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.
Types of coal
- Lignite - brown[note 1] and ugly, really smoky[note 2], 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. Black, 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. Cleaner burning but pricey and rarely used. In the U.S. it is mainly found in northeastern Pennsylvania.
Clean coal is a buzzword for coal power that is "clean" because they pump the emissions underground.
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 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 a lot worse.
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 eventually were 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.
- Actually in most cases a piece of lignite is black or blackish, but if you "draw" with it, the line is brown
- Lignite commonly has a rather high sulfur content making it "dirtier" still
- What are the sources of energy-related carbon dioxide emissions by type of fuel for the United States and the world?, Energy Information Administration
- How much carbon dioxide (CO2) is produced per kilowatt-hour when generating electricity with fossil fuels?, EIA
- IARC Monographs
- Coal Mining-Related Respiratory Diseases, CDC