In the United States, fossil fuels -- coal, oil and gas -- account for more than 85 percent of the energy consumed by Americans today, with oil and gas alone making up more than 60 percent (DOE, 2005; OFE, 2005). Less than half of this energy is extracted from domestic resources, however, making the United States dependent on foreign sources. As such, the restrictions of the availability of fossil fuels are due primarily to the fact that two-thirds of domestic oil is still in the ground. Furthermore, as demand for natural gas increases, easy to access supplies are becoming fewer, making it a more difficult and expensive resource to exploit, therefore, requiring US producers to explore and extract gas resources from "deeper, more complex and difficult-to-produce gas reservoirs" (DOE, 2005).
Coal, a fossil fuel like natural gas and petroleum, "is a sedimentary organic rock that contains more than 50 percent carbonaceous material by weight" and is made up of carbon, hydrogen, oxygen, nitrogen, and sulfur, with smaller amounts of other materials ranging from aluminum to zirconium (EIA, "Coal Production," 2004). Extracted by mining in three different regions of the United States: the Appalachian, Interior, and Western regions of the United States and shipped via truck, rail car or river barge to nearly every state in the country. There are typically two methods of mining coal: underground and surface. Underground methods of mining include drift, slope, and shaft mining, and actual mining methods include longwall and room and pillar mining. Surface-mining methods include area, contour, mountaintop removal, and auger mining (Kentucky Geological Survey, 2005).
Natural gas, on the other hand, is a relatively "clean" fuel source and is a combustible mixture of hydrocarbon gases composed mostly of methane, but may also include ethane, propane, butane and pentane. (Naturalgas.org, 2004). Found in reservoirs underneath the earth...