If you put Mothballs in a gas tank it raises the fuels effective octane a lot. But causes detonation which will trash your motor in short order.
-57--57 °C, 216.0-216.6 K, -71--70 °F
125-126 °C, 398.2-399.2 K, 257-259 °F
is a hydrocarbon and an alkane with the chemical formula C8
, and the condensed structural formula CH3
. Octane has many structural isomers that differ by the amount and location of branching in the carbon chain. One of these isomers, 2,2,4-trimethylpentane (isooctane) is used as one of the standard values in the octane rating scale.
As with all low-molecular weight hydrocarbons, octane and its isomers are very flammable and are components of gasoline (petrol).
"Octane" is colloquially used as a short form of "octane rating" (named for the ability of octane's branched-chain isomers, especially isooctane, to reduce engine knock), particularly in the expression "high octane." However, components of gasoline other than isomers of octane can also contribute to a high octane rating, while some isomers of octane can lower it, and n
-octane itself has a negative octane rating.
Octane became well known in American popular culture in the mid- and late 1960s, when gasoline companies boasted of "high octane" levels in their gasoline advertisements.
These commercials disappeared by the time of the 1973 Oil Crisis, which spared gasoline companies the need to compete in advertising. "Octane" was rarely cited in non-technical contexts over the next two decades.
The compound adjective "high-octane" was first used in its figurative sense (i.e., without reference to gasoline) in a book review of Michael Crichton's novel Jurassic Park
(1990), which appeared in the newspaper New York Newsday
[ The review by Gregory Feeley called the novel "intellectually provocative, high-octane entertainment", and was quoted the following year in the front matter of the novel's paperback edition, which sold more than 15 million copies in the United States. By the mid-1990s, the phrase was commonly being used as an intensifier and has found a place in modern English vernacular.
Octane has 18 structural isomers (24 including stereoisomers):
-188 °C, 85.5 K, -306 °F
-42--42 °C, 230.9-231.11 K, -44--44 °F
is a three-carbon alkane with the molecular formula , normally a gas, but compressible to a transportable liquid. A by-product of natural gas processing and petroleum refining, it is commonly used as a fuel for engines, oxy-gas torches, barbecues, portable stoves, and residential central heating. Propane is one of a group of liquefied petroleum gases. The others include butane, propylene, butadiene, butylene, isobutylene and mixtures thereof.
Propane containing too much propene (also called propylene) is not suited for most vehicle fuels. HD-5 is a specification which establishes a maximum concentration of 5% propene in propane. Propane and other LP gas specifications are established in ASTM D-1835. All propane fuels include an odorant, almost always ethanethiol, so that people can easily smell the gas in case of a leak. Propane as HD-5 was originally intended for use as vehicle fuel. HD-5 is currently being used in all propane applications.
Propane was first identified as a volatile component in gasoline by Walter O. Snelling of the U.S. Bureau of Mines in 1910. The volatility of these lighter hydrocarbons caused them to be known as "wild" because of the high vapor pressures of unrefined gasoline. On March 31, the New York Times
reported on Snelling's work with liquefied gas and that "...a steel bottle will carry enough gas to light an ordinary home for three weeks."
It was during this time that Snelling, in cooperation with Frank P. Peterson, Chester Kerr, and Arthur Kerr, created ways to liquefy the LP gases during the refining of natural gasoline. Together they established American Gasol Co., the first commercial marketer of propane. Snelling had produced relatively pure propane by 1911, and on March 25, 1913, his method of processing and producing LP gases was issued patent #1,056,845. A separate method of producing LP gas through compression was created by Frank Peterson and patented]
[ in 1912.
The 1920s saw increased production of LP gas, with the first year of recorded production totaling 223,000 US gallons (840 m3) in 1922. In 1927, annual marketed LP gas production reached 1 million US gallons (3,800 m3), and by 1935, the annual sales of LP gas had reached 56 million US gallons (210,000 m3). Major industry developments in the 1930s included the introduction of railroad tank car transport, gas odorization, and the construction of local bottle-filling plants. The year 1945 marked the first year that annual LP gas sales reached a billion gallons. By 1947, 62% of all U.S. homes had been equipped with either natural gas or propane for cooking.
In 1950, 1,000 propane-fueled buses were ordered by the Chicago Transit Authority, and by 1958, sales in the U.S. had reached 7 billion US gallons (26,000,000 m3) annually. In 2004 it was reported to be a growing $8-billion to $10-billion industry with over 15 billion US gallons (57,000,000 m3) of propane being used annually in the U.S.
The "prop-" root found in "propane" and names of other compounds with three-carbon chains was derived from "propionic acid".
Propane is produced as a by-product of two other processes, natural gas processing and petroleum refining. The processing of natural gas involves removal of butane, propane, and large amounts of ethane from the raw gas, in order to prevent condensation of these volatiles in natural gas pipelines. Additionally, oil refineries produce some propane as a by-product of cracking petroleum into gasoline or heating oil. The supply of propane cannot easily be adjusted to meet increased demand, because of the by-product nature of propane production. About 90% of U.S. propane is domestically produced.]
[ The United States imports about 10% of the propane consumed each year, with about 70% of that coming from Canada via pipeline and rail. The remaining 30% of imported propane comes to the United States from other sources via ocean transport.
After it is produced, North American propane is stored in huge salt caverns. Examples of these are Fort Saskatchewan, Alberta; Mont Belvieu, Texas and Conway, Kansas. These salt caverns were hollowed out in the 1940s, and they can store 80,000,000 barrels (13,000,000 m3) or more of propane. When the propane is needed, much of it is shipped by pipelines to other areas of the United States. Propane is also shipped by truck, ship, barge, and railway to many U.S. areas.
Propane undergoes combustion reactions in a similar fashion to other alkanes. In the presence of excess oxygen, propane burns to form water and carbon dioxide.
When not enough oxygen is present for complete combustion, incomplete combustion occurs when propane burns and forms water, carbon monoxide, and carbon dioxide.
Unlike natural gas, propane is heavier than air (1.5 times as dense). In its raw state, propane sinks and pools at the floor. Liquid propane will flash to a vapor at atmospheric pressure and appears white due to moisture condensing from the air.
When properly combusted, propane produces about 50 MJ/kg. The gross heat of combustion of one normal cubic meter of propane is around 91 megajoules.
Propane is nontoxic; however, when abused as an inhalant it poses a mild asphyxiation risk through oxygen deprivation. Commercial products contain hydrocarbons beyond propane, which may increase risk. Commonly stored under pressure at room temperature, propane and its mixtures expand and cool when released and may cause mild frostbite.
Propane combustion is much cleaner than gasoline combustion, though not as clean as natural gas combustion. The presence of C–C bonds, plus the multiple bonds of propylene and butylene, create organic exhausts besides carbon dioxide and water vapor during typical combustion. These bonds also cause propane to burn with a visible flame.
Greenhouse gas emissions factors for propane are 62.7 kg CO2
/ mBTU or 1.55 kg of CO2
per liter or 73.7 kg/GJ.]
The energy density of propane is 46.44 megajoules per kilogram (91,690 BTU per US gallon, 2220 kJ/mol, 50.35 kJ/g).
The density of liquid propane at 25 °C (77 °F) is 0.493 g/cm3, which is equivalent to 4.11 pounds per U.S. liquid gallon or 493 grams per liter. Propane expands at 1.5% per 10 °F. Thus, liquid propane has a density of approximately 4.2 pounds per gallon at 60 °F.
Propane is a popular choice for barbecues and portable stoves because the low boiling point of makes it vaporize as soon as it is released from its pressurized container. Therefore, no carburetor or other vaporizing device is required; a simple metering nozzle suffices. Propane powers some locomotives, buses, forklifts, taxis and ice resurfacing machines and is used for heat and cooking in recreational vehicles and campers.
Propane is generally stored and transported in steel cylinders as a liquid with a vapor space above the liquid. The vapor pressure in the cylinder is a function of temperature. When gaseous propane is drawn at a high rate, the latent heat of vaporisation required to create the gas will cause the bottle to cool. (This is why water often condenses on the sides of the bottle and then freezes). In addition, the lightweight, high-octane compounds vaporize before the heavier, low-octane ones. Thus the ignition properties change as the tank empties. For these reasons, the liquid is often withdrawn using a dip tube. Propane is used as fuel in furnaces for heat, in cooking, as an energy source for water heaters, laundry dryers, barbecues, portable stoves, and motor vehicles.
Commercially available "propane" fuel, or LPG, is not pure. Typically in the USA and Canada, it is primarily propane (at least 90%), with the rest mostly ethane, propylene, butane, and odorants including ethyl mercaptan. This is the HD-5 standard, (H
maximum allowable propylene content, and no more than 5% butanes and ethane) defined by the American Society for Testing and Materials by its Standard 1835 for internal combustion engines. Not all products labelled "propane" conform to this standard however. In Mexico, for example, where much of the bottled liquified gas sold is in fact butane, gas labelled "propane" may actually consist of 60% propane and 40% butane.
Propane use is growing rapidly in non-industrialized areas of the world. Propane is replacing wood and other traditional fuel sources in such places, where it is now sometimes called "cooking gas." The "propane" sold outside North America is actually a mixture of propane and butane. The warmer the country, the higher the butane content, commonly 50/50 and sometimes reaching 75% butane. Usage is calibrated to the different-sized nozzles found in non-U.S. grills.]
[ Americans who take their grills overseas — such as military personnel — can find U.S.-specification propane at AAFES military post exchanges.
North American industries using propane include glass makers, brick kilns, poultry farms and other industries that need portable heat.
In rural areas of North America, as well as northern Australia and some parts of southern India propane is used to heat livestock facilities, in grain dryers, and other heat-producing appliances. When used for heating or grain drying it is usually stored in a large, permanently placed cylinder which is recharged by a propane-delivery truck. As of 2007[update], 9.7 million American households use propane as their primary heating fuel.
