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Evaluation of biodiesel from Canarium ovatum (pili) pulp oil and Psophocarpus
tetragonolobus (winged bean) seed oil
Article in Philippine Agricultural Scientist · September 2007
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THE
PHILIPPINE
AGRICULTURAL
Biodiesel
from Pili Pulp
Oil and WingedSCIENTIST
Bean Oil
Vol. 90 No. 3, 215-221
September 2007
0031-7454
J. P. G. BicolISSN
and L.
F. Razon
Evaluation of Biodiesel from Canarium ovatum (Pili) Pulp Oil and
Psophocarpus tetragonolobus (Winged Bean) Seed Oil
John Paul G. Bicol and Luis F. Razon*
Portion of the M. S. thesis of the senior author. Funded by a grant from the University Research Coordination Office of De
La Salle University (DLSU) and the DLSU Science Foundation.
Department of Chemical Engineering, De La Salle University, 2401 Taft Avenue, Manila, Philippines
*Author for correspondence; e-mail: razonl@dlsu.edu.ph
Biodiesel, or fatty acid methyl esters (FAME) derived from triglycerides of oils of vegetable or animal
origin, is an attractive alternative fuel because of its low ecological impact and ease of manufacture.
However, some concerns remain about the cost and availability of feedstocks. Studies were conducted on biodiesel derived from two novel sources of oil: the fruit pulp of Canarium ovatum (pili) and
the seed of Psophocarpus tetragonolobus (winged bean). Oil was extracted from pili pulp and winged
bean seeds using hexane. The pili pulp oil and the winged bean oil were found to have a free fatty acid
content of 4.0% and 1.0%, respectively. Thus, a combination of acid-catalyzed esterification and basecatalyzed transesterification was necessary to convert the oils to FAME. Pili pulp FAME was found to
have a kinematic viscosity of 4.44 mm2s-1, a density of 0.887 g mL-1, cloud point of 7 oC, flash point of 155
oC, free glycerol of 0.01%, total glycerol of 0.06%, acid value of 0.31 mg KOH•g-1, sulfated ash of 0.001%,
sulfur of 0.02% and an iodine value of 69 g I2 100g-1. Winged bean FAME was found to have a kinematic
viscosity of 4.93 mm2s-1, density of 0.879 g mL-1, cloud point of 29 oC, flash point greater than 160 oC,
free glycerol of 0.02%, total glycerol of 0.07%, acid value of 0.26 mg KOH g-1, sulfated ash of 0.001%,
sulfur of 0.02% and an iodine value of 82 gI2 100g-1. The FAME were found to comply with key standards
(ASTM D6751-07, EN14214 and PNS2020:2003) except for the kinematic viscosity of the FAME from
winged bean, which was above the maximum limit for the Philippine standard (i. e., PNS2020:2003).
Key Words: biodiesel, Canarium ovatum, fatty acid methyl esters, feedstock, pili, Psophocarpus tetragonolobus, sigarilyas,
winged bean
Abbreviations: AOAC – Association of Official Agricultural Chemists, AOCS – American Oil Chemists Society, AR –
analytical reagent, ASTM – American Society for Testing Materials, CME – coconut methyl esters, CN – cetane number,
FAME – fatty acid methyl esters, FFA – free fatty acid, IV – iodine value, PNS – Philippine National Standard, SN –
saponification number
INTRODUCTION
Biodiesel, defined as fatty acid methyl esters (FAME) derived from oils of vegetable or animal origin, has attracted
interest as an alternative to petroleum-derived diesel fuel
(“petrodiesel”). It is biodegradable, renewable, non-toxic
and carbon-neutral. Compared to other alternative fuels, it
is easy to manufacture and requires only small changes in
the distribution infrastructure. In blends with petrodiesel,
it can be used in unmodified present-day diesel engines.
Despite these advantages, there are still some concerns over the widespread use of biodiesel. Most of the
present feedstocks are also food oils. Hence, there are le-
gitimate concerns about the impact on vegetable oil prices.
Already, a rise in vegetable oil prices has been observed
and the usual reason given is the use of oils for biodiesel
(Anonymous 2007). Hardly a day goes by without a new
biodiesel plant being announced somewhere in the world.
Availability is another concern. A simple comparison
of coconut oil production and demand for diesel fuel shows
that coconut oil production can only fill a small fraction of
the diesel requirements (Tan et al. 2004).
