Challenges for commercial civil air transport

because much more energy efficient end-use technologies are in use. Similarly, the amount of primary energy needed to fulfil those needs is only about 56 percent of what is needed today, mainly because half of the primary electricity produced from renewables is being transmitted directly to consumers without considerable losses. The other part of this electric production is converted into hydrogen that is being stored for later use and thereby incurring some energy losses. Furthermore, the use of renewable sources of energy has allowed for phasing out most uses of fossil fuels.

In the proposed energy system commercial civil air transport still remains one of the few users of fossil fuels, using about 12 percent of the final energy consumption in Europe and 6 percent of the primary consumption, which equals 91 percent of the total remaining fossil uses, excluding non-energy uses. Note that these figures are based on the assumption that the specific fuel intensity of the global aircraft fleet has been reduced by 50 percent as compared to today while Europeans are assumed to only travel three times as much by air as in 1990. Three times more passenger air travel in Europe in 2050 as compared to 1990 is a relatively low figure as compared to what is currently envisaged by the commercial civil air transport industry itself. The latest industry forecast suggests that global passenger air travel might triple already in 2020 as compared to 1999 [Airbus 1999]. If air traffic continues to grow at the current pace in Europe the sector might well consume at least three to five times as much jet fuel in 2050 as what is envisaged in the European scenario suggested here for 2050.

Thereby, commercial civil air transport may be using up to more than 50 percent of the total final energy use and up to around 30 percent of the total primary uses.

Figure 5.7: The two major challenges for reaching a sustainable commercial civil air transport system

5.2.1 Global air traffic growth versus environmental sustainability

A major challenge for developing a sustainable commercial civil air transport system is the current growth in passenger air travel and airfreight. Figure 5.8 exemplifies the challenges posed to the commercial civil air transport system by growth in passenger air travel. From 1960 to 1998 total passenger air travel, measured in RPKs, increased more than 20-fold from around 131 billions to around 2888 billions, corresponding around 45 RPKs per capita in 1960 and around 490 RPKs per capita in 1996, that is, an 11-fold increase per capita.

Figure 5.8: World passenger air travel 1970-1998 measured in revenue passenger kilometres performed and scenarios for future development Sources for global RPKs: 1960-1975: [Boeing 1980] and 1976-1998: [IATA 1994 and 1999]. Global population data are from [US Census Bureau 2000]. Industry air travel forecast to 2020 from [Airbus 1999].

Scenarios four and five in Figure 5.8 are based on a recent aerospace industry forecast predicting that the world’s RPKs will grow by 5 percent through the next two decades, thereby leading to a tripling of passenger air travel in 2020. The differences between scenarios four and five is that after 2020 growth is assumed to continue at 5 percent Air travel demand growth Technical and operational fixes ^versus

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and 4 percent until 2050 in scenarios five and four respectively, the period after 2020 being shown by dotted lines. In scenarios four and five world passenger air travel has grown nine-fold and twelve-fold in 2050 as compared to 1998. Scenario one illustrates that even if the average per capita passenger air travel in 1996 of around 490 RPKs is

“frozen”, the anticipated population growth would anyway lead to around 50 percent more passenger air travel. Scenarios two and three illustrate that passenger air travel volume would triple or six-double by 2050, if the average global per capita passenger air travel grows from 490 to 1000 or 2000 kilometres respectively. Even 2000 kilometres per capita, leading to a 6-fold increase in the global passenger air travel, is less than the amount of air travel in some industrialised countries today (e.g. the United States and Australia).

Currently, people living in industrialised countries perform the main share of the world’s passenger air travel and airfreight. As indicated in Figure 5.9, airlines situated in North America, Europe and the Asia-Pacific regions performed around 90 percent of the world’s revenue passenger kilometres (RPKs) in 1996. Therefore, on the longer term, the prospects for passenger air travel growth seem almost insatiable, if people living in developing countries begin flying more.

Figure 5.9: World air travel by geographical region 1975 and 1996 Sources: [ICAO 1986 and 1996a].

Before being able to suggest what may be adequate goals for the future level of air traffic volume in an environmentally sustainable commercial civil air transport system it

North America 39%

Asia and pacific 24%

Africa 2%

Middle East 3%

Europe 27%

Latin America/

Carribbean 5%

37%

2%

3%

12%

5%

41%

1996: 2570 billion RPKs

1975: 697 billion RPKs

will be necessary to evaluate to which extent the specific GHG emissions per passenger- and freight-tonne kilometre can be reduced in the future.

