CHAPTER 2
16
LITERATURE REVIEW
CHAPTER 2
LITERATURE REVIEW
The whole world is facing the crises of depletion of fossil fuels as well as the
problem of environmental degradation. The rapid depletion of fossil fuel reserves
with increasing demand and uncertainty in their supply, as well as the rapid rise in
petroleum prices, has stimulated the search for other alternatives to fossil fuels. In
view of this, there is an urgent need to explore new alternatives, which are likely to
reduce our dependency on oil imports as well as can help in protecting the
environment for sustainable development. Many alternative fuels are being recently
explored as potential alternatives for the present high-pollutant diesel fuel derived
from diminishing commercial resources.
Biodiesel emerges as one of the most energy-efficient environmentally friendly
options in recent times to full fill the future energy needs. Biodiesel is a renewable
diesel substitute that can be obtained by combining chemically any natural oil or fat
with alcohol. During the last 15 years, biodiesel has progressed from the research
stage to a large scale production in many developing countries. In Indian context,
non-edible oils are emerging as a preferred feedstock and several field trials have
also been made for the production of biodiesel [41].
Vegetable oils either from seasonal plant crops or from perennial forest tree's origin,
after being formulated, have been found suitable for utilization in diesel engines.
Many traditional oil seeds like pongamia glabra, jatropha, mallous philippines,
garcinia indica, thumba, karanja and madhuca indica etc. are available in our
country in abundance, which can be exploited for biodiesel production purpose.
Many vegetable oils, animal fats and recycled cooking greases can also be
transformed into biodiesel. Biodiesel can be used neat or as a diesel additive in
compression ignition engines.
CHAPTER 2
LITERATURE REVIEW
In this chapter, a detailed survey of available literature is therefore undertaken to
review the different research achievements on vegetable oils and biodiesel as an
alternative fuel for a compression ignition engine, problems associated with pure
vegetable oils and their possible solutions with their structural details have been
looked into. In addition to this, physical and chemical properties of vegetable oils
as well as biodiesel, fuel formulation techniques, biodiesel production and
utilization, engine combustion, performance and emission characteristics have
also been collected. Efforts have also been made to assess the economic viability
of biodiesel.
2.1
HISTORICAL BACKGROUND OF BIODIESEL
Dr. Rudolf Diesel, who invented the first Diesel Engine in 1895, used only biofuel
in his engine. His visionary statement was “The use of vegetable oils for engine fuel
may seem insignificant today, but such oils may become in course of time, as
important as petroleum and coal tar products of the present time”. The above
prediction is becoming true today as more and more biodiesel is being used all over
the world. In 1900 at the world fair in Paris, a small version of a diesel engine ran
on plant oil. This was organized by the French society for the support of the Otto
engine. At that time, crude oil was available in abundance; hence, vegetable oils
could not attract as a source of fuel much. Despite the widespread use of fossil
petroleum-derived diesel fuels, interest in vegetable oils as fuel for internal
combustion engines was reported in several countries during the 1920s and 1930s.
While engineers and scientists have been experimenting with vegetable oils as fuel
for a diesel engine since 1900, it is only recently that the necessary fuel properties
and engine parameters for reliable operation have become apparent.
In recent times, due to realization that crude oil is limited and poses a threat to well
being of mankind from emissions of exhaust gases, vegetable oil has been revisited
for its scope as a fuel in compression ignition engines. Some operational problems
were reported due to the high viscosity of vegetable oils compared to petroleum
17
CHAPTER 2
18
LITERATURE REVIEW
diesel fuel, which results in poor atomization of the fuel in the fuel spray and often
leads to deposits and coking of the injectors and valves. To lower the viscosity of
vegetable oil, chemical and thermal processes were tried to make vegetable oil
compatible to compression ignition engines. Attempts to overcome these problems
included heating of the vegetable oil, blending it with petroleum-derived diesel fuel
or
ethanol,
pyrolysis,
cracking
of
the
oils,
micro-emulsification
and
transesterification, where triglycerides from vegetable oils react with a lower
alcohol to produce fatty acid alkyl esters possessing properties similar to mineral
diesel. Transesterification of a vegetable oil was conducted as early as 1853 by
scientists E. Duffy and J. Patrick, many years before the first diesel engine became
functional. On August 31, 1937, G. Chavanne of the University of Brussels
(Belgium) was granted a patent for a procedure for the transformation of vegetable
oils for their uses as fuels. The use of biodiesel was recognized much later and
became technically relevant only after the energy crisis in the year 1973 and
afterwards. More recently, in 1977, Brazilian scientist Expedito Parente invented
and submitted first industrial process for the production of biodiesel for patent [42].
2.2
PROPERTIES OF VEGETABLE OILS AND BIODIESEL
Ideal diesel molecules are saturated non-branched hydrocarbon molecules with
carbon chain length ranging from 12 to 18 whereas vegetable oil molecules are
triglycerides generally with un-branched chains of different lengths and different
degrees of saturation. Vegetable oils mainly contain triglycerides (90 to 98%)
and small amounts of mono and diglycerides. Triglycerides are esters of three
fatty acids and a glycerol molecule [43, 44].
CHAPTER 2
LITERATURE REVIEW
Vegetable oils can be used as alternative fuels because they are biodegradable, nontoxic, and clean fuels. Vegetable oils and their derivatives as diesel engine fuels
lead to substantial reductions in sulfur, carbon monoxide, polycyclic aromatic
hydrocarbons, smoke and particulate emissions. Number of vegetable oils like
karanja oil, rapeseed oil, rice bran oil, cottonseed oil, sunflower oil and jatropha oil
has been tested as fuels in diesel engines. Studies indicate that, over short periods of
time, neat vegetable oil perform satisfactorily in unmodified diesel engines.
Vegetable oils have high viscosity due to large molecular weight and bulky
molecular structure. The viscosity of liquid fuels affects the flow properties as well
as spray atomization, vaporization, and air/fuel mixture formation. Higher viscosity
also has an adverse effect on the combustion of vegetable oils in existing diesel
engines, fuel pumps and injectors. Temperature greatly affects the viscosity of
vegetable oils. It has been reported that the viscosity of oils and fats decreases
almost linearly with temperature. The significant fuel properties of vegetable oils as
listed in Table [2.1], indicates that the kinematic viscosity of vegetable oils varies in
the range from 27–67 cSt at 40⁰ C. The high viscosity of these oils is due to their
large molecular mass in the range of 600–900, which is an order of magnitude
almost 4 times higher than that of diesel. The flash point of vegetable oils is very
high (above 180⁰ C) and the heating values are in the range of 36–40 MJ/kg, as
compared to diesel fuels which is about 42-45 MJ/kg. The presence of chemically
bound oxygen in vegetable oils lowers their heating values by about 10%. The
cetane numbers are in the range of 30–45. Vegetable oils have comparable energy
density, cetane number, heat of vaporization, and stoichiometric air/fuel ratio to that
of mineral diesel [5, 35, 44]. Vegetable oils can be mixed with conventional diesel
in any proportion and blends can be used successfully in engines [45-48].
