Sunlight:  The light that comes to the earth from the sun is pure energy. The sun is the original energy source. Nearly all other sources of energy originally got their energy from the sun. Organic matter, like plants, convert solar energy into leaves, flowers and fruits. Animals, which eat organic matter, convert the energy into body mass. When animals die, their energy is decomposed and over extensive time, becomes stored as oil, coal or natural gas.

 Food: Food is the source of energy used by people. Food that we eat is digested, and the stored energy is used by the body to keep the heart beating, the blood pumping, and the body growing. When a body has "low blood sugar," the body needs to eat and process more energy, so we can continue working, playing and growing.

Organic Oils: Vegetable oil and animal oil have played an important role in human history. Vegetable oils, like olive oil, corn oil or safflower oil, are often used in cooking. Jojoba oil (from the jojoba bean) is used in cooking or lubricating, as well as in lotions and soaps. Animal oil, like that from whales, seals and livestock, was used in the past for lighting lamps as well as for waterproofing.

Wood: Wood comes from trees, which are, of course, plants. The plants got their energy from the sun. When trees are cut down and burned, they release their energy in the form of heat. Many homes are heated with wood-burning stoves.

Fossil Fuels: The following three energy sources come from prehistoric fossils. Like the methods described above, ancient plants absorbed the energy from the sun and converted it into more plants. Ancient animals, like dinosaurs, ate the plants. When the plants and animals died, their remains collected under mountains of earth and, over millions of years, they decomposed into a source of fuel. The remains of these plants and animals are what we refer to as fossil fuels.

 Coal: Coal is burned to heat homes and run electrical machinery. About 20 percent of the energy we use comes from coal.

Oil: Other petroleum products similar to motor oil are burned to fuel motor vehicles and heat homes. About 45 percent of energy used comes from oil.

Natural Gas: Natural gas is used to heat the homes of many people. About 25 percent of the energy we use comes from natural gas. 

Other Energy Sources

Water: Water is not an energy source, but water is used to generate energy. Water falling downhill is used to run turbines, which generate electricity. This is called hydroelectric power. About 5 percent of the world’s power is now produced by hydroelectric dams. A similar type of energy comes from geothermal energy. Pockets of boiling water under the earth’s surface send steam to the surface of the earth. This hot water also can be used to generate electricity. Dams can impede the movement of fish up and down river to reach spawning grounds or for other migratory purposes.

 Wind: Winds that blow can be used to turn windmills, which generate electricity. Windmills have been used for centuries in some parts of the world, like Holland. Windmills are also used in the United States.

 Electricity: An electrical storm contains a great deal of natural electrical energy. Benjamin Franklin first proved that lightning was electricity in 1752. His discovery helped scientists learn how to harness electricity and how to generate electricity from other methods. The electricity we use today was created by other sources, not by the energy released by lightning.

 Nuclear Power:  Nuclear power comes from the radioactive ore uranium. It produces far more power per ton than any other energy source. Nuclear power does not contribute to air pollution. However, radioactive waste is hazardous to living things. Exposure to radioactive materials can result in mutations, illness or death. The drawback to using nuclear power is finding a safe place to dispose of the nuclear waste. About 6 percent of the energy used in the world comes from nuclear power.

Refuse-derived fuel: Now, we are able to extract energy from garbage! Garbage is burned in a waste-to-energy facility. As it burns, water pipes are heated. This hot water is used to generate electricity. Most waste-to-energy facilities produce enough energy to run the plant and supply additional power to the community. This is a small but growing source of energy.

Chemical energy: Batteries create energy through chemical reactions. When different chemicals react with one another, energy is released. Eventually the reaction stops, and the battery must be replaced. Batteries are used in motor vehicles and many smaller appliances, like clocks, hearing aids and toys.

Credit: The National Wildlife Federation's Animal Tracks Activity Guide for Educators. Copyright © National Wildlife Federation 1995.