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Public Radio's Environmental News Magazine (follow us on Google News)

Wastewater to Energy

Air Date: Week of

Caption: Workers restore a sewage pipe built in 1905. The wastewater running through here hovers around 65 degrees. King County wants to harness that heat energy to use in buildings. (Photo: Ashley Ahearn)

King County in Washington wants to be among the first regions in the nation to tap wastewater to use for energy in buildings. Ashley Ahearn of the public media collaborative Earthfix describes how it would work.


CURWOOD: It's Living on Earth, I'm Steve Curwood. About 350 billion kilowatt hours of energy are flushed down drains in the form of warm wastewater every year, says the US Department of Energy. And one county in Washington State hopes to be among the first in the nation to try to harness that wasted heat and use it in buildings. Ashley Ahearn of the public media collaborative EarthFix reports.


AHEARN: Jessie Israel looks down into an open sewage pipe at a construction site near Discovery Park. She handles resource recovery for King County's Wastewater Utility. Stinky water rushes beneath the construction worker's feet below us. But Israel doesn't think about it as stinky water.

ISRAEL: The vast majority of what's going out to the plant is water from running our laundry, the sink, it's from your shower this morning. We flush a lot of hot water, a lot of energy down the drain and you can see it right here, we're trying to figure out how to capture that and use it in buildings.

Jessie Israel is the Resource Recovery Section Manager for King County’s Wastewater Utility in Washington. Instead of warm stinky water, she sees untapped energy beneath the streets. (Photo: Ashley Ahearn)

AHEARN: Israel sees that warm sewage water as energy. The average temperature of the water rushing through this pipe, and hundreds of miles of sewage and wastewater pipes in the county, is a pretty constant 65 degrees. King County is looking for partners in the private sector who want to harness that heat and use it in buildings.

ISRAEL: We're essentially going to match-make places where we have pipes full of sewage, full of all that hot water, next to a piece of developable land, with a developer that is a deep green developer who wants to innovate and integrate new technologies.

AHEARN: To be clear: King County is not paying the contractors. They're just offering them access to their pipes. And they are one of the first counties in the nation to do so. Another point of clarification: warm sewage water is not getting funneled around buildings to provide heat.

Lynn Mueller owns a company in Vancouver, BC that installs systems to extract heat energy from wastewater. He says in order to understand this, picture your refrigerator.

MUELLER: So you know how your fridge works, you put warm beer in the fridge, pretty soon the beer is cold and the back of your fridge is warm? You've moved heat from that warm material in the fridge to outside of the fridge and that's basically exactly the same system - it's a heat pump.

Workers restore a sewage pipe built in 1905. The wastewater running through here hovers around 65 degrees. King County wants to harness that heat energy to use in buildings. (Photo: Ashley Ahearn)

AHEARN: So the warm wastewater in the sewage pipe provides the heat - just like the beer in the fridge - and then that heat is used to warm up clean water in separate pipes that circulate around the building. Systems like this have been installed in Japan, China, Canada and parts of Northern Europe - and they're having an impact. One of Mueller's systems went into a building in Vancouver and lowered that building's energy consumption by 75 percent.

MUELLER: We're operating at 600 percent efficiency so every dollar we spend to recover the heat out of the sewer we get six dollars worth of heat out.

AHEARN: Mueller's company sales are projected to jump from three million this year to 50 million next year. But wastewater energy systems won't work on all buildings.
It can be tricky to retrofit buildings that don't already have hot water heat circulating systems.

Jessie Israel with King County says the key is to get developers of new buildings thinking about incorporating this technology early on in the design process - in order to reap big energy savings later.

ISRAEL: 350 billion KWH of energy are lost every year, just flushed down the drain. If we're smart about how we build cities and how we build communities and how we build buildings. Maybe 50 years from now that will be a much smaller number.

AHEARN: I'm Ashley Ahearn in Seattle.

CURWOOD: Our story on turning wastewater to energy comes to us from the public media collaborative EarthFix.



Ashley’s story on the Earthfix website

King County’s energy ideas page


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