19
CHAPTER 2
20
LITERATURE REVIEW
Oils
Kinematic
Viscosity
(cSt 40° C)
Density
(kg/m3)
Heating
Value
(MJ/kg)
Cloud
Point
(° C)
Pour
Point
(° C)
Flash
Point
(° C)
Cetane
Number
Carbon
Residue
(w/w)
Diesel
Jatropha
Karanja
Rapeseed
Neem
Sunflower
Soybean
Coconut
Cotton
Seed
Rice Bran
Peanut
Linseed
Palm
Corn
Thumba
Babassu
Tallow
2.75
49.9
46.5
37
57
33.9
32.6
27.7
835
921
929
911
938
916
914
915
42.25
39.7
38.8
39.7
39.4
39.6
39.6
37.1
-15
16
13.2
-3.9
8
7.2
-3.9
-
-20
8
6
-31.7
2
-15
-12
-
66
240
248
246
295
274
254
281
47
40-45
40
37.5
47
37.1
38
52
0.001
0.64
0.64
0.30
0.96
0.23
0.27
0.13
33.5
914
39.4
1.7
-15
234
42
-
28.7
39.6
27.2
39.6
34.9
31.52
30.3
-
937
902
923
918
909
905
946
-
38.9
39.7
39.3
36.5
39.5
39.78
40
13
12.8
1.7
27
-1.1
20
-
1
-6.7
-15
-15
-40
-
200
271
241
271
277
201
150
201
30
42
34.6
42
37.6
45
38
-
0.24
0.043
0.24
6.1
Table [2.1] Properties of Different Vegetable Oils [4, 5, 35, 43, 44, 45, 47, 48]
Due to the molecular similarities of biodiesel to diesel fuel compounds, this
alternative fuel has a chance of fulfilling the requirements of diesel engine [49].
Biodiesel fueled engine emits lower polluting species without the need for
additional emission control equipment. The characteristics of biodiesel are close to
diesel fuels and therefore biodiesel becomes a strong alternative to replace the
diesel fuels [50]. The conversion of triglycerides into methyl or ethyl esters through
the transesterification process reduces the molecular weight to one-third that of the
triglyceride reduces the viscosity by a factor of about eight and increases the
volatility marginally. Biodiesel has viscosity close to diesel fuels. These esters
contain 10 to 11% oxygen by weight, which may encourage more combustion than
hydrocarbon based diesel fuels in an engine [51]. Biodiesel has lower volumetric
heating values (about 12%) than diesel fuels but has a high cetane number and flash
point [52-55]. Some of the enviable fuel properties of biodiesel derived from
different vegetable oils are presented in Table [2.2].
CHAPTER 2
21
LITERATURE REVIEW
Biodiesel
Kinematic
Viscosity
(cSt 40° C)
5.65
Jatropha
6.87
Karanja
7.2
Rapeseed
15
Neem
4.6
Sunflower
4.5
Soybean
3.36
Coconut
4.9
Peanut
5.7
Palm
3.6
Babassu
3.83-5.86
Thumba
Tallow
Density
(kg/m3)
Heating
Value
(MJ/kg)
Cloud
Point
(° C)
Pour
Point
(° C)
Flash
Point
(° C)
Cetane
Number
Carbon
Residue
(w/w)
879
897
883
882
868
872
866
883
880
879
889
-
38.5
37.9
37.37
38.5
40.58
39.76
36.1
39.37
-
13
1
1
5
13
4
.5
12
-1
-12
-7
-4
9
175
187
180
183
178
122
176
164
127
174
96
50
49
51
47
45-52
37-45
56
54
62
63
53
--
0.05
1.7
0.03
-
Table [2.2] Some Fuel Related Properties of Biodiesel Produced From Different
Vegetable Oils [50-55]
2.3
FUEL FORMULATING TECHNIQUES
The alternative diesel fuels must be technically and environmentally acceptable and
economically viable. From the viewpoint of these requirements, triglycerides
(vegetable oils / animal fats) and their derivatives shall be considered as viable
alternatives for diesel fuels. The problems with substituting triglycerides for diesel
fuels are mostly associated with their high viscosities, low volatilities and
polyunsaturated character. One of the main problems of vegetable oil use in diesel
engines is their higher kinematic viscosity because of heavier triglycerides and
phospholipids, due to which problems occur in pumping and atomization, ringsticking, carbon deposits on the piston, cylinder head, ring grooves, etc. Straight
vegetable oils are less suitable as fuels for diesel engines; since they have to be
modified to bring their combustion related properties specially viscosity closer to
mineral diesel. Heating or pyrolysis, dilution or blending, micro-emulsification and
transesterification are some well known techniques available to overcome higher
viscosity related issues associated with the use of vegetable oil in diesel engines and
to make them compatible to the hydrocarbon-based diesel fuels [35, 49, 50, 56].
CHAPTER 2
LITERATURE REVIEW
2.3.1 Heating or Pyrolysis
Heating or pyrolysis is the process by which high molecular weight compound
breaks into smaller compounds by means of heat with or without catalyst. The
liquid fractions of the thermally decomposed vegetable oils are likely to get
converted into liquid oils. Many investigators have studied the pyrolysis of
triglycerides to obtain products suitable for diesel engines [57, 58]. The pyrolyzate
oils have almost same viscosity, flash point, and pour point that of diesel fuel. The
cetane number of the pyrolyzate oil has been found to be lower. The pyrolyzate oils
from vegetable oils contain acceptable sulphur content, water and sediment and give
acceptable copper corrosion values but unacceptable ash and carbon residue.
Mechanisms for the thermal decomposition of triglycerides are likely to be complex
because of many structures and multiplicity of possible reactions of mixed
triglycerides [59]. Billaud et al. [60] studied the pyrolysis of a mixture of methyl
esters from rapeseed oil in a tubular reactor between 500 and 550⁰ C with nitrogen
dilution. The main product obtained was unsaturated methyl ester, which was
chemically similar to petroleum derived fuels.
2.3.2 Dilution or Blending
High viscosity fuels like vegetable oils can be mixed with low viscosity fuel like
diesel to overcome overall viscosity. These blends can then be used as diesel engine
fuels. Dilution of vegetable oils can be accomplished with a solvent, methanol or
ethanol. Vegetable oils can be directly mixed with diesel and may be used to run
diesel engines. Blending of vegetable oil with diesel has been tried successfully by a
number of researchers. The dilution of sunflower oil with diesel fuels in the ratio of
1:3 by volume has been studied and engine tests were carried out by Ziejewski et al.
[61]. They concluded that the blend could not be recommended for a long term use
in the direct injection diesel engines. Pryor et al. [62] had conducted the short term
and long term performance tests with blends of vegetable oil with diesel. In short
term performance test, crude-degummed soybean oil and soybean ethyl ester were
found suitable substitutes for diesel fuel.
