Content uploaded by Azhari Muhammad Syam
Author content
All content in this area was uploaded by Azhari Muhammad Syam on May 20, 2015
Content may be subject to copyright.
Smart Grid and Renewable Energy, 2013, 4, 281-286
http://dx.doi.org/10.4236/sgre.2013.43034 Published Online June 2013 (http://www.scirp.org/journal/sgre)
281
Waste Frying Oils-Based Biodiesel: Process and Fuel
Properties
Azhari Muhammad Syam1,2*, Leni Maulinda1, Ishak Ibrahim1, Syafari Muhammad1
1Department of Chemical Engineering, Malikussaleh University, Lhokseumawe, Indonesia; 2Institute of Advanced Technology,
Universiti Putra Malaysia, Serdang, Malaysia.
Email: *armuh@yahoo.com
Received April 4th, 2013; revised May 6th, 2013; accepted May 13th, 2013
Copyright © 2013 Azhari Muhammad Syam et al. This is an open access article distributed under the Creative Commons Attribution
License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ABSTRACT
The conversion of waste frying oil into a valuable methyl ester (biodiesel) has been successfully conducted and also the
acid pre-treatment process was carried out prior to the main biodiesel production process for lowering waste frying oil
free fatty acid (FFA) content below 1%. The physicochemical properties of biodiesel were analyzed to ensure the prod-
uct could meet the standards of fuel properties. The methanolysis was selected as the biodiesel production technique
under various mixing speeds namely 350, 400 and 450 rpm, while the other parameters are maintained at the optimum
process conditions such as methanol to oil molar ratio is 6:1, percentage of catalyst loading is 1.0% wt, reaction tem-
perature is 60˚C, and reaction time is 50 min. Also, the investigation on the kinematic viscosity, density and flash point
of biodiesel was performed against a number of rpm. The standards of ASTM D 6751 were applied to measure the en-
tire prescribed properties of biodiesel. The highest yield of biodiesel obtained was 99%. The values of flash point, ki-
nematic viscosity and density were in the range of specified limitations. Other biodiesel properties fulfilled the diesel
engine application requirements.
Keywords: Waste Frying Oils; Biodiesel; Fuel Properties
1. Introduction
While global warming and green house gas effect corre-
spond to a part of issues in the green environmental top-
ics of worldwide. Biodiesel takes a significant role in
reducing the accumulation of green house gas and main-
tain a globally benign environmentally. As vehicle fuel,
biodiesel has some benefits due to domestic and renew-
able resources, also its application without requiring a
major modification of engine. In terms of clinical aspects,
biodiesel is suitable for environmentally friendly fuels
because of there are not any toxic compounds produced
during the period of combustion. In this matter, Demir-
bas [1] reported that the advantages of biodiesel is better
quality of exhaust gas emissions, its biodegradability and
its contribution to the reduction in carbon dioxide (CO2)
emissions.
Most researchers have selected the cheapest and sim-
plest technique of biodiesel production. The others have
applied the expensive methods once the untreated oil was
used as feedstock of biodiesel. Even though, the eco-
nomical aspect is highly associated with the technique of
biodiesel production. However, the quality of biodiesel
should be taken into account when one of techniques is
applied as reported by Jain and Sharma [2]. It is due to
the process may take place either with catalysts such as
alkaline [3], acid [4] and enzyme [5,6] or without cata-
lysts [7]. In an industrial scale, the alkaline catalyst is the
most prefer way due to low cost, easy to install and
above all, its high reaction rate without requiring a large
reactor volume and save the capital of production [8].
As a rule, the methanolysis process proceeds under
three step wise reactions as indicated in Scheme 1. Based
on the reaction stoichiometry, one mole of triglyceride
requires three moles of methanol to produce three moles
of fatty acid methyl esters and one mole of glycerol as
shown in Scheme 2.
The nowadays serious problem for biodiesel produc-
tion is the high price of vegetable oil which leads to a
highly expensive of biodiesel product price compared to
that of petroleum based diesel product. For anticipating
such that situation, many researchers have started to util-
ize the waste resource based oils as reaction feedstock.
