World organizations and international agencies, like the IEA, are concerned about the environmental impact of burning fossil fuels, and coal in particular. The combustion of coal contributes the most to acid rain and air pollution, and has been connected with global warming. Due to the chemical composition of coal there are difficulties in removing impurities from the solid fuel prior to its combustion. Modern day coal power plants pollute less than older designs due to new "scrubber" technologies that filter the exhaust air in smoke stacks; however emission levels of various pollutants are still on average several times greater than natural gas power plants. In these modern designs, pollution from coal-fired power plants comes from the emission of gases such as carbon dioxide, nitrogen oxides, and sulfur dioxide into the air.
Acid rain is caused by the emission of nitrogen oxides and sulfur dioxide. These gases may be only mildly acidic themselves, yet when they react with the atmosphere, they create acidic compounds such as sulfurous acid,nitric acid and sulfuric acid which fall as rain, hence the term acid rain. In Europe and the U.S.A., stricter emission laws and decline in heavy industries have reduced the environmental hazards associated with this problem, leading to lower emissions after their peak in 1960s.
Carbon dioxide
Of the fossil fuels, coal is much more carbon intensive than oil or natural gas, resulting in greater volumes of carbon dioxide emissions per unit of electricity generated. In 2010, coal contributed about 81% of CO2 emissions from generation and contributed about 45% of the electricity generated in the United States.[12] In 2000, the carbon intensity of U.S. coal thermal combustion was 2249 lbs/MWh (1,029 kg/MWh).[13]) while the carbon intensity of U.S. oil thermal generation was 1672 lb/MWh (758 kg/MWh or 211 kg/GJ)[14] and the carbon intensity of U.S. natural gas thermal production was 1135 lb/MWh (515 kg/MWh or 143 kg/GJ).[15])Electricity generation using carbon based fuels is responsible for a large fraction of carbon dioxide (CO2) emissions worldwide and for 34% of U.S. man-made carbon dioxide emissions in 2010. In the U.S., 70% of electricity generation is produced from combustion of fossil fuels.[11]
The Intergovernmental Panel on Climate Change (see IPCC) states that carbon dioxide is a greenhouse gas and that increased quantities within the atmosphere will "very likely" lead to higher average temperatures on a global scale (global warming); concerns regarding the potential for such warming to change the global climate prompted IPCC recommendations calling for large cuts to CO2 emissions worldwide.[16]
Emissions may be reduced through more efficient and higher combustion temperature and through more efficient production of electricity within the cycle. Carbon capture and storage (CCS) of emissions from coal-fired power stations is another alternative but the technology is still being developed and will increase the cost of fossil fuel-based production of electricity. CCS may not be economically viable, unless the price of emitting CO2 to the atmosphere rises.
Particulate matter
U.S. Coal-fired Power Plants: Update or Close:
The plants' respective owners, the Tennessee Valley Authority and American Electric Power Co. Inc., also have some things in common. They are two of the nation's largest electric utilities with a combined 14 million customers in 17 contiguous states from Ohio to Texas. Both also have long histories of bringing inexpensive power to Appalachia, one of the nation's poorest regions.
But when it comes to their futures, the Gallatin and Big Sandy coal plants have met sharply divergent paths, with significant implications for their surrounding regions. The 976-megawatt Gallatin plant, built in the 1950s on a bend in the Cumberland River 30 miles east of downtown Nashville, will soon undergo an estimated $1.1 billion in upgrades to its environmental controls, potentially securing the plant's operation well into the 21st century.
"The Gallatin project will further improve air quality in the Tennessee Valley, which is cleaner today than it has been in decades," TVA executives said last month when they announced the plant would be retrofitted with sulfur dioxide scrubbers and selective catalytic reduction units to help reduce nitrogen oxides, a primary ingredient in ground-level ozone.
Meanwhile, Big Sandy, with 1,078 MW of generation capacity, will produce its last power in 2015, making it one of the largest coal plants in the country to give way to economic, regulatory and public pressures that are challenging coal's role as the dominant fuel for electricity in the United States. AEP subsidiary Kentucky Power decided to shutter Big Sandy late last year after reversing course on its own planned $1 billion investment in that plant's environmental controls.
