ends up? >> yep. >> reporter: this piece of infrastructure as a whole, is probably one of the most important pieces of infrastructure. >> without hyperion, l.a. will not work. you can talk about the sunshine, the transit system. l.a. would not work if we did not have hyperion. it's an underappreciated engineering marvel. there it is, the smell. >> reporter: you like that smell? >> it is, to me, that is the smell of a city working. >> reporter: it's the smell of a future, in a way. >> yes. to all of us. a majority of human beings live in cities. so many cities around the world, when i talk to my fellow mayors don't have this yet and need it. i think, you know, cities can't grow and can't work without basics. also, what we're confronting with our environmental crisis, is not just about heating and current. it's about health. if you can't take care of sewage, disease spreads and pandemics can come about.