Construction megaproject

How structural engineers are playing their part in tackling the climate emergency

Image credit: Direk Takmatcha/Dreamstime

Assessing carbon emissions from the start of a construction project through to completion can help make a significant contribution to minimising environmental impact.

The construction industry faces its own unique challenges when it comes to decarbonising. The nature of its work, and the materials that are at the core of its operations, means it needs to work harder than other industries to keep up with the green transition.

According to Built Environment Declares - a global petition that serves as a public commitment to take positive action in response to climate breakdown and biodiversity collapse - the sector desperately needs a paradigm shift. It states: “If we’re to reduce and eventually reverse the environmental damage we’re causing, we will need to re-imagine our buildings, cities and infrastructures as indivisible components of a larger, constantly regenerating and self-sustaining system”.

Structural engineers at COWI became signatories to the pledge in 2019 and we have since begun exploring new avenues to decarbonise the industry. Our journey began while we were delivering the design for a mega-project in Mumbai to construct India’s longest sea-crossing bridge. The project required tens of thousands of tonnes of steel, and as an experiment we started framing material savings in terms of its carbon dioxide equivalent. Think of a typical single steel plate that might form a small part of a bridge structure: from mining as iron ore through smelting, casting, rolling, fabrication and finally delivery to site for installation, the plate will have gone through multiple highly carbon-intensive phases. Saving one tonne of fabricated steel on the project was equivalent to saving around 360kg of farmed chicken, a 9,100km car journey, or one economy seat on a flight from London to Sydney.

We took away three key lessons. First, raw numerical carbon quantities do not mean much to our stakeholders. Most have limited prior experience of this field and therefore it is important to think about how we present our findings in order to provide some context. Second, as construction professionals focused on design, our impact in terms of carbon reduction is significantly greater than our everyday personal contributions. Finally, many gains associated with carbon reduction are also associated with lower cost; for example, using less carbon-intensive materials, waste elimination and improved structural efficiency.

This one-off exercise was the catalyst for us to move forward with a practical measure that’s now in common use across COWI’s operations. We launched an easy-to-use carbon calculator that combines publicly available data on carbon dioxide emission factors with our project quantities, derived throughout project execution. The calculator is flexible enough to support preliminary carbon assessments and we introduce these evaluations at an early stage to support early-stage decision making.

Even better, we have structured our tool so we can automatically log carbon across all our portfolios and attribute it to the distinct design elements that make up each project. We can present a meaningful picture of the carbon footprint associated with each dimension of a project or similar elements across a range of projects. This growing database is forming the basis of a research programme that is enabling us to develop evidence-led heuristics for carbon in infrastructure.

At the end of 2021, more than 30 per cent of our live UK projects were subject to carbon monitoring and we are on target to include all our live infrastructure projects by the end of 2022. This work supports our firmly held belief that carbon calculation must be embedded in our processes. It is a natural extension of the structural engineer’s role in the era of climate change and should be viewed as inseparable from everyday design work.

Of course, the prospective contribution of the structural engineer in design is only one small part of the carbon-reduction landscape. Whole-life carbon assessments are crucial at a strategic level and we’ve seen refreshing signs in the spirit of co-operation. We’ve joined the Net Zero Bridges Group as founding members and are now working collaboratively with like-minded peers to share best practices across the UK structural engineering community.

As a profession embedded throughout the infrastructure delivery process - from conception to construction, operation to demolition – our belief is that we are uniquely placed to advocate for positive change. As an engineering community we should approach this climate emergency with clarity, purpose, and a great deal of hope.

Daniel Green and Cameron Archer-Jones are based in the London offices of consulting group COWI.

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