A group of students from MIT’s business, architecture and engineering schools recently threw open the toilet.

The toilet they threw open is Sanergy, a year-old for-profit social enterprise that manufactures high-quality, yet low-cost and compact toilets for urban slums in the developing world and then uses human waste to produce energy and fertilizer. It is an “affordable, accessible and hygienic sanitation” solution for millions that live in places without sewage or electricity. They are places where the street is the bathroom. And that’s precisely the problem.

According to the World Toilet Organization, 2.5 billion people worldwide lack access to a toilet. Relieving themselves in rivers, roadsides and impromptu and poorly built latrines, this results in high levels of disease, notably diarrhea and cholera. The recent cholera scourge in Haiti that killed thousands is sobering evidence. It is estimated that 1.6 million children die as a result of these diseases. Statistics show that hundreds of millions lose approximately 60 days of work.

Sanergy produces toilets that are franchised to local operators who charge around $0.06 per use. Currently the company has two toilets serving approximately 150 each day. One is at Bridge International school (a for-profit school supported by the Omidyar Network), the other in Kibera, Kenya’s largest slum. These local operators keep all revenues. That, Auerbach says, is an incentive for them to clean, maintain and “market” the toilets. The operators then work with groups who collect the waste daily and bring it to facilities where it is converted to energy. “The waste from each toilet generates Sanergy revenues of $1250 per year.” The waste from 10 million creates a potential market of $178 million per year. Brown gold.