Coal

Coal is that sooty black stuff one usually associates with the late 1800s and Santa Claus. But coal, a fossil fuel, is the largest source of energy for the generation of electricity worldwide, as well as one of the largest worldwide anthropogenic sources of global warming. Gross carbon dioxide emissions worldwide from coal usage are slightly more than those from petroleum and about double the amount from natural gas. Burning coal to produce electricity also releases the most carbon dioxide per kWh generated. Fun stuff. Exposure to coal in various forms is carcinogenic to humans. The emissions caused by coal power plants kill an estimated 10,000 people a year in the United States alone, and that's not even getting into things like mining accidents, coal power plant explosions, long-term health effects from mining such as black lung, and the general environmental destruction due to open-pit mining, making coal power several orders of magnitude more deadly than nuclear power.

Types of coal

 * Peat – basically coal that hasn't become coal yet, with it being somewhat wet and loose and having yet to go through lithification. However, by drying and compressing it, it can be used as a power source. It is most commonly used as such throughout northern Europe, but its harvesting can cause damage to the wetlands where it is produced.
 * Lignite – brown and ugly, really smoky, and isn't usually transported very far from where it is mined. It is usually mined open pit and thus creates huge disruptions of the natural environment for decades, even centuries.
 * Bituminous – this is what most people think of when they think of coal. It's lack, and still rather smoky and stinky.  Most Appalachian coal is bituminous. Wyoming's Powder River Basin coal is "sub-bituminous," which is somewhere between bituminous and the lower-quality lignite, hence cheaper, but for some reason has a lower sulfur content so it also widely used.
 * Anthracite – the better stuff. Well, better than the other two varieties, at least. It burns cleaner but is pricey and used mostly for  metallurgy and smelting rather than power generation. Only 1% of mined coal is anthracite. The largest anthracite reserves in the world are located in northeastern Pennsylvania.

Clean coal?
Clean coal is a buzzword oxymoron for coal power that is "clean" because they pump the emissions underground.

Coal mining
Coal mining is environmentally destructive and dangerous. Coal can cause "Black Lung," also known as coal worker' pneumoconiosis. On multiple occasions, miners have been trapped in coal mines for extended periods of time. Coal mining is often associated with Kentucky, the Ruhr, Silesia and Wales.



Reducing the danger to the miners often means increasing the environmental damage; open-pit mining is not nearly as hazardous as the underground variety, and mountaintop removal also much safer, but it also means mucking up the local environment to a much greater degree. Additionally, open-pit mines require considerably less workers than underground ones, so there are concerns about job security for the communities that still rely on harvesting coal.

Formation
Coal begins as layers of plant matter accumulate at the bottom of a body of water. For the process to continue, the plant matter must be protected from biodegradation and oxidization, usually by mud or acidic water; the wide shallow seas of the Carboniferous period provided such conditions. This trapped atmospheric carbon in the ground in immense peat bogs that were eventually covered over and deeply buried by sediments, under which they metamorphosed into coal. Over time, the chemical and physical properties of the plant remains (believed to mainly have been fern-like species antedating more modern plant and tree species) were changed by geological action to create a solid material.

In medicine
Coal oil was once used as a panacea, but has fallen into disuse. Coal tar, on the other hand, is an approved FDA ingredient for over-the-counter topical medicines. There is no evidence that coal tar causes cancer from short-term, low concentration topical use, even though coal tar is carcinogenic in humans from high-dose occupational exposure.