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From KQED. Welcome back to Forum. I'm Mina Kim. Among the 22 recently announced MacArthur Genius Grant winners is William Tarpe, a chemical engineer at Stanford.

In Tarpe's words, just as an oil refinery takes crude and turns it into many different products, his lab does a similar thing, but with wastewater and in more practical and sustainable ways.

As a MacArthur fellow, Tarpey now has an $800,000 no-strings-attached stipend with which to continue his work.

He joins me now. William, welcome to Forum.

And congratulations on the MacArthur Genius Award.

Thank you so much, Mina. It's great to be here with you.

So tell us first what you mean by turning wastewater into highly useful products.

What do you derive from wastewater?

Sure, yeah.

I think in the name, most of us think of wastewater is something to get rid of and kind of a nuisance at best.

And we try to think about what can we mine

from wastewater. So we can make things like fertilizers, chemicals that are bought and sold. We can make

disinfectants like ammonia that's in household cleaners. And more recently we're trying to recover

basically battery ingredients, lithium, nickel and cobalt from either spent batteries or from

other wastewaters that contain them. Wow. So you developed a way to do this that requires a lot

less energy and infrastructure and even chemicals, I understand. Yes. Yeah. Our big idea here is how to

close the loop is how we think about it. So it's like any process we make, of course, we want to try to reduce the greenhouse gas emissions and the cost and the energy. But even when we do that, there's still another loop to close. So an example would be we've managed to recover ammonia as a fertilizer from different products. But to do that, from different wastewater, sorry, but to do that,

...