We take toilets for granted. Everyone has at least one; most people have more, at least in developed nations. But we forget that in many places in the world, toilets are a non-existent luxury, and many people get by with buckets or holes in the ground. This presents a sanitary hazard; not only is it smelly and unpleasant, it can lead to infectious bacterial diseases like cholera, typhoid and dysentery. By some estimates, more than two and a half billion people in the world have no access to toilets. The World Health Organization estimates that 1.5 million children each year die from diarrhea from diseases resulting from a lack of sanitation.

The Bill & Melinda Gates foundation would like to change this: by redesigning the humble toilet and making it more accessible to people in developing nations. According to an article in Scientific American, the Foundation is presenting several hygienic innovations developed through its Reinventing the Toilet Challenge. Last year, the Foundation began offering $3 million in grants to engineering teams at eight research institutions in North America, Asia, Africa and Europe, including the California Institute of Technology, South Africa's University of KwaZulu–Natal and National University of Singapore. Eight institutions responded and signed on to the challenge.

According to the Scientific American article, several prototypes have been proposed, including one from Delft University of Technology in the Netherlands that uses microwaves to turn human waste into carbon monoxide and hydrogen, which could then be stored in solid-oxide fuel stacks to generate electricity. Engineers at Loughborough University in England and Stanford University are both reportedly working on a process that turns human waste into charcoal, or biochar. Engineers at the University of Toronto have established a process that sterilizes and dehydrates feces and decontaminates urine via membrane filtration and ultraviolet radiation. Caltech engineers have reportedly proposed a solar-powered toilet that generates hydrogen for fuel cells from the waste, solving an energy problem at the same time it safely disposes of human waste.

But the Foundation stresses that it's about more than just technology, it can be a cultural issue, as well. In cultures where toilets are unknown, they are often unwanted, and efforts to build latrines in remote areas of developing nations are often scorned and rejected. In those cases, efforts need to be made to educate the population about the disease risks of open sewers and uncontained human waste.