Treated Denver wastewater flows into the South Platte River in April. In what may be the largest U.S. project of its kind, Denver will use excess energy from sewage wastewater to heat and cool a new agriculture, arts and education center.
A secret cache of clean energy is lurking in sewers, and there are growing efforts to put it to work in the battle against climate change.
The U.S. Department of Energy estimates Americans wash enough energy down the drain every year to power about 30 million homes. The sources are often everyday items inside homes. Think hot showers, washing machines and sinks. Evolving technology is making it easier to harness that mostly warm water.