In North America, local delivery trucks with an average tank size of 3,000 US gallons (11,000 L), fill up large tanks that are permanently installed on the property, or other service trucks exchange empty cylinders of propane with filled cylinders. Large tractor-trailer trucks, with an average tank size of 10,000 US gallons (38,000 L), transport the propane from the pipeline or refinery to the local bulk plant. The bobtail and transport are not unique to the North American market, though the practice is not as common elsewhere, and the vehicles are generally referred to as tankers
. In many countries, propane is delivered to consumers via small or medium-sized individual tanks.
Propane is also instrumental in providing off-the-grid refrigeration, usually by means of a gas absorption refrigerator.
Blends of pure, dry "isopropane" (R-290a) (isobutane/propane mixtures) and isobutane (R-600a) have negligible ozone depletion potential and very low Global Warming Potential (having a value of 3.3 times the GWP of carbon dioxide) 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.
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.
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.
Propane is also being used increasingly for vehicle fuels. In the U.S., over 190,000 on-road vehicles use propane, and over 450,000 forklifts use it for power. It is the third most popular vehicle fuel in America, behind gasoline and diesel. In other parts of the world, propane used in vehicles is known as autogas. In 2007, about 13 million vehicles worldwide use autogas.
The advantage of propane in cars is its liquid state at a moderate pressure. This allows fast refill times, affordable fuel tank construction, and price ranges typically just over half that of gasoline. Meanwhile it is noticeably cleaner (both in handling, and in combustion), results in less engine wear (due to carbon deposits) without diluting engine oil (often extending oil-change intervals), and until recently was a relative bargain in North America. Octane rating of propane is relatively high at 110. In the United States the propane fueling infrastructure is the most developed of all alternative vehicle fuels. Many converted vehicles have provisions for topping off from "barbecue bottles". Purpose-built vehicles are often in commercially owned fleets, and have private fueling facilities. A further saving for propane fuel vehicle operators, especially in fleets, is that pilferage is much more difficult than with gasoline or diesel fuels.
Propane is also used as fuel for small engines, especially those used indoors or in areas with insufficient fresh air and ventilation to carry away the more toxic exhaust of an engine running on gasoline or diesel. More recently, there have been lawn care products like string trimmers, lawn mowers and leaf blowers intended for outdoor use but fueled by propane to reduce air pollution.]
Propane is denser than air. If a leak in a propane fuel system occurs, the gas will have a tendency to sink into any enclosed area and thus poses a risk of explosion and fire. The typical scenario is a leaking cylinder stored in a basement; the propane leak drifts across the floor to the pilot light on the furnace or water heater, and results in an explosion or fire. This property makes propane generally unsuitable as a fuel for boats.
Propane is bought and stored in a liquid form (LPG), and thus fuel energy can be stored in a relatively small space. Compressed Natural Gas (CNG), largely methane, is another gas used as fuel, but it cannot be liquefied by compression at normal temperatures, as these are well above its critical temperature. It therefore requires very high pressure to be stored as a liquid, which poses the hazard that, in an accident, just as with any compressed gas tank (such as a CO2
tank used for a soda concession) a CNG tank may burst with great force, or leak rapidly enough to become a self-propelled missile. Therefore, CNG is much less efficient to store, due to the large tank volume required. Another form of storing natural gas is as a low temperature liquid in insulated containers as Liquefied Natural Gas (LNG). This form of storage is at low pressure and is around 3.5 times as efficient as storing it as CNG. Unlike propane, if a spill occurs LNG will evaporate and dissipate harmlessly because it is lighter than air. Propane is much more commonly used to fuel vehicles than is natural gas because the equipment required costs less. Propane requires just 1,220 kilopascals (177 psi) of pressure to keep it liquid at .
As of July 2013[update], the retail cost of propane was approximately $1.97 USD per gallon, or roughly $12.95 per 1 million BTUs.
Octane rating or octane number is a standard measure of the performance of a motor or aviation fuel. The higher the octane number, the more compression the fuel can withstand before detonating. In broad terms, fuels with a higher octane rating are used in high-compression engines that generally have higher performance. In contrast, fuels with lower octane numbers (but higher cetane numbers) are ideal for diesel engines. Use of gasoline with lower octane numbers may lead to the problem of engine knocking.
Octanes are a family of hydrocarbon that are typical components of gasoline. They are colourless liquids that boil around 125 °C (260 °F). One member of the octane family, isooctane, is used as a reference standard to benchmark the tendency of gasoline/petrol or LPG fuels to resist self-igniting. In a normal spark-ignition engine, the air-fuel mixture is heated due to being compressed and is then triggered to burn (relatively) slowly by the spark plug and ignition system. If it is heated and/or compressed too much, then it will explode when triggered (detonate), or even self-ignite before the ignition system sparks. This causes much higher pressures than engine components are designed for and can cause a "knocking" or "pinging" sound if light, or major engine damage if severe. This can break connecting rods, melt pistons, melt or break valves or other components. The octane rating is a measure of how resistant a fuel is to spontaneously or explosively ignite under such conditions. The higher the number, the more resistant the fuel is. Engines that have aggressive designs (high compression pistons, high intake density and/or temperature) or unusual operating conditions (low-speed, air-cooled engines such as small aircraft) require higher octane fuels.
The most typically used engine management systems found in automobiles today have a knock sensor that monitors if knock is being produced by the fuel being used. In modern computer controlled engines, the ignition timing will be automatically altered by the fuel management system to reduce the pre-ignition to an acceptable level.
The octane rating of gasoline is measured in a test engine and is defined by comparison with the mixture of 2,2,4-trimethylpentane (iso-octane) and heptane that would have the same anti-knocking capacity as the fuel under test: the percentage, by volume, of 2,2,4-trimethylpentane in that mixture is the octane number of the fuel. For example, petrol with the same knocking characteristics as a mixture of 90% iso-octane and 10% heptane would have an octane rating of 90. A rating of 90 does not mean that the petrol contains just iso-octane and heptane in these proportions, but that it has the same detonation resistance properties. Because some fuels are more knock-resistant than iso-octane, the definition has been extended to allow for octane numbers greater than 100.
Octane ratings are not indicators of the energy content of fuels. (See section 4 of this page and heating value). It is only a measure of the fuel's tendency to burn in a controlled manner, rather than exploding in an uncontrolled manner. Where the octane number is raised by blending in ethanol, energy content per volume is reduced. Ethanol BTUs can be compared with gasoline BTUs in heat of combustion tables.
It is possible for a fuel to have a Research Octane Number (RON) more than 100, because ISO-octane is not the most knock-resistant substance available. Racing fuels, avgas, LPG and alcohol fuels such as methanol may have octane ratings of 110 or significantly higher. Typical "octane booster" gasoline additives include MTBE, ETBE, isooctane and toluene. Lead in the form of tetraethyllead was once a common additive, but its use for fuels for road vehicles has been progressively phased-out worldwide, beginning in the 1970s.
The most common type of octane rating worldwide is the Research Octane Number (RON). RON is determined by running the fuel in a test engine with a variable compression ratio under controlled conditions, and comparing the results with those for mixtures of iso-octane and n-heptane.
There is another type of octane rating, called Motor Octane Number (MON), which is a better measure of how the fuel behaves when under load, as it is determined at 900 rpm engine speed, instead of the 600 rpm for RON. MON testing uses a similar test engine to that used in RON testing, but with a preheated fuel mixture, higher engine speed, and variable ignition timing to further stress the fuel's knock resistance. Depending on the composition of the fuel, the MON of a modern gasoline will be about 8 to 10 points lower than the RON, however there is no direct link between RON and MON. Normally, fuel specifications require both a minimum RON and a minimum MON.][
In most countries, including Australia and all of those in Europe, the "headline" octane rating shown on the pump is the RON, but in Canada, the United States, Brazil, and some other countries, the headline number is the average of the RON and the MON, called the Anti-Knock Index (AKI, and often written on pumps as (R+M)/2). It may also sometimes be called the Pump Octane Number (PON).
Because of the 8 to 10 point difference noted above, the octane rating shown in Canada and the United States is 4 to 5 points lower than the rating shown elsewhere in the world for the same fuel. This difference is known as the fuel's sensitivity, and is not typically published for those countries that use the Anti-Knock Index labelling system.
See the table in the following section for a comparison.
Another type of octane rating, called Observed Road Octane Number (RdON), is derived from testing gasolines in real world multi-cylinder engines, normally at wide open throttle. It was developed in the 1920s and is still reliable today. The original testing was done in cars on the road but as technology developed the testing was moved to chassis dynamometers with environmental controls to improve consistency.
Gasoline used in piston aircraft common in general aviation have slightly different methods of measuring the octane of the fuel. Similar to AKI, it has two different ratings, although it is referred to only by the lower of the two. One is referred to as the "aviation lean" rating and is the same as the MON of the fuel up to 100. The second is the "aviation rich" rating and corresponds to the octane rating of a test engine under forced induction operation common in high-performance and military piston aircraft. This utilizes a supercharger, and uses a significantly richer fuel/air ratio for improved detonation resistance.
The most commonly used current fuel 100LL, has an aviation lean rating of 100 octane, and an aviation rich rating of 130.
The RON/MON values of n-heptane and iso-octane are exactly 0 and 100, respectively, by the definition of octane rating. The following table lists octane ratings for various other fuels.
Higher octane ratings correlate to higher activation energies: This being the amount of applied energy required to initiate combustion. Since higher octane fuels have higher activation energy requirements, it is less likely that a given compression will cause uncontrolled ignition, otherwise known as autoignition or detonation.
The compression ratio is directly related to power and to thermodynamic efficiency of an internal combustion engine (see Otto-cycle). Engines with higher compression ratios develop more area under the Otto-Cycle curve, thus they extract more energy from a given quantity of fuel.
During the compression stroke of an internal combustion engine, as the air / fuels mix is compressed its temperature rises (PV=nRT).
A fuel with a higher octane rating is less prone to auto-ignition and can withstand a greater rise in temperature during the compression stroke of an internal combustion engine without auto-igniting, thus allowing more power to be extracted from the Otto-Cycle.
