US city turns wastewater into heat and cooling for schools, offices

A redevelopment project in Denver’s National Western Center has transformed nearby sewer infrastructure into a sustainable energy source by capturing heat from wastewater to provide heating and cooling for classrooms, an equestrian center, and a veterinary hospital. The system leverages the consistent year-round temperature of sewage—around 70°F—to efficiently transfer heat via a sealed heat exchanger without mixing wastewater with clean water. This approach reduces reliance on traditional boilers and chillers, cutting energy use and emissions, with auxiliary cooling towers and boilers only used during extreme weather. Denver’s advantage came from its proximity to major sewer lines in a low-lying industrial area, simplifying installation and boosting efficiency. The project exemplifies how existing urban sewer infrastructure can be repurposed to lower costs and environmental impact, a concept applicable to many cities worldwide. Experts note that wastewater heat recovery is an underutilized resource with significant potential, especially for buildings with centralized hot-water systems such as apartments, laundromats, and factories. Similar systems are already operating in parts of