A related post, Only a constant factor worse, discussed a food-buying strategy that would give you an unboundedly-expanding stored-food supply, as long as you're spending more than about US$0.64 per day (US$234/year) on food, and advocated doing so if you're poor, for several reasons: you can buy food only when it's on sale or free, you can buy food in bulk for better prices, and you can keep a wide variety of food on hand to avoid dangerous dietary monotony. Even if you accept that it would be a good idea, it's reasonable to ask how you can practically store such a stockpile.
First off, let's cap the stockpile at a year's supply. Not even the Mormons store up more than a year's supply of food; many people just store up 72 hours' worth for disaster-preparedness. So let's not even consider the possibility of storing two, five, or ten years' worth of food.
Second, let's consider how much space we can reasonably use. I think it's reasonable to dedicate some constant fraction of your living space to food storage, not too much. If 25% of your house is full of stored food, it's likely to significantly diminish your quality of life. Let's figure 6.25% as a reasonable upper limit.
Would you suffer a lot if your house were 6.25% smaller? The smallest house I've lived in was a Volkswagen Vanagon camper bus, which was about two meters by four meters by one and a half meters (although you could put the top up to get a ceiling of over two meters in part of the bus when you were stopped). Getting at daily-use stuff was trivially easy; it was almost always within arm's reach. Getting at more specialized stuff (tools for putting the damn muffler back on again, say) required reconfiguring the furniture, which was kind of a pain.
That was 12 cubic meters of space. 6.25% of it would be three-quarters of a cubic meter, which was about the size of the humongous toolbox we lugged around to fix the thing. Another three-quarters of a cubic meter would have been feasible, but it would have blocked the back windshield; we would have had to put it on the floor when driving or sleeping, and in the bed space when we needed the floor. That is, we could have done it, but it would have been a pain.
However, if your house contains 12¾ cubic meters, you can damn well spare those extra three-quarters of a cubic meter for food storage. If that's useful, which it is, and if it's necessary, which as we'll see, it isn't.
The apartment I'm living in at the moment has a living room, a kitchen, a bathroom, and a storage room, which was intended as the bedroom but has a weird mold smell, so I don't want to sleep in it. I basically live in the living room, which is about four meters by six meters by three meters tall, a total of 72 cubic meters, six times the size of the Vanagon. 6.25% of this would be 4.5 cubic meters; if it's vertical to the ceiling, it would be 1.5 square meters; along the four-meter-long wall, it would shorten the six meters of the room by 38 centimeters. Eminently livable. How much food can you store in 4.5 cubic meters?
In that related post, I was talking about foods like flour, polenta, brown rice, soybeans, salt, and sunflower oil, with total consumption between 600g and 700g per day. These have somewhat varying densities, but they're generally around the density of water: 1kg/ℓ, or one tonne per cubic meter. Which means you can store about four or five tonnes of food in 4.5 cubic meters. That would be about 19 years' worth!
In fact, storing 650 grams of dry food per day, a year's worth of food is only 237 kg. That's not even the three-quarters of a cubic meter that would be 6.25% of the Vanagon. It's more like one quarter of a cubic meter.
This brings us to the problem of the lifetime of stored food. If you just buy bags of food and pile it up in a corner, you will not have a food stockpile that eliminates risks to your food budget; you will have a serious vermin infestation, maybe a mold problem, and probably a lot of expired food. Plus, if you have to move, you'll have one more heavy thing to bring with you. At different times and in different places, I've had to cope with cockroaches, rancid oil, weevils, red flour beetles (or confused flour beetles), and moths in my food. This is where I explain how you can make sure you never have these problems.
I know nine basic strategies for managing the limited-food-lifetime problem:
Things like rice are typically guaranteed good for 18 months from packaging. Even unopened, unrefrigerated mayonnaise is guaranteed good for nine months. So if you consume your rice within 18 months of buying it, you're all good. But that means that, if you open up the pantry and pick between a two-month-old bag and a 17-month-old container of rice, you'd better pick the 17-month-old one. Otherwise, it's going to expire before you finish the last one.
This is known as "proper stock rotation" or "first in, first out" in business. You need to mark each item you have in stock with a date (either its date of origin or its date of expiration) and always use the oldest item.
That means that, if you manage to work your way up to a one-year stockpile, you'll always be eating year-old food. The alternative is to keep buying more food than you need and just throw out the year-old food, wasting it.
You can mark items in lots of ways. I like to use polyester cloth ribbon, tied around the necks of bottles, marked in ballpoint pen. It looks pretty, it's easy to read, it's easy to make, and it's pretty cheap.
