It may seem incredible that an entire hospital can be powered by energy captured from city sewers. But it is happening in Toronto, Ontario, where the world’s largest wastewater energy-transfer project is almost complete and the city is on the path to becoming one of the world’s leaders in water/wastewater energy projects.
Noventa Energy, which is carrying out the project at the 118-year-old Toronto Western Hospital, says the carbon-free thermal energy will supply up to 90% of Western’s heating and cooling needs, while reducing its direct greenhouse gas emissions by about 8,400 metric tonnes each year. That’s equivalent to removing 1,811 cars from the road.
Noventa proposed the joint venture with Western in 2019, after the City of Toronto asked for private-sector proposals to tap its wastewater energy. It is the leading edge of a powerful trend known as Wastewater Energy Transfer (WET) that is helping Toronto move towards becoming a sustainable city where buildings will produce no on-site GHG emissions, where dependence on fossil fuels will be reduced if not eliminated and where the economic, environmental and social benefits will be shared by all.
In July, 2022, Toronto City Council approved Noventa’s request to build nine more WET™ projects in Toronto. This positions the city of Toronto as one of the world’s leaders in water/wastewater energy projects to decarbonize large community and institutional buildings and accelerate the City’s TransformTO climate goals.
Under its TransformTO Net Zero Strategy, the City of Toronto estimates its sewers can produce 17 megawatts of energy and potentially support well over 20 WET projects which would reduce approximately 200,000 tonnes of GHG emissions annually while producing value for the City through the sale of thermal energy.
The sewage waste heat recovery system captures the heat from sewage and uses it to warm or cool the air inside, using a cutting-edge heat exchanger from Huber, a German firm. It takes the thermal energy out of the sewage, concentrates it, and then uses it to replace the natural gas Toronto Western burns to run its boilers and chillers.
The sewage travels in a closed loop from the main, through the heat exchanger, and then back into the sewer. The process reverses in summer, removing heat from the hospital and transferring it into the sewage.
A growing number of cities also see recovering energy from wastewater as an opportunity, says Corporate Knights. The City of Vancouver’s sewage heat recovery plant in False Creek can generate 3.2 megawatts of power and distributes low-carbon energy for heating and hot water to 6.4 million square feet of mixed-use buildings. Halifax launched a small-scale sewage heat recovery project in 2021.
The possibilities of recovering energy from wastewater are immense. Over 168 billion litres of wastewater are dumped into North America’s sewers each year. Capturing just a fraction of its energy could generate 350 billion kilowatt hours – which could heat and cool the entire US for a month and a half.
Sources:
Decarbonizing our world is a global imperative. Noventa Energy website.
Tapping sewage for clean energy is the ultimate circular-economy play Corporate Knights, Oct. 30, 2023
Cities tap earth, sea and sewage for district energy Corporate Knights. May 30, 2022
Cover image and other images from the Noventa Energy website.