If sustainable biofuels do not become as widely available as expected, oil demand could remain stable over the next few decades, with any gains in efficiency simply offsetting the growth in traffic. Technological developments, operations and infrastructure improvements can create additional increases in fuel efficiency, as well as a reduction in CO2 emissions.
In the EU, direct greenhouse gas emissions from the aviation sector equate to approximately 3% of the total GHG emissions. Between 1990 and 2003, the EU’s GHG emissions from international aviation increased by 73%. As part of its Carbon Neutral Growth initiative, the International Air Transport Association (IATA) issued a four pillar strategy aimed at improving technology, operations, infrastructure and economic measures. In June 2009, IATA adopted a 50% CO2 reduction target per seat or tonne-kilometre by 2050 (compared to 2005 levels). This can be achieved primarily through improvements in new aircraft technology and, to a lesser extent, by aircraft operation improvements and the blending of biofuels.
TECHNICAL CONSTRAINTS LIMIT THE USE OF ALTERNATIVE FUELS FOR AVIATION
Since the 1960s, aircraft efficiency has actually been improving, meaning that the growth in GHG emitted by the sector is the result of an increase in demand, or traffic. That being said, replacing old aircraft with more efficient, new models, via fleet renewals and retrofits, alone could lead to a 25-35% reduction in CO2 per seat or tonne-kilometre by 2020. On a lifetime basis cost assessment, implementing such energy efficiency measures could create low - or even negative - CO2 abatement costs.
However, it is important to note that not all alternative fuels qualify for use in the aviation sector. Aviation fuels must deliver a very high level of energy, be thermally stable and avoid freezing and gelling at low temperatures. The use of liquid blending components, such as Hydro-treated Vegetable Oil (HVO) and Biomass-to-Liquids (BTL), is clearly limited. Viable fuel substitutions must meet numerous stringent product quality specifications while remaining competitive in the fuel market.
More efficient aircraft operations, improved operational practices like reduced APU (auxiliary power unit) usage, more efficient flight procedures and weight reduction will all certainly help prevent the release of millions of tonnes of CO2 into the atmosphere. The implementation of more efficient Airport Traffic Management (ATM) and airport infrastructure could provide additional reductions. Measures currently being taken include the implementation of the Single European Sky (SESAR), which will produce a 70% cut in route extension. As of 2012, the EU aviation sector is included in the Emission Trading System (ETS).
In summary, in the coming decades air transport will certainly become more efficient and more environmentally friendly. However, due to the sector’s very specific and technical requirements, liquid hydrocarbons are likely to continue to fuel the aviation sector.