*Corresponding author.
Copyright © 2013 SciRes. SGRE
Waste Frying Oils-Based Biodiesel: Process and Fuel Properties
282
3
TG+CH OH DG+RCOOCH
Alkaline
3
3
3
Alkaline
3
DG+CH OH MG+RCOOCH
Alkaline
3
MG+CH OH GL+RCOOCH
Scheme 1.
CH
2
-OCOR
1
CH-OCOR
2
CH
2
-OCOR
3
CH
3
OH
CH
2
-OH
CH
2
-OH
R
2
-OCOCH
3
R
1
-OCOCH
3
R
3
-OCOCH
3
Triglyceride Methanol Glycerol Methyl Esters
OCH
3-
CH-OH + +
Scheme 2.
As Berrios et al. [8] reported that waste cooking oils
are good raw material because of their low cost and the
environmental advantage of the residue valorisation. An-
other feedstock which corresponds to bio-based oils is
the slaughterhouse waste.
The objective of this study is to synthesize the oil
waste into biodiesel and investigate the physicochemical
properties of biodiesel product for engine application
such as kinematic viscosity, density, flash point, water
content, calorific value, iodine value, total acid number
(TAN), pour point, and cetane index. The analysis of
those properties refers to the standards of ASTM D 6751
[9], where TG, DG, MG, GL, and R denote triglyceride,
diglyceride, monoglyceride, glycerol and long hydrocar-
bon chain.
2. Materials and Methods
2.1. Material
The feedstock employed in this work is waste frying oils
that are collected from restaurants and houses. Isopropa-
nol, phenolphthalein and potassium hydroxide are util-
ized for determining acid values of waste frying oil and
the oil after treating. While the sulphuric acid is used for
the pre-treatment process, sodium methoxide is used as
catalyst in the methanolysis process and methanol is ap-
plied for both pre-treatment and methanolysis processes.
Ethyl acetate and BSTFA are for gas chromatography
sample preparation. The equipments involved are three
neck flask, oil bath, graham condenser, thermometer, hot
plate complete with stirrer, and other related glass wares.
2.2. Acid Pre-Treatment Process
In this work, the steps of acid pre-treatment (esterifica-
tion) are carried out. Initial step, the high free fatty acid
waste frying oil is poured into the three neck flask (reac-
tor) and heated. The mixing solution of methanol with
catalyst (sulphuric acid) is also heated prior to be added
into the reactor. After the reaction completing, the prod-
ucts are allowed for 2 h settling down in a separation
funnel and then, the methanol-water fraction at the top
layer is removed.
2.3. Methanolysis
The treated oil is used as the feedstock. Fatty acid com-
position of the waste frying oil is given in Table 1. The
oil needs to be heated after pouring into the reactor prior
to the excess reactant and catalyst are added. The reactor
is filled up with 150 g of treated oil and heat until 60˚C.
Then, the mixture of methanol with catalyst is added at
which the reaction is assumed to commence. The flow
sheet of completed biodiesel production process is shown
in Figure 1.
2.4. Analytical Procedure
The free fatty acids content of the waste frying oil and
treated oil is determined using acid base titration tech-
nique. A standard solution of 0.1 N alkali solution is used.
The titration method is as follows. The specified weight
of oil sample is measured in a flask, add 50 ml of iso-
propanol and thus, shake it gently while titrating with
standard alkali to the first permanent pink colour. The
colour must persist for 30 seconds.
2.5. Gas Chromatography Analysis
GC (gas chromatography) analysis is performed for iden-
tifying the hydrocarbon compounds such as fatty acids
and methyl esters. The separation is carried out by using
capillary column Rtx-5MS 30 m × 0.25 mm ID, 0.25 μm
with helium at 137.7 ml/min as a carrier gas and 1:100 of
split ratio.
Table 1. Fatty acid composition of waste frying oils.