Jatropha curcas (locally known as “tuba-tuba”) has
been widely promoted as a possible alternative to food oils
(Foidl et al. 1996; Gubitz et al. 1999). Indeed, it offers the
advantage that it can be grown on marginal lands. How-
The Philippine Agricultural Scientist Vol. 90 No. 3 (September 2007)
215
Biodiesel from Pili Pulp Oil and Winged Bean Oil
J. P. G. Bicol and L. F. Razon
ever, both the oil and the seed cake are toxic (MartinezHerrera et al. 2006). A large spill or a bad poisoning incident
could easily turn public opinion against jatropha.
A prudent course of action would be to develop other
possible sources of feedstocks. Indeed, researchers have
tried a wide variety of plant oils (Rahman and Raherman
2004; Bouaid et al. 2005; Encinar et al. 1999; Ghadge and
Raheman 2006; Ajue and Obika 2000; Zullaikah et al. 2005;
Ramadhas et al. 2005; Antolin et al. 2002; Usta 2005; Karmee
and Chadhu 2005; Oluwaniyi and Ibeyimi 2003), animal fats
(Zheng and Hanna 1996; Reyes and Sepulveda 2006) and
even marine algae (Miao and Wu 2006; Chisti 2007). This
paper describes tests of biodiesel from two new sources of
oil: the mesocarp (fruit pulp) of Canarium ovatum (“pili”)
and the seed of Psophocarpus tetragonolobus (“winged
bean”, Philippine name: “sigarilyas”).
Winged bean was very widely studied in the 1980s,
being hailed as the “soybean of the tropics”. The primary
attraction to the winged bean is its protein content (30–
42%) and yield (2–5 tons per hectare) (De la Peña et al.
1981). Modest compared to that of coconut, the oil content
of winged bean is similar to that of soybean. Moreover,
winged bean oil, though edible, is not very highly valued
as a food because of its high behenic acid content. On the
other hand, the fatty acid profile of its oil seems to indicate
that it may yield biodiesel of acceptable quality. This will
be discussed further in the next section. Since the primary
use of winged bean is its protein, an additional use for its
oil could make cultivation more economically attractive.
Another feedstock that may be studied is the oil from
the mesocarp or the fibrous middle layer of the pili fruit.
The pulp is 33.6% oil, by weight (Coronel 1996). While the
kernel (commonly called the “nut”) is also a very rich source
of oil, it is already highly prized as an ingredient in confections, cakes and ice cream. On the other hand, the pulp
(which makes up 64.5% of the weight of the fruit) is usually
discarded (Coronel 1996). If the pulp can be used as a source
of biodiesel feedstock, a waste stream will have been eliminated.
In this paper, key physicochemical fuel properties of
biodiesel derived from winged bean seed oil and pili pulp
oil are determined and compared to biodiesel standards
and predictions from empirical equations. Some observations are also made on the steps necessary to convert the
oil to biodiesel.
MATERIALS AND METHODS
Materials
Pili pulp was purchased from Leslie Pili Products, Sorsogon
City, Sorsogon. The separation of pili pulp (depulping)
was performed by soaking the pili fruits in hot water for
about 15 min. Winged bean seeds were purchased from
Green World Agri-Farm Center, a supplier of seeds in
Malate, Manila. Bioactiv® brand coconut methyl esters
(CME) was purchased from a UniOil gas station in Makati
City.
Analytical reagent (AR) grade hexanes were used for
oil extraction from the pulp and the seeds. AR grade methanol, sulfuric acid and sodium hydroxide were used for the
esterification and transesterification reactions.
Preliminary Calculations
Literature values of the fatty acid profiles of pili pulp oil
and winged bean oil (Table 1) were used to calculate key
properties of FAME derived from these two oils. The key
properties computed were the cetane number, saponification value, iodine value and the viscosity.
Cetane number was estimated with the following equation (Krisnangkura 1986):
CN = 46.3 +
5458
– 0.225 x IV
SN
(1)
IV, the iodine value, can be computed from the fatty
acid profile via the following equation (Kalayasiri et al.
1996):
n
IV = Σ 254Dixi
(2)
i=1
M
i
where Di, xi and Mi are, respectively, the number of double
bonds, mass fraction and molecular weight of the ith fatty
acid. Similarly, SN, the saponification number, may be computed through the following equation (Kalayasiri et al.
1996):
n
SN =Σ 560xi
(3)
i=1
Mi
Equation (1) has been very popular, having been used
in at least six other studies (Encinar et al. 1999; Kalayasiri
et al. 1996; Azam et al. 2005; Karaosmanoglu et al. 2000;
Machacam et al. 2001; Tomasevic and Siler-Marinkovic
2003). However, only three data points were used to obtain
Equation (1). Hence, any numbers obtained from it should
be treated as mere rough estimates.
