Some reliable source of energy is very important for many industrial countries now days. These energies are utilized for cooking, heating, manufacturing and transport purposes. The energy can be commonly classified as renewable or non-renewable. All over eighty-five percentage of the energy used in the globe is from non-renewable sources. While often bundled up together, fossil fuels are made up of coal, oil and natural gas. All can provide energy but at a different cost – both financial and environmental. Given that natural gas is available only as part of fixed and existing reserves, it is by definition considered a fossil fuel. Nonrenewable energy resources, like coal, nuclear, oil, and natural gas, are available in limited supplies. This is usually due to the long time it takes for them to be replenished. Renewable resources are replenished naturally and over relatively short periods of time.