* Illustration: Leandro Castelao * Picture the lobby atrium of a new, green building, one filled with leafy plants and trees. Now imagine that those trees are growing in waste collected from the building's toilets.

If that idea has the whiff of failure about it, well, sniff again. Increasingly, building designers are managing sewage in-house—really in-house. The Port of Portland, for example, is integrating waste management into the lobby of its new headquarters under construction. The Living Machine uses soil and bacteria to filter out pathogens, essentially turning wastewater into nonpotable water. But the signature element of the system is the plant life that grows up and out of it—right into the lobby. "It's going to provide a kind of greenhouse feel," says Greg Sparks, engineering design manager for the port. "It'll soften the hard edges of the typical office building."

Everybody likes trees, but (aesthetics aside) sending poop from the bathroom to the lobby may seem sort of icky. In environmental terms, though, it's a solid choice. Just as photovoltaics can help take a building off the power grid, living machines take strain off the pipes and municipal wastewater facilities on the "sewage grid." They also show that being green means thinking more creatively about our brown and yellow.

1 Wastewater from the entire building flows into a holding tank where solids settle, like in a septic tank. The reclaimed liquid up top gets pumped to the lobby.

2 Garden-like "wetland cells" layered with plants, soil, and rocks collect the water and capture biological compounds and pathogens.

3 On its way out of the garden, the water is further sterilized by ultraviolet light in the pipes. Then it's recycled back into the plumbing system.

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