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This gleaming machine turns human poop into fertile soil

Everybody poops, sure. But do we need to use water-based toilets for the job?

This gleaming machine turns human poop into fertile soil
[Photo: Rebecca Schedler]

Every flush of a toilet uses 1 to 6 gallons of water. This wastewater flows through pipes to be treated and purified—3% of U.S. energy use goes to just this. And yet 80% of all wastewater still makes its way back into the environment as a pollutant anyway. When you mix water with feces, you actually just increase its polluting powers.

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But what if your toilet weren’t a toilet at all? What if you could simply feed your waste to mushrooms that would purify it into soil, naturally?

That’s the vision of Rebecca Schedler. As a graduate student at Design Academy Eindhoven in the Netherlands, Schedler built the Symbiopunk, a bioreactor that transforms feces into humus—the fertile, black substance in soil (not the chickpea dip). The work was done in collaboration with the composting toilet company Kildwick.

The Symbiopunk is entirely mechanical, requiring no electricity to operate. You feed solid waste into the Symbiopunk’s large copper drum. (It flips upside down, and spins left to right, to make this job easy.) The waste sits in this copper for two to three days, because over this time feces will actually increase in temperature due to its active microbes. The copper offers a literal cooling-off period, and copper itself is antimicrobial, which helps sterilize the waste.

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[Photo: Rebecca Schedler]
After a few days, the waste makes its way through the black tube you see at the bottom of the contraption. This is a screw feeder. By twisting the white handle, the feeder lifts the waste into the big black tank while also incorporating mycelium (the base organism of a mushroom) into the mix.

Then, after a couple of weeks, mushrooms sprout, purifying and breaking down the waste into humus. Human waste becomes organic fertilizer, which you can then incorporate into a garden or farm.

[Photo: Rebecca Schedler]
Due to COVID-19, Schedler isn’t permitted to test human feces in the machine. Instead, she has tested the Symbiopunk with horse manure to prove its efficacy. She insists that the process stinks less than you’d expect. “I was surprised,” she says. “Most smells are created by introducing [waste] to water. The big advantage from this system is that it doesn’t use water.”

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[Image: courtesy Rebecca Schedler]
According to Schedler, without water, you have less stench, and less cultivation of pathogens that create more of that stench. (Users of dry composting toilets in RVs tend to agree.) You also don’t need to dispose of dirty water, which is a logistical challenge. While, yes, feces does have an odor, Schedler says that the mushrooms do quite a bit to mitigate that.

Schedler isn’t the first person to propose using mycelium to treat waste. In 2018, a student project called the MYCOmmunity Toilet proposed a functional, mycelium-filled toilet that you’d bury when full. Over the course of the month, mycelium would digest the waste, working it back into the earth as fertilizer.

The MYCOmmunity Toilet suggests that waste is a problem we can bury. Symbiopunk insists the exact opposite. Symbiopunk is large and eye-catching by design. You are supposed to look at it and consider the issue of human waste. Its metal knobs and finishes are also intentionally overt, evoking the admittedly passé steampunk aesthetic—again, to make a point.

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“Steampunk had this advantage to reimagine the past to show a different future,” Schedler says. With Symbiopunk, she wants to question the advancements of our industrial age. Her alternative future is this low-fi, metal series of tubes and hoppers, which require no electricity or fossil fuels to operate. Instead, Symbiopunk asks only for your feces and your muscle power. You invest in the process of cleaning up after yourself, and strengthen our environment along the way.

“You really need to deal with your own shit,” Schedler says. “It’s not disappearing, you need to take care of it, what comes out of you. You need to take care of a different living organism, and doing that, you also take care of yourself. It’s a loop . . . it’s not as easy as pushing a button and then it disappears.”

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About the author

Mark Wilson is a senior writer at Fast Company who has written about design, technology, and culture for almost 15 years. His work has appeared at Gizmodo, Kotaku, PopMech, PopSci, Esquire, American Photo and Lucky Peach

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