I just traveled halfway around the world to look at a toilet.

If you’re a long-time reader of TGN, this shouldn’t come as a surprise. There are few things I love talking about more. Sanitation is one of the most important issues we work on. I even drank water made from human feces a couple years ago.

That’s why I’m so excited to visit Beijing, China this week for the Reinvented Toilet Expo, where some of the most high-tech toilets in the world will be on display.

The toilets at the expo aren’t just fascinating gadgets—they have the potential to save millions of lives. More than half of the world’s population uses unsafe sanitation facilities. Even in places where people have access to toilets or pit latrines, their waste isn’t disposed of safely. The pathogens from the waste find their way into the local water supply and makes people sick.

The diseases caused by contaminated water kill more than 500,000 children under five every year. Those who survive are often too sick to go to school. It’s no exaggeration to say that poor sanitation holds back whole communities and entire nations.

If you live in a level 3 or 4 country, you can thank your sewer system for keeping you safe. Sewers have historically been the best way to make sure waste isn’t releasing harmful pathogens into the environment.

But what if you didn’t need a sewer to keep people safe? What if your toilet could dispose of waste all on its own?

Here in China, I get to see this and several other amazing new inventions that could deliver on the promise of sewer-less toilets.

Our foundation has invested a lot of money to develop a pipeline of next-generation sanitation solutions. In 2011, we launched the Reinvent the Toilet challenge. Many of the solutions created for that challenge are now ready to license. A remarkable cohort of engineers, scientists, companies, and universities around the world has done the hard work of getting a safe, off-grid sanitation market ready for take-off. My hope is that this week’s showcase moves their hard work one step closer to being used by real people around the world.

Each of these toilets seeks to solve the same problem, but they’ve all taken a different approach to get there. (The video above explains what specifically makes each toilet special.) Several run on solar power, so they can operate off-grid.

Others generate their own power, like the Cranfield nanomembrane toilet. Opening or closing its lid moves a screw that separates liquids from solids. A gasifier converts the solids into ash and heat that is used to operate the toilet.

A big theme for next-gen toilets is the ability to turn waste into something useful. The Ecosan extracts clean water, which is safe to use for hand-washing. The water created by Duke University’s neighborhood treatment system can be used to flush toilets or supplement fertilizer. The University of South Florida’s New Generator even collects methane gas for cooking or heating.

Another common feature involves burning waste to get rid of it (I apologize if you’re eating right now, but there’s no delicate way to describe this). The Janicki Firelight dries out urine and feces, turning them into sterile ash and water.

As you might have guessed, these toilets are a lot more complicated than your average toilet. Just look at the maintenance panel used to operate a public restroom:

The user experience for each is more or less the same as any other toilet, though. Most of the magic happens behind the scenes.

I know most people wouldn’t describe what toilets do as magical, but I think it’s true in this case. Think about it: the toilet hasn’t really changed in more than a century. If you could go back in time to the mid-1800s, you’d find flush toilets that work basically the same as the toilet in your home. And if you live somewhere with pit latrines, toilet design has stayed the same for even longer.

The toilets on display here in Beijing might one day replace a piece of technology that’s been with us for ages—and they could save millions of lives in the process.