Greening Canada’s Concrete: Cement Emissions, Innovations, and Alternatives
By Denis Koshelev
Canada’s cement industry faces mounting pressure to reduce environmental impacts while meeting growing infrastructure demands. The Ordinary Portland Cement (OPC), the most common type of cement, produces approximately 7% of global carbon emissions, while innovative solutions like green cement technologies offer significant emission reductions. Canada is projected to produce approximately 55 million tonnes of cement over the next five years, averaging about 11 million tonnes annually, representing a significant environmental footprint that could be dramatically reduced through the adoption of alternative materials, including biochar supplementation, which can improve concrete strength by 3-13% while sequestering carbon. [2]
The industry stands at a critical juncture where emerging technologies present viable pathways toward sustainable construction practices. But what is green cement — and can it make Canada’s future greener?
Concrete: The Canadian reality
Cement production begins with heating a precise blend of limestone, clay, and sand in a rotating kiln to over 1400ºC. This high-temperature process creates cement clinker, an intermediate material. After emerging from the kiln, the clinker is cooled and then finely ground into the familiar powder we call cement. The fuels used to heat the kiln are responsible for approximately 40% of cement manufacturing’s emissions. The remaining 60% are “process emissions,” which are chemically intrinsic to cement production and effectively unavoidable without carbon-capture technologies. [17]
Over the past three decades, the Canadian cement and concrete industry has reduced its carbon footprint through various initiatives. The industry has formalized its commitment in Concrete Zero: Canada’s Cement and Concrete Industry Action Plan to Net-Zero. This Action Plan outlines clear targets for 2030 and 2040, includes a progress review scheduled for 2025, and emphasizes accountability and transparency with all stakeholders.
The main players in Canada’s industry include Lafarge Canada, CRH Canada Group, Heidelberg Materials, Ciment Quebec, Votorantim Cimentos North America, and Federal White Cement. Canada is a significant producer of cement, with production volumes fluctuating over the years. In 2018, Canada’s cement production reached 13,554,063 metric tons, marking an increase from 12,705,518 metric tons in 2017. [5] Looking forward, Canada is projected to produce approximately 55 million tonnes of cement and 400 million tonnes of concrete over the next five years. This anticipated demand is driven by factors such as population growth, urbanization, economic development, and significant investments in new and retrofitted infrastructure. [2]
Cement production is a significant global contributor to greenhouse gas (GHG) emissions, responsible for approximately 7% of the world’s total. In 2019, cement manufacturing accounted for roughly 26% of all industrial GHG emissions worldwide. The majority of these emissions stem from two key sources: the chemical reactions involved in transforming limestone into clinker and the combustion of fossil fuels needed to generate the extremely high temperatures (around 1,450°C) required for this conversion.
Canada’s cement industry also contributes substantially to the nation’s overall GHG emissions. According to data from Canada’s Greenhouse Gas Reporting Program, cement production facilities released 11.2 megatonnes (Mt) of carbon dioxide (CO₂) in 2019, representing approximately 1.5% of Canada’s total emissions. [6]
Certain steps are being made in Canada to improve the situation. The Concrete Zero Action Plan is an initiative by the Cement Association of Canada to help the cement and concrete industry in Canada reach net-zero emissions by 2050. The plan outlines decarbonization pathways for the cement industry, including eliminating the use of coal and petroleum coke, increasing the use of alternative and blended cements, improving thermal efficiency, investing in carbon capture, utilization, and uptake technologies, increasing the use of clean energy, and advocating for performance-based codes and standards. The Concrete Zero Action Plan shows that emissions reductions of 40% by 2030, 59% by 2040, and net-zero by 2050 are possible using today’s technologies.[18]
The Canadian government, working with Heidelberg Materials through Innovation, Science and Economic Development Canada, is pioneering North America’s first full-scale commercial carbon capture, utilization, and storage (CCUS) system within the cement industry. This groundbreaking Edmonton facility is projected to cut greenhouse gas emissions by up to one million tonnes annually, a reduction comparable to taking over 300,000 passenger vehicles off the road. [19]
The Lafarge Richmond cement plant in British Columbia has successfully entered the second phase of its CO2MENT project, which involves capturing and efficiently reducing the amount of CO₂ emissions released into the atmosphere using Svante’s advanced equipment. In January 2023, the project reached a significant milestone, surpassing 2,400 hours of operation with a 90% CO₂ recovery rate, a CO₂ purity of 95%, and an on-stream factor of over 75%. The operating data will serve as a basis for a feasibility study to assess the viability and design of a commercial-scale system to capture 1.5 million tonnes of carbon dioxide per year at additional Holcim projects in the US. [20]
