People use energy for heat, lighting, and power in homes, business, factories, and agriculture, and for transportation. About 85 percent of the world's energy currently comes from fossil fuels (including petroleum, natural gas, and coal) or from using fossil fuels to generate other types of energy such as electricity.
The global stores of these fuels — especially petroleum — may have peaked and are expected to decline and to become much more difficult, expensive, and environmentally damaging to extract. Relying on resources from politically and socially volatile parts of the world threatens our security. Moreover, when these fuels burn they release carbon dioxide, a greenhouse gas linked to global climate change.
Dwindling resources and climate change are two compelling reasons why our society must move beyond fossil fuels to more sustainable sources. "Renewable energy" sources are constantly replenished and, thus, inherently more sustainable. These sources include solar, wind, water, biomass (wood and other plant materials), and geothermal energy.
In the past, people relied almost exclusively on renewable sources of energy: solar energy for lighting, wood for cooking and heating, wind for pumping water or propelling ships, animals for land transportation, and so on. As the use of fossil fuels increased, the U.S. and other countries relied less on these resources. Today, people are finding innovative ways to once again use these renewable resources to meet energy needs.
The majority of renewable energy today is used to produce electricity. In 2008, about 9 percent of U.S. electricity was generated from renewable sources. While most of that power came from hydroelectric facilities, the amount of electricity generated from wind and solar resources has been increasing dramatically every year.
Any energy source has economic and environmental consequences, meaning that energy efficiency — finding ways to use less energy — is the first step toward sustainability. Renewable energy power plants are generally more expensive to build and operate than coal or natural gas plants, and can affect the natural landscape and native species. Large-scale solar arrays may compromise open spaces. Dams for hydroelectric generation have serious environmental consequences downstream. "Renewable" fuels such as ethanol currently require more energy input to grow than they produce, and take land out of food production.
Nuclear energy is probably the most controversial alternative to fossil fuels. Nuclear power emits less pollution than coal-fired plants. When properly operated, nuclear power plants create little or no carbon dioxide or particulate air pollution. They are also relatively efficient, expending a small amount of resources compared to the power they generate.
However, nuclear plants produce radioactive waste that is extremely dangerous and that must be carefully stored for thousands of years. The risk of a devastating nuclear accident (like Chernobyl) is always a possibility.
Some argue that the existence of nuclear power plants provides an infrastructure for mining and processing uranium and plutonium — energy sources for both nuclear power and nuclear weapons — and the possibility that these materials will get into the wrong hands (Nuclear Energy Information Service). Indeed, more than half of all countries with nuclear power plants also have nuclear weapons, and the country with the most nuclear power plants — the U.S. — also has the most nuclear weapons (Time for Change).
Despite the disadvantages, many countries are investing in new nuclear power plants. Currently, there are about 436 nuclear power plants operating in 31 countries, with 42 new plants under construction (European Nuclear Society).
Energy use is a significant part of schools' operations, and of schools' impacts on the environment. Public school systems spend more than $8 billion annually on energy, their highest expenditure after personnel. Fortunately, the substantial savings that can be realized through energy efficiency create an important incentive for building green and for retrofitting. Even before undertaking such projects, schools can reduce energy use by simpler behavioral changes. The U.S. Department of Energy estimates that actions such as turning off computers, copiers, and lights when not in use, converting to low-flow and waterless plumbing fixtures, and replacing soft drink machines and other energy-intensive items could reduce a school's total energy use by as much as 33 percent (Department of Energy).
The greatest use of energy associated with many schools is the fuel expended in transporting students and staff to and from campus. Everything from locating schools closer to public transportation to encouraging walking and bicycling to eliminating the idling of vehicles dropping off or picking up students can substantially reduce the energy use for which the school is responsible.
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