscosity. This might be due to the effect of high molar ratiowhich causes water production during the transesterification andconsequently lead to incomplete further reaction. Besides, it wasobserved that biodiesel viscosity increased with increase in reac-tion time from 2.5 to 3 h for 12:1 and 15:1 M ratio. Similarity, thisis also stated in Rashid et al. [35] and Yusup and Khan [33] inwhich the reaction time of transesterification process at 1–3 h de-pends on physicochemical properties of oil. In this study, the ob-tained optimum conditions for C. inophyllum oils is 9:1 M ratioand the reaction took 2 h to complete.

tio and temperature on ester yield.

Fig. 7. Effect of alkaline catalyst vs. molar ratio on ester yield.

Fig. 8. Effect of reaction time vs. molar ratio on viscosity.

H.C. Ong et al. / Energy Conversion and Management 81 (2014) 30–40 37

3.4. Performance and emission analysis

The performance and exhaust emission were tested by varyingthe engine speed at full throttle (full load) for C. inophyllum biodie-sel diesel blends (CIB10, CIB20, CIB30 and CIB50) and diesel fuel.The performance of the engine is explored by evaluating theparameters like Bsfc, BTE and EGT. Besides, the exhaust emissionssuch as CO, NOx, and smoke opacity were also investigated. Basedon the experimental results, the effects density, viscosity, calorificvalue and blending ration on CI engine performance are analyzedin this section.

3.4.1. Brake specific fuel consumption (Bsfc)Brake specific fuel consumptions of biodiesel diesel blends

(CIB10, CIB20, CIB30 and CIB50) are shown in Fig. 9 and comparedto diesel fuel. CIB10 give quite satisfactory results in Bsfc which is302.9 g/kW h compared to diesel fuel (313.8 g/kW h) and CIB50(480.1 g/kW h) at 1900 rpm. CIB10 shows slightly lower Bsfc thandiesel fuel due to the biodiesel has a relatively higher heat ofvaporization than diesel, which affects the combustion [36]. Be-sides, the Bsfc of CIB20, CIB30 and CIB50 higher than CIB10 and

diesel fuel due to the lower calorific value of CIB20, CIB30 andCIB50. On the other hand, CIB50 has highest Bsfc of biodiesel dieselblend which is 621.4 g/kW h at 1500 rpm. As expected, the Bsfc ofthe biodiesel diesel blends increase compared to diesel is mainlydue to the low calorific value of the biodiesel [37,38]. Someresearchers have explained that the increase in Bsfc in relationwith the high density and viscosity of the biodiesel [2,39]. At fullload condition, the Bsfc decreases with engine speed until a mini-mum value at 1900 rpm, then increasing again with an increase inengine speed. This is because the heat loss from the combustionchambers walls is proportionately greater at low speeds. Thus,combustion efficiency is poorer causing the higher fuel consump-tion for the power produced. However, the friction power increasesat a rapid rate at higher speeds will cause in a slower increase inpower than in fuel consumption with a slight increase in Bsfc[40,41]. The decrease in Bsfc is a result of better physical andchemical conditions for combustion at low engine speeds. In addi-tion, the Bsfc was decrease in proportion of CIB10 compared to die-sel fuel and the CIB 10 is the optimum blending ratio for higherpower and torque output with lower Bsfc. This indicates that usingCIB10 increased oxygen content and higher combustion rate at the

250

300

350

400

450

500

550

600

650

1500 1700 1900 2100 2300 2500

Bsf

c (g

/kW

h)

Engine speed (rpm)

Diesel

CIB10

CIB20

CIB30

CIB50

Fig. 9. Brake specific fuel consumption for Calophyllum inophyllum biodiesel dieselblends compared to diesel fuel.

38 H.C. Ong et al. / Energy Conversion and Management 81 (2014) 30–40

same engine power for various engine speeds. Similar trends ofBsfc decrease with lower biodiesel blends ratio were also reportedby other researchers [13,42,43].

