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Fuel is any material that stores energy that can later be extracted to perform mechanical work in a
controlled manner. Most fuels used to convert current into energy include various other exothermic
chemical reactions and nuclear reactions, such as nuclear fission or nuclear fusion. Fuels are also
used in the cells of organisms in a process known as cellular respiration, where organic molecules are
oxidized to release un-usable energy.Hydrocarbons are by far the most common source of fuel used
by humans, but other substances, including radioactive metals, are not utilized.
Contents
[hide]
1 Chemical
o 1.1 Biofuels
o 1.2 Fossil fuels
2 Nuclear
o 2.1 Fission
o 2.2 Fusion
3 World trade
4 Use over time
5 Classification of fuel
6 See also
7 Footnotes
8 References
9 Further reading
[edit]Chemical
Chemical fuels are substances that release energy by reacting with substances around them, most
notably by the process of oxidation.
[edit]Biofuels
Main article: Biofuel
Biofuel can be broadly defined as solid, liquid, or gas fuel consisting of, or derived from biomass.
Biomass can also be used directly for heating or power—known as biomass fuel. Biofuel can be
produced from any carbon source that can be replenished rapidly e.g. plants. Many different plants
and plant-derived materials are used for biofuel manufacture.
Perhaps the earliest fuel employed by humans is wood. Evidence shows controlled fire was used up
to 1.5 million years ago at Swartkrans, South Africa. It is unknown which hominid species first used
fire, as both Australopithecus and an early species of Homo were present at the sites.[1] As a fuel,
wood has remained in use up until the present day, although it has been superseded for many
purposes by other sources. Wood has an energy density of 10–20 MJ/kg.[2]
Recently biofuels have been developed for use in automotive transport (for
example Bioethanol and Biodiesel), but there is widespread public debate about how carbon efficient
these fuels are.
[edit]Fossil fuels
Main article: Fossil fuel
Fossil fuels are hydrocarbons, primarily coal and petroleum (liquid petroleum or natural gas), formed
from the fossilized remains of ancient plants and animals[3] by exposure to high heat and pressure in
the absence of oxygen in the Earth's crust over hundreds of millions of years.[4] Commonly, the term
fossil fuel also includes hydrocarbon-containing natural resources that are not derived entirely from
biological sources, such as tar sands. These latter sources are properly known as mineral fuels.
[edit]Nuclear
Main article: Nuclear fuel
Nuclear fuel is any material that is consumed to derive nuclear energy. Technically speaking this
definition includes all matter because any element will under the right conditions release nuclear
energy, the only materials that are commonly referred to as nuclear fuels though are those that will
produce energy without being placed under extreme duress.
[edit]Fission
Nuclear fuel pellets are used to create nuclear energy.
The most common type of nuclear fuel used by humans is heavy fissile elements that can be made to
undergo nuclear fission chain reactions in anuclear fission reactor; nuclear fuel can refer to the
material or to physical objects (for example fuel bundles composed of fuel rods) composed of the fuel
material, perhaps mixed with structural, neutron moderating, or neutron reflecting materials. The most
common fissile nuclear fuels are 235 U and239 Pu , and the actions of mining, refining, purifying, using,
and ultimately disposing of these elements together make up the nuclear fuel cycle, which is important
for its relevance to nuclear power generation and nuclear weapons. In addition there are various
types of fuels.
[edit]Fusion
Fuels that produce energy by the process of nuclear fusion are currently not utilized by man but are
the main source of fuel for stars, the most powerful energy sources in nature. Fusion fuels tend to be
light elements such as hydrogen which will combine easily. Energy is required to start fusion by
raising temperature so high all materials would turn into plasma, and allow nuclear to collide and stick
together with each other before repelling due to electric charge. This process is called fusion and it
can give out energy.
In stars that undergo nuclear fusion, fuel consists of atomic nuclei that can release energy by the
absorption of a proton or neutron. In most stars the fuel is provided by hydrogen, which can combine
together to form helium through the proton-proton chain reaction or by the CNO cycle. When the
hydrogen fuel is exhausted, nuclear fusion can continue with progressively heavier elements,
although the net energy released is lower because of the smaller difference in nuclear binding energy.
Once iron-56 or nickel-56 nuclei are produced, no further energy can be obtained by nuclear fusion as
these have the highest nuclear binding energies. The elements then on use up energy instead of
giving out when fused, and therefore fusion stops and the stars die. In attempts by human, fusion are
only carried out with hydrogen (isotope of 2 and 3) to form helium-4 as this reaction gives out the most
net energy. Electric confinement (ITER), inertial confinement(heating by laser) and heating by strong
electric currents are the popular methods used. The power given out is enormonus as each kilogram
of hydrogen can give out 0.41PJ. This means that burning 0.7 tonne of hydrogen per second can
power the world, replacing the millions of tonnes of fossil fuels burnt and emission made by us each
second. Unfortunately this clean energy whose product would dissipate harmlessly as helium if leak
happens, and also does not emit any radiation or pollution, is not expected to contribute electricity to
electricity networks until 2040.[5]
[edit]World trade
Fuel imports in 2005
World Bank reported that the USA was the top fuel importer in 2005 followed by the EU and Japan.[citation needed]
[edit]Use over time
The first use of fuel was the combustion of wood or sticks by Homo erectus near 2 million years ago.[6]
[page needed] Throughout the majority of human history fuels derived from plants or animal fat were the
only ones available for human use. Charcoal, a wood derivative, has been used since at least 6,000
BCE for melting metals. It was only supplanted by coke, derived from coal, as the forests started to
become depleted around the 18th century. Charcoal briquettes are now commonly used as a fuel
for barbecue cooking.[7]
Coal was first used as a fuel around 1000 BCE in China. With the development of the steam engine in
1769, coal came into more common use as a power source. Coal was later used to drive ships and
locomotives. By the 19 th century, gas extracted from coal was being used for street lighting
in London. In the 20th century, the primary use of coal is for the generation of electricity, providing
40% of the world's electrical power supply in 2005.[8]
Fossil fuels were rapidly adopted during the industrial revolution, because they were more flexible
than traditional energy sources, such as water power.
