The document summarizes research on biodiesel as an alternative fuel. It discusses how biodiesel is produced through transesterification of vegetable oils and fats. The properties of biodiesel are outlined and compared to fossil diesel. Experimental results are presented showing biodiesel blends and advanced injection timing can improve engine performance similar to diesel. However, higher carbon deposits and more frequent filter cleaning are issues. The document concludes biodiesel is a promising renewable alternative but requires further optimization.

1. 1
ABSTRACT
The rapidly increasing consumption of fossil fuel and petroleum products has been
a matter of concern for the many countries which imports more crude oil. Because
it causes huge foreign exchange out-go on the one hand and increasing exhaust
emission on the other. Therefore it is necessary for the development of renewable
energy sources.
Vegetable oils have become more attractive recently because of their
environmental benefits and it is made from renewable resources. Bio-diesel
commands crucial advantages such as technical feasibility of blending in any ratio
with petroleum diesel fuel, use of existing storage facility and infrastructure,
superiority from the environment and emission reduction angle, its capacity to
provide energy security to remote and rural areas and employment generation.
There are more than 350oil bearing crops identified, among which only sun flower,
sunflower, soybean, cottonseed, rapeseed, Jatropha curcas and peanut oils are
considered as potential alternative fuels for Diesel engines. So a particular crop
which is available in surplus within the country should be used to produce Bio-
diesel.
This paper reviews the extraction and properties of Bio-diesel, also the outcomes
of the research work done in different countries. Also efforts has been made to
includes the Bio-diesel scenario in India.

2. 2
1 INTRODUCTION
The world energy demand has, for the last two decades, witnessed uncertainties in
two dimensions. Firstly, the price of conventional fossil fuel is too high and has
added burden on the economy of the importing nations.
Fig 1.1 World Energy Consumption
Secondly, combustion of fossil fuels is the main culprit in increasing the global
carbon dioxide (CO2) level, a consequence of global warming. The scarcity and
depletion of conventional sources are also cases of concern and have prompted
research world-wide into alternative energy sources for internal combustion
engines.

3. 3
Fig 1.2 World Energy scenario
The fast growing population, rapid modernization and industrialization have
relentlessly increased the demand of energy in developing countries like India. The
current demand of energy in India is mostly met from non-renewable resources
such as natural gas and coal. Since these sources are non-renewable in nature, the
reserve will be depleted one day. In addition, the dependency on these fossil fuels,
which are largely been imported, has serious implications on economy and
environment. Fossil fuels are coming to the end, scientist say that up to 2040,all the
resources of fossil fuels will be finished. So for this reason scientist are focus their
view on the alternative renewable energy resource such as solar energy, biogas,
biodiesel, wind power, tidal energy etc.
Table:1.1 Two types energy sources

4. 4
Biofuels appear to be a potential alternative “greener” energy substitute for fossil
fuels [3]. It is renewable and available throughout the world. The idea of using
vegetable oils as fuel for diesel engines is not new [8]. Rudolph diesel used peanut
oil to fuel one of his engines at the Paris Exposition of 1900. The problem of using
neat vegetable oils in diesel engines relates to their high viscosity. The high
viscosity will lead to blockage of fuel lines, flters, high nozzle valve opening
pressures and poor atomization. One hundred percent vegetable oils cannot be used
safely in DI diesel engines. The problems of high fuel viscosity can be overcome
by using esters, blending and heating. Vegetable oils exhibit longer combustion
duration with moderate rates of pressure rise, unlike petroleum derived fuels.
The use of vegetable oils, such as palm, soya bean, sunflower, peanut, and olive
oil, as alternative fuels for diesel is being promoted in many countries [13].
Depending upon the climate and soil conditions, different countries are looking for
different types of vegetable oils as substitutes for diesel fuels. For example, soya
bean oil in the US, rapeseed and sunflower oils in Europe, palm oil in South-east
Asia (mainly Malaysia and Indonesia) and coconut oil in the Philippines are being
considered. Besides, some species of plants yielding non-edible oils, e.g. jatropha,
karanji and pongamia may play a significant role in providing resources. Both
these plants may be grown on a massive scale on agricultural/degraded/waste
lands, so that the chief resource may be available to produce biodiesel on „farm
scale‟.

5. 5
Fig: 1.3 Biofuels as alternative to Fossil fuels
This paper gives a review of biodiesel production, experimental investigation on
different vegetable oils, characterization, results obtained use of by bio-diesel are
briefed.

