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Warm and hot wastewater on the way out can be used to heat clean water on the way in.
Original image CC-BY-2.0 by Tiago Avancini via Flickr.

Efficiency, Waste, Water

Wastewater Heat Recovery On the Rise

The US flushes about 350 billion kilowatt-hours of heat energy down the drain every year. Enter wastewater heat recovery.
BY Stu Campana on

More in Efficiency:

Waste-to-energy is an idea about to hit the big-time.

What used to be a suite of technologies mostly employed by the poor in developing countries is now being eagerly revamped for distribution across North America by waste-to-energy start-ups hoping to capitalize on the fantastic quantities of waste we produce.

We produce food waste that can be used to create compost for agriculture.

We produce solid waste that can be used to create biogas to meet our energy needs.

Waste-to-energy is an idea about to hit the big-time.

What used to be a suite of technologies mostly employed by the poor in developing countries is now being eagerly revamped for distribution across North America by waste-to-energy start-ups hoping to capitalize on the fantastic quantities of waste we produce.

We produce food waste that can be used to create compost for agriculture.

We produce solid waste that can be used to create biogas to meet our energy needs.

We even produce wastewater, with a heating potential that – until recently – no one had really contemplated harnessing.

There are two reasons why not:

  1. It’s hard to filter the raw sewage well enough that it won’t plug the heating pipes.
  2. Raw sewage is gross.

Lynn Mueller, President of Vancouver-based International Wastewater Systems, has found a solution to the first problem. As for the second, he thinks the return on investment is going to be enough to prevent clients from holding their nose.

With approximately 350 billion kilowatt-hours of heat energy flushed down drains in the United States alone each year, he’s probably right.

Wastewater heat recovery works just like a geothermal heat pump. The heat from water washed down sinks and toilets is captured by a heat pump, which applies the heat to the clean water entering the building.

Wastewater isn’t particularly warm – only about 15.6 degrees – but it’s still much warmer than the cold, clean water that must be heated somehow. The waste heat is able to do a bunch of the heavy lifting. And since there are basically endless quantities of it, serving no other purpose, very high heating efficiencies are possible.

It’s the efficiency that makes waste-to-energy such an appealing financial prospect. By definition, waste is just a burden on the system. So anything useful that comes out of it is a bonus. Mueller claims that his system operates “at 500 per cent efficiency,” which is quite good by any standard.

“Waste recovery seems like such a novel idea,” says Mueller, “but [the waste] is available everywhere.”

Solid waste energy recovery is also making waves across Canada and the USA. More than 80 municipal waste-to-energy facilities are in operation across North America, with more coming online all the time. A typical facility can power over 30,000 homes, which is an appealing economic benefit to go along with the ninety per cent reduction in waste processing. Edmonton’s plant is currently producing 38 million litres of methanol annually.

Like any idea on the rise, waste-to-energy is creating winners and losers. In danger of slipping into the latter category is Plasco Energy, who, at the time of this writing, were expected to miss the final deadline to secure financing for a full-scale waste-to-energy plant in Ottawa.

Although small-scale waste conversion systems do exist, most of our established technologies work best with economies of scale. Thus, municipalities have found themselves taking the lead on implementing waste-to-energy systems.

In Vancouver, Mueller has been working closely with the municipal government to install his wastewater heating systems in everything from apartment buildings to hospitals and prisons. Although cities are typically a little territorial about their infrastructure, the appeal of heat and energy from nothing may be softening that stance around the country: “Their motivation is to make a greener city. Vancouver is now at the forefront of recycled heat.”

With luck, others will soon follow suit.

Stu Campana is an international environmental consultant, with expertise in water, energy and waste management. He is the Water Team Leader with Ecology Ottawa, has a master’s in Environment and Resource Management and writes the A\J Renewable Energy blog. Follow him on Twitter: @StuCampana.