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CHAPTER I
INTRODUCTION
Rapid industrialization and techno-economic developments have resulted in
fast depletion of fossil fuels accompanied by serious environmental issues. The
longevity of the world’s oil reserves is up for debate. On the other hand, global
warming threatens the world nations forcing for the emergence of sustainable energy
sources. Countries are striving for energy security and independence, since the base
strength of a nation is its energy resources.
Energy resources available in two forms – renewable and non-renewable, are
the prime indicators of a country’s growth and development. Till date we are mainly
relying on non-renewable fossil fuels – coal, oil and natural gas contributing to more
than 80% of our consumption. The burning of fossil fuels produces around 21.3
billion tonnes (21.3 gigatonnes) of carbondioxide per year, and it is estimated that
natural processes can only absorb about half of that amount, leaving a net increase of
10.65 billion tonnes of atmospheric carbondioxide per year (one tonne of
atmospheric carbon is equivalent to 44/12 or 3.7 tonnes of carbon) [1].
Carbondioxide, one of the greenhouse gases enhances radiative forcing and
contributes to global warming, causing climatic changes and rise in the average
surface temperature of the earth which results in runaway climatic changes like
methane release from permafrost and also clathrates which have been found under
the sediment deposits beneath the ocean floors of earth [2,3]. Global warming
potential of methane is 72 times that of carbondioxide which will further enhance
global warming to a higher order. Fossil fuels also contain radioactive materials,
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mainly uranium and thorium, which are released into the atmosphere. In 2000, about
12,000 tonnes of thorium and 5,000 tonnes of uranium were released worldwide
from burning coal [4].
a) World energy consumption by sector, 2012 (EIA data) b) World transportation
energy by source, 2009 (International Energy Agency data).
Global energy consumption, 2011.
Country Energy(Mtoe)
China 2 648
US 2 225
India 759
Russia 725
Japan 469
Germany 317
Brazil 268
Canada 266
South Korea 257
France 257
As per the US Energy Information Administration (EIA), transportation
sector contributes 26.6% of the total energy consumption, where fossil fuel reserves
contribute nearly the entire range [5]. According to the estimated report, globally the
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greatest energy consumption is by China and US parting around 40% [6]. Moreover
in US and Europe, energy consumed for transportation is almost one third with 30%
carbondioxide emission. Of the total energy, almost the entire sector of
transportation is fuelled by oil products. Due to increasing demand for oil in China,
India and other Asian countries, oil prices are shooting in the world market.
1.1 Crude oil
Oil has become the world's most important source of energy since the mid-
1950s, due to its high energy density, easy transportability and relative abundance
and is being consumed increasingly. Petroleum is also the raw material for many
chemical products, including pharmaceuticals, solvents, fertilizers, pesticides and
plastics which contribute around 16%. Petroleum is found in porous rock formations
in the upper strata of some areas of the earth's crust. There is also petroleum in oil
sands (tar sands). Known oil reserves are typically estimated at around 190 km3 [1.2
trillion (short scale) barrels] without oil sands, [7] or 595 km3 (3.74 trillion barrels)
with oil sands [8]. Based on data from Organization of Petroleum Exporting
Countries at the end of 2011, the highest proved oil reserves including non-
conventional oil deposits are in Venezuela (24.8% of global reserves), Saudi Arabia
(22.1% of global reserves), Iran (12.9%) and Iraq (11.8%) [9]. Consumption of oil is
currently around 84.6 million barrels (13.4×106 m3) per day or 4.9 km3 per year,
which in turn yields a remaining oil supply of only about 120 years, if current
demand remains static [10].
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Worldwide crude oil production and consumption rate.
Unconventional sources, such as heavy crude oil, oil sands, and oil shale are
not counted as part of oil reserves. These unconventional sources require more
labour and resource intensive to produce, however, requiring extra energy to refine,
resulting in higher production costs and up to three times more greenhouse gas
emissions per barrel (or barrel equivalent) on a "well to tank" basis or 10 to 45%
more on a "well to wheels" basis, which includes the carbon emitted from
combustion of the final product [11,12]. Moreover, oil extracted from these sources
typically contains contaminants such as sulfur and heavy metals that are energy-
intensive to extract and can leave tailings, ponds containing hydrocarbon sludge in
some cases [11,13].
Indian consumption of petroleum products also shows an alarming rise from
3.5mt in 1950-51 to 111mt in 2004-2005 and it may increase to 234mt in 2019-20 as
estimated by the Planning Commission of India. The combination of rising oil
consumption and relatively flat production has left India increasingly dependent on
imports to meet its petroleum demand. In 2010, India was the world’s fifth largest
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net importer of oil, largely depended on the Middle East countries and Africa
continent importing more than 2.2 million bbl/d or about 70 percent of consumption
and imported $82.1 billion worth of oil in the first three quarters of 2010 [14, 15].
Among the petroleum derived products, diesel fuel finds its application almost in all
areas viz. transportation, agriculture, commercial, domestic and industrial sectors for
the generation of power/mechanical energy [16] accounting for approximately 40
million tonnes constituting about 40% of the total petro-product consumption and
substituting even a small fraction of total consumption by alternative fuels will have
a significant impact on the economy and the environment.
a) Percentage of India’s oil imports, 2010 b) India’s oil production and consumption,
2000-2010.
1.2 Alternative fuel sources
The situation has led to the search for an alternative fuel, which should be not
only sustainable but also environment-friendly. Renewable fuels so far being
emerged are solar, wind, hydropower, tidal and wave energy, geo-thermal energy,
hydrogen fuel cell, alcohol, biogas, biomass, synthetic fuels, etc. As on 2010, only
about 16% of global energy consumption comes from renewable sources [17], 10%
from traditional biomass, which is mainly used for heating, and 3.4% from
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hydroelectricity. Other emerging renewables (small hydro, modern biomass, wind,
solar, geothermal and biofuels) accounted for another 3% and are growing very
rapidly. In recent years there has been a trend towards an increased
commercialization of various renewable energy sources.
Renewable energy share of global energy consumption, 2009.
Average annual Growth Rates of Renewable energy 2005-2010.
As for transportation sector, apart from vehicles using internal combustion
engine (ICE), researches for employing rechargeable battery as propulsion source are
under study. Instead of using fuels, alternate propulsion systems such as battery and
electric motors are also under investigation.
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1.3 Battery Electric Vehicles
A battery electric vehicle (BEV) is a type of electric vehicle that uses
chemical energy stored in rechargeable battery packs. BEVs use electric motors and
motor controllers instead of ICEs for propulsion. Recharging can be done using
electric grid which may be from solar, wind, hydropower, geothermal power, tidal
and wave power or from hydrogen fuel cell.
1.3.1 Solar Energy
Sun being the most powerful and prime source of energy, the radiation
reaching our earth can be harnessed for utilization as the best alternate source. The
total solar energy absorbed by Earth's atmosphere, oceans and land masses is
approximately 3,850,000 exajoules (EJ) per year [18]. The amount of solar energy
reaching the surface of the planet is so vast that in one year it is about twice as much
as will ever be obtained from all of the Earth's non-renewable resources of coal, oil,
natural gas and mined uranium combined [19]. Depending on geographical location,
the closer to the equator the more "potential" solar energy is available.
Broadly, solar technologies are characterized as either passive or active
depending on the way they capture, convert and distribute solar energy. Active solar
techniques include the use of photovoltaic panels and solar thermal collectors to
harness the energy. Passive solar techniques include orienting a building to the Sun,
selecting materials with favourable thermal mass or light dispersing properties, and
designing spaces that naturally circulate air. Solar energy technologies include solar
heating, solar photovoltaics, solar thermal electricity and solar architecture, which
can make considerable contributions to solve some of the most urgent problems the
world now faces. But the problem of consideration is though the source is renewable
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and readily available, the method to harness energy is costlier to be affordable by
developing and the under-developed countries.
1.3.2 Hydrogen Fuel Cell
Hydrogen is often mentioned as the energy source of the future. The steps in
using hydrogen as a transportation fuel consist in: 1) producing hydrogen by
electrolysis of water or by extracting it from hydrocarbons 2) compressing or
converting hydrogen into liquid form 3) storing it on-board a vehicle and 4) using
fuel cell to generate electricity on demand from the hydrogen to propel a motor
vehicle. Such vehicles convert the chemical energy of hydrogen to mechanical
energy either by burning hydrogen in an internal combustion engine, or by reacting
hydrogen with oxygen in a fuel cell to run electric motors. Hydrogen fuel does not
occur naturally on Earth and thus is not an energy source, but is an energy carrier.
Though it can also be produced from a wide range of sources such as wind/solar, it is
most frequently made from methane or other fossil fuels [20].
Hydrogen can be used in vehicles in two ways: a source of combustible heat
or a source of electrons for an electric motor. The burning of hydrogen is not being
developed in practical terms; it is the hydrogen fuel-cell electric vehicle which is
garnering all the attention. Hydrogen fuel cells create electricity fed into an electric
motor to drive the wheels. Hydrogen is not burned, but it is consumed. The
molecular hydrogen and oxygen's mutual affinity drives the fuel cell to separate the
electrons from the hydrogen, to use them to power the electric motor and to return
them to the ionized water molecules that were formed when the electron-depleted
hydrogen combined with the oxygen in the fuel cell.
