Why are fossil fuels rich in energy?

Fossil fuels are important because they are substances, which were created several hundred million years ago through the decomposition of prehistoric organisms and plants. Machines such as televisions, cars and computers we take for granted in our daily lives, need energy to run. The energy used to power these energy things come from fossil fuels. Fossil fuels can be categorised into three types; petroleum, natural gas and coal. Examples of petroleum fuels include gasoline, kerosene and diesel fuels. Because of petroleum's importance to our energy needs, infrastructure necessary to extract oil from the ground and refine it is already in place, and this oil is relatively economical source of energy. One of the major forms of natural gas is propane, which is also useful in a number of applications, including transportation