Math Lessons for Locavores

But the local food movement now threatens to devolve into another one of those self-indulgent — and self-defeating — do-gooder dogmas. Arbitrary rules, without any real scientific basis, are repeated as gospel by “locavores,” celebrity chefs and mainstream environmental organizations. Words like “sustainability” and “food-miles” are thrown around without any clear understanding of the larger picture of energy and land use. One popular and oft-repeated statistic is that it takes 36 (sometimes it’s 97) calories of fossil fuel energy to bring one calorie of iceberg lettuce from California to the East Coast. It is also an almost complete misrepresentation of reality, as those numbers reflect the entire energy cost of producing lettuce from seed to dinner table, not just transportation. Studies have shown that whether it’s grown in California or Maine, or whether it’s organic or conventional, about 5,000 calories of energy go into one pound of lettuce. Given how efficient trains and tractor-trailers are, shipping a head of lettuce across the country actually adds next to nothing to the total energy bill. It takes about a tablespoon of diesel fuel to move one pound of freight 3,000 miles by rail; that works out to about 100 calories of energy. If it goes by truck, it’s about 300 calories, still a negligible amount in the overall picture. (For those checking the calculations at home, these are “large calories,” or kilocalories, the units used for food value.) Overall, transportation accounts for about 14 percent of the total energy consumed by the American food system. Other favorite targets of sustainability advocates include the fertilizers and chemicals used in modern farming. But their share of the food system’s energy use is even lower, about 8 percent. The real energy hog, it turns out, is not industrial agriculture at all, but you and me. Home preparation and storage account for 32 percent of all energy use in our food system, the largest component by far. Indeed, households make up for 22 percent of all the energy expenditures in the United States. Agriculture, on the other hand, accounts for just 2 percent of our nation’s energy usage; that energy is mainly devoted to running farm machinery and manufacturing fertilizer...more