Figure 2 (below), Depicts the structure of atmosphere below 50kms and the various radiations and emission of green house gases.
Water vapour(H2O), CO2, methane (CH4) and ozone (O3) are examples of important ‘greenhouse gases These gases and particles alter the concentration of atmospheric greenhouse gases and trigger formation of condensation trails (contrails); and may increase cirrus cloudiness—all of which contribute to climate change. In order to combat climate change, the developed countries and economies in transition reached an agreement, under the Kyoto Protocol, to reduce their greenhouse gas emissions to about 5% below 1990 levels between 2008 and 2012. Aircraft emissions of oxides of nitrogen in the troposphere will act to increase ozone levels and therefore decrease surface UV radiation, whereas emissions in the stratosphere near 20 km, act in the opposite way.
Globally, contrails are estimated to cover 0.1% of the sky and this value is predicted to increase to 0.5% by 2050. If the contrails grow into cirrus clouds they have a greenhouse effect - they let solar radiation into the Earth's atmosphere but absorb infra-red radiation coming from the Earth. Soot and sulphate emissions may allow condensation of extra cirrus cloud and add to this effect.
RADIOACTIVE FORCING
The following diagram shows the different ways in which aviation contributes to radioactive forcing (as a measure for global warming). The scientific understanding of these impacts ranges from poor to good depending on the impact.
Estimates of the globally and annually averaged radioactive forcing (Wm-2) from subsonic aircraft emissions in 1992. Positive radioactive forcing is a measure for the contribution to global warming, negative forcing contributes to cooling. Source: IPCC Report on Aviation 1999.
Estimates of the globally and annually averaged radioactive forcing (Wm-2) from subsonic aircraft emissions for the year 2050. Estimations are based on the moderate IPCC growth scenario Fa1, assuming traffic growth of 3.1% per year and the growth rate of burned fuel to be 1.7% per year. Source: IPCC Report on Aviation 1999.
LOCAL POLLUTION
- DECREASED AIR QUALITY CAUSED BY AIRCRAFT AND ALSO BY THE ASSOCIATED GROUND TRANSPORTATION.
Large airports are heavy generators of air pollution because many aspects of their operations produce toxic emissions. These emissions come not only from the exhaust gases of the aircraft themselves, but also from at least three other major sources. First, there are the extensive supply and maintenance equipment and facilities that provide for the aircraft on the ground. Secondly, the large fuel depots with storage tanks, fuel lines and refueling facilities from which there is significant evaporation of volatile organic compounds (VOCs).Thirdly, the heavy road traffic generated by airports. The six main pollutants generated by airports are nitrogen oxides, volatile organic compounds (VOCs), ground-level ozone, particulate matter, carbon monoxide
and sulphur dioxide. All of these substances are damaging to human health. Vulnerable and a few minutes’ exposure to sulphur dioxide may trigger an attack. Sulphur dioxide is particularly dangerous if adsorbed by particulate matter. The particulate matter carries the sulphur dioxide deep into the lungs, causing serious health problems.
The impact of aircraft noise on residents near airports and under flight paths has been a source of concern over the last 20 years. Aircraft noise is a serious problem around all airports and under flight paths. Despite the introduction of quieter aircraft like Airbus 380, the evidence suggests that the number of people affected by aircraft noise is rising, due to the rapid growth in air traffic.High levels of noise give rise to a wide range of health problems and have a retarding effect on children’s learning ability. In the vicinity of airports, and on the flight paths in and out of airports, these ‘safe noise’ levels are regularly exceeded. Around Heathrow airport, for example, 440,000 people are exposed to noise levels above 55 dB(A), the maximum level recommended by the WHO for gardens, terraces and outdoor playgrounds. The standards that have been set by the WHO indicate the extent to which people’s health is currently being threatened by aircraft noise.
Other local environmental impacts:
While noise and air pollution are the most significant impacts from the operation of aircraft, there are also a number of other potential impacts arising from the siting and operation of airport infrastructure out of which few are:
• Land take – building an airport inevitably takes land away from its previous uses. In particular, it can affect wildlife habitats, landscape and heritage.
• Water pollution, particularly from de-icing aircraft, runways and other parts of the airport site
• Waste management, particularly waste generated inside terminal buildings.
RECOMMENDATIONS -The Options to Reduce Emissions and impact on Environment.
There is a range of options to reduce the impact of aviation emissions, including changes in aircraft and engine technology, fuel, operational practices, and regulatory and economic measures
1. Aircraft and Engine Technology Options
Subsonic aircraft being produced today are about 70% more fuel efficient per passenger-km than 40 years ago. The majority of this gain has been achieved through engine improvements
and the remainder from airframe design improvement. A 20% improvement in fuel efficiency is projected by 2015 and a 40 to 50% improvement by 2050 relative to aircraft produced today.
The 2050 scenarios developed for this report already incorporate these fuel efficiency gains when estimating fuel use and emissions.
