Whenever residents of Edmonton, Alberta flush their toilets after 2012, some of their sewage will find its way to a Petro-Canada plant northeast of the city that converts bitumen-like oil sands into crude oil.

Petro-Canada has promised that the first phase of the Fort Hills Sturgeon upgrader, consuming 15.8m litres of water a day, will not only run entirely on treated wastewater, but will then send the used water back to Edmonton for further recycling.