DDB Paris is on a crazy creative roll right now. For Tropicana, it came up with the idea of illuminating a sign using only natural energy from oranges. Part of me went, "Wow, that's a lot of oranges for not a ton of payoff,"* but part of me also exclaimed, "I would now like a cool and refreshing orange beverage."
For those worried about food waste, the oranges were later all recuperated for use as biofuel or compost. That probably doesn't make you feel better as it could have all gone down your throat, smooth and sweet like fish of Gollum, but such is life.
*I actually still like this reaction because it shows you just how much of something you need to produce natural energy from foodstuffs, whose energy often has to be extracted in a lengthy process, in addition to you needing enormous amounts of it. Corn, for example, yields about 400 gallons of ethanol per acre per year. And extracting that requires more energy than the effort may be worth. (For now.)