The primary obstacle to widespread CCUS adoption in the cement industry remains its high cost, which has historically been a significant barrier to commercial application. The vast scale of cement production also presents logistical challenges in identifying and securing adequate CO₂ storage sites. Furthermore, the transportation of captured CO₂ can be a costly endeavour. [21]
Understanding Green Concrete Technology
Green concrete is an environmentally friendly alternative to traditional concrete, designed specifically to reduce its environmental impact throughout its life cycle. Unlike conventional concrete, which relies heavily on natural resources like limestone and clay and generates significant carbon dioxide emissions during production, green concrete incorporates recycled materials and recycled aggregates from construction or industrial waste. The primary ingredients of green concrete are recycled waste materials. These can include blast furnace slag, recycled glass aggregate, and fly ash, a by-product of conventional concrete production, construction, and mining. Unused concrete, broken down into a hardened granular form, can also be used as a partial replacement for fine and coarse aggregate. [7]
The production of green concrete addresses waste management by diverting industrial by-products from landfills and reusing demolished concrete, further contributing to resource conservation and sustainability.
Its designation as “green” stems from manufacturing processes specifically engineered to minimize emissions, particularly CO₂, during critical operations such as clinker (a cement precursor) production. This innovative material directly addresses pressing environmental concerns by aiming for a carbon-negative manufacturing process or achieving a near-zero carbon footprint. The adoption of green cement technologies can lead to a substantial reduction in carbon footprint, potentially by as much as 40%. [4]
A primary pathway to achieving green concrete involves the use of green cement. Green cement offers more than just environmental benefits; it often outperforms OPC in key performance areas. Engineered for both lower emissions and maintained or improved structural integrity, green cement boasts desirable properties like excellent sulphate attack resistance, high early strength, resilience, enhanced durability, crack resistance, and low chloride permeability. Its corrosion resistance is significantly superior, being three to four times greater than OPC, and it withstands twice the number of freeze-thaw cycles, making it ideal for varied climates. Certain green cements, like Ceratech’s, develop a dense crystalline structure called calcium silicate aluminate hydrate (CASH) during hydration, contributing to their strength. Moreover, using calcined clay and powdered limestone in the composition can further reduce porosity and boost mechanical strength. [4]
The emphasis on both environmental and performance advantages for green cement suggests a significant shift in its market positioning. It is not merely a “green” alternative but a technically superior material in many respects. This dual value proposition — environmental sustainability coupled with enhanced material performance — could be a powerful driver for adoption. It allows manufacturers and consumers to justify investment not just on environmental mandates but also on the basis of a better, more resilient product.
Can We Recycle Concrete?
Recycling concrete is a highly viable and beneficial practice for sustainable construction, offering substantial environmental and economic advantages. Both asphalt and concrete are 100% recyclable materials. Economically, concrete recycling offers lower direct project costs. For instance, a 20% recycling rate by municipalities in Ontario could result in annual cost savings of $264 million. [22]
Concrete production often incorporates chemical additives, known as admixtures, to precisely control its properties. These substances can entrain air, reduce water content, modify viscosity, and fine-tune other performance characteristics. To strengthen the bond of cement, manufacturers also integrate supplementary cementing materials (SCMs). These SCMs, valuable by-products from various industrial processes, offer a dual benefit: they prevent materials from ending up in landfills, thus extending their economic utility and significantly advancing the shift towards a circular economy.
Beyond these material innovations, commercially viable carbon utilization and storage technologies are already transforming concrete production. These systems capture waste carbon dioxide from industrial sources and inject it into concrete, thereby making the material more environmentally sustainable. [17]
Research on demolition waste management in Canada reveals that construction and demolition waste accounts for 27% of all municipal solid waste in landfills. Crucially, the same study identified that approximately 75% of this solid waste possesses inherent value and is suitable for reuse. [16] Recycling concrete stands as a primary strategy for managing demolition debris. This procedure transforms removed concrete and other components into gravel-sized aggregates. Once concrete is removed, this durable material can be pulverized and transformed into new aggregate. This robust nature, coupled with concrete’s extended lifespan, makes it an exceptionally valuable resource for recycling.
