Towards net zero infrastructure

Green transition 24 November 2020 Paul Astle John Armitage

Ways you can reduce capital and operational carbon in projects, as well as seeking out the opportunities to reduce user carbon, and user energy, in the long term.

Expert columns
6 min

The importance of infrastructure cannot be overstated, it is the life blood of a modern economy. However, as with all parts of the modern world, we must find a way to construct, renew and use our infrastructure assets in a net zero future. If this were not challenging enough, we also must upgrade our infrastructure for the coming revolution in electric and autonomous vehicles, as well as increasing capacity for a growing population, with ever greater expectations.

The UK has managed to reduce its GHG emissions by 43% in the last 30 years, a significant achievement. However, transport emissions have only fallen by 3% over the same period. As of 2018(1) 60% of the UK’s GHG emissions are associated with infrastructure, with transport emissions being the single largest component at 139 MtCO2e followed by energy at 108 MtCO2e.

The UK government plans to bring forward the phase out of combustion engines to 2035, or earlier. Net emissions from power generation will need to be zero or negative by 2033 according to the National Grid(2). However, to get to net zero across the infrastructure sector we must go further.

Historically, and still today, most of the carbon associated with a piece of infrastructure is generated from its use, so called user carbon. The carbon associated with the operation and construction of a piece of infrastructure is dwarfed by user carbon. However, as we move towards decarbonising transportation and energy generation the carbon associated with its construction, the capital carbon, will become increasingly important.

Currently, capital carbon accounts for 5% of total lifecycle carbon for an infrastructure asset(3). With a shift towards net zero use and operation, the capital carbon will come to represent 100% of the carbon in 2050. However, whilst the adoption of electric vehicles will result in large reductions in vehicle emissions, we cannot rely on decarbonisation through electrification alone. Wherever possible we need to reduce the amount of energy that is required in the use of infrastructure to mitigate the need for increased electrical demand – arguably the single biggest challenge facing the government’s 2050 net zero target. In the UK FIRES Absolute Zero report(4) it has been suggested that, if we only used electricity for all of transport, heating and goods, we would require 3x more electricity than we use today. Expanding renewables as fast as possible could provide 60% of this, but we would still need to either, reduce our energy demand by 40%, or find an emission free supply to make up the shortfall.

A key aspect of reducing energy demand will be to reduce demand for infrastructure. It is clear from the home working arrangements that have been imposed upon us that, for some people, it will be possible to reduce their transportation requirements. However, the response to the pandemic has also demonstrated that there will remain a need for physical interaction, as well as huge growth in our digital infrastructure and the physical delivery of goods.

Managing Carbon

PAS 2080:2016(5) provides guidance on carbon management in infrastructure. It reflects the fact that whilst designers and asset owners can exercise control over the capital and operational carbon in infrastructure, they can also influence the user carbon. This presents opportunities for clients and designers to make a significant impact on tackling carbon in infrastructure. Ramboll is responding to this challenge by helping our clients to reduce the capital and operational carbon in their projects, as well as seeking out the opportunities to reduce user carbon, and user energy, in the long term.

Saving Bridges, Saving Carbon

We should always ask ourselves whether we really need to build. Ramboll’s Saving Bridges initiative has allowed us to extend the life of existing infrastructure, reducing carbon, disruption and waste.

The Hammersmith Flyover has served as an essential link into central London for road traffic since 1962. After 50 years of service, the bridge’s steel tendons had extensive deterioration due to the use of de-icing salts which put its operation at risk. As a result, the flyover was strengthened in critical sections in 2012 prior to a wider and ambitious strengthening solution delivered by Ramboll.

The project team used pioneering post-tensioning, construction innovation and development in materials technology to deliver a new prestressing system that effectively replaced the original one extending the lifespan of the structure by 70 years.

In addition to saving a critical infrastructure asset, the project significantly curbed Capital and User Carbon through the following measures:

  • Capital carbon: Through the application of advanced material technology, the project team was able to re-use the vast majority of nearly 8,000 m3 of structural concrete, avoiding the need for its replacement.
  • User Carbon: Any disruption in or around the structure would create increased traffic, with associated carbon emissions. By carrying out targeted interventions and, in particular, restricting the main strengthening works to below and within the bridge deck and avoiding any significant works in the carriageway, the project team kept traffic disruption to a minimum during construction.

Importantly, the project restored the bridge to its full load-bearing capacity, enabling heavy traffic transit without restrictions for the rest of the structure’s extended lifespan. Compared to alternatives, such as long-term restrictions or a replacement, this intelligent approach saved 75,000 tonnes CO2e.