Table 1. Fatty acid profile of pili pulp oil and winged bean seed oil from literature (wt %).
Source
C14:0 C16:0 C16:1 C18:0 C18:1 C18:2 C18:3 C20:0 C20:1 C22:0 C24:0
Pili pulp
0.10
Winged bean
216
23.90 4.70
10.90
2.6
4.5
60.80 6.60 0.8
37.10 19.00
0.20
0.30
3.60 18.50
4.20
Reference
Pham (2004)
Homma et al. (1983)
The Philippine Agricultural Scientist Vol. 90 No. 3 (September 2007)
Biodiesel from Pili Pulp Oil and Winged Bean Oil
J. P. G. Bicol and L. F. Razon
The viscosity of the FAME (µm) was estimated using
an equation by Allen et al. (1999)
n
ln µm = Σ xi ln µi
i=1
(4)
where µi is the viscosity of fatty acid i and xi is the mass
fraction of the ith fatty acid. This equation may be considered reliable as its authors showed that it is accurate up to
within ±2%.
The results from these calculations were used to determine whether pili pulp oil and winged bean oil are potentially suitable feedstocks for use in biodiesel production.
Oil Extraction and Purification
Mechanical pressing of the seeds and pulp was attempted
but the amount of oil was very small. Therefore, oil extraction was carried out using hexane. The solvent was mixed
for at least 12 h at a 1:1 by weight ratio and was separated
in a rotary evaporator. Separation was performed at a maximum temperature of 80 °C.
Degumming was performed for the oil obtained from
winged bean due to the presence of solids believed to be
phospholipids or gums. Degumming was performed by
adding 2% by volume of distilled water and agitating for 30
min at 70 °C. The hydrated gums were removed by passing
the oils through a filter paper. Two successive degumming
steps were sufficient to remove all visible gums present in
the solvent extracted oil.
Oil Esterification and Transesterification
The free fatty acid content was obtained using Method Ca
5a-40 of the American Oil Chemists Society (AOCS). Both
oils were found to have a free fatty acid content greater
than 0.5%. Hence, an acid-catalyzed esterification reaction
was done to reduce the free fatty acid content. A methanolto-oil ratio of 40:1 and 10 wt% H2SO4 were used so that the
free fatty acid content could be reduced below 0.5% in one
step. The esterification reaction was conducted in a round-
bottom flask with a magnetic stirrer for 1 h at 60 °C. If a
lower methanol:oil ratio of 20:1 and a lower amount of H2SO4
(5 wt %) were used, four reaction steps were necessary to
reduce free fatty acid content to below 0.5%. After the
esterification step, the FAME-oil mixture was separated
from the methanol-water mixture using a separatory funnel. The moisture from the FAME-oil mixture was further
removed using a procedure described in Van Gerpen et al.
(2004), in which the procedure is attributed to Keim (1945).
Using this procedure, the FAME-oil mixture was dried by
heating to 60 °C for 15 min and then allowed to settle for 24
h. After settling, a maximum of 90% of the bottom layer was
taken and used as feed for the transesterification reaction.
A 6:1 methanol-to-oil molar ratio and 1% sodium hydroxide
by weight were used to perform the transesterification reaction in a round-bottom flask. The transesterification was
done at 60 °C for 1 h. The resulting mixture was allowed to
separate in a separatory funnel for at least 24 h. The top
layer, which consists of the FAME, was washed with distilled water.
Biodiesel Fuel Testing
The tests performed on the FAME, the methods used and
the laboratories that did the testing are summarized in Table
2. Because the batch size was small (400 mL), the tests on
the FAME were performed on a composite of four batches
of pili pulp oil and five batches of winged bean seed oil.
Unfortunately, due to cost considerations and the large
sample size required, cetane number testing was not possible.
RESULTS AND DISCUSSION
The results from applying equations (1)-(4) to these fatty
acid profiles are shown in Table 3 along with the relevant
standards from the European Union (EN14214), the American Society for Testing Materials (ASTM D6751-07) and
Table 2. Tests, methods and laboratories used for FAME testing.
Test
Method Used
Laboratory
Density
Free glycerol
Total glycerol
Acid value (AV)
Kinematic viscosity
Flash point
Sulfur
Sulfated ash
Cloud point
Iodine value
ASTM D1298
AOCS Ca14-56
AOCS Ca14-56
ASTM D974
ASTM D445
ASTM D93
ASTM D4294
ASTM D874
ASTM D2500
AOAC 921.158 (Ch. 41)
De La Salle University
De La Salle Univeristy
De La Salle University
De La Salle University
Chevron, Philippines, Inc.
