Embodied greenhouse gas assessment of railway infrastructure: the case of Austria

Abstract

This study assesses life-cycle greenhouse gas (GHG) emissions associated with the entire railway infrastructure network of Austria, a first detailed study for a country, modelled through a top-down approach. Railway track is analysed for the first time in detail for a variety of specific boundary conditions using a bottom-up approach focusing on track renewal and maintenance. The methodology of standard elements allows for quantification of expected maintenance demands over the life cycle as well as determination of service life (SL). For this, the network is clustered into the main condition-affecting parameters, and documented maintenance and renewal measures are analysed and interpreted accordingly to estimate future behaviour. This Austrian approach used for assessing life-cycle costs serves as input for evaluating environmental impacts, a novel model. Data were gathered via environmental product declarations, governmental publications and company-specific environmental reports to correspond to the standard supply chains of the Austrian Federal Railways' (OBB) life-cycle (manufacturing, construction, maintenance and reuse/recycling) infrastructure practices, and reflect actual transport distances, transport modes, the Austrian electricity mix and emissions. The railway infrastructure causes 235 000 tonnes of CO(2)eq emissions per year (0.3% of Austria's total) based on the current infrastructure network, asset distribution and renewal rates. Within railway infrastructure, the track (including rails, fasteners, sleepers and ballast) is the main contributor to GHG emissions with 55% of the total. The GHG emissions associated with concrete tunnels are 16 times larger per kilometre per year than the railway track, but supply only 22% of the total emissions. The railway infrastructure contributes an additional 141% of GHG emissions over emissions from passenger traffic, which is much higher than previously anticipated. In-depth analysis of railway track shows that concrete sleepers with under-sleeper pads come with lower environmental impacts than conventional concrete sleepers. Higher traffic loads as well as narrow curves cause a significant increase in environmental impacts. For rails in a straight section with an SL of 50 years and two grinding measures, the costs regarding GHG emissions amount to (sic)6500 per kilometre (including the production, construction and use phases) when calculating with a cost of (sic)20 per tonne CO(2)eq on the market. Currently, this equals around 5% of the economic costs, but is expected to significantly increase as costs for environmental impacts are set to increase until 2050. Mitigation potential can be found in special rail steel production, reuse of materials, use of alternative fuels and efficient maintenance strategies.