When the Gates Foundation first announced its $42 million Reinvent the Toilet Challenge I took so much abuse for my post-Gates Foundation Throwing $42 Million Into The Toilet. Fortunately we changed commenting systems and all of them were flushed away. Then the first winner was announced and it confirmed everything I worried about- it was so complex, a standard toilet on top of a sewage system that would be at home on the Space Station.
Now we have another new toilet design from Cranfield University in the U.K., described as “a household scale off-grid toilet which produces clean water and ash.” It’s also been described as a “power-generating ‘super-toilet’ that doesn’t need mains water and can charge your phone.”
© Cranfield University
How Does the Nano Membrane Toilet Work?
I will confess that I have spent quite a few hours trying to figure out how it works; the Cranfield site explains it thusly:
Well, not exactly. The mechanism is clever, maintaining a constant seal, but while you are using it the poop is sitting right under you without any water covering it, and it is going to smell during the process of elimination. Anyone who has used a German shelf-style toilet or a squat toilet will know what I mean. One is not, as they show in their photo, going to put this in your living room. Once you are done and close the lid, it does rotate and seal any smells from below.
The video explains that somehow pure water floats on top of the poop and then filters through the membrane. The blog suggests that “faeces will settle to the bottom of the holding talk and urine will be removed from the top using a weir.”
A description on the SuSanA site describes a vacuum pump to lower pressure, which would create vapour from liquid:
And What’s That About Phone Charging?
Earlier reports on the toilet claimed that “heat from burning the waste produces enough electricity to power the unit, and could even produce a little extra for mobile phone charging” and the drawing shows a “gasifier to combust water (?) and generate power”; The most current version on their site appears to say otherwise:
In fact, the video explains that the poop balls are coated in paraffin wax which are then picked up by the guy with the service contract and taken away to “a locally sited small scale gasifier sized to accommodate around 40 toilets.”
As for the pee that has been separated through those nano-structured membrane walls,
Nano Membrane Toilet Pitfalls
Now the Cranfield team has done a lot of work on this, and has put together a group of serious experts on membranes and other technologies. But I go back to the arguments that I have made since the Gates program started.
Waste Could Be Put to Better Use
Let’s start with the pee; had it been separated in the first place, it could have been used directly for irrigation, and the valuable phosphorus in it could have been put to work. There is absolutely no need to put it through nano this and nano that- it is useful stuff in its original form.
Then there is the poop, also useful stuff. Had it been collected in a standard composting toilet, it could have been used as… compost. Or there are many other designs where the poop is collected and taken to a digester and turned into fuel. I does not need to be dried, turned into little balls and coated with wax. Really.
The Cost
On Gizmag they describe this as “a cheap waterless toilet that turns waste into clean water and power " But lets get real: It will not be cheap; It has batteries and generators and pumps and “nano-coated hydrophilic beads”. It is an extremely high tech device. It has also been over-hyped; everyone is excited by the fact that is purported to charge your phone. It’s clear that the gang at Cranfield University have worked really hard and there is some sophisticated stuff going on here with semipermeable membranes, but it seems that the PR department has got out of control.
Building a toilet shouldn’t be rocket science. But so many of the Reinvent the Toilet Challenge treat it like it is. The Nano Membrane toilet definitely is rocket science and I hope I am wrong, but I fear it will suffer from a failure to launch.
