When Équipe Laurence decided to build new office space for its growing roster of employees, it turned to an unlikely place to power its operations: aerated wastewater ponds.

The civil engineering firm had heard about the technology, in which brown water from municipal sewage can be deployed as a heat-pump system to generate heating and cooling. But it hadn’t yet been tried in open-water ponds.

“Alexandre Latour, our president, he realized that we’re building right next to the aerated ponds, the wastewater treatment plant for the City of Ste-Adèle, and he wondered if we could tap into this energy source rather than do geothermal energy,” Vincent Bouré, engineer and partner with Équipe Laurence in Ste-Adèle, Que., said.

As they were also aiming to achieve LEED certification with the $6.4-million facility, this technology seemed to offer just such a benefit.

After various “brainstorm” sessions within the firm, it was decided to tap into the resource.

“There are other systems that tap into sewers as an energy source but none of them were one-to-one. Eventually we came out with this design where we have about 200 metres of piping between our office and the pond, and then in the pond we have 12 coils made up of one-inch piping to maximize the heat-exchange surface,” Bouré said in an interview with Sustainable Biz Canada.

The pipes contain glycol which provides both heat in winter and cooling in summer for the new headquarters. It’s a standalone system that isn’t hooked into the power grid and is designed to power only the one building.

Huge savings on heating, cooling costs

The biggest benefit to the company is clear, Bouré said.

“We estimate that we save about 75 per cent of our heating and cooling bill with that technology so it has a pretty quick payback period in a few years.”

The system provides 32 per cent more energy efficiency and by using rainwater to flush toilets, it uses 60 per cent less water.

But because the technology was unproved, the company had to construct a backup electrically powered furnace just in case the system failed.

“In the end, it worked really well. We haven’t used the electrical system at all in the first two-and-a-half years of the building’s life.”

With this successful project completed in 2022, Équipe Laurence recently announced a new project that will also use brown water to cool and heat a sports facility near its office.

Working with real estate developer Groupe Wilnor and the town of Prévost — about 75 kilometres north of Montreal in Quebec's Laurentians — a new multi-use sports complex will began construction in mid- to late-2025 and should be completed in two years.

The facility will serve the town of 14,000 and will include 15 pickleball courts on its roof as well as a fitness centre, volleyball and basketball courts, and spaces for athletics and swimming.

It will also include restaurants, shops and professional suites in three buildings. It is estimated to cost $30 million and it represents 16,000 square feet of floor space, but that figure is subject to change.

When the site was in its planning stages, the builders were told designing a green energy building was paramount.

“We had one connected just five kilometres away, and it works very well, so the city pretty much imposed it on the builder. They’ve taken a really proactive approach in terms of sustainable development over a number of issues," he said.

"When they submitted for the construction permit, the city heavily suggested that they should look into this system for their heating and cooling and the fact that their neighbour two towns over did it, it took out one of the big hurdles, which was the risk-taking.”

Scaling up the technology

The sports complex will be around 10 times bigger than the Équipe Laurence office, Bouré said, but the initial project experience provided some valuable lessons.

“The big thing we learned, it works really well. The challenge will be to scale it up but we’re pretty sure that it does,” he said.

The technology has been dubbed “cloacothermal” which is derived from Latin for sewer, or cloaca, Bouré explained. It’s similar to geothermal or hydrothermal energy.

“But wastewater is a much better source of energy. This has all that biological matter that heats it up, so the energy budget that’s in it is much higher than regular water, so that is a rather simple heat pump in the building that is connected to a system of coils and pipes that run in the pond.”

While it worked out for Équipe Laurence, the build was not without some challenges.

“One of the most challenging things was getting the coils to float at the right height. We did not want them at the bottom where all the matter is collected. We did not want it at the top either because the temperature fluctuates a bit too much, so we needed to be about a couple of feet under the surface and so that was a bit of trial and error trying to build with certain materials to get it to adjust,” Bouré said.

Potential for cloacothermal expansion

The cloacothermal technology has potential to be used on a larger scale: there are about 750 aerated ponds in Quebec and many more across North America, according to Bouré.

“We’ve had a few talks with other cities but the thing is that it does require a wastewater plant, and not everybody wants to build right next to a wastewater plant, which is understandable, even though we don’t have any odours from the ponds. It’s very well-suited for municipal infrastructure: usually the cities own the land by their plants, so they can build a supporting facility with huge volumes.”

For now, this is the only project at the building stage, but the technology is being noticed.

“It’s getting some traction in the green-energy or green-building world and I hope it inspires people to think differently about things like these unwanted resources that we can tap into to lessen the impact of our developments,” Bouré said.