Most spoilage problems are caused by stuff getting into food from the outside: moisture, bugs, or in the case of rancidity, mere oxygen. So to keep your food from spoiling, it helps a lot to keep it hermetically sealed. Historically, this was really difficult, and that was a major cause of food spoilage. Now, there are lots of ways to do this: heat-sealed bags, cans, jars with hermetically-sealing tops, Ziploc bags, bottles with corks, and my favorite, screw-top soft-drink bottles.
Screw-top bottles typically have a soft plastic gasket on the inside of the screw-top lid, which the thread compresses against the top of the bottle neck. This seal must be sufficiently airtight to keep the soft drink from going flat. Some, but not all, bottled-water bottles are inferior. You can test a candidate bottle by filling it with water and freezing it, which will stretch the bottle and put the contents under a lot of pressure; if the bottlecap doesn't seal well, the last of the water will be forced out and drip past the cap, forming an icicle in your freezer.
One thing to beware of is that hermetic sealing means that odors and contamination won't have a chance to dissipate. This means that if your hermetic container is leaching stuff into your food, it will build up, rather than bubbling out. This is why "tin cans" traditionally were coated in tin and nowadays are coated in plastic: to keep the steel from ending up in the food. Soft-drink bottles probably won't leach anything toxic into your food (they don't contain bisphenol-A, and the concerns about leaching of antimony-based catalysts have not proven out so far) but they might make it taste like Coca-Cola.
Oxygen rancidifies oils and helps to spoil beer (I think by souring it), and most plastics are fairly permeable to oxygen, including the polyethylene terephthalate used for soft-drink bottles and the polyethylene and polypropylene used for most plastic bags. This is the major reason that beer has not been sold in plastic bottles until recently. Some new formulations of polyethylene terephthalate include a bentonite clay filler to dramatically reduce their oxygen permeability, which has made it possible for plastic-bottled beer to keep. I have no idea how to tell if you have such a bottle. Multiple layers of enclosure, perhaps including a layer that's not plastic, may be a useful way to reduce oxygen permeability.
Latex condoms --- preferably unlubricated --- or gloves may provide a useful level of additional sealing for storage that you don't expect to open and close repeatedly. They have the advantage that they can be stored in very little space when empty.
You can have a container that's hermetically sealed but not vermin-proof. In particular, weevils and flour beetles can tunnel through even fairly thick polyethylene plastic bags, so if one bag in a pile is infested, they will eventually colonize the other bags. So far, I haven't had them chew through soft-drink bottles. (This is one of the reasons soft-drink bottles are my favorite.) I'm sure they can't chew through ceramic, glass, or metal.
Some varieties of cockroaches can chew through wood, so wood may not be a good choice for vermin-proof packaging. It's hard to get wood to seal hermetically anyway.
The Anasazi had a kind of container called a "seed pot" which was vermin-proof but not hermetically sealed. It was a small pot with a tiny hole on top --- maybe 2mm in diameter --- to fill it with dried seeds. Apparently the vermin they had to deal with were mostly mice, not flour beetles, and mice are far too big to get in through such a hole. You break the pot to get access to the seeds.
Mice and rats will not have much trouble chewing through soft-drink bottles, I think, so if you have to deal with them, it might be a good idea to keep your soft-drink bottles inside something mouse-proof, like a metal box.
Because your food might already have vermin in it when you put it into storage, it's a good idea to have at least one level of vermin-proof packaging that's fairly small, say, around a kilogram or so. It would be a real shame if the progeny of two tiny flour beetles were able to spoil 20 kilograms of your stored-up flour. The Anasazi seed pots held about 100 grams. I typically use soft-drink bottles of 1½ liters, although I occasonally use 2¼ℓ and 3ℓ bottles too.
Most kinds of spoilage follow the Arrhenius law, increasing exponentially with temperature; so dropping the temperature even a few degrees can slow a spoilage process to the point where it's effectively stopped --- where it won't proceed to the point of mattering by the time you eat the food. This also means that what matters is not the average temperature at which food is stored, but the maximum temperature, so simply reducing the size of temperature variations will extend the lifetime of food.
Refrigerators, of course, are the most ubiquitous manifestation of this storage strategy in the modern world, but wine cellars are another. Deep-freezes --- large, low-temperature freezers that open on top rather than to the side --- are among the most effective ways of storing food.
I've speculated in the past on kragen-tol about using a superinsulated icebox in place of a refrigerator, and have actually done some experiments with freezing two soft-drink two-liter bottles of water in a freezer and transferring them daily to a 2cm-thick styrofoam cooler in the Buenos Aires summer. Heat leakage was enough to melt about one of them per day. This suggests that 10 or 20 centimeters of styrofoam, or twice that of straw, would be sufficient to give you a low-cost major expansion of your refrigerator capacity, at the cost of transferring ice bottles once or a few times a week.
I also recently did some calculations about using a drying-closet to evaporatively cool air to near the wet-bulb temperature, using the temperature change of the air to drive a constant airflow down a cold-air drain, thus accelerating the drying process. Preliminary psychrometric-table consultations suggest that this could lower the temperature of whatever is below the drain by some 5 degrees under ordinary circumstances.
