A review: Advantages and Disadvantages of Biodiesel

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 04 Issue: 11 | Nov -2017 www.irjet.net p-ISSN: 2395-0072
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A review: Advantages and Disadvantages of Biodiesel
Shafaque Firoz1,*
1UG Student, School of Mechanical Engineering, KIIT University, Patia, Bhubaneswar, Odisha -751024
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Abstract - The present paper givesacompleteideaonthe
prospective technology for the production of clean energy
in the form of biodiesel. The fast growing society needs
energy which should be clean in all theaspectsandthiscan
be fulfilled by biodiesel. Due to increasing use of petroleum
fuels in automobiles and industrial sectors, in the past few
years, the world has started facing severe problems like
environmental pollution, ozone layer depletion, global
warming. Due to good oxidation characteristics and
lubricating nature Biodiesel is attracting the world to its
side as the alternative fuel. Therefore, manyscientists from
different parts of the globe are carrying out research to
find an alternative source in order to replace the existing
one. Biodiesel can replace the present energy crisis and
further help in reducing global warming. Utilization of
biofuels results in the reduction of global warming and
also helps in maintaining the demand and supply levels of
fossil fuels. The present paper gives an idea of different
types of fuels available along with comparison of
properties of different fuels and their advantages and
disadvantages.
Key Words: biodiesel, Diesel engine, transesterification,
performance, emission
1. INTRODUCTION
Energy has the capability to do work and has become a
key factor for a process to occur. An energy resource is
something that can produce heat, power, life, move
objects, or produce electricity. Matter that stores energy
is called a fuel. Human energy consumption has grown
steadily along with population and final reached a stage
of extinction[1]. In today's society, humans consume as
much as 110 times of the energy consumed by early
human i.e. the developing society needs energy for its
running. Most of the energy we use today come from
fossil fuels .But fossils fuels have a disadvantagethatthey
are limited in nature , and cause other potentially
harmful effects on the environment[2].
1.1 Renewable Resources
Renewable resources are that resources which can be
replenished by the environment over relatively short
periods of time. This type of resource is much more
desirable to use because it can be compensated by the
nature. Some examples of renewable energy sources are
solar energy, wind energy, hydropower, geothermal
energy, and biomass energy[3].
1.2 Non-Renewable Resources
In contrast to renewable resources, non-renewable
resources are resources that are not easily replenished
by the environment. Earth minerals andmetal ores,fossil
fuels (coal, petroleum, and natural gas)andgroundwater
in conditions are considered non-renewable resources.
2. FUELS
In our day to day life we see many machines running
around us, for running them some form of energy is
required which is provided by the help of fuel. A fuel is
any material that can be made to react with other
substances so that it releases chemical or nuclear energy
as which can be utilized directly or can be converted into
work. Fossil fuels were rapidly adapted during the
industrial revolution because they were cheap and
efficient[4]. They have become a major part our society
but they have also imputed to pollution.Currentlypeople
are more inclined towards usage of renewable fuels such
as biofuels.
Biofuels are fuels which are derived from biomass, they
can be in solid, liquid and gaseous form. Biomass can be
used directly for heating or power or it can be processed
to get the maximum benefit from it. Biofuel can be
produced from any carbonaceous material .Many
different plant derived materials are used for biofuel
manufacturing. Ethanol is also a biofuel because it is
made from corm[5]. Biodiesel is vehicle fuel made from
vegetable oil.
3. ENERGY FROM DIFFERENT FUELS
The amount of energy from different types of fuel
depends on the stoichiometric ratio, the AFR ratioandits
Specific energy, the energy per unit mass. Air–fuel ratio
(AFR) is the mass ratio of air to fuel present in a
combustion process such as in an internal combustion
engine or industrial furnace.

Table.1 Energy capabilities of common types of fuel
1 MJ ≈ 0.28 kWh ≈ 0.37HPh
As we can see from the above chart that the main source
of energy in India is fossil fuels which is not good for the
environment. So we require alternative fuels[4].
4. ALTERNATIVES TO REPLACE FOSSIL FUELS
4.1 Nonconventional energy resources
Energy generated by using wind, tides, solar, geothermal
heat, and biomass including farm and animal waste as well
as human excreta is known as non-conventional energy[6].