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Hydrogen fuel cells are two times more efficient than gasoline and generate
near-zero pollutants. But hydrogen fuel cell suffers from several problems. A lot of
energy is wasted in the production, transfer and storage of hydrogen. Hydrogen
manufacturing requires electricity production. Hydrogen-powered vehicles require 2-
4 times more energy for operation than an electric car which does not make them
cost-effective. Besides, hydrogen has a very low energy density and requires very
low temperature and very high pressure storage tank adding weight and volume to a
vehicle and large investment in infrastructure that would be required to fuel vehicles
and the inefficiency of production processes.
1.3.3 Wind Energy
Wind power, as an alternative to fossil fuels, is plentiful, renewable, widely
distributed, clean, produces no greenhouse gas emissions during operation and uses
little land [21]. Any effects on the environment are generally less problematic than
those from other power sources. As of 2010 wind energy production was over 2.5%
of worldwide power, growing at more than 25% per annum, in which US ranks first
contributing about 27.6% [22]. The overall cost per unit of energy produced is
similar to the cost for new coal and natural gas installations [23].
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Top 10 countries by windpower electricity production, 2010.
Country
Windpower
production
(TWh)
% world total
United States 95.2 27.6
China 55.5 15.9
Spain 43.7 12.7
Germany 36.5 10.6
India 20.6 6.0
United Kingdom 10.2 3.0
France 9.7 2.8
Portugal 9.1 2.6
Italy 8.4 2.5
Canada 8.0 2.3
(rest of world) (48.5) (14.1)
World total 344.8 TWh 100%
But the magnets used in some types of wind turbine's generators contain rare-
earth minerals, specifically neodymium. While being fairly common, neodymium is
spread across the globe and major reserves of neodymium are very rare. The mining
of rare earth minerals and their use in wind turbines has environmental impacts [24,
25].
1.3.4 Geothermal energy
Geothermal energy is thermal energy generated and stored in the Earth. At
the core of the Earth, thermal energy is created by radioactive decay and
temperatures may reach over 9,000 degrees Fahrenheit (5000 degrees Celsius). Heat
conducts from the core to surrounding cooler rock. The high temperature and
pressure cause some rock to melt, creating magma convection upward since it is
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lighter than the solid rock. The magma heats rock and water in the crust, sometimes
up to 700 degrees Fahrenheit (370 degrees Celsius) [26].
Geothermal wells release greenhouse gases trapped deep within the earth, but
these emissions are much lower per energy unit than those of fossil fuels. As a result,
geothermal power has the potential to help mitigate global warming if widely
deployed in place of fossil fuels. But it has historically been limited to areas near
tectonic plate boundaries though geothermal power is reliable, sustainable and
environment-friendly [26].
1.3.5 Hydro Energy
Hydroenergy produced through the use of the gravitational force of falling or
flowing water is the most widely used form of renewable energy, accounting for 16
percent of global electricity consumption. Though it is environment-friendly and
affordable in terms of cost, it requires large reservoirs for the operation of
hydroelectric power stations resulting in submersion of extensive areas upstream of
the dams, destroying biologically rich and productive lowland and riverine valley
forests, marshland and grasslands. The loss of land is often exacerbated by habitat
fragmentation of surrounding areas caused by the reservoir [27].
1.3.6 Tidal and Wave Energy
Tidal energy is a form of hydropower that converts the energy of tides into
useful forms of power - mainly electricity. Among sources of renewable energy,
tidal power has traditionally suffered from relatively high cost and limited
availability of sites with sufficiently high tidal ranges or flow velocities, thus
constricting its total availability. Similarly, wave energy on the ocean surface was
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converted to electrical energy. Both the technologies involve higher cost for
conversion.
A battery electric vehicle will take 12 to 24 hours for a full charge on a
standard 120-volt outlet, while most models will take three to six hours to fully
charge on a 240-volt rated charging unit.
1.4 Hybrid Electric Vehicles (HEVs) and Plug-in-Hybrid Electric Vehicles
For adapting a cheaper technology, hybrid electric vehicles which combine a
conventional ICE propulsion system with an electric propulsion system, can be used.
These vehicles do not have to be plugged in to a power source. As the engine runs,
power is transferred into the batteries for storage and later used by the electric motor.
Hybrid vehicles can use an internal combustion engine running on biofuels, such as a
flexible-fuel engine running on ethanol or engines running on biodiesel. HEVs are
more expensive (the so-called "hybrid premium") than pure fossil-fuel-based ICE
vehicles, due to extra batteries, more electronics and in some cases other design
considerations.
On the other hand, plug-in hybrid electric vehicles (PHEVs) use batteries to
power an electric motor and use another fuel, such as biodiesel, to power an internal
combustion engine or other propulsion source. Using electricity from the grid to run
the vehicle some or all of the time, reduces operating costs and petroleum
consumption relative to conventional vehicles. PHEVs might also produce lower
levels of emissions, depending on the electricity source. But the major drawbacks for
using such vehicles are the requirement of special infrastructure for recharging
purposes with safety assurance and high cost of batteries not affordable by
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developing countries. Also most plug-in hybrids will take four to six hours to fully
charge on a standard 120-volt outlet.
a) Plug-in hybrid electric vehicle b) Battery electric vehicle c) Conventional vehicle.
So in developing countries, fuels of bio-origin, such as biogas, alcohol,
vegetable oils, biomass, biogas, synthetic fuels, etc. are gaining momentum. Such
fuels can be used either directly or with some sort of modification before they are
used as substitute of conventional fuels. In view of protecting our environment
against the green house gases and the concern for long-term supplies of conventional
diesel fuels, it becomes necessary to develop alternative fuels comparable with
conventional fuels.
1.5 CNG as Energy
Compressed natural gas (CNG) is a fossil fuel substitute for gasoline (petrol),
diesel or propane/LPG. Although its combustion does produce greenhouse gases, it
is a more environmentally clean alternative to those fuels, and it is much safer than
other fuels in the event of a spill (natural gas is lighter than air and disperses quickly
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when released). CNG may also be mixed with biogas, produced from landfills or
wastewater, which doesn't increase the concentration of carbon in the atmosphere.
CNG is made by compressing natural gas (which is mainly composed of
methane), to less than 1% of the volume it occupies at standard atmospheric
pressure. It is stored and distributed in hard containers at a pressure of 200-248 bar
(2900-3600 psi), usually in cylindrical or spherical shapes. CNG's volumetric energy
density is estimated to be 42% of liquefied natural gas's (because it is not liquefied),
and 25% of diesel's [28]. The cost of this conversion is a barrier for CNG use as fuel.
1.6 LNG as Energy
Liquefied natural gas or LNG is natural gas (predominantly methane) that
has been converted to liquid form for ease of storage or transport. Liquefied natural
gas takes up about 1/600th the volume of natural gas in the gaseous state. It is
odorless, colorless, non-toxic and non-corrosive. Hazards include flammability,
freezing and asphyxia. The liquefaction process involves removal of certain
components such as dust, acid gases, helium, water and heavy hydrocarbons, which
could cause difficulty downstream. The natural gas is then condensed into a liquid at
close to atmospheric pressure (maximum transport pressure set at around
25 kPa/3.6 psi) by cooling it to approximately −162 °C.
LNG achieves a higher reduction in volume than compressed natural gas
(CNG) so that the energy density of LNG is 2.4 times that of CNG or 60% of that of
diesel fuel [29]. This makes LNG cost efficient to transport over long distances
where pipelines do not exist. Specially designed cryogenic sea vessels (LNG
carriers) or cryogenic road tankers are used for its transport. Although it is more
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common to design vehicles to use compressed natural gas, its relatively high cost of
production and the need to store it in expensive cryogenic tanks have prevented its
widespread use in commercial applications.
1.7 Bioethanol as energy source
Bioethanol is a source of renewable energy that can be produced from
agricultural feedstocks. It can be made from very common crops such as sugarcane,
potato, manioc and corn and also from cellulosic fibres a major and universal
component in plant cell walls. There has been considerable debate on how useful
bioethanol will be in replacing gasoline. Concerns about its production and use relate
to increased food prices due to the large amount of arable land required for crops as
well as the energy and pollution balance of the whole cycle of ethanol production,
especially from corn [30].
There are several problems with the use of ethanol as an alternative fuel.
First, it is costly to produce and use. As on 1987 price, it costs 2.5-3.75 times as
much as gasoline. Another problem is that ethanol has a smaller energy density than
gasoline. It takes about 1.5 times more ethanol than gasoline to travel the same
distance. However, with new technologies and dedicated ethanol-engines, this is
expected to drop to 1.25 times. Moreover, the process for conversion of crops to
ethanol is relatively inefficient because of the large water content of the plant
material. There is legitimate concern, especially in developing countries, that using
land for ethanol production will compete directly with food production. Most
important disadvantage is that some of the ethanol will be partially oxidized and
emitted as acetaldehyde, which reacts in air to eventually contribute to the formation
of ozone. Also the waste product from ethanol production, called swill, though can
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be used as a soil conditioner on land, it is extremely toxic to aquatic life causing
disposal problem.
