Which fossil fuel burns the cleanest of all?

Fossil fuels are non-renewable resources, they pollute the environment and contribute to climate change. 

Natural gas is one of the safest and cleanest fuels available. It emits less pollution than other fossil fuel sources. When natural gas is burned, it produces mostly carbon dioxide and water vapor -- the same substances emitted when humans exhale. Compared with some other fossil fuels, natural gas emits the least amount of carbon dioxide into the air when combusted.