The flush toilet is sanitary, convenient -- and needs lots of water. The problem is, that design only works if you have a functioning sewage system and access to a steady water supply. Those conditions often aren't met in the developing world.
The Bill and Melinda Gates Foundation recently hosted the "Reinvent the Toilet" fair, looking for alternatives to the type richer nations are familiar with. Contestants had to come up with systems that use a lot less water and crucially, can work in areas where power and sewage systems might not be an option. For developing nations toilets can be important -- millions are infected with water-borne diseases every year, such as cholera, and diarrhea can kill you if it dehydrates enough. In many countries the pit latrine is the standard, and the problem is they often leak into local water supplies.
First prize and $100,000 was awarded to the California Institute of Technology for their design: a tall blue contraption that is a self-contained, solar-powered toilet and wastewater treatment system.
A solar panel produces power to run an electrochemical reactor, breaking down water and human waste into hydrogen gas. This system would process all of the waste a family can produce. It also sanitizes the water. Part of the process is disinfecting the waste, because it isn't the waste that causes disease -- it's the bacteria in it. The demonstration model (pictured) works with "squat" toilets, waterless urinals and more traditional-looking versions.
The hydrogen gas can be stored for use in fuel cells or burned to power the system when there is no sunlight, or even for cooking. The water used is recycled, so it can flush repeatedly. The whole thing doesn't depend on outside sources of power or water.
The next step is to find ways to sanitize the sludge and lower the cost of materials so this can be adapted to single households.