Elsevier

Atmospheric Environment

Volume 45, Issue 39, December 2011, Pages 7036-7045
Atmospheric Environment

Carbon dioxide emissions from international air freight

https://doi.org/10.1016/j.atmosenv.2011.09.051Get rights and content

Abstract

Greenhouse gas emissions from international air transport were excluded from reduction targets under the Kyoto Protocol, partly because of difficulties with quantifying and apportioning such emissions. Although there has been a great deal of recent research into calculating emissions from aeroplane operations globally, publicly available emissions factors for air freight emissions are scarce. This paper presents a methodology to calculate the amount of fuel burnt and the resulting CO2 emissions from New Zealand’s internationally air freighted imports and exports in 2007. This methodology could be applied to other nations and/or regions. Using data on fuel uplift, air freight and air craft movements, and assumptions on mean passenger loadings and the mass of passengers and air freight, CO2 emissions factors of 0.82 kg CO2 per t-km and 0.69 kg CO2 per t-km for short-haul and long-haul journeys, respectively, were calculated. The total amount of fuel consumed for the international air transport of New Zealand’s imports and exports was calculated to be 0.21 Mt and 0.17 Mt respectively, with corresponding CO2 emissions of 0.67 Mt and 0.53 Mt.

Highlights

► Methodology to calculate CO2 emissions from international air freight is presented. ► Representative data on fuel uplifts were used in the calculations. ► EFs of 0.82 kg CO2 per t-km and 0.69 kg CO2 per t-km for short- and long-haul journeys. ► Total CO2 emissions from air freighting NZ’s 2007 imports and exports was 1.2 Mt. ► Emissions factors (EFs) derived are likely to be applicable to other nations.

Introduction

This paper presents a methodology for calculating international air freight CO2 emissions factors for a particular nation or region and the total CO2 emissions associated with the nation’s or region’s international air freight. New Zealand is used as a case-study in the present research for which emissions factors and total emissions are calculated, based on the 2007 calendar year. This case-study will be useful for other researchers and policy analysts performing similar studies at national or regional levels as well as helping guide New Zealand policy on international transport emissions.

Currently, there is no internationally accepted methodology for apportioning international aviation emissions (Wood et al., 2010). There is little peer-reviewed literature available for calculating the CO2 emissions from international air freight. A core issue surrounding the accurate quantification of international aviation emissions lies in the commercially-sensitive nature of accurate, activity-based data on fuel use by international aeroplanes. Agencies such as the UK Department for Environment, Food and Rural Affairs (DEFRA) have used other input data, such as specific fuel-oil consumption rates, to calculate CO2 emissions factors (Department of Environment, Food and Rural Affairs, 2008), which have subsequently been used in aviation emissions studies (e.g., Andersen et al., 2010, Saunders and Hayes, 2007). The alternative to activity-based quantification of aviation emissions is bunker fuel sales statistics, but these lead to discrepancies which were discussed in the global context by Owen et al. (2010), and in the New Zealand context by Smith and Rodger (2009).

The present research obtained commercially-sensitive fuel uplifts for aeroplanes refuelling in New Zealand to derive CO2 emissions factors for air freight. These were combined with a dataset containing all of New Zealand’s imports and exports transported by air freight to quantify the CO2 emissions associated with their international transport.

Due to the commercially-sensitive nature of the data needed, calculating air freight CO2 emissions factors as was done in the present research is rare. The international aviation sector is heavily reliant on aeroplanes built by only two manufacturers, who also produce the dominant air craft used to fly into and out of New Zealand. There is a high rotation of the global aeroplane fleet, meaning that the aeroplanes which service New Zealand also operate in other regions around the world. For these reasons, the emissions factors derived in the present research are likely to be applicable to other nations; however, more research is required to verify this. Comparisons with the few publicly available emissions factors for air freight are discussed.

The global aviation industry consumed approximately 200–250 Mt of kerosene per year in the mid-2000s (Kim et al., 2007, Nygren et al., 2009, Lee et al., 2010), resulting in the emission of 733 million tonnes (Mt) of CO2 in the year 2005 (Lee et al., 2009). This contribution represents approximately 3% of the total CO2 emissions from the combustion of fossil fuels and is slightly less than Germany’s national contribution in 2005, the 6th largest contribution by a country (International Energy Agency, 2010). Aviation accounted for 12% of the CO2 emissions from the global transport sector in the year 2000, the third largest contributor after road and maritime transport (Lee et al., 2009).

