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In JWR’s book “How to Survive the End of the World as We Know It” , item number 11 on the Bartering and Charity List is “50 pound sacks of lime (for outhouses”). My first thought on reading this was, “Why would I barter away my precious lime?” More than just an odor eliminator, lime is a very helpful material used for countless applications in its various forms across various industries ranging from use in the production of glass to use as a calcium supplement in Tropicana brand orange juice.

My initial research was designed to discover which type of lime would be best to buy in bulk, based on its price and versatility in regard to survival needs. Ultimately my research has provided more questions than answers, more starting points for more research projects rather than full-fledged answers. However, I do believe that the common uses I have discovered at this point provide a comprehensive springboard which can serve as starting points for future research for all long-term preparation.

The most important thing to distinguish when acquiring lime is the type of lime and storage capacities based on your targeted use of the product. Besides the lime fruit, which will not be discussed in this article, “lime” generally refers to three types of limestone-derived materials: Limestone, Quicklime, and Hydrated Lime. It is important to explore the different uses of each type of lime and its availability in order to plan accordingly.

Furthermore, it is important to note that the chemicals come in different grades as recognized by the FDA: Pharmaceutical (Pharma), Food, Feed, and Industrial/Technical, with pharmaceutical and food grade being safe for human consumption.

Below are each of the common types of lime, their storage recommendations, and uses. What is not included: uses of lime (and there are many) that are outside of the normal scope of survival, such as using limestone to make glass or using hydrated lime in the petroleum refining process. If you are curious, there are abundant resources about the many uses of lime on The National Lime Association’s web site, as well as endless references throughout the Web.

I. Limestone. This is one of the cheapest forms of lime since it is generally made from crushed limestone. Calcium carbonate or calcite (CaCO3) is the primary component of limestone, though CaCO3 derived from limestone may contain pollutants and should not be used for human consumption unless specifically packaged and sold as food or pharma grade calcium carbonate, such as antacid tablets. Crushed limestone is also known as aglime or agricultural lime/limestone and garden lime and is available at most gardening centers and feed stores.
A. Dolomitic lime. Calcium magnesium carbonate: Dolomitic lime is usually also crushed limestone, but with more magnesium, so I group it here with limestone. Limestone generally has varying levels of magnesium carbonate in the form of dolomite (CaMg(CO3)2)—thus, the name Dolomitic lime or  magnesium limestone. Dolomite  has many of its own uses and could warrant its own article, though one must be careful using dolomitic lime as it is not pure dolomite and is often not food or pharma grade. Furthermore, the presence of lime may create separate complications when using dolomite for chemical reactions or consumption. Food grade dolomite can (and should) be purchased separately these purposes.
B. Storage: Aglime should be kept dry mainly because it is hard to use it when it is a sludge, and it can cake up when it dries, making it hard to use. Compositionally, water is not harmful to it, except for the fact that limestone is highly absorbent and can absorb hard metals and other substances into it. If you plan on using this lime for gardening or outhouses for an extended period, consider keeping it in a 5 gallon bucket with a lid.
C. Precautions: Limestone is generally considered chemically inert, but it is a chemical base. Aglime can cause skin irritation, redness and burning of eyes, and prolonged exposure can cause irritation of the respiratory tract. Can worsen asthma.
D. Uses: Many uses of aglime can also be mimicked by quicklime or hydrated lime, so its uses are listed under Interchangeable Uses below. As mentioned before, I am not including industrial uses for lime that may be too far out of the normal purview of survival.