From the website Energy.Gov
Renewable Energy
A clean energy revolution is taking place across America, underscored by the steady expansion of the U.S. renewable energy sector.
The clean energy industry generates hundreds of billions in economic activity, and is expected to continue to grow rapidly in the coming years. There is tremendous economic opportunity for the countries that invent, manufacture and export clean energy technologies.
Another problem related to coal combustion is the emission of particulates that have a serious impact on public health. Power plants remove particulate from the flue gas with the use of a bag house or electrostatic precipitator. Several newer plants that burn coal use a different process, Integrated Gasification Combined Cycle in which synthesis gas is made out of a reaction between coal and water. The synthesis gas is processed to remove most pollutants and then used initially to power gas turbines. Then the hot exhaust gases from the gas turbines are used to generate steam to power a steam turbine. The pollution levels of such plants are drastically lower than those of "classic" coal power plants.[17]
Particulate matter from coal-fired plants can be harmful and have negative health impacts. Studies have shown that exposure to particulate matter is related to an increase of respiratory and cardiac mortality.[18] Particulate matter can irritate small airways in the lungs, which can lead to increased problems with asthma, chronic bronchitis, airway obstruction, and gas exchange.[18]
There are different types of particulate matter, depending on the chemical composition and size. The dominant form of particulate matter from coal-fired plants is coal fly ash, but secondary sulfate and nitrate also comprise a major portion of the particulate matter from coal-fired plants.[19] Coal fly ash is what remains after the coal has been combusted, so it consists of the incombustible materials that are found in the coal.[20]
The size and chemical composition of these particles affects the impacts on human health.[18][19] Currently coarse (diameter greater than 2.5 μm) and fine (diameter between 0.1 μm and 2.5 μm) particles are regulated, but ultrafine particles (diameter less than 0.1 μm) are currently unregulated, yet they pose many dangers.[18]Unfortunately much is still unknown as to which kinds of particulate matter pose the most harm, which makes it difficult to come up with adequate legislation for regulating particulate matter.[19]
Particulate matter from coal-fired plants can be harmful and have negative health impacts. Studies have shown that exposure to particulate matter is related to an increase of respiratory and cardiac mortality.[18] Particulate matter can irritate small airways in the lungs, which can lead to increased problems with asthma, chronic bronchitis, airway obstruction, and gas exchange.[18]
There are different types of particulate matter, depending on the chemical composition and size. The dominant form of particulate matter from coal-fired plants is coal fly ash, but secondary sulfate and nitrate also comprise a major portion of the particulate matter from coal-fired plants.[19] Coal fly ash is what remains after the coal has been combusted, so it consists of the incombustible materials that are found in the coal.[20]
The size and chemical composition of these particles affects the impacts on human health.[18][19] Currently coarse (diameter greater than 2.5 μm) and fine (diameter between 0.1 μm and 2.5 μm) particles are regulated, but ultrafine particles (diameter less than 0.1 μm) are currently unregulated, yet they pose many dangers.[18]Unfortunately much is still unknown as to which kinds of particulate matter pose the most harm, which makes it difficult to come up with adequate legislation for regulating particulate matter.[19]
Radioactive trace elements
Coal is a sedimentary rock formed primarily from accumulated plant matter, and it includes many inorganic minerals and elements which were deposited along with organic material during its formation. As the rest of the Earth's crust, coal also contains low levels of uranium, thorium, and other naturally occurring radioactive isotopes whose release into the environment leads to radioactive contamination. While these substances are present as very small trace impurities, enough coal is burned that significant amounts of these substances are released. A 1,000 MW coal-burning power plant could have an uncontrolled release of as much as 5.2 metric tons per year of uranium (containing 74 pounds (34 kg) of uranium-235) and 12.8 metric tons per year of thorium.[22] In comparison, a 1,000 MW nuclear plant will generate about 30 metric tons of high-level radioactive solid packed waste per year.[23] It is estimated that during 1982, US coal burning released 155 times as much uncontrolled radioactivity into the atmosphere as the Three Mile Island incident.[24] The collective radioactivity resulting from all coal burning worldwide between 1937 and 2040 is estimated to be 2,700,000 curies or 0.101 EBq.[22] It should also be noted that during normal operation, the effective dose equivalent from coal plants is 100 times that from nuclear plants.[22] But it is also worth noting that normal operation is a deceiving baseline for comparison: just the Chernobyl nuclear disaster released, in iodine-131 alone, an estimated 1.76 EBq .[25] of radioactivity, a value one order of magnitude above this value for total emissions from all coal burned within a century. But at the same time, it shall also be understood that the iodine-131, the major radioactive substance which comes out in accident situations, has a half life of just 8 days.
