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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.

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