If during the compression stroke the air / fuel mix reaches a temperature greater than the auto-ignition temperature of the fuel, the fuel self or auto-ignites. When auto-ignition occurs (before the piston reaches the top of its travel) the up-rising piston is then attempting to squeeze the rapidly heating fuel charge. This will usually destroy an engine quickly if allowed to continue.
There are two types of induction systems on internal combustion engines: Normally aspirated engine (air is sucked in using the engine's pistons), or forced induction engines (see supercharged or turbocharged engines).
In the case of the normally aspirated engine, at the start of the compression stroke the cylinder air / fuel volume is very low, this translates into a low starting pressure. As the piston travels upward, a compression ratio of 10:1 in a normally aspirated engine will most likely not start auto-ignition. But 11:1 may. In a forced induction engine where at the start of the compression stroke the cylinder pressure is already raised (having a greater volume of air / fuel) Exp. 2 Bar (14.7Psi), the starting pressure or air / fuel volume would be 2 times that of the normally aspirated engine. This would translate into an effective compression ratio of 20:1 vs. 10:1 for the normally aspirated. This is why many forced induction engines have compression ratios in the 8:1 range.
Many high-performance engines are designed to operate with a high maximum compression, and thus demand fuels of higher octane. A common misconception is that power output or fuel efficiency can be improved by burning fuel of higher octane than that specified by the engine manufacturer. The power output of an engine depends in part on the energy density of the fuel being burnt. Fuels of different octane ratings may have similar densities, but because switching to a higher octane fuel does not add more hydrocarbon content or oxygen, the engine cannot develop more power.
However, burning fuel with a lower octane rating than that for which the engine is designed often results in a reduction of power output and efficiency. Many modern engines are equipped with a knock sensor (a small piezoelectric microphone), which sends a signal to the engine control unit, which in turn retards the ignition timing when detonation is detected. Retarding the ignition timing reduces the tendency of the fuel-air mixture to detonate, but also reduces power output and fuel efficiency. Because of this, under conditions of high load and high temperature, a given engine may have a more consistent power output with a higher octane fuel, as such fuels are less prone to detonation. Some modern high performance engines are actually optimized for higher than pump premium (93 AKI in the US). The 2001 - 2007 BMW M3 with the S54 engine is one such car. Car and Driver magazine tested a car using a dynamometer, and found that the power output increased as the AKI was increased up to approximately 96 AKI.
Most fuel filling stations have two storage tanks (even those offering 3 or 4 octane levels): those motorists who purchase intermediate grade fuels are given a mixture of higher and lower octane fuels. "Premium" grade is fuel of higher octane, and the minimum grade sold is fuel of lower octane. Purchasing 91 octane fuel (where offered) simply means that more fuel of higher octane is blended with commensurately less fuel of lower octane, than when purchasing a lower grade. The detergents and other additives in the fuel are often, but not always, identical.
The octane rating was developed by chemist Russell Marker at the Ethyl Corporation in 1926. The selection of n-heptane as the zero point of the scale was due to its availability in high purity. Other isomers of heptane produced from crude oil have greatly different ratings.
The selection of octane ratings available at the pump can vary greatly from region to region.
Octane ratings of some hydrocarbons
Information in general
Liquefied petroleum gas, also called LPG, GPL, LP Gas, liquid petroleum gas or simply propane or butane, is a flammable mixture of hydrocarbon gases used as a fuel in heating appliances and vehicles. It is increasingly used as an aerosol propellant and a refrigerant, replacing chlorofluorocarbons 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 (), primarily butane () and, most commonly, mixes including both propane and butane, depending on the season — in winter more propane, in summer more butane. 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) and the American Society of Testing and Materials (ASTM). 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, although neither is currently being utilized.
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 no soot 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). 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 for gasoline).
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 , and approximately 2.2 megapascals (320 psi) for pure propane at . 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 within the explosive limits and 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.
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.
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. The studies were split on CO emissions, with one finding significant increases, and the other finding slight increases at low engine load but a considerable decrease at high engine load. 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.
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.
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.
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. 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.
LPG is used for cooking in many countries for economic reasons, for convenience or because it is the preferred fuel source.
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. 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 class voting 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, with the exception of the cities of Rio de Janeiro and São Paulo which have a natural gas pipeline infrastructure. Poor families receive a government grant ("Vale Gás") used exclusively for the acquisition of LPG.
LPG is commonly used in North America for outdoor grilling.
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:
According to 2010-2012 estimates, proven world reserves of natural gas — from which most LPG is derived — stand at 300 trillion cubic meters (10,600 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.][
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.
Commercially available LPG is currently derived from fossil fuels. Burning LPG releases carbon dioxide, a greenhouse gas. The reaction also produces some carbon monoxide. LPG does, however, release less per unit of energy than does coal or oil. It emits 81% of the 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.][ 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.
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 vapor 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.
, or petrol
, is a transparent, petroleum-derived oil that is used primarily as a fuel in internal combustion engines. It consists mostly of organic compounds obtained by the fractional distillation of petroleum, enhanced with a variety of additives. Some gasolines also contain ethanol as an alternative fuel. In North America, the term gasoline
is often shortened in colloquial usage to gas
, while petrol
is the common name in the UK, Republic of Ireland, Australia and in most of the other Commonwealth countries. Under normal ambient conditions, its material state is liquid, unlike liquefied petroleum gas or natural gas.
Gasoline is more volatile than diesel oil, Jet-A, or kerosene, not only because of the base constituents, but also because of additives. Volatility is often controlled by blending with butane, which boils at −0.5 °C. The volatility of gasoline is determined by the Reid vapor pressure (RVP) test. The desired volatility depends on the ambient temperature. In hot weather, gasoline components of higher molecular weight and thus lower volatility are used. In cold weather, too little volatility prevents cars from starting.
In hot weather, excessive volatility causes vapor lock
, where combustion fails to occur, because the liquid fuel has changed to a gaseous state in the fuel lines, rendering the fuel pump ineffective and starving the engine of fuel. This effect mainly applies to camshaft-driven (engine mounted) fuel pumps that lack a fuel return line. Vehicles with fuel injection require that the fuel be pressurised within a set range. Because the camshaft speed is nearly zero before the engine is started, an electric pump is used. It is located in the fuel tank so the fuel may also cool the high-pressure pump. Pressure regulation is achieved by returning unused fuel to the tank. Therefore, vapor lock is almost never a problem in a vehicle with fuel injection.
In the US, volatility is regulated to reduce the emission of unburned hydrocarbons by the use of so-called reformulated gasoline that is less prone to evaporation. In Australia, summer gasoline volatility limits are set by state governments and vary among states. Most countries simply have a summer, winter, and perhaps intermediate limit.
Volatility standards may be relaxed (allowing more gasoline components into the atmosphere) during gasoline shortages. For example, on 31 August 2005, in response to Hurricane Katrina, the US permitted the sale of nonreformulated gasoline in some urban areas, effectively permitting an early switch from summer to winter-grade gasoline. As mandated by EPA administrator Stephen L. Johnson, this "fuel waiver" was made effective until 15 September 2005.
Modern automobiles are also equipped with an evaporative emissions control system ( 'EVAP system' in automotive jargon), which collects evaporated fuel from the fuel tank in a charcoal-filled canister while the engine is stopped, and then releases the collected vapors to the engine for consumption when the engine is running (usually after it has reached normal operating temperature). The evaporative emissions control system also includes a sealed gas cap to prevent vapors from escaping via the fuel filler tube.
Spark ignition engines are designed to burn gasoline in a controlled process called deflagration. In some cases, however, the unburned mixture can autoignite (detonate from pressure alone, rather than ignite from the spark plug at exactly the right time), which causes rapid heat release and can damage the engine. This phenomenon is often referred to as engine knocking or end-gas knock. One way to reduce knock in spark ignition engines is to increase the gasoline's resistance to autoignition, which is expressed by its octane rating.
Octane rating is measured relative to a mixture of 2,2,4-trimethylpentane (an isomer of octane) and n-heptane. There are different conventions for expressing octane ratings, so a fuel may have several different octane ratings based on the measure used. Research octane number (RON) for commercially-available gasoline varies by country. In Finland, Sweden, and Norway, 95 RON is the standard for regular unleaded gasoline and 98 RON is also available as a more expensive option. In the UK, ordinary regular unleaded gasoline is 91 RON (not commonly available), premium unleaded gasoline is always 95 RON, and super unleaded is usually 97-98 RON. However, both Shell and BP produce fuel at 102 RON for cars with high-performance engines, and the supermarket chain Tesco began in 2006 to sell super unleaded gasoline rated at 99 RON. In the US, octane ratings in unleaded fuels can vary between 86 and 87 AKI (91-92 RON) for regular, through 89-90 AKI (94-95 RON) for mid-grade (European premium), up to 90-94 AKI (95-99 RON) for premium (European super).
The octane rating became important as the military sought higher output for aircraft engines in the late 1930s and the 1940s. A higher octane rating allows a higher compression ratio or supercharger boost, and thus higher temperatures and pressures, which translate to higher power output. Some scientists even predicted that a nation with a good supply of high octane gasoline would have the advantage in air power. In 1943, the Rolls Royce Merlin aero engine produced 1,320 horsepower (984 kW) using 100 RON fuel from a modest 27 liter displacement. Towards the end of the second world war, experiments were conducted using 150 RON fuel.
Quality gasoline should be stable almost indefinitely if stored properly. Such storage should be in an airtight container (to prevent oxidation or water vapors mixing), and which can withstand the vapor pressure of the gasoline without venting ( to prevent the loss of the more volatile fractions), and at a stable cool temperature (to reduce the excess pressure from liquid expansion, and to reduce the rate of any decomposition reactions). When gasoline is not stored correctly, gums and solids may be created, which can corrode system components and accumulate on wetted surfaces, resulting in a condition called "stale fuel". Gasoline containing ethanol is especially subject to absorbing atmospheric moisture, then forming gums, solids, or two phases (a hydrocarbon phase floating on top of a water-alcohol phase).