Chevron, Philippines, Inc.
Department of Energy
Department of Energy
Department of Energy
First Analytical Services Technical Cooperative
The Philippine Agricultural Scientist Vol. 90 No. 3 (September 2007)
217
Biodiesel from Pili Pulp Oil and Winged Bean Oil
J. P. G. Bicol and L. F. Razon
Table 3. Predicted FAME properties from fatty acid profiles compared with the standards.
Kinematic
Iodine
Cetane
Viscosity,
Value, IV,
Number
40 °C
g I2.(100 g)-1
from
2
-1
from
Eq. (1)
mm sec
from Eq. (4)
Eq. (2)
Pili pulp
4.33
Winged bean seed
4.46
ASTM D6751-07 1.9–6.0
EN14214
3.5–5.0
PNS2020:2003
2.0–4.5
66
87
120 max
-
59
55
47 min
51 min
42 min
FAME – fatty acid methyl esters
the Philippine National Standard (PNS2020:2003). Table 3
shows that, for the parameters that can be computed via
these empirical equations, winged bean biodiesel and pili
biodiesel may be expected to be acceptable to these three
standards.
Physicochemical Properties of Oil
Table 4 shows the fat content and free fatty acid content of
the raw material and a comparison with the literature val-
ues. While the winged bean seed fat content is similar to
the literature value, the pili pulp fat content is considerably
lower. This may be due to the manner by which the pulp
was separated from the kernel – by soaking in hot water.
The drastic reduction in the expected oil content of pili
pulp is a potentially important issue if the material is to be
used commercially.
The free fatty acid content obtained from actual testing is similar to that reported in the literature (De la Peña et
al. 1981; PCARRD 1997). Based on the free fatty acid content, it was determined that a preliminary acid-catalyzed
esterification step was necessary. This was carried out in
one step as described in the Methodology.
Biodiesel Fuel and By-product Testing
The fuel test results are summarized in Table 5. Also included are tests performed on a commercial sample of coconut methyl esters (CME) (Bioactiv® brand, Chemrez
Corp.). It can be seen that the pili FAME and the winged
bean FAME complied with all standards with one exception. Specifically, the viscosity of the winged bean FAME
exceeded the PNS2020:2003 standard although it complied
with both the ASTM D6751-07 and the EN14214 standards.
This may be because the standards agencies are using
Table 4. Fat content of feedstock and free fatty acid content of oil.
Fat Content (%, Dry Basis)
Free Fatty Acid Content of Oil (%)
Source
Pili pulp
Winged bean seed
Actual
Literature
Actual
Literature
8.0
13.1
33.6 (PCARRD 1997)
15-20 (De la Peña et al. 1981)
4.0
1.0
4.2 (PCARRD 1997)
2.3 (De la Peña et al. 1981)
Table 5. Summary of fuel property results testing.
Material
Specifications
Property
Kinematic viscosity (mm2s-1)
Density (g mL-1)
Cloud point (°C)
Flash point (°C)
Free glycerol (%)
Total glycerol (%)
Acid value (mg KOH.g-1 )
Sulfated ash (%)
Sulfur (%)
Iodine value (g I2.(100g)-1)
Pili
ME
Winged
Bean ME
CME
PNS
ASTM
EN
4.44
0.887
7
155
0.01
0.06
0.31
0.001
0.02
69
4.93
0.879
29
160+
0.02
0.07
0.26
0.001
0.02
82
2.61
0.870
-1
106.5
0.01
0.11
0.20
0.001
0.02
10
2.0 - 4.5
100 min
0.02 max
0.24 max
0.5 max
0.020 max
0.05 max
-
1.9 - 6.0
130 min
0.02 max
0.24 max
0.8 max
0.020 max
0.15 max
-
3.5 - 5.0
0.86 - 0.90
120 min
0.02 max
0.25 max
0.5 max
0.020 max
0.10 max
120 max
ASTM – American Society for Testing Materials, CME – coconut methyl esters, EN – European Union, ME – methyl ester, PNS
– Philippine National Standard
218
The Philippine Agricultural Scientist Vol. 90 No. 3 (September 2007)
Biodiesel from Pili Pulp Oil and Winged Bean Oil
J. P. G. Bicol and L. F. Razon
their “experience base”, that is, standards are based on
typical results obtained from fuels that are known to the
standards agency. Indeed, it can be seen that CME would
not pass EN14214 because of its very low viscosity though
it is well known to be an adequate fuel in the Philippines.
