July 25, 2007

Is Local Food Greener?

Drake Bennett has a fascinating piece in the Boston Globe today on eating locally. Contrary to the conventional wisdom, he argues, eating locally doesn't always save energy and lower greenhouse emissions: "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." Okay, maybe that's true, but some of this sounds fishy:
Judged by unit of weight, ship and rail transport in particular are highly energy efficient. Financial considerations force shippers to pack as much as they can into their cargo containers, whether they're being carried by ship, rail, or truck, and to ensure that they rarely make a return trip empty.

And because of their size, container ships and trains enjoy impressive economies of scale. The marginal extra energy it takes to transport a single bunch of bananas packed in with 60,000 tons of other cargo on a container ship is more than an order of magnitude less than that required to move them with a couple hundred pounds of cargo in a car or small truck.
But how often do containers actually return non-empty? That doesn't always seem possible—when food's being shipped to a city, it's not like there's anything to bring back, is there? And surely when you transport bananas on a container ship, you have to refrigerate them, which in turn uses more energy per banana than a short car trip might. I guess the moral is that this stuff is complicated, and the best way to reduce "food miles" would be a labeling system (which Bennett discusses) or—it's turning into a refrain!—a carbon tax.

Of course, as Bill McKibben notes in his recent book, Deep Economy, there are plenty of other reasons why people would want to eat locally, apart from the potential energy savings: the money stays in the community, the food tends to be fresher and hence healthier (more nutrients!), you're not subsidizing massive agribusinesses, which are always and everywhere evil, and—supposedly—it tastes better. Either way, Bennett's piece was interesting.
-- Brad Plumer 9:09 PM || ||