The presence of these degradation products in fuel tank, lines, carburetor or fuel injection components makes it harder to start the engine, or causes reduced engine performance. Oon resumption of regular engine use, the buildup is often eventually cleaned out by the flow of fresh gasoline. The addition of a fuel stabilizer to gasoline can extend the life of fuel that is not or cannot be stored properly. Some typical fuel stabilizers are proprietary mixtures containing mineral spirits, isopropyl alcohol, 1,2,4-trimethylbenzene,or other additives. Fuel stabilizer is commonly used for small engines, such as lawnmower and tractor engines, especially when their use is seasonal (low to no use for one or more seasons of the year). Users have been advised to keep gasoline containers more than half full and properly capped to reduce air exposure, to avoid storage at high temperatures, to run an engine for ten minutes to circulate the stabilizer through all components prior to storage, and to run the engine at intervals to purge stale fuel from the carburetor.
Energy is obtained from the combustion of gasoline by the conversion of a hydrocarbon to carbon dioxide and water. The combustion of octane follows this reaction:
gasoline contains about 35 MJ/L (46.6 MJ/kg, or 9.7 kWh/L, 13 kWh/kg, , ). gasoline blends differ, and therefore actual energy content varies according to the season and producer by up to 4% more or less than the average, according to the US EPA. On average, about 74 L of gasoline (19.5 US gal, 16.3 imp gal) are available from a barrel of crude oil (about 46% by volume), varying due to quality of crude and grade of gasoline. The remainder are products ranging from tar to naptha.
A high-octane-rated fuel, such as liquefied petroleum gas (LPG) has an overall lower power output at the typical 8:1 compression ratio of a gasoline engine. However, with an engine tuned to the use of LPG (i.e. via higher compression ratios, such as 12:1 instead of 8:1), this lower power output can be eliminated. This is because higher-octane fuels allow for a higher compression ratio without knocking, resulting in a higher cylinder temperature, which improves efficiency. Also, increased mechanical efficiency is created by a higher compression ratio through the concomitant higher expansion ratio on the power stroke, which is by far the greater effect. The higher expansion ratio extracts more work from the high-pressure gas created by the combustion process. The applicable formula is
. An Atkinson cycle engine uses the timing of the valve events to produce the benefits of a high expansion ratio without the disadvantages, chiefly detonation, of a high compression ratio. A high expansion ratio is also one of the two key reasons for the efficiency of Diesel engines, along with the elimination of pumping losses due to throttling of the intake air flow. A high compression ratio can be viewed as a necessary evil to have a high expansion ratio.]
The lower energy content (per liter) of LPG in comparison to gasoline is due mainly to its lower density. Energy content per kilogram is higher than for gasoline (higher hydrogen to carbon ratio, for an example see Standard enthalpy of formation).
The density of gasoline ranges from 0.71–0.77 kg/l ( ; 0.026 lb/3in; 6.073 lb/US gal; 7.29 lb/imp gal), higher densities having a greater volume of aromatics. Gasoline floats on water; water cannot generally be used to extinguish a gasoline fire, unless used in a fine mist.
Gasoline is produced in oil refineries. Material separated from crude oil via distillation, called virgin or straight-run gasoline, does not meet specifications for modern engines (particularly the octane rating, see below), but comprises part of the blend.
The bulk of a typical gasoline consists of hydrocarbons with between four and 12 carbon atoms per molecule (commonly referred to as C4-C12).
The various refinery streams blended to make gasoline have different characteristics. Some important streams are:
The terms above are the jargon used in the oil industry, but terminology varies.
Overall, a typical gasoline is predominantly a mixture of paraffins (alkanes), naphthenes (cycloalkanes), and olefins (alkenes). The actual ratio depends on:
Currently, many countries set limits on gasoline aromatics in general, benzene in particular, and olefin (alkene) content. Such regulations led to increasing preference for high octane pure paraffin (alkane) components, such as alkylate, and is forcing refineries to add processing units to reduce benzene content.
Gasoline can also contain other organic compounds, such as organic ethers (deliberately added), plus small levels of contaminants, in particular organosulfur compounds, but these are usually removed at the refinery.
Most countries have phased out leaded fuel. Different additives have replaced the lead compounds. The most popular additives include aromatic hydrocarbons, ethers and alcohol (usually ethanol or methanol).
Gasoline, when used in high-compression internal combustion engines, tends to autoignite (detonate
) causing damaging "engine knocking" (also called "pinging" or "pinking") noise. To address this problem, tetraethyllead (TEL) was widely adopted as an additive for gasoline in the 1920s. With the discovery of the extent of environmental and health damage caused by the lead, however, and the incompatibility of lead with catalytic converters, leaded gasoline was phased out beginning in 1973. By 1995, leaded fuel accounted for only 0.6% of total gasoline sales and less than 2000 short tons (1814 t) of lead per year. From 1 January 1996, the U.S. Clean Air Act banned the sale of leaded fuel for use in on-road vehicles. The use of TEL also necessitated other additives, such as dibromoethane.
Methylcyclopentadienyl manganese tricarbonyl (MMT) is used in Canada and in Australia to boost octane. It also helps old cars designed for leaded fuel run on unleaded fuel without need for additives to prevent valve problems. Its use in the US has been restricted by regulations.
Gummy, sticky resin deposits result from oxidative degradation of gasoline upon long term storage. These harmful deposits arise from the oxidation of alkenes and other minor components in gasoline (see drying oils). Improvements in refinery techniques have generally reduced the susceptibility of gasolines to these problems. Previously, catalytically or thermally cracked gasolines are most susceptible to oxidation. The formation of these gums is accelerated by copper salts, which can be neutralized by additives call metal deactivators.
This degradation can be prevented through the addition of 5-100 ppm of antioxidants, such as phenylenediamines and other amines. Hydrocarbons with a bromine number of 10 or above can be protected with the combination of unhindered or partially hindered phenols and oil soluble strong amine bases, such as hindered phenols. "Stale" gasoline can be detected by a colorimetric enzymatic test for organic peroxides produced by oxidation of the gasoline.
gasolines are also treated with metal deactivators, which are compounds that sequester (deactivate) metal salts that otherwise accelerate the formation of gummy residues. The metal impurities might arise from the engine itself or as contaminants in the fuel.
Gasoline, as delivered at the pump, also contains additives to reduce internal engine carbon buildups, improve combustion, and to allow easier starting in cold climates. High levels of detergent can be found in Top Tier Detergent Gasolines. These gasolines exceed the U.S. EPA's minimum requirement for detergent content.]
[ The specification for Top Tier Detergent gasolines was developed by four automakers: GM, Honda, Toyota and BMW. According to the bulletin, the minimal EPA requirement is not sufficient to keep engines clean. Typical detergents include alkylamines and alkyl phosphates at the level of 50-100 ppm.
In the EU, 5% ethanol can be added within the common gasoline spec (EN 228). Discussions are ongoing to allow 10% blending of ethanol (available in Finnish, French and German gas stations). In Finland most gasoline stations sell 95E10, which is 10% of ethanol; and 98E5, which is 5% ethanol. Most gasoline sold in Sweden has 5-15% ethanol added.
In Brazil, the Brazilian National Agency of petroleum, Natural Gas and Biofuels (ANP) requires gasoline for automobile use to have from 18 to 25% of ethanol added to its composition.
Legislation requires retailers to label fuels containing ethanol on the dispenser, and limits ethanol use to 10% of petrol in Australia. Such petrol is commonly called E10 by major brands, and it is cheaper than regular unleaded petrol.
The federal Renewable Fuel Standard (RFS) effectively requires refiners and blenders to blend renewable biofuels (mostly ethanol) with gasoline, sufficient to meet a growing annual target of total gallons blended. Although the mandate does not require a specific percentage of ethanol, annual increases in the target combined with declining gasoline consumption has caused the typical ethanol content in gasoline to approach 10%. Most fuel pumps display a sticker that states that the fuel may contain up to 10% ethanol, an intentional disparity that reflects the varying actual percentage. Until late 2010, fuels retailers were only authorized to sell fuel containing up to 10 percent ethanol (E10), and most vehicle warranties (except for flexible fuel vehicles) authorize fuels that contain no more than 10 percent ethanol. In parts of the United States, ethanol is sometimes added to gasoline without an indication that it is a component.
The Government of India in October 2007 decided to make 5% ethanol blending (with gasoline) mandatory. Discussions are ongoing to increase the blending of ethanol to 10%.
In Australia, petrol tends to be dyed a light shade of purple.]
In South Africa, unleaded fuel is dyed green and lead-replacement fuel is dyed red.]
In the United States, aviation gasoline (avgas) is dyed to identify its octane rating and to distinguish it from kerosene-based jet fuel, which is clear.
In Canada and the United Kingdom gasoline for marine and farm use is dyed red and is not subject to road tax.
Oxygenate blending adds oxygen-bearing compounds such as MTBE, ETBE and ethanol. The presence of these oxygenates reduces the amount of carbon monoxide and unburned fuel in the exhaust gas. In many areas throughout the US, oxygenate blending is mandated by EPA regulations to reduce smog and other airborne pollutants. For example, in Southern California, fuel must contain 2% oxygen by weight, resulting in a mixture of 5.6% ethanol in gasoline. The resulting fuel is often known as reformulated gasoline (RFG) or oxygenated gasoline, or in the case of California, California reformulated gasoline. The federal requirement that RFG contain oxygen was dropped on 6 May 2006 because the industry had developed VOC-controlled RFG that did not need additional oxygen.
