Natural Gas and the Environment
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 fossil fuels. Composed primarily of methane, the main products of the combustion of natural gas are carbon dioxide and water vapor. These are 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
|Source: EIA – Natural Gas Issues and Trends 1
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 between 2.4 and 10.4 degrees Fahrenheit.
The principal 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 principal 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 principal component of natural gas, is itself a very potent greenhouse gas. In fact, methane has the 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.
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 summertime, 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 the 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 principal 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 fewer 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.
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 is a hydrogen-rich source of fuel, can be used. Although still under development, the 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.
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 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.