3.4.2. Brake thermal efficiency (BTE)Brake thermal efficiency is the ratio between work output and

the heat available introduced through fuel injection. The variationof brake thermal efficiencies using C. inophyllum blends and dieselfuel is shown in Fig. 10. It can be observed that the BTE values forCIB10, CIB20, CIB30 and CIB50 were 23.32%, 22.44%, 21.21% and20.63% compared to diesel fuel which was about 22.52% respec-tively. The high thermal efficiency of CIB10 has lower viscosityand increases the volatility compared to CIB20, CIB30 and CIB50.This enhances the fuel atomization leading to improved air fuelmixing. Therefore, the thermal efficiency for CIB20, CIB30 andCIB50 are lower than CIB10. This implies that fuel atomizationcharacteristics are different in blends with higher ratios of biodie-sel. It is clearly shown that BTE is inversely proportional to Bsfcwhich as Bsfc decreased the BTE values increased. This study cor-responds with Rahman et al. [2] which reported that CIB5 at1500 rpm has slightly higher combustion temperature and addi-tional oxygen content of the biodiesel facilitate better combustioncompared to diesel fuel. On the other hand, Muralidharan et al.[29] also reported that the oxygen content of the blends is sus-tained in the diffusive combustion phase which ignition delay isan important parameter in the combustion analysis.

520

530

3.4.3. Exhaust gas temperature (EGT)The trend result for exhaust gas temperatures versus with the

speed is shown in Fig. 11. This shows that the EGT increases asthe speed increases for all fuels in CI engines. This is due to the factthat fuel combustion amount in the combustion chamber withinthe unit time increases and consequently the heat energy producedincreases as the engine speed rise. The CIB10 shows slightly lowerexhaust gas temperatures compare with all other fuels. Lower EGT(510.8 �C) is an indication of good combustion of fuel in the com-bustion chamber for CIB10 at 2400 rpm. CIB10 has high cetanenumber, good formation of mixture and oxygenated fuel. However,the highest EGT for CIB20, CIB30 and CIB50 were obtained at518.2 �C, 520.8 �C and 525.3 �C, whereas the EGT for diesel fuel is

12

14

16

18

20

22

24

1500 1700 1900 2100 2300 2500

BT

E (

%)

Engine speed (rpm)

Diesel

CIB10

CIB20

CIB30

CIB50

Fig. 10. Brake thermal efficiency for Calophyllum inophyllum biodiesel diesel blendscompared to diesel fuel.

515.0 �C at 2400 rpm. The higher EGT of CIB20, CIB30 and CIB50could be due to lower calorific value and higher viscosity whichcause the poor atomization and not burnt properly in the combus-tion chamber. Panwar et al. [44] and Devan and Mahalakshmi [45]also observed the poor combustion characteristic caused by highviscosity of biodiesel diesel blends. As a result, lengthen combus-tion duration is the reasons for high viscosity of biodiesel dieselblends (20–40%) to have higher exhaust gas temperatures. More-over, Kumar et al. [46] reported that biodiesel diesel blends hashigher EGT and it will increase Bsfc compared to diesel fuel. Inaddition, this is an indication of higher EGT and it could be the pos-sible reason for lower performance for all CIB20, CIB30 and CIB50.

3.4.4. Nitrogen Oxides (NOx) emissionFig. 12 represents NOx emission at full throttle for C. inophyllum

biodiesel diesel blends and diesel fuel. The NOx emission is173.4 ppm, 182.2 ppm, 189.4 ppm and 196.7 for CIB10, CIB20,CIB30 and CIB50 at 2400 rpm respectively. There is a slightlyreduction of NOx at 1900 rpm which was 139.3 ppm (CIB10),148.5 ppm (CIB20), 154.9 ppm (CIB30) and 162.8 ppm (CIB50).However, the lowest NOx was observed for diesel fuel of119.7 ppm at 1500 rpm. The presence of oxygen in C. inophyllumbiodiesel blends caused higher NOx formation and it is indicatedthat exhaust gas temperature was increased as well [47]. Besides,Keskin et al. [48] also reported that NOx emissions are slightly in-creased due to increasing biodiesel concentration in the fuel. Thisis also agreed with _Ilkılıç and Aydın [49] which reported that bio-diesel with high oxygen content could adequate rising in high tem-perature and increases the formation rate of NOx. Furthermore,Ozsezen and Canakci [30] mentioned that the oxygen content isan affected in the NOx formation due to high exhaust gas temper-atures caused excess hydrocarbon oxidation. Lin et al. [50] ob-served that higher EGT leads to increase in NOx emission.