Fatty acids Formula Weight
Octanoic C8H16O2 6.18
Decanoic C10H20O2 7.13
Dodecanoic C12H24O2 35.36
Tetradecanoic C14H28O2 24.68
Hexadecanoic C16H32O2 12.53
9-Hexadecenoic C16H30O2 1.17
Octadecanoic C18H36O2 4.63
9-Octadecenoic C18H34O2 8.32
Copyright © 2013 SciRes. SGRE
Waste Frying Oils-Based Biodiesel: Process and Fuel Properties
Copyright © 2013 SciRes. SGRE
283
Figure 1. Process flow diagram of biodiesel production.
3. Results and Discussion
3.1. Biodiesel Synthesis
The production of biodiesel from triglyceride of waste
frying oil takes place slowly at the lower mixing speed
(350 rpm). This phenomenon is happened because of the
mechanical nature which contributes to the process that
is going on ineffectively. However, at higher mixing
speeds, the yield of biodiesel increases significantly, in
particular at higher of reaction time as shown in Figure 2.
It proves that the methanolysis process is extremely af-
fected by the rpm. Also, it can be seen that the reaction is
slow during the initial reaction time due to the mixing
and excess reactant dispersion with triglyceride (Figure
2). Nevertheless, the reaction yield increased steadily
from 30 min of reaction. Especially, at both 400 rpm and
450 rpm of mixing speeds, the yield of methyl ester en-
hances proportionally. The conversion of waste frying oil
triglyceride into valuable methyl ester reached the maxi-
mum yield at 50 min of reaction time. The highest yield
of biodiesel product obtained in this work is 99%. The
similar study has been done by Wang et al. [10] which
attained 97% of biodiesel conversion from waste cooking
oil. Also, Zhang et al. [11] have conducted the assess-
ment on the technological and process for biodiesel pro-
duction from oil waste.
Figure 2. The yield of biodiesel at various mixing speeds
(rpm).
tigation on kinematic viscosity of biodiesel over rpm is
carried out. The findings are reported that the kinematic
viscosity of biodiesel declines exponentially at every
selected rpm for whole reaction times. Above all, at 30
until 90 min, the slopes appear to be the same (Figure 3),
except for 60 min of reaction time, there is a slightly dif-
ference of slopes in particular after 350 rpm. In the real-
ity, the kinematic viscosity decreases with increase in
rpm of mixing intensity. Therefore, at low rpm, the un-
successful reaction has caused the biodiesel viscosity still
remains at high level. As the engine fuel, according to
Heywood [14] and Coulson & Richardson [15], the
higher viscosity results in the mixture to burn lean in the
engine as fuel moves slowly through the fuel filter and
fuel lines. In addition, the higher viscosity of biodiesel
fuel causes inadequate atomization and incomplete com-
3.2. Study on Kinematic Viscosity
Kinematic viscosity is one of the most effecting parame-
ters on the performance of engine and the emission char-
acteristics [12]. Also, according to Bhale et al. [13], ki-
nematic viscosity is the property of a fluid by virtue of
which it offers resistance to flow. In this work, the inves-
Waste Frying Oils-Based Biodiesel: Process and Fuel Properties
284
Figure 3. Effect of rpm on the kinematic viscosity.
bustion.
Although, the mixing intensity is surely increased until
450 rpm, from Figure 3 it can be observed that at 400
rpm and 60 min of reaction time, the feasible kinematic
viscosity of biodiesel (4.21 mm2/s) is obtained. The simi-
lar study has been carried out by Tesfa et al. [16] using
corn oil, rapeseed oil and waste oil as the reaction feed-
stock. Their findings report revealed that the kinematic
viscosity of biodiesel is in the range of 3.55 - 5.48
mm2/s.
3.3. Study on Biodiesel Density
Density of biodiesel is one of specified quality parame-
ters which closely relates to the kinematic viscosity and
affects the engine performance. More viscous of bio-
diesel, higher the density of biodiesel is produced. The
density of biodiesel depends on the composition of fatty
acid compounds, as Tat and Gerpen [17] reported that
densities of biodiesel will vary with the fatty acid com-
position and their purity. Thus, it leads to a problem for
engine combustion which results in coking and trumpet
formation on the injectors, carbon deposits, oil ring
sticking, thickening and gelling of the lubricating oil [18].
