Toilets that recycle human waste

Posted on 11 May 2016.

Scientists have devised a no-water flush toilet that recycles human waste. It’s the toilet of the future and it protects the environment and health.

In developed countries, going to the bathroom is as simple as turning on a light or having a drink of water from the faucet. But it isn’t the case everywhere. 2.5 billion people defecate in the open or do not have access to adequate sanitation. 2.1 billion city dwellers use poor quality facilities. The consequences for human health and the environment are devastating. Which is why the Bill & Melinda Gates Foundation launched the "Reinvent the Toilet Challenge". The goal? To support the most ambitious projects and so provide universal access to safe and sustainable sanitation services. To receive grants under the program, the toilet of the future has to fulfill several criteria: efficiently remove germs from human waste and recover resources; operate "off grid" without connections to water, sewer or electrical lines; cost less than 5 cents per user per day; promote sustainable and financially profitable sanitation services and businesses that operate in poor, urban settings.

The Nano Membrane Toilet designed by Britain’s Cranfield University meets all these criteria.

And thanks to funding from the Gates Foundation - $700,000 - the team of researchers has developed an innovative no-flush toilet prototype whose operation is as complex as it is ingenious.

The flush uses a unique rotating mechanism to transport the urine and feces into the toilet without demanding water. The solids are separated by sedimentation. Loosely bound water (mostly from urine) is separated using low glass transition temperature hollow-fiber membranes. The unique nanostructured membrane wall facilitates water transport in the vapor state rather than as a liquid state which eliminates pathogens. Nano-coated beads recover the water vapor by condensation. The filtered water can then be reused for various domestic purposes such as cleaning or watering plants. After being drained, the solid waste is stored in an airtight compartment and covered with a nanopolymer coating to block any bad smells and prevent the transmission of germs. Without water, the Cranfield University super toilet doesn’t need electricity either. It is powered by pedal power or with a crank – a hand crank is supplied that can also be used to recharge small electronic devices such as a mobile phone or a flashlight.

Every week, a technician collects the solid waste and takes it to a locally sited small scale gasifier - or it can be sold as fertilizer. The Nano Membrane Toilet therefore not only recycles water and feces, but also provides additional income to the local people responsible for maintenance. The first ones are likely to be installed in Ghana this year, and will improve the living conditions and health of hundreds of people!