A pot-in-pot evaporative cooler design won some design awards a few years back. Basically you fill the space between an inner terra-cotta pot and an outer terra-cotta pot with sand, and you keep the sand damp with a watering can so that the inner pot remains at the wet-bulb temperature. This doesn't keep things as cold as an actual refrigerator --- and in humid places it doesn't do much at all --- but in many circumstances it can preserve food substantially longer than nothing.
Dehydrating food for storage has some drawbacks --- the flavor and texture changes, and in most food, not for the better; you typically need to rehydrate it to cook it; and it can be labor-intensive, since only occasionally will food dehydrate without human intervention. Usually you have to spread it out, perhaps cut it into slices, perhaps warm it up, and perhaps drive airflow over it. On the other hand, it dramatically reduces the mass of food, making it more portable; and only a very few kinds of spoilage can attack dry food: rancidity, of course; weevils, flour beetles, and moths, which can get sufficient water by digesting its carbohydrates; and large vermin such as mice and rats, which I fortunately have never yet had to deal with, can drink water elsewhere and then eat your food.
Lack of proper dehydration for storage is a major risk factor for cancer, because aflatoxin-producing molds will infest grains and legumes that are stored insufficiently dry.
One thing to keep in mind is that, once vermin have infested food, they tend to moisten it. Flour beetles and weevils are not, in themselves, toxic, although flour beetles do produce nasty flavors --- but if present in sufficiently high quantities, they will moisten the remaining food enough that it will spoil soon, even if you kill them. (Some people think they add protein to the food, but they do not. They probably do slightly increase the protein fraction of the food, but by reducing its carbohydrate content, not by increasing its protein content. Animals, such as humans and confused flour beetles, do not produce protein. We must get it from our food.)
Some foods have a hard, dry shell protecting a tasty inner core, such as nuts, flax seeds, sesame seeds, sunflower seeds (unshelled), and so on. This only works as long as the outer shell remains dry.
I speculate that empanadas and their kin in other lands originally gained popularity in part because of long shelf life. The surface of the empanada is completely dry when you finish cooking it, and it's impregnated with oil to keep it from moistening from either within or without. The interior, having just been cooked thoroughly, is sterile. I suspect that an unpunctured empanada, especially of the fried type, would have a shelf life measured in weeks or months if you can keep vermin off of it, but I have not yet dared to do the experiment.
A few kinds of spoilage are caused by exposure to light, especially ultraviolet light. Potatoes exposed to light will produce potentially deadly levels of solanine and turn green; beer exposed to light will sour faster; and I think oils exposed to light will rancidify faster. Refrigerators conveniently provide darkness, but other kinds of enclosures may also be useful. And, of course, light produces heat, which can dispel cold and accelerate spoilage.
Even a cardboard box with holes in it can provide useful levels of darkness.
Aside from the obvious and noxious chemical preservation methods, using nitrites, sulfites, formaldehyde, and so on, we have jellying, salting, pickling, alkaline preservation, spicing, and antioxidants --- methods which were more ubiquitous before the advent of refrigeration, but which still extend food lifetimes in concert with refrigeration.
Jelly, jam, syrup, and preserves have too much sugar for much life to survive in them, although they can sometimes grow mold on their surface, where perhaps condensation locally reduced the relative sugar content. I think this kind of preservation works by reducing the osmotic pressure to the point that any invading microorganisms are sucked dry. (Unlike with my stores of beans, rice, legumes, flour, and spices, I've never had an insect infestation in my sugar; the most that happens is that ants may come to carry it back to their anthill, grain by grain.)
Salting works similarly, by reducing osmotic pressure. Thus both jellying and salting work synergetically with dehydration --- dehydration reduces the salt or sugar needed, and salt or sugar reduces the dehydration needed, to reach a given level of longevity.
Mayonnaise is, in part, a way to pickle eggs so they can last for months without refrigeration; and many vegetables can be enjoyed for months or years by pickling them, producing an environment too acid for bacteria to grow in.
Alkaline preservation is not as widely used, but, for instance, from the stench, I think thousand-year eggs are preserved with ammonia, and lutefisk, also notoriously stinky, is preserved and softened with lye.
Many spices are poisonous enough to retard food spoilage. Capsaicin, which makes chile peppers hot, is also a fungicide; and cloves and bay leaves, among others, are sufficiently poisonous to discourage many kinds of spoilage-causing organisms.
