...A one-pound box of prewashed lettuce contains 80 calories...

...A one-pound box of prewashed lettuce contains 80 calories of food energy. According to Cornell ecologist David Pimentel, growing, chilling, washing, packaging, and transporting that box of organic salad to a plate on the East Coast takes more than 4,600 calories of fossil fuel energy, or 57 calories of fossil fuel for every calorie of food.