All these sources are renewableorandcanbe replenished by
the environment and do not cause environmental pollution.
Moreover they do not require heavy expenditure.
 Bio-Energy:
Biomass is considered as an energy source. The energy we
get from biomass is bio energy. Some vital forms of biomass
are inferior wood, urban waste. Biomass refers to all plant
material and animal waste product when pulp,livestock and
human waste[7]. It includes both terrestrial as well as
aquatic matter such as new plant growth, residues and
wastes.
 BIO-DIESEL
Bio-diesel refers to a vegetable oil or animal fat based diesel
fuel consisting of long chain alkyl (methyl, ethyl, or propyl)
esters. Biodiesel ismade bychemicallyreactingvegetable oil,
soybean oil, or animal fat with an alcohol produced from
different fatty acids[4].
Bio-diesel is employed in standard diesel engines and is
therefore distinct from the vegetable and waste oils used in
fuel converted diesel engines. Bio-diesel can be used alone,
or mixed with petro diesel in certain proportions. Biodiesel
is often referred to as monoalkyl ester with long chain fatty
acids[8]. Blends of 20% biodiesel and lower can be utilized
in diesel instrumentation with only minor modifications[6].
5. OILSEED CROPS FOR BIODIESEL PRODUCTION
Biodiesel can be produced from a wide variety of oilseed
crops and animal fats. In Europe, rapeseed oil is the major
biodiesel feedstock[7]. In the United States soya beans are
major biodiesel feedstock. Algae contains 90% of biodiesel
contain in it.
5.1 Different oil seed crops for biodiesel production are
 Soybeans
 Mustard
 Rapeseed and Canola
 Camelina
 Sunflower
 Karanja
 Mahua
 Neem oil
 Rice bran oil
 Jatropha
In addition to oil seed crops, biodiesel canbeproducedfrom:
5.3 Used and waste oil
Waste oil and grease can be collected from restaurants to
produce biodiesel. Whereas the processing costs of this
urban source are higher per gallon than the processingcosts
of virgin vegetable oils.
5.4 Animal Fats
Animal fats are low cost biodiesel feed-stocks. However,
there are also some drawbacks and challenges to animal fat
feed-stocks[4].
5.5 Algae
Microalgae have long been considered as potentially good
sources for biofuel production because of their relatively
high oil content and rapid biomass production[5].
6. SELECTION OF FEEDSTOCK FOR BIODIESEL
In general, seeds and nuts should be selected considering all
the outcomes and shortcomings, it should be stored in cool
and dry conditions, and processed quickly to avoid
degradation. The seeds shouldbeprocessedclosetothetime
when the oil will be processed into biodiesel. Before
processing the seeds mustbe cleaned,screened,and,insome
cases, hammered or dehulled[9]. The meal or cake in some
cases must be heated to deactivate toxic components before
use. Biodiesel is not the same as straight vegetable oil or
animal fat. A normal diesel engine will eventually be
damaged through the use of straight vegetableoil orstraight
animal fat fuel. Vegetable oils or animal fats must be
converted into biodiesel by reacting the oil or fat with an

alcohol and a catalyst. This process is referred to as
"transesterification[4]."
7. MAKING BIODIESEL
Biodiesel is made by reacting vegetable oil oranimal fatwith
an alcohol (methanol or ethanol) and a catalyst.Thisprocess
separates the glycerin from oil or fat. Thus resulting in
biodiesel which is thinner than the original oil or fat and
works better in diesel engine[10].Biodiesel productionisthe
method of producing the biofuel, biodiesel, through the
chemical reactions such as transesterification and
esterification. This involves vegetable or animal fatsandoils
being reacted with short chain alcohols (typically methanol
or ethanol). The alcohols used should be of low relative
molecular mass, ethanol is most commonly used because of
its low cost, however greater conversion into biodiesel can
be done using methanol[7]. The method of production is
base catalyzed transesterification, this process is chosen
because it consumes less time and also the cost of catalyst is
low. This process is cheaper than the acid esterification[11].
However alkaline catalyst has the disadvantage of high
sensitivity to both water and fatty acidpresent withinthe oil.
7.1 Transesterification
Animal and vegetable oils are composed of triglycerides,
which are esters of three free fatty acids and glycerol. In the
transesterification process, the addition ofalcohol andalkali
de-polymerization occurs, making it a stronger nucleophile.
