Flush the toilet of an average toilet, and you will hear a wet woosh, as if someone is throwing a pot of water on the ground. Flush one of three toilets in a science building at the National Institute of Science and Technology in Ulsan, South Korea, and the sound will be very different: just a dribble of water, almost drowned out by the purring. “We use a vacuum cleaner,” explained Jaeweon Cho, the toilet brain and environmental engineer at the university, in a video describing his invention. Just before pressing the flush button, Cho prepared viewers for a sound that might surprise them; imagine the suction of an airplane toilet, in a place you wouldn’t expect to hear it. “Please don’t be surprised,” Cho said.

Noise isn’t the only unusual thing in Cho’s bathroom. Called BeeVi, a portmanteau of “bee” and “vision,” they use much less water than a typical throne – about a quarter of a gallon for feces and half for urine, compared to up to six gallons in old conventional toilets. Instead of rinsing the waste in pipes that take it to a sewer and a treatment plant, they transport the excrement elsewhere in the building, to digesters where the microbes break it down into a usable product: biogas. Similar vacuum toilets and systems for converting faeces to biogas exist elsewhere, but unlike most sewer services, which end up passing the costs on to consumers through bills, Cho’s toilets pay people to poop.

With each flush, the pipes carry feces, urine and sewage to the basement of the building. From there, the poo travels to a shiny silver digester, where anaerobic bacteria wait. Microbes eat feces and generate methane. Up to one cubic meter of gas is stored in a tank on the first floor; from there, the methane travels around the building in pipes – imagine a buried sewer, but leaner and attached to the walls – ready to heat showers or fire up the stove in an adjacent communal kitchen. The kitchen area overlooks the lab where anaerobic digestion takes place, allowing students and staff to tap into the stored gas and boil a kettle for tea while viewing the equipment that made it possible.

Each poo earns a few units of a currency Cho has dubbed Feces Standard Money, and can use the funds, in person or at an online marketplace, to purchase. all of from coffee and cabbage to life jackets and hand sanitizer.

Reached by email, Cho says that while the transformation of feces into energy “seems strange to the public,” he thinks the notion doesn’t need to bother people. At room temperature, methane is odorless, and Cho’s team filters out the more odorous sulfur early in the gas generation process, so that it does not damage the equipment. “When we use biogas, we rarely smell” odors, according to Cho.

And now is a good time to tinker with ways to improve toilets and sanitation systems. Many toilets today waste a lot, not only in terms of wasted water, but also because they throw away urine and feces, potentially valuable energy and nutrient resources often viewed as “something you want to keep away from.” more possible, ”explains Chelsea. Wald, science journalist and author of Pipe Dreams: The Urgent Global Quest to Transform the Restroom.

Municipal sanitation systems are also old, overloaded and underperforming in many parts of the world; in others, they barely exist. Many sanitation systems are called upon to exceed their weight by serving populations larger than they were designed to support and by intercepting more water than they can support. This is especially true for combined sewers, where materials from homes mix with stormwater washed down the street. It is not uncommon for wet weather to cause overflows, in which sewers dump their smelly contents into bodies of water. Many sewers are designed to work this way, in part as an alternative to backing up people’s basements, but it means some cities are seeing tens of billions of gallons of sewage pouring into waterways. every year. These untreated torrents introduce waste and bacteria that foul local ecosystems.

The BeeVi biogas harvesting program is a small-scale operation, one of many closed-loop concepts around the world that use similar technology. Although some home biogas installations exist, toilets like those in the BeeVi project require expertise to be built, and digesters are not necessarily perfectly suited to the scale of a household. Wald thinks the merit of this particular project is really in the education, shaking up people’s ideas about wastewater and – with the shit-for-pay element – what resources they value.

These toilets will not solve the massive infrastructure problems in our largest wastewater systems. “As societies and communities, we need to be prepared to spend real money” on the big picture, rather than expecting our toilets to pay us, says Wald. American Society of Civil Engineers Annual Infrastructure Report Sheet recently awarded the country’s wastewater treatment operations a D + rating, for example. A handful of redesigned toilets will not increase this score. But, if you’re near Cho’s bathroom, you might as well sit down, then buy a book or a banana for the road.