BC Focus fall 2021

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Decarbonizing cement As we move towards 2050 targets for green building, embodied carbon is increasingly important to staying under the emissions budget and limiting global warming below 1.5 degrees Celsius. What is embodied carbon? It’s the product of the materials and construction methods we choose. This value is often stretched over the life of the building to reflect durability, the idea that a building built to last is likely better than one that will need constant repairs. However, the reality is that those emissions are all fully released up front. Like netpresent value in the financial world, a ton of carbon emissions today is worth more than a ton of carbon emissions tomorrow. Of all the opportunities to reduce embodied carbon, the most significant is in concrete. Concrete is the most widely used building material, cutting across both buildings and infrastructure. And despite strong and promising market growth of alternative low-carbon materials including wood and biomaterials, concrete will continue to be a critical material for construction. POTENTIAL AS A CLIMATE SOLUTION Reducing greenhouse gas emissions from concrete is a national priority. Natural Resources Canada and the Cement Association of Canada have committed to develop a decarbonization roadmap for the industry. For the designing construction industry, there are a few significant ways to reduce emissions today, and some very promising opportunities emerging. In the immediate term, there are two opportunities to reduce emissions from concrete. The first is simply to minimize the amount of concrete projects use. This involves looking at how much concrete is required for the project and optimizing its use. This requires designers be conscious of how design choices such as massing impact material requirements. In many cases, designers are evaluating alternative low-carbon materials like mass timber to replace concrete, but nothing is as effective as just using less material. One area in relation to embodied carbon that has been overlooked is the impact of land use planning. Infrastructure like roads, sewers, and transit require concrete. There is no realistic substitution. Low-density suburban development oriented around the automobile results in huge amounts of embodied carbon, seldom considered in any municipal carbon strategies. CaGBC has been in discussions with researchers at the University of Toronto to better understand the relative carbon impacts of different development patterns, but at present there isn’t a well-established practice for evaluation. With more research we hope to understand the impact of embodied carbon from infrastructure and the importance what we build and where we build it.



The second way designers can have an impact is to specify concrete with lower embodied carbon. This can be achieved by selecting concrete that uses alternatives to cement, such as fly-ash. However, cement companies are also innovating in their manufacturing process is to minimize the emissions related to fuel use. Specification of low-carbon concrete will be aided by transparency around manufacturing practices, including the publication of environmental product declarations (EPDs). One of the most promising areas is the potential to use captured carbon in concrete. A number of emerging technologies are adding carbon dioxide into cementitious materials and aggregates. This could be a potential game changer because the sheer volume of concrete used is large enough to materially impact atmospheric CO2 with widespread adoption. It would not only reduce the net CO2 emissions from concrete but, unlike carbon sequestration, it creates an economic opportunity for carbon capture. There are still issues to be clarified, particularly around calculating the life-cycle carbon impact of these new products. We need to understand how to benchmark them against traditional concrete and understand any impacts to durability and to natural carbonation in concrete. CaGBC continues to explore this area with industry partners. We are excited to how views of embodied carbon from concrete are shifting from overlooked, to a concern, to a promising climate solution.

Jeff Ranson, Senior Associate, CaGBC