MTBE use is being phased out in some states due to issues with contamination of ground water. In some places, such as California, it is already banned. Ethanol and, to a lesser extent, the ethanol-derived ETBE are common replacements. Since most ethanol is derived from biomass, such as corn, sugar cane or grain, it is referred to as bioethanol. A common ethanol-gasoline mix of 10% ethanol mixed with gasoline is called gasohol or E10, and an ethanol-gasoline mix of 85% ethanol mixed with gasoline is called E85. The most extensive use of ethanol takes place in Brazil, where the ethanol is derived from sugarcane. In 2004, over 3.4 billion US gallons (2.8 billion imp gal/13 million m³) of ethanol was produced in the United States for fuel use, mostly from corn, and E85 is slowly becoming available in much of the United States, though many of the relatively few stations vending E85 are not open to the general public. The use of bioethanol, either directly or indirectly by conversion of such ethanol to bio-ETBE, is encouraged by the European Union Directive on the Promotion of the use of biofuels and other renewable fuels for transport. Since producing bioethanol from fermented sugars and starches involves distillation, though, ordinary people in much of Europe cannot legally ferment and distill their own bioethanol at present (unlike in the US, where getting a BATF distillation permit has been easy since the 1973 oil crisis).
Combustion of 1 US gallon (3.8 L) of gasoline produces 8,788 grams (19.37 lb) of carbon dioxide (2.3 kg/l), a greenhouse gas.
The main concern with gasoline on the environment, aside from the complications of its extraction and refining, is the potential effect on the climate. Unburnt gasoline and evaporation from the tank, when in the atmosphere, react in sunlight to produce photochemical smog. Addition of ethanol increases the volatility of gasoline, potentially worsening the problem.
The chief risks of such leaks come not from vehicles, but from gasoline delivery truck accidents and leaks from storage tanks. Because of this risk, most (underground) storage tanks now have extensive measures in place to detect and prevent any such leaks, such as monitoring systems (Veeder-Root, Franklin Fueling).
The material safety data sheet for unleaded gasoline shows at least 15 hazardous chemicals occurring in various amounts, including benzene (up to 5% by volume), toluene (up to 35% by volume), naphthalene (up to 1% by volume), trimethylbenzene (up to 7% by volume), -butyl ethertert
methyl (MTBE) (up to 18% by volume, in some states) and about ten others. Hydrocarbons in gasoline generally exhibit low acute toxicities, with LD50 of 700 – 2700 mg/kg for simple aromatic compounds. Benzene and many antiknocking additives are carcinogenic.
Huffed gasoline is a common intoxicant that has become epidemic in some poorer communities and indigenous groups in Australia, Canada, New Zealand,and some Pacific Islands. In response, Opal fuel has been developed by the BP Kwinana Refinery in Australia, and contains only 5% aromatics (unlike the usual 25%), which weakens the effects of inhalation.
Like other alkanes, gasoline burns in a limited range of its vapor phase and, coupled with its volatility, this makes leaks highly dangerous when sources of ignition are present. gasoline has a lower explosion limit of 1.4% by volume and an upper explosion limit of 7.6%. If the concentration is below 1.4%, the air-gasoline mixture is too lean and does not ignite. If the concentration is above 7.6%, the mixture is too rich and also does not ignite. However, gasoline vapor rapidly mixes and spreads with air, making unconstrained gasoline quickly flammable. Many accidents involve people using gasoline to start bonfires going. The gasoline readily vaporizes and mixes with surrounding air.]
The United States account for about 44% of the world’s gasoline consumption. In 2003 The US consumed 476.474 gigalitres (1.258711011 US gal; 1.048101011 imp gal), which equates to 1.3 gigaliters of gasoline each day (about 360 million US or 300 million imperial gallons). The US used about 510 billion liters (138 billion US gal/115 billion imp gal) of gasoline in 2006, of which 5.6% was mid-grade and 9.5% was premium grade.
Western countries have the highest usage rates per person.]
Unlike the US, countries in Europe impose substantial taxes on fuels such as gasoline. The price of gasoline in Europe is typically more than twice that in the US. In Italy, due to the amendments imposed by Monti's Government in December 2011, the price of gasoline has passed, in the period of two weeks, from 1.50 €/l (7.48 US$/gal) to 1.75 €/l (8.72 US$/gal); on March, 17th, in a gasoline Station located near Ancona, has reached the psychological threshold of 2 €/l: the price was € 2.001/l (this means 9.97 US$/gal) This chart must be compared to the USA national average price of gasoline of 0.71 €/l .
From 1998 to 2004, the price of gasoline fluctuated between $1 and $2 USD per U.S. gallon. After 2004, the price increased until the average gas price reached a high of $4.11 per U.S. gallon in mid-2008, but receded to approximately $2.60 per U.S. gallon by September 2009. More recently, the U.S. experienced an upswing in gas prices through 2011, and by 1 March 2012, the national average was $3.74 per gal.
In the United States, most consumer goods bear pre-tax prices, but gasoline prices are posted with taxes included. Taxes are added by federal, state, and local governments. As of 2009, the federal tax is 18.4¢ per gallon for gasoline and 24.4¢ per gallon for diesel (excluding red diesel). Among states, the highest gasoline tax rates, including the federal taxes as of 2005, are New York (62.9¢/gal), Hawaii (60.1¢/gal), and California (60¢/gal). However, many states' taxes are a percentage and thus vary in amount depending on the cost of the gasoline.
About 9% of all gasoline sold in the US in May 2009 was premium grade, according to the Energy Information Administration. Consumer Reports
magazine says, “If [your owner’s manual] says to use regular fuel, do so—there’s no advantage to a higher grade.” The Associated Press said premium gas—which is a higher octane and costs several cents a gallon more than regular unleaded—should be used only if the manufacturer says it is “required”. Cars with turbocharged engines and high compression ratios often specify premium gas because higher octane fuels reduce the incidence of "knock", or fuel pre-detonation. If regular fuel is used, the engine computer usually switches to a less aggressive fuel map to protect the engine, and performance is decreased.
The first automotive combustion engines, so-called Otto engines, were developed in the last quarter of the 19th century in Germany. The fuel was a relatively volatile hydrocarbon obtained from coal gas. With a boiling point near 85 °C (octanes boil about 40 °C higher), it was well suited for early carburetors (evaporators). The development of a "spray nozzle" carburetor enabled the use of less volatile fuels. Further improvements in engine efficiency were attempted at higher compression ratios, but early attempts were blocked by knocking (premature explosion of fuel). In the 1920s, antiknock compounds were introduced by Migley and Boyd, specifically tetraethyllead (TEL). This innovation started a cycle of improvements in fuel efficiency that coincided with the large-scale development of oil refining to provide more products in the boiling range of gasolines. In the 1950s oil refineries started to focus on high octane fuels, and then detergents were added to gasoline to clean the jets and carburetors. The 1970s witnessed greater attention to the environmental consequences of burning gasoline. These considerations led to the phasing out of TEL and its replacement by other antiknock compounds. Subsequently, low-sulfur gasoline was introduced, in part to preserve the catalysts in modern exhaust systems.
"Gasoline" is cited (under the spelling "gasolene") from 1863 in the Oxford English Dictionary
. It was never a trademark, although it may have been derived from older trademarks such as "Cazeline" and "Gazeline".
Variant spellings of "gasoline" have been used to refer to raw petroleum since the 16th century. "Petrol" was first used as the name of a refined petroleum product around 1870 by British wholesaler Carless, Capel & Leonard, who marketed it as a solvent. When the product later found a new use as a motor fuel, Frederick Simms, an associate of Gottlieb Daimler, suggested to Carless that they register the trade mark "petrol", but by this time the word was already in general use, possibly inspired by the French pétrole
, and the registration was not allowed. Carless registered a number of alternative names for the product, while their competitors used the term "motor spirit" until the 1930s.
In many countries, gasoline has a colloquial name derived from that of the chemical benzene (e.g.
, German Benzin
, Dutch benzine
, Italian benzina
, Chile bencina
, Thai ??????
, Greek ße?????
). Argentina, Uruguay and Paraguay use the colloquial name nafta
derived from that of the chemical naphtha.
The terms "mogas", short for motor gasoline, or "autogas", short for automobile gasoline, are used to distinguish automobile fuel from aviation fuel, or "avgas". In British English, gasoline
can refer to a different petroleum derivative historically used in lamps, but this usage is relatively uncommon.]
Volumetric and mass energy density of some fuels compared with gasoline (in the rows with gross and net, they are from):
(*) Diesel fuel is not used in a gasoline engine, so its low octane rating is not an issue; the relevant metric for diesel engines is the cetane number
Natural gas is a naturally occurring hydrocarbon gas mixture consisting primarily of methane, but commonly includes varying amounts of other higher alkanes and even a lesser percentage of carbon dioxide, nitrogen, and hydrogen sulfide. Natural gas is an energy source often used for heating, cooking, and electricity generation. It is also used as fuel for vehicles and as a chemical feedstock in the manufacture of plastics and other commercially important organic chemicals.
Natural gas is found in deep underground natural rock formations or associated with other hydrocarbon reservoirs in coal beds and as methane clathrates. Petroleum is also another resource found in proximity to and with natural gas. Most natural gas was created over time by two mechanisms: biogenic and thermogenic. Biogenic gas is created by methanogenic organisms in marshes, bogs, landfills, and shallow sediments. Deeper in the earth, at greater temperature and pressure, thermogenic gas is created from buried organic material.
Before natural gas can be used as a fuel, it must undergo processing to remove impurities, including water, to meet the specifications of marketable natural gas. The by-products of processing include ethane, propane, butanes, pentanes, and higher molecular weight hydrocarbons, hydrogen sulfide (which may be converted into pure sulfur), carbon dioxide, water vapor, and sometimes helium and nitrogen.
Natural gas is often informally referred to simply as gas, especially when compared to other energy sources such as oil or coal. But not to be confused with gasoline especially in North America, the term gasoline also is often shortened in colloquial usage to gas.
In the 19th century, natural gas was usually obtained as a by-product of producing oil, since the small, light gas carbon chains came out of solution as the extracted fluids underwent pressure reduction from the reservoir to the surface, similar to uncapping a bottle of soda where the carbon dioxide effervesces. Unwanted natural gas was a disposal problem in the active oil fields. If there was not a market for natural gas near the wellhead it was virtually valueless since it had to be piped to the end user.