22
CHAPTER 2
LITERATURE REVIEW
2.3.3 Micro-Emulsification
The formation of micro-emulsions is one of the potential solutions for the problem
of vegetable oil viscosity. A micro-emulsion is a system consists of a liquid
dispersed, with or without an emulsifier, in an immiscible liquid, usually in droplets
smaller than colloidal size. Micro-emulsions are isotropic, clear or translucent
thermodynamically stable dispersions of oil, water, surfactant and often a small
amphiphilic molecule, called co-surfactant. The droplet diameters in microemulsions range from 100 to 1000 Å. A micro-emulsion can be made of vegetable
oils with an ester and dispersant (co-solvent) of vegetable oils with an alcohol and a
surfactant and a cetane improver, with or without diesel fuels. Micro-emulsions,
because of their alcohol content have lower volumetric heating values than diesel
fuels, but the alcohols have a high latent heat of vaporization and tend to cool the
combustion chamber, which would reduce nozzle coking. Ziejewski et al. [63]
showed that the engine performance was almost same for the micro-emulsified
sunflower oil and the 25 % blend of sunflower oil in diesel.
2.3.4 Transesterification
Transesterification is a most suitable process to convert oils and fats into biodiesel.
It is the most popular reaction used for the conversion of vegetable oils into
biodiesel in order to reduce its viscosity. It is the reaction of an alcohol, in most
cases methanol, with the triglycerides present in oils, fats or recycled grease,
forming biodiesel (fatty acid alkyl esters) and glycerol. The reaction requires heat
and a strong base catalyst, such as sodium hydroxide or potassium hydroxide. The
transesterification process involves reacting vegetable oils with alcohols such as
methanol or ethanol in the presence of a catalyst (usually sodium hydroxide or
potassium hydroxide) at about 70⁰ C to give the ester and the byproduct, glycerin. It
has been reported that the methyl and ethyl esters of vegetable oil can result in
superior performance than neat vegetable oils.
23
CHAPTER 2
24
LITERATURE REVIEW
2.4
BIODIESEL
PROCESS
PRODUCTION
BY
TRANSESTERIFICATION
Biodiesel fuels are produced by a process called transesterification, in which
various oils (triglycerides) are converted into methyl esters through a chemical
reaction with methanol in the presence of a catalyst, such as sodium or potassium
hydroxide. The byproducts of this chemical reaction are glycerol and water, both of
which are undesirable and needed to be removed from the fuel along with traces of
the methanol, un-reacted triglycerides and catalyst. Biodiesel fuels naturally contain
oxygen, which must be stabilized to avoid storage problems [64-67].
Meher et al. [68] studied the effects of catalyst concentration (KOH), alcohol /oil
molar ratio, temperature and rate of mixing on the transesterification of karanja oil
with methanol. They found that the optimum reaction conditions for methanolysis
of karanja oil was 1% KOH as a catalyst, molar ratio 6:1, reaction temperature 65⁰
C and rate of mixing was 360 rev/min for a period of 3 hours. The yield of methyl
esters was found to be higher by 85% in 15 minutes and reaction was almost
complete in two hours with a yield of 97%. With 12:1 molar ratio or higher, the
reaction was completed within an hour. The reaction was incomplete with a low rate
of stirring (180 rev/min). Further in the optimization study, Meher et al. [69] found
that the yield of methyl ester from karanja oil under the optimal condition was 97 to
98%.
Rathore and Madran [70] studied the kinetics of transesterification of karanja oil
into its alkyl esters in supercritical methanol and ethanol without using any catalyst.
The effect of molar ratio and reaction temperature on alkyl ester formation was
studied. It was concluded that the overall yield of ester was more with methanol as
compared to ethanol.
Darnoko and Cheryan [71] reported data on palm oil kinetics. It was observed that
the rate of alkali-catalyzed (KOH) transesterification in a batch reactor increased
with temperature up to 60⁰ C. The further increase in temperatures did not reduce
the time to reach the maximum conversion.
CHAPTER 2
LITERATURE REVIEW
The free fatty acid and moisture content in the material are the key parameters for
determining the viability of the vegetable oil transesterification process. According
to Freedman et al. [72] the free fatty acid content should be lower than 1% to carry
out the alkali catalyzed reaction. In their study they observed that if the acid value
was greater than 1, more NaOH was required to neutralize the free fatty acids.
Water also caused soap formation, which consumed the catalyst and reduced
catalyst efficiency. The resulting soaps caused an increase in viscosity, formation of
gels and made the separation of glycerol difficult.
Ma et al. [73, 74] studied the effect of free fatty acids and water content in the
transesterification of beef tallow. The presence of water had more negative effects
on the transesterification than free fatty acids. They concluded that for best results,
the water content and the free fatty acid content in beef tallow should be kept below
0.06 % w/w and 0.5 % w/w respectively.
Zullaikah et al. [75] had successfully obtained biodiesel from rice bran oil with high
free fatty acids content. A two-step acid-catalyzed methanolysis process was
employed for the efficient conversion of rice bran oil into fatty acid methyl esters.
Hawash et al. [76] studied the transesterification of jatropha oil using supercritical
methanol in the absence of catalyst under different temperature conditions.
Ramadhas et al. [77] reported the use of acid catalyst followed by alkali catalyst in a
single process using rubber seed oil with high free fatty acid content. The objective
of this study was to develop a process for producing biodiesel from a low-cost
feedstock like crude rubber seed oil.
Iso et al. [78] have studied the transesterification by immobilized lipase in nonaqueous conditions. Noureddini et al. [79] have investigated the biodiesel
production by lipase catalyst. The time taken to get the 67% yield of biodiesel was
72 hours at room temperature. However, the energy input was zero. The reaction
time and the cost of lipase were hurdles to commercialize lipase processes.
25
CHAPTER 2
LITERATURE REVIEW
Various methods of biodiesel production from vegetable oils were also described by
Fukuda et al. [80]. Biodiesel production by transesterification from sunflower oil
was discussed by Antolin G. et al. [81]. Many researchers [82-88] have also
suggested different processes for the production of biodiesel from transesterification
by using different vegetable oils.
2.5
PERFORMANCE, EMISSION AND COMBUSTION BEHAVIOR
OF BIODIESEL ENGINE
Performance, emission and combustion behavior of diesel engine with different
vegetable oils and biodiesel has been evaluated by many researchers and scientists to
establish suitability and feasibility of vegetable oils and biodiesel as an alternative
fuel for diesel engines. The conclusions of previous studies are presented below.
2.5.1 Performance of Diesel Engine Using Vegetable Oils and Biodiesel
A number of researchers and scientists conducted performance tests on compression
ignition engines using different vegetable oils and biodiesel derived from different
feedstocks. The performance parameters such as power output, specific fuel
consumption, exhaust gas temperature and brake thermal efficiency of different
vegetable oils and biodiesel have been reviewed in a detailed manner in the
subsequent paragraphs.
Gerhard Vellguth [89] studied the performance of a direct injection single cylinder
diesel engine with different vegetable oils. He reported that vegetable oils could be
directly used as fuels in diesel engines on a short-term basis with little loss in
efficiency. In long-term operation of engine with vegetable oils, he observed
operational difficulties like carbon deposits, changes in the lubricating oil properties
and ring sticking problems.
