V.A.
Raju & Dr. A.N. Giri
The
preservation of our environment is a very important and pressing topic,
particularly when dealing with energy issues. The advancement of technology,
particularly technologies that allow the cleaner use of fossil fuels, may
provide many environmental benefits and allow us to use cleaner energy. Natural gas is the cleanest of the fossil fuels, and thus
its many applications can serve to decrease harmful pollution levels from all
sectors, particularly when used together with or replacing other fossil fuels.
The natural gas industry itself is also committed to ensuring that the process
of producing natural gas is as environmentally-friendly as possible.
This
section focuses on sulfur compounds in natural gas, Origin and history of NG, Description and Technical
Characteristics, Quality & the environmental issues related to the use of
natural gas, as well as the advancement of new and exciting technologies within
the industry.
ISO 6326-1:2007 gives a
brief description of standardized methods that can be used for the
determination of sulfur compounds in natural gas. The principle of each method
is described generally, the range of concentrations for which the method is
suitable It should enable the user to select judiciously the proper method
for the application being considered. Sulfur analysis is performed in order
to determine total sulfur, sulfur contained in specific groups [e.g. thiols
(mercaptans)], individual sulfur compounds and specific groups of sulfur
compounds.
The available standardized methods in the
field of sulfur analysis are the Wickbold combustion method for total sulfur
determination (ISO 4260); the Lingener combustion method for total sulfur
determination (ISO 6326-5); gas chromatography for
determination of individual sulfur compounds (ISO 19739); potentiometry for
determination of hydrogen sulfide, carbonyl sulfide and thiol compounds (ISO
6326-3).
Sulfur
compounds can occur naturally in natural gas and remain as traces after
treatment, or they may have been injected deliberately to allow subsequent
olfactory detection for safety reasons.
The
standardization of several methods for the determination of sulfur compounds in
natural gas is necessary in view of the diversity of these compounds [hydrogen sulfide, carbonyl sulfide, tetrahydrothiophene
(THT), etc.] and the requirements of the determinations (required
uncertainty, measurement at the well head, at clean-up plant or in the
transmission pipes, etc.).
Tetrahydrothiophene is a heterocyclic organic compound consisting of a five-membered
ring containing four carbon atoms and a sulfur atom. It is the saturated analog
of thiophene. It is a volatile, clear, colorless
liquid with a strong unpleasant odor.
Because of its smell, tetrahydrothiophene is occasionally used as an odorant in natural gas, in place of the more common ethanethiol. It is also used as a solvent, as an insecticide, and as a moth repellent. It is an intermediate in the
preparation of the solvent sulfolane, which is
produced by the oxidation of
tetrahydrothiophene. It is also used as an electrolyte for lithium batteries.
As an odorant, it has numerous advantages against ethanethiol. It is not corrosive to the gas pipes and valves, it does
not cause habitual deactivation of sense of smell, and it does not cause
irritant responses of coughing, tears, and headache. It is regarded
to be an ideal gas indicator in use
The
other parts of ISO 6326 and ISO 19739 describe in detail the various
standardized methods.
Gas
Chromatograph
The gas chromatograph determines the gas
composition. The gas components are defined: Methane C1 Ethane C2
Propane C3 Iso-butane i−C4 Normal butane n−C4 Iso-pentane
i−C5 Normal pentane n−C5 Hexane and heavier hydrocarbons
C6+ Nitrogen N2 Carbon dioxide CO2 In each
analysis, the gas chromatograph performs the following calculations, in
accordance with ISO 6976 ,Gross Calorific Value at reference conditions,
Relative density ,Wobbe index
Density at reference conditions
The chromatograph periodically carries out
a calibration gas analysis, either, automatically or manually. The response
factors for each component are tested between two successive calibration
analyses. Variations of these should be within limits specified by
international standard ISO 6974.
Gas Chromatograph Calibration This
procedure includes:
Response factors check resulting from
consecutive analysis of the calibration gas based on the international standard
ISO 6974 .Concentrations check resulting from consecutive analysis of the
standard gas
calculation check of Gross Calorific Value
of natural gas from the chromatograph based on the international standard ISO
6976 and check of the certified composition of standard gas on chromatograph.
Superior calorific value:
The amount of heat which would be released
by the complete combustion in air of a specified quantity of gas, in such a way
that the pressure p1 at which the reaction takes place remains constant, and
all the products of combustion are returned to the same specified temperature
t1 as that of the reactants, all of these products being in the gaseous state
except for water formed by combustion, which is condensed to the liquid state
at t1.
