A poop vaporizing toilet to solve the sanitation problem

Wet oxidation could be an effective way to treat human waste.

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Hygienic sanitation facilities are crucial for public health. Around 68% of the world’s population i.e. 5.0 billion people used at least a basic sanitation service. While there are 2.3 billion people, who still do not have access to safe and affordable sanitation systems, according to WHO. It means they have to put themselves in an unhealthy, uncomfortable or dangerous situation, every time they go to the bathroom.

Bill and Melinda Gates Foundation believes that this problem can be solved by innovation technologies. Through their ‘Reinvent The Toilet Challenge’, the foundation has recruited scientists and engineers from around the world to make new types of toilets and public sanitation systems for places that can’t afford modern upgrades.

New Zealand-based Scion Research, one of those companies that are funded by the foundation, is developing a new type of toilet that used pressure and microwave technology to treat sewage right in people’s homes.

We get to flush here and it gets out of our household and treated and discharged into the environment and we’re removed from the issue so we don’t have to handle it personally or live amongst it. In a large part of the developing world that’s not the case. Their proximity to their waste is constant and the risk of disease is high,” says Daniel Gapes, an environmental engineer working on the project.

The Scion Research team uses a technology that is fairly well known in large-scale applications, but it is used in mining and also in sewage treatment. The method is called wet oxidation.

A working prototype graphic
A working prototype graphic

Wet oxidation is a hydrothermal treatment process that uses oxygen, heat, and pressure to breakdown materials. It can destroy toilet waste solids and completely kill pathogens by oxidizing organics and oxidizable inorganic components at temperatures between 150 to 374°C and pressures between 0.5-20 MPa.

What would happen in that environment over a period of an hour is that organic material will oxidize. It gets converted to carbon dioxide and water. Just heating under oxygen pressure. It’s quite amazing,” says Gapes.

This byproduct is completely sterile – a clear liquid that can be treated and passed through a filtration membrane to produce purified water and ash that contains a high content of phosphorous, a chemical element used in fertilizer.

The biggest challenge that the team has faced was to create a small household system that contains heat and pressure in a way that is safe to have in a residence.

Mechanical Design Engineer Rob Whitton leads the engineering of the prototype.
Mechanical Design Engineer Rob Whitton leads the engineering of the prototype.

Now, the team is working on developing a microwave reactor. Microwaves are good at quickly and directly heating the waste material, rather than the reactor body itself. The microwave reactor can heat the waste material to 260ºC with speed, yet the technology has not been adopted by any of the other parties in the Reinvent the Toilet Challenge so far.

Using different and unique technology allows us to add something new to the collective knowledge of the toilet challenge parties. We could potentially provide a solution that might benefit another one of the parties,” explains Dr. John Andrews, who leads Scion’s toilet team. “We work collaboratively because we’re all working on the same problem.”

Actually, the Gate Foundation’s challenge was to create a toilet without piped-in water, a sewer connection, or outside electricity – all for less than US$ 0.05 cents per user per day. Gapes says ideally when finished it will cost even less than that. “It needs to feel like a regular toilet,” says Gapes. “The challenge is really high.”

This technology has shown great promise for treating human waste, whether it be in developing countries around the world, New Zealand’s cities, backcountry, or in global disaster zones.