Trafikverket or Trafikverket’s contractors are considering the use of several products that in some way have to do with nanotechnology for sealing and impregnating various types of surfaces, for example road safety cameras. It has been noted that the potential health and environmental risks of nanomaterials should be evaluated over their entire life cycle. Further to previous risk assessments made on the nano-products considered by Trafikverket, it is therefore relevant to analyse the product’s impacts from a life cycle perspective.
The aims of this project are to (i) Provide a state-of-the-art background on the types, production processes, uses and current debates on the classification, and human and eco-toxicity of nano-silica and silane based nanofilms, (ii) To analyse if there are any arguments, from an environmental perspective, for the application of self-cleaning coatings to speed cameras compared to conventional practice, (iii) To qualitatively discuss the potential importance of nanoparticle emissions from self-cleaning coatings in the context of other sources of nanoparticle emissions.
A life cycle assessment is performed for maintenance of road safety cameras in Sweden in a business as usual (BAU) scenario and in a scenario where the cameras have been coated with a self-cleaning silane based nanofilm (Nano ProHard). The functional unit is the maintenance of road safety cameras in Sweden to allow for an acceptable speed camera picture quality over one year. The life cycle impact assessment methods ReCiPe Midpoint (Hierarchist) and Cumulative Energy Demand have been used. All life cycle phases from extraction of raw materials to end-of-life have been included. Inventory data is gathered from Ecoinvent 2.2. The detergent used in the business as usual scenario is approximated with the Ecoinvent process "Soap, at plant/RER S" and the alkoxysilanes in NanoProHard with "Tetrachlorosilane, at plant/GLO S".
Results show that the biggest impacts in the BAU-scenario are related to operation of vehicles for inspection of the road safety cameras in the maintenance phase, and to the production of soap. The biggest impacts in the Nano-scenario are related to operation of vehicles in the maintenance phase, and to production of soap, Nano ProHard Clean and Nano ProHard, mainly due to the ethanol in the product. Comparing the two scenarios (excluding operation of vehicles in the maintenance phase) it was seen that BAU had a bigger contribution than Nano in all impact categories except for fossil depletion, due to use of ethanol in the Nano-scenario. However, a sensitivity analysis revealed that this may not always be the case. It should also be noted that the toxicity in the use phase has not been assessed.
In cases where very little detergent is used for cleaning, for example in those cases where only water is used in the BAU-scenario, it may not be beneficial to use a nanofilm. However, in case the road safety cameras are usually washed very often, and/or with big amounts of detergent, use of nanofilm could have lower GHG-emissions than maintenance in BAU-scenario. However, it can again be emphasised that the toxicity of the products in the use phase has not been assessed, and that this is an aspect that must also be considered when concluding on which maintenance regime to choose. It must also be noted that soap is not the commonly used detergent in maintenance, and that results could vary significantly depending on detergent used.
It can be concluded that there are no clear environmental benefits if Trafikverket were to apply self-cleaning coatings to their road safety cameras, compared to conventional practice. The main source of impacts from maintenance of the road safety cameras is vehicle operation and this cannot be reduced by application of a nanofilm due to the current requirement of inspecting the cameras once per week. Considering the lack of knowledge on the product, and the possible toxicity of its components, it is not recommended that the product is used without further investigations into the type of chemicals used.
Stockholm: KTH Royal Institute of Technology, 2013. , 62 p.