A synonym
for calorific value is the term heating value. Calorific values can be
specified on a molar or mass basis. Then the calorific value depends on the
combustion reference conditions t1 and p1. More commonly, calorific values are
determined based upon a volumetric basis ;in this instance, the calorific value
needs to be specified with the combustion reference conditions t1 and p1 as
well as the volumetric reference conditions t2 and p2.
Wobbe index:
The superior calorific value on a volumetric basis at specified
reference conditions, divided by the square root of the relative density at the
same specified metering reference conditions.
The Wobbe index is an important quality designation for natural
gas, which is commonly used to determine trade prices and the
interchangeability of natural gas.
Origin
and history of NG
The discovery of natural gas dates from
ancient times in the Middle East. Thousands of
years ago, it was noticed that natural gas seeps ignited when lightning and
created "burning springs". In Persia,
Greece or India, people
built temples around these "eternal flames" for their religious
practices. However they did not recognize the energy value of natural gas. It
was done in China
around 900 BC. The Chinese drilled the first known natural gas well in 211 BC.
In Europe, natural gas was unknown until
it was discovered in Great
Britain in 1659 although it was not
commercialized until about 1790. In 1821 in Fredonia, United States,
residents observed gas bubbles rising to the surface from a creek. William Hart, considered as America's "father of natural gas", dug
there the first natural gas well in North America.
Throughout the 19th century, natural gas
was used almost exclusively as source of light and its use remained localized
because of lack of transport structures, making difficult to transport large
quantities of natural gas through long distances. There was an important change
in 1890 with the invention of leak proof pipeline coupling. However, existing
techniques did not allow for gas going further than 160 km. and it was mostly
flared of left in the earth. Transportation of natural gas to long distances
became practical in the 1920s as a result of technological advances in
pipelines. It was only after World War II that the use of natural gas grew
rapidly because of the development of pipeline networks and storage systems.
In the early days of oil exploration,
natural gas was often an unwelcome by-product, as natural gas reservoirs were
tapped in the drilling process and workers were forced to stop drilling to let
the gas vent freely into the air. Now, and particularly after the oil shortages
of the seventies, natural gas has become an important source of energy in the
world.
The gas industry has been highly regulated
for many years mainly as it was regarded as a natural monopoly. In the last 30
years there has been a move away from price regulation and towards
liberalization of natural gas markets. These movements have resulted in greater
competition in the market and in a dynamic and innovative natural gas industry.
In addition, thanks to technological advances natural gas can be better
explored, extracted and transported to consumers. Innovations also help to
improve natural gas applications and create new ones. Natural gas is
increasingly used for power generation.
Natural gas is a fossil fuel source of
energy, which represents more than one fifth of total energy consumption in the
world. It has been the fastest growing fossil fuel since the seventies.
Due to economical and ecological
advantages that it presents as well as its safety qualities (e.g. reduced
flammable range), natural gas is an increasingly attractive source of energy in
many countries. At present, natural gas is the second energy source after oil.
According to Energy Information Administration, natural gas accounted for 23%
of world energy production in 1999. It has excellent perspectives for future
demand. Natural gas is considered the fossil fuel of this century, as petroleum
was last century and coal two centuries ago.
Total primary energy supply by fuel
Source: World Energy Outlook 2000,
International Energy Agency
Natural gas presents a competitive
advantage over other energy sources. It is seen as economically more efficient
because only about ten per cent of the natural gas produced is wasted before it
gets to final consumption. In addition, technological advances are constantly
improving efficiencies in extraction, transportation and storage techniques as
well as in equipment that uses natural gas.
Natural gas is considered as an
environmentally friendly clean fuel, offering important environmental benefits
when compared to other fossil fuels. The superior environmental qualities over
coal or oil are that emissions of sulphur dioxide are negligible or that the
level of nitrous oxide and carbon dioxide emissions is lower. This helps to
reduce problems of acid rain, ozone layer or greenhouse gases.
Natural gas is also a very safe source of
energy when transported, stored and used.
Although resources of natural gas are finite and natural gas is a non-renewable source of energy, these resources are plentiful all over the world. Natural gas reserves are continuously increasing as new exploration and extraction techniques allow for wider and deeper drilling.
Although resources of natural gas are finite and natural gas is a non-renewable source of energy, these resources are plentiful all over the world. Natural gas reserves are continuously increasing as new exploration and extraction techniques allow for wider and deeper drilling.