It can be seen that the reaction did not have other inputs
than triglycerides and alcohol. Under normal conditions,the
reaction will proceed very slowly, so heating is used to
accelerate the reaction using a catalyst (acid and / or base).
Common catalysts for transesterification include sodium
hydroxide, potassium hydroxide and sodium methoxide[6].
The most economical processforprocessingvirginvegetable
oil, which only requires low temperature and pressure and
produces more than 98% of the crop. However, biodiesel
made from different sources or in other ways may require
acidic catalysts, which are much slower[12]. Due to the
dominant technique for production almost all biodiesel is
made from virgin vegetable oil using basic catalyst
techniques because it is action on an industrial scale, only
the base catalyzed transesterification method is discussed
below.
7.1 Base-catalysed transesterification mechanism
The transesterification reaction is the base catalyzed.Strong
bases capable of deprotonating the alcohol can be used, but
sodium and potassium hydroxide are generally selecteddue
to their lower prices. The presence of water causes
undesired base hydrolysis, so the reaction must remain
dry[6].
In the transesterification mechanism, carbonyl carbon from
the starting ester (RCOOR1) undergoes a nucleophilic attack
by an inlet alkoxide (R2O-) to provide a tetrahedral
intermediate, which returns to the starting material, or
passes to the transesterification product (RCOOR2).Various
species exist in equilibrium and therefore the product
distribution depends on the relativeenergiesofreactantand
product.
Chart-1 Transesterification reaction
8. DIFFERENT PRODUCTION METHODS
 Ultra and high shear in line and batch reactors
Ultra and High Shear Reactors inline or in batches enable
continuous, semi-continuous and biodiesel production in
batch mode. This drastically reduces production time and
increases production volume[4].
The reaction is carried out in the highly energetic zoneofthe
Ultra and High Shear mixer, reducing the size of the
incompressible liquid droplets, such as oil or fat and
methanol. Therefore, smaller the dropsizelargerthesurface
area, which will allow larger catalyst action.
 Supercritical process
An alternative, catalyst-free methodology for
transesterification uses supercritical methanol at high
temperatures and pressures during a continuousmethod. In
the critical state, the oil and methanol are in a single phase,
and reaction happens spontaneously and quickly[7]. The
process can tolerate water within the feedstock, free fatty
acids are converted to methyl esters rather than soap,thus a
wide variety of feedstocks may be used.Andalsothecatalyst
removal step is eliminated.
 Ultrasonic reactor method
In the ultrasonic reactor methodology, the ultrasonic waves
cause the reaction mixture to produce and collapse bubbles
uniformly. This cavitation at the same time provides the
space for blending and heating required to carry out the
transesterification process. Thus,usinganultrasonic reactor
for biodiesel production drastically reduces the reaction
time, reaction temperatures, andenergyinput.Therefore the
method of transesterification will run inline instead of using
the time consuming batch processing. Industrial scale
ultrasonic devices allow the commercial scale processing of
thousands of barrels per day[6].

9. PRODUCT PURIFICATION
Products of the reaction include not only biodiesel, but also
byproducts, soap, glycerol, excess alcohol,andtraceamounts
of water. All of these byproducts must be excluded for
perfect blend of biodiesel, but the order of removal is
process-dependent. The density of glycerol is greater than
that of biodiesel, and this property difference is the key to
separate the bulk of the glycerol coproduct. Residual
methanol is typically recovered by distillation and
reused[13]. Soaps can be removed or converted into acids.
Residual water is also removed from the fuel[6].
10. BIODIESEL AS A REMEDY TO CURRENTENERGY
CRISIS
10.1 Biodiesel as a fuel
Biodiesel meets both the biomass-based diesel and overall
advanced biofuel demand of the Renewable Fuel standard.
Biodiesel is a liquid fuel usually stated as B100 or neat
biodiesel in its pure, un homogenised form. Like petroleum
diesel, biodiesel is used as fuel in compression-ignition
engines. How well biodiesel performs in weather condition
depends on the blend of biodiesel[14]. The smaller the
proportion of biodiesel within the mix,the betteritperforms
in cold temperatures. Regular No. 2 diesel and B5 perform
the same in cold weather.