In the 19th century and early 20th century, such unwanted gas was usually burned off at oil fields. Today, unwanted gas (or stranded gas without a market) associated with oil extraction often is returned to the reservoir with 'injection' wells while awaiting a possible future market or to repressurize the formation, which can enhance extraction rates from other wells. In regions with a high natural gas demand (such as the US), pipelines are constructed when it is economically feasible to transport gas from a wellsite to an end consumer.
Another possibility is to export natural gas as a liquid. Gas-to-liquids (GTL) is a developing technology that converts stranded natural gas into synthetic gasoline, diesel, or jet fuel through the Fischer-Tropsch process developed in Germany prior to World War II. Such fuel can be transported to users through conventional pipelines and tankers. Proponents claim that GTL burns cleaner than comparable petroleum fuels. Major international oil companies use sophisticated technology to produce GTL. A world-scale (140,000 barrels (22,000 m3) a day) GTL plant in Qatar went into production in 2011.
Natural gas can be "associated" (found in oil fields), or "non-associated" (isolated in natural gas fields), and is also found in coal beds (as coalbed methane). It sometimes contains a significant amount of ethane, propane, butane, and pentane—heavier hydrocarbons removed for commercial use prior to the methane being sold as a consumer fuel or chemical plant feedstock. Non-hydrocarbons such as carbon dioxide, nitrogen, helium (rarely), and hydrogen sulfide must also be removed before the natural gas can be transported.
Natural gas extracted from oil wells is called casinghead gas or associated gas. The natural gas industry is extracting an increasing quantity of gas from challenging resource types: sour gas, tight gas, shale gas, and coalbed methane.
Iran has the world's largest reserves of natural gas (17.9% of the world's total). It contains an estimated 1,187.3 trillion cubic feet (33,620 km3) (Tcf) in proven natural gas reserves. With Gazprom, Russia is frequently the world's largest natural gas extractor. Major proven resources (in billion cubic meters) are world 187,300 (2013), Iran 33,600 (2013), Russia 32,900 (2013), Qatar 25,100 (2013), Turkmenistan 17,500 (2013) and the United States 8,500 (2013).
It is estimated that there are about 900 trillion cubic meters of "unconventional" gas such as shale gas, of which 180 trillion may be recoverable. In turn, many studies from MIT, Black & Veatch and the DOE—see natural gas—will account for a larger portion of electricity generation and heat in the future.
The world's largest gas field is Qatar's offshore North Field, estimated to have 25 trillion cubic meters (9.01014cubic feet) of gas in place—enough to last more than 420 years][ at optimum extraction levels. The second largest natural gas field is the South Pars Gas Field in Iranian waters in the Persian Gulf. Located next to Qatar's North Field, it has an estimated reserve of 8 to 14 trillion cubic meters of gas.
Because natural gas is not a pure product, as the reservoir pressure drops when non-associated gas is extracted from a field under supercritical (pressure/temperature) conditions, the higher molecular weight components may partially condense upon isothermic depressurizing—an effect called retrograde condensation. The liquid thus formed may get trapped as the pores of the gas reservoir get deposited. One method to deal with this problem is to re-inject dried gas free of condensate to maintain the underground pressure and to allow re-evaporation and extraction of condensates. More frequently, the liquid condenses at the surface, and one of the tasks of the gas plant is to collect this condensate. The resulting liquid is called natural gas liquid (NGL) and has commercial value.
Shale gas in the United States is rapidly increasing as a source of natural gas. Led by new applications of hydraulic fracturing technology and horizontal drilling, development of new sources of shale gas has offset declines in production from conventional gas reservoirs, and has led to major increases in reserves of US natural gas. Largely due to shale gas discoveries, estimated reserves of natural gas in the United States in 2008 were 35% higher than in 2006. Following the success in the United States, gas operations are beginning to sprout up in other countries around the world, particularly Poland, China, and South Africa.
Shale gas was first extracted as a resource in Fredonia, NY in 1825, in shallow, low-pressure fractures. Work on industrial-scale shale gas production did not begin until the 1970s, when declining production potential from conventional gas deposits in the United States spurred the federal government to invest in R&D and demonstration projects Up until the public and private R&D and demonstration projects of the 1970s and 1980s, drilling in shale was not considered to be commercially viable.
Early American federal government investments in shale gas began with the Eastern Gas Shales Project in 1976 and the annual FERC-approved research budget of the Gas Research Institute. The Department of Energy later partnered with private gas companies to complete the first successful air-drilled multi-fracture horizontal well in shale in 1986. The federal government further incentivized drilling in shale via the Section 29 tax credit for unconventional gas from 1980-2000. Microseismic imaging, a crucial input to both hydraulic fracturing in shale and offshore oil drilling, originated from seismic research at Sandia National Laboratories. In 1991 the Department of Energy subsidized Texas gas company Mitchell Energy's first horizontal drill in the Barnett Shale in north Texas.
Mitchell Energy utilized all these component technologies and techniques to achieve the first economical shale fracture in 1998 using an innovative process called slick-water fracturing. Since then, natural gas from shale has been the fastest growing contributor to total primary energy (TPE) in the United States, and has led many other countries to pursue shale deposits. According to the IEA, the economical extraction of shale gas more than doubles the projected production potential of natural gas, from 125 years to over 250 years.
Town gas is a flammable gaseous fuel made by the destructive distillation of coal and contains a variety of calorific gases including hydrogen, carbon monoxide, methane, and other volatile hydrocarbons, together with small quantities of non-calorific gases such as carbon dioxide and nitrogen, and is used in a similar way to natural gas. This is a historical technology, not usually economically competitive with other sources of fuel gas today. But there are still some specific cases where it is the best option and it may be so into the future.
Most town "gashouses" located in the eastern US in the late 19th and early 20th centuries were simple by-product coke ovens that heated bituminous coal in air-tight chambers. The gas driven off from the coal was collected and distributed through networks of pipes to residences and other buildings where it was used for cooking and lighting. (Gas heating did not come into widespread use until the last half of the 20th century.) The coal tar (or asphalt) that collected in the bottoms of the gashouse ovens was often used for roofing and other water-proofing purposes, and when mixed with sand and gravel was used for paving streets.
Methanogenic archaea are responsible for all biological sources of methane. Some live in symbiotic relationships with other life forms, including termites, ruminants, and cultivated crops. Other sources of methane, the principal component of natural gas, include landfill gas, biogas, and methane hydrate. When methane-rich gases are produced by the anaerobic decay of non-fossil organic matter (biomass), these are referred to as biogas (or natural biogas). Sources of biogas include swamps, marshes, and landfills (see landfill gas), as well as agricultural waste materials such as sewage sludge and manure by way of anaerobic digesters, in addition to enteric fermentation, particularly in cattle. Landfill gas is created by decomposition of waste in landfill sites. Excluding water vapor, about half of landfill gas is methane and most of the rest is carbon dioxide, with small amounts of nitrogen, oxygen, and hydrogen, and variable trace amounts of hydrogen sulfide and siloxanes. If the gas is not removed, the pressure may get so high that it works its way to the surface, causing damage to the landfill structure, unpleasant odor, vegetation die-off, and an explosion hazard. The gas can be vented to the atmosphere, flared or burned to produce electricity or heat. Biogas can also be produced by separating organic materials from waste that otherwise goes to landfills. This method is more efficient than just capturing the landfill gas it produces. Anaerobic lagoons produce biogas from manure, while biogas reactors can be used for manure or plant parts. Like landfill gas, biogas is mostly methane and carbon dioxide, with small amounts of nitrogen, oxygen and hydrogen. However, with the exception of pesticides, there are usually lower levels of contaminants.
Landfill gas cannot be distributed through utility natural gas pipelines unless it is cleaned up to less than 3 per cent CO2, and a few parts per million , because CO2 and corrode the pipelines. The presence of CO2 will lower the energy level of the gas below requirements for the pipeline][. Siloxanes in the gas will form deposits in gas burners and need to be removed prior to entry into any gas distribution or transmission system. Consequently it may be more economical to burn the gas on site or within a short distance of the landfill using a dedicated pipeline. Water vapor is often removed, even if the gas is burned on site. If low temperatures condense water out of the gas, siloxanes can be lowered as well because they tend to condense out with the water vapor. Other non-methane components may also be removed to meet emission standards, to prevent fouling of the equipment or for environmental considerations. Co-firing landfill gas with natural gas improves combustion, which lowers emissions.
Biogas, and especially landfill gas, are already used in some areas, but their use could be greatly expanded. Experimental systems were being proposed][ for use in parts of Hertfordshire, UK, and Lyon in France.][ Using materials that would otherwise generate no income, or even cost money to get rid of, improves the profitability and energy balance of biogas production. Gas generated in sewage treatment plants is commonly used to generate electricity. For example, the Hyperion sewage plant in Los Angeles burns 8 million cubic feet (230,000 m3) of gas per day to generate power New York City utilizes gas to run equipment in the sewage plants, to generate electricity, and in boilers. Using sewage gas to make electricity is not limited to large cities. The city of Bakersfield, California, uses cogeneration at its sewer plants. California has 242 sewage wastewater treatment plants, 74 of which have installed anaerobic digesters. The total biopower generation from the 74 plants is about 66 MW.
Huge quantities of natural gas (primarily methane) exist in the form of hydrates under sediment on offshore continental shelves and on land in arctic regions that experience permafrost, such as those in Siberia. Hydrates require a combination of high pressure and low temperature to form. However, as of 2010[update] no technology has been developed yet to extract natural gas economically from hydrates.
In 2010, using current technology, the cost of extracting natural gas from crystallized natural gas is estimated to 100–200 per cent the cost of extracting natural gas from conventional sources, and even higher from offshore deposits.
The image below is a schematic block flow diagram of a typical natural gas processing plant. It shows the various unit processes used to convert raw natural gas into sales gas pipelined to the end user markets.
The block flow diagram also shows how processing of the raw natural gas yields byproduct sulfur, byproduct ethane, and natural gas liquids (NGL) propane, butanes and natural gasoline (denoted as pentanes +).
