The global warming caused by greenhouse effect has become an important issue which humanity is facing. This issue is also the great challenges which humanity is facing in the 21st century. For a long time, scientists have always thought that carbon dioxide gas is the culprit which causes global warming. The carbon dioxide gas is produced by excessive burning of coal, oil and natural gas of a modern industrial society. However, the British Institute of the University of York Situo Ge Gilmore recently published a research report that the airline industry is another culprit of global warming (Xu Anjieï¼Œ2008). In recent years, various sectors began to pay attention to the effects of global warming caused by the aviation industry; Europe and the United States also intend to through legislation, emissions trading scheme (ETS) and other measures to reduce aircraft greenhouse gas emissions. In the "GreenerSkies2007 conference" held in Hong Kong, the representatives of a number of industry associations and airline have reservations about the above-mentioned measures, and call upon governments' civil aviation and air traffic control departments to further open the airspace and enhance aviation management (Yang Shuaiï¼Œ 2007). At present, the aviation industry accounts for only about 3% of total global anthropogenic carbon dioxide emissions, but with the development of global aviation industry, environmental pollution brought by the aviation industry is a serious problem, which must be strictly controlled.
2 The environmental pollution problems caused by the aviation industry
2.1 The aviation industry is one of the heavily polluted industries
Environmentalists pointed out: among the various modes of transportation, the regular route pollution of the environment is the most serious. At present, the aircraft's engines use efficient aviation gasoline and after the combustion there is basically no smoke, but they release large amounts of carbon dioxide gas and water vapor. The experts from U.S. Department of Transportation research institutions and others who are making use of computer models of the United States and Europe measure against emissions. The results showed that in 2000 the world's aircraft carbon dioxide emissions are 572 million tons; in 2010 it will increase to 605 million-776 million tons and in 2025 it will further increase to 1.228 billion-1.488 billion tons which is equivalent to the displacement of Japan 2006 (about 1.34 billion tons)(Energy Departmentï¼Œ 2004). As the aircraft is flying at high altitude, the impact on the atmosphere of its pollutants emissions is greater than pollutants emissions on the surface and also more easily causes greenhouse production and global climate changes. According to the research, aircraft emissions in the atmosphere each year is about 300 million tons of greenhouse gases which causes that the greenhouse effect is about three times of the ground-equivalent emissions. The statistics of "Friends of the Earth" organization in British also show that the carbon dioxide emissions of a jumbo jet of a trip from Europe and the United States are equivalent to annual emissions of a vehicle (Johnstone & Whiteheadï¼Œ 2007).
The human environment suffered heavy damage caused by the intensive and frequent flight routes of the global. For example, the 400 passengers in Australia Sydney International Airport who are boarding flight to London of England flying to London know that the flight needs 23 hours and to volley across the 10.5 thousand miles, but very few people will realize that in these 23 hours of flying time period passengers are required to eat 1 600 copies of the package plastic packaging, aircraft has to drink over 200 tons of aviation fuel and exhausts at least 500 tons of carbon dioxide emissions and other gases. Thus it will increase the atmosphere's "greenhouse effect". The United Nations Intergovernmental panel on Climate Change estimates that the amount of the carbon dioxide emissions caused by the aviation industry is accounting for 3.5% in worldwide, while in 2050 this proportion will rise to 15% (Anonï¼Œ 2007).
2.2 Aircraft cloud is another culprit of global warming
Cloud is a kind of visible trails which is formed by condensed water vapor of aircraft engine emissions aircraft. At an altitude of 8000 meters above, after the water vapor emitted it encountered the cold atmosphere; because of the cold atmosphere it will form numerous small water droplets or small ice particles in instantaneous cooling time. Its' average width is two kilometers, but also durable to leave and are often able to maintain a few hours before gradually dissipated after the aircraft. National Aeronautics and Space Administration (NASA) research results indicate that a large number of aircraft exhaust emissions created a great impact on climate of United States. From the year 1975 to 1994, the average temperature of United States has risen 1ã€‚C. The increase in climate research is a very alarming figure. According to the data from the European meteorological satellites, they show that now cirrus area caused by jet exhaust is 10 times more than itself (Royal Aeronautical Societyï¼Œ 2002). An increase in the number of cirrus causes the Earth's heat radiation from the atmosphere difficult to open, thus exacerbates global warming trend.
3 The initiatives of controlling air pollution
3.1 Airlines improve efficiency in the use
According to the report of the United Nations Intergovernmental Panel on Climate Change (IPCC), it shows that nearly 12% of fuel consumption of the aviation industry is due to the low efficiency (Jolly & Weiss 2009). Mainly it manifested that the landing time is too long, air cooling time is too long; the flight route is not the shortest; the utilization of airport is low and so on.
Implement "eco" landing. Replacing the current ground-based navigation system with area navigation (RNAV) will enable to shorten the aircraft flight time and reduce carbon dioxide emissions, and the more flexible use of airspace, improving air flow limitation and air traffic management, but also help reduce aircraft fuel consumption, thus improving the problem of global warming (Federal Aviation Administrationï¼Œ 2008). Scandinavian Airlines is outstanding performance in this respect: its flights have adopted a new landing system; each flight can save 100 kg of fuel. At the same time, the new system can reduce emissions and lower noise generated in the process of aircraft landing, and will shorten two minutes for each flight time. According to "cross-Atlantic co-reduction plans," using this environmentally way of landing makes that each flight will be able to save about 200-400 kg of fuel on average.