3.4.5. Carbon monoxide (CO) emissionFig. 13 shows the carbon monoxide emission for C. inophyllum

biodiesel diesel blends and diesel fuel. The CO emission was0.2297%, 0.2182%, 0.2427%, 0.2508% and 0.2578% for diesel fuel,CIB10, CIB20, CIB30 and CIB50 respectively. It is shows that COemission of CIB20, CIB30 and CIB50 were higher than diesel fuel.It is clear that CO emissions increase when the biodiesel blend ratiois added. This is due to higher viscosity of the CIB20, CIB30 andCIB50 which causes poor spray characteristics during the combus-tion process and cause the CO formation. The results of increasingCO emissions when the increase of biodiesel blending ratio wasagreed with Kivevele et al. [51] studies. Besides, Banapurmathet al. [52] observed that CO emissions for jatropha, honge and ses-ame biodiesel were higher compared to diesel on a single-cylinder,4-stroke diesel engine at a speed of 1500 rpm with 80% load. Anet al. [53] reported that CO increased when increase of biodieselblend ratio at lower engine speed is due to high viscosity of biodie-

440

450

460

470

480

490

500

510

1500 1700 1900 2100 2300 2500

EG

T (

o C)

Engine speed (rpm)

Diesel

CIB10

CIB20

CIB30

CIB50

Fig. 11. Exhaust gas temperature for Calophyllum inophyllum biodiesel diesel blendscompared to diesel fuel.

100

120

140

160

180

200

220

1500 1600 1700 1800 1900 2000 2100 2200 2300 2400

NO

x(p

pm v

ol)

Speed (rpm)

Diesel

CIB10

CIB20

CIB30

CIB50

Fig. 12. NOx emission with variation speed for Calophyllum inophyllum biodieseldiesel blends compared to diesel fuel.

10

15

20

25

30

35

40

45

1500 1600 1700 1800 1900 2000 2100 2200 2300 2400

Smok

e op

acity

(%

)

Speed (rpm)

DieselCIB10CIB20CIB30CIB50

Fig. 14. Smoke opacity with variation speed for Calophyllum inophyllum biodieseldiesel blends compared to diesel fuel.

H.C. Ong et al. / Energy Conversion and Management 81 (2014) 30–40 39

sel can influence combustion process and tend to cause incompletecombustion. However, CIB10 has lower CO emission than dieselfuel and other blends in this study. This is because low viscosityand density of CIB10 compared to other blends and higher cetanenumber compared to diesel fuel which will improved the combus-tion and reduced CO emissions. This result agreed with Sanjid et al.[54] which investigated that 10% of biodiesel blends have lower COemissions compared to diesel fuel and other blends. It is caused bylower density and viscosity leads good fuel atomization and sprayformation which leads to complete combustion and hence COemissions decrease. Moreover, Rizwanul Fattah et al. [55] statedthat CO emission reduced due to fuel rich zones formation as wellas advances injection and complete combustion.

3.4.6. Smoke opacitySmoke opacity is an indirect indicator of soot content in the ex-

haust gases. The variation of smoke opacity with engine speed forC. inophyllum biodiesel blends compared to diesel was shown inFig. 14. It was observed that smoke opacity for CIB10, CIB20,CIB30 and CIB40 was 24.7%, 27.92%, 30.81% and 32.98% respec-tively at 2400 rpm. However, the highest smoke opacity was found40.55% for diesel fuel at the same speed. The CIB has lower smokeopacity than diesel because the oxygen content present in biodie-sel diesel blends. This is agreed with Xue [56] which reported thatsmoke emissions for biodiesel diesel blends decreased due to theenrichment of oxygen content in the fuel. Besides, Buyukkayaet al. [57] also obtained that results that smoke opacity by usingbiodiesel blends was reduced compared to diesel due to presenceof oxygen in biodiesel. Moreover, many researchers were agreedthat the rich oxygen content in biodiesel will reduce smoke opacity[21,44,58]. Another reason for smoke emissions reduction for bio-diesel is because lower carbon to hydrogen ratio and absence ofaromatics compounds compared with diesel fuel. The lower carbonmolecule and higher oxygen content can decrease the tendency ofa fuel for soot production and reduce smoke opacity [43]. It wasagreed by Gumus and Kasifoglu [59] stated that biodiesel contains