Water and air contamination by coal ash
A study released in August 2010 that examined state pollution data in the United States by the organizations Environmental Integrity Project, the Sierra Club and Earthjustice found that coal ash produced by coal-fired power plants dumped at sites across 21 U.S. states has contaminated ground water with toxic elements. The contaminants including the poisons arsenic and lead.[26]
Arsenic has been shown to cause skin cancer, bladder cancer and lung cancer, and lead damages the nervous system.[27] Coal ash contaminants are also linked to respiratory diseases and other health and developmental problems, and have disrupted local aquatic life.[26] Coal ash also releases a variety of toxic contaminants into nearby air, posing a health threat to those who breath in fugitive coal dust. [27]
Currently, the EPA does not regulate the disposal of coal ash; regulation is up to the states and the electric power industry has been lobbying to maintain this status quo. Most states require no monitoring of drinking water near coal ash dump sites. The study found an additional 39 contaminated U.S. sites and concluded that the problem of coal ash-caused water contamination is even more extensive in the United States than has been estimated. The study brought to 137 the number of ground water sites across the United States that are contaminated by power plant-produced coal ash.[26]
Mercury contamination
U.S. government scientists tested fish in 291 streams around the country for mercury contamination. They found mercury in every fish tested, according to the study by the U.S. Department of the Interior. They found mercury even in fish of isolated rural waterways. Twenty five percent of the fish tested had mercury levels above the safety levels determined by the U.S. Environmental Protection Agency for people who eat the fish regularly. The largest source of mercury contamination in the United States is coal-fueled power plant emissions.[28]
Updates on Energy sources in the United States of America
From the Scientific American website:
Updates on Energy sources in the United States of America
From the Scientific American website:
U.S. Coal-fired Power Plants: Update or Close:
The plants' respective owners, the Tennessee Valley Authority and American Electric Power Co. Inc., also have some things in common. They are two of the nation's largest electric utilities with a combined 14 million customers in 17 contiguous states from Ohio to Texas. Both also have long histories of bringing inexpensive power to Appalachia, one of the nation's poorest regions.
But when it comes to their futures, the Gallatin and Big Sandy coal plants have met sharply divergent paths, with significant implications for their surrounding regions. The 976-megawatt Gallatin plant, built in the 1950s on a bend in the Cumberland River 30 miles east of downtown Nashville, will soon undergo an estimated $1.1 billion in upgrades to its environmental controls, potentially securing the plant's operation well into the 21st century.
"The Gallatin project will further improve air quality in the Tennessee Valley, which is cleaner today than it has been in decades," TVA executives said last month when they announced the plant would be retrofitted with sulfur dioxide scrubbers and selective catalytic reduction units to help reduce nitrogen oxides, a primary ingredient in ground-level ozone.
Meanwhile, Big Sandy, with 1,078 MW of generation capacity, will produce its last power in 2015, making it one of the largest coal plants in the country to give way to economic, regulatory and public pressures that are challenging coal's role as the dominant fuel for electricity in the United States. AEP subsidiary Kentucky Power decided to shutter Big Sandy late last year after reversing course on its own planned $1 billion investment in that plant's environmental controls.
From the website Energy.Gov
Renewable Energy
A clean energy revolution is taking place across America, underscored by the steady expansion of the U.S. renewable energy sector.
The clean energy industry generates hundreds of billions in economic activity, and is expected to continue to grow rapidly in the coming years. There is tremendous economic opportunity for the countries that invent, manufacture and export clean energy technologies.
Sources: wikipedia.org, Energy.Gov, Scientific American.
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