6. 6
2. Literature Review
2.1 What are biofuels?
Any hydrocarbon fuel that is produced from organic matter (living or once living
material) in a short period of time (days, weeks, or even months) is considered a
Biofuel.
Fig 2.1 Diff types of Biofuels
There are four chief of biofuels:
The 1st generation of biofuels comes from sugar, starch & vegetable fats that are
solely dependent on food-crops. It also can be sourced through animal fats.

7. 7
Fig2.2 Four chief of Biofuels
2.2 Biofuel versus Fossil Fuel
Fossil fuels are not renewable, which means they will run out at some point. As our
ability to pump fossil fuels from the ground diminishes, the available supply will
decrease, which will inevitably lead to an increase in price.
Biofuels can be looked upon as a way of energy security which stands as an
alternative of fossil fuels that are limited in availability. Today, the use of biofuels
has expanded throughout the globe.
2.3 Positives of Biofuels
• The energy content of biodiesel is about 90% that of petroleum diesel.
• The energy content of ethanol is about 50% that of gasoline.
• The energy content of butanol is about 80% that of gasoline.
• Biofuels burn cleaner than fossil fuels, resulting in fewer emissions of
greenhouse gases, particulate emissions, and substances that cause acid rain
such as sulfur.

8. 8
• Biodiesel is sulfur free.
• Biodiesel has fewer polycyclic aromatic hydrocarbons, which have been
linked to cancer.
• Additionally, biofuels are biodegradable, so if they do spill, less harm is
done compared to when fossil fuels spill.
2.4 Biodiesel:
Biodiesel is a famous biofuel in Europe Produced from oils or fats using trans-
esterification after mixing the biomass with methanol and sodium hydroxide.
An low-emissions, high lubricating alternative diesel fuel produced from veg.oil /
animal fats,Non-toxic, Biodegradable And can be combined at any level with
petroleum diesel to fuel diesel engines.
methanol and sodium hyrox
Produced after mixing the biomass with methanol and sodium hyroxide
Used for car diesel engine. PrProduced after mixing the biomass with methanol
and sodium hyroxide
Fig 2.3 Making of Biodiesel.
Inputs:
Fat/Vegetable Oil (“Feedstock”)
Methanol/Ethanol
Catalyst - “Lye” (Sodium Hydroxide or Potassium Hydroxide)

9. 9
Water
Outputs:
Biodiesel
Dirty Water
Glycerine
2.5 Biodiesel Attributes:
 High Cetane no. (avg. over 50)
 High Lubricity, even in blends as low at 1-2%
 High Energy Balance (3.2 to 1)
 Low Agriculture Inputs: Soybeans
 78% Life Cycle CO2 Reduction
 Renewable, Sustainable
 Domestically Produced
 Reduces HC, PM, CO in existing diesel engines
 Reduces NOx in boilers and home heating

10. 10
3. BIO-DIESEL PRODUCTION
Many standardized procedures are available for the production of bio-diesel fuel
oil [3]. The commonly used methods for bio-fuel production are elaborated below.
Fig 3. 1 Production steps of Biofuels
3.1 Blending
Vegetable oil can be directly mixed with diesel fuel and may be used for running
an engine. The blending of vegetable oil with diesel fuel in different proportion
were experimented successfully by various researchers. Blend of20% oil and 80%
diesel have shown same results as diesel and also properties of the blend is almost
close to diesel. The blend with more than 40% has shown appreciable reduction in

11. 11
flash point due to increase in viscosity. Some researchers suggested for heating of
the fuel lines to reduce the viscosity.
Fig: 3.2 Biodiesel Blends
Although short term tests using neat vegetable oil showed promising results, longer
tests led to injector coking, more engine deposits, ring sticking and thickening of
the engine lubricant[14]. Micro-emulsification, pyrolysis and transesterification
are the remedies used to solve the problems encountered due to high fuel viscosity.
Although there are many ways and procedures to convert vegetable oil into a
Diesel like fuel, the transesterification process was found to be the most viable oil
modification process [3].
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3.2 Transesterification
Transesterification is the process of using an alcohol (e.g. methanol, ethanol or
butanol), in the presence of a catalyst, such as sodium hydroxide or potassium
hydroxide, to break the molecule of the raw renewable oil chemically into methyl
or ethyl esters of the renewable oil, with glycerol as a by product. Biodiesel,
defined as the mono-alkyl esters of fatty acids derived from vegetable oil or animal

