Fossil fuels are essentially energy derived from plants and animals that died millions of years ago. Currently fossil fuels account for about 90% of the world energy consumption. Our economies and even our social life have become quite dependent on fossil fuels. What happens if we run out? Fire! Come on, I want some fire! Fire! Come on, I want some fire! Oh, jeez, well, okay, we may not go back to the stone age, but can you imagine?