IPCC METHOD

9.1 Introduction

The emissions of the greenhouse gases CO2, CH4and N2O by the transport sector in the Netherlands

are calculated using two methodologies: a top-down approach based on fuel sales data and a bottom- up approach based on vehicle kilometres driven and specific fuel consumption per vehicle kilometre on Dutch territory. In this chapter the differences between both approaches are described in more detail.

Top-down approach based on fuel sold

As part of international policy efforts in the area of climate change, which are coordinated by the Intergovernmental Panel on Climate Change (IPCC), it is mandatory to conduct an annual greenhouse gas emission inventory. In order to prevent overlap of data between various countries, the IPCC recommends calculating greenhouse gas emissions based on fuel sales data [ref 8: Thoughton et al., 1997].

In the Netherlands, as in most other countries, fuel sales data are known at an aggregate level. For example, the total amount of fuel sold per fuel type (i.e. petrol, diesel, LPG) to road transport is reported annually by Statistics Netherlands. These aggregated sales data are used to calculate the greenhouse gas emissions by road transport top-down, as reported to the UNFCCC.. In the present report, the top-down method is referred to as the IPCC method.

NB According to the IPCC requirements the CO2emissions from biomass combustion are not included

in the national emission totals, but are reported separately as an information item (see table 1.28).

Bottom-up approach based on fuel used

The energy consumption and the accompanying greenhouse gas emissions from road transport can also be calculated in a “bottom-up” fashion. First, energy consumption and greenhouse gas emission factors per vehicle kilometre are derived for different vehicle types. Combining these specific fuel consumption and emission factors with data on vehicle kilometres driven results in the total amount of fuel used (per fuel type) and resulting greenhouse gas emissions on Dutch territory. In the Netherlands, this method has been used for a number of years in the emission inventory of mobile sources (see the remainder of this report). In the present report, this bottom-up method is referred to as the Dutch territory method, which is used for determining the actual and the NEC emissions.

9.2

Why are there two estimation methods?

A decision was made to use both methods for greenhouse gas emissions in the Dutch emissions statistics. There are two reasons for this. First, the IPCC makes an inventory of worldwide greenhouse gas emissions. To prevent duplication of data and to minimize differences in calculation methods between countries, the IPCC has prescribed a method that uses national statistics about fuel sales in individual countries. The estimates for the total fuel sales to road transport are probably more reliable than the estimates of the total fuel consumption based on vehicle kilometres and fuel efficiency. Nevertheless, using this top-down method alone is not sufficient; for policy reasons it is also necessary to understand the greenhouse gas emissions of the individual vehicle categories of road transport. In order to aggregate the greenhouse gas emissions from road transport according to vehicle categories, the bottom up method is essential. Both methods must therefore be used.

The second reason is that it is advisable in any case to use both methods; this is because comparing the final results of the two independent calculation methods provides information about the reliability of the final greenhouse gas emission estimates for traffic and transport in the Netherlands. However, both methods are not directly comparable. Section 9.3 addresses this issue in more detail.

9.3

The most important differences between the two methods

The essential difference between the IPCC method and the Dutch territory method (based on energy consumption) is that the IPCC method is based on fuel sales in a single country and the Dutch territory method is based on fuel consumption on Dutch territory. There are other methodological differences

as well. These primarily concern the method of attributing emissions to the Netherlands. Crucially important to this process is an IPCC recommendation: “International bunker fuels are combusted in vessels at sea and by airplanes (both undertaking international movements) and therefore should be included in global greenhouse gas estimations. Following guidance, the IPCC recommends that every country estimate emissions from international bunker fuels sold within national boundaries, but that these emissions would be reported separately and, as far as possible, excluded from national totals”. This recommendation has been included in the IPCC method. In the Dutch territory method, the approach is different; this method aims to make an estimate of the emissions that take place on Dutch territory. This method does not address the issue of the difference between bunker fuels and non- bunker fuels, but only looks at what portion of the activities of air transport and maritime and inland shipping take place on Dutch territory.

For civil aviation, the Dutch territory method takes into account the emissions that take place during the LTO (landing and take off) cycle of all aircraft movements at Dutch airports (see Chapter 6). In the IPCC method, only the emissions from domestic overland flights and low-level flights are attributed to the Netherlands (both the LTO cycle and the remainder of these domestic flights). The emissions resulting from the combustion of bunker fuels that are sold on Dutch territory (free of excise tax) for international aviation are not attributed to the Netherlands in the IPCC method. The bunker emissions are reported to the IPCC, but not attributed to individual countries.

For inland shipping, the Dutch territory method includes the emissions of all activities that take place on Dutch inland waterways. In the IPCC method, only the emissions of domestic navigation on the inland waterways (with point of origin and destination both within the Netherlands) are attributed to the national emission totals. For maritime shipping, the Dutch territory method includes the emissions of vessels sailing on Dutch waters and those at anchor in Dutch harbours (see Chapter 4) as well as those on the Westerschelde27. The bunker fuels sold on Dutch territory (free of excise tax) must not be attributed to the Netherlands in accordance with the IPCC guidelines. However, the sales of bunker fuels to fishing vessels in the Netherlands must be added to the national total.

9.4

Emission factors for the IPCC method

Tables 9.1A, B and Cprovide a summary of the emission factors and conversion factors that have been used in calculating the greenhouse gas emissions of mobile sources in accordance with the IPCC guidelines. For further information, please refer to www.broeikasgassen.nl and the website of the Dutch Emission Registration.Tables 9.2A, B and Cprovide the factors which have been applied in the calculation of the IPCC emissions by road transport. The CO2factors have been corrected for the

use of biofuels and the N2O and CH4 factors have been derived from the actual emissions and

calculated fuel consumption according to the ‘bottom-up’ approach (see 9.1).

10.

CHANGES WITH RESPECT TO PREVIOUS VERSIONS OF THE REPORT

The most important methodological changes in the last 6 years are reported in Table 10.1.

The most recentchanges concern the 2012 emission registration, which reports the emissions during the period 1990 – 2010.