Sustainable development is one of the greatest challenges and opportunities facing the aviation industry in the 21st Century. With global air traffic growing at an average rate per annum of 4-5%, environmental concerns are gaining an increasing importance. Although the aerospace industry has already made significant efforts to reduce its environmental footprint, further technological and operational improvements are necessary to outweigh the impact of traffic growth.
Noise
The principle sources of aircraft noise are the aircraft’s engines and, particularly during approach, airframe noise when the aircraft’s flaps/slats are fully extended and the landing gear is deployed. Aircraft noise levels are today typically around 20 dB lower than they were 40 years ago. This represents a significant reduction in the acoustic energy at source and consequently, for an individual event, the noise level perceived by the listener. However, over this period the number of air traffic movements has significantly increased, and will continue to grow. As a result aircraft noise continues to have a very significant environmental impact around airports and be a source of disturbance to the public.
The majority of European airports already have their operations constrained by noise-related issues. Many airports have implemented noise related charging schemes, night time restrictions or even night curfews. The number of airports affected in this way will likely increase further during the next decade.
Local Air Quality
Air pollutants such as Nitrogen Oxides (NO2 and NO) and particulate matter (PM) ;have been identified as key contributors from air transport to the problems of local air quality. Exposure to particulate matter can lead to impacts ranging from minor effects on the respiratory system to premature mortality. At some of the busiest European airports, NO2 levels may already exceed the annual limit set by Directive 2008/50/EC on ambient air quality. Compliance with PM limits will also become an increasing issue. It is therefore likely that air quality will be a significant feature in the debate concerning additional runway capacity. European airports e.g. in Switzerland, Sweden and the UK already apply airport emissions charging schemes and the EU air quality directives may result in the introduction of more local air quality management schemes and emissions related charging regimes in the future.
Greenhouse Gas Emissions
The main greenhouse gas (GHG) emissions generated by air transport are carbon dioxide (CO2), nitrogen oxides (NOX), water vapour (H2O) and particulate matter (PM). Many of the world’s governments, including those of the EU, are actively working through the United Nations Framework Convention on Climate Change (UNFCC) and the International Civil Aviation Organisation (ICAO) to mitigate the contribution of aviation to climate change. Although international aviation is currently excluded from the Kyoto Protocol, its contribution to global warming is predicted to increase significantly by 2050 due to growth in the industry and the development of alternate energy efficient technologies in other sectors.
It is recognised that international aviation, like all other sectors, should be integrated into the global emissions reduction targets to ensure it contributes to reducing GHG emissions and does not undermine efforts to address climate change. The inclusion of aviation in the EU Emissions Trading Scheme (ETS) is a key step to meet this goal.
Alternative Fuels
Alternative fuels should become a major driver in reaching the objective of carbon-neutral growth for aviation. Drop-in biofuels have been successfully tested and are already in use on certain commercial routes. The industry is aiming at replacing 6% of current fossil fuel with biofuel by 2020. Beyond the complex issue of life cycle assessment, the major challenge will be to ensure that biofuels are supplied in a reliable and cost-effective manner to air operators.
Future Objectives
The ultimate aim for the industry must be sustainable development, where the environment is not sacrificed for growth and future generations will be able to continue to benefit from air travel. The aviation industry has already started to tackle this formidable task, but continued and imaginative effort is required to ensure the industry maximises the use of its “environmental capacity”.