II. Calcium oxide (CaO). This is a more volatile form of lime that reacts endothermically with water. It is formed by baking calcium carbonate in a kiln at temperatures between 900-1000°C (1652-1832°F). It is also known as quicklime, hot lime, or burnt lime.
            A. Storage: Quicklime needs to be stored away from all moisture in containers that themselves are moisture proof. Over time, a container may absorb some moisture, and this can cause the quicklime to either melt the container or even explode, depending on how much water has reached it. Calcium oxide is not a flammable material, but its reaction with water can cause high temperatures. It should not be stored near combustible materials.
            B. Precautions: Besides precautionary measures for storage, one should remember that quicklime is especially dangerous to animals because of its reaction with water, and it can cause chemical burns to the eyes, throat, lungs when it reacts with the body’s moisture. It has actually been used as a chemical weapon for this reason (see below).
III. Calcium hydroxide (Ca(OH)2). This is also known as hydrated lime, slaked lime, cal, and pickling lime. Cal and pickling lime are both food grade. Hydrated lime has an impressive range of use across multiple industries, including the food industry, oil and gas, metallurgy, construction, and many others. It is formed by adding water to quicklime. Food grade is fairly expensive compared to industrial grade—a 1 lb bag of pickling lime is currently $4.69 on Amazon, whereas Tractor Supply Co. sells a 50 lb bag of [non food grade] hydrated lime for $7.99.

