This study is firstly a short review of the types of exhaust systems predicted for Euro 4 (2005) and Euro 5 (2008), particularly focussed on the effects of combined NOx (nitrogen oxides) and PM (particulate matter) aftertreatment systems. Secondly, it explores in detail the implications of using a liquid secondary water-based fuel of urea on board heavy duty diesel vehicles in Europe as a basis for NOx reduction via selective catalytic reduction (SCR). Some of the main points that become apparent when using integrated SCR systems are: the potential costs of increased urea production in Europe (including possible fuel taxation), refuelling issues, secondary fuel cost, logistics of urea supply, and cost of implementation of the urea fuel delivery method. From the original equipment manufacturers view, the hardware cost will be increased substantially when compared to current silencer systems. From the vehicle owner’s point of view, the possibility of large running cost increases is not desired, and the system solution cost and its benefits must ultimately be acceptable. This paper will attempt to put the life-time costs of various systems within perspective in order to assess the feasibility of implementing selective catalytic reduction systems (SCR) Europe wide for the near future
