Fossil fuels are a non-renewable energy source formed over millions of years from the remains of plants and animals. When burned, they release energy. As of 2009, fossil fuels supplied about 85 percent of the world's energy demands. There are three main types of fossil fuels: coal, oil and natural gas. Coal is made from decomposed plants that have been subjected to intense heat and pressure. Oil and natural gas are formed from animal remains that have undergone the same treatment.

Oil is found below Earth's surface. Oil companies locate the oil by using seismic surveys to find probable oil fields. After oil has been found and permission has been approved by the government for drilling, a well is dug for a pump. Often, the pump is able to bring the oil to the surface. Sometimes, however, another hole must be drilled to pump steam into the oil field to lessen the density in order for it to be pumped out.

Natural gas is found in many of the same areas as oil. It's also pumped to the surface and travels through pipeline.

The three types of coal are anthracite, bituminous and lignite. Anthracite is the hardest and releases the most energy; lignite releases the least. Coal is recovered from beneath Earth's surface through mining. Mines are created from shafts dug into areas that have coal, and the coal is brought out from the mines. Another mining technique, strip mining, entails removing all of the soil and rock above the coal and then replacing the soil and rocks after the coal has been collected.

Once the fossil fuels are collected, they are transported to the power plant. The fossil fuels are then burned to heat water. When the fossil fuels' many hydrocarbon bonds are broken, they release large amounts of energy. The steam from the water then increases in pressure, forcing a turbine to spin. The turbine is used to rotate a magnet encased in a generator a high speeds. As the magnet spins, electrons are produced, and they power the electricity grid.