An estimated 2.5 billion people still lack access to proper sanitation and the Gates Foundation has put a lot of resources into trying to do something about it. Through the Reinvent the Toilet Challenge and other initiatives, it’s funded dozens of projects, including the Omniprocessor sewage plant that Bill Gates visited last year (famously, he drank water that had been purified from poop).
The Nano Membrane Toilet being developed at Cranfield University, in the U.K., is another Gates baby. And pretty impressive it is too. A self-contained system that needs no additional water to operate, it converts human waste into useable water and an inert, pathogen-free ash. It could allow people to meet their sanitation needs without needing to be connected to a sewage network; to generate additional clean water for the home; and to dispose of the residue in the normal garbage.
Here is how it works: Once you’ve done your business, you close the lid, and the toilet bowl inside rotates, taking the waste downwards and creating a “smell barrier” between you and your doings. A scraper keeps the drum clean, sending the waste down to a collection tank, where the solids fall to the bottom and the liquid is passed through a fine membrane. That extracts just the water molecules, which are then vaporized and condensed using some hydrophilic beads (this process also takes out the bugs).
The cleaned liquid is then channeled to a tank at the bottom, from where it can be reused for washing, watering plants, and even for drinking. Meanwhile, the sludge at the bottom of the tank is carried away, covered in a wax, and gasified to several hundred degrees, so it becomes ash. The most innovative part of all is that the feces itself is a fuel source: poo is used to dispose of poo.
At the moment, the toilet is still a lab prototype and has yet to be tested in real-life situations. The team behind the toilet is currently scoping out potential test sites. “We are still at the early trials stage and some of the other media reports have maybe been misleading. We will be commencing human tests shortly,” says Alison Parker, a lecturer with Cranfield’s Water Science Institute.
Cranfield has also yet to work out how much the toilet might cost, or exactly what its business model might be. But it’s working to the Gates Foundation’s target of sanitation for five cents a day per person, and it’s likely the toilet will be rented out, with maintenance included in the contract.
“Our toilet is ideal for urban environments where pit latrines are not proving adequate,” Parker says. “In rural areas, you can still build a pit and when it fills up, you can cover it up and dig a new pit and move your structure over. That’s a satisfactory solution. In urban areas, the amount of land per family is shockingly low and you can’t move the pit, and so you have to empty it.”
“Our model envisions a maintenance technician being able to regularly visit in a defined geographic area. For that to happen, it needs in an area where traveling times are short, not a remote rural area where it could be hours between locations.”
Some have questioned Gates’s focus on high-tech solutions. The world doesn’t need fancy new mechanisms, say critics. It needs reliable toilets kept clean and tidy, so people want to use them. In contrast to the technology promoted by Gates, toilet start-ups like Sanergy and Sanivation emphasize the service side of things and try to get local people as involved as possible. That’s important, as research shows that simply building toilets for people doesn’t necessarily mean they’ll use them. In other words, there are cultural barriers to improved sanitation as well as technological ones.
This isn’t to take away from the cleverness of Cranfield’s technology, though, and Parker insists the toilet fills a need in urban environments. “People have been developing cheap toilets for years and years. The obvious example is the pit latrine. I think Bill Gates was correct to try and seek a different technology to solve the sanitation crisis. The low-tech options are not always working to provide sanitation for everyone,” she says.