BIODIESEL AS AN ALTERNATIVE FUEL LEADING TO CLEANER
ENVIRONMENT
CLEOTILDE A. BULAN
Chemicals and Mineral Division-Industrial Technology Development Institute
Department of Science and Technology, DOST Compound., Bicutan, Taguig, Metro Manila, Philippines
Abstract
Vegetable oils and their derivatives, particularly the methyl esters, commonly referred to as “biodiesel” are the
leading candidates as alternative fuel ready for introduction to the growing population who clamor for a
cleaner air and cleaner environment. They are technically competitive with and offer technical advantages
compared to petroleum-diesel fuel. Aside from being renewable and biodegradable, biodiesel, reduces most
emissions while engine performance and fuel economy are nearly the same as the conventional fuel.
Introduction
The use of vegetable oils as diesel fuel is nearly as old as the diesel engine itself. The inventor of the
diesel engine, Rudolf Diesel, reportedly used groundnut (peanut) oil as a fuel for demonstration purposes in
1900 . Fuel and energy crisis and the concern of society for depleting world’s non-renewable resources initiates
various sectors to look for alternative fuels. One of the most promising fuel alternative is the vegetable oils and
their derivatives. Hundreds of scientific articles and research activities from around the world were printed and
recorded. Oils from coconut, soy bean, sunflower, safflower, peanut, linseed and palm were used depending on
what country they grow abundantly. In the Philippines alone, research activities on the use of vegetable oils as
fuel substitute have already been done as early as the 1970s using coconut oil. In the United States, the
primary interest as biodiesel source is soy bean oil while many European countries are concerned with rape
seed oil and countries with tropical climate prefer to utilize coconut oil or palm oil.. Furthermore, other sources
of biodiesel studied include animal fat and used frying oil.
Several problems encountered cause delay in the widespread use of biodiesel. First is economics and
second is the properties of biodiesel. Use of neat vegetable oils cause injector coking, engine deposits, ring
sticking and thickening of the engine lubricant. To overcome this problem, various modifications of vegetable
oils were suggested such as by transesterification, micro-emulsion formation and the use of viscosity reducers.
Among these, transesterification was considered as the most suitable modification because technical properties
of esters are nearly similar to diesel.
What is Biodiesel?
The term Biodiesel, in general, refers to neat vegetable oils used as diesel fuel as well as neat methyl esters
prepared from vegetable oils or animal fats and even blends of conventional diesel fuel with vegetable oils or
methyl esters. Due to problems encountered in the use of neat vegetable oil, Biodiesel is now referred to as the
mono alkyl esters of long chain fatty acids derived from vegetable oils for use in compression ignition (diesel)
engines. Methyl ester is usually made from 80-90% vegetable oil, 10-20% alcohol and 0.35-1.5% catalyst.
How to Make Biodiesel?
The process of making Biodiesel is called transesterification. It is the transformation of one type of an ester into
another type of ester. Transesterification chemically break the molecule of the raw renewable oil into methyl
ester with glycerol as a by-product. Most vegetable oil are triglycerides (TG). Chemically, trigylcerides are the
triacylglyceryl esters of various fatty acids with glycerol. About 20% of a vegetable oil molecule is glycerol.
During transesterification, glycerol is removed from the vegetable oil making the oil thick and reduce viscosity.
The most common derivative of triglycerides or fatty acids for fuels are the methyl esters. Methy esters are
formed by the transesterificion of the TG with methanol in the presence of a basic catalyst to give the methyl
ester and glyceryl (Fig. 1). Other alcohols have been used to generate esters like the ethyl, propyl and butyl
alcohol. Methanol, however, is the preferred alcohol because it produces a more stable biodiesel reaction, it is
less affected by water in the vegetable oil and the transesterification reaction is faster compared with other
alcohols.
