And don't forget the list of pollutants that do come out of coal fired pwoer plants (no matter what colour the smoke is), including radioactive material, mercury, particulates, nitrogen oxides and sulphur dioxide (cause acid rain), fly ash and of course, carbon dioxide.
"Environmental impacts
The world's power demands are expected to rise 60% by 2030.[5] With the worldwide total of active coal plants over 50,000 and rising,[6] the International Energy Agency (IEA) estimates that fossil fuels will account for 85% of the energy market by 2030.[5]
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.
European Environment Agency (EEA) gives fuel-dependent emission factors based on actual emissions from power plants in EU.[7] Pollutant Hard coal Brown coal Fuel oil Other oil Gas CO2 (g/GJ) 94600 101000 77400 74100 56100 SO2 (g/GJ) 765 1361 1350 228 0.68 NOx (g/GJ) 292 183 195 129 93.3 CO (g/GJ) 89.1 89.1 15.7 15.7 14.5 Non methane organic compounds (g/GJ) 4.92 7.78 3.70 3.24 1.58 Particulate matter (g/GJ) 1203 3254 16 1.91 0.1 Flue gas volume total (m3/GJ) 360 444 279 276 272
Carbon dioxide
Electricity generation using carbon based fuels is responsible for a large fraction of carbon dioxide (CO2) emissions worldwide and for 41% of U.S. man-made carbon dioxide emissions.[8] Of fossil fuels, coal combustion in thermal power stations result in greater amounts of carbon dioxide emissions per unit of electricity generated (2249 lbs/MWh[9]) while oil produces less (1672 lb/(MW�h)[10] or 211 kg/GJ) and natural gas produces the least 1135 lb/(MW�h) (143 kg/GJ).[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.[12]
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
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.[13]
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.[14] Particulate matter can irritate small airways in the lungs, which can lead to increased problems with asthma, chronic bronchitis, airway obstruction, and gas exchange.[14]
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.[15] 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.[16]
The size and chemical composition of these particles affects the impacts on human health.[14][15] 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.[14] 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.[15]
There are several methods of helping to reduce the particulate matter emissions from coal-fired plants. Roughly 80% of the ash falls into an ash hopper, but the rest of the ash then gets carried into the atmosphere to become coal-fly ash.[16] Methods of reducing these emissions of particulate matter include:
a baghouse an electrostatic precipitator (ESP) cyclone collector
The baghouse has a fine filter that collects the ash particles, electrostatic precipitators use an electric field to trap ash particles on high-voltage plates, and cyclone collectors use centrifugal force to trap particles to the walls.[16]
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.[17] In comparison, a 1,000 MW nuclear plant will generate about 500 pounds of plutonium and 30 short tons of high-level radioactive controlled waste.[18] 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.[19] 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.[17] It should also be noted that during normal operation, the effective dose equivalent from coal plants is 100 times that from nuclear plants.[17] But it is also worth noting that normal operation is a deceiving baseline for comparison: just the Chernobyl nuclear disaster released, in of I-131 alone, an estimated 1,76 EBq [20] of radioactivity, a value one order of magnitude above this value for total emissions from all coal burned within a century.
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. [21]
Arsenic has been shown to cause skin cancer, bladder cancer and lung cancer, and lead damages the nervous system.[22] Coal ash contaminants are also linked to respiratory diseases and other health and developmental problems, and have disrupted local aquatic life.[21] Coal ash also releases a variety of toxic contaminants into nearby air, posing a health threat to those who breath in fugitive coal dust.[23]
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.[21]
Range of mercury contamination in fish
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.[24]"
