Did you know that, according to the U.S. Department of Energy, 350 billion Kw-Hrs worth of hot water is discarded annually through drains in North America, and that the value of energy put into wastewater is a minimum of $10 billion annually?
The typical sources for this huge amount of waste down the drain are doing our laundry, running our dishwasher, or taking a shower or bath. Stuff we do every single day of the year.
But this is now an abundant, accessible renewal sewage—so eventually it’s not all going to waste.
As we continue to search for new and sustainable energy sources, we have found that we are discarding billions of Btus / Joules /Kw-Hrs into water, leading to the 350 billion Kw-Hrs worth of hot water discarded annually through drains in North America.
Most of this is recoverable. By using municipal wastewater as a heat source in winter, and as a heat sink in summer, you can generate considerable savings in heating, ventilation, and air conditioning (HVAC) costs. Wastewater heat recovery systems use a heat exchanger to transfer heat from the municipal wastewater to a conveyance medium, which you then pump to individual buildings.
The heat pumps located at these buildings extract heat from the conveyance medium to deliver energy for space heating and cooling.
Drivers for Sewage Heat Recovery
The drivers for sewage heat recovery are the rising price of energy, the immediate urgency to switch from fossil fuels, provincial and municipal climate change and energy goals, and increased requests for access to sewage.
What makes the drive for sewage heat recovery viable are these three facts about wastewater:
- Wastewater has an “average” temperature of approximately 21°C (70°F) when exiting buildings.
- On “average,” North America per diem/capita domestic water usage ~ 100 gallons. Range 70 – 130.
- Wastewater can represent between 15% and 25% of a building’s total daily energy requirements.
Sewage Heat Recovery in the Public Sector
The first large-scale wastewater heat recovery system, the False Creek Energy Centre, was built in Vancouver. It was a $45M publicly funded project and was completed in 2010. This first-of-a-kind heating system mines energy from Vancouver’s sewage system and heats a downtown neighborhood with the heat. It is a low carbon, reasonably priced heat that has a small footprint.
This sewage heat recovery system is the first in North America, with the other systems in Oslo, Norway, and Tokyo, Japan. Vancouver’s False Creek Energy Centre plans to go from heating 250,000 square meters to 650,000 square meters as more buildings in the neighborhood become connected.
The False Creek Energy Centre’s wastewater heat recovery system has two steps. First, the sewage is run through a filter to clean it out, then it is pumped through the heat exchange system, a piece of machinery the size and shape of a semi-trailer truck, where the heat pump strips out the heat. After upgrading the heat, the heat is then transferred to pipes that carry the hot water into the homes and buildings of nearby customers.
The City of Vancouver installed the sewage recovery system for the greenhouse gas savings—its goal is to be carbon neutral after 2020.
Sewage Heat Recovery in the Private Sector
Adera Capital Corporation developed seven35, the first multi-family LEED for Homes Platinum Development in Canada. The seven35 project is comprised of 60 one- and two-bedroom town homes with an average of 1,000 square feet per suite. One of the project’s sustainable features is International Wastewater Systems’ (IWS) SHARC Sewage Heat Recovery System.
The average water usage per suite is 250 gallons per day at an average exiting temperature of 20°C (68°F). The SHARC system has 2-5 ton FHP heat pumps with double walled, vented heat exchangers that recover waste heat from the exiting raw sewage and moves the heat into 6 to 120 gallon DHW storage tanks. The DHW storage tanks are heated to 52°C (126°F) by the heat pumps.
Adera’s seven35 is the first wastewater heat-recovery project among private multi-unit developments in North America.
Benefits of Sewage Heat Recovery Systems
Sewage heat recovery systems are cost competitive, they reduce the environmental footprint, and provide a sustainable alternative to traditional methods of heating and cooling such as the use of fossil fuels. As well, sewage treatment plants designed for resource recovery are less expensive to build and operate, further cutting costs and reducing our environmental footprint.
We’re now heading in the right direction, taking the road, although not well travelled, toward sustainable wastewater treatment and resource recovery.
Walking down that road will never be the same again. Today, when you leave a building, drive down the road, or walk or cycle to work, you’ll know that beneath the sidewalks and roadways flows energy. Abundant. Accessible. Renewable sewage. And we created it. Every last little drop.