变城市污水为农田之宝

AUDIE CORNISH, HOST: While most Americans contribute to agriculture by buying food at stores and restaurants, about half of us make an additional donation in the form of fertilizer. With spring at hand, farmers are getting ready for planting. That means enriching the soil.

And as Frank Morris, of member station KCUR reports, it may just involve you.

FRANK MORRIS, BYLINE: Here in this bathroom, in busy gas station in Kansas City North, you're reminded that while this place is a major distribution point for fuel, food and drinks, it's also a big collection point for something else.

(SOUNDBITE OF FLUSHING TOILET)

STEVE ZUHLKE: I'd say we're probably running about 70 million gallons a day right now.

MORRIS: In Kansas City, almost all toilets lead here, to a treatment plant where engineer Steve Zuhkle is monitoring the flow.

ZUHLKE: It's got a little, earthy smell to it.

MORRIS: The city runs much of the heavier goop through a process called anaerobic digestion, and then pipes it out to its own farm.

TIM WALTERS: We are down next to the Missouri River. We have 1,350 acres of really good bottom land soil.

MORRIS: Tim Walters is the chief agronomist for Kansas City, the municipal farmer, so to speak. He's got this spread plumbed with what could be mistaken for sewer mains, except these pipes don't collect smelly stuff. They disperse it.

Thick jets of processed sewage arc out 40 or 50 feet from giant, moving sprayers.

WALTERS: It's black. It's black gold. It looks like grease. It doesn't smell like grease but it looks like grease. And when you get it on you, it's hard to get off.

MORRIS: It's also packed with nutrients good for the corn and soybeans that Walters grows here, generating almost half a million dollars in profits for the city each year. Walters figures the free fertilizer is worth nearly $200,000 year. And he'd use more of it, if he could get it.

WALTERS: Every year we typically run out. They can't digest enough. They can't get enough down to us.

MORRIS: The city's two digesters run all the time but can't keep up with Walters' demand, let alone the city's supply. Still, more than half the processed sludge, or biosolids, is put to use, which makes Kansas City just about average for the U.S., according to Ned Beecher.

NED BEECHER: It's actually been a pretty routine practice in a lot of places. In the U.S., about 55 percent of the sewage sludge that's produced at wastewater treatment plants is recycled as biosolids.

MORRIS: Beecher heads the North East Biosolids and Residuals Association. He says cities across the country - from Boston to Chicago to L.A. - sell or use most, if not all, their human waste to fertilize plants.

BEECHER: Hay and corn, but it's also used on soybeans, on wheat, on hops for beer, on grapes.

MORRIS: But Milwaukee wins the award.

JAMIE STAUFENBEIL: Milorganite has been doing this for over 86 years.

MORRIS: Jamie Staufenbeil markets Milorganite, a lawn and garden fertilizer made from sewage collected in Milwaukee. She says the city refines this stuff so much that it's safe for any kind of use.

STAUFENBEIL: We just reached nine billion pounds of Milorgonite sold into the marketplace.

MORRIS: With profits lowering sewer fees for Milwaukee residents. Hundreds of waste water treatment plants collect methane and burn it for energy. But even with all the well-established, beneficial, and even lucrative ways to dispose of solid waste, a lot of it still ends up in landfills or being processed at big, industrial incinerators, like this one in Kansas City.

(SOUNDBITE OF MACHINERY)

UNIDENTIFIED MAN: Watch out. Watch out.

SHAUN O'KELLEY: It's basically a Roman arch structure, eight floors.

MORRIS: Shaun O'Kelley runs this incineration facility, burning human waste down to a fine ash and using lots of natural gas, electricity and manpower to do it. The incinerator no longer runs all the time, but O'Kelley is about to fire it up again, because for now, here, burning some human waste is cheaper than recycling all of it.

O'KELLEY: Land application has its challenges, too. The USDA, the EPA, you know, with the regulations. Plus, you have to have the land available and the capital to invest in that property. Always economics - it's always money.

MORRIS: Biogas and biosolids are also hard on machinery. And, well, there's the smell. Residents aren't always pleased about having an expanding biosolids application program in their backyard. So the drive make good use of human waste has been largely stalled for years. And despite a steady stream of innovations, almost half of it is still wasted.

For NPR News, I'm Frank Morris in Kansas City.