For example, your model would indicate that if rail tracks ran the 60 miles from the local farm to my doorstep that would be the most efficient transportation mode. A commodity like this would move in a boxcar. The load would cube out without reaching the weight limit. The lading weight may only be ~60,000 lbs. The tare weight on a 50’ boxcar is approximately 65,000 lbs. Common sense should tell you it wouldn’t be efficient to move 0.27 lb of steel railcar for each 0.25 lb tangerine. Not to mention I don’t need 240,000 tangerines. You’re also ignoring a bunch of other things such as all of the energy costs associated with building and supporting a transportation network.

1) What about transportation “to” the overseas seaport?
2) Is the assumption of high-efficiency trucking valid? Probably it is most valid for large farms that can benefit from big trucks.

What I get out of your helpful analysis is this:

1) Carbon-emission-wise, don’t worry too much about the efficient parts of the supply chain.
2) Do worry about air freight. (perhaps uncommon)
3) Do worry about low-efficiency trucking.
4) Usage level of low-efficiency trucking is probably, roughly proportional to
a) how much we rely on small farms and
b) how far away small farms are from high-efficiency transportation hubs.

I am not sure if we should be too concerned about low-efficiency trucking. In the long run, we will use it less and less — note that even small farms are close to other small farms, and these folks have incentive to aggregate their production in local transportation hubs that can use high-efficiency trucking.

In my case, I understand that buying local is becoming quite popular. The reasons are probably two:

1) Some people probably do it because they value local farmers more than remote farmers. I don’t subscribe to that philosophy. As commenters have said, remote farmers are just as deserving.
2) Many people do it because they believe they are reducing their carbon footprint. OK, a few issues here.
a) First, I generally feel that a carbon tax would do the trick here.
b) But, buying local is not just “an inefficient approximation” to a carbon tax. It is about changing people’s value system in a way that will change their demand curve. If people get some moral value out of buying local (or conserving home energy, or whatever) then the resulting consumption switch can be an efficient result. The value system of people can change, and when that happens, it can change the equilibrium.
c) I agree that people who buy local to reduce CO2 had better be sure they are actually doing that. I’ve seen some mixed evidence here, but (i) I think the environmentalist community is sufficiently self-critical to “get the message” once definitive research comes out in either way, (ii) I’m sure some food gets freighted by air, and it would make sense to target that per David Foster’s great analysis; (iii) Efficiency happens with economies of scale. As local-farmer demand increases, the local-food supply chain will increase in efficiency. (iv) It is excellent to point these things out so people can be mindful of them. For example, one could imagine a food-transportation business, targeted at locally-grown foods, which emphasizes high CO2 efficiency (hybrids, electric vehicles, railways). (v) Note that the tangerines in David Foster’s example are not grown at the seaport, and they are not grown at the train station. Presumably the very beginning of the supply chain, which moves foods to the high-efficiency transportation hubs, is CO2-inefficient. That is left out of David’s otherwise excellent analysis.

It must have been a long time since you’ve been out to a farm because , you know, they do grow more than one crop at a time.

The tangerine/gallon argument leaves out lots of stuff: carbon footprint of the manufacturing process, of the local cost to transport the tangerines to the train/truck/airport stations, carbon footprint of the workers getting to the train/truck/airport stations. So I’ve left out lots of stuff, too.

So I say to you chill.

Where I live the local grocery store is just about as far as the local farms. So when I go to the local farm to get tangerines rather than to the supermarket there is 0 (zero) gallons of additional fuel used. I get an infinity of tangerines per gallon by buying from a local producer. (I also support local neighborhoods and communities and get fresher produce besides.)

As far as I am concerned your argument is full of soot!

I showed that the carbon footprint from a normal day of driving was comparable to that required to produce a couple of cheeseburgers.

Read the whole thing at voluntaryXchange.

You may have heard that John Edwards’s wife recently swore off eating tangerines because she is worried about the carbon footprint of transporting food long distances. David Foster at Chicago Boyz crunches the numbers and reports that tangerines impor…

Couldn’t we just subcontract out to a a factory in Indonesia? This way, the Indonesians get trained in the important art of contributing to the world economy and cash in on carbon footprints before they become yesterday’s fad.

Did you see where a neighbor of eco-shrew Laurie David called her a Mrs. Carbon Sasquatch? It takes some serious bucks to achieve that distinction, Mitch. Maybe Verity can whip you up some Carbon Sasquatch house slippers.

Or some way of making a carbon footprint on a bathmat grow larger! Personally, I favour profligacy.

I bet they’d sell very well, at least in certain venues.

Tee hee.