Our modern world continues to be built on physical foundations that would have been all too familiar to the ancient Romans: cement and concrete. These products loom large across the entire spectrum of civil engineering, which annually consumes twice as much concrete and cement as all other building materials combined. Their production has consequently assumed the form of a classic smokestack industry, taking advantage of the economies of large-scale output in order to turn out a widely used product at the lowest possible price. 

Not surprisingly, those large smokestacks serve as beacons for environmental criticism, much of which is well earned. The high heat in a cement kiln has traditionally been generated with coal and petroleum coke, both prime sources of pollution such as sulphur oxides (SOx) and nitrogen oxides (NOx). Moreover, cement manufacturing accounts for about five percent of greenhouse gas emissions, an airborne testament to the industry’s significance in the global economy.

Rob Cumming of Lafarge Canada

The most effective approach to tackling these problems would be to introduce alternative low-carbon fuels. In theory, biomass and recycled material can substitute for coal, replacing a non-renewable fossil fuel with renewable commodities that might otherwise simply wind up decomposing elsewhere. In practice, life is somewhat more complicated. Just ask Rob Cumming, the Environment and Public Affairs Manager for Lafarge Canada’s cement plant on the northeastern shore of Lake Ontario in the town of Bath. For the past decade, he has watched the provincial government phase in its Industry Emissions Reductions Plan, which continues to ratchet down SOx and NOx emissions. Looking ahead to national and international regulations of CO2 emissions, Cumming was active in the formation of the Cement 2020 program, which is becoming an industry-wide initiative to bring low-carbon fuels into the cement-making process over the next few years.

The Bath plant is preparing to demonstrate just how this strategy could work, starting with a pilot operation to stoke the kiln with discarded railroad ties, roofing shingles and waste material collected from construction and demolition sites. Cumming notes that the life-cycle carbon emissions from these items are half as much as coal or less — a working definition of low-carbon fuel — and burning them for a purpose keeps them out of the conventional waste stream. “It’s a real problem for municipalities, which would otherwise put these things in landfill,” he says. 

Lafarge has assembled upwards of $9 million to operate this test facility, which includes a $2.7 million grant from Natural Resources Canada’s EcoEnergy Industrial Initiative. Another $400,000 grant from the non-profit institute Carbon Management Canada has supported researchers at nearby Queen’s University in Kingston, Ont., who have helped map out the design of the pilot plant and worked through the details of how the combustion of these alternative fuels should occur. 

Lafarge Canada’s Bath operations near Lake Ontario wants to become a model for how the cement industry can be both environmentally sound and economically competitive. Photo credit: Lafarge Canada Inc.

Lafarge’s Bath site marked its 40th anniversary last year and Cumming is eager to show how a 1970s installation can be upgraded to meet the environmental expectations of the 21st century. He wants nothing less than a model operation pointing the way for the entire Canadian industry, which currently produces 10-14 million tonnes of cement every year from a handful of major operations located across the country. 

The scope of that industry is almost immediately apparent from the vast scale of the Bath plant. You feel dwarfed just setting foot on the property — the massive inclined tube of a kiln looms overhead, surrounded by grinding mills several storeys high and storage sheds that cover whole hectares of raw material. And somewhere in behind the factory is a sprawling quarry, looking much like a geological work-in-progress. 

The production of cement here follows a textbook formula, albeit one writ very large. Quarried stone and clay are placed in a gently inclined, rotating kiln that measures some 200 metres in length and six metres in diameter. A large flame of about 3,000 C at one end of the kiln generates radiant heat throughout the interior, averaging 1,400-1,500 C in a crucial region called the “burning zone.” As the material makes its way down the incline, it changes from simple calcium carbonate to a series of different mineral phases, including tetracalcium alumino ferrite (4 CaO•Al2O3•Fe2O3), tricalcium aluminate (3 CaO•Al2O3), dicalcium silicate (2 CaO•SiO2) and tricalcium silicate (3 CaO•SiO2). 

The long cylindrical tube of the kiln is a dominant feature of the Lafarge cement operation in Bath, Ont. Limestone and clay go in one end and “clinker” — nodules of various calcium silicates that will be ground up to form cement — come out the other. Photo credit: Lafarge Canada Inc.         

The resulting nodules are cooled and ground into the fine powder known as Portland cement, the most common version found at building sites in every corner of the globe. Chemical additives may alter the makeup slightly for specific applications, such as increasing or decreasing the setting time after mixing with water, but the base product remains essentially the same. Concrete, for its part, consists of cement and aggregate to form a synthetic stone.

As the industry finds itself increasingly in the crosshairs of environmental legislation mitigating SOx, NOx and carbon dioxide (CO2) emissions, proponents have turned to the concept of life-cycle analysis in order to place the impact of cement in a broader context. “Of the total energy that goes into a building over its service life, only 10 percent, if that, is in the initial construction,” says Richard McGrath, director of codes and standards for the Cement Association of Canada. “Yet that is where the focus of legislators and the public has been, because it’s easy to quantify.” For example, the cement industry will be held accountable for the CO2 emissions generated by producing the material that goes into a new building. But there may be no subsequent calculations to take into account the CO2 emissions associated with the heating or cooling of that building over the many decades it will be occupied. According to Adam Auer, the Cement Association’s director of sustainability, this latter set of emissions overshadow any contribution from the cement that went in at the beginning. For that reason, Auer warns that focusing only on the front-end of a building’s life can easily lead to construction policies that are penny-wise but pound-foolish. “Even if you could get the embodied CO2 of your building materials down to zero, it would hardly make a dent in solving the real impact of that building,” Auer says. He adds that it is bound to be more expensive to build a more durable, energy-efficient structure but this is the only approach that will reduce emissions over its complete service life.

In reality, the embodied CO2 cannot be altogether eliminated, but it can be substantially reduced. The industry already conducts dedicated marketing of products with a reduced carbon footprint; for builders with an eye toward advanced environmental certification such as Leadership in Energy and Environmental Design (LEED) ratings, this kind of cement will contribute toward that qualification and therefore should be highly attractive. 

The success of such products in the market assures Cumming that Cement 2020 is on the right track and the pilot plant at Bath will show the way forward. “There are no other projects where you’ve got this many fuels, with before-and-after testing and with life-cycle assessments done on each of them,” he says, adding that public meetings with the local community have made the entire research undertaking as transparent as possible. “Any one of these fuels is already in use. All of them are less expensive than coal. So if our industry can have lower cost fuels, produce some local jobs to replace imported fuels with locally produced fuels and reduce our carbon emissions, then we can keep our cement industry competitive for years and years to come.”

You can still find sturdy examples in Europe where the Romans used these very same materials thousands of years ago. Such dramatic artefacts speak to why we continue to prefer cement and concrete but they also illustrate why it is hard to confront the pollution associated with their manufacture. Lasting for decades, centuries and even millennia, these edifices continue to have some environmental impact throughout their lifetime. Such enduring monuments to a culture shouldn’t compromise the wellbeing of the environment where they stand.