CH2COOR
CHCOOR
CH2OH
+
3CH3OH
3CH3COOR
+
CH2COOR
Vegetable Oil
CHOH
CH2OH
(plus)
Methanol

(plus catalyst)
Biodiesel
(plus)
Glycerin
Fig.1 The Transesterification Reaction
A typical transesterification procedure follows. A weighed amount of oil is charged into a biodiesel reactor.
The catalyst is dissolved in alcohol in a small reactor by vigorous stirring and then added to the oil. Vigorous
stirring of the solution is continued for two hours. A successful reaction produces two liquid phases: the ester
found at the upper layer and the crude glycerol which is found in the lower layer. Phase separation can be
observed within 10 minutes after the stirring stopped and be completed from two to eight hours. After complete
settling the glycerol is drained. The catalyst (usually sodium hydroxide or potassium hydroxide) goes with the
glycerol. The ester layer is washed with water at the rate of 28 percent by volume of the oil with gentle agitation
several times until the washing is neutral to pH paper or the washing becomes clear. Washing can be a hot mild
salt solution or water containing Acetic acid, Tannic acid or Hydrochloric acid. This is used to lessen
emulsion formation due to presence of soap and to make separation of water and ester layer easier. After
gentle agitation the solution is allowed to settle. After settling, the aqueous solution is drained. For the final
washing, water alone is added at 28 percent by volume of oil. Gentle agitation followed and then the solution is
allowed to settle before draining the aqueous layer completely.
Why Use Biodiesel?
Biodiesel fuel is reliable, renewable, biodegradable and non-toxic. It is less harmful to the environment for it
contains practically no sulfur and substantially reduce emissions of unburned hydrocarbon (HC), carbon
monoxide, sulfates, polycyclic aromatic HC (PAH) and particulate matter. It has fuel properties comparable to
mineral diesel and because of great similarity, it can be mixed with mineral oil and used in standard diesel
engines with minor or no modifications at all. Biodiesel works well with new technologies such as catalysts
(which can reduce the soluble fraction of diesel particulates but not the solid carbon fraction), particulate traps
and exhaust gas re-circulation. It can be produced from any kind of oil both vegetable and animal source . Used
frying oil can also be used and , therefore, be a very promising alternative for waste treatment.
Being an agricultural product, all countries have the ability to produce and control this energy source which is
a situation very different to the crude oil business. It can strengthen economy by creating more jobs and create
independence from the imported depleting commodity, petroleum. It can also be used as a way of stimulating
and supporting agriculture.
Emissions, Engine Problem and Deposits.
Neat Vegetable Oils. Lots of works on the use of neat vegetable oils as fuel substitute have already been done
and reported. Their properties are competitive with conventional diesel fuel in some emission categories but
problems were also identified for other kinds of emissions. It was shown that poly-aromatic hydrocarbon (PAH)
emissions were lower for neat vegetable oils especially the alkylated PAHs which are common in the emission
of conventional diesel fuel (DF). Besides higher NOx levels, aldehydes are reported to present problems with
neat vegetable oils. Total aldehyde increased dramatically with vegetable oils and formaldehyde formation was
consistently higher than with DF. It was also reported that component triglycerides (TGs) in vegetable oil can
lead to formation of aromatics via acrolein (CH2=CH-CHO) from the glycerin moiety.
Most studies conducted report that for short-term trials, neat oils gave satisfactory engine performance and
power output are often equal to or even slightly better than conventional DF. However, vegetable oils cause
engine problems. Studies on sunflower oil, coconut and other oils as fuel noted coking of injector nozzles,
sticking piston rings, crankcase oil dilution, lubricating oil contamination and other problems. The causes of
these problems were attributed to the polymerization of TGs via their double bonds which leads to formation of
engine deposits as well as the low volatility and high viscosity with resulting poor atomization patterns.
Alkyl esters. Biodiesel emissions are substantially lower than petroleum diesel emissions. Compared to
gasoline, biodiesel produces no sulfur dioxide, no net carbon dioxide, up to 20 times less carbon monoxide, and
more free oxygen. Biodiesel has the following emission characteristics when compared to petroleum diesel fuel:

Reduction of net carbon dioxide (CO2) and sulfur dioxide (SO 2)emissions by 100%.

