Exhaustible energy sources include all kinds of nonrenewable types of energy generation, such as coal, oil, nuclear or natural gas. As of June 2011, most of the energy used in the U.S. is produced from exhaustible sources, although all but five states in the U.S. have implemented programs that mandate a certain percentage of energy production come from inexhaustible sources at defined points in the future. Inexhaustible sources include wind, solar and water.
Coal is the most commonly used source of energy to create electricity in the U.S., accounting for nearly half of electrical production. Natural gas and nuclear power provide about 40 percent of the power produced in the U.S. Hydroelectric power generates just over 7 percent of power. Solar- and wind-production rates are rising as more solar-generating plants and wind farms evolve from the drawing board into production and implementation.
Although the fuels differ, most energy production using exhaustible fuels heat water to create steam, which turns the blades inside turbines to create electricity. The coal used in electrical production is finely crushed so that it burns hotter, heating the water more efficiently. The coal dust is sprayed into a boiler. Natural gas burns to create steam, as does the rarely used oil. Nuclear power uses uranium-235 pellets about an inch long, each of which is equivalent to a ton of coal. The pellets go into rods, which are sent to the reactor where they heat water, creating steam.
The side effects of burning these exhaustible energy sources to create power include air pollution, although new technology and regulations have reduced such harmful emissions as carbon monoxide, nitrogen oxides, sulfur dioxide and particulates. The cleanest fossil fuel used to create electricity is natural gas, and coal creates the most emissions. Carbon dioxide is a natural byproduct of burning nonrenewable resources and, while a naturally occurring compound, it is considered a major contributor to global warming. Carbon dioxide retains heat in the atmosphere and as more of these fuels burn, the atmospheric balance changes, changing the climate. In addition to climate change, mining for coal destroys habitat. And as petroleum resources dwindle, the prices increase for everything that relies on oil — including food, transportation, electricity and clothing.
Since the energy most of the world relies on to create electricity is not renewable at present, scientists are working on developing alternatives that imitate these fuels. Biofuels show promise. Ethanol is an additive for gasoline used in vehicles and, not only does it reduce the consumption of gas derived from oil, it also burns cleaner than gasoline. Biodiesel combines methanol with vegetable oil as a fuel for diesel engines. Scientists are also exploring algae as a means to generate oil even more efficiently than using plants.