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Embodied carbon, the hidden emission in infrastructure

The importance of considering embodied carbon on infrastructure projects

The term “embodied carbon” has been gaining significant attention in recent years. You are likely familiar with it if you work in the building industry, especially if you live in Vancouver and have rezoned under the City’s progressive green building policies. If, like me, the bulk of your experience is working in the transportation, municipal or environmental infrastructure sectors, you may be considering how and why you should incorporate embodied carbon considerations into your projects. In writing this article I hope to provide some clarity, direct you to some resources, and ultimately, increase your knowledge on the emerging world of embodied carbon reduction.

Embodied carbon refers to the total greenhouse gas emissions caused by the extraction, manufacture and supply of construction products and materials, as well as the construction, maintenance, and end of life disposal processes. Think concrete materials extraction, manufacturing, mixing, transport to site, installation, demolition, and disposal. According to the United Nations Environment Program, embodied carbon of building materials represents 11% of global emissions. Concrete is the most abundant man-made material in the world, and cement production creates 7% of global emissions. These are not small pieces of the pie. While much of the world’s attention is on reducing operational emissions and decarbonizing energy grids, the share of embodied carbon emissions is expected to grow. Countries with a significant proportion of renewable energy have already reached a point where embodied carbon is exceeding operational emissions. As governments around the world wrestle with aging infrastructure, population growth, and urbanization while working towards meeting Paris Agreement commitments, increased focus and energy is being put into embodied carbon, as it should.

Full lifecycle analysis diagram
Courtesy of Kingspan

It is essential for embodied carbon to be considered over the full life cycle of a project. Selecting materials or products with relatively low emissions to manufacture and transport may have poor durability, leading to emissions from maintenance, repair, and replacement. Companies like Priopta in Vancouver are leading the way in the building sector, developing Life Cycle Assessments (LCAs) to inventory a building project’s materials and calculate the total emissions associated with the extraction, transportation, manufacturing, and disposal over the useful life of the material. A growing number of products now have third-party verified Environmental Product Declarations (EPDs) available, containing carbon footprint data for use in the LCAs. LCAs allow project teams to make better choices, like using less carbon intensive materials, sourcing local, using materials more efficiently (less waste), or using recycled products. In addition to emissions reduction, these choices often lead to reduced project costs, as with the UK’s M25 highway upgrade project. Not only does specifying local materials support the local economy, increasing demand for low carbon materials helps position Canadian companies as innovative leaders in these products, including for potential export.

Calculating the embodied carbon on infrastructure projects in Canada is currently voluntary, but look for that to evolve in the coming years. Already the federal government’s infrastructure funding requires applicants to submit climate lens assessments to evaluate emissions. The Canadian Collaboration for Sustainable Procurement, a member-based network of Canadian public-sector institutions working together to align their spending with their values and commitments on sustainability, has identified green building materials and road construction as high impact opportunities for 2020. Progressive infrastructure owners understand the benefits and are considering embodied carbon on their projects, often using tools such as the Envision Sustainable Infrastructure Framework. The National Research Council of Canada is developing an inventory of LCA values for construction materials such as steel, wood, and concrete to establish guidelines and tools for conducting LCAs. Through my discussions with the BC Ministry of Environment, I learned this work is expected to conclude in 2023 and will inform the development of LCA tools for public procurement. Under the City of Vancouver’s green building policies referenced above, rezoning projects are required to complete LCAs. Through my discussions with Priopta Principal Anthony Pak, I learned the City of Vancouver is considering bolstering the LCA requirement by introducing a minimum embodied carbon reduction requirement.

In Sweden, the national transport agency implemented a 2015 policy to require all new projects with a budget over 50M kr (approximately $7M CAD) to report, reduce and document greenhouse gas emissions and energy use throughout project delivery. They are even awarding bonuses to project bidders that beat prescribed target carbon performance. For products, they have policies to reduce embodied emissions from procured materials, requiring suppliers to perform better than a minimum level. Similar carbon performance-based procurement systems are being considered by governments around the world.

Of course, considering embodied carbon comes with unique challenges. At this point, limited data is available for the carbon intensity of infrastructure products and materials, however progress is being made. Projects often involve thousands of products, making it very onerous to quantify. Focusing on major materials like concrete/cement, steel and aggregates is a good place to start. For context, consider the Port Mann Highway 1 Project, a BC project I spent several years on. The Port Mann Bridge alone, not including the 37km of highway widening, interchanges etc., required approximately 157,000m3 of concrete. Assuming an embodied carbon value of 350kg CO2 eq/m3 of concrete, the bridge’s concrete represents approximately 55,000 tonnes of CO2e, equivalent to about 12,000 average Canadian cars on the road for one year.

LCAs and embodied carbon considerations also add a layer to already complex project decision making. Considering embodied carbon early in a project’s life cycle is the most efficient and cost-effective way. Education and mindset shifts are key.

Accurate calculation of embodied carbon over a project’s life cycle is challenging. But calculating it, tracking it, and diminishing it is the right thing to do for the environment, taxpayers and the economy. In the future, project professionals and governments will ensure that the embodied carbon of the built environment is as low as possible, for the benefit of us all.



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