Reduction of soot emissions by 40-60%.

Reduction of carbon monoxide (CO) and hydrocarbon emissions by 10 - 50%.

Reduction of all polycyclic aromatic hydrocarbons (PAHs) and specifically the reduction of the following
Carcinogenic PAHs:
Reduction of phenanthren by 97%.
Reduction of benzofloroanthen by 56%.
Reduction of benzapyren by 71%.
Reduction of aldehydes and aromatic compounds by 13%.

Reduction or increase of nitrous oxide (Nox) emissions by 5-10% depending on the age of the vehicle
and the tuning of the engine.
Biodiesel Standard
To instill confidence in biodiesel users, engine manufacturers and other parties and to facilitate
commercialization of this product it is important to develop a reliable standards. Austria (ONORM C 1190) and
Germany (DIN V 51606) have established similar standards for neat biodiesel. In the United States, an ASTM
standard was suggested. Both standards contain specifications particular to biodiesel (for example, glycerol
quantitation) which are not given for conventional diesel fuel.
Use of biodiesel in the Philippines
In the Philippines, research and development activities in the use of neat vegetable oil, particularly, the coconut
oil and its methyl ester derivative started as early as the 1970s. Both the government and private institutions like
DOST, ITDI, PCA, NPC, PNOC-ERDC and PCRDF have initiated such studies on fuel application. Various
problems caused by the high viscosity and low volatility of coconut oil and the related problems associated with
its use as diesel fuel substitute like clogging of fuel lines, gum formation and thickening of lubricating oil, initiated
continuous effort to develop production of methyl ester, particularly, coconut methyl ester or CME.
Coconut methyl ester (CME) is an ester derivative of coconut oil with C 8 to C18 carbon chain. It has lubricity,
solvency and detergency characteristics and can be used as pure petroleum diesel fuel (PDF) substitute or as
blend with PDFin any proportion without any engine modification. Studies showed that use of CME result to
complete combustion of fuel, less pollution and more power delivered. The engines ran smoothly during actual
testing and does not need frequent maintenance cleaning for it also has cleaning property of the nozzle or
engine parts. Use of CME is found to be technically viable but the question on economics delayed the
commercialization and use of CME or biodiesel.
With the implementation of the Philippine Clean Air Act (RA 8749) in 1999, Philippine Coconut
Authority under the Department of Agriculture in collaboration with the Department of Energy (DOE),
Technological University of the Philippines (TUP) and the Metro Manila Development Authority conceptualized
and conducted a project on the use of CME as a petroleum-diesel fuel quality enhancer. Research
activities are still on-going to gather enough data to support the program and to answer the many questions
being raised by the transportation sectors and the PDF manufacturers. Aside from the Clean Air Act they were
also inspired by the previous studies showing that CME is a good, more environment-friendly alternative fuel
and by the intention to uplift the quality of life of coconut farmers. To address the economic issues, CME will
not be used as diesel fuel substitute but as an economically viable PDF quality enhancer to improve engine
performance and reduce air pollution. Initial results show that the use of 1% CME alone reduces smoke
emission as shown in Fig. 2. Illustration No.1 shows that because of its solvency it has cleaning effect to the
engine parts particularly the nozzles. After the testing of several PCA vehicles showed favorable results, the
1% CME-PDF blend are now being tried and used in several buses flying in Metro Manila . Results of
Dynamometer testing using a C-190 Isuzu diesel engine as shown in Figure 3 indicates an increase of 2.5% to
3.2% for CME blends in torque curve compared to Low Sulfur Diesel (LSD). Illustration No.2 showed the
decrease in the opacity readings between the buses using 1% CME blend and the one using pure PDF.
