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Help us eat for the winter!
May 31, 2009 5:36 AM   Subscribe

We want to freeze vegetables for the winter. Here's the trick: we don't want to use a refrigerator.

So, after a summer of vegetable gardening, we're going to have a ton of produce that we'd like to put up. Not much space in the kitchen, so we're trying to think of "off the grid" ways of freezing vegetables until the winter. Specifically, ways that don't use electricity... Maybe this is a little bit crazy? Here are some of the things we've come up with so far....

- Bury the ice-box -- basically, digging a small hole in the ground, lining it with wood spacers, and creating a mini-icebox that we can access through a trap door. In the summer we'd have to keep it stocked with ice; in the winter it should keep on its own. Downside: Drainage? If we're OK with ice melting, is this going to be a huge mud problem, or will it drain effectively on its own? What are good ways to line / seal something like this?

- Freezing with liquid nitrogen - this gets around the initial "no-fridge" policy, but space is still an issue. (one of my roommates is REALLY excited about this idea). Plus side: no need to buy ice! But is this going to be a logistical nightmare? Downside: Storage is still an issue, obviously.

- Chest freezer in the backyard and just turning it off in December (when stuff gets cold enough to keep on its own). We could also do this in the basement (though it's not technically our space). Upside: No problems with insulation. Downside: It's a refrigerator.

I'm excited about number 1 (buried home icebox), and potentially number 2 (in conjunction with number 1). We're also going to be doing a lot of canning / preservation, but we'd like to have fresh veggies on hand too. Ideally, we want an outdoor setup, so things will just keep naturally once it gets cold.

posted by puckish to Grab Bag (19 answers total) 5 users marked this as a favorite
I haven't heard much about freezing root vegetables underground but this link from the Colorado extension suggest a number of ways of storing vegetables that doesn't involve freezing. They also list quick solutions (ie the outdoor pit) and more involved ones (building a cellar for your house).
posted by aetg at 5:44 AM on May 31, 2009

You might want to read up on root cellaring.
posted by MonkeyToes at 5:52 AM on May 31, 2009 [2 favorites]

Specifically, ways that don't use electricity [...] In the summer we'd have to keep it stocked with ice; in the winter it should keep on its own.

Where do you plan to get this ice from?

I mean, if the 'no electricity' thing is for environmental reasons, I would have thought store-brought ice would use more resources than making ice in your freezer; and making ice in your freezer would use more resources than just putting the vegetables in your freezer.
posted by Mike1024 at 6:35 AM on May 31, 2009

Liquid nitrogen will just do the same thing as ice only faster. And like ice it will also need to be replaced on a regular basis. A large tank of liquid nitrogen, probably cost you 30-40$ and even un-used will vent/boil off in a week or two.

For long term, electricity free storage, you might want to look into canning or something along those lines.
posted by Captain_Science at 6:46 AM on May 31, 2009

Why not can them instead?
posted by Airhen at 6:48 AM on May 31, 2009

Yeah I'm confused why you're not going with a root cellar?

I think burying things would keep them warmer than leaving them out in the open, where it's cold.
posted by sully75 at 6:50 AM on May 31, 2009

Root cellaring is definitely worth a look. And the book Putting Food By might also offer some suggestions. What might be ideal would be a porch chest freezer that you could unplug on cold enough days, but that will likely fluctuate so you will have to mind the outdoor temps. It would only take a day or so of temps above freezing to begin to thaw the freezer. It should be in a covered area though, not just behind the house. The liquid Nitrogen thing seems a little extreme to me.

We live not far from an old railroad bed, and as the town we live in used to produce a lot of milk, one of the solutions our town fathers came up with for storing the milk still exists near the a part of the rail bed by the creek. They built a partially submerged stone storage room in a part of the creek with a very cold spring feed. The large containers of milk were stored there until the appropriate train arrived. It kept the milk very cold, though not quite frozen. Burying food is an old technique, but some methods are a lot less convenient and reliable than others. And different foods do best with particular practices. Check out Putting Food By for some older practices modified for modern living.
posted by Toekneesan at 6:59 AM on May 31, 2009

Ha! yes, "root cellar" is the operative term here -- now I feel kind of like an idiot. These links are great, thanks a lot!

I guess one of the questions, with an ice box, is how long we can expect ice to keep underground? (If ice will stay frozen for a month, it seems maybe worth doing? If it's a day, obviously not). We're not really "going off the grid" in any sense, but it would be nice not to have two fridges running.

And oh man, Tokeneesan -- your town sounds awesome! I'm guessing they don't still do that, but it sounds really nice. The mounding / cellaring techniques from the second link look really promising - we also have under-the-porch space, which might be a good option for an unpluggable box.

