On freezing local foods

17 Oct 2005

Got questions about the environment? Ask Umbra.

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.

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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

Yours is to wonder why, hers is to answer (or try). Please send Umbra any nagging question pertaining to the environment -- but first check out her FAQs!

The claims made in this column may not reflect the views of this magazine. Neither the magazine nor the author guarantees that any advice contained in this column is wise or safe. Please use this column at your own risk.

Umbra Fisk is Grist Research Associate II, Hardcover and Periodicals Unit, floors 2B-4B.

Comments: (2 comments)

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Numbers, numbers, numbers

Just to play around with the numbers a bit...

Google says that the drive from Fresno, CA to downtown Chicago is 2,209 miles long. Let's assume that you're right, Umbra, and that a 1,638 mile truck trip carrying 38,000 pounds of produce emits 6,000 pounds of CO2. Then a 2,209 mile trip emits about 8,000 pounds. That's a little over a pound of CO2 for every 5 pounds of produce carted from the Central Valley to Chicago.

Using your freezer for 9 months emits 332 pounds of CO2. I have no idea how much food you can pack in a freezer. But I'd be surprised if it were more than a couple hundred pounds. Let's be generous, and assume that we are freezing around 300 pounds of food.

Which means that shipping the veggies is...wait for it...about 5 times more carbon efficient than buying local and freezing.

Now, obviously, there's lots of uncertainty here. The actual trip can be longer (or shorter) than 2,209 miles. Food grown in California & Illinois may use different amounts of fossil fuel inputs (fertilizer, tractor diesel, pesticides, seeds, etc.). Cooking frozen foods can use more energy than fresh foods. Refrigerator trucks may get worse mileage than regular diesel vehicles. Ad nauseum.

But unless I'm mistaken, it looks like the numbers you present don't make much of a case for buying local. Sadly enough.

by Clark Williams-Derry at 9:41 PM on 17 Oct 2005

Eat fermented foods!

What about eating naturally fermented foods during the winter? All you need is an airtight glass or other container, fresh veggies or fruits, sometimes some salt and a little bit of time. No freezer required! And, it's a great way to get probiotics naturally!

p.s. You can also turn to nature's greatest gift: oxygen, and dry your foods, even meat if you eat it.

by jenniferbourdier at 6:40 AM on 18 Oct 2005

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Good Bite, and Good Luck