Fuel 112 (2013) 203–207

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Fuel

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Evaluation of methyl ester of microalgae oil as fuel in a diesel engine

0016-2361/$ - see front matter � 2013 Elsevier Ltd. All rights reserved.http://dx.doi.org/10.1016/j.fuel.2013.05.016

⇑ Corresponding author. Tel.: +90 5052106272; fax: +90 3223386741.E-mail address: gtuccar@cu.edu.tr (G. Tüccar).

Gökhan Tüccar ⇑, Kadir AydınÇukurova University, Department of Mechanical Engineering, 01330 Adana, Turkey

h i g h l i g h t s

� The manuscript presents availability of methyl ester of microalgae oil as fuel.� Fuel properties of diesel fuel, microalgae biodiesel and its blends were determined.� The engine performance tests were carried out.� Microalgae biodiesel was identified as a promising alternative fuel.

a r t i c l e i n f o

Article history:Received 22 July 2011Received in revised form 29 April 2013Accepted 1 May 2013Available online 25 May 2013

Keywords:MicroalgaeBiodieselFuel propertiesEngine performanceExhaust emissions

a b s t r a c t

Biodiesel can be obtained from various resources. However, the usage of vegetable oils as biodiesel sourcemay impact global food market. Therefore, scientists focus on searching new biodiesel sources which arenon-edible and easy to obtain. Microalgae have gained much attention recently due to their high growingrates and high oil contents. The objective of this study is to identify availability of microalgae biodiesel indiesel engines as alternative fuel. Microalgae biodiesel was blended with diesel fuel with the volumetricratio of 5%, 10%, 20% and 50%. Fuel properties of blends and pure microalgae biodiesel were found out andthe performance characteristics and exhaust emissions of the engine fueled with blends were analyzed.The results showed that, although microalgae biodiesel caused a slight reduction in torque and brakepower values, the emission values of the engine using microalgae biodiesel were improved.

� 2013 Elsevier Ltd. All rights reserved.

1. Introduction

Due to their higher thermal efficiency and durability, compres-sion ignition engines are more useful than spark ignition engines infield of heavy transportation and agriculture sectors. However, ra-pid increase in transportation fuel demand, environmental con-cerns and depletion of fossil fuels forces scientists to developvegetable oil-based derivatives that approximate the propertiesand performance of petroleum-based diesel fuel. Vegetable oilscan be directly used in diesel engines as they have a high cetanenumber and calorific value, which are very similar to those of die-sel. However, the brake thermal efficiency of vegetable oils is infe-rior to that of diesel. This leads to problems of high smoke, HC andCO emissions, however transesterification of vegetable oils resultsin better performance and reduced emissions. Biodiesel has a morefavorable combustion emission profile, such as low emissions ofcarbon monoxide, particulate matter and unburned hydrocarbons.Due to its relatively high flash point and good lubrication proper-ties, biodiesel became popular as a new alternative energy source[1–6]. Combustion of biodiesel alone provides over a 90% reduction

in total unburned hydrocarbons (HC), and a 75–90% reduction inpolycyclic aromatic hydrocarbons (PAHs). Biodiesel further pro-vides significant reductions in particulates and carbon monoxidethan petroleum diesel fuel. Biodiesel provides a slight increase ordecrease in nitrogen oxides depending on engine family and test-ing procedures [7]. Recent investigations have indicated that theuse of biodiesel can decrease 90% of air toxicity and 95% of cancerscompared to common diesel source [8]. Currently, vegetable oils,waste cooking oils and animal fats are generally used as biodieselfeed stock; however, the limited supply of these feed stocks limitsthe further expansion of biodiesel production and the price of thesefeedstocks accounts for 60–75 of the total cost of biodiesel [9]. Inaddition to, the usage of vegetable oils as biodiesel feedstock hasgenerated a lot of controversy, mainly due to its impact on globalfood markets and on food security. Currently, about 84% the worldbiodiesel production is met by rapeseed oil. The remaining portionis from sunflower oil (13%), palm oil (1%) and soybean oil and oth-ers (2%). Thus, instead of arable land being utilized to grow food, itis being used to grow fuel, in other words; by converting edible oilsinto biodiesel, food resources are actually being converted intoautomotive fuels [10,11]. The use of edible vegetable oils mightcause starvation especially in the developing countries [12]. Theseproblems have raised doubts about the potential of biodiesel to