1.8 Vegetable oils as Fuel
The concept of using vegetable oils as fuel source emerged well before the
1970s when Rudolf Diesel took interest in finding an ideal fuel which ensures
complete combustion. Rudolf Diesel rightly stated in the year 1912, “The use of
vegetable oils for engine fuels may seem insignificant today. But such oils may
become in the course of time as important as petroleum and the coal tar products of
the present time.” As predicted by him, the inventor of diesel engine, it has now
gained a wide-spread momentum. Rudolf Diesel run his first engine only with
(peanut) vegetable oil, but later due to the cheaper price of petroleum oil that time,
he designed the engine for working with diesel. So the use of vegetable oils as fuel
source, dated long back but only in times of emergency. Now it has gained a
renewed focus due to depleting petroleum reserves and environmental concerns.
Vegetable oil/animal fat is made up of one mole of glycerol and three moles
of fatty acids, referred to as triglycerides. They differ in the nature of their carbon
chain and the amount of unsaturation. They are highly viscous, water
insoluble/hydrophobic and contain larger fractions of free fatty acids apart from
phospholipids, sterols, water, odorants and other impurities [31]. These qualities
impede their direct use in engines and require modifications.
The advantages of vegetable oils as diesel fuel are (1) liquid nature
portability (2) heat content (3) ready availability and (4) renewability. But the
problems appear only after the engines have been operating on vegetable oils for a
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long period of time, especially with direct-injection engines. The problems include
(1) coking and trumpet formation on the injectors to such an extent that fuel
atomization does not occur properly or is even prevented as a result of plugged
orifices (2) carbon deposits (3) oil ring sticking and (4) thickening and gelling of the
lubricating oil as a result of contamination of the vegetable oils [32]. These
disadvantages ultimately lead to the idea of modifying the chemical nature of
vegetable oils to meet fuel specifications.
1.9 Biodiesel
Biodiesel as its name implies is obtained from biological sources like
vegetable oils and animal fats. They are the simple alkyl esters of long chain fatty
acids which are obtained from glyceride sources by employing appropriate methods
for production. Biodiesel has been raised as a promising fuel nowadays due to its
multiple advantages viz.
· The use of biodiesel in conventional diesel engines results in substantial
reduction of unburnt hydrocarbons, carbonmonoxide and particulate matters
(but NOx about 2 % higher)
· Biodiesel has almost no sulphur (0.05%), no aromatics and has about 11%
built-in oxygen which helps in better combustion.
· Its higher Cetane number (>51 as against 48 in diesel) improves the ignition
quality.
· Require very little or no engine modifications because biodiesel has
properties similar to petro-diesel fuels.
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· It can be stored just like the petro-diesel fuel and hence does not require
separate infrastructure.
· Its higher flash point (>100 as against 48 in diesel) is good from safety point
of view.
· Biodiesel can be blended in any ratio with the petro-diesel.
Worldwide production and consumption of Biodiesel.
Apart from these, glycerol a by-product obtained during the production of
biodiesel can be purified which can serve for many industrial processes including the
manufacture of drugs, cosmetics, toothpastes, urethane foam, synthetic resins and
ester gums [33]. Besides, the crude glycerol obtained as by-product can be used for
biogas production [34] and can also serve as a carbon source for some fermentation
processes [35].
As per the United States Energy Information Administration, in 2010, the
production of biodiesel was 294.69 thousand barrels per day. The consumption rate
of biodiesel is increasing rapidly [36] and these biodiesel plants are mainly
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operational in America, France, Italy, Hungary, Germany and Czechslovakia for
commercial production.
1.10 Sources of Biodiesel
Vegetable oils (both fresh and used) and animal fats [37] are the important
sources of biodiesel. Biodiesel production from various feedstocks worldwide,
includes soybean [38], olive, coconut, sesame, hazelnut, walnut, cotton, corn,
sunflower, canola [39], palm, jatropha [40], mustard [41], yellow horn [42], karanja
[43], mahua [44], rubber [45], moringa [46] and neem [47]. Besides, researches are
under progress in advocating algae [48] and pisces [49] as a possible source. Apart
from these, oil from halophytes such as Salicornia bigelovii [50], which can be
grown using saltwater in coastal areas where conventional crops cannot be grown,
with yields equal to that of soybeans and other oilseeds grown using freshwater
irrigation, is under study.
1.11 Non-edible vs Edible oil sources of Biodiesel
Of the vegetable oils both edible and non-edible can be used to produce
biodiesel. Edible oils of rapeseed, soybean, palm, sunflower, coconut and linseed are
used as the main sources for biodiesel in Europe and North America [51]. It is not
economic to use these oils in a populous country like India as there exists a huge gap
between production and demand [52]. However, it is feasible to exploit non-edible
oil sources which may not affect the food production. Non-edible oil seeds of
Jatropha curcus [53], Xanthoceras sorbifolia [42], Sapindus mukorossi [54],
Pongamia pinnata [55], Moringa oleifera [46], Calophyllum inophyllum [56],
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Nicotiana tabacum [57] and Hevea brasiliensis [45] are some of the potential
sources for biodiesel.
In search for an efficient alternate fuel, two new sources – Polyalthia
longifolia and Annona Squamosa have been attempted as feedstocks in this study for
biodiesel production. The sources being completely non-edible, the potentiality of
the oils extracted from the dried and powdered seeds by hexane and chloroform
solvents in the ratios 2:1 and 3:1 analysed for biodiesel production. The oil extracted
from Polyalthia get solidified to a gelly mass even at room temperature (≈30oC)
when stored for a few weeks. Considering the oil nature, oil content and poor
industrial application for the plantation, the feedstock discarded. While for the latter,
the oil content being lesser with lack of potential industrial application for the
plantation, it was also dropped out. Rubber being a common plantation with oil
content of range 35-45% [58] and good industrial as well as environmental
applications, it was chosen as a potential feedstock in this study for biodiesel
production.
Seeds of Polyalthia Longifolia Seeds of Annona Squamosa
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Acid values of some common vegetable oils are analysed where sunflower
oil shows the minimum and rubber seed oil exhibits the maximum.
Acid value of some vegetable oils.
Vegetable oils Acid value (mgKOH/g)
Helianthus annuus (Sunflower) < 1.0
Polyalthia Longifolia -
Annona Squamosa 4.9
Pongamia Pinnata 25.75
Jatropha Curcus 5.56
Hevea Brasiliensis (Natural Rubber) 46.41
1.12 Hevea Brasiliensis as a potential source of Biodiesel
India is one among the top ten rubber producing countries and Kerala state
leads rubber plantation in India. Though many plant species produce natural rubber,
considerations of quality and economics limit the source of natural rubber to one
species, namely Hevea brasiliensis. It is a native of the Amazon basin and
introduced from there to countries in the tropical belts of Asia and Africa during late
19th century. Interestingly, rubber plantations have greater carbon sequestration
potential which is roughly in the range of 7-9 tC per hectare per year. This is much
greater than most of the tree species according to Rubber Research Institute of India.
Kyoto protocol provides about 15 US $ per tonne carbon sequestration which
encourages developing countries to cultivate more rubber [59].
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Hevea brasiliensis, also known as the Para rubber tree after the Brazilian port
of Para, is a quick growing, fairly sturdy, perennial tree of a height of 25 to 30
metres. The young plant shows characteristic growth pattern of alternating period of
rapid elongation and consolidated development. The leaves are trifoliate with long
stalks. The tree is deciduous in habit and winters from December to February in
India. Refoliation is quick, and copious flowering follows. Flowers are small but
appearing in large clusters.
a) Rubber plantation in Kanyakumari District b) Rubber seeds.
Fruits are three lobed, each holding three seeds, quite like castor seeds in
appearance but much larger in size and each weighs 2 to 4g. The seeds, which fall
on the ground, deteriorate very rapidly due to moisture and infection. These lead to
rapid increase in the free fatty acid (FFA) content of the oil. Therefore, it is essential
to collect the seeds as quickly as possible and dry them, so as to reduce the moisture
less than 5% in order to arrest increase in the FFA. The oil content in dried kernel
varies from 35 to 45% [58]. The rubber seed oil is normally obtained by expelling
the seeds from the fruits. Depending on the pre-extraction history of the kernels, the
colour of the oil ranges from water white to pale yellow for low FFA content (about
5%) to dark colour for high FFA content (about 10 to 40%).
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The milky serum or latex of the rubber tree is one of the important raw
materials available for making various kinds of products in heavy industries such as
motor and vehicle industry, kitchenware and houseware while the rubber seeds could
be utilized as a promising source of non-edible oil. The rubber seed oil can be used
in the manufacture of inferior quality laundry soap, paints and varnishes, epoxidised
oil used in the preparation of anti-corrosion coatings, adhesives, and alkyl resin
coatings, grease and tanning of leather. The rubber seed cake with rich protein
content is used as cattle/poultry feed. With all these utilities, rubber seed oil could
emerge as a potential source of biodiesel tomorrow. Moreover, the prime aspect in
the cost of production of biodiesel is quite because of the costlier nature of the
vegetable oil to be used as source constituting between 70-85% [60-62]. The rubber
seed oil used in the present work is readily available in the experimental locality and
is very cheap.