Currently the trend has been towards renewable fuels, such as biofuels like alcohols.
[edit]Classification of fuel
On the basis of occurrence, fuels can be classified as of two types, primary (natural
fuel) and secondary (artificial fuel).
Primary fuels are of three types, solid (wood, coal, peat, lignite, cow dung, etc. ), liquid (crude oil)
and gaseous (natural gas).
Secondary fuels are also of three types, solid (coke, charcoal, petroleum), liquid (diesel, petrol, tar,
kerosene, LPG) and gaseous (water gas, blast furnace gas, coal gas, coke oven gas, CNG).
Charcoal
Peat digging by hand inSaterland, 1963
LPG
Liquefied petroleum gas, also called LPG, GPL, LP Gas, liquid petroleum gas or
simply propane or butane, is a flammable mixture ofhydrocarbon gases used as a fuel in heating
appliances and vehicles. It is increasingly used as an aerosol propellant and a refrigerant,
replacingchlorofluorocarbons in an effort to reduce damage to the ozone layer. When specifically used
as a vehicle fuel it is often referred to as autogas.
Varieties of LPG bought and sold include mixes that are primarily propane (C3H8),
primarily butane (C4H10) and, most commonly, mixes including both propane and butane, depending
on the season — in winter more propane, in summer more butane[citation needed]. In the United States,
primarily only two grades of LPG are sold, commercial propane and HD-5. These specifications are
published by the Gas Processors Association (GPA)[1] and the American Society of Testing and
Materials (ASTM).[2] Propane/butane blends are also listed in these
specifications. Propylene, butylenes and various other hydrocarbons are usually also present in small
concentrations. HD-5 limits the amount of propylene that can be placed in LPG, and is utilized as an
autogas specification. A powerful odorant, ethanethiol, is added so that leaks can be detected easily.
The international standard is EN 589. In the United States, tetrahydrothiophene (thiophane) or amyl
mercaptan are also approved odorants,[3] although neither is currently being utilized. Major suppliers
of LPG in the UK include AvantiGas, Calor gas and Flogas.
LPG is prepared by refining petroleum or "wet" natural gas, and is almost entirely derived from fossil
fuel sources, being manufactured during the refining of petroleum (crude oil), or extracted from
petroleum or natural gas streams as they emerge from the ground. It was first produced in 1910
by Dr. Walter Snelling, and the first commercial products appeared in 1912. It currently provides about
3% of all energy consumed, and burns relatively cleanly with nosoot and very few sulfur emissions.
As it is a gas, it does not pose ground or water pollution hazards, but it can cause air pollution. LPG
has a typical specific calorific value of 46.1 MJ/kg compared with 42.5 MJ/kg for fuel oil and
43.5 MJ/kg for premium grade petrol (gasoline).[4] However, its energy density per volume unit of 26
MJ/L is lower than either that of petrol or fuel oil, as its liquid density is lower (about 0.5—0.58,
compared to 0.71—0.77 forgasoline).
As its boiling point is below room temperature, LPG will evaporate quickly at
normal temperatures and pressures and is usually supplied in pressurised steel vessels. They are
typically filled to between 80% and 85% of their capacity to allow for thermal expansion of the
contained liquid. The ratio between the volumes of the vaporized gas and the liquefied gas varies
depending on composition, pressure, and temperature, but is typically around 250:1. The pressure at
which LPG becomes liquid, called its vapour pressure, likewise varies depending on composition and
temperature; for example, it is approximately 220 kilopascals (32 psi) for pure butane at 20 °C (68 °F),
and approximately 2.2 megapascals (320 psi) for pure propane at 55 °C (131 °F). LPG is heavier
than air, unlike natural gas, and thus will flow along floors and tend to settle in low spots, such
as basements. There are two main dangers from this. The first is a possible explosion if the mixture of
LPG and air is right and if there is an ignition source. The second is suffocation due to LPG displacing
air, causing a decrease in oxygen concentration. In addition, an odorant is mixed with LPG used for
fuel purposes so that leaks can be detected more easily.
Large amounts of LPG can be stored in bulk cylinders and can be buried underground.
Contents
[hide]
1 Uses
o 1.1 Rural heating
o 1.2 Motor fuel
o 1.3 Refrigeration
o 1.4 Cooking
2 Security of supply
3 Comparison with natural gas
4 Environmental effects
5 Fire risk and mitigation
6 See also
7 References
8 External links
[edit]Uses
[edit]Rural heating
Cylinders with LP gas in India
Predominantly in Europe and rural parts of many countries, LPG can provide an alternative to
electricity and heating oil (kerosene). LPG is most often used where there is no access to piped
natural gas.
LPG can be used as a power source for combined heat and power technologies (CHP). CHP is the
process of generating both electrical power and useful heat from a single fuel source. This technology
has allowed LPG to be used not just as fuel for heating and cooking, but also for de-centralised
generation of electricity.
LPG can be stored in a variety of ways. LPG, as with other fossil fuels, can be combined with
renewable power sources to provide greater reliability while still achieving some reduction in
CO2 emissions.
[edit]Motor fuel
LPG filling connector on a car
Main article: Autogas
White bordered green diamond symbol used on LPG-powered vehicles in China
When LPG is used to fuel internal combustion engines, it is often referred to as autogas or auto
propane. In some countries, it has been used since the 1940s as a petrol alternative for spark ignition
engines. In some countries, there are additives in the liquid that extend engine life and the ratio of
butane to propane is kept quite precise in fuel LPG. Two recent studies have examined LPG-fuel-oil
fuel mixes and found that smoke emissions and fuel consumption are reduced
but hydrocarbon emissions are increased.[5][6] The studies were split on CO emissions, with one
finding significant increases,[5] and the other finding slight increases at low engine load but a
considerable decrease at high engine load.[6] Its advantage is that it is non-toxic, non-corrosive and
free of tetraethyllead or any additives, and has a high octane rating (102-108 RON depending on local
specifications). It burns more cleanly than petrol or fuel-oil and is especially free of
the particulates from the latter.