In present study, the correlation between density and rpm
is investigated. From Figure 4, it can be seen that the
change of biodiesel density at every rpm is significant.
However, between 400 to 450 rpm (6.7 - 7.5 Hz), there is
not any major change of density for all reaction times.
On the other hand, at 300 rpm, especially for 30 min of
reaction time, the density of biodiesel is almost close to
the density of feedstock. This condition shows that the
reaction is not happened completely due to the time con-
straint.
Many previous works have been done by other re-
searchers on the biodiesel density [19]. But, their find-
Figure 4. Effect of rpm on density.
ings showed that the density change is linier with the
increase of pressure and inversely to the decrease of
temperature. The similar study also has been performed
by Alptekin and Canakci [12] which obtained that the
density of biodiesel is between methanol and fatty acid
densities.
3.4. Study of Flash Point
The aim of flash point analysis is to identify the tem-
perature degree of oil to be flammable with air. It is only
one of properties which must be considered in assessing
the overall flammability hazard of a material [20]. This
analysis is very important for the fuel transportation and
storage purposes.
The flash point of biodiesel corresponds to both the
percentage amount of hydrocarbon saturated compounds
and the residual of alcohol. As Jorge et al. [21] reported
the high sensitivity of the flash point with respect to the
residual alcohol content of the biodiesel is very clear.
This study is performed to investigate the effect of vis-
cosity on the flash point of biodiesel. The correlation of
viscosity with flash point of biodiesel can be explained
by using Figure 5. The results of observation (Figure 5)
showed that the flash point increases considerably with
enhance the viscosity. The bond appears to be linier. It
means that higher the percentage of saturated hydrocar-
bon compounds, lower the flash point of biodiesel. In
terms of safety, the lowest the flash point, a higher cost is
necessary for storage system. In this work, a moderate
flash point is obtained on the acceptable value of bio-
diesel viscosity as indicated in Table 2. The similar work
has been conducted by Mejía et al. [22], which used the
lending of vegetable oil biodiesel with fossil based die- b
Copyright © 2013 SciRes. SGRE
Waste Frying Oils-Based Biodiesel: Process and Fuel Properties
Copyright © 2013 SciRes. SGRE
285
Table 2. Physicochemical properties of waste frying oils based-biodiesel (ASTM D 6751).
Parameters Unit Method Values Limitation*
Density (15˚C) kg/m3 ASTM D 40 867 -
Kinematic viscosity (40˚C) mm2/s ASTM D 445 4.21 6.0 (max)
Water content % volume ASTM D 95-05 0.006 0.05 (max)
Calorific value MJ/kg ASTM D 240 39.85 -
Iodine value - PORIM 91 -
Pour point ˚C ASTM D 97 0 -
Flash point ˚C ASTM D 93 133 130 (min)
Total acid number mg KOH/g oil ASTM D 974 0.781 0.80 (max)
Cetane index - ASTM D 976 49 47 (min)
*[9].
Figure 5. Flash point of biodiesel over kinematic viscosity.
sel as the analyzed matter.
3.5. Analysis of Physicochemical
Characterization of Biodiesel
Since biodiesel as fuel for the engine application, it
should meet the standard quality of International specifi-
cations. In this work, some physic chemical properties of
waste frying oil-based biodiesel are analyzed using
ASTM method as shown in Table 2.
Most studies in biodiesel application have been fo-
cused on the blending with petroleum-based diesel. In
terms of emulsifying, biodiesel is also potentially prone
to hydrolytic degradation which is caused by the pres-
ence of water [23]. Biodiesel contaminated with water
can result in engine corrosion. To avoid this negative
effect, ASTM D 6751 set the maximum allowable con-
tent of 0.05% for water in biodiesel [24]. Anyway, in this
study, the value of water content of biodiesel is very low
compared to the minimum standard limitation. In terms
of TAN, Fan et al. [24] also reported that TAN is used as
a guide in the quality control as well as monitoring oil
degradation during storage period. Other physicochemi-
cal properties comply with the values of standards speci-
fication.