12. 12
fat, in application as an extender for combustion in diesel engines, has
demonstrated a number of promising characteristics, including reduction of
exhaust emissions [4]. Transesterified, renewable oils have proven to be a viable
alternative Diesel engine fuel with characteristics similar to those of Diesel fuel.
Fig:3.3 Transesterification process
The transesterification reaction proceeds with catalyst or without catalyst by using
primary or secondary monohydric aliphatic alcohols having 1–8 carbon atoms [14]
as follows:
Triglycerides + Monohydric alcohol = Glycerine + Mono-alkyl esters
3.3 Micro –emulsification
To solve the problem of high viscosity of vegetable oil, micro emulsions with
solvents such as methanol, ethanol and butanol have been used. A micro emulsion
is defined as the colloidal equilibrium dispersion of optically isotropic fluid
microstructures with dimensions generally in the range of 1–150 nm formed
spontaneously from two normally immiscible liquids and one or more ionic or non-
ionic amphiphiles.

13. 13
Fig:3.4 Micro –emulsification
These can improve spray characteristics by explosive vaporization of the low
boiling constituents in the micelles. All micro emulsions with butanol, hexanol and
octanol will meet the maximum viscosity limitation for diesel engines[13,14].
3.4 Cracking
Cracking is the process of conversion of one substance into another by means of
heat or with the aid of catalyst. It involves heating in the absence of air or oxygen
and cleavage of chemical bonds to yield small molecules[14].
Fig:3.5 Catalytic cracking process

14. 14
The pyrolyzed material can be vegetable oils, animal fats, natural fatty acids and
methyl esters of fatty acids. The pyrolysis of fats has been investigated for more
than 100 years, especially in those areas of the world that lack deposits of
petroleum.
Since World War I, many investigators have studied the pyrolysis of vegetable oil
to obtain products suitable for engine fuel application. Tung oil was saponified
with lime and then thermally cracked to yield crude oil, which was refined to
produce diesel fuel and small amounts of gasoline and kerosene.

15. 15
4. PROPERTIES OF BIO-DIESEL
The fuel properties of vegetable oils indicate that the kinematics viscosity of
vegetable oils varies in the range of 30–40 cSt at 38°C. The high viscosity of these
oils is due to their large molecular mass in the range of 600–900, which is about 20
times more higher than that of diesel fuel.
The flash point of vegetable oils is very high (above 200 8C). The volumetric
heating values are in the range of 39–40 MJ/kg,as compared to diesel fuels (about
45 MJ/kg).
The presence of chemically bound oxygen in vegetable oils lower their heating
values by about 10%.
The cetane numbers are in the range of 32–40.
The Biodiesel esters were characterized for their physical and fuel properties,
including density, viscosity, iodine value (IV), acid value, cloud point, pour point,
gross heat of combustion and volatility.
Methyl and ethyl esters prepared from a particular vegetable oil had similar
viscosities, cloud points and pour points, whereas methyl, ethyl, 2-propyl and butyl
esters derived from a particular vegetable oil had similar gross heating values.
However, their densities, which were 2–7% higher than those of Diesel fuels,
statistically decreased in the order of methyl similar to 2-propyl > ethyl > butyl
esters [14].
The HVs of the Biodiesel fuels, on a mass basis, are 9–13% lower than diesel.
The viscosities of Biodiesel fuels are twice that of diesel. The cloud and pour
points of diesel are significantly lower than those of the Biodiesel fuels.
The Biodiesel fuels produced slightly lower power and torque and higher fuel
consumption than diesel. Biodiesel is clean, efficient, natural energy alternative to
petroleum fuels.
Among the many advantages of Biodiesel fuel are : safe for use in all conventional
Diesel engines, offers the same performance and engine durability as Diesel fuel,
nonflammable and non-toxic, reduces exhaust emissions, visible smoke and odors.

16. 16
Biodiesel is better than Diesel fuel in terms of sulphur content (SC), flash point,
aromatic content and biodegradability.
4.1 Biofuel consumption:
Brazil stands 1st
in terms of Biofuel consumption. According to UNCTAD report,
Brazil uses pure ethanol in 20% of their vehicles and a 22 to 26 % ethanol-petrol
blend in the rest of their vehicles.
CO emission from automobiles decreased from 50g/km in 1980 to 5.8g/km in
1995.The USA and Australia use a 10% ethanol blend.
India is 4th
largest producer and the government mandated the use of a 5% ethanol
blend in petrol sold in nine sugarcane producing states.
Fig: 4.1 World Biodiesel production.

