I certainly don't care if someone wants to eats locally grown food. If you prefer local food because it is fresher or tastier, great. If you enjoy shopping at the farmer's market, swell. Prefer local varieties? Happy hunting.
The "eat local" crowd does a fair amount of moralizing, though. They frequently suggest that we all ought to be buying locally-grown food. How far our food travels evidently has become a moral issue. By reducing our food-miles, the argument goes, we will reduce our fuel consumption.
But "food-miles" is the wrong metric. The correct metric is the amount of fuel used to transport a pound of food (or some other given amount). We don't care how far our tomato traveled; we care how much fuel it took to get it from there to here.
I'm skeptical that moving food even long distances has to use much fuel per pound. For example, an 18-wheeler can haul 30,000 pounds of tomatoes 1,500 miles from Florida to Texas at 5 mpg. That's a hundred pounds per gallon. At $4/gallon of diesel . . . I'll save you the arithmetic: that works out to just 4 cents to move one pound. You'll burn more fuel per pound making a separate trip to the grocery store for bread and milk. You'll probably burn more fuel per pound just backing your car out of the driveway to make a separate trip for bread and milk.
I realize it costs a lot more than 4 cents/pound to move those tomatoes from Florida to Texas. The trucker has to be paid, the trucking company gets its cut, etc. But we're worried about fuel. A pound of food can travel a long way on just a tiny amount of fuel.
The food-milers make another mistake, perhaps one worse than fixating on the wrong metric. They ignore the fact that lots of energy is used at every step of the soil-to-plate cycle. Fertilizer. Irrigation. Tilling. Harvesting. Storage. Processing. Transportation. Everyone knows that the recent surge in food prices was caused by the sustained surge in fuel prices (aggravated by the government's edict that we fuel our cars with food).
This is an important reason not to worry about fuel miles. It's actually very, very tricky to calculate the amount of energy used to get food from the ground to the market. Growing conditions matter a lot. Florida growers can grow 2 or 3 times or more tomatoes per acre than Texas growers. Local growers thus start at a huge energy disadvantage unless they are using radical farming methods that use no energy (also known as "subsistence farming"). It's quite possible that they cannot close the energy gap despite their advantage in transportation costs.
Because the cost of energy makes up such a large percentage of the cost of food, it makes no sense to minimize just one component of the energy cost. You'll be apt to maximize something else. Just look at the price. It may not be a perfect indicator of your food's energy cost, but it is the most reliable indicator you've got.
The handy thing about market prices is that if long-haul transportation costs are a large fraction of an item's cost, grocers have an incentive to find local sources. (At least they do if they expect prices to stay high; it may be too much trouble to switch sources for a temporary spike.)
Perhaps that's actually beginning to happen, as this story suggests:
Like all restaurants, Texadelphia sees food prices spike when gas prices do. Produce presents a big problem.
"Gas prices have caused everything food-wise to go up, but with produce in particular, because produce is something that is delivered daily," says Jeremy Wright, general manager of the Texadelphia location on 'the Drag' at the University of Texas campus.
So Texadelphia is finding a shorter route between the farm and its tables.
"We try to look and see if we can still get a good quality product, but be able to get it in more locally, or something that's closer, in order to be able to combat those rising gas prices," says Wright.
Produce the restaurant used to get from California is now coming from local suppliers or Mexico.
"It's actually coming in at about a third less cost coming in from Mexico," says Wright.
I'm not sure that switching from Californian to Mexican suppliers is what most locavores would consider "localizing" the food supply. (And doesn't the Mexican government heavily subsidize gasoline use?) I don't know whether grocers and restaurants are really switching en masse to local suppliers to save fuel. The nice thing about relying on the price as a guide is I don't have to worry about it. Texadelphia (and H.E.B.) will worry about it for me.
P.S. You can compare crop yields between states at the USDA site. (You can compare, e.g., Texas and Florida tomato yields -- Florida got 3.0 and 3.5 times the Texas yields in 2006 and 2007.)
A train can haul a ton of freight 423 miles on one gallon of diesel fuel, about a 3-to-1 fuel efficiency advantage over 18-wheelers . . .
This implies that an 18-wheeler can haul one ton 1,500 miles on 9 gallons, or over 200 pounds/gallon -- just 2 cents/
gallonpound at $4/gallon of diesel.