Cheap, waterless toilet that turns waste into clean water and power to be trialed in Africa

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Nano Membrane toilet prototype(Credit: Cranfield University)

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A cheap, easy to maintain, "green" toilet that uses no water and turns human waste into electricity and clean water will be trialed in 2016, possibly in Ghana. Dubbed the "Nano Membrane Toilet" by its creators from Cranfield University, UK, this new approach to managing waste could help some of the world's 2.3 billion people who have no access to safe, hygienic toilets.

The toilet's magic happens when you close the lid. The bottom of the bowl uses a rotation mechanism to sweep the waste into a sedimentation chamber, which helps block any odors from escaping. The waste is then filtered through a special nanotech membrane, which separates vaporized water molecules from the rest of the waste, helping to prevent pathogens and solids from being carried further by the water.

The vaporized water then travels through to a chamber filled with "nano-coated hydrophilic beads", which helps the water vapor condense and fall into a collection area below. This water is pure enough to be used for household washing and farm irrigation.

The residual solid waste and pathogens are driven by an archimedean screw into a second chamber. This part of the design is still being finalized, but the current plan is for the solid waste to be incinerated to convert it into ash and energy. The energy will power the nanomembrane filtration process, with enough left over to charge mobile phones or other small devices.

The only waste product of the whole process is ash from the burning of solids, which is nutrient-rich and pathogen free, and therefore, usable in farming. The toilet can manage the waste generated by households of up to 10 people.

Funded in part by the Bill & Melinda Gates Foundation's Reinvent the Toilet Challenge, and winner of the CleanEquity Monaco 2015 award, the nano membrane toilet is to be trialed and tested in 2016, possibly in Ghana.

Currently, more than 650 million people in the world do not have access to clean water, and more than 2.3 billion don't have access to a safe, private toilet. Researchers around the world are working to help solve this problem, but high-tech solutions, such as adding solar panels, are usually too expensive to be practical.

Sociological issues also play a role. As toilet infrastructure deteriorates, people prefer to go outside rather than use a smelly room inside their house. This makes women vulnerable to rape, and creates further sanitation and hygiene issues.

The nano membrane toilet is clean, odorless and aspirational, and it should be capable of working in environments that lack sewage, external power and water. So it will be interesting to see how it works in the field.

The plan is for the toilet to be rented to households through a local organization, helping to spread the costs to stay within the Gate Foundation's challenge of keeping the cost of the toilet below US 5 cents per person per day.

If all goes well, the toilet could also find applications elsewhere like the military, construction industry, yachts, or outdoor events.

The video below, created by the Cranfield Water Science Institute, was developed for the Reinvent the toilet fair in 2014. It showcases some earlier ideas of how the toilet could work in the field.

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