LPG has a lower energy density than either petrol or fuel-oil, so the equivalent fuel consumption is
higher. Many governments impose less tax on LPG than on petrol or fuel-oil, which helps offset the
greater consumption of LPG than of petrol or fuel-oil. However, in many European countries this tax
break is often compensated by a much higher annual road tax on cars using LPG than on cars using
petrol or fuel-oil. Propane is the third most widely used motor fuel in the world. 2008 estimates are
that over 13 million vehicles are fueled by propane gas worldwide. Over 20 million tonnes (over 7
billion US gallons) are used annually as a vehicle fuel.
Not all automobile engines are suitable for use with LPG as a fuel. LPG provides less upper cylinder
lubrication than petrol or diesel, so LPG-fueled engines are more prone to valve wear if they are not
suitably modified. Many modern common rail diesel engines respond well to LPG use as a
supplementary fuel. This is where LPG is used as fuel as well as diesel. Systems are now available
that integrate with OEM engine management systems.
[edit]Refrigeration
LPG is instrumental in providing off-the-grid refrigeration, usually by means of a gas absorption
refrigerator.
Blended of pure, dry propane (refrigerant designator R-290 ) and isobutane (R-600a) the blend—"R-
290a"—has negligible ozone depletion potential and very low global warming potential and can serve
as a functional replacement for R-12, R-22, R-134a,and
other chlorofluorocarbon or hydrofluorocarbon refrigerants in conventional stationary refrigeration and
air conditioning systems.[7]
Such substitution is widely prohibited or discouraged in motor vehicle air conditioning systems, on the
grounds that using flammable hydrocarbons in systems originally designed to carry non-flammable
refrigerant presents a significant risk of fire or explosion.[8][9][10][11][12][13][14][15]
Vendors and advocates of hydrocarbon refrigerants argue against such bans on the grounds that
there have been very few such incidents relative to the number of vehicle air conditioning systems
filled with hydrocarbons.[16][17] One particular test was conducted by a professor at the University of
New South Wales that unintentionally tested the worst case scenario of a sudden and complete
refrigerant loss into the passenger compartment followed by subsequent ignition. He and several
others in the car sustained minor burns to their face, ears, and hands, and several observers received
lacerations from the burst glass of the front passenger window. No one was seriously injured.[18]
[edit]Cooking
According to the 2011 Census of India, 28.5% of Indian households or 33.6 million Indian households
used LPG as cooking fuel in 2011, which is supplied to their homes either in pressurised cylinders or
through pipes. [19] LPG is subsidised by the government in India. Increase in LPG prices has been a
politically sensitive matter in India as it potentially affects the urban middle classvoting pattern.
LPG was once a popular cooking fuel in Hong Kong; however, the continued expansion of town gas to
buildings has reduced LPG usage to less than 24% of residential units.
LPG is the most common cooking fuel in Brazilian urban areas, being used in virtually all households.
Poor families receive a government grant ("Vale Gás") used exclusively for the acquisition of LPG.
[edit]Security of supply
Because of the natural gas and the oil-refining industry, Europe is almost self-sufficient in LPG.
Europe's security of supply is further safeguarded by:
a wide range of sources, both inside and outside Europe;
a flexible supply chain via water, rail and road with numerous routes and entry points into Europe;
As of early 2008, world reserves of natural gas — from which most LPG is derived — stood at
6,342.411 trillion cubic feet. Added to the LPG derived from cracking crude oil, this amounts to a
major energy source that is virtually untapped and has massive potential. Production continues to
grow at an average annual rate of 2.2%, virtually assuring that there is no risk of demand outstripping
supply for the foreseeable future.[citation needed]
[edit]Comparison with natural gas
LPG is composed primarily of propane and butane, while natural gas is composed of the lighter
methane and ethane. LPG, vaporised and at atmospheric pressure, has a higher calorific
value(94 MJ/m3 equivalent to 26.1kWh/m3) than natural gas (methane) (38 MJ/m3 equivalent to
10.6 kWh/m3), which means that LPG cannot simply be substituted for natural gas. In order to allow
the use of the same burner controls and to provide for similar combustion characteristics, LPG can be
mixed with air to produce a synthetic natural gas (SNG) that can be easily substituted. LPG/air mixing
ratios average 60/40, though this is widely variable based on the gases making up the LPG. The
method for determining the mixing ratios is by calculating the Wobbe index of the mix. Gases having
the same Wobbe index are held to be interchangeable.
LPG-based SNG is used in emergency backup systems for many public, industrial and military
installations, and many utilities use LPG peak shaving plants in times of high demand to make up
shortages in natural gas supplied to their distributions systems. LPG-SNG installations are also used
during initial gas system introductions, when the distribution infrastructure is in place before gas
supplies can be connected. Developing markets in India and China (among others) use LPG-SNG
systems to build up customer bases prior to expanding existing natural gas systems.
[edit]Environmental effects
Commercially available LPG is currently derived from fossil fuels. Burning LPG releases CO2, an
important greenhouse gas, contributing to global warming. LPG does, however, release less CO2per
unit of energy than does coal or oil. It emits 81% of the CO2 per kWh produced by oil, 70% of that of
coal, and less than 50% of that emitted by coal-generated electricity distributed via the grid.[citation
needed] Being a mix of propane and butane, LPG emits less carbon per joule than butane but more
carbon per joule than propane.
LPG can be considered to burn more cleanly than heavier molecule hydrocarbons, in that it releases
very few particulates.
[edit]Fire risk and mitigation
This section needs additional citations for verification. Please
help improve this article by adding citations to reliable sources.
Unsourced material may be challenged and removed. (September 2009)
A spherical gas container typically found in refineries
In a refinery or gas plant, LPG must be stored in pressure vessels. These containers are either
cylindrical and horizontal or spherical. Typically, these vessels are designed and manufactured
according to some code. In the United States, this code is governed by the American Society of
Mechanical Engineers (ASME).