4. Conclusion
This research work, however, employs the optimum con-
dition for methanolysis process namely 1% wt of catalyst,
50 min of reaction time, and a hundred percent of stoi-
chiometric excess of methanol to oil, which is equal to
6:1 molar ratio to obtain the maximum percent conver-
sion of biodiesel production under various reaction tem-
peratures. The highest yield of biodiesel is 99%. The
similar condition is also achieved for the kinematic vis-
cosity, density, and flash point studies. The entire ana-
lyzed physicochemical properties of product showed that
the biodiesel properties favour the commercial require-
ments, in particular for diesel engine application.
5. Acknowledgements
The authors acknowledged all parties which contributed
in this research work, and a special thank for PT. Arun
NGL management which has allowed the authors for
using the lab facilities in conducting some analysis of
biodiesel properties.
REFERENCES
[1] A. Demirbas, “Biodiesel Fuels from Vegetable Oils via
Catalytic and Noncatalytic Supercritical Alcohol Trans-
esterifications and Other Methods: A Survey,” Energy
Conversion & Management, Vol. 44, No. 1, 2003, pp.
2093-2109. doi:10.1016/S0196-8904(02)00234-0
[2] S. Jain and M. P. Sharma, “Kinetics of Acid Base Cata-
lyzed Transesterification of Jatropha curcas Oil,” Biore-
Waste Frying Oils-Based Biodiesel: Process and Fuel Properties
286
source Technology, Vol. 101, No. 20, 2010, pp. 7701-
7706. doi:10.1016/j.biortech.2010.05.034
[3] L. C. Meher, V. S. Dharmagadda and S. N. Naik, “Opti-
mization of Alkali Catalyzed Transesterification of Pon-
gamia Pinnata for Production of Biodiesel,” Bioresource
Technology, Vol. 97, No. 12, 2006, pp. 1392-1397.
doi:10.1016/j.biortech.2005.07.003
[4] J. E. Lotero, Y. Liu, D. E. Lopez, K. Suwannakarn, D. A.
Bruce and J. G. Goodwin, “Synthesis of Biodiesel via
Acid Catalyst,” Industrial & Engineering Chemistry Re-
search, Vol. 44, No. 1, 2005, pp. 5353-5363.
doi:10.1021/ie049157g
[5] H. Noureddini, X. Gao and R. S. Philkana, “Immobilized
Pseudomonuas cepacia Lipase for Biodiesel Fuel Produc-
tion from Soybean Oil,” Bioresource Technology, Vol. 96,
No. 7, 2005, pp. 769-777.
doi:10.1016/j.biortech.2004.05.029
[6] M. M. Soumanou and U.T. Bornscheuer, “Improvement
in Lipase Catalyzed Synthesis of Fatty Acid Methyl Es-
ters from Sunflower Oil,” Enzyme and Microbial Tech-
nology, Vol. 33, No. 1, 2003, pp. 97-103.
doi:10.1016/S0141-0229(03)00090-5
[7] G. Madras, C. Kolluru and J. Kumar, “Synthesis of Bio-
diesel in Supercritical Fluids,” Fuel, Vol. 83, No.1, 2004,
pp. 2029-2033. doi:10.1016/j.fuel.2004.03.014
[8] M. Berrios, M. A. Martín, A. F. Chica and A. Martín,
“Study of Esterification and Transesterification in Bio-
diesel Production from Used Frying Oils in a Closed Sys-
tem,” Chemical Engineering Journal, Vol. 160, No. 2,
2010, pp. 473-479. doi:10.1016/j.cej.2010.03.050
[9] G. Knothe, J. V. Gerpen and J. Krahl, “The Biodiesel Hand
Book,” AOCS Press, Urbana, 2005.
doi:10.1201/9781439822357
[10] Y. Wang, S. Ou, P. Liu and Z. Zhang, “Preparation of Bio-
diesel from Waste Cooking Oil via Two-Step Catalyzed
Process,” Energy Conservation and Management, Vol. 48,
No. 1, 2007, pp. 184-188.