There is a clear and significant point in recycling cement from old buildings or roads, though it’s important to clarify what is being recycled. When concrete structures are demolished, the material that is typically recycled is concrete, not pure cement. Cement is the binding agent in concrete, and once it has been used and cured, it cannot be separated and reused as fresh cement. Instead, the recycling process involves crushing the old concrete to produce aggregates that can be used in new construction projects. [8]
Recycling concrete offers several environmental and economic benefits. It reduces the amount of waste sent to landfills, conserves natural resources by decreasing the need for new raw materials such as gravel and sand, and saves energy compared to producing new aggregates. Recycling one tonne of concrete could save 6,182 litres of water and 900kg of CO₂, primarily by avoiding the emissions associated with extracting and processing virgin aggregates. [9]
Recycling concrete offers significant benefits: first, it conserves virgin aggregate resources, mitigating the environmental impact of extraction and transportation. Second, it diverts valuable material from landfills, allowing for its reuse in new projects. However, concrete recycling does not significantly reduce greenhouse gas emissions. The majority of emissions in concrete’s lifecycle stem from cement production, and the cement within concrete cannot be efficiently separated and recycled back into new cement.
Currently, most recycled concrete finds use in road sub-bases and civil engineering, which, in most situations, represents the most sustainable application.
Despite the limitations in emission reduction, strategic planning during building design, thoughtful renovations, and well-managed demolitions can maximize concrete recovery and reuse. This contributes significantly to creating more sustainable buildings and future urban environments.[8]
What other materials can be used instead of cement for road construction?
Several alternatives to cement are being explored for road construction to address environmental concerns and reduce carbon emissions. Industrial by-products and recycled materials such as rice husk ash (RHA), brick dust (BD), marble dust (MD), stone dust (SD), fly ash (FA), limestone dust (LD), and silica fume (SF) are commonly used as partial or complete replacements for cement in road base layers and concrete mixtures. Tests indicated that LD and SF mixtures offered a marginal improvement in mechanical strength and durability over OPC-based mixtures, positioning them as viable substitutes for cement in concrete road applications. [10]
Geopolymer binders, which use aluminosilicate sources like fly ash, slag, and ground glass fibres activated with alkalis, have also demonstrated promising performance as full replacements for Portland cement in road stabilization and base applications. [11]
Biochar is another viable candidate for reducing cement usage in concrete. Biochar can reduce cement usage in concrete by acting as a pozzolanic material and improving the strength development of the mortar. Its porous structure and high surface area help in the formation of new cementitious compounds, leading to increased strength and reduced environmental impact. The use of biochar as a cement substitute can contribute to more sustainable construction methods and help mitigate the adverse environmental effects of cement production. [12]
Studies have shown that at low replacement rates — typically between 0.5% and 6% by weight — biochar can enhance certain mechanical properties of concrete. Using biochar in concrete is a promising approach for producing eco-friendly and cost-effective concrete for structural applications. Further research is needed to understand the influence of contaminated biochar on the durability of concrete and reinforced concrete beams and to evaluate the effect of biochar on the demand for water reducers to ensure adequate flowability and constructional performance. [13]
Engineers at the University of Colorado Boulder have developed a new method for producing carbon-neutral cement using algae. The researchers used coccolithophores, single-celled microalgae covered in microscopic plates made of calcium carbonate. When these organisms shed their plates, they send calcium carbonate to the deep ocean. The team used coccolithophores to grow calcium carbonate as a limestone alternative, which can be used to make concrete. Although the process still requires heating, it has a smaller environmental impact since it doesn’t need to be quarried, and the growing process sequesters carbon. The unique advantage of coccoliths lies in their origin: they are formed through coccolithogenesis, a photosynthesis-driven CO₂ mineralization process. Coccoliths act as a carbon sink, effectively storing CO₂. Utilizing these biogenic CaCO3 particles offers a novel approach to sequestering CO₂ while simultaneously improving concrete performance. [15]
While the cost-effectiveness of the method compared to traditional cement production is currently unclear, the potential benefits include a quick supply growth and reduced environmental impact. [14]
Exploring innovative alternatives to traditional concrete reveals several other options. Ashcrete, for instance, a material produced from recycled fly ash, delivers superior strength, resilience, and durability while remaining cost-effective. Another valuable by-product, micro silica (also known as silica fume) from silicon metal production, can replace a significant portion of cement in mixtures, thereby enhancing both structural integrity and corrosion resistance. Similarly, blast furnace slag, a by-product of steel manufacturing, not only boosts concrete’s strength and workability but also significantly reduces its permeability.
