Coal is the undisputed leader in dirty fuel sources. But beyond the issue of global warming/climate change (burning coal is the number one source of the greenhouse gas, carbon dioxide), coal-fired power plants also release dangerously high levels of sulfur dioxide, nitrogen oxide, mercury, arsenic, lead, carbon monoxide and hydrocarbons into the atmosphere, creating environmental hazards both near the plants (i.e smog, respiratory complications, fouled water from coal-slurry impoundments), and far from the plants (i.e acid rain, mercury pollution in rivers and oceans, etc.). And that is only the burning of coal, to say nothing of the mining and transportation of it.
Generally speaking, the older the plant, the more polluting it is, but the type of coal burned also plays a significant role determining the amount of CO2, SO2 and other pollutants released into the atmosphere. That said, some coal plants are dirtier than others:
R. Gallagher – Indiana, USA
As one of the older plants on this list, Duke Energy's Gallagher Generating Station is also one of the dirtiest. Located along the banks of the Ohio River in Floyd County, Indiana, Gallagher stores coal fly ash in ponds on the banks of the Ohio River. But the relatively small 600-megawatt Gallagher station made the list mostly because it emits 50,819 tons of sulfur dioxide (SO2) annually—a ratio of about 4o pounds per megawatt-hour—the highest of any plant in the United States.
Kraftwerk Niederaussem – Bergheim, Germany
Owned by Germany's RWE Niederaussem is consistently one of the largest sources of CO2 in all of Europe. Even though the plant saw its emissions drop by 20 % to 24.9 million tons in 2008, the 3800 megawatt plant burns dirty and inefficient lignite (brown coal). Vast lignite mines in Germany, like the one pictured above, have swallowed entire villages and large swaths of fertile farmland.
Scherer Power Plant – Juliette, Georgia, USA
At 27 million tons of carbon dioxide annually, the Robert W. Scherer Power Plant is the single largest point-source of CO2 in the U.S.. Scherer is owned and operated by Georgia Power, which also owns the Bowen Plant. Scherer burns through an average of three train-loads of coal per day – coal hauled in from Wyoming's Powder River Basin, 1,800 miles away. At any given time, BNSF has thirty-six different two-mile long coal trains somewhere on the ten-day roundtrip between Wyoming and Georgia.
Taichung Coal-Fired Power Plant – Lung-Ching, Taiwan
The 4130-megawatt Taichung power station is the world's biggest CO2 emitter, with over 40 million tons produced in 2008. The CO2 emissions of the Taichung project roughly corresponds to the CO2 emissions of Switzerland.
Belchatow – Belchatow, Poland
Belchatow is arguably the largest coal-fired power plant in the world. Run by state-owned utility BOT Elektrownia, Belchatow emitted the most CO2 of any EU installation last year, pumping the equivalent of 34 million tons into the atmosphere; making it the second biggest coal-fired source of CO2 in the world.
Kendal Power Station – Mpumbulanga, South Africa
The 4116-megawatt Kendal facility in South Africa is the largest coal-fired power plant in the world. With an annual CO2 emissions of 26.8 millions tons, Kendal is the tenth biggest source of CO2 in the world.
Bowen – Bowen, Georgia, USA
Along with the Scherer Plant, which is also owned by Georgia Power, Plant Bowen is consistently one of the top three emitters of CO2 in the United States. In addition to the 24 million tons of CO2 it emits annually, Scherer is also one of the bigger sulfur dioxide sources, emitting 206,442 tons of SO2 annually (it should be noted that while the total amount of SO2 produced has a relatively low ratio of 18lb/MWh, as compared to Gallagher's 40lb/MWh).
Hazelwood – Hazelwood, Victoria, Australia
The WWF referred to Hazelwood power station as "the most polluting of all power stations operating in the world's major industrialised countries." Scheduled to be decommissioned by 2009 due to the exceedingly high volume of CO2 emissions from burning brown coal, a 2005 decision by the Victorian Government will keep the plant operational until 2031.
Agios Dimitrios – Agios Dimitrios, Greece
In terms of CO2 per Megawatt-hour produced, the 1595-megawatt Agios Dimitrios power plant in Greece is the dirtiest power plant in Europe. The lignite-burning facility was at the top (or bottom) of WWF's Dirty Thirty (Europe).
Drax – Selby, Yorkshire and the Humber, UK
Drax provides 7% of the electrical power required by Britain. Drax is actually the most carbon efficient coal-fired power plant in the UK, even though it generates around 1.5 million tons of ash and 22.8 million tons of carbon dioxide each year, which just goes to show, even the cleanest of coal-fired power plants are dirty.