See main article, Gas depletion
Natural gas is a major source of electricity generation through the use of cogeneration, gas turbines and steam turbines. Natural gas is also well suited for a combined use in association with renewable energy sources such as wind or solar and for alimenting peak-load power stations functioning in tandem with hydroelectric plants. Most grid peaking power plants and some off-grid engine-generators use natural gas. Particularly high efficiencies can be achieved through combining gas turbines with a steam turbine in combined cycle mode. Natural gas burns more cleanly than other hydrocarbon fuels, such as oil and coal, and produces less carbon dioxide per unit of energy released. For an equivalent amount of heat, burning natural gas produces about 30 per cent less carbon dioxide than burning petroleum and about 45 per cent less than burning coal.
Coal-fired electric power generation emits around 2,000 pounds of carbon dioxide for every megawatt hour generated, which is almost double the carbon dioxide released by a natural gas-fired electric plant per megawatt hour generated. Because of this higher carbon efficiency of natural gas generation, as the fuel mix in the United States has changed to reduce coal and increase natural gas generation, carbon dioxide emissions have unexpectedly fallen. Those measured in the first quarter of 2012 were the lowest of any recorded for the first quarter of any year since 1992.
Combined cycle power generation using natural gas is currently the cleanest available source of power using hydrocarbon fuels, and this technology is widely and increasingly used as natural gas can be obtained at increasingly reasonable costs. Fuel cell technology may eventually provide cleaner options for converting natural gas into electricity, but as yet it is not price-competitive. Locally produced electricity and heat using natural gas powered Combined Heat and Power plant (CHP or Cogeneration plant) is considered energy efficient and a rapid way to cut carbon emissions.
Natural gas dispensed from a simple stovetop can generate heat in excess of 2000°F (1093°C) making it a powerful domestic cooking and heating fuel. In much of the developed world it is supplied to homes via pipes where it is used for many purposes including natural gas-powered ranges and ovens, natural gas-heated clothes dryers, heating/cooling, and central heating. Home or other building heating may include boilers, furnaces, and water heaters.
Compressed natural gas (CNG) is used in rural homes without connections to piped-in public utility services, or with portable grills.][ Natural gas is also supplied by independent natural gas suppliers through Natural Gas Choice programs throughout the United States. However, due to CNG being less economical than LPG, LPG (propane) is the dominant source of rural gas.
CNG is a cleaner alternative to other automobile fuels such as gasoline (petrol) and diesel. By the end of 2012 there were 17.25 million natural gas vehicles worldwide, led by Iran (3.3 million), Pakistan (3.1 million), Argentina (2.18 million), Brazil (1.73 million), India (1.5 million), and China (1.5 million). The energy efficiency is generally equal to that of gasoline engines, but lower compared with modern diesel engines. Gasoline/petrol vehicles converted to run on natural gas suffer because of the low compression ratio of their engines, resulting in a cropping of delivered power while running on natural gas (10%–15%). CNG-specific engines, however, use a higher compression ratio due to this fuel's higher octane number of 120–130.
Natural gas is a major feedstock for the production of ammonia, via the Haber process, for use in fertilizer production.
Russian aircraft manufacturer Tupolev is currently running a development program to produce LNG- and hydrogen-powered aircraft. The program has been running since the mid-1970s, and seeks to develop LNG and hydrogen variants of the Tu-204 and Tu-334 passenger aircraft, and also the Tu-330 cargo aircraft. It claims that at current market prices, an LNG-powered aircraft would cost 5,000 roubles (~ $218/ £112) less to operate per ton, roughly equivalent to 60 per cent, with considerable reductions to carbon monoxide, hydrocarbon and nitrogen oxide emissions.
The advantages of liquid methane as a jet engine fuel are that it has more specific energy than the standard kerosene mixes do and that its low temperature can help cool the air which the engine compresses for greater volumetric efficiency, in effect replacing an intercooler. Alternatively, it can be used to lower the temperature of the exhaust.
Natural gas can be used to produce hydrogen, with one common method being the hydrogen reformer. Hydrogen has many applications: it is a primary feedstock for the chemical industry, a hydrogenating agent, an important commodity for oil refineries, and the fuel source in hydrogen vehicles.
Natural gas is also used in the manufacture of fabrics, glass, steel, plastics, paint, and other products.
Because of its low density, it is not easy to store natural gas or transport by vehicle. Natural gas pipelines are impractical across oceans. Many existing pipelines in America are close to reaching their capacity, prompting some politicians representing northern states to speak of potential shortages. In Europe, the gas pipeline network is already dense in the West. New pipelines are planned or under construction in Eastern Europe and between gas fields in Russia, Near East and Northern Africa and Western Europe. See also List of natural gas pipelines.
LNG carriers transport liquefied natural gas (LNG) across oceans, while tank trucks can carry liquefied or compressed natural gas (CNG) over shorter distances. Sea transport using CNG carrier ships that are now under development may be competitive with LNG transport in specific conditions.
Gas is turned into liquid at a liquefaction plant, and is returned to gas form at regasification plant at the terminal. Shipborne regasification equipment is also used. LNG is the preferred form for long distance, high volume transportation of natural gas, whereas pipeline is preferred for transport for distances up to 4,000 km (2,485 mi) over land and approximately half that distance offshore.
CNG is transported at high pressure, typically above 200 bars. Compressors and decompression equipment are less capital intensive and may be economical in smaller unit sizes than liquefaction/regasification plants. Natural gas trucks and carriers may transport natural gas directly to end-users, or to distribution points such as pipelines.
In the past, the natural gas which was recovered in the course of recovering petroleum could not be profitably sold, and was simply burned at the oil field in a process known as flaring. Flaring is now illegal in many countries. Additionally, higher demand in the last 20–30 years has made production of gas associated with oil economically viable. A further option is the gas is now sometimes re-injected into the formation for enhanced oil recovery by pressure maintenance as well as miscible or immiscible flooding. Conservation, re-injection, or flaring of natural gas associated with oil is primarily dependant on proximity to markets (pipelines), and regulatory restrictions.
A "master gas system" was invented in Saudi Arabia in the late 1970s, ending any necessity for flaring. Satellite observation, however, shows that flaring and venting are still practiced in some gas-extracting countries.
Natural gas is used to generate electricity and heat for desalination. Similarly, some landfills that also discharge methane gases have been set up to capture the methane and generate electricity.
Natural gas is often stored underground inside depleted gas reservoirs from previous gas wells, salt domes, or in tanks as liquefied natural gas. The gas is injected in a time of low demand and extracted when demand picks up. Storage nearby end users helps to meet volatile demands, but such storage may not always be practicable.
With 15 countries accounting for 84 per cent of the worldwide extraction, access to natural gas has become an important issue in international politics, and countries vie for control of pipelines. In the first decade of the 21st century, Gazprom, the state-owned energy company in Russia, engaged in disputes with Ukraine and Belarus over the price of natural gas, which have created concerns that gas deliveries to parts of Europe could be cut off for political reasons.
Floating Liquefied Natural Gas (FLNG) is an innovative technology designed to enable the development of offshore gas resources that would otherwise remain untapped because due to environmental or economic factors it is nonviable to develop them via a land-based LNG operation. FLNG technology also provides a number of environmental and economic advantages:
Many gas and oil companies are considering the economic and environmental benefits of Floating Liquefied Natural Gas (FLNG). However, for the time being, the only FLNG facility now in development is being built by Shell, due for completion around 2017.
Natural gas is mainly composed of methane. After release to the atmosphere it is removed over about 10 years by gradual oxidation to carbon dioxide and water by hydroxyl radicals (·OH) formed in the troposphere or stratosphere, giving the overall chemical reaction CH4 + 2O2→ CO2 + 2H2O. While the lifetime of atmospheric methane is relatively short when compared to carbon dioxide, it is more efficient at trapping heat in the atmosphere, so that a given quantity of methane has 62 times the global-warming potential of carbon dioxide over a 20-year period, 20 times over a 100-year period and 8 times over a 500-year period. Natural gas is thus a more potent greenhouse gas than carbon dioxide due to the greater global-warming potential of methane. Current estimates by the EPA place global emissions of methane at 3 trillion cubic feet (85 km3) annually, or 3.2 per cent of global production. Direct emissions of methane represented 14.3 per cent of all global anthropogenic greenhouse gas emissions in 2004.
The extraction, storage, transportation and distribution of natural gas is known to leak into the atmosphere, particularly during the extraction process. A study in 2011 demonstrated that the leak rate of methane was high enough to jeopardize its global warming advantage over coal. This study was criticized later for its high assumption of methane leakage values. These values were later shown to be close to the findings of the Scientists at the National Oceanic and Atmospheric Administration. Natural gas extraction also releases an isotope of Radon, ranging from 5 to 200,000 Becquerels per cubic meter.
Natural gas is often described as the cleanest fossil fuel. It produces about 29% and 44% less carbon dioxide per joule delivered than oil and coal respectively, and potentially fewer pollutants than other hydrocarbon fuels. However, in absolute terms, it comprises a substantial percentage of human carbon emissions, and this contribution is projected to grow. According to the IPCC Fourth Assessment Report, in 2004, natural gas produced about 5.3 billion tons a year of CO2 emissions, while coal and oil produced 10.6 and 10.2 billion tons respectively. According to an updated version of the Special Report on Emissions Scenario by 2030, natural gas would be the source of 11 billion tons a year, with coal and oil now 8.4 and 17.2 billion respectively because demand is increasing 1.9 percent a year. Total global emissions for 2004 were estimated at over 27,200 million tons.
Natural gas produces far lower amounts of sulfur dioxide and nitrous oxides than any other hydrocarbon fuels. The other pollutants due to natural gas combustion are listed below in parts per million (ppm):
In mines, where methane seeping from rock formations has no odor, sensors are used, and mining apparatus such as the Davy lamp has been specifically developed to avoid ignition sources.
Some gas fields yield sour gas containing hydrogen sulfide (H2S). This untreated gas is toxic. Amine gas treating, an industrial scale process which removes acidic gaseous components, is often used to remove hydrogen sulfide from natural gas.