Antioxidants such as BHA, BHT, and vitamins A, C, and E (IIRC) can slow down rancidification dramatically, even in the presence of ample oxygen. Palm and camellia oils supposedly have very long shelf lives in part because of their high levels of naturally present antioxidants. I don't know if you can use this property of theirs to impart longer shelf lives to other prepared foods. (Nitrites, I think, are antioxidants too, which is why they keep preserved meat pink. But, in meat, they generate carcinogenic nitrosamines, and the consumption of nitrite-containing meat is associated with a significantly higher risk of stomach cancer, so I don't think the risk is worth it.)
Many food spoilage problems are caused by life forms, like beetles, bacteria, or fungi; some other food health problems are caused by the survival of parasites in the food. Contrary to the medieval and earlier hypothesis of spontaneous generation, if these life forms are initially absent from the food and have no opportunity to get into it, they will never be present, and the food will never experience that kind of spoilage. (It might still get eaten by rats or go rancid.)
So ensuring that the food contains no spoilage-causing life forms is one way to prevent it from spoiling. This is, of course, the main thrust of canning: you cook the can thoroughly after sealing it. Approaches other than cooking include irradiation (sadly, not practical to do at home) and deep-freezing. If you have a small number of weevils or other beetles in your flour or rice or whatever, freezing it for a couple of days can be sufficient to kill them. (If you have a large number, you may still want to freeze the container before you throw it out, to keep them from spreading from it.)
In the opposite direction, many foods are still alive when you harvest them, for example because they are seeds or fruits. They have their own immune systems to fight off disease and spoilage, for a while at least. Green beans can survive and remain free of spoilage for weeks under even fairly unfavorable conditions. Winter squash and potatoes can last for months.
So suppose you have 250 kilograms of dry food with a density of 1kg/ℓ. You need to rotate it properly so as to keep it from expiring, and keep it in hermetically-sealed vermin-proof containers of around a kilogram each, ideally in the dark, at a consistent, low temperature. How do you do it?
A big part of the solution is to store most of the food in 1¼-ℓ soft-drink bottles, making sure it's in pieces small enough to fit through the necks without jamming. These bottles are about 32 cm tall and about 9 cm across. You need about 200 of them, or to allow for the fact that some of them will be partly empty at any given time, 300.
These bottles have a few other advantages over other alternative food storage methods that I haven't mentioned above: they're very difficult to break (I've watched a bus drive over an empty soft-drink bottle without breaking it), they're designed to be food-safe, they're very lightweight, they come in a variety of pleasing shapes and colors, they can be deflated when empty for compact storage and transport (at some cost to their sturdiness and pleasing shape), and they're free, in the sense that they're discarded in huge numbers.
300 of these bottles standing next to each other on the floor would occupy a rhombus consisting of two equilateral triangles some 162 cm on a side, which would actually hold 324 such bottles; its total area is about 2.3 square meters, for a total volume of about 0.73 cubic meters. (That means this arrangement is mostly empty space, which is because the bottles are partly empty and in themselves only occupy about 61% of the volume of the hexagonal prism enclosing them).
These 2.3 square meters (say, a rectangle of 1.6 meters by 1.4 meters) could fit inside a coffee table, for example, which could have doors on the side that open or a top that swings open. 162 cm provides 18 bottles per long row and 17 bottles per short row; 140 cm provides 18 rows, half short and half long. The total is then 315 bottles. A hexagonal or rhomboid coffee table would be both more space-efficient and more entertaining. A few centimeters of styrofoam around the outside and thermal mass such as sand in the bottom would go a long way to keeping temperatures consistent. (If you labeled the bottle bottoms, you could stick them neck-down into the sand, so the sand wouldn't diminish the bottle storage capacity. An average depth of 5cm of sand would need 114 liters of sand, which would weigh about 260 kg, doubling the mass of the coffee table, and probably roughly doubling its thermal mass as well.)
What if you want to shelve the bottles instead? If you divided that area into eight equal-area shelves (spaced 37½ cm apart, floor to ceiling) each shelf would need to be about 0.28 square meters. At a minimal shelf depth of 9 cm --- one bottle --- it would cover a bit over three meters of three-meter-high wall space. If you extended the 9-cm shelving to fill the whole four-meter wall of my living room, you'd have space for 44 bottles per shelf, 352 in all. You'd probably want to hang a curtain in front of it to provide insulation, darkness, and aesthetics. (Although orderly rows of shapely bottles filled with dried foodstuffs of varying visual textures has its own aesthetic appeal.)
While both of these approaches are livable, they still do reduce the available living space somewhat. Your 500-kilogram coffee table would be a hell of a thing to stub your toe on. An approach that would enhance rather than compromise the architectural merits of this living room would be an overhead loft space for the bottles: a single shelf of the 2.3 square meters, some 40 cm below the ceiling, would be 47 centimeters wide, providing an alcove at one end of the living room. Rather than ensmallening the living space, this would just transform a part of it into a cozy nook, enhancing the rest of the room. The ceiling in the nook might be 2½ meters high instead of the 3 meters of the rest of the room.
