Carbon counting: why detail matters

At the end of last month, National Highways held a webinar to update the industry on its progress against its net zero targets. Attendees also heard from three of its construction and maintenance suppliers: Balfour Beatty Highways, Tarmac and white line company WJ which manufactures materials and equipment, as well as being a contractor.

One of the strongest messages to emerge from the webinar is that we need to get more rigorous with the carbon emission data we collect – but using current counting carbon processes can be a very resource-hungry activity. Balfour Beatty Highways’ head of environmental sustainability Paul Taylor reported that it takes his team around nine months to interrogate and update the carbon data for a major highways project.

Carbon going up?

As any company which has started down the journey to measure and reduce carbon emissions knows, once you get better at counting the carbon, some emissions are likely to go up. As she reported on some of those challenges for National Highways’, Angela Halliwell, its head of carbon & air quality group, emphasised the importance of transparency.

National Highways aims to reach net zero in its corporate emissions by 2030, in the construction and maintenance activities of its supply chain by 2040 and for road users by 2050. It reports reductions in its carbon emissions against a 2019/20 baseline.

Halliwell reported that the authority’s corporate emissions had risen by 18% compared to 2023/24, largely, she said, due to some of the motorway service stations moving away from renewable energy. And, although construction and maintenance emissions were down 24% compared to the previous year, Halliwell cautioned that this was due to the type of project work being undertaken, rather than to huge changes in practices. Road user emissions were down 5% compared to the original baseline and around 1% compared to the previous year.

More rigour needed

Taylor presented on his team’s deep dive into the carbon emissions associated with the M25 Junction 10 project and also reported that Balfour Beatty is doing the same on two other big highway projects. The exercise showed that some carbon emissions had been missed in initial calculations such as non-bulk items procured by Balfour Beatty, some data from suppliers and contractors, accurate distances for transport and commuting data. There were also gaps in some of the data provided.

This exercise showed that there was a significant discrepancy in both the previously calculated baseline and the actual emissions compared to the more rigorously calculated ones. This meant that the project’s emissions were at 75% of the baseline, rather than the 45% which had been previously calculated.

One of the challenges for Balfour Beatty, and any of National Highways’ suppliers, is that the systems for submitting carbon data are manual and time consuming. “Ultimately we need to move to semi-automated or automated systems that cover our direct purchases and our subcontractor packages,” Taylor told the webinar.

Stephen Elderkin, director of environmental sustainability National Highways, acknowledged that the authority needs to work on better, less manual interfaces between its supply chains’ carbon counting systems and its own. “There’s a real risk that if it’s so expensive to do data improvement work there is going to be a backlash,” he commented.

To HVO or not to HVO?

The webinar also led to an interesting discussion about hydrotreated vegetable oil (HVO). Tarmac’s technical product support manager, Megan Thompson, told the webinar that HVO had been used extensively on its A64 project at junction 44 near Bramham – celebrated as National Highways’ lowest carbon resurfacing job. However, during the panel discussion at the end of the event, Taylor explained why Balfour Beatty did not currently use HVO, although that position is continually annually, he added.

“It comes down to market pressures on HVO,” Taylor said. “We have evidence it is leading to clearance of natural habitats to produce palm oil, to produce HVO, and we can’t support that. So, unless we can avoid that by having very clear pathways, we won’t be using it.”

Paul Aldridge, group sustainability director at WJ said that his company held the same view. “We looked at HVO and for now we are not using it,” he said.

Aldridge talked during his presentation about the importance of knowing the provenance of biogenic materials. WJ has cut the emissions associated with its white line materials by 80% by switching from a hydrocarbon binder system to a biogenic one. “These come from sustainably managed Scandinavian forests and there’s no land use change,” said Aldridge. “With some biogenic products there are a lot of unintended consequences.”

Gaining pace

The webinar demonstrated that, four years on from National Highways setting its Net Zero targets, its supply chains are rising to the challenges of counting carbon. But getting down to the detail isn’t easy.

Thermal Road Repairs gained accreditation to PAS2080 far ahead of the end-of -2025 deadline that National Highways has set for its supply chain. We find that it helps to reinforce a robust approach to carbon counting and reduction.

There is still a long way for us all to go. But we need to keep moving forward.

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Thermal Road Repairs: Road Repairs. Reinvented.

High output. Low emission. Zero waste. Permanent solution.

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Sources:

https://www.youtube.com/watch?v=Nbt7ym1wLNg