LPG containers have pressure relief valves, such that when subjected to exterior heating sources,
they will vent LPGs to the atmosphere. If a tank is subjected to a fire of sufficient duration and
intensity, it can undergo a boiling liquid expanding vapour explosion (BLEVE). This is typically a
concern for large refineries and petrochemical plants that maintain very large containers. In general,
tanks are designed that the product will vent faster than pressure can build to dangerous levels.
One remedy, that is utilized in industrial settings, is to equip such containers with a measure to
provide a fire-resistance rating. Large, spherical LPG containers may have up to a 15 cm steel wall
thickness. They are equipped with an approved pressure relief valve. A large fire in the vicinity of the
vessel will increase its temperature and pressure, following the basic gas laws. The relief valve on the
top is designed to vent off excess pressure in order to prevent the rupture of the container itself. Given
a fire of sufficient duration and intensity, the pressure being generated by the boiling and expanding
gas can exceed the ability of the valve to vent the excess. If that occurs, an overexposed container
may rupture violently, launching pieces at high velocity, while the released products can ignite as well,
potentially causing catastrophic damage to anything nearby, including other containers.
[edit]See also
Energy portal
Listing and approval use and compliance
Blau gas
Compressed natural gas (CNG)
Endothermic
Filling Carousel
Fireproofing
Fire-resistance rating
Gasoline gallon equivalent
Hybrid vehicles and Hybrid electric vehicles
Intumescent
Industrial gas
Liquefied natural gas (LNG)
Natural gas
Passive fire protection
Product certification
Underwriters Laboratories
World LP Gas Association
List of CO2 emitted per million Btu of energy from various fuels
[edit]References
1. ̂ "Liquefied Petroleum Gas Specifications and Test Methods". Gas
CNG
"CNG" redirects here. For other uses, see CNG (disambiguation).
Blue diamond symbol used on CNG-powered vehicles in North America
Green bordered white diamond symbol used on CNG-powered vehicles in China
A CNG powered high-floor Neoplan AN440A, operated by ABQ RIDE inAlbuquerque, New Mexico.
Compressed natural gas (CNG) is a fossil fuel substitute for gasoline (petrol), Diesel fuel,
or propane/LPG. Although its combustion does producegreenhouse 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 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, CH4), 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 (2,900–3,600 psi), usually in cylindrical or spherical shapes.
CNG is used in traditional gasoline internal combustion engine cars that have been converted into bi-
fuel vehicles (gasoline/CNG). Natural gas vehiclesare increasingly used in Iran, the Asia-
Pacific region (especially Pakistan [1] and the Indian capital of Delhi, and other large cities
like Ahmedabad,Mumbai, Kolkata, Chennai, etc. ), Latin America, Europe, and North America due to
rising gasoline prices.[2] In response to high fuel prices and environmental concerns, CNG is starting
to be used also in tuk-tuks and pickup trucks, transit and school buses, and trains.
The cost of this conversion is a barrier for CNG use as fuel and explains why public transportation
vehicles are early adopters, as they can amortize more quickly the money invested in the new (and
usually cheaper) fuel. In spite of these circumstances the number of vehicles in the world that use
CNG has grown steadily at a 30 percent annual rate.[3]
CNG's volumetric energy density is estimated to be 42% that of liquefied natural gas (because it is
not liquefied), and 25% that of Diesel fuel.[4]
Contents
[hide]
1 Uses
o 1.1 Cars
o 1.2 Locomotives
2 Advantages
3 Drawbacks
4 Codes and standards
5 CNG compared to LNG
6 CNG compared to HCNG
7 Worldwide
o 7.1 South America
o 7.2 South and East Asia
o 7.3 Middle East and Africa
o 7.4 Europe
o 7.5 North America
7.5.1 Canada
7.5.2 United States
o 7.6 Oceania
8 Deployments
9 DNG
10 References
[edit]Uses
[edit]Cars
CNG pumps at a Brazilian gasoline fueling station
Main article: Natural gas vehicle
Worldwide, there were 14.8 million natural gas vehicles by 2011, led by Iran with 2.86
million, Pakistan (2.85 million), Argentina (2.07 million), Brazil (1.7 million), and India (1.1 million).[5] with the Asia-Pacific region leading with 5.7 million NGVs, followed by Latin America with almost 4
million vehicles.[2]
Several manufacturers (Fiat, Opel (General Motors), Peugeot, Volkswagen, Toyota, Honda and
others) sell bi-fuel cars. In 2006, Fiat introduced the Siena Tetrafuel in the Brazilian market, equipped
with a 1.4L FIRE engine that runs on E100, E25 (Standard Brazilian Gasoline), Gasoline and CNG.
Any existing gasoline vehicle can be converted to a bi-fuel (gasoline/CNG) vehicle. Authorized shops
can do the retrofitting, this involves installing a CNG cylinder in the trunk, installing the plumbing,
installing a CNG injection system and the electronics.
[edit]Locomotives
CNG locomotives are operated by several railroads. The Napa Valley Wine Train successfully retrofit
a diesel locomotive to run on compressed natural gas before 2002.[6] This converted locomotive was
upgraded to utilize a computer controlled fuel injection system in May 2008, and is now the Napa
Valley Wine Train's primary locomotive.[7] Ferrocarril Central Andino in Peru, has run a CNG
Locomotive on a freight line since 2005[8] CNG locomotives are usually diesel locomotives that have
been converted to use compressed natural gas generators instead of diesel generators to generate
the electricity that drives the motors of the train. Some CNG locomotives are able to fire their cylinders
only when there is a demand for power, which, theoretically, gives them a higher fuel efficiency than
conventional diesel engines. CNG is also cheaper than petrol or diesel.
[edit]Advantages
CNG powered bus in Madrid, Spain being refueled.
Due to the absence of any lead or benzene content in CNG, the lead fouling of spark plugs is
eliminated.
CNG-powered vehicles have lower maintenance costs when compared with other hydrocarbon
fuel-powered vehicles.
CNG fuel systems are sealed, which prevents any spill or evaporation losses.
Increased life of lubricating oils, as CNG does not contaminate and dilute the crankcase oil.
Being a gaseous fuel, CNG mixes easily and evenly in air.
