Decarbonizing cement

By Jeff Ranson, Senior Associate, CaGBC

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 net-present 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.