0.00

0.05

0.10

0.15

0.20

0.25

0.30

1500 1600 1700 1800 1900 2000 2100 2200 2300 2400

CO

(%

vol

)

Speed (Rpm)

Diesel

CIB10

CIB20

CIB30

CIB50

Fig. 13. CO emission with variation speed for Calophyllum inophyllum biodieseldiesel blends compared to diesel fuel.

rich with oxygen can decrease smoke formation. On the otherhand, Zhang et al. [60] observed that start of combustion (SOC)for biodiesel blends is earlier than diesel. The result indicated thatearlier SOC for biodiesel blends and advanced injection timing canreduce the smoke emission. On other hand, high smoke opacity ofdiesel fuel was determined due to higher sulfur content comparedto biodiesel [61]. It was agreed with Çelikten et al. [47] which men-tioned that reduction of smoke opacity for biodiesel is principallybased on the high oxygen content of biodiesel and lower aromaticand sulfur content.

4. Conclusions

The C. inophyllum biodiesel was produced in the lab scale via de-gummed, acid esterification, neutralization and followed by basetransesterification process. The ester yield was found to be98.92% by using 1 wt.% catalyst concentration, 9:1 M ratio metha-nol to oil at 50 �C for 60 min. The present results obtained showthat degummed and neutralization process improved the fuelproperties of the C. inophyllum biodiesel. C. inophyllum methyl es-ters and the blends (CIB10, CIB20, CIB30 and CIB50) comply withASTM biodiesel standard. Besides, it has been found that CIB10gave good improvement in the engine performance with higherBTE from the engine performance test results. On the other hand,there is an improvement in fuel economy with lower Bsfc andEGT by using CIB10 compared to diesel fuel. Furthermore, CIB10 re-duced the CO and smoke opacity compared to diesel fuel but NOx

emission is slightly increased. The experimental results provedthat C. inophyllum biodiesel diesel blends is a potential alternativefuel which can be used effectively in diesel engine without modifi-cation. Finally, further studies on tribology and fuel economy needto be carried out before the C. inophyllum biodiesel diesel blendscan be utilized widely in the future.

Acknowledgements

The authors would like to acknowledge the Ministry of Educa-tion of Malaysia and The University of Malaya, Kuala Lumpur,Malaysia for the financial support under UM.C/HIR/MOE/ENG/06(D000006-16001), BK032-2013 and ERGS: ER022-2011A.

References

[1] Giakoumis EG, Rakopoulos CD, Dimaratos AM, Rakopoulos DC. Exhaustemissions of diesel engines operating under transient conditions withbiodiesel fuel blends. Prog Energy Combust 2012;38:691–715.

[2] Rahman SMA, Masjuki HH, Kalam MA, Abedin MJ, Sanjid A, Sajjad H.Production of palm and Calophyllum inophyllum based biodiesel andinvestigation of blend performance and exhaust emission in an unmodifieddiesel engine at high idling conditions. Energy Convers Manage2013;76:362–7.

[3] Ma F, Hanna M. Biodiesel production: a review. Biomass Bioenergy1999;70:1–15.

40 H.C. Ong et al. / Energy Conversion and Management 81 (2014) 30–40

[4] Demirbas A. Progress and recent trends in biodiesel fuels. Energy ConversManage 2009;50:14–34.

[5] Yusuf NNAN, Kamarudin SK, Yaakub Z. Overview on the current trends inbiodiesel production. Energy Convers Manage 2011;52:2741–51.

