Energy is the capacity to do work. Power is the rate of doing work. The huge blackout of 2003 reminds us of how dependent we are on energy.
Worldwide, about 86 percent of all commercial energy is generated by fossil fuels, about 40 percent coming from petroleum. Next are coal, with 23.3 percent, and natural gas (methane), with 22.5 percent. Coal supplies will last several more centuries at present rates of usage, but it appears that the fossil fuel age will have been a rather short episode in the total history of humans. Nuclear power provides about 6.5 percent of all commercial energy, but about 20 percent of the electricity in the United States.
Energy is essential for most activities of modern society. Its use generally correlates with standard of living, but there are striking differences between energy use per capita in countries with relatively equal standards of living. The United States, for instance, consumes nearly twice as much energy per person as does Switzerland, which is higher in many categories that measure quality of life. This difference is based partly on level of industrialization and partly on policies, attitudes, and traditions in the United States that encourage extravagant or wasteful energy use.
The largest share of energy used in the United States is for industry. Transportation consumes about 27 percent of the U.S. energy supply, almost entirely from petroleum. One measure of energy efficiency is the amount used per unit of economic output. While efficiency has increased in most areas in recent years, Europe still uses less than half as much energy per unit of GDP as the former Soviet Union.
The environmental damage caused by mining, shipping, processing, and using fossil fuels may necessitate cutting back on our use of these energy sources. Coal is a dirty and dangerous fuel, at least as we currently obtain and use it. Some new coal treatment methods remove contaminants, reduce emissions, and make its use more efficient (so less will be used). Coal combustion is a major source of acid precipitation that is suspected of being a significant cause of environmental damage in many areas. We now recognize that CO2 buildup in the atmosphere has the potential to trap heat and raise the earth's temperature to catastrophic levels.
Natural gas is a convenient, clean-burning fuel that produces less CO2 per BTU than coal. Russia and the Middle East have nearly two-thirds of the world's proven supply of gas. Large, easily accessible gas deposits are found in coal seams in the western United States, but the environmental and social costs of extracting this fuel are high.
Nuclear energy offers an alternative to many of the environmental and social costs of fossil fuels, but it introduces serious problems of its own. In the 1950s, there was great hope that these problems would be overcome and that nuclear power plants would provide energy "too cheap to meter." Recently, however, much of that optimism has been waning. No new reactors have been started in the United States since 1975. Many countries are closing down existing nuclear power plants, and a growing number have pledged to remain or become "nuclear-free."
The greatest worry about nuclear power is the danger of accidents that release hazardous radioactive materials into the environment. Several accidents, most notably the "meltdown" at the Chernobyl plant in the Soviet Ukraine in 1986, have convinced many people that this technology is too risky to pursue.
Other major worries about nuclear power include where to put the waste products of the nuclear fuel cycle and how to ensure that it will remain safely contained for the thousands of years required for "decay" of the radioisotopes to nonhazardous levels. Yucca Mountain, Nevada, was chosen for a high-level waste repository, but many experts believe that burying these toxic residues in nonretrievable storage is a mistake.
None of our current major energy sources appear to offer security in terms of stable supply or environmental considerations. Neither coal nor nuclear power is a good long-term energy source with our present level of technology. We urgently need to develop alternative sources of sustainable energy.
