HWN Suggests

The neglected clean heat we flush down the drains

Heat in water is relatively easy to harness once it's in the sewage system because it's contained – and no, any heat recovered isn't going to smell. By comparison, heat in the air quickly escapes out of windows, doors, and roofs. In addition, there's plenty of hot wastewater to work with. In 2020, experts at the London South Bank University estimated that energy from the UK's daily 16 billion litres of sewage wastewater could, in theory, provide more than 20TWh of heat energy annually – enough to provide space heating and hot water to 1.6 million homes. Over in the US, Americans flush an estimated 350TWh of energy down the drain each year – the equivalent of heating 30 million homes a year.

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 Waste Wattage: Cities Aim to Flush Heat Energy Out of Sewers

So much hot water goes down the drain that cities worldwide are recognizing sewer heat as an untapped resource that can help cut energy costs.

Articles of Interest

Heat Recovery from Wastewater—A Review of Available Resource

The EU Directive 2018/2001 recognized wastewater as a renewable heat source. Wastewater from domestic, industrial and commercial developments maintains considerable amounts of thermal energy after discharging into the sewer system. It is possible to recover this heat by using technologies like heat exchangers and heat pumps; and to reuse it to satisfy heating demands.

How Your Hot Showers And Toilet Flushes Can Help the Climate

A secret cache of clean energy is lurking in sewers, and there are growing efforts to put it to work in the battle against climate change. The U.S. Department of Energy estimates Americans wash enough energy down the drain every year to power about 30 million homes. The sources are often everyday items inside homes. Think hot showers, washing machines and sinks. Evolving technology is making it easier to harness that mostly warm water.

In Vancouver, Wastewater and Sewage Provide Energy

Relative to conventional combined electricity and natural gas systems, the sewage heat recovery process has reduced greenhouse gas emissions by 65 percent, an immense source of pride for a city attempting to become a world leader in green energy.

Renewable energy of wastewater heat recovery

Basically, the heat from wastewater is CO2-free and represents a significant opportunity for the energy transition in the heating market.

These apartments will soon get their heat from wastewater

At two high-rise apartment buildings in the Bronx, when a tenant takes a shower or does laundry, the hot water that goes down the drain will soon help heat their apartment in the winter—or cool it in the summer.

Wastewater heat recovery is now officially a renewable energy source

The European Commission instituted wastewater heat recovery as a renewable energy source in its recast of the directive on the promotion of the use of energy from renewable sources, also known as RED II. This recognition comes as wastewater heat recovery is becoming an increasingly popular energy source for houses, apartment buildings, hotels and swimming pools.

Wastewater heat recovery: From dirty water to clean energy

Around the world, and more recently in Canada and the U.S., cities are realizing that the water leaving our homes and offices—specifically, warm and hot wastewater—is an astoundingly powerful source of energy. One estimate is that Americans flush 85 trillion litres of wastewater or 350 billion kilowatt-hours of energy into the sewers each year—roughly enough to power 30 million U.S. homes. In Canada, where commercial and residential buildings make up 17 per cent of the annual carbon emissions, capturing the thermal energy from wastewater could remove up to 54.7 million metric tonnes of greenhouse gases annually, the equivalent to taking 18.6 million cars off the street.

‘A treasure beneath our feet’: How the Dutch went down the toilet looking for heat

Sewage waste is now being seen as a reliable heat source for millions of homes in the Netherlands.

‘Sewer Heat’ Could Be Hidden Ally Against Climate Change. Here’s How Denver Is Pulling It To The Surface

There’s no mystery over how excess energy ends up below cities. Showers, hot waters and sinks all add hot water to sewers. In fact, the U.S. Department of Energy estimates American’s wash 350 billion kilowatt-hours of energy down the drain every year. For some perspective, that’s enough power for about 30 million U.S. homes. The largest sewer heat-recovery project in North America is now under construction in Denver.