Designing out capital carbon

Ramboll’s commitment to digitalisation has led to the creation of various applications designed to help consultants and clients make more informed decisions in early project stages. The latest of such applications is the 'Digital pavement tool for carbon reduction'. The tool enables engineers to calculate code compliant highway pavement build-ups based on the project requirements and assess the capital carbon implications of their decisions in real time.

The tool can link the selected build-up to an existing highway alignment and calculate total quantities by material as well as calculating the capital carbon in a design. With this information, designers and clients can quickly assess different options and select a solution with a carbon footprint that will meet the project carbon reduction targets from the design outset.

The tool represents a continuation of a paradigm shift when it comes to meeting carbon reduction targets. Historically, carbon assessments have been undertaken when a design has reached a mature level, at which point any changes to make it compliant with the carbon reduction targets can be prohibitively expensive. Tools like this provide instantaneous carbon information, which not only gives engineers a more intuitive understanding of carbon, but also provides them with more latitude to provide a low carbon solution, giving clients more certainty that carbon targets will be met.

Saving Carbon, one hill at a time

When assessing the carbon footprint of highways, the capital carbon may appear to be the largest component. However, whilst the amount of capital carbon embodied in highways is significant, the user carbon associated with emissions of vehicular traffic currently far outweighs it during the asset’s lifecycle.

With this in mind, Ramboll has once again pushed the boundaries of what sustainable solutions look like and has developed a design tool to tackle user carbon emissions and user energy in highways. FuelSave, which has been developed by Ramboll spin-off Waywize, allows designers and clients to analyse and visualise the energy, fuel and climate impact of road transportation schemes.

FuelSave allows its users to easily visualise the impact that certain design parameters have on overall emissions. For instance, it brings to light how sensitive whole lifecycle carbon figures are to highway gradients, which can be slightly counterintuitive for designers who may assume they should focus on limiting capital carbon alone. For example, on the E6 highway in Norway the team found that by choosing the optimum FuelSave alignment solution, 400,000 tonnes of user carbon could be saved on just 4km of road. Indeed, adopting lower highway gradients can result in longer alignments and higher capital carbon. However, a shallower gradient means less fuel consumption by vehicles traversing on the highway over its life, which leads to enormous savings in user carbon and energy. This trade-off is only one example of the complexity of designing low-whole lifecycle carbon infrastructure assets. It also demonstrates how we can use our influence at the design stage to reduce user carbon and energy.

Value for Carbon

In 2010 the President of the ICE, Peter Hansford, talked about a new meaning of value in infrastructure. Value for Carbon. Peter recognised that carbon had to become a key metric by which we judge our infrastructure(6). That speech was made when the UK’s target was an 80% reduction in GHG emissions with 40 years achieve it. We now need to get to net zero with only 30 years to go.

The ICE’s 2020 State of the Nation report(7) reiterates Peter’s message, ‘Clients and regulated asset managers should prioritise and elevate the value of emissions reduction impacts in procurement criteria, so it is at the same level as value for money, and health and safety outcomes. ‘ Some of the report’s key recommendations include altering the regulatory framework and criteria to specifically include the UK’s net zero target. With the much-anticipated UK National Infrastructure Strategy due imminently, value for carbon is likely to be enshrined into the decision-making process for years to come.

In Ramboll we are tackling the challenge of net zero infrastructure from multiple angles. We are extending the life of existing assets, measuring and reducing capital carbon and using our influence and insight to make reductions in user carbon. Through these measures, and by collaborating with our clients and industry partners, we can overcome the challenge of net zero infrastructure and leave a lasting, low-carbon, legacy for future generations.

This article was co-authored by Xavier Echegaray Jaile, former senior engineer in the rail infrastructure team. Xavier is currently studying for his MBA at INSEAD.  


  1. Final UK greenhouse gas emissions national statistics: 1990 to 2018. ONS. 2020.
  2. UK National Grid Future Energy Scenarios 2020. National Grid. 2020.
  3. HM Treasury, 2013. Infrastructure Carbon Review. London: HM Treasury. Interpolated from Chart 1.B.
  4. UK FIRES Absolute Zero 2019
  5. PAS 2080:2016 Carbon Management in Infrastructure. BSI. 2016.
  6. Inaugural address of Peter Hansford. ICE. 2010.
  7. State of the Nation 2020: Infrastructure and the 2050 net-zero target. ICE. 2020.


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