The growing importance of natural gas as a
major energy source is shown by the amount of investment devoted to the natural
gas industry. The sector shows a great dynamism at the beginning of the new
millennium. Increasing demand and prices in the recent past have led to new
expansion and exploration projects in the natural gas industry. New pipeline
construction projects are developed and planned all over the world.
Furthermore, most governments are progressively including natural gas in their
energy policy agenda, by following liberalization policies (particularly after
the energy shortages of 1970s), in order to open the markets to competition.
More and more, energy final users are also showing a preference for using
natural gas as a clean, safe, reliable and economical source of energy. Natural
gas is used for heating, cooling and several other industry uses, while it is
increasingly becoming the favoured fuel for power generation.
Natural gas is colourless,
odourless, tasteless, shapeless and lighter than air. It is gaseous at
any temperature over -161º C. When it is at
its natural state, it is not possible to see or smell natural gas. For safety
reasons, a chemical odorant that smells a little like rotten eggs, Mercaptan, is added to natural gas so that it can be
smelled if there is a gas leak.
Natural gas is a mixture of light
hydrocarbons including methane, ethane, propane, butanes and pentanes. Other compounds found in natural gas include CO2, helium,
hydrogen sulphide and nitrogen. The composition of natural gas is never
constant, however, the primary component of natural gas is methane (typically,
at least 90%), which has a simple hydrocarbon structure composed of one carbon
atom and four hydrogen atoms (CH4). Methane is highly flammable, burns easily
and almost completely, while it emits very little air pollution. Natural gas is neither corrosive nor toxic, its ignition
temperature is high, and it has a narrow flammability range, making it an
inherently safe fossil fuel compared to other fuel sources. In addition,
because of its specific gravity of 0.60, lower than that of air (1.00), natural
gas rises if escaping, thus dissipating from the site of any leak.
The carbon
and hydrogen in natural gas are thought to have originated from the remains of
plants and animals that were accumulated at the bottom of lakes and oceans over
millions of years. After having been buried under huge layers of
other sediments, the organic material is transformed into crude oil and natural
gas as a result of the high pressure from the layers of sediments and the heat
from the earth's core. The oil and gas are then squeezed out of the marine
shales in which they were deposited, and from there go into porous sedimentary
rocks. Oil and gas migrates upward through the porous rock, as it is less dense
than the water, which fills the pores. Several different types of oil and gas
"traps" exist.
Natural gas is found throughout the world
in reservoirs deep beneath the surface of the earth and floor of the oceans. It
forms as pockets of gas over crude oil deposits or is trapped in porous rock
formations. Natural gas can be found in oil deposits, as associated natural
gas, although non-associated natural gas is often found without the presence of
oil.
When natural gas is cooled to a
temperature of approximately -260°F at atmospheric pressure, it condenses to a liquid called liquefied natural gas (LNG). One volume of
this liquid takes up about 1/600th the volume of natural gas. LNG weighs less
than one-half that of water, actually about 45% as much. LNG is odourless,
colourless, non-corrosive, and non-toxic. When vaporized it burns only in
concentrations of 5% to 15% when mixed with air. Neither LNG, nor its vapour,
can explode in an unconfined environment. Since LNG takes less volume and
weight, natural gas is liquefied for ease of storing and transporting.
Natural gas is considered as a clean
fuel because of its environmentally friendly properties: commercialised natural
gas is practically sulphur free and thus it produces virtually no sulphur
dioxide (SO2), natural gas emits lower levels of nitrogen oxides (NOx) emissions
than oil or coal and emissions of carbon dioxide (CO2) are less than those of
other fossil fuels (According to Eurogas 40-50% less than coal and 25-30% less
than oil).
Quality
Quantities of natural gas are measured in
cubic metres (at a pressure of 75,000 Pascal and a temperature of 15º C) or in
cubic feet (at the same pressure and temperature). Normally, gas production
from wells and supplies to power plants are measured in thousands or millions
of cubic feet (Mcf and MMcf); resources and reserves are calculated in
trillions of cubic feet (Tcf).
The amount of energy that is obtained from
the burning of a volume of natural gas is measured in British thermal units
(Btu). The value of natural gas is calculated by its Btu content. One Btu is
the quantity of heat required to raise the temperature of one pound of water of
1 degree Fahrenheit at atmospheric pressure. A cubic foot of natural gas on the
average gives off 1,000 Btu, but the range of values is between 500 and 1,500
Btu.