17. 17
5. EXPERIMENTAL ANALYSIS
A large number of experiments were carried out with vegetable oils as a
replacement of I.C. engine fuel by researchers from various parts of the world. A
summary of some of these experimental results is given below.
The various blends of rubber seed oil and diesel were prepared and its important
properties such as viscosity, calorific value, flash point, fire point, etc. were
evaluated and compared with that of diesel [1]. The blends were then subjected to
engine performance and emission tests and compared with that for diesel. It was
found that 50–80% of rubber seed oil blends gave the best performance.
Long run tests were conducted using optimized blend and diesel. It was found that
blend fueled engine has higher carbon deposits inside combustion chamber than
diesel-fueled engine. Utilization of blends requires frequent cleaning of fuel filter,
pump and the combustion chamber. Hence, it is recommended that rubber seed
oil–diesel blend fuel is more suitable for rural power generation Nwafor [2]
conducted test with rapeseed oil with advancing injection timings on Petter model
single cylinder, energy cell diesel engine. It is an air-cooled, high speed, indirect
injection, four-stroke engine.
The test results showed that plant oil fuels exhibited longer ignition delay with
slower burning rates. The test results also showed that each alternative fuel
requires injection advance appropriate to its delay period. The delay period was
noted to be influenced by the engine load, speed and the system temperature. At
the engine speed of 2400 rpm, there seems to be a significant increase in brake
thermal efficiency when running on rapeseed oil fuel with standard injection
timing.
Mechanical efficiency was observed to be reduced with advanced timing compared
to the standard timing test results at 2400 rpm. The engine ran smoothly with
advance of 3.58° as compared to the standard timing. A further 1.58° advance
tended to produce erratic behaviour of the engine. There seems to be a significant
reduction in CO and CO2 emissions with advanced timing for the speeds tested. A
moderate injection advance is recommended for operations at low engine speeds.

18. 18
The overall results indicate that vegetable oils exhibit longer combustion duration
with moderate rates of pressure rise, unlike petroleum derived fuels. Nwafor [3]
investigated the effect of elevated fuel inlet temperature on the emission
characteristics of diesel engine running on pure vegetable oil. Test runs were
conducted on Petter model single cylinder energy cell diesel engine. It is an
aircooled, high speed, indirect injection four-stroke engine.
The test results showed that the fuel consumption of heated and unheated oil
operations at high loads was similar and higher than diesel fuel operation. The
results indicate increases in exhaust temperature with heated oil over the other
fuels. The heated fuel showed a comparative reduction in delay period over the
unheated. The unheated oil and diesel fuel operations showed an increase in CO
production as the load was increased. The plant fuels showed marginal increase in
CO2 emissions over diesel fuel operation. The concentrations of HC in the exhaust
were higher when running on diesel fuel. The heated fuel showed a marginal
increase in HC emissions over the unheated plant fuel.
An experimental evaluation of using jojoba oil as an alternate Diesel engine fuel is
conducted by Huzayyin et al.[4].The tests were conducted on an air cooled, single
cylinder, four stroke, direct injection Diesel engine has 100 mm bore, 105 mm
stroke, compression ratio of 17 and a rated brake power of 5.775 kW at 1500 rpm
without any modifications. At present jojoba desert shrub are grown in the USA,
Latin America, South Africa and many other countries. In recent years, jojoba oil
has become one of the most genuinely Egyptian products. Its chemical and
physical properties have indicated a good potential of using jojoba oil as an
alternative Diesel engine fuel.
Blending of jojoba oil with gas oil has been shown to be an effective method to
reduce engine problems associated with the high viscosity of jojoba oil.
Reasonable viscosity values have been obtained using blend ratios as high as
60%J–40%D oil. Gvidonas Labeckas et al. [5] conducted tests with blends of shale
oil with diesel on naturally aspirated, four stroke, four cylinders, water cooled,
direct injection Diesel engine. Shale oil is produced in Estonia from local oil shale.
Test results show that when fuelling a fully loaded engine with shale oil, the brake
specific fuel consumption at the maximum torque and rated power is
correspondingly higher by 12.3% and 20.4%. However, the brake thermal

