As frigid temperatures sweep across parts of the U.S., indoor heating systems will be working extra hard. Heating buildings is a big part of energy consumption in U.S. cities, but a technology that's relatively new to the United States is helping make that energy consumption more sustainable.
Many of us have heard of wind and solar energy, but wastewater can also be a significant source of renewable energy. Leslie Fangman works for CenTrio, the largest operator of district energy in the U.S. She is part of a project that is taking wastewater from the Denver Metro area to thermally heat and cool commercial buildings.
"Thermally heating and cooling buildings is about 50% of energy consumption in any city, and so doing it more energy efficient and more sustainable is very important to the environment," Fangman said. "Most sanitary sewer lines run very hot, like upwards of over 70 degrees Fahrenheit even in the wintertime. A lot of that is driven because your dishwashers, your washing machines, your hot showers. All of that water that's heated goes down into the sanitary sewer pipes."
The heart of the operation is the SHARC wastewater energy transfer system. Fangman calls it a heavy-duty garbage disposal.
"The sewage water comes up into the macerator, the heavy solids fall down to the bottom, and then, the sludge comes up through these pipes," Fangman said. "And the heat exchanger transfers the heat of the sewage to the clean water."
The sewage water and the water being transported to buildings never touch. Fangman says it's a closed loop.
"This system, when it's fully built out, will save the equivalent of 6.6 passenger miles of CO2 out of the air annually," Fangman said.
She says the water that's conserved is equivalent to five Olympic swimming pools.
"So, we get the benefit of basically utilizing energy from the sewer that would have just been wasted or not used at all," Fangman said. "And then keep not only greenhouse gases but also water conservation for the system."
While this technology is quite new to the U.S., Fangman says it's been used in Western Europe for more than a decade and in Canada for at least five years. The facility in Denver will serve as a model for systems that can be created in metro areas all over the country.
"We're excited to be the first one, but not the last," Fangman said.