Beyond these manufactured alternatives, sustainable practices offer further advantages. Recycling concrete debris from demolition projects offers numerous benefits, including improved structural stability, reduced production timelines, and an immediate reduction in carbon emissions. Grasscrete integrates living grass and plants directly into the concrete, thus minimizing overall concrete consumption and improving rainwater absorption and drainage. Furthermore, incorporating recycled plastic waste as an aggregate significantly reduces carbon production and transportation costs, while simultaneously decreasing the need for heavy structural support.
Natural materials also present potent possibilities for sustainable construction. Mycelium, the intricate root-like structure of mushrooms, can be engineered into a dense, exceptionally durable, and naturally fire-resistant material, easily moldable into diverse forms. Hempcrete, derived from hemp fibres, offers a much lighter alternative to conventional concrete with superior thermal insulation properties.
Self-healing concrete, which autonomously repairs cracks through bacterial reactions, promises a significantly extended service life. Finally, bamboo, celebrated for its rapid growth and remarkable strength, stands as an attractive and environmentally sound building material, adaptable to a wide range of applications as a viable substitute for concrete. [23]
The Future Outlook
Traditional cement production is a substantial contributor to global and national greenhouse gas emissions, primarily due to the clinker manufacturing process. In Canada, cement production accounted for approximately 1.5% of national emissions in recent years, prompting a strong commitment from the industry and government to achieve net-zero concrete by 2050.
Green cement offers a promising pathway, not only by significantly reducing carbon footprints but also by providing superior performance characteristics compared to Ordinary Portland Cement.
Decarbonization efforts are multi-faceted, encompassing strategies such as Carbon Capture, Utilization, and Storage (CCUS), which is being actively piloted in Canada with substantial government support. Other critical approaches include reducing clinker content through alternative binders (SCMs), transitioning to low-carbon fuels, and improving energy efficiency. While traditional SCMs face supply constraints due to decarbonization in other industries, research into novel alternatives is accelerating.
Concrete recycling presents a highly viable and economically beneficial solution for reducing waste and embodied carbon, yet its full potential remains underutilized. Furthermore, while modern reinforced concrete structures have a lifespan of 50-100 years, limited by steel corrosion, innovations in materials like biochar offer opportunities for not only cement reduction but also long-term carbon sequestration, potentially leading to carbon-negative construction.
References:
-
https://theconstructor.org/concrete/green-cement-types-applications/5568/
-
https://www.kapre.com/resources/contractor/green-cement-future-sustainable-construction
-
https://www.ceicdata.com/en/canada/construction-materials-production-cement/production-cement
-
http://docs.wbcsd.org/2009/07/CSI-RecyclingConcrete-Summary.pdf
-
Alternative Fillers in Asphalt Concrete Mixtures: Laboratory Investigation and Machine Learning Modeling towards Mechanical Performance Prediction. Nitin Tiwari, Fabio Rondinella, Neelima Satyam, Nicola Baldo
-
Mechanical and Microstructural Analysis of Treated Tuff with Metakaolin. https://periodicos.ufv.br/jcec/article/view/19363/9871
-
Effect of Biochar and Sewage Sludge Ash as Partial Replacement for Cement in Cementitious Composites: Mechanical, and Durability Properties. https://www.mdpi.com/2071-1050/16/4/1522
-
Valorization of Vetiver Root Biochar in Eco-Friendly Reinforced Concrete: Mechanical, Economic, and Environmental Performance. https://pmc.ncbi.nlm.nih.gov/articles/PMC10056510/
-
Nucleation effects of coccoliths in portland cement. Danielle N. Beatty, Wil V. Srubar.
-
https://cement.ca/the-cement-and-concrete-industry/how-cement-and-concrete-are-made/
-
https://www.ucem.ac.uk/whats-happening/articles/concrete-alternatives/