FOSSIL FUELS ARE A WIDELY USED BUT LIMITED ENERGY SOURCE

0ur fossil fuel supplies were created hundreds of millions of years ago when ancient plants and animals died and became buried in swamps, lakes, and seabeds. These supplies cannot be replaced after we have used them up, which is why they are often referred to as nonrenewable energy sources. Estimates vary on the worlds supply of fossil fuels, which include coal, petroleum, and natural gas. Even the most conservative estimates, however, show that, at present consumption rates, recoverable petroleum reserves will be depleted within 100 years and recoverable natural gas reserves within 150 years. As depletion approaches, these valuable commodities will become too costly. Coal reserves, on the other hand, are more abundant and may last another 300 years. Worldwide, nearly all our present energy needs are met by fossil fuels—38 percent from petroleum, about 30 percent from coal, and about 20 percent from natural gas. 

Fossil fuel deposits are not distributed evenly throughout the world. For instance, 65 percent of the world s recoverable petroleum deposits are in the Middle East, along with 34 percent of recoverable natural gas deposits. North America is relatively poor in petroleum and natural gas but has a bit more than one-fourth of the world s supply of coal. 

Typical molecular structures of coal, petroleum, and natural gas. 

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Fossil Fuels Are a Widely Used but Limited Energy Source warmed by the sun is because it is so big. Look at the lower right corner of the chapter-opening photograph, and you ll... 

Fossil Fuels Are a Widely Used but Limited Energy Source... 

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