26
CHAPTER 2
LITERATURE REVIEW
Rao and Gopalkrishna [90] studied the vegetable oils and their methyl esters as fuel
for diesel engines and found that the pure vegetable oils could be used in diesel
engines without any major problems. The direct injection diesel engine given almost
similar output for all the vegetable oils tested.
Altin et al. [91] indicated that the vegetable oils produced from numerous oil seed
crops have high energy content, most of them require some processing to assure safe
use in internal combustion engines. They also conducted experiments on a single
cylinder DI diesel engine to evaluate the performance and exhaust emissions using
sunflower oil, cottonseed oil, soya bean oil and their methyl esters. They found little
power loss, higher particulate emissions and less NOX emissions with neat vegetable
oils. They concluded that raw vegetable oils can be used as fuel in diesel engines
with some modifications. They also indicated that the methyl ester of vegetable oils
is more acceptable substitutes for diesel fuel.
Nwafor et al. [92, 93] performed tests on an indirect injection diesel engine with
rapeseed oil with an injection advance of 3.5 and 5⁰ CA BTDC. It was reported that
the delay period was noted to be influenced by the engine load, speed and system
temperature. At 2400 rev/min, there was a significant increase in brake specific fuel
consumption with standard fuel injection timing. There was a significant reduction
in carbon monoxide and carbon dioxide emissions with advanced timing for the
speeds tested. A moderate injection advance was recommended for operations at
low engine speeds. Further, he reported that the fuel consumption of heated and
unheated oil operations at high loads was slightly higher than the diesel fuel
operation. The heated fuel showed a comparative reduction in delay period over the
unheated oil. The overall test results showed that fuel heating was beneficial at low
speed and part-load operations.
Varaprasad et al. [94] investigated the effect of using jatropha oil and esterified
jatropha oil on a single cylinder diesel engine. They found that the brake thermal
efficiency was higher with esterified jatropha oil as compared to raw jatropha oil
but inferior to diesel. They also reported low NOX emission and high smoke levels
with neat jatropha oil as compared to esterified jatropha oil and diesel.
27
CHAPTER 2
LITERATURE REVIEW
Parmanik [95] studied the properties and use of jatropha curcas oil and diesel fuel
blends in compression ignition engine. The exhaust gas temperature was observed to
be reduced due to reduced viscosity of the vegetable oil diesel blends. It was found
that the fuel consumption was increased with a higher proportion of the jatropha
curcas oil in the blends. Acceptable thermal efficiencies of the engine were obtained
with blends containing up to 50% (by volume) of jatropha oil.
The tests were also conducted by Forson et al. [96] on a single-cylinder directinjection engine operated on diesel fuel, jatropha oil and blends of diesel and
jatropha oil in proportions of 97.4% / 2.6%; 80% / 20%; and 50% / 50% by volume.
The test results showed that jatropha oil can be conveniently used as a diesel
substitute in a diesel engine.
Jajoo and Keoti [ 9 7 ] carried out experiments on a single cylinder diesel engine
using rapeseed oil, soybean oil and their methyl esters as fuel. They revealed that
the engine performance with esters and diesel-vegetable oil blends were comparable
to that of diesel operation. For longer use methyl esters are preferable because of
their lower viscosity and low smoke formation tendency.
Ramadhas, Jayeraj and Muraledharan [98, 99] studied the characterization and effect
of using rubber seed oil in a compression ignition engine and found that the rubber
seed oil can be directly used instead of diesel and does not need any modifications in
the design of the engine. Further, they observed that up to 50% of rubber seed oil can
be substituted for diesel easily in the compression ignition engines without any
major modification and operational difficulties.
Agarwal et al. [100] evaluated the performance and emission characteristics of
linseed oil, mahua oil and rice bran oil blends. It was reported that linseed oil
blends showed comparable thermal efficiency at lower loads; 50% linseed oil
blends were found to be more efficient than other blends. Smoke density was higher
for 50% blends compared to all other linseed oil blends. Smoke density was found
to be higher for mahua blends as compared to mineral diesel at lower engine loads.
Rice bran oil blends showed comparable thermal efficiency to that of diesel fuel
28
CHAPTER 2
LITERATURE REVIEW
operation. 20% rice bran oil blend showed minimum brake specific energy
consumption and improved performance.
Herchel et al. [101] found that operation of the test engine with pure coconut oil and
coconut oil diesel blends for a wide range of engine load conditions was
satisfactory even without engine modifications. Increase of coconut oil in the
coconut oil-diesel blends resulted in lower smoke and NOX emissions with an
increase in the brake specific fuel consumption.
Rice et al. [102] presented the results of an engine test with different blends, neat
rapeseed oil and diesel fuel. There were no significant problems with engine
operation using these alternative fuels. The test results showed a reduction in brake
thermal efficiency as the amount of rapeseed oil in the blend increases. Reduction of
power-output was also noted with the increased amount of emissions.
Mustafa and Jacobus et al. [103, 104] made an extensive study on a single cylinder
diesel engine operated on a number of vegetable oils like sunflower oil, cottonseed
oil, soya bean oil and peanut oil to provide a detailed comparison of performance
and emissions. They observed that the engine operation with vegetable oils showed
slightly inferior performance. They also observed higher gas phase emissions with
vegetable oils as compared to diesel.
Korete [105] performed the comparative study using 100% rapeseed oil and
commercially available diesel fuel. They observed that the torque and power output
with rapeseed oil were only 2% lower as compared to diesel operation. This was
because of the high viscosity of the rapeseed oil. They found the lower heat release
rate with rapeseed oil than diesel. During the whole operating range they found that
the hydrocarbon and carbon monoxide emissions were higher with rapeseed oil as
compared to neat diesel operation. They also observed slower combustion and
lower maximum gas temperatures in the combustion chamber.
A number of researchers [106-108] also assessed the performance of a compression
ignition engine with different vegetable oils and found that the vegetable oil can be
used as blending component to diesel fuel. Prasad et al. [109] used non-edible oils
29
CHAPTER 2
LITERATURE REVIEW
such as pongamia and jatropha in low heat rejection diesel engine. Esterification,
preheating and increase in injection pressure have been tried for utilization of the
vegetable oils in diesel engine. Performance parameters such as the brake specific
energy consumption and exhaust gas temperature have been reported for varying
load for different non-edible oils. The emission of smoke and NOX has been found
to increase.
Sahoo and Das [110] with other scientists [111-112] investigated diesel engine
performance with biodiesel derived from jatropha oil, Karanja oil and honge oil.
Kumar et al. [113] found longer ignition delay for jatropha oil methyl ester as
compared to diesel fuel on a constant speed diesel engine.
Bhatt, Murthy and Dutta [114] carried out performance evaluation tests on a diesel
engine with karanja oil and its blends with diesel. It was observed that karanja oil
could be easily blended up to 40% (by volume) in diesel without any significant
difference in power output, brake specific fuel consumption and brake thermal
efficiency. The performance of engine with karanja oil blends improved with the
increase in compression ratio from 16:1 to 20:1.
