The environmental impact from the use of a truck is mainly generated from exhaust emissions. Emission levels are on the other hand related to fuel consumption, fuel quality, combustion techniques and cleaning techniques.
Combustion Technique
Compared with other engines, the diesel engine in our trucks is very energy efficient. During combustion, the temperature level is high and there is a surplus of air. The combustion is almost complete. The hydrocarbon and carbon monoxide levels in the exhaust gases are low compared with petrol (’otto’) engines.
On the other hand, a diesel engine produces more nitrogen oxides and particles than an otto engine. By monitoring combustion, the balance between hydrocarbons/carbon monoxide and nitrogen oxides can be regulated.
Fuel Quality
Diesel fuel has a higher energy value than petrol, but, on the other hand, it contains higher levels of sulphur and aromatic hydrocarbons. Currently, low-sulphur fuel can be found in e.g. Sweden, Finland and the United Kingdom.
Cleaning Techniques
There are currently several types of after-treatment or cleaning available for diesel engines.
- One type uses filters or particle traps, which reduce the quantity of particles discharged.
- The second type is a catalytic converter, which burns the exhaust gases in controlled conditions.
For their FL6 and FM9 Volvo offer an exhaust filter, which is a combination of an oxidising catalytic converter and a particle filter. The filter reduces hydrocarbons, carbon monoxide and particles by 80-90%. This cleaning technique requires low sulphur fuel, that is, diesel that contains no more than 50 ppm of sulphur.
The new engine technologies developed to meet the tough legislation are Exhaust Gas Recirculation (EGR) and Selective Catalytic Reduction (SCR).