MnrAq

1
Inventories of CO 2 emissions from
international shipping 2007–2012
1.1 Top-down CO 2 inventory calculation method
1.1.1 Introduction
Section 1.1 provides a top-down estimate of emissions from shipping for the period 2007–2012. This task
also provides a comparison of this update with the methods used in the Second IMO GHG Study 2009. The
top-down approach is based on statistical data derived from fuel delivery reports to internationally registered
vessels. The top-down approach also considers allocation to domestic and international shipping, as reported
in national statistics.
Calculations of emissions using top-down fuel consumption estimates are presented. For CO 2 , these estimates
use CO 2 emissions factors consistent with those used in the bottom-up calculations in Section 1.2. Specifically,
the top-down inventory uses the CO 2 emissions factors reported in Section 2.2.7. For marine fuel oil (HFO),
this study uses 3.114 grams CO 2 per gram fuel; for marine gas oil (MDO), this study uses 3.206 grams CO 2 per
gram fuel; and for natural gas (LNG), this study uses 2.75 grams CO 2 per gram fuel.
1.1.2 Methods for review of IEA data
The World Energy Statistics published by IEA are used both in the Second IMO GHG Study 2009 and this
study. Both studies reviewed several years of IEA data, mainly as a quality assurance measure, but IEA statistics
provided the main top-down comparator with bottom-up results in that study.
The Second IMO GHG Study 2009 used IEA data for 1971–2005 (2007 edition). Two types of oil product
(fuel oil and gas/diesel) and three sectors (international marine bunkers, domestic navigation and fishing) were
reported, and the study subsequently projected those data for 2007 using tonne-miles transported.
For this study, the consortium reviewed data from IEA (2013) for all available years. Figure 18 shows the longrun
statistics for total marine consumption of energy products (international, domestic and fishing) over the
period 2007–2011. IEA statistics for international marine bunkers, domestic navigation and fishing data were
specifically examined for the fuels known to be most used by ships: fuel oil (residual), gas diesel oil, motor
gasoline, lubricants, non-specified fuel and natural gas fuel.
IEA statistics indicate that marine bunker consumption volumes of motor gasoline, lubricants, non-specified
fuel and natural gas are very small. Each of these features has less than 0.10% of fuel oil consumption as
international marine bunkers. Considering domestic and international marine fuels together, only motor
gasoline is reported at quantities equivalent to more than 1% of fuel oil used by ships. No natural gas is
reported as international marine bunkers consumption in IEA (2013), but a small quantity of natural gas is
reported for domestic navigation and fishing.
Other energy products are used in shipping, such as a small amount of primary solid biofuels (domestic and
fishing) and heat and electricity (exclusively in fishing). Given that the statistics identify none of these fuels as
used in international shipping, and given their very small volumes, these fuels were determined to be outside
the scope of this study. Comparison of top-down statistics is therefore limited to fuel oil (HFO), gas diesel oil
(MDO) and natural gas (LNG).