In a meeting with environmentalists, Elizabeth Edwards talked about the importance of buying locally-produced foods:
“We’ve been moving back to ‘buy local,'” Mrs. Edwards said, outlining a trade policy that “acknowledges the carbon footprint” of transporting fruit.
“I live in North Carolina. I’ll probably never eat a tangerine again,” she said, speaking of a time when the fruit is reaches the price that it “needs” to be.
Being the kind and considerate person that I am, I don’t want the Edwards family to unnecessarily forego the pleasures of tangerine-eating. Therefore, I’ll try to help them out by calculating a vital economic and environmental parameter which shall be known as tangerines per gallon.
This is a very rough and preliminary analysis; tangerine experts and transportation experts are invited to chime in with more data.
Tangerines weigh about 1/4 pound each. As near as I can tell, the tangerines consumed in the U.S. come mostly from Florida, California, and Spain. There are four possible ways for them to get to market: truck, train, ship, and air.
According to the Association of American Railroads, trains move freight with an average efficiency of 423 ton-miles per gallon. The AAR also puts railroad fuel efficiency at 3-4 times that of trucking. I’ll use 400 tmpg for rail, and 100 tmpg for truck.
The Edwards residence is near Chapel Hill, NC. Let’s move some tangerines to his local store–first, from Florida. For this simplistic analysis, assume the shipment originates in La Belle, FL, which is 763 miles away from Chapel Hill–I’ll round it up to 800. So we have 8 gallons of fuel used per ton of tangerines, or 1000 tangerines per gallon.
If the shipment goes by rail, the TPG number will be much higher. The rail haul will consume only 2 gallons of fuel per ton, but I’ll assume 100 miles of truck shipment to get the fruit to and from the railheads, adding 1 more gallon. We’re now up to more than 2600 tangerines per gallon.
For West Coast tangerines, I calculate 266 TPG by truck and 941 TPG by rail. (This company is making a major push to get a higher proportion of the west-to-east fruit/vegetable traffic moved to the rails.)
But what if the Edwards tangerines come from Spain? We’re now talking ship or plane, and the fuel consumption estimates for these modes are harder to pin down. Combining estimates from several sources, I feel we can conservatively estimate 500 ton-miles per gallon for sea transportation and 7 tmpg for air freight.
According to an analysis from 1998, virtually all U.S. tangerine imports from Spain come by sea. So let’s ship the Edwards tangerines from Valencia and bring them in at Wilmington, NC. This should be about 5000 miles, consuming 10 gallons per ton, and haul them 160 miles to Chapel Hill, for another 2 gallons. Result: 666 tangerines per gallon.
If the tangerines do go by air–which seems unlikely–then fuel consumption from Valencia to Charlotte will be about 714 gallons, with another gallon for trucking to Chapel Hill. Result: 11 tangerines per gallon,.
So, it seems likely to me that the Edwards family is getting somewhere between 400 and 1000 tangerines per gallon. (Truck from Florida, blended truck/rail from West Coast, or ship from Spain.) Worst case–air freight from Spain–they’re still using less than a tenth of a gallon per tangerine consumed.
It’s interesting to compare these results with the “local” case. Suppose that a miracle occurred and tangerines began to grow in North Carolina. Even then, though, it’s doubtful that there would be tangerine groves adjacent to the Edwards place. If the tangerines are raised by a farmer 60 miles away, and he brings 500 lb of them to market in a pickup truck getting 20 mpg, then he is using 3 gallons of fuel each way–6 for the round trip–which equates to 333 tangerines per gallon. This is worse than truck from Florida, worse than rail from California, and worse than ship from Spain. Obviously, the numbers for the local alternative would improve–a lot–if we assume that the pickup truck is actually filled to capacity, or nearly so, but that’s not always easy to do under conditions of small-scale production and distribution.