Merve et al. [115] indicated that the torque and brake power output obtained with the
used cooking oil derived biodiesel were 3-5% less than diesel fuel. The engine
exhaust temperature at each engine speed with biodiesel was less than diesel fuel.
Scholl and Sorenson [116] studied the combustion of soya bean oil methyl ester in a
direct injection diesel engine. They found that most of the relevant combustion
parameters for soya bean oil methyl ester such as ignition delay, peak pressure, and
rate of pressure rise were close to those observed for diesel combustion at the same
engine load, speed, timing and nozzle diameter. It was found that ignition delay for
the two fuels were comparable in magnitude and the ignition delay of soya bean oil
methyl ester was found to be more sensitive to nozzle diameter than diesel. Carbon
monoxide emissions from soya bean oil methyl ester was slightly lower,
hydrocarbon emissions reduced drastically, NOX for two fuels were comparable and
smoke numbers for the soya bean oil methyl ester were lower than that of diesel.
30
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They also observed that the premixed portion of the combustion process had a lower
rate of combustion with the ester as compared to neat diesel.
Clark et al. [117] studied the effects of methyl and ethyl esters of soybean oil on a
4-cylinder diesel engine. They observed that the engine fuelled with soybean esters
resulted in a slightly less power combined with an increase in fuel consumption.
Agarwal [118] transesterified the linseed oil to prepared linseed oil methyl ester and
performed the engine experiments with different blends of biodiesel (linseed oil
methyl ester) with diesel and compared the results with baseline data for diesel
using a single cylinder direct ignition diesel engine. Further Agarwal and Das [119]
studied the biodiesel development and characterization for use as a fuel in
compression ignition engine and observed that almost all the important properties of
a biodiesel was in a very close agreement with the diesel oil making it a potential
candidate for partial replacement of diesel fuel. The 20% biodiesel blend was found
to be optimum, which improved the thermal efficiency of the engine by 2.5%,
reduced the exhaust emissions and brake specific fuel consumption.
Al-Widyan et al. [120] have carried out variable speed tests on a single cylinder
direct injection diesel engine using different blends of biodiesel in diesel, produced
from waste vegetable oil. The comparison of the biodiesel blends and the diesel fuel
operation was done in terms of engine performance and exhaust emissions. It was
found that with biodiesel blends, the engine operated smoothly without significant
problems. The blends burnt more efficiently with better fuel economy and further
generated lower emissions.
Zhang and Gerpan [121] investigated the combustion characteristics of the
turbocharged direct injection diesel engine using blends of isopropyl and methyl
esters of soya bean oil with diesel. They found that all fuel blends had similar
combustion behavior. Ignition delay for ester-diesel blend was shorter than diesel
fuel.
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Shaheed and Swain [122] observed that the esters derived from coconut oil have
similar characteristics to diesel fuel with little performance and emission
differences.
Bao and He [123] studied the cotton seed methyl ester as a partial substitute for
diesel oil for single cylinder diesel engines and observed that the mixture of 30%
cotton seed methyl ester and 70% diesel oil was suitable for engine operation.
Biodiesel derived from different feedstock and its blends with diesel were also
investigated for the performance and exhaust emissions by many researchers [124139]. They concluded that biodiesel and its blends with diesel can be used
successfully in diesel engines with almost the same efficiency as compared to diesel
and with reduced exhaust emissions.
Amit et al. [140, 141] developed a biodiesel production test rig based on
hydrodynamic cavitation. The hydrodynamic cavitation technique for biodiesel
production, found to be a simple, efficient, time saving, eco-friendly and
industrially viable. They also conducted experiments on four cylinders, direct
injection water cooled diesel engine with diesel and biodiesel blends of citrullus
colocynthis (thumba) oil produced through hydrodynamic cavitation technique.
Biodiesel blend of 30% thumba oil showed relatively higher brake power, brake
thermal efficiency, reduced brake specific fuel consumption and smoke with
favorable P-θ diagram as compared to diesel fuel.
The transesterification process for production of thumba oil methyl ester has been
analyzed by Karanwal et al. [142] and the various process variables like
temperature, catalyst concentration, amount of methanol and reaction time have
been optimized with the objective to maximize yield. The optimum conditions for
transesterification of thumba oil with methanol and KOH as catalyst were found to
be 60° C reaction temperature, 6:1 molar ratio of thumba oil to methanol, 0.75%
catalyst (w/w) and 1 hour reaction time.
Egusi melon seed oil was studied by Solomon et al. [143] and Ntui et al. [144] for
the first time as a potential feedstock for biodiesel production. Crude egusi melon
seed oil was transesterified using sodium methoxide as the catalyst at 60° C and
32
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molar ratio of 1:6 to produce its corresponding methyl esters. Egusi melon oil
methyl ester yield obtained was 82%. All the measured fuel properties of egusi
melon oil methyl ester were almost alike with soya bean and sunflower biodiesel.
Remarkably, the kinematic viscosity of egusi melon oil methyl ester was measured
to be 3.83 mm2/s, a value lower than most of the biodiesel fuels reported.
2.5.2 Exhaust Emission Characteristics of Vegetable Oils and Biodiesel
The use of vegetable oils and biodiesel in a conventional diesel engine results in
substantial reduction of un-burnt hydrocarbons, carbon monoxide and particulate
matter. However, Emissions of nitrogen dioxides are either slightly reduced or
slightly increased depending on the duty cycle and testing methods. The use of
biodiesel can decrease the solid carbon fraction of particulate matter (since the
oxygen in biodiesel enables more complete combustion), eliminates the sulphur
fraction (as there is no sulphur in the fuel), while the soluble or hydrogen fraction
stays almost same. Most of the studies on emission using vegetable oils and
biodiesel have reported lower emissions of un-burnt hydrocarbons, carbon
monoxide, smoke and particulate matter with some increase of NOX.
Nobukazu Takagi and Koichiro Itow [145] conducted experiments on a single
cylinder DI diesel engine with palm oil, rapeseed oil and the blends of palm oil and
rapeseed oil with ethanol and diesel fuel at different fuel temperatures. They found
that the vegetable oils and their blends generated the acceptable performance and
engine exhaust emission levels for short-term operation. Compared to diesel, the
methyl esters of rapeseed oil and palm oil offered lower smoke, NOX emission,
engine noise and higher thermal efficiency.
Wang et al. [146] observed higher carbon monoxide; lower carbon dioxide, lower
HC emissions, except 50% vegetable oil blend, due to higher oxygen content in
vegetable oil. Lower NOX emissions were reported as compared to mineral diesel
due to lower calorific value of vegetable oil.
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H. Raheman and A.G. Phadatare [147] studied the karanja esterified oil and found
that the blends of esterified karanja oil with diesel up to 40% by volume could
replace diesel for getting less emissions. The reduction in exhaust emission together
with an increase in torque, brake power, brake thermal efficiency and reduction in
brake-specific fuel consumption made the blends of karanja esterified oil (B20 and
B40) a suitable alternative fuel for diesel and could help in controlling air pollution.