19. 19
efficiencies do not differ widely and their maximum values remain equal to 0.36–
0.37 for Diesel fuel and 0.32–0.33 for shale oil.
The total nitrogen oxide emissions from the shale oil at engine partial loads
remain considerably lower although when running at the maximum torque and
rated power, the NOx emissions become correspondingly higher by 21.8% and
27.6%. Karaosmanoglu et al. [6] conducted long term tests using sunflower oil on
single-cylinder direct injection, air cooled diesel engine, having a bore/stroke ratio
of 108:110 mm.Engine tests were conducted at a speed of 1600 rpm under part
load condition for 50 hour. An overall evaluation of results indicates that the
sunflower oil can be proposed as a possible candidate for diesel fuel.During the
test, the engine experienced no significant differences in drop or increase in power
and fuel consumption.
For studying changes in lubricating oil employed at the test, samples were taken
and their characteristics analyzed. Lubricating oil characteristics exhibited no
remarkable change. Changes that will take place at fuel injectors during the test
were observed on quantitative bases. The nozzle of the injector emerged clean,
without any formation of a cloggage. No significant problems were met during the
engine tests of the sunflower oil Silvio et al. [7] conducted tests using 100% palm
oil on direct injection four-stroke 70 kW diesel-generator. The results proved that a
diesel-generator set can be adapted to run with palm oil. Increasing the palm oil
temperature the performance and endurance of the diesel generator increases
compared to operation in ambient conditions.
The deposits on the cylinder head presented high levels when the engine operated
with palm oil heated at 50°C and acceptable levels when heated at 100°8C (almost
similar to the operation with diesel oil).However, other engine modifications are
required to improve lubricating oil degradation, performance, emissions and reach
a more efficient combustion. Narayana Reddy et al. [9] conducted tests with neat
Jetropa oil on a single cylinder, constant speed, direct injection diesel engine by
changing the engine operating parameters.
Tests shown that advancing the injection timing from the base diesel value and
increasing the injector opening pressure increase the brake thermal efficiency and
reduce HC and smoke emissions significantly. Enhancing the swirl has only a

20. 20
small effect on emissions. The ignition delay with Jatropha oil is always higher
than that of diesel under similar conditions. Improved premixed heat release rates
were observed with Jatropha oil when the injector opening pressure is enhanced.
When the injection timing is retarded with enhanced injection rate, a significant
improvement in performance and emissions was noticed.
Governoment of India is encouraging for the use of Jetropa oil as a Bio fuel in
India. China is rich in cottonseed and research on using cottonseed oil as diesel
engine fuel has been intensively and widely studied there. From a technological
point of view, the fuel property of cottonseed oil seems to meet the fundamental
requirements of diesel engine.Y.He et al. [10] conducted tests with blend of 30%
cottonseed oil and 70% diesel on diesel engine.
The experimental results obtained showed that a mixing ratio of 30% cottonseed
oil and 70% diesel oil was practically optimal in ensuring relatively high thermal
efficiency of engine, as well as homogeneity and stability of the oil mixture. For
this purpose, a modification of diesel engine structure is unnecessary, as has been
confirmed by the literature. High viscosity of cottonseed oil is one of the key
problems preventing its widespread application. In India, karanji oil was
experimented for analyzing its performance characteristics by Srinivasa Rao [15].
Karanjia oil was found to give a better performance compared to that of diesel.
Senthil Kumar et al. [16] conducted experiments by blending Jatropha oil with
diesel. It has been reported that exhaust gas temperature, smoke, HC and CO are
higher compared to diesel. Deshpande [17] used blends of linseed oil and diesel to
run the CI engine. Minimum smoke and maximum brake thermal efficiency were
reported in this study. Barsic et al. [18] conducted experiments using 100%
sunflower oil, 100% peanut oil, 50% of sunflower oil with diesel and 50% of
peanut oil with diesel. A comparison of the engine performance was presented.
The results showed that there was an increase in power and emissions. In another
study, Rosa et al. [19] used sunflower oil to run the engine and it was reported that
it performed well. Blends of sunflower oil with diesel and safflower oil with diesel
were used by Zeiejerdki et al. [20] for his experimentation. He demonstrated the
least square regression procedure to analyze the long-term effect of alternative fuel
and I.C. engine performance.

21. 21
Indian Railway, the largest transport corporation in India, is experimenting with
Jatropha oil ester to run passenger trains. If biodiesel is used as per plans, to the
extent of10% mixture with the conventional diesel, the railways would be able to
save on its rising fuel bill and also to control the atmospheric pollution levels
(sulphur and lead emissions). The Railways‟ annual fuel (diesel) bill of Rs. 3400
crores could be reduced by nearly Rs. 300 crores to 400 crores per annum by using
biodiesel [21].