The high viscosity standard in EN14214 may be because
the European Standards Agency has probably not had
enough experience with lower viscosity FAME to conclude
that they can indeed be used in diesel engines without any
harmful effects. Similarly, the Philippine standards are also
probably set to a lower viscosity because the Philippine
experience is based primarily on coconut.
The repeatability of the tests for kinematic viscosity,
density, free glycerol, total glycerol, acid value and flash
point were all found to be within the repeatability specifications of the tests used. Other properties including sulfur, sulfated ash and cloud point were not included since
these tests were contracted to other laboratories; the latter
did not report any trial data.
Also worthy of discussion is the cloud point. The
cloud point of the winged bean FAME is high and is already close to room temperature. Hence, some “winterization” may be necessary if the fuel is to be used in a pure
state or a large percentage blend although some loss of
material may be the penalty for winterization (Knothe 2005).
Some observations may also be reported on the color
of the products. The pili pulp FAME is greenish yellow
while the winged bean FAME is yellowish red. These probably originate from the natural pigments of the raw materials. Similarly, the glycerol from pili pulp has a black or dark
gray tint while the glycerol from winged bean is light yellow. These observations are relevant because glycerol is
an important by-product of the biodiesel process and a
significant price premium is paid by end users for colorless
glycerine.
Comparison of Predicted and Actual Results
A comparison of the model prediction versus actual values
for iodine value and kinematic viscosity is shown in Table
6. While not strictly in agreement, the percentage errors
are reasonable. The rather large error for the kinematic viscosity of the winged bean FAME can be explained by the
fact that the viscosity data for the longer chain fatty acids
such as behenic acid are not available because they are
solid at room temperature. Hence, the viscosity of these
fatty acids was estimated using the viscosity of the closest related fatty acid.
CONCLUSION AND RECOMMENDATIONS
FAME derived from both plants complied with all standards with the exception that the winged bean FAME did
not comply with the PNS2020:2003 kinematic viscosity standard. Since the winged bean FAME complied with the
ASTM D6751-07 and EN14214, no actual problems are expected from the use of winged bean FAME in diesel engines. Comparisons of actual measurements with values
predicted from empirical equations have been shown to be
within reasonable agreement.
The authors recommend that economic feasibility studies be conducted on these materials now that it has been
demonstrated that adequate FAME can be obtained from
these two plants. The production volume of the pili nut
has shown a steadily upward trend with a peak production
of 5402 metric tons of nuts recorded in 2005 (BAS 2007).
Using the literature value that the fruit contains 64.5% pulp
and 35.5% nut (Coronel 1996), this figure translates to about
9300 MT of pulp and 3500 MT of oil. This is a modest
amount compared to total diesel demand but this volume
may be enough to sustain a small facility because the production of pili is concentrated in the Bicol Region and
Eastern Visayas.
The total production of the immature pods of winged
bean for the past 10 yr has remained roughly constant at
about 1800 MT per year (BAS 2007). However, the figure
reflects only the use of the plant as a vegetable. Winged
bean has a potential yield of about 400–1000 kg of oil per
hectare (De la Peña et al. 1981). This would rank it on more
or less the same level as soybean and rapeseed but lower
Table 6. Comparison of predicted iodine value and viscosity with the actual value.
Iodine Value
(g I2 .(100g)-1)
Viscosity
(mm2s-1)
Material
Pili ME
Winged bean ME
Predicted
(Eq. 1)
Actual
Testing
%
Error
Predicted
(Eq. 4)
Actual
Testing
%
Error
66
87
69
82
4.3
6.1
4.33
4.46
4.44
4.93
2.5
9.5
ME – methyl ester
The Philippine Agricultural Scientist Vol. 90 No. 3 (September 2007)
219
Biodiesel from Pili Pulp Oil and Winged Bean Oil
J. P. G. Bicol and L. F. Razon
than coconut and palm. The economic feasibility of winged
bean FAME will hinge on both the feasibility of the use of
its protein for foods and feed and the use of the oil for fuel.
As before, the trellis requirement for winged bean works
against the compatibility of this plant with large-scale
mechanized agriculture.
Further studies need to be conducted on the winged
bean and pili FAME. Engine and vehicle testing also needs
to be completed to determine directly if any problems may
arise from the use of these two unusual feedstocks.
ACKNOWLEDGMENTS
The authors would like to thank the University Research
Coordination Office (URCO) of De La Salle University
(DLSU) and the DLSU Science Foundation for funding this
project. Dr. Laura Pham of the National Institute of Molecular Biology and Biotechnology of the University of the
Philippines Los Baños informed us of the possibility of
using pili pulp oil as biodiesel feedstock and provided invaluable advice through the course of this project.
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