David Chang and Van Gerpen [148] tested soybean methyl ester as compression
ignition engine fuel. They found that the biodiesel fuelled diesel engine produced a
higher fraction of soluble organic material in its exhaust emission. However,
hydrocarbon emissions were lowered when the engine was fuelled with biodiesel
blends. They reported that the soluble organic fraction was increased when the
fraction of biodiesel was increased in the blends.
In another study, Crookes et al. [149] observed a decrease in NOX emissions with
vegetable oil. They found that at 1500 rev/min and below, diesel NOX emissions
were higher than palm oil. In the speed range of 2500-3500 rev/min, NOX
emissions were found almost same for both oils due to the increase of turbulence
intensity in the combustion chamber which affects the air-fuel mixing process.
Kalligeros et al. [150] conducted experiments on a single cylinder direct injection
petter diesel engine using olive oil and sunflower oils as fuels in different
proportions with marine diesel. They reported lower un-burnt hydrocarbon, carbon
monoxide, nitrogen oxide and particulate with blends compared to neat vegetable
oils.
Nwafor [151] studied the emission characteristics of a diesel engine operating on
rapeseed methyl ester and found that rapeseed methyl ester and its blends with
diesel fuel emitted high carbon dioxide as compared to diesel fuel. Significant
reduction in emission of hydrocarbon was recorded when running on rapeseed
methyl ester. Hydrocarbon emissions observed to increase with increased amount of
diesel fuel in the blend.
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Ken Friis Hansen and Michel Grouleff Jensen [152] used methyl ester of rapeseed
oil for their experiments. They found decrease in hydrocarbon and carbon
monoxide emissions but an increase in NOX and particulate emissions. They also
conducted biological tests and reported that the use of rapeseed oil methyl ester as
fuel in diesel engine presents a lower potential health risk than diesel.
Rakopoulos et al. [153] reported that the smoke density significantly increased with
the use of vegetable oil blends of various origins. NOX emissions were slightly
reduced with the use of vegetable oil blends of various origins with respect to
mineral diesel due to lower cetane number (larger premixed combustion part) and
the absence of aromatics. The carbon monoxide emissions were increased and unburnt hydrocarbon emissions showed indefinite trends.
Watanabe et al. [154] reported that particulate matter emissions decreased with a
reduction in injection nozzle diameter.
Graboski et al. [155] studied the effect of blending biodiesel (methyl soya ester)
with conventional diesel on performance and emissions characteristics of a diesel
engine. They tested 20%, 35% and 65% biodiesel blends with diesel. By increasing
biodiesel proportions in the blend, increased NOX emission and reduced
hydrocarbons and particulate emissions were observed. There are several reported
results [156-157] of a slight increase in NOX emissions for biodiesel. However,
biodiesel’s lower sulfur content allows the use of NOX control technologies that
cannot be otherwise used with conventional diesel. Hence, NOX emissions can be
effectively managed and eliminated by engine optimization.
2.5.3 Combustion Behavior of Vegetable Oils and Biodiesel
Heat release analysis of engine pressure data is a means of indirectly depicting the
combustion process occurring in the engine. A detailed experimental description of
combustion evolution in diesel engines is extremely complex because of the
simultaneous formation and oxidation of air/fuel mixture. It is carried out within the
framework of the first law of thermodynamics. The pressure crank angle history of
an engine is affected by combustion, heat transfer and mass loss. The heat release
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pattern alone indicates the affect of combustion. Thermal efficiency and peak
cylinder pressure is very much influenced by the heat release pattern. Heat added
before the TDC increases heat losses, frictional losses and peak cylinder pressure.
During the combustion process the burning proceeds in three distinguishable stages.
In the first stage the rate of burning is very high and lasts for only a few crank angle
degrees. It corresponds to the period of rapid pressure rise. The second stage
corresponds to a period of gradually decreasing heat release rate and lasts about 40⁰
CA. Normally about 80% of the heat energy is released in these two phases. The
third stage corresponds to a small but distinguishable rate of heat release persists
throughout the expansion stroke. The heat energy during this period usually amounts
to 20% of the total fuel energy. The different methods for computation of heat
release rate from cylinder pressure data vary in the degree of accuracy with which
the contents of the cylinder are considered. Some methods are simple and easy to use
and others are complicated and involve extensive computation to achieve accuracy
[158, 159].
Senatore et al. [160] reported that with rapeseed oil methyl ester, heat release
always takes place earlier than mineral diesel, because fuel injection starts earlier
for biodiesel blends due to their higher density, leading to higher peak cylinder
temperature.
McDonald et al. [161] obtained the heat release from the actual pressure angle
diagram with soya bean oil methyl ester as a fuel in an indirect injection diesel
engine and concluded that the overall combustion characteristics were quite similar
to diesel operation except shorter ignition delay for soya bean methyl ester.
Niehaus and Carroll [162] found that thermally decomposed soybean oil produced
slightly less power than diesel fuel and also produced low levels of hydrocarbons
and NOX emissions. The heat release rate was lowered with thermally cracked
soybean oil as compared to diesel. They suggested that by advancing the injection
timing, combustion temperatures can be increased and a higher maximum rate of
cylinder pressure rise and higher levels of premixed burning with the oil can be
achieved.
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Bari et al. [163] observed that crude palm oil had a 6% higher peak pressure than
diesel. They also observed that crude palm oil had a 2.6⁰ CA shorter ignition delay,
but lower maximum heat release rate compared with diesel. Chemical reactions,
such as cracking of the double bonds of the carbon chain, could have produced light
volatile compounds which result in a shorter ignition delay as compared with diesel.
Due to the shorter ignition delay, less fuel was injected during the delay period
resulting in lower maximum heat release rates. This also resulted in less intense
premixed combustion, and usually translates into lower tendency to knock. Crude
palm oil had a longer combustion period than diesel. This is due to the fact that
another chemical reaction, polymerization of vegetable oil at higher temperatures
could have produced heavy low-volatile compounds. These heavy compounds are
difficult to combust and could not completely burn in the main combustion phase,
and subsequently continued to burn in the late combustion phase.
2.6
DUAL FUEL OPERATION OF DIESEL ENGINE
In the dual fuel engine, two fuels are used simultaneously. The secondary fuel or
pilot fuel (diesel, biodiesel etc.) is used to initiate the combustion process with the
primary fuel that is usually gaseous or liquid fuels (methanol, ethanol, gasoline etc.)
in the fumigated form. In the compression ignition dual fuel engines, the pilot fuels
are injected in a normal manner after compression of the primary fuel air mixture.
Extensive experimental investigations were done by M. P. Poonia [164] to study the
effect of the pilot (diesel) fuel injection parameters, pilot fuel quantity, intake
temperature, exhaust gas recirculation and intake air throttle on combustion and
performance of dual fuel engine using LPG as primary fuel. The analysis of the
study suggested that at a low injector lift pressure (150 bars) resulted in severe
knock at high loads whereas at loads less than 80%, the improvement in brake
thermal efficiency up to 3% was obtained by reducing the injector pressure from
170 to 150 bars. The injection delay found in dual fuel mode was always longer
than diesel operation mode. The optimum performance was obtained at 20% load
and 50% throttle along with 40% load and 37.5% throttle closing.