1.13 Process of Biodiesel Production
Biodiesel can be obtained by four possible treatments viz. dilution, micro-
emulsification, pyrolysis and transesterification [31]. Dilution is the simplest method
where vegetable oils are blended with diesel at various proportions, a blend of 20%
vegetable oil and 80% diesel being successful. Used cooking oil can be filtered and
blended with diesel fuel in the ratio 95:5 [63]. Peterson et al. (1983) have used a
blend of 70/30 winter rapeseed oil and No.1 diesel to power a small single cylinder
diesel engine [64]. A blend of sunflower oil and diesel in the ratio 25:75 has been
successfully used [65] by Ziejewski et al. (1986).
The disadvantages of using vegetable oils directly have lead to the
development of another technique called micro-emulsification, where the high
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viscosity of vegetable oil gets reduced. Micro-emulsification is defined as a colloidal
equilibrium dispersion of optically isotropic fluid microstructures with dimensions
generally in the range 1-150 nm formed spontaneously from two normally
immiscible liquids and one or more ionic or non-ionic amphiphiles [66]. Micro-
emulsions are prepared with solvents such as methanol, ethanol and
1-butanol. Ziejewski et al. (1984) have prepared an emulsion of 53% (v/v) alkali
refined-winterised sunflower oil [67], 13.3% (v/v) 190- proof ethanol and 33.4%
(v/v) 1-butanol. A micro-emulsion prepared by blending soybean oil, methanol,
2-octanol and cetane improver in the ratio of 53.7:13.3:33.3:1.0, has passed the 200
h Engine Manufacturers Association test (EMA test) [68].
Ziejewski et al. (1983) have reported that the engine performance were the
same for micro-emulsions of 53% sunflower oil and the 25% blend of sunflower oil
in diesel [69]. Though micro-emulsions reduce viscosities and improve spray
patterns [70], it has disadvantages like irregular injector needle sticking, incomplete
combustion, increase of lubricating oil viscosity [67], carbon and lacquer deposits on
the injector tips, intake valves and tops of the cylinder liners [71]. Micro-emulsion is
not a very attractive solution to reduce viscosity.
Another technique pyrolysis, involving heating the vegetable oil in the
absence of air but with a catalyst develops cleavage of chemical bonds to yield
smaller molecules [72]. Soybean oil has been thermally decomposed and distilled in
air and nitrogen sparged with a standard ASTM distillation apparatus [73, 74] by
Niehaus et al. (1986) and Schwab et al. (1988). Billaud et al. (1995) have pyrolysed
rapeseed oil to produce a mixture of methyl esters in a tubular reactor between 500
and 850oC in nitrogen atmosphere [75]. The main components of pyrolysed oil are
25
alkanes and alkenes, which accounted for approximately 60% of the total weight and
carboxylic acids which accounted for another 9.6-16.1%
[74, 76].
Pyrolytic chemistry is difficult to characterize because of the variety of
reaction products that may be obtained from the reactions that occur and the
equipment used for the method is also expensive [32]. Though pyrolysed vegetable
oil possesses acceptable amount of sulphur, water and sediments it shows
unacceptable ash, carbon residues and pour point [77]. This lead to the development
of another method, transesterification.
1.14 Transesterification
Transesterification or alcoholysis is a better method to reduce viscosity and
thereby improve engine-performance [78]. Its emergence can be dated to as early as
1846, when Rochieder described glycerol preparation through ethanolysis of castor
oil [79]. Transesterification involves displacement of an alcohol from the
triglycerides by another alcohol in a process similar to hydrolysis, resulting in the
formation of another alkyl ester commercially called biodiesel.
Methanol and ethanol are used most frequently for achieving
transesterification. However, methanol is preferred over ethanol due to its lower cost
and structural advantages with higher polarity and smaller size and it can quickly
react with triglycerides and sodium hydroxide. Though 3:1 ratio of alcohol to
triglyceride is enough to complete a transesterification stoichiometrically, higher
amount of alcohol is needed in practice to drive the equilibrium to a maximum ester
yield. Catalysts used for transesterification of triglycerides can be classified as acid,
26
alkali or enzyme among which alkali catalysts are more effective [77]. Or even
heterogenous inorganic catalysts can be used but require temperature above 200oC to
achieve a conversion above 90%. The acids used may be sulphuric acid, sulphonic
acid or hydrochloric acid. The common alkali catalysts are sodium hydroxide,
potassium hydroxide, carbonates, sodium alkoxide and potassium alkoxide. Alkali-
catalyzed transesterification proceeds 4000 times faster than that catalyzed by the
same amount of an acid catalyst [80].
For an alkali-catalyzed transesterification, the glycerides and alcohol must be
substantially anhydrous because water causes a partial reaction change to
saponification, which produces soap [81]. The soap formed reduces the ester yield
and hinders the separation of glycerol since it forms an emulsion. Moreover, free
fatty acid should be less than 2% to get maximum yield for alkali-catalyzed
transesterification which otherwise leads to saponification of the ester. Alternatively,
acid catalyst [82, 83] can be used when FFA content is greater, since it is more
tolerant to FFAs but it is time consuming as the reaction take 48-96 hours even at the
boiling point of the alcohol, and a high molar ratio of alcohol is needed (20:1 w/w to
the oil) [84]. Another alternate is the enzyme which is quite expensive. These
drawbacks switches back to the use of alkali catalysts for the processing of vegetable
oils in the production of fatty acid alkyl ester (biodiesel).
1.15 Base-catalyzed Transesterification
Transesterification using base catalyst is quite considered as an economic as
well as time saving method for biodiesel production (Scheme 1.1). But there are
some parameters to be considered in this process to get good yield and quality.
27
1.15.1 Water
Water content is the major problem in biodiesel production using base-
catalyzed transesterification. Saponification reaction competes with
transesterification in presence of water [85]. Even a small quantity of water in the
source or methanol will support saponification reaction (Scheme 1.2) to dominate
over transesterification. Ultimately washing will be difficult due to the formation of
emulsion, making the separation process of biodiesel difficult.
Scheme 1.1 Base-catalyzed Transesterification of triglycerides.
Scheme 1.2 Saponification of triglycerides.
28
1.15.2 Free Fatty Acid content (FFA)
Second factor to be considered is the free fatty acid content of the source
used for biodiesel production [85, 86]. To get high yield of biodiesel, FFA content
should be normally within a limit of 0.5% [87]. Base-catalyzed transesterification
can be processed in oils having FFA content upto 2% of FFA [45] with a good yield,
above which saponification reaction will dominate reducing the yield of desired
product since soap formation results in emulsification. To reduce FFA, esterification
is done using acid catalyst after which transesterification can be done.
1.15.3 Phospholipids and Glycerides
Another problem is the presence of phospholipids, a form of resinous
compounds in the source oil. Presence of phospholipids increases the viscosity of the
source material, whether it may be the oil or the biodiesel produced. Phospholipids
are the products of triglyceride with one of the substituents as phosphatide instead of
the fatty acid chain. Phospholipids are of two types – hydratable and non-hydratable
in which hydratable gums can be removed by hot water while the other has to be
removed by acids like phosphoric acid or citric acid [88]. Besides, phospholipase an
enzyme can also be used to cleave the phosphatide chain via hydrolysis. In base-
catalyzed transesterification, phospholipids tend to hinder biodiesel separation since
it forms emulsion. Hence prior to transesterification process, degumming should be
done to remove the phospholipids by using acids such as phosphoric acid or citric
acid.
29
Incomplete reaction results in the formation of mono- and di-glycerides
which act as emulsifying agents [89] resulting in emulsification, making the
purification process of biodiesel still more difficult.
1.16 Transesterification via Acid-catalyzed Esterification
If the free fatty acid content is above 2% in vegetable oil, acid-catalyzed
transesterification process can be followed to produce biodiesel. Acid-catalyzed
transesterification is not suffered by the problems of FFA and water since there
won’t be any soap formation. But the reaction time is very long (48–96 hrs), that
leads to the development of a two step process i.e., transesterification via acid-
catalyzed esterification. Initially the vegetable oil is pre-heated to remove moisture
after which the free fatty acids are converted to its esters to its minimum. The oil is
then transesterified by using an alkali catalyst, but the product still contains tri-, di-
and mono- glycerides along with fatty esters, glycerol, alcohol and catalyst
depending on the completion of the reaction. Obtaining pure esters is not easy [90].
The mono glycerides cause turbidity in the mixture of esters. The glycerol which is
obtained as a by-product should be recovered by gravitational settling or
centrifuging.