Extraction of natural gas (or oil) leads to decrease in pressure in the reservoir. Such decrease in pressure in turn may result in subsidence, sinking of the ground above. Subsidence may affect ecosystems, waterways, sewer and water supply systems, foundations, and so on.
Another ecosystem effect results from the noise of the process. This can change the composition of animal life in the area, and have consequences for plants as well in that animals disperse seeds and pollen.][
Releasing the gas from low-permeability reservoirs is accomplished by a process called hydraulic fracturing or "hydrofracking". To allow the natural gas to flow out of the shale, oil operators force 1 to 9 million US gallons (34,000 m3) of water mixed with a variety of chemicals through the wellbore casing into the shale. The high pressure water breaks up or "fracks" the shale, which releases the trapped gas. Sand is added to the water as a proppant to keep the fractures in the shale open, thus enabling the gas to flow into the casing and then to the surface. The chemicals are added to the frack fluid to reduce friction and combat corrosion. During the extracting life of a gas well, other low concentrations of other chemical substances may be used, such as biocides to eliminate fouling, scale and corrosion inhibitors, oxygen scavengers to remove a source of corrosion, and acids to clean the perforations in the pipe.
Dealing with fracking fluid can be a challenge. Along with the gas, 30 per cent to 70 per cent of the chemically laced frack fluid, or flow back, returns to the surface. Additionally, a significant amount of brine, containing salt and other minerals, may be produced with the gas. It is however uncommon for this to cause a problem with the environment. The water concerns are mostly a placebo.
In order to assist in detecting leaks, a minute amount of odorant is added to the otherwise colorless and almost odorless gas used by consumers. The odor has been compared to the smell of rotten eggs, due to the added tert-Butylthiol (t-butyl mercaptan). Sometimes a related compound, thiophane may be used in the mixture. Situations in which an odorant that is added to natural gas can be detected by analytical instrumentation, but cannot be properly detected by an observer with a normal sense of smell, have occurred in the natural gas industry. This is caused by odor masking, when one odorant overpowers the sensation of another. As of 2011, the industry is conducting research on the causes of odor masking.
Explosions caused by natural gas leaks occur a few times each year. Individual homes, small businesses and other structures are most frequently affected when an internal leak builds up gas inside the structure. Frequently, the blast will be enough to significantly damage a building but leave it standing. In these cases, the people inside tend to have minor to moderate injuries. Occasionally, the gas can collect in high enough quantities to cause a deadly explosion, disintegrating one or more buildings in the process. The gas usually dissipates readily outdoors, but can sometimes collect in dangerous quantities if flow rates are high enough. However, considering the tens of millions of structures that use the fuel, the individual risk of using natural gas is very low.
Natural gas heating systems are a minor source of carbon monoxide deaths in the United States. According to the US Consumer Product Safety Commission (2008), 56 per cent of unintentional deaths from non-fire CO poisoning were associated with engine-driven tools like gas-powered generators and lawn mowers. Natural gas heating systems accounted for 4 per cent of these deaths. Improvements in natural gas furnace designs have greatly reduced CO poisoning concerns. Detectors are also available that warn of carbon monoxide and/or explosive gas (methane, propane, etc.).
Quantities of natural gas are measured in normal cubic meters (corresponding to 0 °C at 101.325 kPa) or in standard cubic feet (corresponding to and 14.73 psia). The gross heat of combustion of one cubic meter of commercial quality natural gas is around 39 megajoules (≈10.8 kWh), but this can vary by several percent. This comes to about 49 megajoules (≈13.5 kWh) for one kg of natural gas (assuming 0.8 kg/m^3, an approximate value).][
The price of natural gas varies greatly depending on location and type of consumer. In 2007, a price of $7 per 1,000 cubic feet (28 m3) was typical in the United States. The typical caloric value of natural gas is roughly 1,000 British thermal units (BTU) per cubic foot, depending on gas composition. This corresponds to around $7 per million BTU, or around $7 per gigajoule. In April 2008, the wholesale price was $10 per 1,000 cubic feet (28 m3) ($10/MMBTU). The residential price varies from 50 per cent to 300 per cent more than the wholesale price. At the end of 2007, this was $12–$16 per 1,000 cu ft (28 m3). Natural gas in the United States is traded as a futures contract on the New York Mercantile Exchange. Each contract is for 10,000 MMBTU (~10,550 gigajoules), or 10 billion BTU. Thus, if the price of gas is $10 per million BTUs on the NYMEX, the contract is worth $100,000.
Gas prices for end users vary greatly across the EU. A single European energy market, one of the key objectives of the European Union, should level the prices of gas in all EU member states. Moreover, it would help to resolve supplying and global warming issues.
In US units, one standard cubic foot 1 cubic foot (28 L) of natural gas produces around 1,028 British thermal units (1,085 kJ). The actual heating value when the water formed does not condense is the net heat of combustion and can be as much as 10 percent less.
In the United States, retail sales are often in units of therms (th); 1 therm = 100,000 BTU. Gas meters measure the volume of gas used, and this is converted to therms by multiplying the volume by the energy content of the gas used during that period, which varies slightly over time. Wholesale transactions are generally done in decatherms (Dth), or in thousand decatherms (MDth), or in million decatherms (MMDth). A million decatherms is roughly a billion cubic feet of natural gas. Gas sales to domestic consumers may be in units of 100 standard cubic feet (Ccf).
Canada uses metric measure for internal trade of petrochemical products. Consequently, natural gas is sold by the Gigajoule, cubic metre (m3) or thousand cubic metres (E3m3). Distribution infrastructure and meters almost always meter volume (cubic foot or cubic meter). Some jurisdictions, such as Saskatchewan, sell gas by volume only. Other jurisdictions, such as Alberta, gas is sold by the energy content (GJ). In these areas, almost all meters for residential and small commercial customers measure volume (m3 or ft3), and billing statements include a multiplier to convert the volume to energy energy content of the local gas supply.
A Gigajoule (GJ) is a measure approximately equal to 1/2 of a barrel (250 lbs) of oil, or 1 million BTUs, or 1000 cu ft of gas, or 28cu metres (m3) of gas. The energy content of gas supply in Canada can vary from 37 to 43 GJ per m3 depending on gas supply and processing between the wellhead and the customer.
In the rest of the world, natural gas is sold in Gigajoule retail units. LNG (liquefied natural gas) and LPG (liquefied petroleum gas) are traded in metric tons or mmBTU as spot deliveries. Long term natural gas distribution contracts are signed in cubic metres, and LNG contracts are in metric tonnes (1,000 kg). The LNG and LPG is transported by specialized transport ships, as the gas is liquified at cryogenic temperatures. The specification of each LNG/LPG cargo will usually contain the energy content, but this information is in general not available to the public.
In the Russian Federation, Gazprom sold approximately 250 billion cubic metres of natural gas in 2008.
Research conducted by the World Pensions Council (WPC) suggests that large US and Canadian pension funds and Asian and MENA area SWF investors have become particularly active in the fields of natural gas and natural gas infrastructure, a trend started in 2005 by the formation of Scotia Gas Networks in the UK by OMERS and Ontario Teachers' Pension Plan.
Another way to storage natural gas is adsorbing it to the porous solids called sorbents. The best condition for methane storage is at room temperature and atmospheric pressure. The used pressure can be up to 4 MPa for having more storage capacity. The most common sorbent used for ANG is activated carbon (AC). Three main types of activated carbons for ANG are: Activated Carbon Fiber (ACF), Powdered Activated Carbon (PAC), activated carbon monolith.
Natural gasoline is a natural gas liquid with a vapor pressure intermediate between natural gas condensate(drip gas) and liquefied petroleum gas and has a boiling point within the range of gasoline. The typical gravity of natural gasoline is around 80 API.
This hydrocarbon mixture is liquid at ambient pressure and temperature. It is volatile and unstable but can be blended with other hydrocarbons to produce commercial gasoline.
The natural gas hydrocarbons mixture is mostly pentanes and heavier (smaller amounts of C6 and C6+), extracted from natural gas, that meets vapor pressure, end-point, and other specifications for natural gasoline set by the Gas Processors Association. Includes isopentane which is a saturated branch-chain hydrocarbon, (C5H12), obtained by fractionation of natural gasoline or isomerization of normal pentane.
Natural gasoline is often used to denature ethanol produced for E85 "flexible fuel". Natural gasoline has a lower octane content than conventional commercial distilled gasoline, so it cannot normally be used by itself for fuel for modern automobiles. However, when mixed with high concentrations of ethanol such as mid-level blends, like E50 or E85, the octane content is raised high enough to be used easily in flex-fuel vehicles. It may be sourced from production of natural gas wells (See "drip gas") or may be produced by extraction processes in the field, as opposed to refinery cracking of conventional gasoline.
A fuel tank (or petrol tank) is a safe container for flammable fluids. Though any storage tank for fuel may be so called, the term is typically applied to part of an engine system in which the fuel is stored and propelled (fuel pump) or released (pressurized gas) into an engine. Fuel tanks range in size and complexity from the small plastic tank of a butane lighter to the multi-chambered cryogenic Space Shuttle external tank.
Typically, a fuel tank must allow or provide the following: Alkanes
Detonation involves a supersonic exothermic front accelerating through a medium that eventually drives a shock front propagating directly in front of it. Detonations are observed in both conventional solid and liquid explosives, as well as in reactive gases. The velocity of detonations in solid and liquid explosives is much higher than that in gaseous ones, which allows the wave system to be observed with greater detail (higher resolution).
Gaseous detonations normally occur in confined systems but are occasionally observed in large vapor clouds. They are often associated with a gaseous mixture of fuel and oxidant of a composition, somewhat below conventional flammability limits. There is an extraordinary variety of fuels that may be present as gases, as droplet fogs and as dust suspensions. Other materials, such as acetylene, ozone and hydrogen peroxide are detonable in the absence of oxygen; a more complete list is given by both Stull and Bretherick. Oxidants include halogens, ozone, hydrogen peroxide and oxides of nitrogen. Mothball