Palmgren, F., Berkowicz, R., Ketzel, M., Winther, M., 2007, NERI Technical Report No. 620, 44 pp.
Summary and conclusions
The project assesses SCR catalysts as an efficient tool to obtain compliance with the EU limit value for NO2. It is expected that <st1:country-region w:st="on"><st1:place w:st="on">Denmark</st1:place></st1:country-region> and the other EU member states are not able to comply with the limit value at 40 µg/m3 (annual average) in 2010 without further measures (EU, 2006).
Within the recent years we have observed an increase of the NO2 concentrations at busy streets. Several years of measurements from the monitoring programmes have been analysed. They support the assumption that the increasing NO2 concentration is due to higher direct NO2 emissions from traffic, probably caused by increasing number of modern diesel vehicles equipped with oxidizing catalysts or particle filters. We observed an increase of the direct NO2 contribution from around 5 % in 1995 to 18 % in 2006 during daytime on weekdays. During weekend nights we observed up to 40 %, when the traffic is dominated by taxies, which generally are new diesel cars with oxidizing catalysts.
The fraction of NO2 formed by oxidation of NO by O3 is nearly constant. This is because O3, which up till now has been the limiting parameter, has been constant for many years.
In addition, we have made scenario calculations of the effect of several different measures. The scenarios are the following:
0. Basis scenarios for 2005, 2010, 2015 and 2020 without further measures.
1. A scenario for 2010 corresponding to the environmental zone proposal in <st1:City w:st="on"><st1:place w:st="on">Copenhagen</st1:place></st1:City> . <st1:place w:st="on">I.</st1:place> e. particle filters are mandatory for heavy duty vehicles (> 3.5 tons), which have EURO 3 engines or older in 2010 (MZ1).
2. The environmental zone proposal (MZ1) as above, but with the assumption that 50 % of the oldest heavy duty vehicles will be replaced by new (EURO 5) (MZ2).
3. The environmental zone proposal (MZ1) as above, but with SCR catalysts on all vehicles, which got filters retrofitted (MZ1+SCR).
4. Replacement of pre-EURO petrol passenger cars (scrapping) with EURO 5 petrol passenger cars in 2010.
5. All diesel vehicles will be equipped with SCR catalysts in 2010.
6. A combination of 3. and 4. in 2010 and SCR catalysts on buses.
7. A combination of 3. and 4. in 2015 and SCR catalysts on buses.
We have made all scenario calculations for 138 busy street sections in the Capital area (the municipalities of <st1:City w:st="on">Copenhagen</st1:City> and <st1:City w:st="on"><st1:place w:st="on">Frederiksberg</st1:place></st1:City> ). The calculations for 2005, 2010, 2015 and 2020 showed that the NO2 concentrations will increase until 2010 assuming no other measures than already approved. Consequently, <st1:country-region w:st="on"><st1:place w:st="on">Denmark</st1:place></st1:country-region> will not be able to comply with the limit value at 40 µg/m3 at much trafficked street sections. Exceedance of the limit value will take place at 115 of the 138 street sections. The limit value will also be exceeded at some street sections until 2020.
MZ1: Implementation of the environmental zone proposal will result in exceedances at more street sections, if particle filters are retrofitted on heavy duty vehicles without any further technological measures for reduction of the NO2 emission. This will lead to exceedances at 129 of the 138 street sections.
MZ2: The number of streets sections with exceedances will be reduced to 120, if a fraction of the heavy duty vehicles (50 %), which should have particle filters are replaced by new vehicles (EURO 5).
MZ1+SCR: Retrofitting of SCR catalysts in the MZ1 scenario will reduce the number of street section with exceedances significantly to 101.
Scrapping of all EURO 1 and older petrol passenger cars and replacement with EURO 5 cars will lead to 105 street section with exceedances.
The number of street sections with exceedances will be reduced to 67, if all diesel vehicles were equipped with SCR catalysts. This is probably not realistic from a technological and economic point of view.
The combination of scrapping of old petrol passenger cars and SCR catalysts on all diesel vehicles which got particle filter lead to 55 and 58 street sections with exceedances in 2010 and 2015, respectively.
In conclusion, none of tested scenarios did result in compliance with the limit value at 40 µg/m3 in 2010. It was assumed that the traffic was constant until 2020, which probably is an underestimation since we already can observe a general increase. However, the increase will probably not take place in the very densely trafficked streets where the exceedances take place, but more in the newer and larger roads (by-pass roads, highways etc.)
In addition, it has been assumed, that the fraction of diesel passenger cars will rise until 25 %. This is probably an underestimation, since we already have seen a trend to a larger fraction. Estimates up to 60-70 % have been made, but it will depend on many factors like taxes on fuel and vehicles.
Finally, it has been assumed that the fractions of direct NO2 emissions are correctly estimated. They are taken from the literature, but they will depend on the applied technologies. Until now there are only emission limits on NOx and not specifically on NO2 and this could be changed in the future.
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