CBC News: Toronto Wants Buildings to Tap Into Its Sewage for Heating

Many buildings buy and burn gas or other fossil fuels to keep warm. But there's actually a free, carbon-free source of heat underfoot that they could be tapping into instead — sewage pipes. 

Along with wastewater, those pipes carry a lot of "waste" heat from buildings, including warm water from showers and dishwashers. […] In most places, that heat is literally going down the drain. But it doesn't have to be that way.