Thanks for the feedback!
posted by puckish at 7:33 AM on May 31, 2009

Ice-box: This creates a fridge, not a freezer. This space will not be below 0C and so it won't freeze anything.

Liquid nitrogen: Expensive.

Running a freezer outside: You want -18C for a freezer. Unless you live in a very cold climate, you are going to be running the freezer most of the whole year (which means you'll be wasting heat form the freezer that you could keep inside your house instead).

Using a root cellar is the traditional way of doing this, but it isn't freezing.
posted by ssg at 7:33 AM on May 31, 2009

Read this book. Some of it is kind of off-the-wall, but lots of both creative and traditional root cellaring techniques in here. I've just been thinking about doing a FPP on this topic, so maybe I'll get cracking.
posted by nax at 7:40 AM on May 31, 2009

Freezing with liquid nitrogen

Depending on the air temperature in the underground/outdoor chamber where you're keeping this, I'm thinking it could get a little dicey in there as cooler nitrogen gas displaces normal air. Again, it greatly depends on the air temperature and pressure in your cave or basement (see this Google Answers thread), but I personally wouldn't want to have any part of the whole "offgassing canister of nitrogen in the basement" idea.

That's not as bad as "dry ice in the basement," though, the results of which I recall seeing on this CSI episode.
posted by limeonaire at 7:40 AM on May 31, 2009

If by "produce", you're talking about the more perishable end of the spectrum (greens, fruits, tomatoes, etc.) as opposed to root vegetables, than I don't think a root cellar will do what you want. It will keep root vegetables fresh for a long time, but they've already got a fairly long shelf life to work with. It'll also extend the life of your produce, but I don't think it's at all a viable solution if your intent is to pick your peppers now and eat them come Christmas.

I don't know off-hand how much electricity is needed to keep an ice chest running, but have you considered solar panels? Also off the grid, but you'd have to consider (a) up-front cost and (b) a fall-back power source.
posted by mkultra at 8:47 AM on May 31, 2009

Have you considered dehydrating? That'd work for all things your root cellar won't work for.
posted by koahiatamadl at 9:54 AM on May 31, 2009

You might want to check out the book The Frozen Water Trade, which explores the history of ice production and storage before electricity. It goes into some detail about methods for harvesting ice during the winter off of ponds and storing it in wooden ice houses insulated with sawdust. Techniques eventually evolved for transporting ice from cold climates to tropical climates on a pretty regular basis.

Anyway, the point is that it's possible to keep ice around for your vegetables during the summer without electricity if you plan far enough ahead and have tremendous resources at your disposal.
posted by Jeff Howard at 12:18 PM on May 31, 2009

I think burying things would keep them warmer than leaving them out in the open, where it's cold.

Underground temperature for a given area and depth is pretty constant year-round. This is why foundation footings are buried a certain number of inches, to get below the frost line, but in summer it will also be cooler than the ground closer to the surface. Your typical cave in North America has a temperature in the mid-50s.

See also geothermal energy, heat pumps, and passive solar homes.

Chest freezer in the backyard and just turning it off in December

At least you know to turn it off. The problem with fridges and freezers outside is that they actually insulate against the outside cold, allowing the contents to thaw out. The thermostat thinks it's cold enough so the compressor never kicks in. This is fine for beer, not so much for meat.

This isn't off-grid, but if your volume is really large enough, you might ask around regarding refrigerated self-storage units.
posted by dhartung at 3:06 PM on May 31, 2009

Your car can be used as a dehydrator. Crack the windows, spread your tomatoes and peppers slices out on a cookie sheet, and let the greenhouse effect do the work. This will preserve the veggies without requiring electricity, and it's a lot easier than make some underground icebox.

I preserve my veggies by canning, which allows me to make salsa, pasta sauce, pickles, jams, etc. for later use. If you are interested in canning, you will need The Ball Blue Book.
posted by Ostara at 3:34 PM on May 31, 2009

Why don't you want to use a refrigerator? All of these techniques seem less than optimal, and more energy intensive than a fridge.
posted by gjc at 7:09 PM on May 31, 2009

"Bury the ice-box [...] In the summer we'd have to keep it stocked with ice; in the winter it should keep on its own"

Please note that plain ice does not keep food at safe frozen temperatures. For all practical purposes it'll only keep things near freezing which is not suitable for safe long term storage of most vegetables. This is why if they power goes out for any length of time your freezer manual will tell you to insert dry ice not water ice to keep the contents from spoiling. It's also why you need to adulterate ice with salt to make ice cream. Burying an ice box will let you use the fly wheel effect of earth temperatures to buffer unseasonably warm mid-winter days and extend the freezing temperatures a bit in the spring though. However if your climate doesn't already have an extended period of time below -17C/0F then you'll need to add extra heat removal capacity in some manner. And lowering the temperature of earth takes a lot of energy.

puckish writes "Ha! yes, 'root cellar' is the operative term here -- now I feel kind of like an idiot. These links are great, thanks a lot!"

