Fossil fuels are also known as “nonrenewable” fuels because the amount of time required to transform living tissue into coal, oil, or natural gas is tens of millions of years at a minimum. When we pull oil, coal, and natural gas from the earth and then burn it inside our vehicles, power plants, and factories, it is not being replaced. Because it is easy to envision a world with a growing population translating into a growing use of fossil fuels, we are left wondering: How much fossil fuel is still out there?
