"Clean." "Green." What do those words mean? When President Obama talks about "clean energy," some people think of "clean coal" and low-carbon nuclear power, while others envision shiny solar panels and wind turbines. And when politicians tout "green jobs," they might just as easily be talking about employment at General Motors as at Greenpeace. "Clean" and "green" are wide open to interpretation and misappropriation; that's why they're so often mentioned in quotation marks. Not so for renewable energy, however.
Somehow, people across the entire enviro-political spectrum seem to have reached a tacit, near-unanimous agreement about what renewable means: It's an energy category that includes solar, wind, water, biomass, and geothermal power. As the US Energy Department explains it to kids: "Renewable energy comes from things that won't run out -- wind, water, sunlight, plants, and more. These are things we can reuse over and over again. … Non-renewable energy comes from things that will run out one day -- oil, coal, natural gas, and uranium."
Renewable energy sounds so much more natural and believable than a perpetual-motion machine, but there's one big problem: Unless you're planning to live without electricity and motorized transportation, you need more than just wind, water, sunlight, and plants for energy. You need raw materials, real estate, and other things that will run out one day. You need stuff that has to be mined, drilled, transported, and bulldozed -- not simply harvested or farmed. You need non-renewable resources: