One of the arguments most often heard, however, is about energy. And at a time of rising concern about climate change, the great distances that most of our food travels are a potent symbol of the system's profligacy and cost in greenhouse gases. For local-food activists, "food miles" have become a favored measure of environmental impact. Food activists in the US and especially in Western Europe have pushed to put the term on menus and grocery-store labels.
"[T]he typical item of food on an American's plate travels some fifteen hundred miles to get there," Michael Pollan writes in "The Omnivore's Dilemma," "and is frequently better traveled and more worldly than its eater."
But a gathering body of evidence suggests that local food can sometimes consume more energy -- and produce more greenhouse gases -- than food imported from great distances. Moving food by train or ship is quite efficient, pound for pound, and transportation can often be a relatively small part of the total energy "footprint" of food compared with growing, packaging, or, for that matter, cooking it. A head of lettuce grown in Vermont may have less of an energy impact than one shipped up from Chile. But grow that Vermont lettuce late in the season in a heated greenhouse and its energy impact leapfrogs the imported option. So while local food may have its benefits, helping with climate change is not always one of them.
Ezra Klein at the left leaning American Prospect busts out some interesting numbers:
two Carnegie Mellon researchers recently broke down the carbon footprint of foods, and their findings were a bit surprising. 83 percent of emissions came from the growth and production of the food itself. Only 11 percent came from transportation, and even then, only 4 percent came from the transportation between grower and seller (which is the part that eating local helps cut). Additionally, food shipped from far off may be better for the environment than food shipped within the country -- ocean travel is much more efficient than trucking.
Read that third sentence again, you emit more CO2 per pound of food driving home from the grocery store than is emitted moving that same food thousands of miles to the grocery store.