Opacity or "K" Reading (m-1)
2.5
2.32
2
1.5
1.24
1.03
1
0.81
0.43
0.5
0.35
0.24
0
0
200
1,400
3,900
5,033
15,663
16,928
Equivalent Diesel Particulate
(PPM)
Road Run Kilometer (Km)
450.00
400.00
386.67
350.00
300.00
250.00
206.67
171.67
200.00
135.00
150.00
71.67
100.00
58.33
50.00
40.00
0.00
0
200
1,400
3,900
5,033
15,663
16,928
Road Run Kilometer (Km)
Figure 1. Reduction of Smoke Emission after Blending Petroleum Diesel with 1% CME
After using 1% CME
After using 1% CME
Illustration No. 1. Effect of CME on the Engine
Before using CME
Before using CME
After using 1% CME
POWER TORQUE CURVE
TORQUE (kg-m)
LSD
10.80
1% CM E-13
10.60
10.40
10.20
1% CM E-15
10.00
5% CM E-15
2% CM E-13
2% CM E-15
5% CM E-13
9.80
9.60
9.40
9.20
9.00
8.80
1500
2000
2500
3000
3500
4000
4500
RPM
Fig. 3. Dynamometer Test Result On C-190 Isuzu Diesel Engine.
3
Opacity or "K" Reading (m-1)
2.65
2.5
with 1% CME
w/o CME
1.9
1.89
2
1.6
1.53
1.5
1.05
1
0.79
0.54
0.5
0.39
0.28
0.19
0.26
0
0
900
1800
2700
3600
4500
Distance Travelled (Km)
Illustration No. 2. California Buses Opacity Test Result
Biodiesel Standard
Pursuant to the intent of the Clean Air Act to develop and utilize cleaner alternative fuels, the Technical
Committee on Petroleum products and Additives of the Department of Energy (DOE/TCPPA) prepared a
Philippine Coconut Oil Biodiesel Product Standard and is adopted as the Philippine National Standard (PNS) for
Biodiesel by the Bureau of Product Standard (BPS) which the manufacturers should comply to ensure its
effectiveness when used either in its pure state or as a blend. The ASTM standard being used in the United
States was used as basis for this specification. Table 1 shows the prepared PNS specifications.
Critical key points on CME fuel quality include; Flash point whose limit is set at 100oC to ensure the removal
of excess methanol used during the manufacturing process. Presence of residual methanol even at small
amount reduces flash point. It can also affect fuel pumps, seals and can result to poor combustion, Sulfated Ash
ensures the removal of catalyst. High level of catalyst in the fuel can result in injector deposits or filter plugging,
Acid number limits to 0.5 maximum. Higher than the set limit may cause fuel system deposits and reduce the
life of fuel pumps and filters, and Free and Total Glycerin Number which measure the degree of conversion of oil
into ester. If the value is too high, fuel gumming and engine fouling will occur.
DOE/TCPPA also come up with conclusive inter-laboratory fuel test results (wherein the petroleum
laboratories participated) that 1%, 2% and 5% CME-PDF Blend (by volume basis) still conform to the PNS for
Diesel Fuel.
Table 1. PNS Specification for Biodiesel and the Test Method Used
Property
Flash point Pensky Martens oC, min.
Water & Sediments % vol. Max.
Kinematic viscosity @ 40oC, mm2/s
Sulfated ash % mass max.
Sulfur @ mass max.
Copper strip corrosion 3 hrs @ 50oC max.
Cetane number, min.
Cloud point, oC max.
Carbon residue,100% sample,% mass, max.
Acid number, mg KOH/g,max.
