As Hurricane Katrina taught us, dealing with human waste is a big problem in a disaster. Historically, because of poor sanitation, more people have tended to die with the epidemic of disease following the disaster than in the disaster itself.
While smaller regional disasters may not affect plumbing, a catastrophic event disabling the US power grid would likely affect water sanitation and availability.
So if indoor plumbing is disabled and availible water must be conserved for drinking and not flushing, how should one best deal with human solid waste?
If the plumbing is going to be out for months, everyone will eventually run out of logs to squat over. A great alternative to the odoriferous outhouse is the composting toilet or "biolet".
The principles behind a composting toilet are several.
1. It is very difficult and expensive to clean fecal bacteria from water so DON'T poop in your water. Biolets keep liquid and solid human wastes separate.
2. Because fresh human urine is sterile, it can be diluted and used as fertilizer immediately. Urine must be collected and kept separate from solids.
3. 90% of the volume of human solid fecal waste is water and air. So the action of a composting toilet works to dry human waste, shrinking it down to a small fraction of its original volume.
4. Bacteria and odors are eliminated by aerating and drying the waste. Usually the collection container is partially filled with some sort of absorbant waste biomass (peat moss, dry grass, shreaded news paper, ect). The biomass serves to absorb moister and increase aeration and surface area.
5. The enemy to bacteria is dryness. Bacteria cannot survive long without water. Biomass also introduces fungus in the compost which inhibits bacterial growth and suppoerts further natural decomposition.
6. Biolets are easy to plumb as the simplest designs just require an exhaust pipe. Modern designs are fitted with exhaust fans and heaters however these are not absolutely necessary if built correctly. Simple Biolets will create their own air circulation and heat through spontaneous exothermic reactions.
7. Good Composting toilet design has a mechanism to turn the waste allowing for good aeration. Foul odors are usually caused by anerobic bacterial growth so good earation will limit the worst orders.
8. Natural Heat production during the composting process will also kill bacteria and limit growth.
9. Adding lime will increase the pH and aid in inhibiting bacterial growth and odors. Bacteria tend to prefer an acidic low pH over a basic high pH.
10. Basically, a Biolet composting toilet deals with human solid waste not unlike kitty litter.
11. Finished waste is sterile and can be burried. Some people add it to soil around flower gardens but I personally wouldn't use it in my veggie garden especially because when you empty the Biolet there will always be the newer waste mixed with the older decomposed waste.
12. Some designs have 3 chambers that are rotated to make sure waste that is emptied is all decomposed and sterile. Other designs empty to an outdoor compost pile to finish the decomposition process.