Safety and sustainability analysis of railway sleeper alternatives : Application of a novel method for material loops

This is a revised version of letter report 2020-0126 Every year, ProRail replaces 200,000 railway sleepers. In the last century, wooden sleepers were used treated with creosotes to preserve them. Creosotes contain substances of very high concern. More recently, sleepers have been made from concrete, but greater quantities of CO2 are released in the manufacture of these sleepers than from wooden sleepers. To minimize CO2 emissions and the use of substances of concern, ProRail is looking for alternative railway sleepers. To this end, RIVM has compared six different types of sleepers with cement concrete (100 percent Portland cement). The six sleeper types are made from copper-treated wood, untreated wood, recycled steel-reinforced plastic (PE), virgin steel-reinforced plastic (PE), glass-fiber-reinforced plastic (virgin PU) and Sulphur-based concrete (instead of cement-based concrete). The comparison of the various sleepers was based on the aspects that are important for sustainability and safety of substances for the environment. The sleepers made from recycled plastic and Sulphur-concrete are more sustainable than sleepers from concrete (Portland cement). The other types of sleepers are only favorable over concrete in certain aspects of sustainability. Based on the data available, the various types appear to be equally safe for the environment. Part of the sustainability assessment of the sleepers is done by looking at the extent to which they release greenhouse gases and how much land is needed to extract the materials to make them. The land used to produce wooden sleepers is greater than for the other sleeper types. This is important due to the effect on biodiversity, even though less greenhouse gases are released during production compared to concrete. The safety of the sleepers was analyzed by looking at the presence of pollutants and the degree to which these pollutants leach out. After all, any substance released during the use of the sleepers can end up in the soil and groundwater. There is legislation for all types of sleepers, the objective of which is to ensure that they are safe to use. For this study not all relevant data were available. Knowledge of the presence of any hazardous substances in sleepers is important if they are to be safely reused.