CNG is less likely to ignite on hot surfaces, since it has a high auto-ignition temperature (540 °C)
and a narrow range (5–15%) of flammability.[9]
Less pollution and more efficiency: CNG emits significantly less pollutants such as carbon
dioxide (CO2), unburned hydrocarbons (UHC), carbon monoxide (CO), nitrogen
oxides (NOx), sulfur oxides (SOx) and particulate matter (PM), compared to petrol. For example,
an engine running on petrol for 100 km emits 22,000 grams of CO2, while covering the same
distance on CNG emits only 16,275 grams of CO2.[10] CNG is essentially methane, i.e., CH4 with a
calorific value of 900 kJ/mol. This burns with oxygen to produce 1 mole of CO2 and 2 moles of
H2O. By comparison, petrol can be regarded as essentially benzene or similar, C6H6 with a
calorific value of about 3,300 kJ/mol and this burns to produce 6 moles of CO2 and 3 moles of
H2O. From this it can be seen that per mole of CO2 produced, CNG releases over 1.6 times as
much energy as that released from petrol (or for the same amount of energy, CNG produces
nearly 40% less CO2).
The corresponding figures are 78 and 25.8 grams respectively, for nitrogen oxides. Carbon
monoxide emissions are reduced even further. Due to lower carbon dioxide and nitrogen oxides
emissions, switching to CNG can help mitigate greenhouse gas emissions.[9] The ability of CNG
to reduce greenhouse gas emissions over the entire fuel lifecycle will depend on the source of the
natural gas and the fuel it is replacing. The lifecyclegreenhouse gas emissions for CNG
compressed from California's pipeline natural gas is given a value of 67.70 grams of CO2-
equivalent permegajoule (gCO2e/MJ) by the California Air Resources Board (CARB),
approximately 28% lower than the average gasoline fuel in that market (95.86 gCO2e/MJ). CNG
produced from landfill biogas was found by CARB to have the lowest greenhouse gas emissions
of any fuel analyzed, with a value of 11.26 gCO2e/MJ (over 88% lower than conventional
gasoline) in the low-carbon fuel standard that went into effect on January 12, 2010.[11]
[edit]Drawbacks
Gas storage in a car.
Compressed natural gas vehicles require a greater amount of space for fuel storage than
conventional gasoline powered vehicles. Since it is a compressed gas, rather than a liquid like
gasoline, CNG takes up more space for each gasoline gallon equivalent (GGE). Therefore, the tanks
used to store the CNG usually take up additional space in the trunk of a car or bed of a pickup truck
which runs on CNG. This problem is solved in factory-built CNG vehicles that install the tanks under
the body of the vehicle, leaving the trunk free (e.g., Fiat Multipla, New Fiat Panda, Volkswagen
Touran Ecofuel,Volkswagen Caddy Ecofuel, Chevy Taxi - which sold in countries such as Peru).
Another option is installation on roof (typical on buses), requiring, however, solution of structural
strength issues. CNG-powered vehicles are considered to be safer than gasoline-powered vehicles.[12]
[13][14]
[edit]Codes and standards
The lack of harmonized codes and standards across international jurisdictions is an additional barrier
to NGV market penetration.[15] The International Organization for Standards has an active technical
committee working on a standard for natural gas fuelling stations for vehicles.[16]
Despite the lack of harmonized international codes, natural gas vehicles have an excellent global
safety record. Existing international standards include ISO 14469-2:2007 which applies to CNG
vehicle nozzles and receptacle[17] and ISO 15500-9:2012 specifies tests and requirements for the
pressure regulator.[18]
NFPA-52 covers natural gas vehicle safety standards in the United States.
[edit]CNG compared to LNG
Compressed Natural Gas is often confused with liquefied natural gas (LNG). While both are stored
forms of natural gas, the key difference is that CNG is gas that is stored (as a gas) at high pressure,
while LNG is stored at very low temperature, becoming liquid in the process. CNG has a lower cost of
production and storage compared to LNG as it does not require an expensive cooling process and
cryogenic tanks. CNG requires a much larger volume to store the same mass of gasoline or petrol
and the use of very high pressures (3000 to 4000 psi, or 205 to 275 bar). As a consequence of this,
LNG is often used for transporting natural gas over large distances, in ships, trains or pipelines, and
the gas is then converted into CNG before distribution to the end user.
CNG can also be confused with LPG, which is liquified propane. Unlike natural gas (mostly methane),
propane can be compressed to a liquid without continual refrigeration. LPG is commonly used to fuel
vehicles in Australia.
CNG can be stored at lower pressure in a form known as an ANG (Adsorbed Natural Gas) tank, at 35
bar (500 psi, the pressure of gas in natural gas pipelines) in various sponge like materials, such
as activated carbon [19] and metal-organic frameworks (MOFs).[20] The fuel is stored at similar or greater
energy density than CNG. This means that vehicles can be refuelled from the natural gas network
without extra gas compression, the fuel tanks can be slimmed down and made of lighter, weaker
materials.
[edit]CNG compared to HCNG
The addition of hydrogen to CNG increases the H/C ratio of the fuel. HCNG has a flame speed about
eight times higher than CNG.[21]
[edit]Worldwide
Iran, Pakistan, Argentina, Brazil and India have the highest number of CNG run vehicles in the world.[5]
Top ten countries with most CNG vehicles-2011
(millions)
Pakistan 3.50[22]
Iran 2.86
Argentina 2.07
Brazil 1.7
India 1.1
Italy 0.78
People's Republic of China 0.61
Colombia 0.36
Uzbekistan 0.31
Thailand 0.30
World Total 14.8
Source:[5]
[edit]South America
CNG station in Rosario, Argentina.
CNG vehicles are commonly used in South America, where these vehicles are mainly used as
taxicabs in main cities of Argentina and Brazil.[23]Normally, standard gasoline vehicles are retrofitted in
specialized shops, which involve installing the gas cylinder in the trunk and the CNG injection system
and electronics. Argentina and Brazil are the two countries with the largest fleets of CNG vehicles,[23] with a combined total fleet of more than 3.4 million vehicles by 2009.[2] Conversion has been
facilitated by a substantial price differential with liquid fuels, locally produced conversion equipment
and a growing CNG-delivery infrastructure.