IV. Uses (In no particular order):

1. Blacksmithing. Quicklime is commonly used as a flux for removing impurities from steel. Hydrated lime is used to whitewash steel products to provide corrosion protection as well as lubrication.
2. Smelting. Quicklime and hydrated lime are both used in the recovery of nonferrous ores from various other materials.
3. Construction. Aglime is often used as an aggregate, and quicklime is a binding agent in mortars, cements, concretes, plasters, and stuccos. The type of lime required varies with the product, but each type of lime has some use in construction. Using lime goes back to ancient times of combining lime, sand, and water to make primitive masonry.
4. Construction. Hydrated and quicklime may be used as a firming agent for wet soil to expedite construction. Quicklime in pebble form is preferred over hydrated lime, though both do work.
5. Gardening. Use aglime as a soil sweetener to raise PH levels of soil in gardens. Some gardeners prefer dolomitic lime to regular ag lime because it also adds magnesium to the soil. Hydrated lime is more effective at raising pH levels, though it may contain less magnesium, and is generally more expensive. My dad limed a single field years ago, and it is still the greenest field and best producer on his land.
6. Livestock. To control flies in barn areas, spread aglime on the barn floor. Hydrated lime works, too. This will also control unwanted odors. Be careful if you are using manure to fertilize your garden as the lime can make it more alkaline, though many gardens actually need it. The latent benefit is that one can both fertilize and sweeten the soil with manure that has lime mixed in already.
7. Outhouse. To control odors in outhouses, sprinkle aglime over waste. Any of the other types work, too, though one should probably avoid combining quicklime with water needlessly. Any other offensive odors can be treated similarly.
8. Fishing. “Liming” a pond is common in the southeastern U.S. where soil tends to be more acidic. This greatly increases the availability of nutrients and production of phytoplankton (the base of the food chain in a pond), increases the pH levels of the water and helps to stabilize fluctuations in pH levels. Hydrated lime achieves the same results, but it can kill the fish because it raises the pH levels quickly, so its use is reserved for sterilization between crops at hatcheries.
9. Water treatment. In water purification and treatment, hydrated lime is used to adjust pH levels, as a softener, as a coagulate and flocculate, as a disinfectant, and in purification. Dolomitic lime is effective in removing silica from water in water treatment processes. The Coca Cola company is among Mississippi Lime’s clients, where it is used in the manufacturing of Coke (processing of water), although it may have other uses there, too.
10. Instruction. Limestone was once the core component in making chalk for use on a blackboard. I am still looking for an exact recipe here, but previously chalk was made from ground limestone, whereas today it is mainly made from gypsum. In traditional chalk-making, the limestone was mixed with pigments and baked, but I have not experimented with this yet. Adding clays and oils creates pastels, which are air-dried. Chalk provides a long-term solution for brainstorming, schooling, and other instruction without having to worry about ink or graphite supplies.
11. Heating. Quicklime is useful as a heating element in self-heating cans or foods when mixed with water. You may have seen the internet video of the hillbilly hot tub, which uses quicklime and water to heat. Calcium oxide can be used on a much larger scale if needed as emergency heating, and the byproduct is hydrated lime, which has its own uses. Smokeless/fireless heat can be very important if one is on needs to remain undetected, although there is some amount of “smoke” from the chemical reaction, which quickly dissipates. Avoid using quicklime in enclosed areas.
12. Lighting. Quicklime may be used as a non-electric source of bright lighting. The limelight (or calcium light) was used to light stages for quite some time before electrical lighting took over. Simply put, limelight was calcium oxide heated with a hydrogen torch, which emits a bright glow. The lowest temperature required for the glow is around 1000°C or 1832°F, which can be easily achieved by a propane torch, stove, or heater.  Although not as efficient as other forms of lighting necessarily, it is at least another option to file away, especially if you already plan on using propane to cook or heat and want to set up a limelight. Calcium oxide melts at around 2572°C or 4661°F, so you have a lot of leeway between making it glow and actually melting it.
13. Weapons. Because calcium oxide reacts endothermically with water, it can be particularly dangerous to the skin, eyes, lungs, and digestive tract. It can cause chemical burns in the throat, lungs, nose, stomach, etc. The MSDS for quicklime does not list it as a fire hazard, but it does note that its reaction with water can be hot enough to ignite combustible materials, which is one of the theories of why it may have been a key ingredient for Greek Fire. Author David Hume’s 1688 work The History of England claims quicklime was used by the English to win a critical battle against the French by positioning themselves upwind and throwing quicklime in the French’s faces. Ouch.
14. Tanning. Hydrated lime is used for removing the hair from hides in the tanning process. It is also a key ingredient in human hair removal lotions, such as Nair. It is also used as a hair relaxer.
15. Cooking. Cal (hydrated lime) is a critical ingredient in in making masa (corn dough) and hominy. Masa is the basis for corn tortillas and tamale dough. The process of making masa (called nixtamalizing) actually does make the corn more digestible and, therefore, more nutritious (not to mention the added calcium). As an added bonus, because of hydrated lime’s preservative properties, corn tortillas tend to keep much longer than flour tortillas.
16. Dietary supplement. Small amounts of food grade hydrated lime are added to Tropicana orange juice to fortify it with calcium, and it is also used in baby formula. The Poison Control Center tells me that you would have to eat huge amounts of this before it would do you lethal harm. Remember, however, that it is a base, which is why it works well in orange juice to counteract the acidity of the citrus, but by itself it may cause irritation in the throat or stomach.
17. Whitewash. Hydrated or aglime are combined with water and salt to make whitewash or lime-wash. Besides aesthetically pleasing, some claim whitewashing a roof with lime-wash for collection of rainwater helps to pre-treat it, which makes sense since lime is antimicrobial and helps in water purification. This is done in countries like Bermuda, which have no natural fresh water reservoirs and rely on rainwater for consumption.
18. Food preservation. Hydrated lime is also called pickling lime because it can be used in pickling. Furthermore, hydrated lime has great antimicrobial/antifungal and preservative properties, which is an added reason to use it. My mother, who lives in a swampy area, is unable to use a root cellar, so she sprinkles aglime on her potatoes through the winter and has no problem with them going bad. If you utilize this method, wash the potatoes thoroughly. Hydrated lime is the active ingredient in a compound called Polikar, which is used for preserving vegetables. See more below on lime’s antimicrobial properties.
19. Gardening. Hydrated lime is effective against many different types of insects, often killing them through contact, and it is an active ingredient in some insecticides on the market, which is why it is so effective at treating excess flies in a barnyard. Hydrated lime is an active ingredient in the Bordeaux mixture used by vineyards to fight fungus.
20. Antimicrobial/antifungal. Lime’s antimicrobial properties can (in theory) help fight certain types of blight, although I have not found reliable documentation for this. It is boiled with sulfur to make a mange dip. A more powerful pharmaceutical grade calcium hydroxide (pH 13 instead of 12ish) is used in dentistry as a paste to treat microbes when dealing with root canals. These antimicrobial properties are one of the primary reasons why lime is effective at controlling odors.

