by Robin Futcher

From January 1st 2005, vehicles produced in Europe will have needed to meet even tighter emissions standards, namely Euro 4.
In order to meet the new standards, all heavy good vehicles need to reduce the amount of NOx (Nitrous Oxides) they emit.
Euro 5 is nearly upon us and is scheduled for introduction in October 2009. The new limits outlined in Euro 5 are even more stringent than before, in fact almost half of the previous standard.
Vehicle manufacturers are opting for SCR (Selective Catalytic Reduction) as the preferred technology to meet the demands set out by Euro 5. This involves incorporating the urea into an aqueous solution called AdBlue. The alternative is EGR (Exhaust Gas Recirculation) but this technology has its limits and at present will not be able to meet the demands of Euro 6 due in 2012
There are a number of advantages with SCR technology as around 85% of the nitrous oxide is converted into water vapour and nitrogen. (the air we all breath is approximately 74% nitrogen). In addition to this fuel savings of up to 6% have been boasted by some of the leading vehicle manufacturers. This has encouraged many of the leading manufacturers to concentrate their efforts on developing SCR vehicles in their range. With fuel pump prices now at a record high, support for SCR is growing fast.
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