As of 2009 Argentina had 1,807,186 NGV's with 1,851 refueling stations across the nation,[2] or 15%
of all vehicles;[23] and Brazil had 1,632,101 vehicles and 1,704 refueling stations,[2] with a higher
concentration in the cities of Rio de Janeiro and São Paulo.[23][24]
Colombia had an NGV fleet of 300,000 vehicles, and 460 refueling stations as of 2009.[2] Bolivia has
increased its fleet from 10,000 in 2003 to 121,908 units in 2009, with 128 refueling stations.[2] Peru had 81,024 NGVs and 94 fueling stations as 2009,[2] but that number is expected to skyrocket
as Peru sits on South America's largest gas reserves.[23] In Peru several factory-built NGVs have the
tanks installed under the body of the vehicle, leaving the trunk free. Among the models built with this
feature are the Fiat Multipla, the newFiat Panda, the Volkswagen Touran Ecofuel, the Volkswagen
Caddy Ecofuel, and the Chevy Taxi. Other countries with significant NGV fleets
are Venezuela (15,000) and Chile (8,064) as of 2009.[2]
[edit]South and East Asia
A CNG powered Volvo B10BLE bus, operated by SBS Transit in Singapore.
In Singapore, CNG is increasingly being used by public transport vehicles like buses and taxis, as well
as goods vehicles. However, according to Channel NewsAsia on April 18, 2008, more owners of
private cars in this country are converting their petrol-driven vehicles to also run on CNG – motivated
no doubt by rising petrol prices. The initial cost of converting a regular vehicle to dual fuel at the
German conversion workshop of C. Melchers, for example, is around S$3,800 (US$2,500); with the
promise of real cost-savings that dual-fuel vehicles bring over the long term.
Singapore currently has five operating filling stations for natural gas. SembCorp Gas Pte Ltd runs the
station on Jurong Island, and jointly with Singapore Petroleum Company, the filling station at Jalan
Buroh. Both these stations are in the western part of the country. Another station on the mainland is in
Mandai Link to the north and is operated by SMART Energy. SMART also own a second station on
Serangoon North Ave 5 which was set up end of March 2009; The fifth and largest station in the world
was opened by the UNION Group in September 2009. This station is recognized by the Guniness
World Records as being the laregst in the world with 46 refuelling hoses. This station is located in Toh
Tuck. The Union Group, which operates 1000 CNG Toyota Wish taxis plan to introduce another three
daughter stations and increase the CNG taxi fleet to 8000 units.
CNG scooters (autorickshaws) in Dhaka,Bangladesh.
As a key incentive for using this eco-friendly fuel Singapore has a Green Vehicle Rebate (GVR) for
users of CNG technology. First introduced in January 2001, the GVR grants a 40% discount on the
Open Market Value (OMV) cost of newly registered green passenger vehicles. This initiative will end
at the end of 2012 as the government believes the 'critical mass' of CNG vehicles would then have
been built up.
The Ministry of Transport of Myanmar passed a law in 2005 which required that all public transport
vehicles - buses, trucks and taxis, be converted to run on CNG. The Government permitted several
private companies to handle the conversion of existing diesel and petrol cars, and also to begin
importing CNG variants of buses and taxis. Accidents and rumours of accidents, partly fueled by
Myanmar's position in local hydrocarbon politics,[25]has discouraged citizens from using CNG vehicles,
although now almost every taxi and public bus in Yangon, Myanmar's largest city, run on CNG. CNG
stations have been set up around Yangon and other cities, but electricity shortages mean that
vehicles may have to queue up for hours to fill their gas containers.[26] The Burmese opposition
movements are against the conversion to CNG, as they accuse the companies as being proxies of the
junta, and also that the petrodollars earned by the regime would go towards the defense sector, rather
than towards improving the infrastructure or welfare of the people.
In Malaysia, the use of CNG was originally introduced for taxicabs and airport limousines during the
late-1990s, when new taxis were launched with CNG engines while taxicab operators were
encouraged to send in existing taxis for full engine conversions. The practice of using CNG remained
largely confined to taxicabs predominantly in the Klang Valley and Penang due to a lack of interest.
No incentives were offered for those besides taxicab owners to use CNG engines, while government
subsidies on petrol and diesel made conventional road vehicles cheaper to use in the eyes of the
consumers. Petronas, Malaysia's state-owned oil company, also monopolises the provision of CNG to
road users. As of July 2008, Petronas only operates about 150 CNG refueling stations, most of which
are concentrated in the Klang Valley. At the same time, another 50 was expected by the end of 2008.[27]
As fuel subsidies were gradually removed in Malaysia starting June 5, 2008, the subsequent 41%
price hike on petrol and diesel led to a 500% increase in the number of new CNG tanks installed.[28]
[29] National car maker Proton considered fitting its Waja, Saga and Persona models with CNG kits
from Prins Autogassystemen by the end of 2008,[30] while a local distributor of locally
assembled Hyundai cars offers new models with CNG kits.[31] Conversion centres, which also
benefited from the rush for lower running costs, also perform partial conversions to existing road
vehicles, allowing them to run on both petrol or diesel and CNG with a cost varying between RM3,500
to RM5,000 for passenger cars.[28][32]
In China, companies such as Sino-Energy are active in expanding the footprint of CNG filling stations
in medium-size cities across the interior of the country, where at least two natural gas pipelines are
operational.[citation needed]
In India, the Delhi government under the order of Supreme Court in 2004 made it mandatory for all
city buses and auto rickshaws to run on CNG with the intention of reducing air pollution.