204 G. Tüccar, K. Aydın / Fuel 112 (2013) 203–207

replace fossil fuels and sustainability of its production [13,14]. Toreduce the dependency on edible oil, alternative biofuel sources,such as non-food feedstocks, have been developed to produce bio-diesel since it is necessary to find new feedstock suitable for bio-diesel production, which does not drain on the edible vegetableoil supply [15,16]. Recently, non-edible vegetable oils have beenconsidered as prospective feedstocks for biodiesel production. Thisis mainly attributed to their ability to overcome the problems offood versus fuel crisis related to edible oils [17].

Microalgae are microscopic photosynthetic organisms that arefound in both marine and freshwater environments [18]. Microal-gae are considered as a second generation feedstock for productionof biofuels since they have ability to synthesize high amount of lip-ids [19,20]. In addition to, biodiesel could be produced from vari-ous species of microalgae [21]. Two biggest advantages ofmicroalgae are their fast growing ability and their high oil con-tents. Microalgae which can grow faster than terrestrial crops havedoubling times down to 3.5 h during their exponential growthphase. Oil content in microalgae can exceed 80% by weight of drybiomass; however, oil levels of 20–50% are quite common [22].Microalgae require much less land area than other biodiesel feedstocks of agricultural origin, up to 49 or 132 times less when com-pared to rapeseed or soybean crops [23].

A lot of researches have been conducted about usage of differ-ent oils in existing diesel engines as fuel [24–32]. However, mostof these oils are edible. The emphasis of the present work is toexperimentally evaluate the possibilities of using biodiesel devel-oped from one of the most important non-edible resources: micro-algae. Therefore, the objective of this study was to identifyavailability of microalgae biodiesel in diesel engines. Fuel proper-ties of microalgae biodiesel and its blends were determined andthe performance, emission and combustion characteristics of bio-fuel blends were evaluated.

Table 1Technical specifications of the test engine.

Brand Mitsubishi canter

Model 4D34-2A

2. Materials and methods

2.1. Biodiesel production

Microalgae oil used in biodiesel production was purchased fromSoley Biotechnology Institute. During the microalgae biodiesel pro-duction, the necessary amount of catalyst (NaOH) for the transe-sterification reaction (0.4% by weight of the oil) was dissolved inmethanol and added to the reactor after heating the microalgaeoil to 65 �C; the reaction was performed at 60–61 �C and the mix-ture was stirred by the help of a magnetic stirrer at about 600 rpmduring 1 h. After completion of the transesterification reaction, themixture was cooled to room temperature and then transferred to aseparatory funnel and separation of the ester and glycerin phaseswas performed by letting them stand for 8 h in the separatory fun-nel. The crude ester phase was washed 3 times with hot water at 1/5 water to ester phase ratio. After washing process, the mixturewas waited in seperatory funnel during 30 min and by this waywater is separated from methyl ester. Since purity level has strongeffects on fuel properties, in order to provide water content to beless than 0.1, drying process was conducted by heating the biodie-sel to 105 �C during 1 h until bright color occurred. Finally, filteringprocess was done in order to ensure that the end product is ofexcellent quality. Two batches of transesterification reaction wereconducted. Therefore, two number of fuel samples were preparedin order to see the difference from batch to batch.

Type Direct injection diesel with glow plugDisplacement 3907 ccBore 104 mmStroke 115 mmPower 89 kW @ 3200 rpmTorque 295 N m @ 1800 rpm

2.2. Property analysis

In this study, mixtures consisting of methyl ester producedfrom microalgae oil and diesel fuel were used as alternative fuel.

100% diesel fuel was also used as reference. MB (microalgae biodie-sel) fuel and diesel fuel were mixed at the volumetric ratios of 5%,10%, 20% and 50%. Mixtures were prepared just before the tests.Important physical fuel properties of diesel fuel, microalgae biodie-sel and the mixtures were determined. The tests were performedthree times, and averages of three results were taken for both fuelsamples obtained from separate batches of transesterification reac-tion. The maximum coefficients of variation between the resultswere about 0.4% and 0.7% for three experiments and for two sepa-rate fuel samples, respectively. Therefore, the differences betweenresults obtained from three experiments were insignificant for twoseparate fuel samples.

