Infrastructure projects – a calculated move to decarbonise

The new walkway at Barnes Bridge in London will be one of the most environmentally conscious bridges ever constructed by COWI in the UK.

The climate change emergency is permanently redefining the role of the structural engineer, say COWI’s Daniel Green and Cameron Archer-Jones.

The construction industry faces its own unique challenges when it comes to decarbonising. It may not be as far down the road as other sectors, but there are good reasons for that. The nature of its work and the materials that are at the core of its operations, mean it has to work harder than most to keep pace with the green transition.

There’s also a naturally conservative mindset that sees new practices, concepts and techniques reasonably treated with caution by an industry with little scope to test them in a live project environment. There are no trial phases for new infrastructure projects – they need to work first time.

Change, however, is here. Formal declarations of a climate and biodiversity emergency across the built environment have certainly served to focus minds within our discipline on the multiple ways in which we can contribute to wider sustainability goals. Structural engineers at COWI became signatories to the pledge in 2019 and – like many others in our profession in the UK – began exploring new approaches.

It was the following year, when we were working together on a mega-project project in Mumbai, that it first struck home that we had an opportunity to contribute to decarbonisation in a big way. The work entailed the use of tens of thousands of tonnes of steel, and as part of the design optimisation process, we started framing material savings in terms of carbon equivalents for context. The implications were startling.

Briefly consider the example of a single steel plate in a bridge construction project. 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. Put simply, saving one tonne of fabricated steel on the project was equivalent to saving around 360kg of farmed chicken, a 9,100km journey in a car, or one economy seat on a flight from London to Sydney.

Carbon conversations – making them easy

We took two big learnings from that initial exercise. First, that converting carbon savings into relatable terms – everyone understands food, flights and family cars – would be hugely helpful in promoting these principles among colleagues, developers or contractors. Second, that as construction professionals focused on design, our impact in terms of carbon reduction was an order of magnitude greater than our everyday personal contributions. We could all make a difference – a big difference.

It was the catalyst for us to move forward with a practical measure that’s now in common use across COWI’s UK operations. We put together an easy-to-use carbon calculator that takes publicly available data on the CO2 emission factors associated with specific materials and practices and multiplies it by our estimated project quantities derived throughout project execution. By structuring the calculation around distinct design elements, we can present a meaningful picture of the carbon footprint associated with each dimension of the project. We can show how the design process has already helped keep that footprint to a minimum and this often highlights how we can collaborate with the client to reduce it further.

Carbon considerations – all part of the job

In our view, carbon calculation 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. We’ve also seen refreshing signs of the spirit of cooperation on this fundamentally important topic. In the past year, we have joined the Net Zero Bridges Group as founding members and we are now working collaboratively with like-minded peers to share experiences and best practice across the UK structural engineering community. Indeed, we’ve even published some of our own data publicly to help others when they consider benchmarking their projects.

Certainly, within our organisation, the calculation tool has been positively received by teams and at the end of 2021 more than 30% of our live UK projects were having a carbon score applied to them. We also have dedicated champions in each department focusing on carbon opportunities specific to their field. Our stretch goal is now to have a live carbon calculation on all our infrastructure projects by the end of 2022.

We’ve also adapted our approach to the design process to ensure we introduce carbon assessments at an early stage, whenever possible, and advocate for its consideration in decision-making. Of course, many key decisions lie with the client, however we have found that they’re typically already engaged with the issue so there’s generally little pushback and a genuine willingness to consider the opportunities.

This positive environment is augmented by the reality that many aspects of carbon reduction produce cost savings as it often entails greater scrutiny on materials and elimination of waste. Whatever the impact on project economics, the carbon impacts presented by the engineer are becoming a noticeably more powerful influence against the backdrop of our client’s own green objectives, compliance requirements and reputation.

That topic of associated gains was highly pertinent when we were asked to support the installation of a new TV and radio mast in a remote location last year, after the original was destroyed by fire. With swift restoration of a TV signal the priority, the original proposal had been to simply replicate the design of another new mast recently installed by the client. We sought a little time to come up with a lower-carbon alternative, deploying the calculation tool. The result? A design which made the construction programme faster and safer because of the lower volumes of steel involved. For us, it represented another step away from the conventional way of doing things – and showed how it’s possible to realise benefits beyond the carbon dividend.

A key advocacy role for engineers

Of course, the prospective contribution of the structural engineer in design is only one small part of a carbon reduction landscape. Whole-life carbon assessments are crucial at a strategic level, taking into account systemic impacts from new infrastructure, as are material advancements and new regulatory and stakeholder pressures to respond to environmental issues.

That landscape, however, is rapidly evolving and therefore daunting for many of the traditional players. 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. We believe that 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 UK-based principal bridge engineers with the global consulting group, COWI.