Legislation & Technology

In order to reduce air pollution, European legislation is setting tighter limits on emissions from Diesel Vehicles. Two of the main pollutants are Oxides of Nitrogen (NOx) and Particulate Matter (PM)

In 1990, the first of these Standards, Euro 0, came into effect with NOx limits of 14.4 and PM limits of 1.1, both measured in g/kwh. The 2001 Euro III standard reduced these limits to 5 and 0.1 respectively.

The Euro IV standard, implemented on 1st October 2006, cut PM by a further 80% to 0.02g/kwh and NOx to 3.5g/kwh. In 2009 Euro V standards become compulsory, with no further reduction in PM levels but a further decrease in NOx levels to 2g/kwh. This will mean that a single Euro 0 vehicle emits the same amount of PM as 55 (fifty five) Euro IVs.

These drastic reductions impose serious technological challenges for engine manufacturers, since reducing NOx in the combustion chamber increases particulates and vice versa.

Engine Manufacturers have, therefore, adopted two main technologies to cope with reductions of pollution levels.

The first is called Exhaust Gas Recirculation or EGR. This involves cooling a percentage of the exhaust gas and feeding it back into the combustion chamber to burn at a lower temperature, thus reducing NOx formation. The PM pollutants are then reduced in the exhaust system via a particulate filter.  Although this system requires no additive, limitations on chassis space mean that larger engines cannot use the system. Due also to the burning of carbon-rich exhaust gases, oil drain intervals will be shorter.

The second technology is an after-treatment system called Selective Catalytic Reduction or SCR. In this system the PM emissions are controlled within the combustion chamber and NOx is reduced in the exhaust gases by using a reagent called AdBlue. This is injected directly into the exhaust gas and, via a chemical reaction in a Catalyst, converts pollutants such as NOx into environmentally friendly Nitrogen and Water. The advantage of this system is that it offers fuel economy benefits and can be adapted to cope with Euro V emission levels very easily. The AdBlue is dosed typically at 4-5% by volume of the rate of diesel for Euro IV, and 5-6% for Euro V standards.

EU regulation