Choice of method

Two methodological tiers for estimating emissions of CO2, CH4, and N2O from water-borne navigation are presented. Both tiers apply emission factors to fuel consumption activity data. The decision tree shown in Figure 3.5.1 helps in making a choice between the two tiers. Emissions are estimated separately for domestic and international water-borne navigation.

Tier 1

The Tier 1 method is the simplest and can be applied with either default values or country-specific information. The fuel consumption data and emission factors in the Tier 1 method are fuel-type-specific and should be applied to the corresponding activity data (e.g. gas/diesel oil used for navigation). The calculation is based on the amount of fuel combusted and on emission factors for CO2, CH4, and N2O. The calculation is shown in Equation 3.5.1 and emission factors are provided in Table 3.5.2 and Table 3.5.3

Equation 3.5.1 Water-borne navigation equation

Emissions = ^ (Fuel Consumedab • Emission Factorab)


a = fuel type (diesel, gasoline, LPG, bunker, etc.)

b = water-borne navigation type (i.e., ship or boat, and possibly engine type.) (Only at Tier 2 is the fuel used differentiated by type of vessel so b can be ignored at Tier 1)

Tier 2

The Tier 2 method also uses fuel consumption by fuel type, but requires country-specific emission factors with greater specificity in the classification of modes (e.g. ocean-going ships and boats), fuel type (e.g. fuel oil), and even engine type (e.g. diesel) (Equation 3.5.1). In applying Tier 2, the inventory compilers should note that the EMEP/Corinair emission inventory guidebook (EEA, 2005) offers a detailed methodology for estimating ship emissions based on engine and ship type and ship movement data. The ship movement methodology can be used when detailed ship movement data and technical information on the ships are both available and can be used to differentiate emissions between domestic and international water-borne navigation.

Table 3.5.1 Source category structure

Source category


1 A 3 d Water-borne Navigation

Emissions from fuels used to propel water-borne vessels, including hovercraft and hydrofoils, but excluding fishing vessels. The international/domestic split should be determined on the basis of port of departure and port of arrival, and not by the flag or nationality of the ship.

1 A 3 d i International



(International bunkers)

Emissions from fuels used by vessels of all flags that are engaged in international water-borne navigation. The international navigation may take place at sea, on inland lakes and waterways and in coastal waters. Includes emissions from journeys that depart in one country and arrive in a different country. Exclude consumption by fishing vessels (see Other Sector - Fishing). Emissions from international military water-borne navigation can be included as a separate sub-category of international water-borne navigation provided that the same definitional distinction is applied and data are available to support the definition.

1 A 3 d ii Domestic



Emissions from fuels used by vessels of all flags that depart and arrive in the same country (exclude fishing, which should be reported under 1 A 4 c iii, and military, which should be reported under 1 A 5 b). Note that this may include journeys of considerable length between two ports in a country (e.g. San Francisco to Honolulu).

1 A 4 c iii Fishing (mobile combustion)

Emissions from fuels combusted for inland, coastal and deep-sea fishing. Fishing should cover vessels of all flags that have refuelled in the country (include international fishing).

1 A 5 b Mobile (water-borne navigation component)

All remaining water-borne mobile emissions from fuel combustion that are not specified elsewhere. Includes military water-borne navigation military emissions from fuel delivered to the country's military not otherwise included separately in 1 A3 d i as well as fuel delivered within that country but used by the militaries of external countries that are not engaged in multilateral operations.

Multilateral operations (waterborne navigation component)

Emissions from fuels used for water-borne navigation in multilateral operations pursuant to the Charter of the United Nations. Include emissions from fuel delivered to the military in the country and delivered to the military of other countries.

Figure 3.5.1 Decision tree for emissions from water-borne navigation

Figure 3.5.1 Decision tree for emissions from water-borne navigation

Box 3

Note: See Volume 1 Chapter 4, "Methodological Choice and Key Categories" (noting section 4.1.2 on limited resources) for discussion of key categories and use of decision trees.

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