2.3. Experimental set-up

In this study, experiments were conducted on a four stroke, fourcylinder diesel engine. Specifications and the schematic diagram ofthe engine are presented in Table 1 and Fig. 1, respectively. This en-gine was coupled to a hydraulic dynamometer which has torquerange of 0–1700 N m and speed range of 0–7500 rpm to measureengine torque. Before starting to the experiment, the engine wasoperated with the new fuel for sufficient time to clean out theremaining fuel from the previous experiment. Engine performancevalues such as torque and specific fuel consumption were read bythe help of a computer program of dynamometer control unitwhich can take values in two second time intervals and exhaustemissions such as CO and NOX were obtained by the help of an-other computer program.

3. Results and discussion

3.1. Fuel properties

The measured physical fuel properties of microalgae oil, andmethyl ester of microalgae oil are compared with those of dieselfuel and given in Table 2. The measured physical properties of mic-roalgae biodiesel like density, viscosity, pour point and heating va-lue are comparable with those of diesel fuel. It can also be observedfrom the Table 2 that except its low cetane number, all other mea-sured properties of microalgae biodiesel are within the EuropeanBiodiesel Standard (EN 14214). However, low cetane number ofmicroalgae can be compensated by mixing it with diesel fuel, asit can be seen from the Table 2, cetane numbers of all blends meetEN 14214 Standard.

3.2. Engine performance

3.2.1. Brake power and torque outputFig. 2 shows the variation of brake power according to different

engine speed values. As it can easily be seen in Fig. 2, power of theengine was reduced with increasing percentage of microalgae bio-diesel in the blends (there is an average of about 6% reduction forB100 compared to diesel fuel). The reason of this reduction can bebecause of incomplete combustion of the fuel due to low cetane

Fig. 1. Layout of experimental setup.Engine Speed (rpm)

1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000

Brak

e Po

wer

(kW

)

25

30

35

40

45

50

55

60

65

DieselB5B10B20B50B100

Fig. 2. Brake power output versus engine speed for the test fuels.

Engine Speed (rpm)1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000

Torq

ue (N

m)

120

140

160

180

200

220

240

260

280

DieselB5B10B20

B50B100

Fig. 3. Torque output versus engine speed for the test fuels.

G. Tüccar, K. Aydın / Fuel 112 (2013) 203–207 205

number of microalgae biodiesel. For all fuels the maximum poweroutput was obtained at about 2400 rpm.

The torque output of test fuels is shown in Fig. 3. Torque outputvalues reduced with the increasing concentration of microalgaebiodiesel in the blends (there is an average of 5.3% reduction forB100 compared to diesel fuel). The value of the power reductionamount is higher at high engine speeds (about 13% at 2800 rpm)than that of at lower engine speeds (about 3.8% at 1200 rpm).The maximum torque values for all fuels were obtained at an en-gine speed of 1400–1600 rpm. The torque output reduced throughhigher engine speeds.

There are also publications reporting decreases in brake poweror torque when using biodiesel [33–37].

3.2.2. Carbon monoxide emissionCO emission is due to incomplete combustion and depends on

many parameters such as engine temperature, and air/fuel ratio.[38]. Generally a reduction in CO emission values occur when bio-diesel is used instead of diesel fuel since biodiesel contains addi-tional oxygen and this additional oxygen enhances completecombustion [39]. The variation of CO emissions for different fuelsis compared in Fig. 4. It can be observed from the Fig. 4 that thereis an average of 9.4% reduction in CO emission values when micro-algae biodiesel was used instead of diesel fuel. With regard to mostof the other authors, also a decrease in CO emissions occurs whensubstituting diesel fuel with biodiesel [40–41]. These lower COemissions of biodiesel may be due to its high oxygen content ascompared to diesel. The extra oxygen molecule present in the bio-diesel chain might have been used to convert some of the CO intoCO2 during combustion, thus CO formation is reduced [42]. For allof the test fuels, CO emissions increased with increasing enginespeed. This trend may occurred due to injected fuel amount whichincreases parallel to increasing engine load.

3.2.3. Nitric oxides emissionAnother significant diesel emissions are nitric oxides. There are

many factors that have an impact on NOX formation from diesel

Table 2Properties of test fuels.

