Canada finds new uses for sewage water’s thermal energy
Capturing heat from waste could result in matching ever-growing energy demand
In False Creek, a waterfront community in Vancouver, Canada, the energy being used to heat homes comes from an unlikely source.
Instead of a boiler, each building’s hot water arrives in underground pipes from a city-owned plant-a system called district heating. A growing number of municipalities are incorporating this strategy into their plans to cut fossil fuel consumption, using renewable energy sources such as geothermal or solar instead of oil or natural gas.
But in the case of False Creek, they’re using sewage. It turns out that the water flowing out of your kitchen sink, washing machine, shower, dishwasher — and yes, toilet — is warmer than when it first shows up at your house.
Wastewater flowing through municipal sewer pipes can maintain a temperature of between 50 degrees and 68 degrees Farenheit, even in the coldest months.
So rather than waste that heat,
False Creek uses it. In 2022, the local utility said it generated 23,441 megawatt hours of thermal energy from sewage waterenough to heat 3,000 residential apartments for a year.
“What we’re doing is converting wastewater into a resource,” says Derek Pope, manager of neighborhood energy for Vancouver. “In doing so, we’re able to heat up an entire neighborhood.”
With the energy transition falling behind as global warming continues to accelerate, cities are scrambling to find ways to help bridge the gap. Wastewater is one of a number of alternative energy options being exploited.
Across the globe, 380 billion cubic meters of municipal sewage is generated annually, according to a 2022 report by the European Investment Bank. As cities grow, that’s expected to increase 51% by 2050.
According to the US Department of Energy, a year’s worth of American wastewater contains an estimated 350 terawatt-hours of energy, which could heat 30 million homes. In other words, that’s a lot of unused heat.
The energy used to heat homes and workplaces is among the highest contributors to individual carbon footprints. Gas boilers and wood stoves release vast amounts of carbon dioxide, while electric heaters are only as green as their power source-often gas or coal. Globally, heating accounts for 40% of all energy-related emissions.
It may then come as no surprise that, according to a 2023 report by global engineering firm Danfoss, excess heat is the world’s largest untapped energy source.
Around 2,860 terawatt-hours of waste heat is generated annually in the European Union alone, almost the same as the area’s total energy demand for heat and hot water in residential and service sector buildings.
A global push to capture this heat could help avoid burning almost 30 million barrels of oil per day, or 650 billion cubic meters of natural gas per year, the report says. “This is not only about reducing greenhouse gas emissions; it’s also about rethinking how we view waste heat resources like sewage,” says Pope.
“Around any given city, there are various waste heat resources that systems like ours could make use of, and we need to begin thinking about them seriously.”
Aaron Gillich, a professor of building decarbonization at London South Bank University, says initiatives like False Creek’s make it easier to implement stricter building limits on greenhouse gases as well as more sustainable urban planning.
In Vancouver, a big part of that is reducing dependence on natural gas. “We use so much that no single thing can replace it on its own,” Gillich says. Wastewater “is potentially a really significant ingredient in squaring that circle.”
Wastewater is an appealing source of energy because its supply is stable-as is its temperature.
That means the pumps that transfer its heat to clean water can operate in winter, when demand for heating is highest.
In Vancouver, a city of 680,000 on Canada’s west coast, buildings account for 57% of greenhouse gas emissions.