10 surprisingly easy sources of alternative energy

Sure, you've heard of wind and solar power, biofuels, hydroelectric, tidal and wave power, but Mother Nature provides an endless bounty of alternative energy sources beyond those that we use today. Clean, green energy is all around us in the natural world, and scientists have only begun to answer the question of how to tap it. Here's a list of 10 practical sources of alternative energy you've probably never heard of. (Text: Bryan Nelson)