Table.2 Physical Characteristics of Biodiesel
Not all the light-, medium-, and heavy-duty diesel vehicles
are technically "alternativefuel"vehicles,severalarecapable
of running on biodiesel. Biodiesel that is most frequently
used as a blend with regular diesel fuel can be used in
several diesel vehicles without any engine modification. The
most common biodiesel blend is B20, which is 6% to 20%
biodiesel blended with petroleum diesel[4]. B5 (5%
biodiesel, 95% diesel) is commonly used in fleets[7]. Before
using biodiesel, it's necessary to check theengine’swarranty
to make sure that higher-level blends of alternative fuel do
not void or have an effect on it. Biodiesel improves fuel
lubricity and raises the Cetane number of the fuel. Diesel
engines depend upon the lubricity of the fuel to stay moving
components from wearing untimely. Federal regulations
have step by step reduced allowable fuel sulfur to only
fifteen parts per million, that has often resulted in lower
aromatics content in diesel fuel. One advantage of biodiesel
is that it can impart satisfactory lubricity to diesel fuels at
blend levels as low as 1%.
Chart-2 Biodiesel vehicle
Biodiesel fuel can also be used as a heating fuel in domestic
and commercial boilers. A blend of heating oil and
standardized biofuel is used here. It is sometimes known as
"bio heat" and is available in various blends; up to 20%.
Using biodiesel fuel existingfurnaceswithoutmodificationis
considered acceptable. Increase in the use ofbiodiesel fuel is
projected in the coming years.
10.2 EFFICIENCY
According to a recent study, an average farm consumes fuel
at 82 liters of oil per hectare of land to generate one crop.
However, a mean crop of oilseed makes oil atanaveragerate
of 1,029 L/ha, and high-yield oilseed fields turn out about
1,356 L/ha. It is clear to notice the ratio of input to output in
these cases which is roughly 1:13 and 1:16. Photosynthesis
is known to have an efficiency rate of about 3-6% of total
solar radiation[6]. Therefore, if the whole crop mass is used
for producing energy, the general efficiency of this chain is
currently about 1%.
10.3Comparing emissions
Our testing showed that emissions from the biofuels were
the same or better than from regular diesel by most
measures. None of the four fuels generated significant
amounts of carbon monoxide. Cooking oil produced less
smog-causing NOx than regular diesel, while our B100
produced a little more.

Table.3 Properties of Biodiesel
11. ADVANTAGES OF BIODIESEL FUEL
 Easy to use: No vehicle modification or any fueling
equipment needed.
 Power, Performance and Economy: Proven power
generation, performance and cost efficiency made
biodiesel a useful fuel.
 Effect on environment: Biodiesel is helping in
reducing pollution and improve health by lowering
the emission of CO2 which reduces the effect of
global warming.
 Biodiesel reduces the use of foreign oils.
 Biodiesel is safer to handle because it is less toxic
and easy to store than petroleum.
 Biodiesel helps communities by keeping energy
dollars at home.
12. DISADVANTAGES OF BIODIESEL FUEL
• At present, Biodiesel fuel is about one and a half
times more expensive than petroleum diesel fuel.
• It requires energy to produce biodiesel fuel from
soya crops, plus there is the energy of sowing,
fertilizing and harvesting.
• Another biodiesel fuel disadvantage is that it can
harm rubber houses in some engines.
• As Biodiesel cleans the dirt from the engine, this dirt
can get collected in the fuel filterandcloggingoccurs.
So, filters should be changed regularly.
• Biodiesel fuel distribution infrastructure needs
improvement, which is another of the biodiesel fuel
disadvantages.
13. CONCLUSION
Biodiesel provides energy security as it protects the
environment, and also boosts the economy. Today,biodiesel
turning as the growing alternative fuel not only in America,
but other parts of the world as well. One of the main reasons
behind transition to biodiesel fuel is energy security. Is that
the nation's dependence on foreign oil get reduced, use of
locally available sources is enhanced. Thus a country finds
energy security in biodiesel fuel without a decrease in
greenhouse gas emissions. Althoughthetotal energy balance
is still a debatable issue, but clearly the energy security due
to biodiesel fuel is enhanced. It has been observed that
properly managed biodiesel fuels have the prospective for
strengthening the security of supply and can also help in
generating different energies[7].
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