5.2.2 Technical and operational fixes versus growth

A major challenge for the commercial civil air transport system is to try to de-couple the growth in GHG emissions from the growth in air traffic volume by reducing the specific greenhouse gas emissions per passenger kilometre and per freight tonne kilometre performed. First of all, the specific GHG intensity per capacity unit of the aircraft fleet can be reduced by introducing more efficient new aircraft and by scrapping the oldest and most inefficient models. Secondly, improvements in operational procedures, such as improving average load factors and reducing stacking above airports can reduce the specific GHG intensity of the aircraft fleet. Finally, choosing fuel with lower GHG emissions per available energy unit than current fossil jet fuel can reduce emissions per distance travelled (see Figure 1.2). An example could be a switch from kerosene to liquid hydrogen fuelled aircraft.

As shown in Figure 5.10 the global aircraft fleet’s specific CO₂ emissions per passenger kilometre performed has been reduced substantially since the 1970s.

However, the fuel efficiency gains have been levelling off in the last decades as compared to earlier (see also Figure 3.3). The tendency for the fuel efficiency gains to slow down is expected to continue in the future. As an example, the European Aerospace Industry envisages that the yearly reductions in the European fleet’s specific CO2 emissions will not exceed 1,1 percent throughout the next decade [AEA and AECMA 1999].

Scenarios for the future specific CO₂ emissions of the world fleet until 2050 are illustrated in Figure 5.10. The scenarios are based on yearly reductions of the fuel intensity of 1,1 percent throughout the period in specific fuel scenario 1 (SFSc1); and starting at 2 percent and thereafter gradually levelling off to less than a half percent by the end of the period in specific fuel scenario 2 (SFSc2); and 2 percent throughout the period in specific fuel scenario 3 (SFSc3) respectively. The average fuel-burn per passenger kilometre is reduced by 43 percent in scenario one (SFSc1), by 46 percent in scenario two (SFSc2) and by 64 percent in scenario three (SFSc3). SFSc1 illustrates a business as usual development in Europe but is probably rather conservative if considering the global fleet. SFSc2 represents a more rapid introduction of new

advanced technology aircraft and improved operational procedures in line with what is anticipated by the IPCC in its central forecast for the global fleet for the next two decades. SFSc3 probably represents a minimum for what is technologically achievable concerning fuel intensity reduction.

Figure 5.10: Specific CO₂ emissions per revenue passenger kilometre (RPK) of the world civil passenger aircraft fleet and scenarios for the future

Source for historic specific fuel burn is chapter 3.

Figure 5.11 illustrates some scenarios for the world’s civil aircraft fleet’s future CO₂ emissions as compared to 1999. These scenarios combine the demand scenarios for passenger air travel that are illustrated in Figure 5.9 with the scenarios for the specific CO₂ emissions that are shown in Figure 5.10 and exemplifies the dominant role commercial civil air transport might possibly come to play in a future sustainable energy system. The thick curves in Figure 5.11 illustrate demand scenario five (DSc5) combined with specific CO2 scenarios one (SFSc1), two (SFSc2) and three (SFSc3).

This is meant to illustrate that if the air traffic volume grows by a factor of twelve, while the specific CO2 emissions are reduced by 43 percent, 46 percent and 64 percent respectively, the CO₂ emissions from the world’s civil aircraft fleet will grow by factors of 7.1, 6.8 and 4.5 respectively. Demand scenarios one (DSc1), two (DSc2), and four (DSc4) are only shown in combination with specific CO₂ emission scenario one (SFSc1). Demand scenario three (DSc3) is combined with scenarios one (SFSc1) and two (SFSc2) for specific CO₂ emissions. Among the scenarios shown here only the

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combination DSc1 * SFSc1 allows for reduced yearly CO2 emissions from commercial civil air transport in 2050 as compared to 1999. This is under the assumption that air traffic volume per capita is kept constant at the 1996 level, while the specific CO2

emissions are reduced by some 43 percent.

Figure 5.11: Scenarios for future CO₂ emissions from world civil aircraft fleet until 2050 (index 1999=1)