1.17 Ultrasonic Energy for Biodiesel Production
Biodiesel, the fatty acid alkyl ester, is gaining more and more attention in
recent years since it may be at least a partial answer to the world’s need for
renewable energy. For the processing of biodiesel, stoichiometrically a 3:1 molar
ratio of alcohol to triglyceride is necessary. In practice, excess amount of alcohol is
added to enhance the biodiesel yield. The transesterification process can be affected
30
by many factors, including the molar ratio of alcohol to oil, catalyst type and
concentration, reaction time, stirring intensity and temperature. Fats and alcohols are
not totally miscible, so their reaction takes place at the interface and it is a very slow
process. To strengthen the mass transfer between liquid-liquid heterogeneous
systems, ultrasound can serve as a useful tool which has entered the popular
consciousness. It is known that ultrasound can generate cavitation that can efficiently
improve the biodiesel production. Chemical reactions requiring stringent conditions
can be efficiently carried out using cavitation [90]. The feasibility and the efficiency
of ultrasonic mixing have been demonstrated by a number of researchers to improve
biodiesel production [91, 92-98].
Principle of ultrasonication.
Cavitation refers to generation, subsequent growth and collapse of cavities
resulting in very high energy densities of the order of 1 to 1018 kW/m3 [91]. The
cavitation bubbles produced by ultrasound expand with each cycle of compression
and rarefraction until they reach an unstable size resulting in violent collapse.
31
Collapse of the cavitation bubbles cause intensive shock waves in the surrounding
liquid and result in the formation of liquid jets of high velocity. Strong shock waves
generated and the liquid jets formed during the collapse of bubbles further disrupt
the phase boundary, enhancing the mixing efficiency between immiscible
triglycerides and alcohol. By applying the ultrasound, biodiesel production cost can
be reduced significantly due to its high efficiency and low energy input
[96-98].
1.18 Fuel Properties
Apart from being renewable, non-toxic and environment-friendly, an
efficient fuel must possess acceptable properties a fuel must have. A good fuel must
have high energy content and it should be readily combustible. Combustion can be
made readily only when enough fuel reaches the injection pump which is possible
when the viscosity is lower and cetane number is higher [33, 99, 100]. Moreover if
there is water contamination, it will lead to premature damage to the fuel injection
system and also contaminants like sulphur result in metal corrosion for which copper
components are more sensitive [33].
In biodiesel derived from vegetable oils, there may be presence of mono-,di-
and tri-glycerides due to incomplete reaction. They will further contribute water
content by solubilizing more water since they act as emulsifier. In addition, the
glyceride content will cause engine clogging and deposition along with free glycerin
and free fatty acid [101]. Increased water content enhances degradation of the fatty
acid alkyl esters reducing its shelf life. Regarding the safety of fuel handling, it must
have high flashpoint and fire point. Lower flash point may lead to fire hazards
mainly during transportation.
32
To ensure suitability of usage in different climatic conditions, the cold flow
properties are helpful so that based on the climatic condition of a country the
suitability of a fuel can be addressed [102]. Fuels in general will have the tendency
to get auto-oxidise on storage and the ease of oxidation is based on its chemical
composition. On oxidation, biodiesel tends to form acids, peroxides and polymers
[103] which will result in fuel atomization problem due to engine deposits and
clogging. So a good fuel must have higher oxidative stability.
1.19 Storage Stability
One of the main criteria for the quality of a biofuel is its storage stability.
Biodiesel, an alternative diesel fuel derived from transesterification of vegetable oils
or animal fats, is composed of saturated and unsaturated long-chain fatty acid alkyl
esters. Vegetable oil derivatives especially tend to deteriorate owing to hydrolytic
and oxidative reactions. Their degree of unsaturation makes them susceptible to
thermal and/or oxidative polymerization, which may lead to the formation of
insoluble products that cause problems within the fuel system, especially in the
injection pump [104]. When exposed to air during storage, autoxidation of biodiesel
can cause degradation of fuel quality by adversely affecting properties such as
kinematic viscosity, acid value and peroxide value [105].
Storage stability is influenced by various parameters like temperature, metal
contaminants, moisture, air and electromagnetic radiation [104,106, 107].
Contamination due to metals is possible depending on the storage container. Since
metals can catalyze oxidation with oxygen, it will adversely effect deterioration of
the fuel. So it is important to fix the limit and condition of storage for the future use
of the fuel to assure engine life.
33
1.20 Antioxidants as Additives
The quality of a fuel can also be signified by testing its storage stability. To
ensure industrial production and commercialization, a fuel must be able to sustain
storage for a reasonable time. In order to enhance the shelf life of a fuel, additives
are acceptable without affecting its fuel quality and standard. Stability of a fuel is
mainly attributed to the extent of oxidation which results in insoluble deposition and
acid formation seriously affecting fuel atomization and engine life [108]. To prevent
such oxidation, antioxidants as additives are advisable so as to improve storage
stability.
Mostly synthetic antioxidants are being used due to their greater efficiency.
A number of antioxidants are commercially available which include tert-
butylhydroquinone, pyrogallol, butylated hydroxytoluene, butylated hydroxyanisole,
di-tert-butylphenol and propyl gallate [109-113]. Mechanism of inhibition of
oxidation involves free radical intermediates [40, 114-116]. Apart from synthetic
antioxidants, a number of natural antioxidants [117-119] are available which can be
loaded with fuels to inhibit oxidation. Mostly polyphenols and flavonoids in
vegetables and fruits possess antioxidant behaviour fighting effectively against
oxidation. Among the natural sources - berries, vegetables, fruits and spices, berries
and green tea are reported to have high antioxidant property due to their rich
polyphenols and flavonoid content [114, 120-124]. In some plants, even the non-
edible portions like bark [125], roots [115] and peel of fruits are exhibiting good
antioxidant activity. Pomegranate, a common species has its peel [126] with good
antioxidant nature which is utilized in the present work along with green tea to
improve the oxidative stability of biodiesel obtained.
34
1.21 Environmental Concern
Emissions from diesel engines seriously threaten the environment and are
considered to be one of the major sources of air pollution. These pollutants impact
on the ecological systems, leading to environmental problems, and carry
carcinogenic components that significantly endanger the health of human beings.
They can cause serious health problems, especially respiratory and cardio-vascular
problems. Increasing worldwide concern about combustion-related pollutants, such
as particulate matter (PM), oxides of nitrogen (NOx), carbonmonoxide (CO), total
hydrocarbons (THC), acid rain, photochemical smog and depletion of the ozone
layer have led several countries to regulate emissions and give directives for
implementation and compliance.
Average biodiesel emissions according to EPA.
Emission Type B100 B20
Regulated
Total Unburned Hydrocarbons Carbonmonoxide
Particulate matter NOx
-67% -48%
-47% +10%
-20% -12%
-12% +2% to -2%
Non-Regulated
Sulfates PAH (Polycyclic Aromatic Hydrocarbons)**
nPAH (nitrated PAH)** Ozone potential of speciated HC
-100%
-80% -90% -50%
-20%*
-13% -50%***
-10%
*Estimated from B100 result
**Average reduction across all compounds measured ***2-nitrofluorine results were within test method variability.
Biodiesel obtained from renewable sources is non-toxic and biodegradable.
Biodiesel burns clean which lessens its environmental impact. It significantly
reduces greenhouse gas emissions and toxic air pollutants. Since the plantation
35
consumes carbondioxide for photosynthesis, it neutralizes carbon emission
effectively and was recommended by Environmental Protection Agency (EPA).
Sulphur emission is eliminated and polyaromatic hydrocarbons which are
carcinogenic are reduced to minimum of 20-10% [127]. But the only problem is the
increase in NOx emission mainly due to higher oxygen content, different injection
characteristics and presence of high degree of unsaturation in biodiesel [128, 129].
To reduce NOx emission, biodiesel blends can be used or cetane improvers can also
be a choice since EPA report shows that higher cetane number controls NOx
emission [127].
1.22 Problem statement
The scope of this work is to produce an efficient alternative environment-
friendly fuel from a cheap and readily available source (rubber seed oil) in a cost
effective method, with the following objectives.
1. Production of biodiesel from Hevea brasiliensis seed oil adopting an efficient
method.
2. Optimizing the method of production of biodiesel by efficient techniques
(ultrasonication and magnetic stirring).
3. Analysing the biodiesel characteristics by suitable techniques.
4. Improving the storage stability of the biodiesel by suitable additives.
References
36
1. US Energy Information Administration (2004). Green house gases, climatic
change and energy. Retrieved August 28, 2012: www.eia.doe.gov/oiaf/
1605/ggccebro/chapter1.html.
2. Zimov, S.A., Schuur, E.A.G., & Chapin, F.S. (2006). Climate change:
Permafrost and the global carbon budget. Science 312(5780), 1612-1613.
3. Shakhova, N., Semiletov, I., & Panteleev, G. (2005). The distribution of
methane on the Siberian Arctic shelves: Implications for the marine methane
cycle. Geophysical Research Letters 32(9), L09601.
4. Gabbard, A. (2011). Coal Combustion: Nuclear Resource or Danger. Retrieved
August 24, 2012: www.ornl.gov/info/ornlreview/rev26-34/text/colmain.html.
5. Bredenberg, A. (2012). The Damage Done in Transportation - Which Energy
Source Will Lead to the Greenest Highways. Retrieved August 24, 2012:
www.news.thomasnet.com/green_clean/2012/04/30/the-damage-done-in-
transportation-which-energy-source-will-lead-to-the-greenest-highways/.
