This off-grid toilet uses sand and a treadmill to “flush” your bus


You may not think about it when doing your morning business, but more than 1.7 billion people still lack basic sanitation services, such as private toilets or shared latrines. Nearly 500 million people still practice open defecation (yes, that’s open poo), 92% of whom live in rural areas.

That’s why Archie Read, a recent graduate from Brunel University London, designed Sandi. The toilets use a mechanical flush (no electricity), a basic treadmill to flush solids (no water), and a separator inside the bowl that separates waste streams so that they can be used as independent fertilizers. For now, Sandi is just a concept with a prototype, but if it hits the market, it could work off-grid, making it a viable and dignified solution for rural families without water, septic tanks or sewers. systems.

[Image: courtesy Archie Read]

Read, who graduated with an engineering degree in product design, came up with the idea during a recent internship in Madagascar. He worked for toilet company LooWatt, which captures waste in a biodegradable polymer film but requires regular maintenance. “It’s a great product, but like all other sustainable designed toilets, it’s targeting cities,” Read says.

[Image: courtesy Archie Read]

Sandi joins a growing ecosystem of off-grid toilets that run the gamut from something like a potty training toilet and comes with a single-use biodegradable bag, to a glorified bucket with a lid, to a toilet technology that uses nanotechnology to convert human waste into clean water and ash without using energy. Like Sandi, these toilets don’t need water to work, but most of them (except the last one) don’t flush at all, which Read describes as “a safe but not pleasant experience. “.

[Image: courtesy Archie Read]

This is where Sandi comes in. The toilet bowl has two separate compartments: one guides urine into a container below; the other has a simple treadmill covered in a thin layer of sand that renews itself with each hunt. Read opted for sand because it keeps the droppings from sticking to the conveyor belt, but he says sawdust or dirt would work just as well. (The prototype test involved instant mashed potatoes mixed with various amounts of water.)

[Image: courtesy Archie Read]

When you’re done, you press down on the flush handle, which swings the treadmill out of sight and deposits your belongings in a separate container below. For a household of 7, he says the liquid container should be emptied every two days, while the solid container should be emptied after four days. After that, people can immediately use the urine as fertilizer and bury the rest to use as compost four weeks later.

The key here is that the whole operation is low-tech in design. “If you have a beautiful, complex electrical component and you’re in a village 80 km from any technician who can fix it, you can’t expect him to travel 50 km to fix a toilet.” Read says. “It must be in a situation that can be fixed by 90% of people themselves.”

It’s too early to talk about logistics, but for now, Reed has priced the product at $74 per unit, which puts it somewhere in the middle of its competitors. Eventually, he plans to work with NGOs who could buy or rent the toilets and educate people about safe sanitation in the process. “If your main priority is security, you can’t charge people a fortune,” he says. “It’s not like you’re selling a luxury product.”


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