Reduce the cost of air cooling and reduce carbon dioxide emissions. When the aircraft flies at high altitude, its temperature is almost minus 50 degrees, so it does not need air-conditioning. But on the ground due to sunlight leading to the cabin temperature rises during the summer before taking off to start an auxiliary power unit (APU) for cooling. If the running time of the APU can be shortened by 10 minutes, a large passenger aircraft could reduce emissions which are considerable of 169 kilograms carbon dioxide. According to the recommendations of the pilots, Japan Airlines began to try to lay down their windows sun visor measures spending the night at the airport, overnight parking, the aircraft will be arriving to lay down their windows, sun visor, inhibit the next morning due to sunlight, which led to the warming cabin.
Optimize the flight line. Airline pilots greatly enhance the technology to ensure the most accurate flight along the shortest route flight, thus shorten the flight time and reduce carbon dioxide emissions.
Optimize the use of airport. Flights waiting for take-off the will have a fixed parking spots on the ground to replace the procedure of waiting for take-off with the engine, thereby it can reduce energy waste. In addition, the airport will take precise control of operation on the flight in order to reduce flight delays and cancellations.
3.2 Aircraft industries developed bio-fuels and reduce carbon dioxide emissions
At present, there are basically three kinds of aircraft fuel: aviation gasoline, aviation kerosene and aviation diesel fuel. The vast majority of civilian aircraft use aviation kerosene now. As traditional fossil fuel, aviation kerosene is again seen as the culprit of the aviation industry carbon emissions. In order to reduce oil dependence, costs and achieve emissions reductions, looking for a large scale for commercial development of bio-fuels has become a global aviation industry imperative. As an efficient alternative of petroleum-based fuels, bio-fuels is not only renewable, sustainable and do not need any modification to existing engines.
The use of food crops as raw materials for bio-fuels are called first generation bio-fuels, even though the first-generation bio-fuels has so far experienced a mere few years of development, and only in very few countries achieved the large-scale production, but its limitations are quickly apparent: take up too much farmland and threaten food supply (Aline Leónï¼Œ 2008). At present, countries all over the world focus on developing a second-generation bio-fuels, compared with the first generation, second generation bio-fuels will not be diverted to food production and raw materials used in water resources or arable land and it will not cause deforestation behavior. In the research and development of second-generation bio-fuels, scientists have identified the three main plants: grass, trees and seaweed (Antonino Furfariï¼Œ 2008). Currently, the aircraft of Air New Zealand flight supply power from mixture of the bio-fuel of which jatropha and Jet A1 fuel of 50 percent each for one powered engines (Roland Conradyï¼Œ 2010); the test aircraft of the United States Continental Airlines flight is used with algae and jatropha extraction complex mixture of bio-fuels (Wang Qingï¼Œ 2009); Japan Airlines is the first test flight of three kinds of second-generation bio-fuels, a mixture of fuel, the ingredients are flax Camelina sativa oil (84%), jatropha oil (less than 16%), and algae (less than 1%)(Chinanewsï¼Œ 2008).
The more "cool" message from Switzerland than bio-fuels instead is the sun power. At present, the International Air Transport Association has become a strategic partner of sun powered aircraft. The aircraft which do not use any type of fuel recently opened a mystery in Du Bendorf airport near the Zurich of Switzerland.With a near-perfect, neat appearance, coupled with "zero-fuel, zero emissions" high-tech armed forces, this new type of solar-powered aircraft succeeds in attracting the eyes of the world's scientific and technical personnel, environmentalists and explorers, and becomes the star of the technological environment praised by people (Valavanis & P. Valavanisï¼Œ 2007).
3.3 Aircraft industries develop new materials and reduce the weight of the aircraft itself
By reducing the aircraft's own weight contribute to reducing fuel consumption, thereby reducing carbon dioxide emissions. This requires the development of new materials. For example, new materials polymer has characteristics of lightweight, high strength, corrosion resistance, and low power consumption, and is a new energy-saving environment-friendly material. The "Dreamliner" Boeing 787 uses more than 50% of the new polymer materials, and the aircraft weight reduces by 16% (Wagner & Norrisï¼Œ 2009); nano-structured composite metal materials will reduce the weight of the aircraft and so on, in theory, allow the aircraft to reduce the weight of 1-5%, fuel consumption can also declined 3% to 8% (Xinhua ï¼Œ2009).
4.1 To improve air traffic management and the efficiency of flight operations a year will be able to reduce the millions of tons of carbon dioxide emissions which will be an effective initiative.
4.2 In order to build the air transport industry into a green, environmentally-friendly industries, all participants should work together, because it is not a problem which can be solved by one company or one country alone.
4.3 The air transport industry must be multi-pronged, cross-border cooperation, and do everything possible to strictly control the air transport industry carbon dioxide emissions. To strengthen environmental protection without delay must adapt to the rapid development with the industry as a whole.
4.4 Governments should actively support the global air transport industry in environmental protection efforts, and supply more R & D funds and project support.