Scenarios for future shipping emissions in the North Sea have been developed
in the framework of the Clean North Sea Shipping project. The effects of
changing NO
Shipping is an important contributor to air pollution in coastal areas. More
than 90 % of global trade is done with ships. The total global transport
work by ships (in ton miles) has been tripled since the mid-1980s
Nitrogen oxide emissions from ships are also regulated in MARPOL Annex VI.
Since the year 2000 the NO
In the Clean North Sea Shipping (CNSS) European project different
technologies capable of reducing air emissions from ships in the North Sea
were investigated. Among them are scrubbers that reduce sulfur emissions,
catalysts that reduce NO
The basis for the ship fleet and the ship movements on the North Sea is a
data set with AIS positions of ships for the entire year 2011 combined with a
ship characteristics data base that includes all ships given in the AIS data
set. The data are used to calculate the energy demand of individual ships
depending on the installed engine and their actual velocity. From this, fuel
use as well as NO
The purpose of scenarios is to describe plausible and possible future
developments. Scenarios are often used to describe the boundaries of possible
future situations, e.g. a worst case and a best case. In our study we decided
to create scenarios that describe the future development of policy and
technology regarding exhaust gas emissions from ships in the North Sea area.
We adopted the methodology described in
In brief, our fleet development scenario assumes an increase in the number of bigger ships, while the number of smaller ships decreases in the North Sea area. This leads to an increase in ship number by 1.0 % p.a. and an increase in transported cargo of 2.5 % p.a. In addition to this increase in ship number, it is assumed that per year 2.5 % of all ships are replaced by new ones, no matter what size they are. Older ships are replaced first. The main techniques under investigation are liquefied natural gas (LNG) as an alternative fuel for shipping and end-of-the-pipe technologies like scrubbers and selective catalytic reduction (SCR) to reduce sulfur dioxide and nitrogen oxide emissions.
The main drivers of changes in the use of ship fuels and in the amount of
emissions to air are on the one hand regulations, and here mainly what is
written in MARPOL Annex VI
Tier III NO
These drivers are combined into six scenarios that can be arranged in a
coordinate system with legislation on the
Scenario identifiers for technical developments and legislation with respect to ship emissions for 2030.
The stories behind these scenarios can be described as follows.
The emission inventories that were constructed as input for the CMAQ model
were developed from the ship emission inventory for 2011 which is based on
AIS data and ship characteristics data. First, the fleet development was
applied. Then, the new emissions were calculated by using modified emission
factors for the specific emissions of the ships. All emission factors are
given in g kWh
The LNG scenarios differ from the SCR scenarios in the following way: SO
The changes in the annual average emissions of NO
NO
SO
The CMAQ model
The model was set up on a
Left: modelling domains, outer domain with 72
The meteorological fields that drive the chemistry transport model were
simulated with the COSMO-CLM mesoscale meteorological model (version 4.8) for
the year 2008
COSMO-CLM is the climate version of the COSMO regional-scale meteorological
community model
Chemical boundary conditions for the outer model domain were taken from
monthly means of the TM5 global chemistry transport model system
The model runs were performed with full emissions from all relevant sources
in the model domain. Land-based emissions in hourly temporal resolution were
produced with SMOKE EU
The results for today's air pollution due to shipping serve as a reference
case for this study. They are discussed in detail in the accompanying paper
by
Contribution of shipping to the total NO
There are large differences between summer and winter. Partly, they can be
ascribed to seasonal differences in the emissions, with higher shipping
emissions in summer. Most of the differences in the concentrations are caused
by atmospheric chemistry. As a photochemical pollutant, ozone is only
increased during the summer months. The situation is similar for sulfate and
nitrate aerosol. Both are formed via oxidation pathways that include the
photochemically formed OH radical. Therefore, the conversion rate of SO
To derive the contribution of ships to the selected pollutant concentrations, two model runs, one including and one excluding shipping emissions, were performed. The difference is regarded as the contribution of ships to the individual pollutant. For the scenarios, the difference between two model runs with different shipping emissions is regarded as the change in the contribution of ships in the respective scenario. The evaluation is restricted to concentrations in the lowest model level, because they are most relevant for the population.
We mainly discuss the consequences of changes in the NO
NO
In the following, maps illustrating changes in the contribution of shipping
to NO
Time series of daily average NO
Scenario No ECA reflects a steady increase in shipping activity disregarding
the implementation of stricter rules for NO
Figure
Scenario ECA SCR 16 on average still shows a moderate increase in the NO
The contribution of shipping to NO
All reductions in the contribution of shipping to NO
Figure
Contribution of shipping to the total NO
Nitrate aerosol (NO
Contribution of shipping to the mean O
In summer, the emission scenarios show very similar results for nitrate
aerosol and for NO
In winter, nitrate aerosol concentrations are only marginally affected by
shipping emissions. For this reason the results of the scenario runs do not
show reliable patterns of changes in NO
Time series of daily average ozone concentrations in
NO
Here, we look at the impact of shipping emissions on the daily mean ozone
values. Figure
Scenario ECA SCR 21 (Fig.
Figure
An analysis of the different regions reveals that the days with
concentrations higher than 120
Number of days with 8 h maximum ozone concentrations greater than
120
Sulfur dioxide (SO
Change in the contribution of shipping to the total (
In Fig.
Particulate matter with a diameter less than 2.5
Reductions in the contribution of shipping to PM
Contribution of shipping to the total PM
The time series for PM
This paper investigates the effects of different future developments of shipping emissions in the North Sea area on air quality in the North Sea region. The main differences between the scenarios for 2030 concern nitrogen oxide emissions. They could be significantly lowered by using exhaust gas cleaning techniques or alternative fuels like LNG. Additionally, international regulations for a mandatory reduction of nitrogen oxide emissions in the North and Baltic Sea areas are under debate in the International Maritime Organization. To avoid misinterpretations of the results, land-based emissions and meteorological conditions were the same in the scenario runs and in the base case.
It was found that the expected increase in ship traffic in the North Sea will
lead to enhanced levels of NO
Time series of daily average PM
The effect of emission reduction measures depends on the year of
implementation. If already in 2016 new ships needed to follow the new Tier
III rules for new buildings, the concentrations of NO
The situation is different for sulfur dioxide, sulfate aerosol particles and
also for PM
Our model study shows that all effects of shipping emissions on air quality
differ largely by region and season, depending on the pollutant in focus.
Gaseous primary pollutants like NO
Change in the contribution of shipping to the total SO
Change in the contribution of shipping to the total SO
Change in the contribution of shipping to the total NO
Change in the contribution of shipping to the total SO
Change in the contribution of shipping to the total SO
Time series of daily average NO
Time series of daily average O
Time series of daily average PM
This work has partly been funded by the European Regional Development Fund (ERDF) within Interreg IVB projects Clean North Sea Shipping (CNSS) and CNSS Improved Dissemination and Impact (CNSS-IDI). We thank our colleagues from CNSS for their valuable comments concerning the development of the emission scenarios.
US EPA is gratefully acknowledged for the use of CMAQ; we thank Twan van Noije (KNMI) for providing TM5 model data. The article processing charges for this open-access publication were covered by a Research Centre of the Helmholtz Association.Edited by: A. Richter