Carbon footprinting of railway embankments and cuttings: assessing potential for carbon reduction and carbon offsetting to reach net zero

Abstract

There are two overarching aims of this thesis. First, to identify and categorise different geotechnical assets, specifically embankments and cuttings, across the UK mainline railway and quantify the Business As Usual (BAU) Carbon Footprint (embodied CO2e Carbon dioxide equivalent) of the materials and processes used by these geotechnical assets. The second aim is to assess the potential for emissions reduction and offset over the lifecycle of these assets to contribute towards Network Rail (NR) meeting its Net Zero Carbon by 2050 obligations under the Environment Act. NR’s goals for net zero over the coming decades are aligned with Science Based Targets to enable this journey to be within the 1.5◦C pathway set out in the Paris Agreement.
The academic literature review has identified gaps in data collection and a lack of consistent alignment of data to the current key guidance on carbon management, Publicly Available Specification 2080 (PAS2080), life cycle stages. To fill this gap a novel carbon data capture form has been created which is subsequently utilised in the collation of data for 50 small scale case studies over the GB mainline railway. These case studies encompass maintenance, refurbishment and renewal interventions in embankments, soil cuttings, and rock cuttings.
Data collected using this novel form has been utilised to create carbon footprints of the BAU scenario for these interventions via the Rail Safety Standards Board (RSSB) Rail Carbon Tool (RCT) aligned with PAS2080 life cycle stages to enable identification of carbon hotspots by life cycle stage. An in-depth analysis of the A0 life cycle stage carbon emissions for mainline railway earthworks has also been carried out, assessing the relative weighting of emissions in this stage. The BAU scenarios have been expanded from the current limited A1-5 before use stages to include the B stages for in use, and C stages for EOL activities, initiating the journey towards whole Life Cycle Analysis (LCA) for these earthworks.
Using the identified carbon hotspots as a starting point for emissions reduction, a variety of emerging and established emissions reduction technologies have been reviewed and applied to the 50 case studies, demonstrating the potential for emissions reduction in the areas of transport, both of staff, and materials & plant, and construction, in terms of processes and materials. An overview of offsetting methods and their applicability on a project-by-project basis for the renewal case studies, followed by an extrapolation to the extensive NR estate, has been explored (including assessment of the co-benefits of offsetting such as biodiversity), determining that emissions reduction in conjunction with offsetting actions can aid NR in reaching Net Zero by 2050 with a theoretical 1/7 of their reduced whole company emissions able to be offset via Enhanced Weathering (EW).

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Identifiers

ORCID for Simon Blainey: orcid.org/0000-0003-4249-8110

ORCID for John Preston: orcid.org/0000-0002-6866-049X

ORCID for William Powrie: orcid.org/0000-0002-2271-0826

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