The Omnivore's Dilemma: A Natural History of Four Meals

by Michael Pollan

The plant washes and packs 2.5 million pounds of lettuce a week; when you think just how many baby leaves it takes to make a pound, that represents a truly stupendous amount of lettuce. It also represents a truly stupendous amount of energy: to run the machines and chill the building, not to mention to transport all that salad to supermarkets across the country in refrigerated trucks and to manufacture the plastic containers it’s packed in. 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 energy for every calorie of food. (These figures would be about 4 percent higher if the salad were grown conventionally.)