[6] Ong HC, Silitonga AS, Masjuki HH, Mahlia TMI, Chong WT, Boosroh MH.Production and comparative fuel properties of biodiesel from non-edible oils:Jatropha curcas, Sterculia foetida and Ceiba pentandra. Energy Convers Manage2013;73:245–55.

[7] Atabani AE, Silitonga AS, Ong HC, Mahlia TMI, Masjuki HH, Badruddin IA, et al.Non-edible vegetable oils: a critical evaluation of oil extraction, fatty acidcompositions, biodiesel production, characteristics, engine performance andemissions production. Renew Sust Energy Rev 2013;18:211–45.

[8] Palash SM, Masjuki HH, Kalam MA, Masum BM, Sanjid A, Abedin MJ. State ofthe art of NOx mitigation technologies and their effect on the performance andemission characteristics of biodiesel-fueled compression ignition engines.Energy Convers Manage 2013;76:400–20.

[9] Ong HC, Mahlia TMI, Masjuki HH. A review on energy pattern and policy fortransportation sector in Malaysia. Renew Sust Energy Rev 2012;16:532–42.

[10] Azam MM, Waris A, Nahar NM. Prospects and potential of fatty acid methylesters of some non-traditional seed oils for use as biodiesel in India. BiomassBioenergy 2005;29:293–302.

[11] Kumar A, Sharma S. Potential non-edible oil resources as biodiesel feedstock:an Indian perspective. Renew Sust Energy Rev 2011;15:1791–800.

[12] Demirbas� A. Biodiesel fuels from vegetable oils via catalytic and non-catalyticsupercritical alcohol transesterifications and other methods: a survey. EnergyConvers Manage 2003;44:2093–109.

[13] Buyukkaya E. Effects of biodiesel on a DI diesel engine performance, emissionand combustion characteristics. Fuel 2010;89:3099–105.

[14] Sahoo PK, Das LM. Process optimization for biodiesel production fromJatropha, Karanja and Polanga oils. Fuel 2009;88:1588–94.

[15] Dhar A, Kevin R, Agarwal AK. Production of biodiesel from high-FFA neem oiland its performance, emission and combustion characterization in a singlecylinder DICI engine. Fuel Process Technol 2012;97:118–29.

[16] Jena PC, Raheman H, Prasanna Kumar GV, Machavaram R. Biodiesel productionfrom mixture of mahua and simarouba oils with high free fatty acids. BiomassBioenergy 2010;34:1108–16.

[17] Hathurusingha S, Ashwath N, Subedi P. Variation in oil content and fatty acidprofile of Calophyllum inophyllum L. with fruit maturity and its implications onresultant biodiesel quality. Ind Crop Prod 2011;33:629–32.

[18] Friday JB, Okano D. Calophyllum inophyllum (kamani) species profiles forpacific Island Agroforestry, Traditional Tree Initiative, Hawaii; 2006<www.traditionaltree.org>.

[19] Dweck C, Meadows T. Tamanu (Calophyllum inophyllum) – the African, Asian,Polynesian and Pacific Panacea. Int J Cosmetic Sci 2002;24:1–8.

[20] Mohod AG, Bhor P, Kadam K, Sengar S, Khandetod Y. Study of properties ofCalophyllum inophyllum L. oil and its biodiesel. Int J Agric Eng 2010;3:125–9.

[21] Bora DK, Das LM, Babu MKG. Performance of mixed biodiesel fueled dieselengine. J Sci Ind Res 2008;67:73–6.

[22] Sahoo PK, Das LM, Babu MKG, Arora P, Singh VP, Kumar NR, et al. Comparativeevaluation of performance and emission characteristics of jatropha, karanjaand polanga based biodiesel as fuel in a tractor engine. Fuel2009;88:1698–707.

[23] Canakci M, Sanli H. Biodiesel production from various feedstocks and theireffects on the fuel properties. J Ind Microbiol Biot 2008;35:431–41.

[24] Rizwanul Fattah IM, Masjuki HH, Kalam MA, Mofijur M, Abedin MJ. Effect ofantioxidant on the performance and emission characteristics of a diesel enginefueled with palm biodiesel blends. Energy Convers Manage 2014;79:265–72.

