For sanitation in temporary emergency situations, a chemical (portable) toilet is the easiest to store and set up. Portable toilets are easy to store, but require disposal. If there won't be any entity helping with waste disposal, a longer-term solution of digging a latrine might be a better option.
A chemical toilet is one that utilizes different chemicals to deal with the smells and disinfect your waste. Portaloos (portapotties), RV toilets, airplane toilets, and portable toilets work this way. You can turn an existing toilet into a chemical toilet by emptying the water and inserting a plastic bag inside the bowl. In it's simplest form, a bucket with a trash liner can also be used to create a chemical toilet. Two boards placed parallel to each other can create a more-comfortable, make-shift seat.
After using the facilities, commercially-available chemical packets, or home-stored chemicals such as baking soda, lime, or bleach are added to the toilet bag to maintain sanitation. The American Red Cross recommends that you "pour or sprinkle a small amount of regular household disinfectant, such as creosol or chlorine bleach, into the container to reduce odors and germs."4
You can buy portable toilet kits which just include a bag and chemical packets. Other kits include the seat and/or stand. Some even "flush" into a lower chamber to reduce smell. The downside of a chemical toilet is that waste still needs to be disposed.
Many sites recommend disposing waste in an outdoor container until your local governments collect it. If you feel that a quick response is reasonable, then store an extra trash container with a tight fitting lid to be used for this short-term disposal. In a situation where collections might not be soon available, official emergency sources recommend that you "bury garbage and human waste to avoid the spread of disease by rats and insects. Dig a pit 2 to 3 feet deep and at least 50 feet downhill or away from any well, spring or water supply."5
Store: Bucket, lid/seat (or other configuration), garbage-can bags, chemicals.
Pros: Easy and readily available.
Cons: Waste still has to be disposed.
If you find yourself without toilet facilities for a longer period of time, you might consider digging a latrine (privy or outhouse). In reality, people have lived without sewer systems much longer than they have lived with them. It's not been so long since digging a hole for an outhouse was the norm.
The big concern in latrine construction is fresh water contamination. It is essential that toilet facilities be placed where they will not contaminate ground water, fresh water wells, or streams. 50 feet from homes or water sources is a widely cited distance for location of toilet waste. Some areas have high ground water and require that outhouse facilities be located elsewhere in order to protect drinking water.
An adequate hole for a privy would be about five feet deep (which gives you about five years worth of sanitation disposal depending upon use).6 Sources vary in their suggestions of depth from as little as four feet to as much as 15 feet (larger depths require reinforcing the walls to eliminate the risk of cave-in). After digging a hole, a board with a hole cut in the middle can be placed on top to cover the pit. Your privy would be usable at this point, but probably not comfortable. You can add an elevated box or a chair with a hole cut into the seat to make sitting more comfortable. A hollowed bucket with two boards on top would be better than nothing.
At this point, you would also need to address the smell. Whatever construction method you use, it is important to have a lid of some kind to close off the pit which would help to contain the smell. An outhouse can utilize a built-in vent pipe to reduce the build-up of methane gas and disperse the smell into the air. Flies are attracted to the smell and can cause the spread of disease. If you use a venting pipe, make sure to add a screen on top to reduce access to flies and other insects. Fly paper placed inside the facility would also reduce the flies somewhat.
Privacy is a huge issue with outdoor toilet use. There are pop-up tents available for this purpose. A regular tent or even a tarp could also be modified to give privacy. Because a latrine is located outside, weather considerations are important as you build your new facility. Tents and tarps will have to be anchored to ensure resistant to winds, rain and/or snow. If you have the resources to build a permanent wooden facility, weather would be less of a concern.
Store: Shovels, pick-ax, large piece of wood to cover the pit, bucket (or other seat), tent/tarp/wood for privacy.
Pros: Waste is disposed as part of the design. No need for additional chemicals.
Cons: Requires time to set up/dig, usually smelly, cold/hot and uncomfortable.
Make sure that you also store sanitizer, sanitary pads (dispose separately), and septic-safe toilet paper in addition to any other supplies for your toilet.
Click here to go to Toilet Troubles (part one).
1 - Christchurch earthquake: Survival in the suburbs
2 - Strangers brought together by quake stories
3 - Christchurch earthquake: Many face weeks of temporary toilets
4 - American Red Cross - Emergency Sanitation
5 - University of Florida - Emergency Sanitation
6 - How to build a latrine