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Some researchers [165, 166] did experiments by using CNG as a primary gaseous
fuel with diesel as pilot fuel.
Ramesh et al. [167] studied the dual fuel operation of karanja oil and its biodiesel
with LPG as the inducted fuel in compression ignition engine. Banapurmath et al.
[168, 169] conducted a series of experiments to obtain combustion characteristics of
a 4-stroke compression ignition engine operated on neem, rice bran, honge oil and
honge oil methyl ester when directly injected and dual fuelled with producer gas
induction.
Stanislaw Szwaja and Karol Rogalinski [170] presented the results of investigations
carried out with the combustion of hydrogen in a compression ignition diesel
engine. Namasivayam et al. [171] conducted experimental investigations using
biodiesel, emulsified biodiesel and dimethyl ether as pilot fuels using natural gas as
primary fuel.
2.7
ECONOMIC FEASIBILITY OF BIODIESEL
The Biofuels market has been witnessing a continuous growth and developments
across the world over the past few years. Governments across the world are feeding
huge money and resources into the development of this sector in an attempt to
reduce their dependency on oil. The volatile oil prices and production levels have
further enlightened the need for continuous development in this sector. During
2001-2006 alone, the global annual production of biodiesel and ethanol grew by
43% and 23%, respectively. The major economic factor to consider for input costs
of biodiesel production is the feedstock (price of seed, seed collection and oil
extraction, transport of seed and oil), which is about 75–80% of the total operating
cost. Other important costs are labor, methanol and catalyst, which must be added to
the feedstock. Cost recovery will be through the sale of cake and of glycerol.
Economical feasibility of biodiesel depends on the price of the crude petroleum and
the cost of transporting diesel long distances to remote markets in India. It is certain
that the cost of crude petroleum is bound to increase due to increase in its demand
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and limited supply. Further, the strict regulations on the aromatics and sulphur
contents in diesel fuels will result in higher cost of production of diesel fuels as
removal of aromatics from the distillate fractions requires capital-intensive
processing equipments. India has rich and abundant forest resources with a wide
range of plants and oilseeds. The production of these oilseeds can be stepped up
many folds if the government takes the decision to use them for producing
alternative fuels for diesel engines.
Palm oil and refined soya oil are the main option that is traded internationally. The
costs for biodiesel production from palm oil, soya oil and jatropha oil are estimated
about US$ 0.82/litre, US$ 0.70/litre and US$ 0.65/litre respectively. In India,
estimated current biodiesel finished production costs lies somewhere between Rs.
42 to 52 per litre [2, 172-174].
The Government of India also envisaged setting up of the National Biofuel Board to
develop a road map for the use of biofuels, besides taking appropriate policy
measures. In order to promote biodiesel and its production by providing necessary
support to the cultivators of jatropha, the Ministry of Petroleum and Natural Gas
announced the biodiesel Purchase Policy in October 2005. The policy provided for
the purchase of biodiesel at 20 specified purchase centers in 12 states at Rs. 25/litre
(inclusive of taxes and duties) from January 2006, moreover, the Government of
India fully exempted biodiesel from excise duties in the Union Budget of February
2007. The Indian government also announced, on 23rd December, 2009, attractive
incentives to encourage biofuels plantation in wastelands and to utilize indigenous
biomass feedstocks for the production of biofuels. It addresses the issues across the
entire value chain from plantations and processing to marketing of biofuels. India’s
new policy on biofuels targets blending at least 20% biofuels in diesel and petrol by
2017. This implies that 13.38 million tonnes of biodiesel will be required [175].
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Sudha et al. [176] estimated the waste land availability and economical biomass
production potential in India. Augustus et al. [177] screened 22 plants at Western
Ghats (Tamil Nadu) in India as economical potential alternative crops for biodiesel.
Other scientists Mohibbe et al. [178] pointed out some selected plants, which have
great potential for biodiesel production in India. Giibitz et al. [179] and Kandpal et
al. [180] highlighted the potential of jatropha oil for fulfilling the future energy
needs. Barnwal et al. [181] have highlighted the economical production and
utilization of biodiesel in India. A detailed economic analysis of vegetable oil based
biofuels in Spain was made by Dorado et al. [182]. They identified that the price of
the feedstock was one of the most significant factors. Also, glycerol was found to be
a valuable by-product that could reduce the final manufacturing costs of the process
up to 6.5% depending on the raw feedstock used.
2.8
INTERNATIONAL SCENARIO OF BIODIESEL
Global production of biofuels has been growing rapidly. Many countries around the
world are embarking on ambitious biofuel policies through renewable fuel standards
and economic incentives. As a result, both global biofuel demand and supply is
expected to grow very rapidly over the next two decades, provided policymakers
maintain their policy goals. While the motivation for this expansion is complex, the
most important rationale is to enhance national energy security. Due to the growing
demand for fossil fuels and their relatively limited supply, governments of many
energy-short countries are searching for any and all means to increase their energy
production. Total biofuel production expected to grow more than six-fold from 12
billion gallons in 2005 to 83 billion gallons in 2030. Market expansion will be led
by a more than doubling of the global market for bio-ethanol, with the biodiesel
market achieving even more rapid growth [2, 175, 183].
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41
LITERATURE REVIEW
The utilization of biodiesel is not new, since it has been used as a substitute for
mineral diesel since the early 20th century, but in small quantities. What is new is
that from 2005 onwards biodiesel production and use has increased significantly.
The world biodiesel industry is still in its infancy but devolving rapidly. World
output of biodiesel production in 2007 is reached to 9.52 million tonnes, valued at
about US$ 7 billion. By 2011-12, total biodiesel production could be as high as 20
million tonnes [2, 3, 4, 175, 184]. Table [2.3] shows the biodiesel production of
various countries in million tonnes. High fuel prices and generous regulatory
support have given the sector healthy margins and relatively short investment
payback times. Only a small fraction of world biodiesel production is currently
exchanged internationally, but this may change in the future.
Country
06-07
07-08
08-09
09-10
10-11
European Union
4.85 MT
5.95 MT
7.49 MT
8.42 MT
9.55 MT
USA
1.13 MT
1.70 MT
2.69 MT
1.80 MT
2.10 MT
Argentina
0.05 MT
0.18 MT
0.74 MT
1.16 MT
1.60 MT
Brazil
0.06 MT
0.36 MT
1.03 MT
1.40 MT
2.00 MT
Other
1.03 MT
1.33 MT
2.37 MT
2.94 MT
3.91 MT
Total
7.12 MT
9.52 MT
14.32 MT 15.72 MT 19.16 MT
Table [2.3] Production of Biodiesel in Different Countries in Million Tonnes
[2, 3, 4, 34, 175, 183-190]
CHAPTER 2
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LITERATURE REVIEW
Owing to their availability, various oils have been in use in different countries as
feedstock for biodiesel production. The vegetable oils mainly used for biodiesel
production in Europe are rapeseed or sunflower oil, USA and Canada uses soya
bean, rapeseed, other waste oils and fats; frying oil and animal fats are the chosen
option in Ireland; castor oil and soya bean oil is used in Brazil; coconut oil is
preferred in Malaysia and Philippines; palm oil in Thailand, Malaysia, Indonesia
and the Philippines; cotton seed oil in Greece; linseed and olive oil in Spain;
jatropha and karanja are used in India, Nicaragua and Africa to produce biodiesel.