6. Enerdata (2012). Global Energy Statistical Yearbook 2012. Retrieved August
24, 2012: www.yearbook.enerdata.net/.
7. US Energy Information Administration (2010). EIA reserves estimates.
Retrieved August 24, 2012: www.eia.doe.gov/emeu/international/reserves.
html.
8. Thomas, C.E. (2009). Introduction to Process Technology (3rd ed.), Cengage
Learning, Canada.
9. Organisation of the Petroleum Exploring Countries (2011). OPEC Share of
World Oil Reserves 2010. Retrieved August 24, 2012: www.opec.org/
opec_web/en/data_graphs /330.htm.
37
10. Indexmundi (2012). World Crude Oil Production and Consumption by Year.
Retrieved August 24, 2012: www.indexmundi.com/energy.aspx?
region=xx&product=oil&graph =production+consumption.
11. Weber, B. (2009). Alberta's oilsands: well-managed necessity or ecological
disaster. Retrieved August 24, 2012: www.mjtimes.sk.ca/Canada--
World/BusinessWorld/Business/2009-12-10/article-243834/Albertas-oilsands: -
well-managed-necessity-or-ecological-disaster%3F/1.
12. Duarte, J. (2006). Canadian Tar Sands: The Good, the Bad, and the Ugly.
Retrieved August 24, 2012: www.rigzone.com/news/article.asp?a_id=30703.
13. Weissman, J.G., & Kessler, R.V. (1996). Downhole heavy crude oil
hydroprocessing. Applied Catalysis A: General 140(1), 1-16.
14. US Energy Information Administration (2011). Independent Statistics and
Analysis. Retrieved September 13, 2012: www.eia.gov/countries/
cab.cfm?fips=IN.
15. Ramakrishnan, V. (2010). Rupee Rally Falters as Oil Rises to Two-Year High.
Retrieved September 1, 2012: www.businessweek.com/news/2010-12-07/rupee-
rally-falters-as-oil-rises-to-two-year-high- india-credit.html.
16. Biswas, S., Kaushik, N., & Srikanth, G. (2009). Biodiesel: Fuel for the Future.
Technology Information, Forecasting and Assessment Council, Department of
Science and Technology, India. Retrieved August 24, 2012: www.tifac.org
.in/index.php?option=com_content&view=article&id=776:biodiesel-fuel-for-
thefuture&catid=120:publication-bioprocess-a-bioroducts&Itemid=1380.
17. REN21 (2011). Global Status Report. Retrieved August 24, 2012:
www.ren21.net/Portals/97/documents/GSR/GSR2011_Master18.pdf.
38
18. Wikipedia (2012). Solar Energy. Retrieved August 24, 2012: www.en.
wikipedia.org/wiki/Solar_energy.
19. Smil, V. (2005). Energy at the Crossroads: Global Perspectives and
Uncertainties. The MIT Press, USA.
20. Wikipedia (2012). Hydrogen Fuel. Retrieved September 13, 2012: www.en.
wikipedia.org/wiki/Hydrogen_vehicle.
21. Fthenakis, V., & Kim, H.C. (2009) Land use and electricity generation: A life-
cycle analysis. Renew. Sust. Energ. Rev. 13(6-7), 1465-1474.
22. Observ'ER (2011). Worldwide Electricity Production From Renewable Energy
Sources: Stats and Figures Series: Thirteenth Inventory. Retrieved September
13, 2012: www.energies-renouvelables.org/observ-er/html/ inventaire/pdf/13e-
inventaire-Chap02.pdf.
23. Wikipedia (2012). Wind Power. Retrieved August 24, 2012: www.en.
wikipedia.org/wiki/Wind_power.
24. Energy Information Administration (2006). International Energy Outlook,
DOE/EIA-0484. Retrieved September 13, 2012: www.eia.doe.gov/
oiaf/ieo/index.html.
25. Bogo, J. (2007). Popular Mechanics. How the Deadliest Wind Farm Can Save
the Birds: Green Machines. Retrieved September 14, 2012:
www.popularmechanics.com /science/environment/green-energy/4222351.
26. Nemzer, J. (2012). Geothermal heating and cooling. Retrieved September 14,
2012: www. geothermal.marin.org/.
27. Haugan, G.T. (2013). The New Triple Constraints for Sustainable Projects,
Programs, and Portfolios. CRC press, USA.
39
28. Wikipedia (2012). Compressed Natural Gas. Retrieved September 13, 2012:
www.en. wikipedia.org/wiki/Compressed_natural_gas.
29. Envocare (2012). Environment, Recycling, Ethical Investment, Alternative
Energy: Liquefied Petroleum Gas (LPG), Liquefied Natural Gas (LNG) and
Compressed Natural Gas (CNG). Retrieved September 13, 2012:
www.envocare.co.uk/lpg_lng_cng.htm.
30. Seleghim, P. (2011). Developing an integrated agro-industrial model for the
sustainable production and conversion of biomass into biofuels and added value
products, Energy use of biomass: a challenge for machinery manufacturers,
Proceedings of the 22nd members' meeting, Club of Bologna, Hannover,
Germany.
31. Demirbas, A. (2003). Biodiesel fuels from vegetable oils via catalytic and non-
catalytic supercritical alcohol transesterifications and other methods: a survey.
Energy Conversion and Management 44, 2093-2109.
32. Ma, F., & Hanna, M.A. (1999). Biodiesel production: a review. Bioresource
Technology 70, 1-15.
33. Knothe, G., Van Gerpen, J., & Krahl, J. (2005). The biodiesel handbook: The
basics of diesel engines and diesel fuels. AOCS press, Illinois, USA.
34. Kolesarova, N., Hutnan, M., Bodik, I., & Spalkova, V. (2011). Utilization of
Biodiesel By-Products for Biogas Production. Journal of Biomedicine and
Biotechnology, doi:10.1155/2011/126798.
40
35. Celik, E., Ozbay, N., Oktar, N., & Calık, P. (2008). Use of Biodiesel Byproduct
Crude Glycerol as the Carbon Source for Fermentation Processes by
Recombinant Pichia pastoris. Ind. Eng. Chem. Res. 47, 2985-2990.
36. Indexmundi (2011). World Biodiesel Production and Consumption by Year.
Retrieved August 24, 2012: www.indexmundi.com/energy.aspx?product=
biodiesel&graph=production+consumption.
37. Harwood, H.J. (1984). Oleochemicals as a fuel: Mechanical and economic
feasibility. J. Am. Oil Chem. Soc. 61, 315-324.
38. Samart, C., Chaiya, C., & Reubroycharoen, P. (2010). Biodiesel production by
methanolysis of soybean oil using calcium supported on mesoporous silica
catalyst. Energy Conversion and Management 51(7), 1428-1431.
39. Ardebili, M.S., Ghobadian, B., Najafi, G., & Chegeni, A. (2011). Biodiesel
production potential from edible oil seeds in Iran. Renew. Sust. Energ. Rev.
15(6), 3041-3044.
40. Sarin, R., Sharma, M., Sinharay, S., & Malhotra, R.K. (2007). Jatropha–Palm
biodiesel blends: An optimum mix for Asia. Fuel 86(10-11), 1365-1371.
41. Jham, G.N., Moser, B.R., Shah, S.N., Holser, R.A., Dhingra, O.D., Vaughn,
S.F., Berhow, M.A., Winkler-Moser, J.K., Isbell, T.A., Holloway, R.K., Walter,
E.L., Natalino, R., Anderson, J.C., & Stelly, D.M. (2009). Wild Brazilian
Mustard (Brassica juncea L.) Seed Oil Methyl Esters as Biodiesel Fuel. J. Am.
Oil Chem. Soc. 86, 917-926.
42. Li, J., Fu, Y.J., Qu, X.J., Wang, W., Luo, M., Zhao, C.J., & Zu, Y.G. (2012).
Biodiesel production from yellow horn (Xanthoceras sorbifolia Bunge.) seed oil
41
using ion exchange resin as heterogeneous catalyst. Bioresource Technology
108, 112-118.
43. Sharma, Y.C., Singh, B., & Korstad, J. (2010). High Yield and Conversion of
Biodiesel from a Nonedible Feedstock (Pongamia pinnata). J. Agric. Food
Chem. 58, 242-247.
44. Puhan, S., Vedaraman, N., Ram, B.V.B., Sankarnarayanan, G., & Jeychandran,
K. (2005). Mahua oil (Madhuca Indica seed oil) methyl ester as biodiesel-
preparation and emission characteristics. Biomass and Bioenergy 28(1), 87-93.
45. Ramadhas, A.S., Jayaraj, S., & Muraleedharan, C. (2005). Biodiesel production
from high FFA Rubber seed oil. Fuel 84, 335-340.
46. Rashid, U., Anwar, F., Moser, B.R., & Knothe, G. (2008). Moringa oleifera oil:
A possible source of biodiesel. Bioresource Technology 99, 8175-8179.
47. Aransiola, E.F., Betiku, E., Ikhuomoregbe, D.I.O., & Ojumu, T.V. (2012).
Production of biodiesel from crude neem oil feedstock and its emissions from
internal combustion engines. African Journal of Biotechnology 11(22), 6178-
6186.