The contribution of the aviation sector to global radiative forcing takes into account historical emissions and, therefore, provides a more accurate representation of the sector’s contribution to anthropogenic climate change than considering CO2 emissions alone (Penner et al., 1999). In 2005, the radiative forcing due to aviation was estimated to be between 23 and 87 mW m−2 (excluding cirrus cloud enhancement, 90% likelihood range with a best estimate value of 55 mW m−2), equivalent to 1.3–10% (3.5% best estimate) of the total anthropogenic radiative forcing (Lee et al., 2010). This contribution is especially significant when considering that the sector has only been commercially active since about the 1950s, whereas some other CO2-producing sectors have been active for over one hundred years (e.g., the coal industry). While radiative forcing provides a more accurate representation of historical emissions, it is a difficult metric to use in estimating future impacts.

Under the Kyoto Protocol, Annex I countries are only liable for domestic aviation emissions that are included in a country’s National Greenhouse Gas Inventory, whilst international aviation emissions are only required to be reported (Eggleston et al., 2006). Under Article 2.2 of the Kyoto Protocol, Annex I parties “shall pursue limitation or reduction” of greenhouse gas emissions by working through the International Civil Aviation Organization (ICAO) (United Nations, 1998).

It is uncertain whether global climate change agreements will include international aviation emissions in the foreseeable future. The introduction of the aviation sector into the European Union Emissions Trading Scheme (EU ETS) in 2012 will be the first international policy measure to use binding targets that aim to reduce CO2 emissions from aviation (Anger and Köhler, 2010). Accurate quantification should always precede policy decisions, and it is in this regard that the present research will be informative.

Quantifying the non-CO2 climate effects that emissions have on radiative forcing is an area of active research (Sausen et al., 2005, Forster et al., 2006, Forster et al., 2007, Lee et al., 2009, Lee et al., 2010, Fuglestvedt et al., 2010, Wuebbles et al., 2010). Aviation emissions cause both positive and negative changes to radiative forcing in the atmosphere. There is currently no internationally standardised approach for accounting for the non-CO2 effects of aviation emissions. It is for this reason that no radiative forcing metric is applied to the calculations carried out in the present research.

Discussions on the regional- or product-level determination of CO2 emissions from aviation have increased in the literature recently, particularly as part of life-cycle assessments and the sector being introduced into the EU ETS in 2012. However, there are few peer-reviewed papers that calculate the CO2 emissions associated with a single country’s imports and/or exports from air freight, with Andersen et al. (2010) and Cadarso et al. (2010) being two rare examples. In both of those papers, the calculation of air freight emissions was not the focus of the paper and neither developed a unique air freight emissions factor. This highlights the need for more research to be done in developing emissions factors for air freight.

New Zealand is a geographically isolated island nation, and is therefore dependent on air and maritime transport for all international movement of people and goods. For the year ended June 2007, air freight accounted for only 0.56% and 0.45% of New Zealand’s imports and exports, respectively, by mass (Statistics New Zealand, 2007a). However, for the same year, air freight accounted for 21% and 15% of New Zealand’s imports and exports, respectively, by value (Statistics New Zealand, 2007a). This indicates that high value, low mass goods are traded internationally by air freight, with lower value, heavier items shipped by sea. Air freight is also the preferred mode of transport for time-sensitive goods (Sankaran, 2000).

Air freight can either be transported in dedicated freighters or in the lower holds of passenger aeroplanes (“belly-hold”, as it is referred to herein). New Zealand air freight is mostly transported in the belly-holds of scheduled passenger services (Ministry of Economic Development, 2005; Air New Zealand, pers. comm., 19 November 2010).

Section snippets

Overview

The present research utilises a general methodology of multiplying the mass-distance of commodities transported by international air freight by CO2 emissions factors. The authors are not aware of any other peer-review sources that outline how this methodology is specifically applied in a global, national or regional context. Previous air freight emissions factors that have been derived are found in non-peer reviewed sources. There are many inputs that are used in calculating both the

New Zealand aeroplane movements

The geographical location of New Zealand results in the average distance needed to fly between New Zealand and an overseas destination being considerably larger than for many other countries. As a result of this, of the top 20 countries or territories for imports and exports, only Australia, Fiji and the Cook Islands were short-haul international journeys. These countries combined accounted for 34% and 49% of the gross mass of air freight imports and exports, respectively, from the top 20

Conclusion

The climate impacts of international aviation due to the emissions of CO2 are currently not liable under any global agreements. An increase in research into the CO2 emissions from aviation in recent years has been due to interest in quantifying air transport’s climate impacts, as well as increased use of product life-cycle assessments and the impending addition of the aviation sector into the EU ETS. However, there is minimal peer-reviewed literature on air freight CO2 emissions factors and the

Acknowledgements

The authors acknowledge the Statistics New Zealand Student Assistance Scheme for providing HS10 data for the present research through a data scholarship awarded to M.A.C. The authors thank the Transport Research and Educational Trust for providing funding at an early stage in this research. The University of Otago Department of Physics 2009 Summer Research Bursary scheme, the Tertiary Education Commission and University of Otago 2010 Matched Funding Summer Scholarship scheme and the Otago

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