Dear Umbra,

I am lucky enough to live across the street from a farmers’ market, and I shop there all summer. But when summer’s done, the market closes and I am left to buy produce from California. Would it be better for me to buy a small freezer and freeze farmers’ market veggies for winter, or to forgo the freezer and buy from the grocery store? Which is worse: long-distance transportation or the juice used by a freezer?

Anne McKibbin
Chicago, Ill.

Dearest Anne,

Don’t be so sure your produce comes from California. It could come from South America. One of my favorite studies [PDF] of the transport difference between local and non-local foods found that in 1998, more than 21 percent of the produce coming in to Chicago’s terminal market was from outside the United States. For the purpose of your question, though, we’ll just go with Cali, and reasonably assume that Chilean imports are worse.

It’s a long way to Chicago.

OK, let’s start crunching numbers. If you got a 10-cubic-foot Energy Star chest freezer, it would run you about 285 kilowatt-hours per year. Energy Star, on its handy page of facts and figures for persuading people that conservation is more than a personal virtue, calculates 1.55 pounds of carbon dioxide per kWh. We get to knock off a few months — you’ll plug in the freezer in July, and by April, the food left will fit into your regular refrigerator/freezer — so figure nine months of operation, which is 214 kWh. That’s 332 pounds of CO2 to freeze your meat and veggies. (I hope you’re buying meat at the farmers’ market, if you eat it.)

Now, diesel fuel emits 22 pounds of CO2 per gallon, if I correctly understand the Energy Information Administration’s emissions coefficients. A diesel truck would need to burn only 15 gallons of fuel to match your chest freezer’s carbon burden, which, with an average of 6 miles per gallon, is about 90 miles of travel. (That will get you veggies from South Bend — yum!) According to another part of the study I mentioned at the start, conventional produce in Iowa traveled an average of 1,638 miles, as opposed to 38 miles for local produce. If a diesel truck travels 1,638 miles, it will produce around 6,000 pounds of CO2. More than your freezer.

There are a lot of other factors at play, of course: your household’s food consumption, the actual food-miles of your groceries, the 38,000 pounds of produce in the average long-haul diesel truck, economies of scale, manufacturing, and so forth. The whole thing may be a wash. But when you consider the more than 20 percent of produce coming from outside the U.S. and the benefits of supporting local growers, I say, chest freezer ho!

One last thing: Am I an idiot to think you may be able to buy from a local grower during the winter in Illinois? Some farm with a winter Community Supported Agriculture program? Ask around, on my idiotic behalf.

Frostily,
Umbra