CME Limit
Test Method
100.0
0.050
2.0 – 4.5
0.020
0.050
PNS 613 / ASTM D 93
PNS 707 / ASTM D 2709
PNS 407 / ASTM D 445
PNS 2025 / ASTM D 874
PNS 504 / ASTM D 2622
PNS 1685 / ASTM D 5453
PNS 505 / ASTM D 4294
PNS 502 / ASTM D 1266
PNS 379 / ASTM D 130
PNS 653 / ASTM D 613
PNS 706 / ASTM D 2500
PNS 708 / ASTM D 4530
PNS 2024 / ASTM D 664
PNS 2026 / ASTM D 974
PNS 2022 / AOCS Ea6-51 (1989)a
PNS 2023 / AOCS Ca 14 -- 56
(1997)a
PNS 2028 / ASTM D 4951
PNS 2027 / ASTM D 1160
No. 3
42a
Report
0.050
0.50
Free glycerin, % mass, max.
Total glycerin, % mass, max.
0.02a
0.24a
Phosphorus,% mass,max.
Distillation AET 90% recovered oC, max.
a Transition standard
(Source:DOE/TCPPA)
0.001
360
Summary
Biodiesel (fatty acid alkyl ester) is a cleaner-burning diesel replacement fuel made from natural, renewable and
biodegradable sources. It is a stable diesel which performs reliably in all diesel engines without any modification,
is mixable with petroleum diesel fuel, easy to make and safe to handle. Biodiesel cuts emissions, reduce
particulates, unburned hydrocarbons, carbon monoxide and carbon dioxide. It is practically free from lead, sulfur
and halogens. Biodiesel, therefore, is a very promising alternative fuel that can lead to a cleaner environment.
Acknowledgement
The author gratefully acknowledge Engr. Roberto C. Ables of PCA for sharing their available data on
the application testing of biodiesel, Ms. Evelyn Reyes of DOE, Ms. Merle A. Villanueva, Ms. Marina Yao,
Ms. Annabelle V. Briones and the rest of Organic Chemicals Section staff of Chemicals and Mineral Division
for their support and assistance in the completion of this paper.
References:
Carandang, E. V., Ferrer, Ma. L. M., Red, V. P. 1991. Use of 100% Coconut Methyl Ester as Substitute for
Diesel. PJCS 16(1):22-25.
Arida, V. P., Atienza, A., Borlaza, F. C., Binlayo, D. L. 1981. Production and Development of a Diesel Fuel
Substitute from Coconut. PJCS 6(2) 10-20.
Tickell, J. 2000. From the Fryer to the Fuel Tank-The Complete Guide to Using Vegetable Oil as an Alternative
Fuel, 3rd Edition, Edited by Kaia Roman. Pp 29-38, 59-87. Tickell Energy Consulting, Tallahassee, F.L.
(Florida).
Knothe, G., Dunn, R. O., Bagby, M. O. Biodiesel: The use of Vegetable Oils and their Derivatives as Alternative
Diesel Fuels. Oil Chemical Research, National Center for Agricultural Utilization Research, Agricultural
Research Service, U.S. Department of Agriculture, Peoria, I L 61604.
BIOGRAPHY
The author, CLEOTILDE A. BULAN, is a Bachelor of Science in Chemistry graduate of
University of Santo Tomas. She is a Registered Chemist and worked as a Quality Control
Analyst for six (6) years at United Chemicals, Inc. Plant in Bauan, Batangas. At present, she
is a Senior Science Research Specialist of the Chemicals and Mineral Division of industrial
Technology Development Institute (ITDI), one of the Research and Development Institute of
the Department of Science and Technology (DOST). She is directly involve in the research
and development of different Fats and Oils locally available to produce chemical derivatives
for industry use. She attended and successfully completed an Individual Training Course in
Processing of Fats and Oils into Chemicals/Intermediate/Products and Formal Training on
various Scientific instruments at Miyoshi Oil & Fat., Ltd. and Shimadzu Corporation at Tokyo
and Kyoto, Japan, respectively, from November 1, 1990 to February 25, 1991. Some of her
published paper are the ‘Laboratory Synthesis of Alkyl Phosphate from Coco-Based
Chemicals’ and the ‘Production and Application Testing of Textile Auxiliaries from CocoBased Chemicals’.