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The Bill and Melinda Gates Foundation has begun a “Reinvent the Toilet” competition and awarded $3 million to researchers at eight universities, challenging them to use recent technology to create models that do not need to be connected to sewers, water, and electricity, and that cost less than pennies per person a day to use. Later prizes will include financing for one or more winning prototypes to be tested and produced commercially. About 2.6 billion people without access to sewer-linked systems must use simple latrines, holes in the ground, or just the nearest available spot ― a situation that can lead to many health problems. One of the new toilets being financed by the foundation is a compact chamber that runs on solar power from a roof panel, and uses built-in electrochemical technology to process waste. The California Institute of Technology (Caltech) in Pasadena received$400,000 to develop this solar toilet. It uses the Sun’s energy to power an electrode system in the waste water; the electrodes drive a series of cleansing chemical reactions, converting organic waste in the water into carbon dioxide and producing hydrogen that can be stored in a fuel cell for night operation.