Most people who follow renewable energy have heard of biogas by now, yet the origins and uses of biogas remain mysterious to many. Biogas is unusual in that its use predates the use of fossil fuels. In fact, it is older than fossil fuels completely. The microorganisms that create biogas are among the oldest life forms on earth, over three billion years older than the plants and animals that became today's fossil fuels. Biogas not only provides excellent, clean-burning energy that can replace fossil fuels in the future, but in many places it already is.