[25] Pinzi S, Rounce P, Herreros J, Tsolakis A, Pilar DM. The effect of biodiesel fattyacid composition on combustion and diesel engine exhaust emissions. Fuel2013;104:170–82.

[26] Fernando S, Karra P, Hernandez R, Jha SK. Effect of incompletely convertedsoybean oil on biodiesel quality. Energy 2007;32:844–51.

[27] Kaya C, Hamamci C, Baysal A, Akba O, Erdogan S, Saydut A. Methyl ester ofpeanut (Arachis hypogea L.) seed oil as a potential feedstock for biodieselproduction. Renew Energy 2009;34:1257–60.

[28] Raj FRMS, Sahayaraj JW. A comparative study over alternative fuel (biodiesel)for environmental friendly emission. Adv Technol Climate Change Chennai,India; 2010. p. 80–6.

[29] Muralidharan K, Vasudevan D, Sheeba KN. Performance, emission andcombustion characteristics of biodiesel fuelled variable compression ratioengine. Energy 2011;36:5385–93.

[30] Ozsezen AN, Canakci M. Determination of performance and combustioncharacteristics of a diesel engine fueled with canola and waste palm oil methylesters. Energy Convers Manage 2011;52:108–16.

[31] Ramírez-Verduzco LF, Rodríguez-Rodríguez JE, Jaramillo-Jacob AR. Predictingcetane number, kinematic viscosity, density and higher heating value ofbiodiesel from its fatty acid methyl ester composition. Fuel 2012;91:102–11.

[32] Ushakov S, Valland H, Æsøy V. Combustion and emissions characteristics offish oil fuel in a heavy-duty diesel engine. Energy Convers Manage2013;65:228–38.

[33] Yusup S, Khan MA. Base catalyzed transesterification of acid treated vegetableoil blend for biodiesel production. Biomass Bioenergy 2010;34:1500–4.

[34] Tiwari S, Saxena M, Tiwari SK. Mahua-oil-based resins for the high-temperature curing of fly ash coatings. J Appl Polym Sci 2003;87:110–20.

[35] Rashid U, Rehman HA, Hussain I, Ibrahim M, Haider MS. Muskmelon (Cucumismelo) seed oil: a potential non-food oil source for biodiesel production. Energy2011;36:5632–9.

[36] Jasanpreet S, Narinder K, Mahlac SK. Rice bran oil biodiesel as an alternative insingle cylinder CI engine with DI ethyl ether blends. Int J Emerg Sci Eng2013;1:31–4.

[37] Al-Dawody MF, Bhatti SK. Optimization strategies to reduce the biodiesel NOxeffect in diesel engine with experimental verification. Energy Convers Manage2013;68:96–104.

[38] Vedharaj S, Vallinayagam R, Yang WM, Chou SK, Chua KJE, Lee PS.Experimental investigation of kapok (Ceiba pentandra) oil biodiesel as analternate fuel for diesel engine. Energy Convers Manage 2013;75:773–9.

[39] Silitonga AS, Masjuki HH, Mahlia TMI, Ong HC, Chong WT, Boosroh MH.Overview properties of biodiesel diesel blends from edible and non-ediblefeedstock. Renew Sust Energy Rev 2013;22:346–60.

[40] Silitonga AS, Masjuki HH, Mahlia TMI, Ong HC, Chong WT. Experimental studyon performance and exhaust emissions of a diesel engine fuelled with Ceibapentandra biodiesel blends. Energy Convers Manage 2013;76:828–36.

[41] Tesfa B, Mishra R, Zhang C, Gu F, Ball AD. Combustion and performancecharacteristics of CI (compression ignition) engine running with biodiesel.Energy 2013;51:101–15.

[42] Qi DH, Geng LM, Chen H, Bian YZ, Liu J, Ren XC. Combustion and performanceevaluation of a diesel engine fueled with biodiesel produced from soybeancrude oil. Renew Energy 2009;34:2706–13.

