Denver Heats Buildings With Sewage to Fight Climate Change

Denver is tapping into an unlikely clean energy source: the city's sewage system.

The Colorado capital is launching a pilot program for a "thermal energy network" that will heat and cool buildings using warmth extracted from wastewater. Buildings in the network will connect to a loop of circulating water that draws heat from sewage flowing beneath the city's streets.

The technology works because sewage is naturally warm. Instead of letting that heat escape into the ground, the system captures it and redistributes it to buildings that need heating in winter and cooling in summer.

Denver aims to eliminate all greenhouse gas emissions by 2040, an ambitious goal that requires creative solutions. Traditional heating and cooling systems account for a huge portion of urban energy use and carbon emissions.

The thermal network approach kills two birds with one stone. It reduces reliance on fossil fuels while using an energy source that otherwise goes to waste every single day.

The Ripple Effect

Cities around the world are watching Denver's experiment closely. If the pilot succeeds, it could offer a blueprint for urban areas struggling to meet climate goals without massive infrastructure overhauls.

The technology isn't entirely new. European cities like Oslo and Amsterdam already use sewage heat recovery systems, proving the concept works at scale.

What makes Denver's approach noteworthy is the timing and potential impact. American cities desperately need proven, scalable climate solutions, and sewage heat recovery requires relatively modest upfront investment compared to completely rebuilding energy grids.

The system also sidesteps a common climate action problem: it doesn't require people to change their behavior. Buildings connected to the network get heated and cooled just like always, but with dramatically lower emissions.

If the pilot works as planned, Denver could expand the network across the city. Other American cities facing similar climate deadlines would likely follow suit, turning a waste product into a powerful tool against climate change.

Sometimes the best solutions are literally right under our feet.