If you wanted to reduce the physical dimensions of your year's worth of stored food to a minimum without abandoning the bottle strategy, for example to make it more portable, you could probably have an upper layer of bottles neck-down, sticking through round holes in an upper shelf, with their conical necks nestling into the gaps between the necks of the bottles in the lower layer. Arranged this way, I think the second layer of bottles would add only about 22 cm of height to the thing, for a total of about 54 cm high in 1.14 square meters of floor area: 107 cm square, or a hexagon of around 120 cm from corner to corner.
You'd probably want to build the upper shelf in four to six pieces that could be lifted separately, since it would contain 125 kg of food when full, and you'd need to lift it off to access the bottles below. Each of four pieces would weigh at most 32 kg, which most people can lift safely.
Adding a third layer of bottles neck up would increase the total height to some 86 cm and diminish the floor area to about 87 cm by 87 cm. This is probably close to the minimal-dimension configuration, so let's work out the details a bit more.
If you have at least 300 bottles, at least 100 in each layer, you could make the bottom and top layer hexagons of 127 bottles --- 7 bottles on each side of the hexagon, 13 from corner to corner. Then the middle layer would be an uneven hexagon of 101 bottles.
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This gives you a total of 355 bottles, a distance across the corners of 117 cm, and a distance across the flats of 101 cm. Not as small as you might hope.
But 355 seems a little excessive if we just want to accommodate 200 bottles plus some extra to compensate for some bottles being partly empty. Suppose we use smaller hexagons: 6 bottles on each side of the regular top and bottom hexagons, for a total of 91 each, and 75 in the irregular middle layer:
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Then we have 257 bottles, still 86 cm tall, 11 bottles (99 cm) across the corners, and about 86 cm across the flats. This is probably the minimal-dimension configuration.
With the Terma bottles I'm using for my estimates here, you can get a full 10 cm of interpenetration of layers by putting the second layer neck down. But without putting the second layer neck down, just spreading out the spacing of the bottles by about half a centimeter, you can still get about 8 cm, and you can get it with both of the upper layers, instead of just one. This turns out not to be an improvement.
If you actually built this chest full of potentially 321 liters of stored food, you'd probably want to put it on heavy casters so you could move it around. Otherwise it still wouldn't be very portable unless it was mostly empty. 320 kilograms is not a weight you can reasonably lift.
If you don't live up in the air somewhere (I'm about four meters off the ground as I write this), you can get extremely consistent temperatures, constant darkness, and little oxygen just by burying things less than a meter into the ground. Many vegetables can keep at least a year this way, and roots like potatoes, ginger, onions, beets, manioc, and turnips have the additional advantage that they will do the work of burying themselves for you, if you just let them grow. And if vermin attack your root vegetables, well, it's a shame, but at least they're not inside your house.
Geopolitically, root vegetables are credited as a major force in peasants' attempts to evade conquest and taxation in, for example, Zomia (if I recall the name correctly) and Ireland. You can't burn a field of potatoes, you can't tell how many potatoes there are in it, and you can't confiscate them if the farmer won't tell you where they are.
I suspect that you can get some of these root vegetables to last longer than a year by burying them deeper so they don't sprout in the spring.
This brings me to growing food at home, instead of storing it. Among my earliest memories, I remember my mother plowing the back yard with a Roto-Tiller to plant a garden, mostly corn. All my life she's had at least tomato plants, and often sunflowers too; and last I saw, my father (who left her decades ago) had a few rows of corn in his backyard in Minnesota.
That is not the way to save time and money. That's gardening as a hobby, not gardening for frugality and resilience.
To garden for frugality and resilience, you need to focus on the things that provide the highest return --- the least effort for the greatest benefit. As I documented in the other post, you can buy all the corn you can eat for two years for about US$200, at retail. Unless you have less than a few hundred dollars a year to spend on food, or you're preparing for a total collapse of civilization, you shouldn't spend your scarce gardening time on raising more corn or potatoes.
Instead, focus on foods that require very little effort and very little land area, and are difficult to store instead of growing. Don't grow anything you can easily buy dry in quantities you'd eat in a week. For example, here in Buenos Aires's temperate climate:
Sprouts. My first attempt at sprouting turned about 100g of dry, boring, high-carbohydrate mung beans into about 400g of crunchy, fresh, low-carbohydrate, high-protein, juicy stir-fryable vegetables, which lasted several days. It took a few minutes a day for three or four days. My second attempt turned about 100g of dry, boring, high-protein soybeans into a moldy mess. If I figure out how to do this right, I'll be eating some bean sprouts every week, year round.
Rosemary. It's nearly impossible to kill, and although you can dry it for storage, dry rosemary is a pale shadow of fresh rosemary. A single plant in a pot can give you enough rosemary to spice every meal. I think I've heard you can use it to keep moths out of clothing, too, but I haven't tested that.
