Oil, natural gas, coal and uranium – the most common fuels in the world – are considered to be non-renewable, due to the eons it took to create them and mankind’s inability to synthesize similar fuels readily. All but uranium are called “fossil fuels” because of their genesis in decaying plant and animal matter. Together, oil, natural gas and coal account for about 85 percent of the world’s energy supply, a share that has changed little over recent decades. Nuclear power now provides 6.3 percent, a six-fold increase from 1973 levels.1
In 2005, petroleum products (including oils, gasoline and other liquid fuels, but not natural gas) provided 40.6 percent of the 100.3 quadrillion British Thermal Units (Btu), or “quads,” consumed in the U.S. Coal and natural gas each provided more than 22 percent of the Btu consumed nationwide; nuclear energy provided 8 percent; and hydropower and biomass provided less than 3 percent each.2
The Texas oil and gas industry has bolstered the state economy for a century. Oil and gas deposits are widely distributed throughout the state and offshore. Deposits of coal and uranium (which, when processed, produces nuclear power) are found in Texas, but not in quantities comparable to those of oil and gas. Combined, these fuels produce all but a small fraction of the state’s electricity; gasoline and diesel refined from oil likewise account for all but a small fraction of the state’s transportation fuels.
Oil, natural gas, coal and liquefied petroleum gases (LPGs) are called “hydrocarbons” because of their chemical structure, which is based on hydrogen and carbon atoms. Under heat and pressure, these elements bond and create chains of molecules in almost infinite combinations, each with unique properties. For example, the long “carbon chain” molecules that create crude oil can be heated and “cracked” in the refining process. (The longer the chain, the broader the variety of refined products it can produce.) The result is a variety of shorter molecule chains that give us waxes, liquids and gases such as paraffin, diesel, gasoline, kerosene, propane, butane and methane (natural gas), among others.
Petroleum deposits, for the most part, formed at the bottom of ancient seabeds to become semi-solid, liquid and gaseous compounds. These deposits are now found as deep as tens of thousands of feet below the earth’s surface. As such, petroleum deposits generally can be extracted economically only by drilling. The exception is tar or oil sands, found in Canada and elsewhere in the world, which are near the surface and can be mined.3
Today, petroleum products and their derivatives supply almost all of the world’s transportation fuels, chemicals and plastics.
Coal is a combustible rock of varying hardness, moisture and mineral content. Coal deposits, called “seams,” must be excavated; commercial deposits generally are found either just below the surface or underground at depths up to 1,000 feet, although mine depths of more than 2,000 feet are not uncommon.4
Coal was widely used first as jewelry, then as fuel, by the Chinese six millennia ago and by the Romans in Britain four millennia later.5Today, coal is the world’s most common heating fuel. China, with the third-largest proven reserves in the world, is unique among developing countries in that coal is its preferred fuel for both heating and home cooking.6
Uranium is a mineral found throughout the world. Commercial concentrations of uranium ore are fairly widespread, including several in South Texas.
In its natural state, uranium is an ore that must be extracted via underground mining, open-pit mining or in-situ leach (ISL) mining. Open-pit and underground mining mechanically remove the uranium ore from on or below ground, break it up and send it to a mill where the uranium is removed.
ISL mining, also called solution mining, pumps a leach solution (commonly sulfuric acid or a weak alkaline solution, depending on the type of rock) through the ground to separate uranium from the source rock, and then extracts the uranium-bearing fluid from the formation. ISLcauses little surface disturbance or waste rock. The source rock must be permeable to the leach solution, however, and should be located in a geologic formation that prevents groundwater contamination.