In Pakistan in 2012, the federal government announced plans to gradually phase out CNG over a
period of approximately three years given natural gas shortages which have been negatively affecting
the manufacturing sector.[33] Aside from limiting electricity generation capacity, gas shortages in
Pakistan have also raised the costs of business for key industries including the fertilizer, cement, and
textile sectors.[34]
[edit]Middle East and Africa
Iran has one of the largest fleets of CNG vehicles and CNG distribution networks in the world. There
are 1800 CNG fueling stations, with a total of 10.352 CNG nozzles. The number of CNG burning
vehicles in Iran is about 2.6 million.[35]
Egypt is amongst the top ten countries in CNG adoption, with 128,754 CNG vehicles and 124 CNG
fueling stations. Egypt was also the first nation in Africa and the Middle East to open a public CNG
fueling station in January 1996.[36]
The vast majority 780000 have been produced as dual fuel vehicles by the auto manufacturer in the
last two years, and the remainder have been converted utilizing after market conversion kits in
workshops. There are 750 active refueling stations country wide with an additional 660 refueling
stations under construction and expected to come on stream. Currently the major problem facing the
industry as a whole is the building of refueling stations that is lagging behind dual fuel vehicle
production, forcing many to use petrol instead.
Nigeria CNG started with a pilot project in Benin City Edo State in 2010 by Green Gas Limited. Green
Gas Limited is a Joint Venture Company of Nigerian Gas Company Limited (NGC) & NIPCO PLC. As
at October 2012 about 7 CNG stations have been Built in Benin City Edo State with about 1,000 cars
running on CNG in Benin City Edo state. In Benin City Edo state major companies such as Coca-cola
are using CNG to power their fork-lifts/trucks while Edo City Transport Ltd (ECTS) is also running
some of its busus on CNG.
[edit]Europe
CNG powered bus in Italy
The use of methane (CNG) for vehicles in Italy started in the 1930s and has continued off and on until
today. Since 2008 there have been a large market expansion for natural gas vehicles (CNG and LPG)
caused by the rise of gasoline prices and by the need to reduce air pollution emissions.[37]
Before 1995 the only way to have a CNG-powered car was by having it retrofitted with an after-market
kit. A large producer was Landi Renzo, Tartarini Auto, Prins Autogassystemen, OMVL, BiGAs,... and
AeB for electronic parts used by the most part of kit producer.
Landi Renzo and Tartarini selling vehicles in Asia and South America.
After 1995 bi-fuel cars (gasoline/CNG) became available from several major manufacturers.
Currently Fiat, Opel, Volkswagen, Citroën, Renault, Volvoand Mercedes sell various car models and
small trucks that are gasoline/CNG powered. Usually CNG parts used by major car manufacturers are
actually produced by automotive aftermarket kit manufacturers, e.g. Fiat use Tartarini Auto
components, Volkswagen use Teleflex GFI[38] and Landi Renzo components.
In Italy, there are more than 800 CNG stations.[39] In Germany, CNG-generated vehicles are expected
to increase to two million units of motor-transport by the year 2020. The cost for CNG fuel is between
1/3 and 1/2 compared to other fossil fuels in Europe.[citation needed] in 2008 there are around 800
gas(CNG) stations in Germany
In Portugal there are 4 CNG refueling stations but 3 of them do not sell to the public. Only in Braga
you can find it on the local city bus station (TUB).
In Turkey, Ankara has 1050 CNG buses.
In Hungary there are 4 public CNG refueling stations in the cities Budapest, Szeged, Pécs and Győr.
The public transportation company of Szeged runs buses mainly on CNG.
In Bulgaria, there are 96 CNG refueling stations as of July 2011. One can be found in most of
Bulgaria's big towns.[40] In the capital Sofia there are 22 CNG stations making it possibly the city with
the most publicly available CNG stations in Europe. There are also quite a few in Plovdiv, Stara
Zagora and Veliko Tarnovo as well as in the towns on the Black Sea
- Varna, Burgas, Nesebar andKavarna. CNG vehicles are becoming more and more popular in the
country. The fuel is mostly used by taxi drivers because of its much lower price compared to petrol.
In Macedonia, there is one CNG station located in the capital Skopje, but it is not for public use. Only
twenty buses of the local Public Transport Company have been fitted to use a mixture of diesel and
CNG. The first commercial CNG station in Skopje is in the advanced stage of development and is
expected to start operation in July 2011.
In Serbia, there are 4 public CNG refuelling stations in the capital Belgrade and in the towns
of Pančevo, Kruševac and Čačak.
In Slovenia, there is only 1 public CNG refuelling station in the capital Ljubljana.
In Croatia, there is only one CNG station situated close to the center of Zagreb.[41] At least 60 CNG
buses are in use as a form of a public transport (Zagreb public transport services).
In Estonia, there are two public CNG refuelling stations - one in the country´s capital Tallinn and the
other one in Tartu.[42] From 2011, Tartu has 5 Scania manufactured CNG buses operating it´s inner-
city routes.[43]
In Sweden there are currently 90 CNG filling stations available to the public (as compared to about 10
LPG filling stations), primarily located in the southern and western parts of the country as well the
Mälardalen region[44] Another 70-80 CNG filling stations are under construction or in a late stage of
planning (completions 2009-2010). Several of the planned filling stations are located in the northern
parts of the country, which will greatly improve the infrastructure for CNG car users.[45] There are
approx. 14,500 CNG vehicles in Sweden (2007), of which approx. 13,500 are passenger cars and the
remainder includes buses and trucks.[46] In Stockholm, the public transportation company SL currently
operates 50 CNG buses but have a capacity to operate 500.[47]The Swedish government recently
prolonged its subsidies for the development of CNG filling stations, from 2009-12-31 to 2010-12-31.[48]
In Spain the EMT Madrid bus service use CNG motors in 672 regular buses. Is rare to see another
kind of CNG vehicle, and there's no CNG refueling stations.
As of 2010, there are 25 public CNG filling stations in the Czech Republic, mainly in the big cities.[49] Local bus manufacturers SOR Libchavy and Tedom produce CNG versions of their vehicles, with
roof-mounted tanks.
[edit]North America
The Honda Civic GX is factory-built to run on CNG and it is available in several U.S. regional markets.
Buses powered with CNG are common in the United States.
