The question of what do we do with the detritus from the demolition of buildings is a big one, especially as the prospect of aging infrastructure in Calgary necessitates their renovations or replacement.

The environmental impact of building new homes was among the concerns raised by Calgarians during the city’s largest-ever public hearings on citywide up-zoning in late April and early May.

But for one Calgary business, Calgary Aggregate Recycling (CAR) the answer to some of those construction questions is already being put into practice—with over 125,000 tonnes of soil and hydrovac slurry processed through their first-of-its-kind facility in Canada, instead of going to landfills.

With that, tonnes of GHG emissions were also removed from the environment. Some 6,696 metric tonnes were reported to Emissions Reductions Alberta by CAR in 2023.

For CAR President Travis Powell, the ability to reduce, reuse, and recycle should be a source of pride for Calgary’s construction industry.

“I think it has to be on everybody’s radar, and all of our competitors will be thinking probably how they’re going to lower their impact, but we’re pretty proud of that,” he said.

In 2023 the City of Calgary disposed of 752,000 tonnes of waste, of which just 124,000 was made up of garbage in household black bins.

About 20 per cent of waste entering Calgary landfills comes from the construction and demolition industry.

Although the City of Calgary noted in a 2021 Transportation Department report, related to the transportation of waste goods, the commercial demand for construction materials meant that diversion and recycling were more cost-effective for construction businesses.

That was reflective in the lower cost of business for companies wanting to recycle instead of tipping at landfills, Powell said.

Tipping fees for materials dropped off at CAR were about $40 per tonne on average based on material composition he said, versus $150 at the City of Calgary’s Spyhill Landfill.

The other advantage he said was that it also made it easier for companies looking to recycle materials to drive from a Calgary construction site to a Calgary recycler, instead of driving to the next closest recycler in Brooks—and for KLS Earthworks, which owns CAR, that is a difference of going from 40 trucks on their own job sites to eight.

“At the end of the day, I think that it makes some of these projects more viable for sure. From an affordability standpoint, and accessibility standpoint, I think that we’ve done a good job on that,” said Powell.

Better use for material than dumping

Ultimately the goal is to find a better use for construction detritus than dumping it at a landfill, Powell said.

“Landfills are essential, absolutely, I’d say that they’re more essential for our municipal waste that we’re generating on a daily basis, rather than filling them up with soil that’s highly recyclable,” he said.

“One of our counterparts in New York, their tagline is that they want people to look at recycling soil as easy as recycling bottles and cans. It truly is that easy to reclaim a lot of this material and put it back into construction products.”

That goal, he said, aligned with the City of Calgary strategy to divert construction and demolition material.

The City has said previously that it wants to increase the amount of construction industry waste diversion to reach at least 40 per cent by 2025.

“We’re pretty fortunate in Calgary just for our soil types. There is a lot of this eluvial type soil deposited from glaciers off the mountains, so we have really good soil type that makes it really recyclable,” said Powell.

“Probably 85 to 90 per cent of that material could stay out of landfill.”

He said that recycling could even apply to contaminated soils, like those found throughout Downtown and West Village locations.

On the compliance side, the firm reports all of its emissions data to Emissions Reduction Alberta, which works on behalf of the Government of Alberta to find projects to reduce GHG emissions.

That compliance and tracking, said Powell, has been useful for larger contractors like Enmax and ATCO which also want to ensure they’re reducing emissions through their own diversion efforts.

The impact of that emissions effort for CAR and KLS is also immense, he said.

“If we get over this 220,000 times a year threshold, that will actually offset enough emissions that both Calgary Aggregate and our contracting business KLS will be carbon neutral. It’d be a pretty good feather in our cap. We’re a big diesel fuel consumer, and we have a lot of heavy equipment, but we’re on the right path.”

How recycling works at CAR

At the CAR facility, material made of concrete goes through a concrete crusher where the concrete is separated from rebar. Any other materials like plastics or garbage are also separated out, and then both the concrete gravel and metals can be sold and reused by industry.

In fact, the concrete that made up the old Stampede Corral was among the debris turned into base gravel that makes up some of Calgary’s newest warehouses.

Throughout the history of CAR, rebar collected from crushed concrete has gone on to provide material for several projects including pipelines for Alberta’s oil and gas industry and municipal infrastructure, Powell said.

That process has been in operation for decades and has diverted on average about 250,000 tonnes of concrete and about 125,000 tonnes of asphalt each year.

The soil recycling was the newest addition to CAR in the second half of 2022, after an initial proposal to be built in 2021.

That soil, as part of the recycling process, becomes five different saleable products that ranges from five millimetre concrete sand up to larger rocks used for drainage—and then various sizes for end uses like roadworks and construction in between.

Even the finer grain waste product that’s 63 microns in size isn’t really wasted.

“Our ultra-fine material which isn’t a saleable product, but it’s a recycled product as well through our process, it goes to the LaFarge Exshaw. We did the testing on it found that it’s high in silica and alumina, which works well for the chemistry for the making of cement. So LaFarge actually takes our waste stream and actually they upcycle it into cement powder,” Powell said.

That’s a largely automated process that uses recycled water to separate out the different sizes of stones and sand.

Before the introduction of a hydrovac slurry diversion process, the water-based recycling process was 95 per cent efficent for re-use, with the remaining 5 per cent being lost largely due to evaporation.

“We went from being a net water consumer in the first four months—we had to buy top of water from the City of Calgary—then we decided that we needed to figure out a way to get hydrovac slurry introduced into this so we could reclaim that water and use that for our top up requirements,” Powell said.

“So we went from being a net consumer to actually being a net exporter of water, which is pretty neat. So that’s really 100 per cent recycled material.”