There is a lot to like about local food. It tastes fresh, fosters community, supports regional farming and has a certain cachet that's drawing Americans to farmers' markets in droves. It's also putting more small farmers and their produce-filled box trucks on the nation's roads, which is raising questions about local food's carbon footprint and the significance of a metric at the heart of the farm-to-table movement: the food mile.
At its most basic, a food mile is simply the distance food travels from where it is grown to where it is purchased. The lower the food miles, the shorter the trip, the smaller the transportation-related greenhouse gas emissions, or so the thinking went. Then ten years ago, an Iowa-based sustainable agriculture policy institute called the Leopold Center started factoring the mode of transportation into the food mile equation. Whether food is transported by container ship, train, diesel truck or gasoline pickup has a huge impact on the relative efficiency of its food mileage: an Idaho potato bound for Boston by train, for example, has a lower carbon footprint than a spud driven from Maine in a diesel truck.
The latest challenge for the food-mile metric, and farmers' markets around the country - which frequently place food-mile limits on their vendors - is another matter of transportation efficiency: volume, or more accurately, its lack. When individual farmers drive trucks to market, they rarely have enough merchandise to fill the available cargo space. This is the trucking equivalent of a single-occupancy vehicle, and it’s entirely invisible to the food-mile metric, which would give the same rating to a lone carrot transported 50 miles as it would a truck-load of them.
"What matters in terms of fossil fuel consumption is not how many miles the food has traveled, but how many gallons of fuel are in each pound of food," says Bob Comis, the head of Stony Brook Farm in Schoharie, New York. "The concept of food miles is incomplete. We need a more revealing and accurate measure like 'pound-gallons.'" Comis believes that pound-gallons, which could be calculated to include both production and transportation externalities, would not only allow consumers to make a more informed decision about the environmental costs of what they buy, but also encourage farmers to increase the efficiency of their transportation system.
Comis envisions a local-food future where farmers' markets remove their food-mile limits in favor of pound-gallon caps and encourage vendors to post figures that reflect the true environmental cost of an item. He also predicts that truck-pooling and purveyor systems will catch on, allowing a number of small farms from the same region to share vehicle space, fuel and transportation headaches. "That would definitely decrease the environmental impacts of truck transport and drastically reduce the cost of doing business," Comis says.
B.R. Shute, a farmer from Tivoli, New York, who spends more than 12 hours commuting to and from New York City each week, has already been involved in some informal truck pools. "We always try to make sure that the truck is filled," he says. "It’s good business. It’s better for everyone involved."
Whether truck pools purveyors and pound gallons will move past the world of bright ideas and into the realm of real policy has yet to be seen. There are benefits to sticking with an already established and easily understood metric like food miles. “People get it, and it gets some of the larger community-focused points across pretty well,” Comis concedes. "'Pound gallons' is a terrible phrase for the ears, even if it’s moving the conversation about local agriculture in the right direction."
Photo credit: Jonathan Ernst/Reuters