It is cheap, strong, fireproof, easy to transport and shape, but produces about seven percent of global greenhouse gas emissions
Brent Korobanik has a tough job.
A conservation scientist and St. Albert resident, Korobanik is the permitting and community liaison at Heidelberg Material's cement plant in Edmonton. He is part of a team that has been trying for years to figure out how to make carbon-free cement to combat climate change.
“It's in everything we build these days,” he said of cement, including roads, buildings and sidewalks, and it accounts for about seven percent of global greenhouse gas emissions — about 4.7 times what Canada produces each year.
“We can’t keep doing this.”
Cement is a difficult issue when it comes to climate change. Unlike heat, electricity and transport, we cannot make it carbon-free by simply using green energy. Instead, we need a whole range of solutions, including the ones Korobanik is working on.
Cement 101
Cement is a powder that hardens like glue when mixed with water, reports the European Cement Association. Concrete is made of cement, water, gravel and sand. Mortar consists of cement, water, lime and sand.
According to the federal government, concrete is the second most consumed product in the world after water. Canada alone is expected to produce 400 million tons of it between 2022 and 2027, which would fill enough concrete mixers to circumnavigate the globe 4.5 times.
“Cement is actually such a good material,” said Cyrille Dunant, a materials scientist at the University of Cambridge who studies cement: It is cheap, strong, fireproof, rustproof, and easy to transport and shape—properties that few other materials can match.
To make cement, you heat limestone (calcium carbonate) to about 850°C to convert it into lime and CO2, Korobanik said. Roast the lime along with other ingredients in a rotating horizontal oven at 2,000°C and you get a pumice-like substance called clinker. Grind and mix that with plaster of paris and you have cement.
The big hit
Net-zero cement is a two-part problem, explain Dunant and Korobanik. About 40 percent of CO2 comes from fossil fuels burned for heating. This heat could be generated with green electricity, but not so easily. The rest comes from the limestone. As long as we make cement from limestone – and we don't currently have a good substitute for it – we will be producing CO2 from it.
One solution could be to stuff these emissions underground. Korobanik and his team built a carbon capture pilot plant at the Heidelberg Edmonton Cement Plant to see if it was feasible. Korobanik is scheduled to speak about the pilot project at the 2025 Alberta Capital Airshed Clean Air Forum on Nov. 4.
“We want to apply CO2 capture directly to the chimney,” he said.
The pilot plant is a house-sized mess of pipes, tanks and sea canisters. Without the “Pilot Plant” sign it would be easy to miss.
The system takes the exhaust gases from the production building and directs them through a high chimney. Inside the chimney, liquids called amines rain down and absorb the CO2. The amines flow into a second stack, are heated to release their CO2, and are pumped back to the top of the first stack to absorb more.
While the pilot plant releases the captured CO2 into the air, the real plant will send it to a facility near Villeneuve for permanent underground storage, according to Korobanik.
The pilot plant captures 95 percent of the CO2 injected, or about three tons per day, and has cost about $100 million so far, Korobanik said. The real project will be the size of a large office building, catch about 4,100 tons per day, cost around $2 billion and allow Heidelberg to produce net-zero cement.
“It will be a huge facility,” he said.
The Cement Association of Canada predicts that such facilities could save about 28 percent of cement's CO2 emissions by 2050.
The biggest obstacles to carbon capture are politics and cost. Korobanik said the large-scale capture facility in Heidelberg was designed assuming the carbon price in Alberta would reach $170 per tonne in 2030, as planned. Alberta froze that price at $95 earlier this year, calling into question the economic viability of the facility.
“We need a clear, consistent greenhouse gas policy,” he said, and a stable, high price for carbon.
Carbon capture won't work everywhere because not every cement plant has the necessary storage, Korobanik said. It's also expensive, Dunant added, and most studies suggest it roughly triples the cost of cement.
Heidelberg opened the world's first CO2-capturing cement plant in Norway last June and is now producing CO2-reduced cement there. Korobanik said Heidelberg plans to make a decision on the Edmonton carbon capture plant next March.
Silver shot
According to the Cement Association of Canada, there is no silver bullet solution for net zero cement. Instead, the industry believes it can reach net zero by 2050 through a combination of policies and technologies, many of which are still in development.
“The losing crop right now is alternative fuels,” Korobanik said, particularly trash.
The Heidelberg plant in Edmonton began using various forms of waste for about half of its heating needs last year. Korobanik said. The waste (which includes tire fiber from a Sturgeon County recycler) arrives in (very smelly) truckloads and is tossed onto a conveyor belt to the kilns with a big red claw.
“For us, it’s a very high-energy fuel,” Korobanik said of that waste, and they don’t have to worry about the ash — it goes right into the cement.
Korobanik said these alternative fuels reduce the plant's greenhouse gas emissions by about 22 percent. Other companies hope that solar concentrators and eco-friendly electric ovens could lead to further savings.
We could also reduce cement's carbon emissions by using less of it.
One way to do this is recycling, but that is difficult. When you grind up used cement and add water, it becomes useless sludge, Dunant said. To truly recycle it, you have to reactivate it with around 1,450°C heat. You can't get that heat without burning a lot of coal or building an expensive electric oven that runs on green electricity, which is why hardly anyone recycles cement.
But steel recyclers already have environmentally friendly electric furnaces. They also mix lime fluxes with their molten metal to remove impurities – a job that can also be done with cement. Dunant's team showed that steel recyclers could get recycled metal and cement from the same furnace if they mixed used cement with their hot metal instead of flux.
“You get twice the value from the heat and twice the value from the [cement]Dunant said, with little to no additional CO2 released.
Dunant said this form of recycling could optimistically eliminate 80 percent of cement's carbon footprint if used everywhere – which he said is feasible since steel recyclers could make a bundle out of it. However, there are limits: not every cement plant is located near a steel recycler, and not every recycler has access to green electricity.
Clinker substitutes like fly ash (used at the Edmonton plant) also allow us to use less cement, reports the Cement Association of Canada. However, these substitutes are typically location-specific and supply-limited, limiting their potential. Efficient designs and waste reduction could also reduce our cement needs and reduce the industry's carbon footprint by 14 percent by 2050.
Cement itself could save a further five percent by 2050, predicts the cement association. Korobanik explained that cement naturally absorbs CO2 and turns back into limestone. If we could harness this through building design and other processes, we could turn our cement structures into CO2 sponges.
Net zero cement is hard, but the rewards are great. Not only is there huge demand for carbon-free cement, but the technologies being developed to produce it (such as waste-to-energy conversion and carbon capture) could also help other sectors address climate change, Korobanik said.
“We have a lot of things we can offer the community,” he said.
Net zero cement is the goal you have to achieve if you want a livable climate for your children, said Dunant.
“In many ways, that’s motivation enough.”