Energy content of natural gas is variable
and depends on its accumulations which are influenced by the amount and types
of energy gases they contain: the more non-combustible gases in a natural gas,
the lower the Btu value. In addition, the volumic mass of energy gases which are
present in a natural gas accumulation also influences the Btu value of natural
gas. The more carbon atoms in a hydrocarbon gas, the higher its Btu value.
Btu analyses of natural gas are done at
each stage of the supply chain. Gas chromatographic process analysers are used
in order to conduct fractional analysis of the natural gas streams, separating
natural gas into identifiable components. The components and their
concentrations are converted into a gross heating value in Btu-cubic foot.
The composition of natural gas varies
depending on the field, formation or reservoir from which it is extracted. The
different hydrocarbons that form natural gas can be separated using their
different physical properties as weight, boiling point or vapour pressure. Depending
on its content of heavy components, natural gas can be considered as rich (five
or six gallons or more of recoverable hydrocarbons per cubic feet) or lean
(less than one gallon of recoverable hydrocarbons per cubic feet).
Normally, natural gas as it is when
extracted is not suitable for pipeline transportation or commercial use before
being processed. Natural gas for commercial distribution is composed almost
entirely of methane and ethane, while moisture and other components have been
removed. Pipelines set their specifications for the quality of natural gas. In
any case, natural gas must be processed in order to remove unwanted water
vapour, solids or other contaminants and to get those hydrocarbons that have a
higher value as separate products.
Natural gas is the cleanest of all the
fossil fuels, as evidenced in the Environmental Protection Agency’s data
comparisons in the chart below, which is still current as of 2010. Composed
primarily of methane, the main products of the combustion of natural gas are carbon dioxide and water vapor,
the same compounds we exhale when we breathe. Coal and oil are composed of much
more complex molecules, with a higher carbon ratio and higher nitrogen and
sulfur contents. This means that when combusted, coal and oil release higher
levels of harmful emissions, including a higher ratio of carbon emissions,
nitrogen oxides (NOx), and sulfur dioxide (SO2). Coal and fuel oil also release
ash particles into the environment, substances that do not burn but instead are
carried into the atmosphere and contribute to pollution. The combustion of
natural gas, on the other hand, releases very small amounts of sulfur dioxide
and nitrogen oxides, virtually no ash or particulate matter, and lower levels
of carbon dioxide, carbon monoxide, and other reactive hydrocarbons.
Fossil Fuel Emission Levels
- Pounds per Billion Btu of Energy Input |
|||
Pollutant
|
Natural Gas
|
Oil
|
Coal
|
Carbon Dioxide
|
117,000
|
164,000
|
208,000
|
Carbon Monoxide
|
40
|
33
|
208
|
Nitrogen Oxides
|
92
|
448
|
457
|
Sulfur Dioxide
|
1
|
1,122
|
2,591
|
Particulates
|
7
|
84
|
2,744
|
Mercury
|
0.000
|
0.007
|
0.016
|
Source: EIA - Natural Gas Issues and
Trends 1998
|
|||
Natural gas, as the cleanest of the fossil
fuels, can be used in many ways to help reduce the emissions of pollutants into
the atmosphere. Burning natural gas in the place of other fossil fuels emits
fewer harmful pollutants, and an increased reliance on natural gas can
potentially reduce the emission of many of these most harmful pollutants.
Pollutants emitted in the United States,
particularly from the combustion of fossil fuels, have led to the development
of many pressing environmental problems. Natural gas, emitting fewer harmful
chemicals into the atmosphere than other fossil fuels, can help to mitigate
some of these environmental issues. These issues include:
Global warming, or the 'greenhouse effect'
is an environmental issue that deals with the potential for global climate
change due to increased levels of atmospheric 'greenhouse gases'. There are
certain gases in our atmosphere that serve to regulate the amount of heat that
is kept close to the earth's surface. Scientists theorize that an increase in
these greenhouse gases will translate into increased temperatures around the
globe, which would result in many disastrous
environmental effects. In fact, the Intergovernmental Panel on Climate Change
(IPCC) predicts in its 'Fourth Assessment Report' released in 2007 that during the 21st century, global
average temperatures are expected to rise by between 2.0 and 11.5 degrees
Fahrenheit. A Fifth Assessment Report is expected to be released by the
IPCC between 2013 and 2015.
The principle greenhouse gases include
water vapor, carbon dioxide, methane, nitrogen oxides, and some engineered
chemicals such as chlorofluorocarbons. While most of these gases occur in the
atmosphere naturally, levels have been increasing due to the widespread burning
of fossil fuels by growing human populations. The reduction
of greenhouse gas emissions has become a primary focus of environmental
programs in countries around the world.