[edit]Canada
Natural Gas has been used as a motor fuel in Canada for over 20 years.[50] With assistance from
federal and provincial research programs, demonstration projects, and NGV market deployment
programs during the 1980s and 1990s, the population of light-duty NGVs grew to over 35,000 by the
early 1990s. This assistance resulted in a significant adoption of natural gas transit buses as well.[51]
The NGV market started to decline after 1995, eventually reaching today’s vehicle population of about
12,000.[51]
This figure includes 150 urban transit buses, 45 school buses, 9,450 light-duty cars and trucks, and
2,400 forklifts and ice-resurfacers. The total fuel use in all NGV markets in Canada was 1.9 petajoules
(PJs) in 2007 (or 54.6 million litres of gasoline litres equivalent), down from 2.6 PJs in 1997. Public
CNG refuelling stations have declined in quantity from 134 in 1997 to 72 today. There are 22 in British
Columbia, 12 in Alberta, 10 in Saskatchewan, 27 in Ontario, and 1 in Québec. There are only 12
private fleet stations.[15]
Canadian industry has developed CNG-fueled truck and bus engines, CNG-fueled transit buses, and
light trucks and taxis.
Fuelmaker Corporation of Toronto, the Honda-owned manufacturer of CNG auto refueling units, was
forced into bankruptcy by parent Honda USA for an unspecified reason in 2009.[52] The various assets
of Fuelmaker were subsequently acquired by Fuel Systems Corporation of Santa Ana, California.
[edit]United States
Similar to Canada, the United States has implemented various NGV initiatives and programs since
1980, but has had limited success in sustaining the market. There were 105,000 NGVs in operation in
2000; this figure peaked at 121,000 in 2004, and decreased to 110,000 in 2009.[53]
In the United States, federal tax credits are available for buying a new CNG vehicle. Use of CNG
varies from state to state; only 34 states have at least one CNG fueling site.[54] In California, CNG is
used extensively in local city and county fleets, as well as public transportation (city/school buses),
and there are 90 public fueling stations in southern California alone, although as of 2011 CNG fueling
stations in the rest of the state of California, Nevada and Arizona are few and far between.[55] Compressed natural gas is available at 30-60% less than the cost of gasoline, as a rule of thumb,
in much of California.
The Massachusetts Bay Transportation Authority was running 360 CNG buses as early as in 2007,
and is the largest user in the state.[56]
The City of Harrisburg, Pennsylvania has switched some of the city's vehicles to compressed natural
gas in an effort to save money on fuel costs. Trucks used by the city's street and water, sewer and
gas departments have been converted from gasoline to CNG.[57]
Personal use of CNG is a small niche market currently, though with current tax incentives and a
growing number of public fueling stations available, it is experiencing unprecedented growth. The
state of Utah offers a subsidised statewide network of CNG filling stations at a rate of $0.85/gge,[58] while gasoline is above $4.00/gal. Elsewhere in the nation, retail prices average around $2.50/gge,
with home refueling units compressing gas from residential gas lines for approx $1.50/gge. Other than
aftermarket conversions, and government used vehicle auctions, the only currently[when?] produced
CNG vehicle in the United States is the Honda Civic GX sedan, which is made in limited numbers and
available only in a few states.
An initiative, known as Pickens Plan, calls for the expansion of the use of CNG as a standard fuel for
heavy vehicles has been recently started by oilman and entrepreneur T. Boone Pickens. California
voters defeated Proposition 10 in the 2008 General Election by a significant (59.8% to 40.2%) margin.
Proposition 10 was a $5 billion bond measure that, among other things, would have given rebates to
state residents that purchase CNG vehicles.
Congress has encouraged conversion of cars to CNG with a tax credits of up to 50% of the auto
conversion cost and the CNG home filling station cost. However, while CNG is much cleaner fuel, the
conversion requires a type certificate from the EPA. Meeting the requirements of a type certificate can
cost up to $50,000. Other non-EPA approved kits are available. A complete and safe aftermarket
conversion using a non-EPA approved kit can be achieved for as little as $400 without the cylinder.[59]
[edit]Oceania
K230UB CNG bus currently used as part of the "Scania Koala CNG Bus Trial" atACTION in Canberra.
During the 1970s and 1980s, CNG was commonly used in New Zealand in the wake of the oil crises,
but fell into decline after petrol prices receded. At the peak of natural gas use, 10 percent of New
Zealand's cars were converted, around 110,000 vehicles.[60]
A Mercedes-Benz OC500LE (withCustom Coaches bodywork) running on CNG, operated by Sydney Buses in Sydney,
Australia.
Brisbane Transport and Transperth in Australia have both adopted a policy of purchasing only CNG
buses in future. Transperth is purchasing 451 Mercedes-Benz OC500LE buses and is undertaking
trials with articulated CNG buses from Scania, MAN, and Irisbus, while Brisbane Transport has
purchased 216 Scania L94UB and 240 MAN 18.310 models as well as 30 MAN NG 313 articulated
CNG buses. The State Transit Authority of New South Wales (operating under the name "Sydney
Buses") operates 102 Scania L113CRBbuses, two Mercedes-Benz O405 buses and 300 Mercedes-
Benz O405NH buses and are now taking delivery of 255 Euro 5-compliant Mercedes-Benz
OC500LEs.[61]
In the 1990s Benders Busways of Geelong, Victoria trialled CNG buses for the Energy Research and
Development Corporation.[62]
Martin Ferguson, Ollie Clark, and Noel Childs featured on ABC 7.30 Report raising the issue of CNG
as an overlooked transport fuel option in Australia, highlighting the large volumes of LNG currently
being exported from the North West Shelf in light of the cost of importing crude oil to Australia.[63]
[edit]Deployments
AT&T ordered 1,200 CNG-powered cargo vans from General Motors in 2012. It is the largest-ever
order of CNG vehicles from General Motors to date.[64] AT&T has announced its intention to invest up
to $565 million to deploy approximately 15,000 alternative fuel vehicles over a 10-year period through
2018, will use the vans to provide and maintain communications, high-speed Internet and television
services for AT&T customers.[65]
[edit]DNG
DNG, or Diesel Natural Gas, is a system which can be installed on trucks that mixed diesel fuel and
up to 70% natural gas. It is designed be retrofitted on existing trucks.[66]