A properly constructed root cellar doesn't freeze things so you'll be looking for something else. In fact one of the design goals is to keep the contents above freezing. Also like mkultra says they are generally just for storage type foods. EG: carrots, potatoes, apples, parsnip, rutabagas, sauerkraut (can be safely frozen and thawed though), and unripe tomatoes. Peas, leafy greens, ripe tomatoes, etc. have to preserved by other methods. Dry foods like beans should be kept out of root cellars because the humidity is too high. And of course there are things like pumpkins and other hard squashes that are both late season and will keep a long time even at cool dark room temperature.

PS: The best way to keep food is while it's growing. Swiss chard for example "tolerates frost and freezes into the upper twenties". We plant quite a bit for late fall early winter salads and we routinely pick chard after the first snows. The multi colour variety looks really cool growing in a snow covered garden. The same with carrots and parsnip though you want to harvest those before the ground freezes too much to dig otherwise you'll have a lot of labour with a pick.

dhartung writes "The problem with fridges and freezers outside is that they actually insulate against the outside cold, allowing the contents to thaw out. The thermostat thinks it's cold enough so the compressor never kicks in."

That is not how freezers work. Common domestic chest freezers measure only the temperature inside the freezing compartment. They have no way of measuring the outside temperature and therefor the outside temperature will not effect the on/off state of the thermostat. Thermostats turn on at set point X and turn off at set point X-Y. For a domestic chest freezer X is going to be somewhere in the -17C-0F range and Y is going to be a couple degrees.

Also think "Where is the heat coming from?". Assuming no solar gain, what ever the ambient temperature outside the freezer there is no heat available to raise the temperature above that. IE: if it's -20 outside given time to normalize the temperature inside is going to be -20. Your freezer walls could be a pure vacuum; unless you have something inside creating heat then the temperature inside the freezer is never going to rise above ambient. Turning off your freezer is dangerous as if the temperature rises above safe storage temperatures for any length of time your food will spoil.

However what can happen is compressor oil thickens as the temperature drops just like the oil in your car. The oil can get thick enough at low temperatures that it prevents the compressor from coming up to speed in the short period of time allowed by the start relay. The compressor then clicks off on the built in overload. After a period of time varying between a few seconds a few minutes the overload cools and clicks back on allowing the compressor to try to start again. This repeats ad naseum until either 1) the heat of the overloaded coils thins the oil allowing it to start 2) the overload or compressor burns out 3) ambient temperatures rise to the point that the compressor can start.

Note that "cold enough to congeal the oil" can be much warmer than "cold enough to keep my turkey and OJ safely frozen".
posted by Mitheral at 10:47 PM on May 31, 2009

To clarify -- we're storing up a range of things, some of which (peppers, cucumbers, etc) we'd like to freeze, others of which (potatoes, carrots, parsnips) will keep on their own. As for the logistical hurdles on the original post -- well, it's partly an effort to save space / avoid having to get a second fridge, but it's MOSTLY an opportunity for an interesting house project. But yeah -- for pretty much everything I can think of, it's going to be more energy-efficient to just can stuff or get a mini-fridge. And the preservation methods are going to be different, depending on what we're working with.

Dehydration is something I hadn't actually thought of, but is also a great option. The benefit of freezing with liquid nitrogen isn't cost, so much as it is getting around having to plug something in, and being able to quickly freeze stuff in bulk. Also: less structural damage to the vegetables (which isn't really an issue, but is one of the benefits of doing that over conventioanl freezing)

A root cellar / buried chest (ice or no) has the benefit of being slightly more temperature stabilized (maybe I'm wrong about this?) and so would be good for storing things like cheese or dairy products. I'm not quite sure if it would be worth doing, since these can easily be stored elsewhere --- and I don't actually want this stuff to freeze. So, maybe not such a hot idea.

So yeah -- it's a little vague, I guess, because there's a range of stuff that we want to put up? "No refrigeration" is an arbitrary parameter -- right now we're pretty much just brainstorming, trying to come up with an interesting project for end-of-summer when we actually want to put this stuff away.

Thanks for all the feedback!
posted by puckish at 3:14 PM on June 1, 2009

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