One of the principle greenhouse gases is
carbon dioxide. Although carbon dioxide does not trap heat as effectively as
other greenhouse gases (making it a less potent greenhouse gas), the sheer
volume of carbon dioxide emissions into the atmosphere is very high,
particularly from the burning of fossil fuels. In fact, according to the Energy
Information Administration in its December 2009 report 'Emissions of Greenhouse Gases’
in the United States, 81.3 percent of greenhouse gas emissions in the United States
in 2008 came from energy-related carbon dioxide.
Because carbon dioxide makes up such a
high proportion of U.S.
greenhouse gas emissions, reducing carbon dioxide emissions can play a pivotal
role in combating the greenhouse effect and global warming. The combustion of
natural gas emits almost 30 percent less carbon dioxide than oil, and just
under 45 percent less carbon dioxide than coal.
One issue that has arisen with respect to
natural gas and the greenhouse effect is the fact that methane, the principle
component of natural gas, is itself a potent greenhouse gas. Methane has an ability to trap heat almost 21 times more
effectively than carbon dioxide. According to the Energy
Information Administration, although methane emissions account for
only 1.1 percent of total U.S.
greenhouse gas emissions, they account for 8.5 percent of the greenhouse gas
emissions based on global warming potential. Sources of methane emissions in
the U.S.
include the waste management and operations industry, the agricultural
industry, as well as leaks and emissions from the oil and gas industry itself.
A major study performed by the Environmental Protection Agency (EPA) and the
Gas Research Institute (GRI), now Gas Technology Institute,
in 1997 sought to discover whether the reduction in carbon dioxide emissions
from increased natural gas use would be offset by a possible increased level of
methane emissions. The study concluded that the reduction in emissions from
increased natural gas use strongly outweighs the detrimental effects of
increased methane emissions. More recently in 2011, researchers at the
Carnegie Mellon University released “Life cycle greenhouse gas emissions of
Marcellus shale gas”, a report comparing greenhouse gas
emissions from the Marcellus Shale region with emissions from coal used for
electricity generationIn 1993, the natural gas industry joined with EPA in
launching the Natural Gas STAR Program to reduce methane emissions. The
STAR program has chronicled dramatic reductions to methane emissions, since
that time:
Smog and poor air quality is a pressing
environmental problem, particularly for large metropolitan cities. Smog, the
primary constituent of which is ground level ozone, is formed by a chemical
reaction of carbon monoxide, nitrogen oxides, volatile organic compounds, and
heat from sunlight. As well as creating that familiar smoggy haze commonly
found surrounding large cities, particularly in the summer time, smog and
ground level ozone can contribute to respiratory problems ranging from
temporary discomfort to long-lasting, permanent lung damage. Pollutants
contributing to smog come from a variety of sources, including vehicle
emissions, smokestack emissions, paints, and solvents. Because the reaction to
create smog requires heat, smog problems are the worst in the summertime.
The use of
natural gas does not contribute significantly to smog formation, as it emits
low levels of nitrogen oxides, and virtually no particulate matter. For this
reason, it can be used to help combat smog formation in those areas where
ground level air quality is poor. The main sources of nitrogen oxides are
electric utilities, motor vehicles, and industrial plants. Increased natural
gas use in the electric generation sector, a shift to cleaner natural gas
vehicles, or increased industrial natural gas use, could all serve to combat
smog production, especially in urban centers where it is needed the most.
Particularly in the summertime, when natural gas demand is lowest and smog
problems are the greatest, industrial plants and electric generators could use
natural gas to fuel their operations instead of other, more polluting fossil
fuels. This would effectively reduce the emissions of smog causing chemicals,
and result in clearer, healthier air around urban centers.
For more
information on smog, including the major contributors to smog formation and
what is currently being done to combat smog levels, visit the EPA's smog information section.
Particulate emissions also cause the degradation of air quality in the United States. These
particulates can include soot, ash, metals, and other airborne particles. Natural gas emits virtually no particulates into the atmosphere: in fact, emissions of particulates from natural gas combustion are 90 percent lower than from the combustion of oil, and 99 percent lower than burning coal.
