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QUESTION: Why are we are required to submit our personal vehicles for a smog check and all those big trucks are out there belching out copious amounts of obviously harmful black smoke and soot?

Kathleen

ANSWER: The cynical short answer: They have a powerful lobby and their contributions to the economy are so significant. Almost everything we consume on this continent is moved by a truck at some point and, with fuel prices rising, the cost of this transportation is going up.

The more complete answer is also more complicated. Commercial vehicles are built to run for millions of kilometres and last for many years. Often the engines are rebuilt or replaced and the truck itself continues even longer.

Most of the newer vehicles on the road use much cleaner diesel engines and, in fact, the vast majority of big rigs run pretty clean.

If you see a cloud of black smoke pouring out of a big rig, it means the injection system is not running properly and needs a tune-up. It also indicates an excessive use of fuel and greater operating costs.

While there is no legislation I am aware of in place at this moment, new U.S. Environmental Protection Agency standards will go into effect in 2010 for Class 8 heavy-duty trucks that will address the problem. Combined with the legislated availability of clean diesel fuel (less than 15 parts per million of sulphur compared to 500 ppm), this will result in a much different landscape for commercial vehicles.

While new vehicles will be required to meet the new regs, the new clean fuel means older rigs can as well, thanks to a process know as selective catalytic reduction (SCR). Basically, this is the same system that has recently been introduced by Mercedes-Benz, marketed as BlueTec.

SCR involves injecting a slight amount of a mixture of urea and water known as AdBlue into the exhaust stream at certain intervals. The heat converts this special mixture into ammonia which, through a catalytic chemical reaction, reduces nitrogen oxides to near-zero levels, breaking it into nitrogen and water - natural elements in the air we breath.

SCR is not new; it has been used for decades in marine and large stationary diesel engines and is already in use by more than a half-million trucks in Europe where the clean diesel fuel has been available for two years.

Mercedes has made arrangements for its AdBlue to be available at Esso and Exxon outlets. A similar liquid known as diesel exhaust fluid (DEF) will have to be kept in separate containers on commercial vehicles and will require a refill every second fuel fill-up or 3,000-to-6,000 kilometres, depending on weight and use.

Already hundreds of highway refuelling centres have DEF available for SCR-equipped rigs. Almost all of the heavy-duty engines in volume production today, which will continue to be sold after the new standards take effect in 2010, will utilize SCR.

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