48. Stephenson, A.L., Kazamia, E., Dennis, J.S., Howe, C.J., Scott, S.A., & Smith,
A.G. (2010). Life-Cycle Assessment of Potential Algal Biodiesel Production in
the United Kingdom: A Comparison of Raceways and Air-Lift Tubular
Bioreactors. Energy & Fuels 24, 4062-4077.
49. El-Mashada, H.M., Zhanga, R., & Avena-Bustillos, R.J. (2008). A two-step
process for biodiesel production from salmon oil. Biosystems Engineering 99,
220-227.
42
50. Goffman, F.D., & Gómez, N.V. (1996). Potential for the use of new oil
producing crops as source material for the synthesis of biodiesel. Proceedings of
the Ninth international conference on jojoba and its uses and of the Third
international conference on new industrial crops and products, pp. 225-228.
51. Korbitz, W. (1999). Biodiesel production in Europe and North America, an
encouraging prospect. Renewable Energy 16, 1078-1083.
52. Azam, M.M., Waris, A., & Nahar, N.M. (2005). Prospects and potential of fatty
acid methyl esters of some non traditional seed oils for use as biodiesel in India.
Biomass and Bioenergy 29, 293-302.
53. Banerji, R., Chowdhury, A.R., Misra, F., Sudarsanam, G., Verma, S.C., &
Srivatsava, G.S. (1985). Jatropha seed oils for energy. Biomass 8, 277-282.
54. Kumar, A., & Sharma, S. (2011). Potential non-edible oil resources as biodiesel
feedstock: An Indian perspective. Renew. Sust. Energ. Rev. 15(4), 1791-1800.
55. Murugesan, A., Umarani, C., Chinnusamy, T.R., Krishnan, M., Subramanian,
R., & Neduzchezhain, N. (2008). Production and analysis of bio-diesel from
non-edible oils - A review. Renew. Sust. Energ. Rev. 13(4), 825-834.
56. Sahoo, P.K., Das, L.M., Babu, M.K.G., & Naik, S.N. (2007). Biodiesel
development from high acid value polanga seed oil and performance evaluation
in a CI engine. Fuel 86, 448-454.
57. Veljkovic, V.B., Lakicevic, S.H., Stamenkovic, O.S., Todorovic, Z.B., & Lazic,
M.L. (2006). Biodiesel production from tobacco (Nicotiana tabacum L.) seed oil
with a high content of free fatty acids. Fuel 85, 2671-2675.
58. Nadarajapillai, N., & Wijewantha, R.T. (1967). Productivity Potentials of
Rubber Seed. Bull. Rubber Res. Inst. Ceylon 2, 8-17.
43
59. National Rubber Board, India (2012). Rubber Cultivation. Retrieved August 24,
2012: http://rubberboard.org.in/ManageCultivation.asp?Id=236.
60. Bender, M. (1999). Economic Feasibility Review for Community-Scale Farmer
Cooperatives for Biodiesel. Bioresource Technology 70, 81-87.
61. Noordam, M., & Withers, R.V. (1996). Producing Biodiesel from Canola in the
Inland Northwest: An Economic Feasibility Study. Idaho Agricultural
Experiment Station, Bulletin No. 785, University of Idaho College of
Agriculture, Moscow, Idaho.
62. Reining, R.C., & Tyner, W.E. (1983). Comparing Liquid Fuel Costs: Grain
Alcohol Versus Sunflower Oil. Am. J. Agric. Econ. 65, 567-570.
63. Anon (1982). Filtered used frying fat powers diesel fleet. J Am. Oil Chem. Soc.
59, 780A-781A.
64. Peterson, C.L., Wagner, G.L., & Auld, D.L. (1983). Vegetable oil substitutes for
diesel fuel. Trans. ASAE 26(2), 322-327.
65. Ziejewski, M., Goettler, H., & Pratt, G.L. (1986). Paper No. 860301,
International Congress and Exposition, Detroit, Michigan.
66. Schwab, A.W., Bagby, M.O., & Freedman, B. (1987). Preparation and
properties of diesel fuels from vegetable oils. Fuel 66, 1372-1378.
67. Ziejewski, M., Kaufman, K.R., Schwab, A.W., & Pryde, E.H. (1984). Diesel
engine evaluation of a non-ionic sunflower oil-aqueous ethanol microemulsion.
J. Am. Oil Chem. Soc. 61, 1620-1626.
44
68. Goering, C.E. (1984b). Final report for project on effect of nonpetroleum fuels
on durability of direct-injection diesel engines under contract 59-2171-1-6-057-
0, USDA, ARS, Peoria, Illinois.
69. Ziejewski, M.Z., Kaufman, K.R., & Pratt, G.L. (1983). Vegetable oil as diesel
fuel, USDA, Argic, Rev. Man., ARM-NC-28, pp. 106-111.
70. Pryde, E.H. (1984). Vegetable oils as fuel alternatives – symposium overview.
J. Am. Oil Chem. Soc. 61, 1609-1610.
71. Goering, C.E., & Fry, B. (1984a). Engine durability screening test of a diesel
oil/soy oil/alcohol micro-emulsion fuel. J. Am. Oil Chem. Soc. 61, 1627-1632.
72. Weisz, P.B., Haag, W.O., & Rodeweld, P.G. (1979). Catalytic production of
high-grade fuel (gasoline) from biomass compounds by shapedelective catalysis.
Science 206, 57-58.
73. Niehaus, R.A., Goering, C.E., Savage, L.D., & Sorenson, S.C. (1986). Cracked
soybean oil as a fuel for a diesel engine. Trans. ASAE 29, 683-689.
74. Schwab, A.W., Dykstra, G.J., Selke, E., Sorenson, S.C., & Pryde, E.H. (1988).
Diesel fuel from thermal decomposition of soybean oil. J. Am. Oil Chem. Soc.
65, 1781-1786.
75. Billaud, F., Dominguez, V., Broutin, P., & Busson, C. (1995). Production of
hydrocarbons by pyrolysis of methyl esters from rapeseed oil. J. Am. Oil Chem.
Soc. 72, 1149-1154.
76. Alencar, J.W., Alves, P.B., & Craveiro, A.A. (1983). Pyrolysis of tropical
vegetable oils. J. Agric. Food Chem. 31, 1268-1270.
45
77. Fukuda, H., Kondo, A., & Noda, H. (2001). Biodiesel production by
transesterification of oils. Journal of Bioscience and Bioengineering 92(5), 405-
416.
78. Clark, S.J., Wangner, L., Schrock, M.D., & Piennaar, P.G. (1984). Methyl and
ethyl soybean esters as renewable fuels for diesel engines. J. Am. Oil Chem.
Soc. 61, 1632-1638.
79. Demirbas, A. (2009). Production of biodiesel fuels from linseed oil using
methanol and ethanol in non-catalytic SCF conditions. Biomass and Bioenergy
33(1), 113-118.
80. Formo, M.W. (1954). Ester reactions of fatty materials. J. Am. Oil Chem. Soc.
31(11), 548-559.
81. Wright, H.J., Segur, J.B., Clark, H.V., Coburn, S.K., Langdon, E.E., & DePuis,
R.N. (1944). A report on ester interchange. Oil and soap 21, 145-148.
82. Eckey, E.W. (1956). Esterification and Inter-esterification. J. Am. Oil Chem.
Soc. 33(11), 575-579.
83. Crabbe, E., Nolasco-Hipolito, C., Kobayashi, G., Sonomoto, K., & Ishizaki, A.
(2001). Biodiesel production from crude palm oil and evaluation of butanol
extraction and fuel properties. Process Biochemistry 37(1), 65-71.
84. Van Gerpen, J. (2005). Biodiesel processing and production. Fuel Process.
Technol. 86, 1097-1107.
85. Canakci, M., & Van Gerpen, J. (1999). Biodiesel production via acid catalysis.
Trans. ASAE 42, 1203-1210.
86. Van Gerpen, J., Shanks, B., Pruszko, R., Clements, D., & Knothe, G. (2004).
Biodiesel Production Technology. NREL/SR-510-36244.
46
87. Canakci, M., & Van Gerpen, J. (2001). Biodiesel production from oils and fats
with high free fatty acids. Trans. ASAE 44(6), 1429-1436.
88. Zufarov, O., Schmidt, S., & Sekretár, S. (2008). Degumming of rapeseed and
sunflower oils. Acta Chimica Slovaca 1(1), 321-328.
89. Jensen, R.G., Sampugna, J., & Gander, G.W. (1961). Glyceride and Fatty Acid
Composition of Some Mono-Diglyceride Ice Cream Emulsifiers. Journal of
Dairy Science 44(6), 1057-1060.
90. Ma, F. (1998). Biodiesel fuel: the transesterification of beef tallow. Ph.D
dissertation. Biological Systems Engineering, University of Nebraska-Lincoln,
USA.
91. Gogate, P.R., Tayal, R.K., & Pandit, A.B. (2006). Cavitation: A technology on
the horizon. Current Science 91(1), 35-46.