After reviewing my own list, it is difficult to determine exactly which type of lime one should concentrate on, and I believe that stocking up on any one type should be governed by your intended use. I do believe that food grade hydrated lime is possibly the most useful of all of the types of lime since it can be consumed and still has the critical properties needed for all of its other uses, not to mention the fact that it can fulfill many of the same functions as the other types of lime. Additionally, heating hydrated lime to around 512°C (954°F) evaporates the water from it and forms calcium oxide (quicklime), so one can easily create his/her own calcium oxide if needed.

Of course, following that philosophy, one could theoretically stock up solely on aglime, bake it to create quicklime, and then combine the quicklime with water to create hydrated lime, although that whole process requires an investment in a lime kiln and other materials, and the hydrated lime would not be edible.

The most practical recommendation would be to stock up on a proportionate amount of each type relative to your intended use. Quicklime is a little harder to find these days, as it either comes in very small amounts (such as 400g) or very large amounts (several tons). You may be lucky enough to have a building materials vendor that sales it in your area, but you will probably have to make a few phone calls. The National Lime Association lists companies in each state that produce lime, and they will either sell it to you directly or point you to one of their distributors. Hydrated lime, dolomitic lime, and regular aglime can all be found easily and are fairly cheap (if not food grade)—all of them can be found for around $10/50lbs at most gardening or feed stores.

General Warnings:
For complete details on lime, its health risks, and precautionary measures, please visit the manufacturer’s site for MSDS information. I used Mississippi Lime’s MSDS for my information, as well as interviews with scientists at the FDA and in the labs at various limestone companies.

All forms of lime can cause irritation to the skin, eyes, throat, and lungs. One should take precautionary measures with all lime.

Consuming different grades of lime can have hazardous effects. There are many different potential contaminants in limestone, which realistically can vary from quarry to quarry even in the same region. These can vary greatly, but possible contaminants include lead, copper, fluoride, arsenic, cadmium, and petroleum distillates among others. Quarries near mines or areas that use hydraulic fracturing (“fracking”) are also at higher risk for contaminated limestone. Remember that limestone (from which most quicklime and hydrated lime also derive) is sedimentary rock and therefore vulnerable to outside contaminants. For example, the EPA permits industrial sewage sludge to spread over farms, which could potentially leech through the soil down into the limestone, introducing cadmium as a contaminant.

That said, Mississippi Lime, which, from my own research as well as information from the National Lime Association and the company itself, is possibly the only company in the United States that produces food grade calcium hydroxide, explained to me that most lime is naturally fairly compliant with FDA regulations except one major element. In the case of the limestone they quarry, the limestone naturally conforms to all FDA requirements for traces of lead, copper, iron, and other pollutants except for fluoride, which may be present in over 100 PPM (the standard is 50 PPM). Basically, besides cleaning it better, the only difference between their agricultural grade calcium hydroxide and their food grade pickling lime is that they have removed some of the fluoride. With other quarries, the amount of pollutants is difficult to determine since they do not perform tests that measure all human toxins, although, depending on the company, they may remove heavy metals even in the agricultural grade aglime or hydrated lime. Agricultural grade does remove lead and arsenic to accepted levels.

Sources:
The National Lime Association’s web site is a great starting point for any research involving lime. They were also a valuable resource for pointing me to the proper people to whom I could pose my questions.

The people at Mississippi Lime were extremely patient and helpful to me in answering specific questions about the processing of food grade lime and many of its various, diverse uses. I also spoke with various other company representatives of other lime companies, but I mainly reference my conversations with Mississippi Lime employees.

The kind scientists at the FDA were also surprisingly helpful about hazards, potential contaminants, and diseases associated with lime and answered all of my questions with expertise and competency.

The Poison Control Center provides 24/7 free information about the toxicity and dangers of the various types of lime. You can call them for all non-
emergency questions, too, so feel free to do so with any questions you may have about lime or any other product. Their answers tend to be less substantiated and scientific than the FDA, but they are easier to contact.

Brazilian Dental Journal and my brother, who is a dentist s helped me with specific uses of lime in dentistry.