doi:10.1016/j.enconman.2006.04.016
[11] Y. Zhang, M. A. Dubé, D. D. McLean and M. Kates,
“Biodiesel Production from Waste Cooking Oil: 1. Proc-
ess Design and Technological Assessment,” Bioresource
Technology, Vol. 89, No. 1, 2003, pp. 1-16.
doi:10.1016/S0960-8524(03)00040-3
[12] E. Alptekin and M. Canakci, “Determination of the Den-
sity and the Viscosities of Biodiesel-Diesel Fuel Blend,”
Renewable Energy, Vol. 33, No. 12, 2008, pp. 2623-2630.
doi:10.1016/j.renene.2008.02.020
[13] P. V. Bhale, N. V. Deshpande and S. B. Thombre, “Im-
proving the Low Temperature Properties of Biodiesel Fuel,”
Renewable Energy, Vol. 34, No. 3, 2009, pp. 794-800.
doi:10.1016/j.renene.2008.04.037
[14] J. B. Heywood, “Internal Combustion Engine Fundamen-
tals,” McGraw-Hill, New York, 1988.
[15] Coulson and J. Richardson, “Particle Technology and Se-
paration Process,” Butterworth Heinemann Press, London,
2002.
[16] B. Tesfa, R. Mishra, F. Gu and N. Powles, “Prediction
Models for Density and Viscosity of Biodiesel and Their
Effects on Fuel Supply System in CI Engines,” Renew-
able Energy, Vol. 35, No. 12, 2010, pp. 2752-2760.
doi:10.1016/j.renene.2010.04.026
[17] M. E. Tat and J. V. Gerpen, “The Specific Gravity of
Biodiesel and Its Blends with Diesel Fuels,” Journal of
the American Oil Chemists Society, Vol. 77, No. 2, 2000,
pp. 115-119. doi:10.1007/s11746-000-0019-3
[18] F. Ma, L. D. Clements and M. A. Hanna, “The Effect of
Mixing on Transesterification of Beef Tallow,” Biore-
source Technology, Vol. 69, No. 3, 1999, pp. 289-293.
doi:10.1016/S0960-8524(98)00184-9
[19] A. B. Chhetri and K. C. Watts, “Densities of Canola, Ja-
tropha and Soapnut Biodiesel at Elevated Temperatures
and Pressures,” Fuel, Vol. 99, No. 1, 2012, pp. 210-216.
doi:10.1016/j.fuel.2012.04.030
[20] ASTM D93-02a, “Standard Test Methods for Flash Point
by Pensky-Marten Closed Cup Tester,” 2003, pp. 1-6.
[21] H. F. B. Jorge, L. C .S. Eva, B. C. Lilia and T. Matthieu,
“Determining the Residual Alcohol in Biodiesel through
Its Flash Point: Short Communication,” Fuel, Vol. 90, No.
2, 2011, pp. 905-907. doi:10.1016/j.fuel.2010.10.020
[22] J. D. Mejía, N. Salgado and C. E. Orrego, “Effect of
Blends of Diesel and Palm-Castor Biodiesels on Viscosity,
Cloud Point and Flash Point,” Industrial Crops and Prod-
ucts, Vol. 43, No. 1, 2013, pp. 791-797.
doi:10.1016/j.indcrop.2012.08.026
[23] P. Bondioli, A. Gasparoli, A. Lanzani, E. Fedeli, S. Ve-
ronese and M. Sala, “Storage Stability of Biodiesel,” Jour-
nal of the American Oil Chemists Society, Vol. 72, No. 6,
1995, pp. 699-702. doi:10.1007/BF02635658
[24] X. Fan, R. Burton and G. Austic, “Preparation and Char-
acterization of Biodiesel Produced from Recycled Canola
Oil,” The Open Fuels & Energy Science Journal, Vol. 2,
No. 1, 2009, pp. 113-118.
doi:10.2174/1876973X00902010113
Copyright © 2013 SciRes. SGRE