On 17 December 2020, Lancashire County Council declared a climate change emergency and adopted an ambitious carbon reduction and nature recovery resolution that seeks to 'transition the Lancashire economy away from carbon by 2030 and address the biodiversity crisis'. They recognised that a planned highway capital surfacing programme was a highly carbon intensive programme of works, so began a journey to ascertain the carbon output, record and measure changes made to reduce it, and develop tools to allow them to integrate carbon usage into the asset lifecycle modelling.
- To work in collaboration through the highways sector to establish best practice in carbon modelling and to agree consistency and consensus across the sector (via the Midlands Highway Alliance Plus (MHA+) and Local Council Roads Innovation Group (LCRIG)) in how to measure and model carbon usage for highway works.
- To understand the CO2e of different products and processes.
- To inform the decision making process when it comes to choice of materials, treatments and intervention timing.
The above are with the overall aim to reduce CO2e of the highway surfacing programme both in the immediate term and whole life cycle.
We have engaged with highway authority benchmarking organisations MHA+ and LCRIG to start to develop modelling that will allow the impact of various carriageway treatment options on whole life CO2e. Substantial work has already been done by Herefordshire County Council in developing a spreadsheet based model for whole life carbon modelling. Further working is continuing through the MHA+ Asset Management Group to develop the model and provide consistency in the CO2e rates used in the model.
Through engagement with partner authorities and the supply chain, we identified three initial possible solutions for reduction of CO2e associated with our carriageway surfacing works:
- warm mix asphalt
- in-situ carriageway recycling
- ex-situ carriageway recycling.
Along with the physical processes, we also collaborated with other highway authorities and suppliers to ascertain the CO2e equivalence values for each process, including traditional hot mix asphalt and the new alternative treatments/materials. This allowed a baseline CO2e of the surfacing programme to be developed and subsequent values of CO2e when using the alternative treatments. This then allowed savings to be calculated.
We demonstrated an in-year 31 per cent CO2e saving over the use of conventional hot mix asphalt. Through working with our contractors and suppliers, we produced a mechanism to assess the CO2e impact of each scheme and so begun embedding the thought process of considering CO2e into our scheme and works design.
Through this journey to date, it is apparent that savings through the three main solutions we implemented will only get us so far in helping to achieve net zero. The technological fact at this point in time is that the assured properties of virgin aggregate and the properties of bitumen will still be required for road surfacing materials.
Therefore, it will still remain that the quarrying of material and distillation of bitumen will use carbon, this reinforces the mantra of sustainability through durability. The initial reduction of carbon usage must not come at the detriment of durability, as this will inevitably lead to increased carbon usage over the lifecycle and not contribute to net zero, in fact it would likely be detrimental to this target.
We are therefore progressing a parallel project to refine the design of road surfacing materials and to implement automated intelligent testing equipment with the aim of increasing durability.