Hot peppers. Really hot varieties can also provide you more than enough spice for every meal from a single plant in a pot. Some varieties are also spectacularly gorgeous.
Mints. Similarly, a small pot can provide enough mint to spice every meal, and it's hard to kill; the usual problem is that if it's not in a pot, you have to police it aggressively to keep it from choking out everything else in the area. There are a lot of different mint varieties with widely varying flavors.
Basil. Likewise, but you'll need several large pots rather than one small one if you like pesto. Try to keep it from going to seed.
Squash. Squash vines are also quite aggressive and hard to kill, and when their season comes, they tend to produce volumes of squash that go beyond anything reasonable. You can't really raise them in a small pot. Summer squash, once picked, goes bad quickly enough that I fear buying it if I'm not planning to use it immediately, but I think it stays good for weeks on the vine.
Nasturtium. Better known as a decorative flower, it's also edible with a kind of mustard-like spicy flavor. Both the leaves and the flowers are edible, and the flowers are gorgeous. It requires very little care.
Bay, aka laurel. It's a hardy evergreen tree, and its leaves can be used to keep moths away and to spice food; they're strong enough that you usually only need a fraction of a leaf per serving.
Tomatoes. If you have a few meters of fence that you can plant thickly with tomato vines, when they come into season, you can easily have thousands of tomatoes. This requires more care than the other plants mentioned, since the tomatoes are pretty attractive to pests, and they don't keep nearly as long on the vine as the other plants mentioned.
Other herbs: oregano, parsley, cilantro, thyme, sage, lavender, lemon verbena, and so on. Many herbs are much better fresh than dry, will rot if you cut them and don't dry them, and can't be bought in small enough quantities for a single meal. If you have a dozen pots of a dozen different herbs, you can choose among a dozen different fresh herbs for every meal. This can go a long way toward making frugal food palatable.
I've heard that chard also has pretty good frugality performance, is dead easy to grow, and grows year round, but I haven't tried growing it yet myself.
Olives, if you inherited an olive tree. Otherwise, maybe plant one and hope your grandkids will benefit.
Mushrooms, maybe? I don't know how to grow mushrooms, but they don't need access to sunlight, they can live on garbage (right?) and one or two of them really dramatically improve the flavor of a lot of foods. But they don't last long, and you often can't buy just one or two.
Blackberries, if you have a lot of land, or mulberries. Blackberries are thorny, but otherwise easy to pick, and they're very hard to kill; you don't need to worry about pampering them. They make a wonderful jam, which you can eat year-round if you can it when they're in season. I haven't seen them growing in Buenos Aires, but they grew wild and abundant in the Presidio in San Francisco, whose climate is similar. Mulberry trees are also quite hardy once established --- IIRC they can grow deep taproots to survive long droughts --- but they take years to mature, and your chances of getting a male tree that produces no fruit is 50-50. Mulberries essentially cannot be bought, because they don't last long enough once picked.
Stockpiling food, as explained above, is a potent weapon against poverty and geopolitical uncertainty. Stockpiling water will probably not help you get out of poverty, since you already buy it in bulk, you don't benefit from variety, and it's never on sale. And water supplies typically remain available anywhere inhabited by people, except for short periods of time, even when your city is being bombed to smithereens.
Sometimes, however, a "short period of time" might be three or four days, or a week, due to nothing more serious than a power outage. A sufficient stockpile of water can improve your resilience against power outages. It's really hard to cook dried food without water.
At Burning Man, we had to bring our own water. The recommendation was 8 ℓ/day, for cooking, drinking, and showering in an extremely hot, dry climate. A week's worth would then be 56 ℓ. That's about half a bathtub full, and if you have a bathtub and forewarning of a possible interruption, filling up the bathtub is a reasonable response.
If you want to be prepared for a week-long water interruption without forewarning, it's not reasonable to keep your bathtub full of clean water all the time. The water will go stagnant and breed algae, mold, and mosquitoes. You'll stink from not bathing. Instead, you need containers, you need to be able to seal them, and you need to remember to rotate them.
For Burning Man, we actually used 56-liter military-surplus bacteriostatic plastic water bottles. Rotating 56 liters of water every few months is going to be a huge pain in the ass if you're trying to use containers much smaller than this. 20-liter bottles might be reasonable, and they're a lot easier to move around than the 56-liter ones are. 3-liter bottles are not reasonable.
A 200-liter barrel is probably a thoroughly reasonable and widely available solution. Food-safe, sturdy 200-liter plastic barrels with sealing screw tops are a standard item all over the world, as are devices for moving them around when they're full. They go for about US$10 to US$20 used in the US.
For your house, though, you'll probably want to fill and empty the barrel with a hose.
