Building the future: Reducing carbon footprints across the entire infrastructure lifecycle

Projected population growth and urbanization worldwide will drive significant development, making the shift toward low-carbon infrastructure more crucial than ever. The global building stock is projected to double its current floorspace, adding another 241 billion square metres during the next four decades. This is the equivalent of adding an entire New York City to the world every month for 40 years.

UN Secretary General Antonio Guterres has estimated that three-quarters of the infrastructure required to support these buildings and their inhabitants by 2050 still does not exist.

These projections are compounded by the fact that the emissions from just four major materials used in infrastructure projects – cement, iron, steel and aluminium – are responsible for 7.3% of annual global CO2 emissions, according to Architecture 2030 analysis of IEA data. Infrastructure is responsible for nearly half of global cement emissions and over a quarter of the global iron, steel and aluminium emissions.

Understanding how to reduce infrastructure’s environmental impacts requires an understanding of its lifecycle: from the product stage (material extraction, manufacturing, and transportation) to the construction stage, the use stage and finally, to its end of life. Strategies and policies can be implemented to address the environmental impacts at these different stages of this lifecycle.

A growing policy trend in low-carbon infrastructure is “Buy Clean” procurement, which focuses on material-related carbon impacts. According to the Carbon Leadership Forum, these policies are being adopted by states, local governments and federal agencies, primarily in the building and infrastructure sectors. By using Environmental Product Declarations (similar to nutrition labels but for carbon), these policies help stakeholders choose lower-carbon materials without sacrificing durability or performance.

For example, early this year, Washington State Governor Jay Inslee signed the landmark Buy Clean, Buy Fair legislation, which addresses embodied carbon by requiring reporting on the environmental and workforce impacts of the production of materials used in state construction projects.

Key provisions include:

Procurement policies like Buy Clean are a great start but only cover the product stage of the life cycle. The construction of infrastructure, with trucks, cranes and other equipment, also contributes emissions. General contractors are beginning to implement strategies to reduce these impacts by using alternative fuels, reducing idling time and reusing materials onsite, among other things.

The Sustainable Construction Leaders group has created the Contractors Commitment to Sustainable Building Practices to help these organizations quantify, measure and prioritize such measures.

A key strategy for creating low-carbon concrete is to reduce the amount of cement, the most emissions-intensive ingredient.

The team delivering the new Seattle Storm Centre for Basketball Performance – Sellen Construction, Stoneway Concrete and ZGF Architects – found a way to do this. They extended the curing time for the concrete used in the foundations and walls from 28 days to 56 days, allowing them to use less cement while still achieving the needed strength.

The project achieved 40% fewer carbon emissions than average mixes in the region and 80% of the 2030 targeted reductions in the First Movers Coalition for Concrete.

The next phases of the infrastructure life cycle include operations, maintenance, and repair. The Institute for Sustainable Infrastructure has developed Envision, a sustainability framework and rating system, to provide consistent methodologies for defining and measuring what constitutes sustainable infrastructure, including greenhouse gas emissions, during project operation.

Several local governments, including Miami-Dade County and the City and County of Los Angeles, have begun using Envision as a framework for their efforts.

Additionally, the American Society of Civil Engineers’ Infrastructure 2050 programme was created, in part, to help engineers understand and meaningfully account for the environmental impacts of maintenance and repair efforts over many years.

Infrastructure covers many systems spanning bridges, tunnels, roadways, aviation, utilities, ports and more. Each system’s maintenance and repair efforts vary significantly. For example, the structure of a transportation tunnel is typically designed for watertight conditions across a typical 100+ year lifespan; maintenance and repair efforts are more frequently associated with the fit-out systems and equipment inside the tunnel and less are associated with the structure itself.

However, due to degradation from weather and use, the structure of a typical bridge can undergo significant maintenance and repair efforts across its 40+ year lifespan. In addition, a lack of preventative maintenance can significantly worsen the level of future repairs needed, frequently leading to increased costs and traffic delays.

Missouri-based HNTB worked with the West Virginia Parkways Authority to develop sustainable preservation strategies such as bridge washing and deck sealing that increase the service life of their bridges, delaying the need for major rehabilitation or replacements and thereby reducing their overall carbon footprint.

Lastly, there is the end-of-life stage of infrastructure. What happens to that investment once the infrastructure has performed its “useful life,” which it was designed for? Is the project demolished and its materials landfilled, contributing to emissions or was it designed for deconstruction and are its materials put back into a circular economy model?

At Ellinikon Park, a massive project to transform an obsolete airport into a massive coastal park in Athens, Greece, Sasaki’s team of landscape architects, planners, and others set out to repurpose everything possible to minimize the project’s carbon footprint. More than 300,000 square feet of concrete from existing tarmac and runways are reused as part of the park’s story about its past uses.

As we move forward, embracing low-carbon infrastructure will be essential to achieving global climate goals and ensuring sustainable development.

The World Economic Forum’s G20 Smart Cities Task Force took on the effort to create a Whole Life Carbon Assessment Mandates Model Policy to help cities take a decisive step to reduce the carbon footprint of their built environment and reach their climate-neutrality and net-zero emissions targets.

Can the evolution of building-level decarbonization policy inform a whole-life carbon approach for infrastructure? The Forum’s newly released report, Implementing a Lifecycle Approach to Infrastructure: A Policy Roadmap for Cities, aims to answer this and other questions, balancing short-term and long-term impacts on essential infrastructure needs around the world.