Chemistry Reference
In-Depth Information
NOx
Commercial,
institutional and
households
14%
Industrial
processes
2%
Non-road
transport
7%
Agriculture
2%
Road transport
41%
Energy
production and
distribution
20%
Energy use in
industry
14%
Total = 10.4 million tonnes
Fig. 2 Sectoral emissions in the EU-27 in 2008 [
5
]
most regulated pollutants (including NO
x
) from road transport in the EU peaked in
the early 1990s [
6
]. NO
x
emissions from road vehicles decreased by 45% between
1990 and 2010, while the volumes of passenger transport (in passenger-km) and
freight transport (in tonne-km) increased by more than 40% and 80%, respectively
(see Fig.
3
). This effective decoupling of transport activity from NO
x
emissions
was achieved through the interplay between legislation and technology. Notably,
the mandatory use of the three-way catalytic converter (often referred to as a
“three-way catalyst” - TWC) in 1992 reduced emissions from petrol passenger
cars rapidly and substantially. With some delay, emission-reduction measures for
heavy-duty vehicles also became effective. These two vehicle categories together
contribute around 80-90% of all road transport NO
x
emissions. However, the
reduction in NO
x
emissions in Europe has slowed down in recent years due to
increasing numbers of diesel cars in the fleet. The emission characteristics of
diesel vehicles pose a challenge to any emission-reduction target, as will be
explained below.