92. Stavarache, C., Vinatoru, M., Nishimura, R., & Maeda, Y. (2005). Fatty acids
methyl esters from vegetable oil by means of ultrasonic energy. Ultrasonics
Sonochemistry 12, 367-372.
93. Kachhwaha, S.S., Maji, S., Faran, M., Gupta, A., Ramchandran, J., & Kumar,
D. (2006). Preparation of biodiesel from jatropha oil using ultrasonic energy.
Proceedings of the National Conference on Trends and Advances in Mechanical
Engineering, YMCA Institute of Engineering, Faridabad, Haryana.
94. Ibiari, N.N., Abo El-Enin, S.A., Attia, N.K., & El-Diwani, G. (2010). Ultrasonic
Comparative Assessment for Biodiesel Production from Rapeseed. Journal of
American Science 6(12), 937-943.
95. Kumar, D., Kumar, G., Johari, R., & Kumar, P. (2012). Fast, easy
ethanomethanolysis of Jatropha curcus oil for biodiesel production due to the
47
better solubility of oil with ethanol in reaction mixture assisted by
ultrasonication. Ultrasonics Sonochemistry 19(4), 816-822.
96. Gong, C., & Hart, D.P. (1998). Ultrasound Induced Cavitation and
Sonochemical Yields. Journal of the Acoustical Society of America 104(5),
2675-2682.
97. Santos, H.M., Lodeiro, C., & Capelo-MartRnez, J. (2009). Ultrasound in
Chemistry. In J. Capelo-Martínez (Eds.), The Power of Ultrasound. Wiley
publications, Germany, pp. 1-16.
98. Suslick, K.S. (February 1989). The Chemical Effects of Ultrasound. Scientific
American, 80-86.
99. Xuea, J., Grifta, T.E., & Hansen, A.C. (2011). Effect of biodiesel on engine
performances and emissions. Renew. Sust. Energ. Rev. 15, 1098-1116.
100. Sivaramakrishnan, K., & Ravikumar, P. (2011). Determination of higher heating
value of biodiesels. International Journal of Engineering Science and
Technology 3(11), 7981-7987.
101. Van Gerpen, J., Hammond, E.G., Johnson, L.A., Marley, S.J., Yu, L., Lee, I.,
& Monyem, A. (1996). Determining the Influence of Contaminants on Biodiesel
Properties. Final report prepared for: The Iowa Soybean Promotion Board, Iowa
State University, USA.
102. Knothe, G. (2005). Dependence of biodiesel fuel properties on the structure of
fatty acid alkyl esters. Fuel Process. Technol. 86, 1059-1070.
103. McCormick, R.L., & Westbrook, S.R. (2010). Storage Stability of Biodiesel and
Biodiesel Blends. Energy & Fuels 24, 690-698.
48
104. Mittelbach, M., & Gangl, S. (2001). Long Storage Stability of Biodiesel Made
from Rapeseed and Used Frying Oil. J. Am. Oil Chem. Soc. 78, 573-577.
105. Dunn, R.O. (2005). Effect of antioxidants on the oxidative stability of methyl
soyate (biodiesel). Fuel Process. Technol. 86, 1071-1085.
106. Moser, B.R. (2011). Influence of extended storage on fuel properties of methyl
esters prepared from canola, palm, soybean and sunflower oils. Renewable
Energy 36, 1221-1226.
107. Bita, M.G., Grecu, D.R., Tutunea, D., Popescu, A., & Bica, M. (2009). Role of
the Extract Obtained from Seeds of Vitis Vinifera on the Oxidative Stability of
Biodiesel. Rev. Chim. (Bucharest) 60(10), 1090-1093.
108. Waynick, J.A. (2005). Characterization of biodiesel oxidation and oxidation
products. CRC Project No. AVFL-2b NREL/TP-540-39096.
109. Junior, J.S., Mariano, A.P., & Angelis, D.F. (2009). Biodegradation of
biodiesel/diesel blends by Candida Viswanathii. African Journal of
Biotechnology 8(12), 2774-2778.
110. Tang, H., Wang, A., Salley, S.O., & Simon Ng, K.Y. (2008). The Effect of
Natural and Synthetic Antioxidants on the Oxidative Stability of Biodiesel. J.
Am. Oil Chem. Soc. 85, 373-382.
111. Navy Environmental Health Center (2001). Fuels Comparison Chart. Retrieved
August 24, 2012: www.nmcphc.med.navy.mil/downloads/
ep/fuels_comp_chart.pdf.
112. Guzman, R.D., Tang, H., Salley, S.O., & Simon Ng, K.Y. (2009). Synergistic
Effects of Antioxidants on the Oxidative Stability of Soybean Oil- and Poultry
Fat-Based Biodiesel. J. Am. Oil Chem. Soc. 86, 459-467.
49
113. Domingos, A.K., Saad, E.B., Vechiatto, W.W.D., Wilhelm, H.M., & Ramos,
L.P. (2007). The influence of BHA, BHT and TBHQ on the oxidation stability
of soybean oil ethyl esters (biodiesel). J. Braz. Chem. Soc. 18(2), 416-423.
114. Brewer, M.S. (2011). Natural Antioxidants: Sources, Compounds, Mechanisms
of Action, and Potential Applications. Comprehensive Reviews in Food Science
and Food Safety 10, 221-247.
115. Diwani, G.E., Rafie, S.E., & Hawas, S. (2009). Protection of biodiesel and oil
from degradation by natural antioxidants of Egyptian Jatropha. Int. J. Environ.
Sci. Tech. 6(3), 369-378.
116. Aluyor, E.O., & Ori-Jesu, M. (2008). The use of antioxidants in vegetable oils -
A review. African Journal of Biotechnology 7(25), 4836-4842.
117. Gupta, V.K., & Sharma, S.K. (2006). Plants as Natural antioxidants. Natural
product Radiance 5(4), 326-334.
118. Koontz, J.L. (2008). Controlled release of natural antioxidants from polymer
food packaging by molecular encapsulation with cyclodextrins. Ph.D. Thesis,
Food Science and Technology, Virginia Polytechnic Institute and State
University, USA.
119. Nahm, H.S., Juliani, H.R., Nahm, J.E.S., Seung, H., Juliani, H.R., & Simon, J.E.
(2012). Effects of Selected Synthetic and Natural Antioxidants on the Oxidative
Stability of Shea Butter (Vitellaria paradoxa subsp. paradoxa). Journal of
Medicinally Active Plants 1(2), 69-75.
120. Skupien, K., Ochmian, I., Grajkowski, J., & Krzywy-Gawronska, E. (2011).
Nutrients, antioxidants and antioxidant activity of organically and
50
conventionally grown raspberries. Journal of Applied Botany and Food Quality
84(1), 85-89.
121. Kalam, S., Singh, R., Mani, A., Patel, J., Khan, F.N., & Pandey, A. (2012).
Antioxidants: elixir of life. International Multidisciplinary Research Journal
2(1), 18-34.
122. Halvorsen, B.L., Holte, K., Myhrstad, M.C.W., Barikmo, I., Hvattum, E.,
Remberg, S.F., Wold, A., Haffner, K., Baugerod, H., Andersen, L.F., Moskaug,
J.O., Jacobs, D.R., & Blomhoff, R. (2002). A Systematic Screening of Total
Antioxidants in Dietary Plants. Journal of Nutrition 132, 461-471.
123. Svilaas, A., Sakhi, A.K., Andersen, L.F., Svilaas, T., Ström, E.C., Jacobs, D.R.,
Ose, L., & Blomhoff, R. (2004). Intakes of Antioxidants in Coffee, Wine, and
Vegetables Are Correlated with Plasma Carotenoids in Human. Journal of
Nutrition 134, 562-567.
124. Lipinski, B. (2012). Is it oxidative or free radical stress and why does it matter.
Oxid. Antioxid. Med. Sci. 1(1), 5-9.
125. Maduka, H.C.C., Uhwache, H.M., & Okoye, Z.S.C. (2003). Comparative Study
of the Antioxidant Effect of Sacoglottis gabonensis Stem Bark Extract, a
Nigerian Alcoholic Beverage Additive and Vitamins C and E on the
Peroxidative Deterioration of Some Common Stored Vegetable Oils in
Maiduguri. Pak. J. Biol. Sci. 6(3), 202-207.
126. Ibrahium, M.I. (2010). Efficiency of Pomegranate Peel Extract as Antimicrobial,
Antioxidant and Protective Agents. World Journal of Agricultural Sciences 6(4),
338-344.
51
127. United States Environmental Protection Agency (2002). A Comprehensive
Analysis of Biodiesel Impacts on Exhaust Emissions, EPA420-P-02-001.
128. Kousoulidou, M., Fontaras, G., Mellios, G., & Ntziachristos, L. (2008). Effect
of biodiesel and bioethanol on exhaust emissions. ETC/ACC Technical Paper
2008/5, Report No.: 08.RE.0006.V1.
129. Xuea, J., Grift, T.E., & Hansena, A.C. (2011). Effect of biodiesel on engine
performances and emissions. Renew. Sust. Energ. Rev. 15, 1098-1116.