Road materials are a challenge to decarbonise. Composed of heavy, often sulphurous fractions of crude oil, bitumen and the asphalt produced for road building can be carbon intensive to create and when heated before being applied. Despite the challenge, the UK government is supporting a series of trials into more sustainable road infrastructure projects, as pressure mounts to reach emission targets.
The government has pledged to reduce emissions by 68pc by 2030 and reach a net zero economy by 2050, carefully balancing net zero commitments with a pledge for stronger economic growth. The UK is not on track to reach its targets, says the Climate Change Committee (CCC), a non-departmental government body, suggesting the pressure to adopt more green technologies will only increase.
Government policy for decarbonising roads has been in place for a few years already. The Net Zero Highways policy, published in 2021, targets a net zero future for the UK’s road network, including plans to launch a zero-carbon construction innovation programme focusing on asphalt, cement, concrete and steel. Now policy is translating into change, as research projects, government owned companies, and businesses push for road infrastructure emission reductions.
The road to greener roads forks in more than one direction. Most routes lead to alternative mixes of asphalt, often with biomass feedstocks.
In December last year, Tarmac, a major UK construction firm, carried out the first trial road resurfacing scheme in the UK to utilise a ‘carbon sink’ binder that reduces carbon emissions, resulting in what the firm claims to have been significant carbon savings.
The binder locks carbon into the road surface and prevents its release into the atmosphere, which limits emissions from construction. The scheme was a collaboration between Tarmac and National Highways, the UK highway planning agency, while Shell produced the carbon sink binder.
Use of the binder and other low-carbon interventions reduced overall emissions of the project by 75pc, according to Tarmac. The scheme also utilised recycled asphalt, reducing the need for newly produced bitumen.
Biogenic asphalts are becoming more widespread, says the Asphalt Industry Alliance (AIA). A ‘biogenic asphalt’ trial on the A452 road project resulted in CO2 ewas laid for the project.
Recent scientific research is pushing asphalt further. Researchers have developed a [‘self-healing’ asphalt] that mends its own cracks without the need for maintenance.
The new material could offer a solution to the UK’s pothole problem, says Swansea University, who have spearheaded the research alongside colleagues at King’s College London and the University of Biobio in Chile.
Pothole maintenance is estimated to cost England and Wales £143.5million a year, according to the AIA. The size of the issue means that potholes rank highly among the many collective annoyances of the British public, and the news of potentially self-maintaining potholes led to a rare flooding of national press outlets with asphalt news stories.
The path to net zero roads is moving past small trials and shifting to larger projects. On 4 February, National Highways revealed a target to reduce its construction emissions by 70pc for its Lower Thames Crossing project. National Highways aims to reduce emissions from the project to below 840,000t. If successful, the stretch of road would be the greenest road ever built in the UK, according to National Highways.
In an upscaled project, bitumen is only part of solution. National Highways’ target accounts for all materials and processes in constructing the road, and not only emissions from road paving. This includes fuels used on the construction site. National Highways aims to remove all diesel from its construction sites by 2027, instead using EVs and hydrogen powered heavy machinery.
The UK government is further encouraging firms to innovate new low emission road paving solutions through the ‘Live Labs’ scheme, managed by the Association of Directors of Environment, Economy, Planning and Transport (ADEPT). Live Labs 2 provided £30m in grants to firms willing to innovate new ways to decarbonise local highway infrastructure. This followed an earlier scheme running from 2019.
The scheme supports exploring multiple angles to find net zero solutions. As part of Live Labs 2, a trial in southwest England used a combination of an asphalt mix laid at a lower temperature than traditional asphalt and equipment fuelled by hydrogen and vegetable oil to drop emissions. All interventions collectively reduced emissions by 16pc, according to ADEPT.
A new Live Labs trial begins in early 2025 called Greenprint, which aims to create carbon-negative road infrastructure by generating energy collecting cuttings from road verges for use in biomass.
For all the projects and innovation happening in the UK bitumen and road industries, it is clear that truly decarbonising what is currently a heavy hydrocarbon product is a challenge. Most ideas remain at a trial stage, but with major projects showing the signs of significant carbon reductions, change is afoot in UK construction.
Author: Tim van Gardingen, Market Reporter, Oil Products
Related products
Spotlight content