22. 22
6. Why Biodiesel?
Biodiesel reduces carbon dioxide exhaust emissions by up to 80%.Biodiesel
produces 100% less SOx than petroleum.Biodiesel reduces exhaust smoke
(particulates) emissions by up to 75% so the usual black cloud associated with a
diesel engine can be eliminated.
Fig:6.1 REDUCTION IN EMISSIONS
6.1 Emissions:
 The use of biodiesel in a conventional diesel engine results in substantial
reduction of unburned hydrocarbons, carbon monoxide, and particulate
matter compared to emissions from diesel fuel.
 The ozone (smog) forming potentials of hydrocarbons is less than diesel
fuel.

23. 23
 Sulfur emissions are essentially eliminated with pure biodiesel .
6.2 Environmental Benefits:
 Biodiesel contains fewer aromatic hydrocarbon: benzofluoranthene: 56 %
reduction; Benzopyrenes: 71 % reduction .
 Biodiesel reduces emissions of carbon monoxide (CO) by approximately 50
% and carbon dioxide by 78 % on a net lifecycle basis.
 Biodiesel is biodegradable and non-toxic posing no threat to human health.
 Biodiesel reduces by as much as 65 % the emission of small particles of
solid combustion products.
 Biodiesel has higher cetane rating than petro diesel .
The smell of the biodiesel exhaust is far more pleasant.Biodiesel is much easier to
handle and does not cause cracking or redness.
Fig:6.2 Relative Greenhouse Gas Emissions

24. 24
Biodiesel is much less dangerous to put in vehicle fuel tank as its flash point is ±
150°C (300°F) as opposed to petroleum diesel ± 70°C (150°F).
Biodiesel provides significant lubricity improvement over petroleum diesel fuel so
engines last longer, with the right additives engine performance can also be
enhanced.
6.3 Economic Performance:
 Biodiesel is least-cost-strategy to comply with state and federal regulations.
 Use of biodiesel does not require major engine modifications. The only thing
that changes is air quality.
 Biodiesel has positive attributes such as increased cetane, high fuel lubricity
& high oxygen content.

25. 25
6.4 Petrol/Diesel Price Rising
Petrol/Diesel price = cost price (procuring + refining + marketing) + tax (central +
state)
+
Costprice = f(international crude price)
International Crude Price = f(Supply, Demand, Government policies, Financial
Institutions,Geopolitics)
International crude price is rising, therefore cost price is rising thus increasing the
petrol price.
Effect on Engine Performance:
6.5 Application of Biodiesel
 Car diesel engine
 Effective solvent
 Oxygenated fuel
 Bioheat

26. 26
7. ADVANTAGES AND DISADVANTAGES
The advantages of vegetable oils as Diesel fuel are:
 Bio diesel is environmental friendly.
 It can help reduce dependency on foreign oil.
 It helps to lubricate the engine itself, decreasing engine wear.
 It offers similar power to diesel fuel.
 It is safer than conventional diesel.
 It can be made from waste products.
 It can be made at home easily.
 Higher flash point makes it safer in transport and storage;
 Greatly reduces particulate matter and carbon monoxide emissions.
 Liquid nature-portability
 Ready availability,
 Renewability,
 Higher heat content (about 88% of D2 fuel),
 Lower SC,
 Lower aromatic content,
 Biodegradability.

27. 27
7.2 The disadvantages of vegetable oils as Diesel fuel are:
 Its storage for long period is not suitable for engine operation.
 It becomes gel in cold weather.
 It has water content. (Hygroscopic)
 It degrades rubber.
 It has higher (10%) Nox emissions.
 It decreases horsepower. (25%)
 Higher viscosity
 Lower volatility,
 The reactivity of unsaturated hydrocarbon chains.

28. 28
8. CONCLUSION
In this review, it is concluded that Compared to diesel fuel, a little amount of
power loss happened with vegetable oil fuel operations. Particulate emissions of
vegetable oil fuels were higher than that of diesel fuel, but on the other hand, NO2
emissions were less.
Vegetable oil methyl esters gave performance and emission characteristics closer
to the diesel fuel. So, they seem to be more acceptable substitutes for diesel fuel.
Raw vegetable oils can be used as fuel in diesel engines with some modifications.
Before starting wide application, there are some improvements that should be
done, such as Fuel systems should be optimized for vegetable oil operation.
VegeVegetable oils are mainly consumed on the food market. Therefore, it has
some unfavorable properties as fuel, such as high density, drying with time and
gumming, lower cetane number.

29. 29
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