Several other plants such as neem (azadirachta indica), meswak (salvadora species),
mahua (madhuca indica), rubber (hevea species), castor (ricinus communis),
diploknema butracea, garcinia species and thumba (citrullus colocynthis) can also
be used for producing biofuels in India [183-190]. Table [2.4] summarizes the
feedstock used to produce biodiesel in various countries.
Vegetable oil
Country
Rapeseed
France, USA, Canada
Sunflower
Italy, Southern France, Italy, Spain
Soya Bean
USA, Canada, Brazil, China
Castor
Brazil, India
Palm
Malaysia, Indonesia, Thailand, Philippines
Coconut
Malaysia, Philippines
Linseed, Olive
Spain
Cotton Seed
Greece, Malaysia,
Jatropha
Nicaragua, India, Central America, Africa
Karanja, Mahua, Neem
India
Canola
Canada, European Countries
Used frying oils
Australia, Ireland
Waste oils and animal fats
USA, Canada, Japan, Ireland
Table [2.4] Feedstock Used to Produce Biodiesel in Various Countries [183-190]
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LITERATURE REVIEW
2.9
DEVELOPMENT OF BIODIESEL IN INDIA
Biofuels are going to play an extremely important role in meeting India’s energy
needs. India is not only a large importer of oil with the prospect of increased
imports in the future, but also has significant potential for production of biofuels in
the country. India actually has large areas of wasteland, which could be utilized for
the production of biofuels. India and many countries in the world are on the verge
of devising and implementing programme for production, conversion and use of
biofuels, it is essential to base these on the rapidly expanding knowledge that
already exists in this area. Adoption of biofuels programme has several socioeconomic impacts as it creates domestic jobs in plant construction, operation,
maintenance and support in the surrounding communities. Biodiesel and bio-ethanol
also help in improving the air quality with reduced automotive emissions, because
they undergo complete oxidation. The Indian government has taken a major
initiative for promoting biofuels, ethanol from sugar cane (molasses) and biodiesel
from plants such as jatropha, jojoba and karanja. For a country like India, biofuels,
especially biodiesel production promises a number of economic, environmental and
social benefits, such as large-scale employment generation, particularly in the rural
sector. The biodiesel programme will open up a large number of land-based
employment opportunities through the raising of plantations and their subsequent
maintenance, collection of seed, the processing of vegetable seeds into oil and
transesterification.
In India, the sources of biodiesel are non-edible oils. Due to its wider adaptability,
jatropha curcas (ratanjyot) is regarded as the major source of biodiesel. The other
sources of biodiesel in the country are pongamia pinnata (karanja or honge),
calophyllum inophyllum (nagchampa), hevca brasiliensis (rubber), thumba (citrullus
colocynthis) and other vegetable oils. To encourage the production and use of
biodiesel in India, the Government of India set up a committee for the development
of biofuels in July 2002 under the Planning Commission. Based on the
recommendations of the committee, the National Mission on Biodiesel was
launched in the country, which was proposed to be implemented in two phases over
nine years, that is, Phase I from 2003 to 2007 and Phase II from 2007 to 2012.
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Phase I was the demonstration and test phase. The primary aim of this phase was to
cultivate jatropha and similar plants in a total area of 0.4 Mha in various states of
the country. The Government of India provided the necessary funding for the
project. Phase II has been proposed to focus on a self-sustaining expansion of the
programme, leading to the production of biodiesel required to meet the demand
during 2011-12. The committee projected that by the end of the Eleventh Plan
(2011-12), the demand for high speed diesel shall be 66.9 MT, requiring 13.38 MT
of biodiesel to meet the requirement of 20% blending of mineral oil-based diesel
with biodiesel. It is estimated that to meet the production of 13.38 MT of biodiesel,
about 11.2 Mha of land would be required for plantation [1, 2, 34, 175, 191].
The Indian biodiesel programme is at a nascent stage, and the supply of raw
materials is a limiting factor for the development of the biodiesel economy in our
country. In the present scenario, when most of the cultivable area has been occupied
by conventional or cultivated crops, plant species that can come up in degraded
lands under less favorable environmental conditions need to be promoted.
Cultivation of jatropha coupled with increasing seed collection efficiency will help
augment the production of oil and also help to generate income and employment
opportunities for the weaker sections of the society. It is necessary that all the
stakeholders in the biodiesel programme develop some know-how transfer
mechanism, which provides for the sharing of fundamental data on cultivation of
biodiesel feedstock plants and its exploitation, marketing strategies, capacity
development, and execution of the necessary predictive research. In the biodiesel
sector, India has taken the initial steps toward commercial production. The work
accomplished so far includes developing high-yielding varieties of jatropha,
initiating jatropha nurseries, setting up pilot-plants for biodiesel manufacture and
testing biodiesel in public transport locomotives and buses. India has embarked in
the largest scale jatropha plantations in the world, despite the many uncertainties
involved, particularly lack of commercial experience, low productivity and land
quality [175, 191, 192].
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2.10
SUMMERY OF LITERATURE SURVEY
The literature review suggests that the vegetable oils produced from numerous oils
and seed crops have high energy content and reasonably good fuel properties, but
they require processing to biodiesel for its safe use in compression ignition engines.
It is reported that because of high viscosity, the neat vegetable oils can lead to
thickening in cold climate, fuel flow problems, poor atomization and low efficiency.
The vegetable oils therefore need to be converted into biodiesel, which has
properties suitable for application in diesel engines. The available literature shows
that the transesterification process has been a most suitable and acceptable method
for biodiesel production. From the experiments and studies conducted by plenty of
scientists and researchers, it has been observed that the biodiesel mostly causes
reduction in engine power and torque, but some studies have reported higher engine
power than conventional diesel fuel. Most of the studies showed lower carbon
dioxide, carbon monoxide, hydrocarbons and smoke emissions with the biodiesel as
compared to mineral diesel with a slight increased in NOX emissions.
Although encouraging work has been carried out on performance, emissions and
combustion of biodiesel produced from vegetable oils like jatropha oil, karanja oil,
sunflower oil, soya oil etc., but it was observed from literature survey that limited
amount of work has been done to evaluate performance, emission characteristics
and combustion analysis of diesel engine with biodiesel produced from nontraditional vegetable oils like thumba oil, neem oil etc. The literature review also
indicates that detailed study on evaluation of performance, exhaust emission and
combustion behavior of the biodiesel dual fuel engine with LPG gas induction and
biodiesel injection has been scantily reported. The present study is undertaken
because the prospect for vegetable oils and biodiesel is very promising in the short
term because of their availability and suitability as a diesel engine fuel.
45