German motor titan Mercedes Benz says it will be the first to introduce European-style "AdBlue" clean diesel technology to US consumers. AdBlue involves fitting cars with a tank of special urine-like liquid, which is used to clean the exhaust emissions.

In a statement last week, the company said:

The diesel engine has proved an attractive alternative [for] the USA in times of increasing fuel prices and growing sensitivity to the issue of CO2 emissions. In the land of large minivans, pickups and SUVs, and the given driving conditions characterised by steady cruising speeds on the highways and enormous overland distances, the diesel is able to show its advantages particularly well.

At the same time, American legislation sets very strict emission standards for diesel-powered vehicles. This is why Mercedes-Benz introduced the E 320 BlueTEC with its in-house BlueTEC technology in America first, and is now including a variant of this BlueTEC technology with AdBlue injection in its cross-Atlantic range. This innovative drive technology enables these large and powerful SUVs to meet the limits imposed by the US ...

Diesel engines, especially turbocharged ones, are quite green in many ways compared to petrol jobs. They are economical of fuel, and hence can have low CO₂ emissions - which saves money on taxes as well as on buying fuel. For instance, even quite muscular turbodiesel 4x4s can escape London Mayor Ken Livingstone's swingeing new taxes against "gas guzzling Chelsea tractors", and the carbon-banded road taxes ease as well. The teeny, super-economical VW Polo BlueMotion turbodiesel is the lowest-CO₂ car registered in the UK at the moment, just qualifying for the new sub-100g/km zero road tax band.

But diesels do emit comparatively large amounts of nitrogen oxide, which is nasty. Many US states, led by California, are imposing tough new nitrogen-oxide standards on new vehicles, and even tougher regs are on the horizon in Europe. Hence several manufacturers have begun making diesels as clean as they can - usually using the word "blue" in the branding for some reason.

Thus there is BlueMotion, BlueTEC etc. Early models wearing these badges have used different measures including filters, catalysts, engine modifications and whatnot. This latest "AdBlue" move involves fitting a tank full of "aqueous urea solution" which is squirted into the "exhaust tract" in very small amounts. This converts the nitrous oxide into ammonia, which in turn gets broken down into harmless nitrogen and water in a following catalytic unit.

Presumably the more obvious choice of "Golden" as a colour to represent this technology was deemed unsuitable. Too blue, perhaps. AdBlue is already used on large buses and trucks in Europe.

As a prelude to showering the US consumer with blue-green goodness, Mercedes showed off its new BlueTEC ML320 sports-utility Chelsea tractor at the New York auto show a couple of days ago. Its 28-litre tank of golden AdBlue is enough to go 28000km, seemingly, so Mercedes don't expect that customers will need to top it up themselves. This will be done by technicians during routine servicing.®

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