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Authorisation renewed every 5 years
The wood of sleepers is vulnerable to attack by bacteria, fungi and other insects, as well as to climatic conditions. To protect them and increase their lifespan, SNCF Réseau, like most railway network managers, has been using creosote for over 100 years. The European Union wants to ban this biocidal product, which is produced by distilling coal. However, in the absence of an effective and authorised alternative, and under favourable socio-economic conditions, creosote benefits from a marketing authorisation that is renewed every five years.
36 alternative products screened
Most of the sleepers are treated by impregnation of the substance at the SNCF Réseau Quercy Corrèze industrial site in Bretenoux (46). Since 2016, SNCF Réseau has been conducting an innovation project to find sustainable substitutes for creosote. No less than 36 alternative products or materials are or have been evaluated on their technical, toxicological and environmental performance, throughout the life cycle of the sleeper. "Our aim is to guarantee the continuity of supplies needed for network renovation and to anticipate the change in the Quercy Corrèze industrial plant that will be necessary if alternatives are validated", explains Vincent Auriat, head of the Sustainable Development Department at SNCF Réseau's Industrial and Engineering Directorate General (DGII) and head of the "Post-creosote" project. "We are conducting studies that are independent of the chemical industry, with the idea of being perfectly transparent to help the authorities make informed decisions."
15 experiments carried out on the way
In order to make progress in identifying alternatives to creosote, SNCF Réseau is relying on a start-up company in Belgium: Durwood. This company carries out laboratory tests, field tests and pre-industrialisation tests. "In particular, we have a chamber to simulate climatic conditions and their long-term effects on the ageing of wood, depending on the product used for the treatment", explains François Amorison, founder and director of Durwood. The research project is complemented by in situ experiments on fifteen SNCF Réseau sites. During track renewal work, new sleepers impregnated with the new solutions are laid alternately with creosote-treated sleepers. Samples are taken by Durwood and by a design office to check that the product is properly impregnated in the sleeper, and that it is harmless to the soil and therefore has no effect on the environment.
Imagining industrial transition scenarios
Of the 36 products initially evaluated, three were selected as the most promising for testing. If the European Union extends the authorisation for creosote - its decision is expected in the autumn of 2021 - SNCF Réseau will have a few more precious years to make the new solutions more reliable and achieve its industrial transformation. With this in mind, we are working closely with the teams from the Industrial and Engineering Department and Durwood", says Cédric Bouzou, Local Maintenance Manager at the Quercy Corrèze industrial site. "In particular, we are discussing the impregnation parameters that will enable us to industrialise the substitute products, as well as the forecasts for marketing authorisation. Our future installation will have to be flexible in order to be able to adapt to several products, which is an important change. "
Tomorrow's sleepers will be resources
With the introduction of the new impregnation products, sleepers can be reused after they have been used on the rail network. "With the growth of the circular economy, we will have the opportunity to capture new markets in France and Europe if we become the first industrial site to use alternative products. In addition, end-of-life sleepers that have not been treated with creosote can be used, for example, on tourist railways or to build street furniture", says Vincent Terrioux, Business Unit Manager at the Quercy Corrèze industrial site. "The end of creosote therefore appears to be a great opportunity to maintain our jobs while meeting health and environmental challenges." It is also worth noting that the company's approach enables it to preserve a supply - wood - which helps to capture CO2, while supporting the wood industry in the regions.