Major examples include:
Pratt & Whitney has developed a jet turbofan engine that burns 12 to 15 percent less fuel than other jet engines and cuts carbon dioxide emissions by 1,500 tons per plane per year.
21st century aircraft A380, with a new wing design and composite materials accounting for 25% of its structural weight, the A380 is a much more efficient aircraft all round. And by producing only about 75g of CO2 per passenger kilometer, the A380 is contributing to the aviation industry's commitment to constraining greenhouse gas emissions.
2. Fuel Options
There would not appear to be any practical alternatives to kerosene-based fuels for commercial jet aircraft for the next several decades. Reducing sulfur content of kerosene will reduce SOx emissions and sulfate particle formation. Jet aircraft require fuel with a high energy density, especially for long-haul flights. Other fuel options, such as hydrogen, may be viable in the long term, but would require new aircraft designs and new infrastructure for supply. Hydrogen fuel
would eliminate emissions of carbon dioxide from aircraft, but would increase those of water vapour
3. Operational Options
Improvements in air traffic management (ATM) and other operational procedures could reduce aviation fuel burn by between 8 and 18%. The large majority (6 to 12%) of these reductions comes from ATM improvements which it is anticipated will be fully implemented in the next 20 years. All engine emissions will be reduced as a consequence. The rate of introduction of improved ATM will depend on the implementation of the essential institutional arrangements at an international level.
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4. Regulatory, Economic, and Other Options
Policy options to reduce emissions further include more stringent aircraft engine emissions regulations, removal of subsidies and incentives that have negative environmental consequences, market-based options such as environmental levies (charges and taxes) and emissions trading, voluntary agreements, research programmes, and substitution of aviation by rail and coach. Most of these options would lead to increased airline costs and fares. Some of these approaches have not been fully investigated or tested in aviation and their outcomes are uncertain.
5. Technology, Operations and Policy
The nation should vigorously pursue a balanced approach towards the development
of operational, technological and policy options to reduce the unfavorable
impacts of aviation. (The bottom figure depicts UK’s vision for aviation and environment)
Source:
Environmental issues in aviation industry Coventry University
CONCLUSION
The aviation industry is causing serious environmental damage, and is threatening the health of people who live and work near airports. If aviation is allowed to grow unchecked, the scale of the damage will escalate dramatically. This is of particular concern in relation to aviation’s contribution to climate change. These concerns point to the need for a fundamental change in public policy towards the aviation industry.
A solution to the environmental problems of aviation – particularly those concerning the climate – requires further research. This, should not stop from implementing the measures that are already feasible as soon as possible. In the short term, financial incentive is the only method that will create quick results. Technological breakthroughs and implementation, improved fuels and more
effective air traffic control, as well as”ecodriving” must also be introduced as they become available. Under no circumstances should the aviation industry resort to the tactic of “waitandsee”.
Aviation developments have long been about energy efficiency. Now that climate impact provides a new impetus, this striving for energy efficiency has laid a good foundation for future progress. Technologies enabling lower weight and less air resistance as well as more efficient engines all interact to reach ACARE’s (Advisory Council for Aeronautics Research in Europe ) goals of halving fuel consumption by 2020. More efficient design of the fuselage wings, engines with higher pressure and flow, can still represent continuous improvement. However, the growing impetus for change will lead to a higher innovation pace in the aviation industry than we have seen over the last few decades. Further adaptations for lower environmental impact will take place through adapted design and usage.
The aviation industry – both airlines and manufacturers – must collaborate to further the evolution towards better energy efficiency and lower emissions that has been going on for decades and that doubtlessly still has great potential. Improvements should be made at the highest possible pace technology allows, considering the expectations of stricter demands in the future. However, the
industry cannot rely exclusively on technology solving the environmental problems, particularly global warming, but should also present the potential of technological improvements without exaggeration, while, at the same time, implement other solutions to the problems.
In short, measures should be taken to reduce and control more stringent noise and emission standards for aircraft and for geographical areas around airports also better environmental monitoring and local environmental data around airports, to inform local populations about air and noise quality. Also, more research and best-practice guidance on using alternatives to the air journey.
REFRENCES
1. Journal of Air Transportation World Wide, Steven E. Morrissette
A Survey of Environmental Issues in the Civilian Aviation Industry (Vol. 1, No. 1 – 1996)
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3. IPCC SPECIAL REPORT, AVIATION AND THE GLOBAL ATMOSPHERE
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8. Calculating the Environmental Impact of Aviation Emissions, Dr Christian N. Jardine
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12. Conclusions and recommendations from the aviation environmental committee,
Prof. Lars B Johansson, Autumn 2007 http://www.lfv.se/upload/In_english/information_about/Summary%20Conclusions%20and%20Recommendations.pdf
13. The Plane Truth: Aviation and the Environment, Prof. John White egg and Nick Williams
14. www.enviro.aero
