Toilet tech proves that where there's muck there's brass
Nearly a third of the world's population still has no access to safe, hygienic sanitation. This means they have to go the toilet out in the open - in the bush, fields or forests.
This leads to about 700,000 deaths each year from related diseases, says the World Bank, and stops children getting a proper education.
"Sanitation lies at the root of many other development challenges, as poor sanitation impacts public health, education, and the environment," says Jyoti Shukla, senior manager of the World Bank's Water and Sanitation Program (WSP).
So what are the technology innovations helping to address this issue, and is the private sector better placed than the public sector to implement these solutions?
One of the United Nations' Sustainable Development Goals is to make universal access to safe sanitation and water a reality by 2030.
"The stakes are high: stunting and malnutrition are directly related to poor sanitation; quality of learning and productivity is affected by sanitation; and dignity and empowerment of women and girls is influenced by how we deliver sanitation," says Ms Shukla.
But many in the private tech sector believe this cannot be achieved without their help.
For example, Kenya-based Sanivation is on a mission to make toilets "cool", according to chief executive Andrew Foote. His firm has come up with a way of transforming human waste into energy briquettes.
The company provides hygienic toilet units to households in slums and refugee camps. The waste is collected once a week and taken away to be treated and transformed into charcoal at a special facility.
Sanivation sells this back to communities as a source of energy that is safer to burn than traditional charcoal.
At the processing plant, the waste is put into solar concentrators, which focus energy from the sun to heat the waste to temperatures over 70C (158F) for many hours. This deactivates pathogens, and renders the waste safe for reuse.
The treated waste is then mixed with biomass agricultural residue - rice husks, flower stems, corn cobs, and the like - which has also been heated and ground into charcoal dust.
The two waste streams are then combined and compressed into charcoal blocks.
"Simply to achieve universal sanitation, toilets will have to mimic the adoption rates of cell phones, says Mr Foote. "One of my favourite parts of my job is thinking: How do I make toilets as cool as cell phones?"
The private sector treats sanitation as a business opportunity and this is potentially more effective than aid-based hand-outs, Mr Foote believes.
Another firm adopting the private sector model is Kenya's Sanergy, It installs what it calls Fresh Life Toilets in informal settlements, and sells them - at cost - to local entrepreneurs who create mini-businesses out of each toilet.
Fresh Life Operators charge a nominal fee per use of their toilet, but over the year end up making a tidy living. They often hire toilet attendants, and run their unit as a business.
Sanergy removes the waste from the units, treats it, and sells by-products to the agricultural sector.
The company has to date installed 781 Fresh Life Toilets run by 387 operators in eight settlements around Nairobi. Sanergy says it collects nine tonnes of waste a day.
"Investment in private sector sanitation solutions allows for innovation that can't be undertaken in the more risk-averse public sector," says Medora Brown, Sanergy's communications manager.
In sub-Saharan Africa, traditional sewered sanitation systems cost about $56 per capita, whereas Sanergy's model costs $7 per capita, says Ms Brown.
And that's one of the main barriers blocking faster adoption of more effective, life-saving sanitation systems - cost and the difficulties of implementing them at scale.
The Gates Foundation's Reinvent the Toilet competition, launched in 2011, has come up with 24 different types of innovative toilet technologies aiming to transform waste into either clean water or energy. Technology of Business has reported on some of the more promising ideas before.
In 2012, Dr Michael Hoffmann, professor of environment science and engineering at the California Institute of Technology (CalTech), was awarded $100,000 (£70,000) by the Foundation for his team's solar-powered loo.
It uses an electrochemical reactor to break down human waste into fertiliser and hydrogen gas, which can then be stored in electric fuel cells. The treated water can be reused to flush the loo or irrigate crops.
A panel of photovoltaic cells captures light and converts it into electricity stored in rechargeable batteries. One day's light can produce enough power to run the entire electrochemical sanitation system night and day.
Another promising idea came from the University of Loughborough, which designed a toilet that brings the waste to a high enough pressure and temperature to kill all the pathogens, while releasing a lot of the energy in the process as heat. This heat can then be captured and used to help power the next processing cycle.
But a Gates Foundation spokesman, admits that bringing such hi-tech innovations to fruition is hugely difficult in developing countries without established sewerage systems or skilled maintenance people.
Three years after winning their prizes, the CalTech and Loughborough ideas are still being tested and evaluated.
"By this time next year, we will have valuable test data and user feedback on these designs, and we expect we will have commercial partners building launch plans for the first wave of Reinvented Toilets," the spokesman says.
The problem is that while such innovations are tested, more people are dying from diseases associated with poor sanitation.
And the problem is likely to get worse.
"Lots of progress is being made," says Sanivation's Mr Foote. "The bad news is that with rates of urbanisation and population growth, despite the efforts of many actors, the number of people lacking access to sanitation in sub-Saharan Africa and in urban areas has actually been increasing in the last 10 years."
Technology can only do so much. Solving the world's deadly sanitation problem will take a concerted effort from all sectors working together.
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