Friday, August 20, 2010

How Important is Eating Locally?

I was interested to read Stephen Budiansky's Op-Ed piece , Math Lessons for Locavores in the New York Times today. Budiansky posits that when the true carbon costs of shipping produce across or between continents is accurately analyzed, the impact is minimal, especially in relation to the other ways in which our food production systems use energy.

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.

Budianski has a blog, Liberal Curmudgeon, on which he posts this chart, taken from the University of Michigan's Center for Sustainable Systems.

Breakdown of Energy Consumption in U.S. Food System

What do you think? Does this chart demonstrate that the energy saved by growing and eating locally more often is so small as to be unimportant? Why or why not?

1 comment:

  1. Each lb of lettuce provides about 75 calories. It takes 20 lbs of lettuce to provide 1500 calories so lets assume that 20 lbs of lettuce feeds one person for one day. If they were shipped by trucks, 20 lbs of lettuce would incur an extra 6,000 calories of transportation cost, which is about enough to grow 1 lb of lettuce. This means that we're talking about feeding 20 people with CA lettuce and 21 people with, say, VT lettuce with the same energy cost. Feeding 5% more people seems like a significant thing.

    Of course there are many problems with this calculation, with the first being that lettuce is very inefficient. I'd imagine this would work out very differently with grains and meat.