A more ghetto, but also quite effective, container is the 20-liter soy-sauce bottle, which is small enough that you can carry it around when full, rectangular, and unlike the mil-surplus bottles we took to Burning Man, stackable. I wash my laundry in a bucket cut from the bottom of one of these that I found near a dumpster outside a Chinese restaurant last month, labeled "DO NOT REUSE". They're made of thoroughly unbreakable polyethylene, they have handles to lug them around with, they're food-safe, and originally they ship with a hermetically-sealed screw top. They're not bacteriostatic, though, and the one I fished out of the trash stream had been long separated from its screw top.
Three 20-liter soy-sauce bottles, a week's supply of water, would occupy a little less space than the year's supply of food considered earlier.
It's recommended to chlorinate your stored drinking water with bleach to a level where it's not really safe to drink, I think 100ppm or 200ppm. Water thus chlorinated should last for months or years. (I forget what the official recommendation on rotation for water thus chlorinated is, but I think it's six months or a year.) Before you drink it, you dechlorinate it by letting it sit in an open jar overnight. (I think you can boil it, too, if you're in a hurry.)
There are other poisons you could put in the water to keep it sterile, but they're harder to remove.
If you wanted to store enough drinking water for a year, perhaps because you were insane, the 8 liters a day multiplies out to 2920 liters for the year: fifteen 200-liter barrels whose contents you'll have to rotate once or twice a year. This is three tonnes of water, occupying three cubic meters. This would occupy less than 6.25% of my living room, so it might be a reasonable thing to have in your house --- or, better, outside your house where it won't wreck everything if it springs a leak --- if you had some other use for it, other than preparing for a disaster that is unlikely ever to happen.
For example, three tonnes of water is a fairly large thermal mass, and eminently capable of internal convection. Raising or lowering its temperature by a degree requires 13 megajoules, which is 3.5 kilowatt hours. Freezing or thawing it requires almost a gigajoule, 260 kilowatt hours. This could allow you to time-shift the use of energy to warm or cool something to a time of day when energy is easily available, or to harvest ambient temperature at a reasonable time of day.
Or you could put it in a swimming pool and filter it if you wanted to drink it. Swimming pools are still a pain to maintain, but at least they're fun, in a way that a psycho apocalypse water barrel complex isn't.
Speaking of the same thing more prosaically, if you have a tank of hundreds of liters of water, it's not going to change temperature much between day and night unless it's really, really shallow, so you can take a cold bath any time, day or night. In a heat wave, this can save your life.
A lot of the food I've described here isn't edible without cooking. Some commonly-eaten legumes are actually dangerous to eat raw, especially kidney beans. But if you can't pay the bill one month and they turn off your gas or electricity, or if there's an earthquake, or if somebody's air force bombs your city's power plants or transmission lines, or there's a heat wave and consequent power outages, you could be out of luck forever if you don't have fuel stored up.
And energy is important for other things as well as cooking.
The most common response to this situation is to cook with wood, dried poop, or charcoal, which isn't very convenient and is dangerous --- it produces carbon monoxide and, except for charcoal, carcinogenic and irritating smoke. (This is the biggest cause of childhood death today, now that we've dramatically ameliorated the diarrhea situation.) The fuel is also kind of a pain to keep stored, and it can harbor wildlife, including termites, deadly spiders, mice, rats, and cockroaches.
The next-most-common response is to store LP gas or CNG in a tank, either inside or outside your house. This works fine, is reasonably safe, and is extremely convenient because you can adjust the flame instantly. It does involve a certain amount of up-front investment if you're not renting the tank, and it's not completely safe; people have produced spectacular explosions by accidentally driving cars into LP gas tanks.
A less-common approch is to cook with alcohol. The Penny Stove is a stove burner which can cook a meal with tens of milliliters of alcohol, weighs a few grams, and can be made from two discarded aluminum cans and a worthless coin. Ethanol is a particularly safe fuel: it won't explode if its container is breached, doesn't usually burn the surface it's burning on top of (so it probably won't burn your skin if you get splashed with it), can be extinguished with water, produces very little carbon monoxide when burning, and is much less toxic than alternatives like gasoline or methanol. It's also usable for disinfecting water or wounds and as a solvent for some things, and because it doesn't require high-pressure containment, it's more portable than LP gas or CNG. It's much more expensive than those fuels, though. Ethanol here currently costs about AR$20 per liter, and that liter might cook 50 meals --- AR$0.40 per meal. In the Penny Stove, it's also less controllable than gas fuels, but I think there are camping stoves that provide similar levels of control to a regular gas stove.
If you're poor enough to worry about US$1 per day of food costs, cooking on alcohol may be a low-upfront-investment alternative to buying a gas cylinder or hookup and gas stove. It's a lot more convenient and safer than wood or charcoal. It might even be cheaper than those fuels if you have to buy them, but most people scavenge them instead.