Properties Diesel fuel B5 B10 B25

Density (kg/L) 0.833 0.835 0.838 0.84Cetane number 56.46 56.04 55.08 54.1Viscosity (at 40 �C) (mm2/s) 2.37 2.62 2.84 2.88Pour point (�C) �10 �12 �12 �12

Flash point (�C) 58.5 68.5 78.5 78.5Heating value (kJ/kg) 45,254 44,674 44,107 43,5

engine. NOX formation is primarily a function of pressure, reactiontemperature, residence time of combustion products, premixedportion of combustion, availability of excess oxygen, ignition delayperiod, heat removal rate and the operational parameters of theengine [43]. The variation of NOX emission values for different testfuels is presented in Fig. 5. On an average, 9.3% reduction in NOX

was obtained for biodiesel and as compared to diesel. Fig. 5 showsthat high oxygen content does not lead to increases in NOX forma-tion. Reduction in NOX value can be due to less air drawn into thecylinder during the combustion of microalgae biodiesel. Heat re-lease rate of microalgae biodiesel is also lower due to its lowerheating value which will lead to lower peak temperatures. Nitro-gen oxides formation strongly depends on peak temperature,which explains the observed phenomenon.

B50 MB European biodiesel standard (EN 14214)

3 0.859 0.886 0.860–0.9009 51.55 48.31 >51

3.51 4.47 3.5–5.0�12 �12 Summer <4.0

Winter <�1.078.5 165.5 >120

676 42,890 40,045 –

Engine Speed (rpm)1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000

CO

(ppm

)

150

200

250

300

350

400

EurodieselMB

Fig. 4. Comparison of CO values for diesel fuel and microalgae biodiesel.

Engine Speed (rpm)1000 1200 1400 1600 1800 2000 2200 2400 2600 2800 3000

NO

x (p

pm)

700

800

900

1000

1100

1200

1300

EurodieselMB

Fig. 5. Comparison of NOx values for diesel fuel and microalgae biodiesel.

206 G. Tüccar, K. Aydın / Fuel 112 (2013) 203–207

Although most of the literature shows a slight increase in NOX

emissions when using biodiesel fuel [44–52], some works showingdifferent effects have been found [53]. Some researchers also re-ported lower NOX emissions with biodiesel [54–56].

3.3. Cost analysis of microalgae biodiesel

Cost analysis is needed to evaluate the feasibility and profitabil-ity of algae biodiesel and to determine if it is competitive enoughto be commercialized. The process of making biodiesel fuel frommicroalgae involves several steps: growing algae in engineeredponds (growth), harvesting the biomass in settling ponds (harvest),extracting the algal oils from the biomass (extraction), and con-verting the algal oil into biodiesel (conversation). The first threesub-processes are performed at an aquatic farm using agriculturalengineering principles. Conversion of algal oil to biodiesel is gener-ally accomplished in a chemical plant using a simple process to re-duce the size and viscosity of the algal oil molecular compounds.

[57]. Harvesting costs contribute 20–30% to the total cost of al-gal cultivation with majority of the cost contribute to cultivationexpenses [58]. The estimated cost of producing a kilogram of mic-roalgal biomass is $2.95 and $3.80 for photobioreactors and race-ways, respectively for the facilities. If the annual biomassproduction capacity is increased to 10,000 t, the cost of productionper kilogram reduces to roughly $0.47 and $0.60 for photobioreac-tors and raceways, respectively. Assuming that the biomasscontains 30% oil by weight, the cost of biomass for providing a liter

of oil would be something like $1.40 and $1.81 for photobioreac-tors and raceways, respectively [22]. However, for microalgal bio-diesel to be competitive with petrodiesel, algal oil price should beless than $0.48/L [58].

4. Conclusions

Fuel properties of diesel fuel, microalgae biodiesel and itsblends were determined. It is found that except its low cetanenumber, microalgae biodiesel satisfies European Biodiesel Stan-dards (EN 14214), however; its low cetane number can be compen-sated by mixing microalgae biodiesel with diesel fuel.

The power and torque output of engine fueled with microalgaebiodiesel decreased when microalgae biodiesel was used.

CO and NOX emission values improved with microalgae biodie-sel usage.

Finally, it can be concluded that, microalgae biodiesel can beused as alternative fuel in conventional diesel engines, by thisway exhaust emission values can be improved.

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