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Source: Anadarko
Petroleum Corporation |
Natural gas is an extremely important source of energy
for reducing pollution and maintaining a clean and healthy
environment. In addition to being a domestically abundant
and secure source of energy, the use of natural gas
also offers a number of environmental benefits over
other sources of energy, particularly other fossil fuels.
This section will discuss the environmental effects
of natural gas, in terms of emissions as well as the
environmental impact of the natural gas industry itself.
Scroll down, or click on the links below to be transported
ahead.
Emissions
from the Combustion of Natural Gas
Natural gas is the cleanest of all the fossil fuels.
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 |
The use of fossil fuels for energy contributes to a
number of environmental problems. As the
cleanest of the fossil fuels, natural gas 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 into the
atmosphere, 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:
Greenhouse Gas Emissions
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 'Third Assessment Report' released
in February 2001 that over the next 100 years, global
average temperatures will rise by between 2.4 and 10.4
degrees Fahrenheit.
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Power Plants Contribute to the
Emission of Greenhouse Gases |
Source: API |
The principle greenhouse gases include water vapor,
carbon dioxide, methane, nitrogen oxides, and some engineered
chemicals such as cholorofluorocarbons. 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 EIA in its
report 'Emissions of Greenhouse Gases in the United
States 2000', 81.2 percent of greenhouse gas emissions
in the United States in 2000 came from carbon dioxide
directly attributable to the combustion of fossil fuels.
Because carbon dioxide makes up such a high proportion
of U.S. greenhouse gas emissions, reducing carbon dioxide
emissions can play a huge 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
very potent greenhouse gas. In fact, 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) 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. Thus the increased use of natural gas in
the place of other, dirtier fossil fuels can serve to
lessen the emission of greenhouse gases in the United
States.
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Smog! - Natural Gas Can Help |
Source: EPA |
Smog, Air Quality and Acid Rain
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 instance, a 1995 study
by the Coalition for Gas-Based Environmental Solutions
found that in the Northeast, smog and ozone-causing
emissions could be reduced by 50 to 70 percent through
the seasonal switching to natural gas by electric generators
and industrial installations.
Particulate emissions also cause the degradation of
air quality in the United States. These particulates
can include soot, ash, metals, and other airborne particles.
A study by the Union
of Concerned Scientists in 1998, entitled 'Cars
and Trucks and Air Pollution', showed that the risk
of premature death for residents in areas with high
airborne particulate matter was 26 percent greater than
for those in areas with low particulate levels. 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. Thus
increased natural gas use in place of other dirtier
hydrocarbons can help to reduce particulate emissions
in the U.S.
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.
Industrial and Electric
Generation Emissions
Pollutant emissions from the industrial sector and
electric utilities contribute greatly to environmental
problems in the United States. 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) in their 2002 publication
entitled 'Cleaning up Air Pollution from America's Power
Plants', power plants in the U.S. account for 67 percent
of sulfur dioxide emissions, 40 percent of carbon dioxide
emissions, 25 percent of nitrogen oxide emissions, and
34 percent of mercury emissions. Coal fired power plants
are the greatest contributors to these types of emissions.
In fact, only 3 percent of sulfur dioxide emissions,
5 percent of carbon dioxide emissions, 2 percent of
nitrogen oxide emissions, and 1 percent of mercury emissions
come from non-coal fired power plants.
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Emissions from Industrial
Smokestacks |
Source: EPA |
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 requiring 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.
Pollution from the Transportation
Sector - Natural Gas Vehicles
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.
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Source: EPA |
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. In fact,
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. In
addition, because of the relatively simple makeup of
natural gas in comparison to traditional vehicle fuels,
there are fewer toxic and carcinogenic emissions from
natural gas vehicles, and virtually no particulate emissions.
Thus the environmentally friendly attributes of natural
gas may be used in the transportation sector to reduce
air pollution.
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 sound as possible. Learn about
the natural gas industry and the environmental effects of natural gas production.
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