I've previously written on kragen-tol about inherently-safe ethanol storage XXX by floating your ethanol bottles in your water stockpile, so that almost any conceivable storage accident will result in the ethanol mixing with the water and becoming nonflammable.
Solar cooking is a zero-fuel-consumption alternative, but it's less convenient than cooking with fire unless you have a bunch of heat-storage bits that are not very frugal yet. Still, I think you can make reasonable solar cookers entirely out of garbage, assuming you have sunlight access.
Specifically, if you have a thermal storage tank for molten salt, you can use that to cook with solar heat whenever you want; the eutectic mixture of nitrates of potassium and sodium melts at 221°, hot enough to bake with, and has a heat of fusion near that of water, so you can store a huge amount of heat in a tiny space. But this is very far from being a practical option to save money.
Refrigeration also suffers when energy supplies are interrupted. If you have a superinsulated icebox as I suggested earlier, or even if you keep your refrigerator and freezer full of bottles of water when they have available space, you may be able to weather some days without refrigeration power.
In our Vanagon, we had a dual-fuel refrigerator, which could run off the 12-volt van electricity (for hours) or the 12-liter LP gas tank (for days or weeks). It was of the ammonia-absorption type, which is somewhat more hazardous than the usual HCFC-compression type to have inside your house, but has no moving parts other than the gas valve. Gas-fueled refrigerators are common in houses in rural parts of the US.
With a somewhat more elaborate system, I think you could run an ammonia-absorption chiller from a solar concentrator to freeze ice (maybe salted) during the day, and use the ice with a secondary heat transfer circuit to keep your food cold. This is not very practical for individual frugality unless somebody commercializes it.
Jesus, you think it's cold in your house without the heat on? Do you have a medical problem with body-temperature regulation? Otherwise, you know, in igloos, people get naked, even though the igloos aren't melting. You can adjust. Insulate your house, chink the cracks, put on a sweater, put a mylar blanket over your regular blanket, snuggle up to somebody, and quitcher complaining.
(Some solar thermal mass might help too.)
This is a bigger problem; many more people die in heat waves than in cold waves. Their houses get too hot, because they don't have air conditioning or because the power went out, and they die. As the climate changes, we'll see more and more heat waves, and more and more mass deaths as a result. Air conditioners require a lot of energy; you need a hefty generator to run one, and it will gobble up lots of generator fuel. In theory you could run one off solar heat (see earlier comment under Refrigeration) but it's simpler to just have lots of thermal mass around you, thick enough that it'll stay cool past the end of the heat wave. Traditional adobe construction was about a meter thick, and solved that problem.
In theory, you could build a Thermal Mass Stockpile in your house just like an emergency food or water stockpile. In practice, it's considerably more difficult and not really practical. It would be a little alcove of adobe (or brick, or stone, or concrete), just big enough for you to be comfortable inside, with meter-thick walls, ceiling, and floor, and a closeable door. If you made it horizontal --- a thermal-refuge version of a Kapuseru Hoteru bunk --- you could probably get by with a one-meter by one-meter by two-and-a-half-meter inside volume, enough of a sturdy metal frame to keep it safe from collapse, a mattress, and a light. The outside dimensions would be 3 m × 3 m × 3½ m, for a total volume of 31½ cubic meters, of which 29 cubic meters would be adobe. About 64 tonnes of adobe. This is going to be more than 6.25% of your living space, and your downstairs neighbors are going to raise hell about the cracks in their ceiling.
(You could actually keep your food and water stockpiles inside of it, keeping them at a consistent temperature and slightly cutting down on the adobe requirements all at once.)
Failing that, if you have, or recently had, a working refrigerator, soft-drink bottles filled with frozen water can make a huge difference. Sleep with one, wrapped in a towel, at night; snuggle up to one during the day. If the air temperature gets above about 35°, snuggle up to an ice bottle or two under blankets; instead of keeping your body heat from escaping into the air, the blankets keep the air's heat from escaping into your body and the ice bottles. In a sense, your ice bottles are your "stockpile of air conditioning".
Or you could take a cool bath, if you have or can get cool water.
If you live on the ground instead of up in the air like me, you can just dig a meter-deep trench in the ground, shore it up to keep it from collapsing, put a cover over the top, and lie down in it. This has its potential problems (radon, groundwater, propane or freon) but digging out five or six tons of dirt beats the hell out of molding 64 tons of it into bricks or heaping 64 tons of it on top of your box.
All of these thermal-mass stockpile approaches become slightly more practical when they're for more than one person. If you have four people, you can build a 4×2½×1 meter capsule with a meter of adobe around it, and instead of 64 tons of adobe for one person, you have 5×3½×3 - 4×2½×1 = 42½ cubic meters of adobe, or 93½ tonnes for four --- less than 25 tons each!