Environmental performance analysis of railway infrastructure using life cycle assessment: Selecting pavement projects based on global warming potential impacts

Abstract

In response to the growing demand for credit to finance railway projects, portfolios of credit options which use criteria aligned with environmental factors have proved to be an attractive solution. The parameters involve, for example, the commitment to reduce the impact on global warming. Although transportation financing already includes environmental covenants, which are focused mainly on operational aspects, such as rolling stocks, this mechanism is still not applied comprehensively in railway infrastructure projects, particularly regarding the track and its foundation. Therefore, this study aims to present a comprehensive life cycle assessment method to analyze railway infrastructure projects' global warming potential impact, through environmental performance analysis. It was accomplished through the use of various materials for the composition of the sub-ballast, considering the subgrade's mechanical behavior under distinct moisture content conditions (optimal and optimal+2%). Compared with references values from the literature review (13.40–22.37 tCO2e/km/year), the results indicate that the sub-ballast without the use of alternative materials, specifically 19.88 tCO2eq/km/year, is the best choice. This considering a minor potential global warming impact when the moisture content is optimal, even considering differences in maintenance frequency during the assessed period, which is 200 years. Regarding the subgrade with moisture content above the optimal level, the use of a soil–cement mixture to increase the sub-ballast's support capacity, representing 4,481 tCO2eq, is the best choice when life cycle assessment aspects are considered. Finally, materials originating from bitumen demonstrate the highest potential global warming effects, been hot mix asphalt the option that shows the higher contribution– 48.69 tCO2eq/km/year. However, it is worth mentioning this last engineering solution is used to make the subgrade impermeable, which could be an interesting choice in situations in which the moisture content level is higher than that used in this study. • Comparative LCA for various sub-ballast is performed (construction & maintenance). • Sensibility assessed varying materials and subgrade moisture content, based on GWP. • For optimal moisture content, gravel soil without improvements performed better. • Under non-optimal moisture content, soil-cement seems to be the best choice. • For floods, HMA could be a feasible solution since it impermeabilizes the subgrade.