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How DC Water Turns Poop Into Power

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DC Water's Chris Peot standing in front of the world's largest power generating thermal hydrolysis digester in Blue Plains.
Jennifer Strong/WAMU
DC Water's Chris Peot standing in front of the world's largest power generating thermal hydrolysis digester in Blue Plains.

There’s a new kind of power in the nation’s capital: Every time a toilet flushes in the District, or a garbage disposal runs, it’s helping power DC Water’s Blue Plains Treatment Plant. The utility's new digester facility is creating renewable energy from solid waste and microbes.

Wastewater treatment facilities are notorious consumers of electricity. Indeed, DC Water is the city's largest consumer of power. "They use more electricity than any other need in your city. The wastewater facility in DC uses 26 megawatts," says Patrick Serfass, the Executive Director of the American Biogas Council.

Put more simply, it takes roughly as much electricity to run DC Water as it does to power 26,000 homes.

The good news? Serfass says at least part of the solution is right in front of us. "We have a great resource in this organic material we flush down the toilet," he says.

DC Water operates one of the nation’s largest sewers. It services not only the District, but also portions of Loudoun and Fairfax Counties in Virginia, as well as Montgomery and Prince George's Counties in Maryland.

Chris Peot handling DC Water's compost product made from human waste which they intend to sell at local garden centers. (Jennifer Strong/WAMU)

DC Water treats 370 million gallons of sewage every day — enough to fill RFK Stadium.

Lauren Fillmore at the Water Environment Research Foundation in Alexandria says the utility "has a lot of opportunities as well as a lot of issues it has to deal with in managing all that water that comes 24-7."

Among those issues, the wastewater it treats has to be clean enough to be released into the Chesapeake Bay Watershed. Also, something has to be done with all the solid waste.

DC Water's Christ Peot says he puts it on his garden. "I grow herbs and tomatoes and things for my family, and I love my family. I feed them to my family. It's an asset we should really make use of," he says.

Peot is the man behind a variety of innovations at DC Water, including compost and fertilizer programs, and the world’s largest thermal hydrolysis digester facility. That’s what’s producing all that renewable power from sewage.

His analogy for how the system works starts with eating dried beans. "Our stomach acids and the microbes in our stomachs would figure out a way to extract some of the energy out of it, but most of the energy would pass through with our solids," he chuckles. "But if we put it into a pressure cooker, got it all soft and mashed it up with a fork, we'd be able to extract a lot more of the energy out. That's what this process does. It prepares the food for the microbes in the digesters," says Peot.

Patrick Serfass says it also kills any harmful pathogens in that final product that Peot puts on his garden. "It both makes the solids that you take out of it that you can use on your garden, it makes them safer," he says, "It also produces more renewable energy in the process, so it's a good system."

The solids that come out of the digester after the energy making process are blended with sawdust and bark to create a product that looks, and smells, like topsoil. Chris Peot says with a smile, "It doesn't smell like what you might think it smells like. We think it's going to be a very marketable product. We are currently giving it away in the form of compost to our sister agencies and to non-profits in D.C., but we intend to establish a market for this for sale to garden centers and landscapers."

Lauren Fillmore at the Water Environment Research Foundation says this kind of thinking is the future of water treatment.

"A lot of what people used to consider waste in the past, really aren't waste. They're carbon, nitrogen, and phosphorus. There are elements and components that have value, the problem is, they aren't in the right location. They shouldn't be in a water body. They should be taken out and re-purposed," she says.

Peot says these projects will mean fewer rate hikes. It’s cheaper to produce power with the new digester than it is to purchase it from the grid. Not having to truck the solids out of DC also saves money, and if the compost product takes off, that could even generate income.

Music: "Green Tambourine" by Oliver Nelson & Steve Allen from Happenings/Soulful Brass

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