[43] Qi DH, Lee CF, Jia CC, Wang PP, Wu ST. Experimental investigations ofcombustion and emission characteristics of rapeseed oil–diesel blends in a twocylinder agricultural diesel engine. Energy Convers Manage 2014;77:227–32.

[44] Panwar NL, Shrirame HY, Rathore NS, Jindal S, Kurchania AK. Performanceevaluation of a diesel engine fueled with methyl ester of castor seed oil. ApplTherm Eng 2010;30:245–9.

[45] Devan PK, Mahalakshmi NV. Study of the performance, emission andcombustion characteristics of a diesel engine using poon oil-based fuels.Fuel Process Technol 2009;90:513–9.

[46] Kumar N, Varun, Chauhan SR. Performance and emission characteristics ofbiodiesel from different origins: a review. Renew Sust Energy Rev2013;21:633–58.

[47] Çelikten _I, Mutlu E, Solmaz H. Variation of performance and emissioncharacteristics of a diesel engine fueled with diesel, rapeseed oil andhazelnut oil methyl ester blends. Renew Energy 2012;48:122–6.

[48] Keskin A, Gürü M, Altiparmak D, Aydin K. Using of cotton oil soapstockbiodiesel–diesel fuel blends as an alternative diesel fuel. Renew Energy2008;33:553–7.

[49] _Ilkılıç C, Aydın H. Determination of performance and exhaust emissionsproperties of B75 in a CI engine application. Fuel Process Technol2011;92:1790–5.

[50] Lin B-F, Huang J-H, Huang D-Y. Experimental study of the effects of vegetableoil methyl ester on DI diesel engine performance characteristics and pollutantemissions. Fuel 2009;88:1779–85.

[51] Kivevele TT, Kristóf L, Bereczky Á, Mbarawa MM. Engine performance, exhaustemissions and combustion characteristics of a CI engine fuelled with crotonmegalocarpus methyl ester with antioxidant. Fuel 2011;90:2782–9.

[52] Banapurmath NR, Tewari PG, Hosmath RS. Performance and emissioncharacteristics of a DI compression ignition engine operated on Honge,Jatropha and sesame oil methyl esters. Renew Energy 2008;33:1982–8.

[53] An H, Yang WM, Chou SK, Chua KJ. Combustion and emissions characteristicsof diesel engine fueled by biodiesel at partial load conditions. Appl Energy2012;99:363–71.

[54] Sanjid A, Masjuki HH, Kalam MA, Rahman SMA, Abedin MJ, Palash SM.Production of palm and jatropha based biodiesel and investigation of palm-jatropha combined blend properties, performance, exhaust emission and noisein an unmodified diesel engine. J Clean Prod 2013:1–9.

[55] Rizwanul Fattah IM, Masjuki HH, Liaquat AM, Ramli R, Kalam MA, RiazuddinVN. Impact of various biodiesel fuels obtained from edible and non-edible oilson engine exhaust gas and noise emissions. Renew Sust Energy Rev2013;18:552–67.

[56] Xue J. Combustion characteristics, engine performances and emissions ofwaste edible oil biodiesel in diesel engine. Renew Sust Energy Rev2013;23:350–65.

[57] Buyukkaya E, Benli S, Karaaslan S, Guru M. Effects of trout-oil methyl ester on adiesel engine performance and emission characteristics. Energy ConversManage 2013;69:41–8.

[58] Chattopadhyay S, Sen R. Fuel properties, engine performance andenvironmental benefits of biodiesel produced by a green process. ApplEnergy 2013;105:319–26.

[59] Gumus M, Kasifoglu S. Performance and emission evaluation of a compressionignition engine using a biodiesel (apricot seed kernel oil methyl ester) and itsblends with diesel fuel. Biomass Bioenergy 2010;34:134–9.

[60] Zhang X, Gao G, Li L, Wu Z, Hu Z, Deng J. Characteristics of combustion andemissions in a DI engine fueled with biodiesel blends from soybean oil. SAEtechnical paper, vol. 1; 2008. p. 1832–5.

[61] Usta N. An experimental study on performance and exhaust emissions of adiesel engine fuelled with tobacco seed oil methyl ester. Energy ConversManage 2005;46:2373–86.