Acid rain is another
environmental problem that affects much of the Eastern
United States, damaging crops, forests, wildlife populations, and
causing respiratory and other illnesses in humans. Acid rain is formed when
sulfur dioxide and nitrogen oxides react with water vapor and other chemicals
in the presence of sunlight to form various acidic compounds in the air. The principle
source of acid rain-causing pollutants, sulfur dioxide and nitrogen oxides, are
coal fired power plants. Since natural gas emits
virtually no sulfur dioxide, and up to 80 percent less nitrogen oxides than the
combustion of coal, increased use of natural gas could provide for fewer acid
rain causing emissions.
The use of
natural gas to power both industrial boilers and processes and the generation
of electricity can significantly improve the emissions profiles for these two
sectors.
Natural gas is becoming an increasingly
important fuel in the generation of electricity. As well as providing an
efficient, competitively priced fuel for the generation of electricity, the
increased use of natural gas allows for the improvement in the emissions
profile of the electric generation industry. According to the National
Environmental Trust (NET), Natural gas-fired electric generation and natural
gas-powered industrial applications offer a variety of environmental benefits
and environmentally friendly uses, including:
Fewer Emissions - Combustion
of natural gas, used in the generation of electricity, industrial boilers, and
other applications, emits lower levels of NOx, CO2, and particulate emissions,
and virtually no SO2 and mercury emissions. Natural gas can be used in
place of, or in addition to, other fossil fuels, including coal, oil, or
petroleum coke, which emit significantly higher levels of these pollutants.
Reduced Sludge – Coal-fired power plants and
industrial boilers that use scrubbers to reduce SO2 emissions levels generate
thousands of tons of harmful sludge. Combustion of
natural gas emits extremely low levels of SO2, eliminating the need for
scrubbers, and reducing the amounts of sludge associated with power plants and
industrial processes.
Reburning - This process involves injecting
natural gas into coal or oil fired boilers. The
addition of natural gas to the fuel mix can result in NOx emission reductions
of 50 to 70 percent, and SO2 emission reductions of 20 to 25 percent.
Cogeneration - The production and use of both
heat and electricity can increase the energy efficiency of electric generation
systems and industrial boilers, which translates to the combustion of less fuel
and the emission of fewer pollutants. Natural gas is the preferred choice for
new cogeneration applications.
Combined Cycle Generation – Combined-cycle
generation units generate electricity and capture normally wasted heat energy,
using it to generate more electricity. Like cogeneration applications, this
increases energy efficiency, uses less fuel, and thus produces fewer emissions.
Natural gas-fired combined-cycle generation units can be up to 60 percent
energy efficient, whereas coal and oil generation units are typically only 30
to 35 percent efficient.
Fuel Cells - Natural
gas fuel cell technologies are in development for the generation of
electricity. Fuel cells are sophisticated devices that use hydrogen to generate
electricity, much like a battery. No emissions are involved in the generation
of electricity from fuel cells, and natural gas, being a hydrogen rich source
of fuel, can be used. Although still under development, widespread use of fuel
cells could in the future significantly reduce the emissions associated with the
generation of electricity.
Essentially, electric generation and
industrial applications that require energy, particularly for heating, use the
combustion of fossil fuels for that energy. Because of its clean burning
nature, the use of natural gas wherever possible, either in conjunction with
other fossil fuels, or instead of them, can help to reduce the emission of
harmful pollutants.
According to the Congressional Research
Service’s 2010 report: “Displacing
Coal with Generation from Existing Natural-Gas Fired Power Plants,” if
natural-gas combined cycle plants utilization were to be doubled from 42
percent capacity factor to 85 percent, then the amount of power generated would
displace 19 percent of the CO2 emissions attributed to coal-fired electricity generation.
The
transportation sector (particularly cars, trucks, and buses) is one of the
greatest contributors to air pollution in the United States. Emissions from
vehicles contribute to smog, low visibility, and various greenhouse gas
emissions. According to the Department of Energy
(DOE), about half of all air pollution and more than 80 percent of air
pollution in cities are produced by cars and trucks in the United States.
Currently, automobile manufacturers are under pressure to produce more
environmentally friendly vehicles.
Natural gas can be used in the
transportation sector to cut down on these high levels of pollution from
gasoline and diesel powered cars, trucks, and buses. According to the EPA,
compared to traditional vehicles, vehicles operating on compressed natural
gas have reductions in carbon monoxide emissions of 90 to 97 percent, and
reductions in carbon dioxide emissions of 25 percent. Nitrogen oxide
emissions can be reduced by 35 to 60 percent, and other non-methane hydrocarbon
emissions could be reduced by as much as 50 to 75 percent.
Thanks for given detail information to me. keep posting like this. Natural Gas & Environment
ReplyDelete