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Reinventing the toilet for 2.5 billion in need.

High-tech toilets for tackling the growing public health problem of human waste are gaining increasing attention. But, as Gary Humphreys reports, low-tech solutions may be more practical in poor countries. Professor Karl Linden of the University of Colorado, Boulder, in the United States, is understandably proud of his team's toilet. It looks like a missile tracking system and makes human faeces and urine disappear; or, to be more precise, turns solid waste into biological charcoal, a material known as bio-char that can be safely used as a fuel or fertilizer, while urine-infused bio-char can be used as a nitrogen-rich fertilizer. "Nothing harmful is left over," says Linden. "There are no by-products, no germs, nothing." The Sol-Char toilet is one of the winners of the Bill & Melinda Gates Foundations Reinvent The Toilet Challenge, a competition launched in 2011 to encourage the development of technological solutions that will bring safe, affordable sanitation to the 2.5 billion people worldwide estimated to be without it. In the first three years of the competition, 16 grants were disbursed. One, for example, went to a University of Bristol team, to develop a urinal that transforms human waste into electricity. Another went to Swiss aquatic institute EAWAG for a toilet that stores urine and faeces for energy recovery, and another to RTI International in the USA for a model that disinfects urine, dries and burns waste and converts this into stored electricity. [ILLUSTRATION OMITTED] Recently the Gates Foundation joined forces with India's Biotechnology Industry Research Assistance Council to pick six teams of researchers from India, who are developing several models, including a solar-powered toilet with an in-built waste processing capability and a toilet that uses ultrasound to reduce water wastage. "The idea of the challenge isn't simply to come up with better toilets, but to invent new ideas and new approaches to dealing with human waste," explains Gates Foundation sanitation expert Jan-Willem Rosenboom, who has 30 years' experience of working on sanitation solutions in the field. Prior to joining Gates, Rosenboom worked for Oxfam and the United Nations Children's Fund (UNICEF). The Gates Foundation initiative is laudable and addresses a serious problem. According to Bruce Gordon, acting coordinator of the Water, Sanitation, Hygiene and Health unit at the World Health Organization (WHO) in Geneva, the lack of access to safe, clean sanitation currently puts an estimated 2.5 billion people at risk of many diseases including dysentery, cholera, typhoid, schistosomiasis, trachoma and intestinal worms. An estimated 645 000 children under five die every year from diarrhoea--a preventable, sanitation-related disease. "Progress on the issue has been disappointing," Gordon says, noting that the Millennium Development Goal (MDG) sanitation target to halve the proportion of the global population without access from around 50% in 1990 to 25% in 2015 is unlikely to be met, while the number of people practising open defecation--usually because they have no other option--has fallen by only 21% over the past two decades to around one billion in 2012. "Achieving universal access to basic drinking water sources appears to be in reach, but we will not achieve universal access to basic sanitation without some fundamental change," Gordon says. Is reinventing the toilet the way to achieve that change? Rosenboom thinks so, but has no illusions about the size of the challenge faced, a challenge reflected in the stringent selection criteria of the Reinvent the Toilet Challenge competition. The winning toilets are supposed to remove germs from waste, recover valuable resources such as energy, clean water and nutrients, without being connected to water, sewer or electrical mains. They should be cheap--less than 5 cents per user per day (US$ 0.05)--and suitable for promoting sustainable and profitable sanitation services and businesses that can operate in poor, urban settings. …