2700 kg of kerosene, 722 700 kg of cold air, 850 000 kg of air, 130 000 kg of hot air, 8500 kg of carbon dioxide (CO2), of which, as harmful substances: 30 kg of nitrogen oxides, 2.5 kg of sulfur dioxide, 2 kg of carbon monoxide, 0.4 kg of hydrocarbons, 0.1 kg of fine dust / soot, 3300 kg of water vapor (H20).
Every year air traffic is responsible for the release of a total of 800 million tons of CO2 into the atmosphere. A project implemented by NASA, in collaboration with some teams of researchers in Germany and Canada, aims to solve or at least contain this problem as much as possible. The initiative is based on the idea that the use of special biofuels can reduce the environmental impact by up to 70%.
The composition of aircraft emissions is similar to those of other means of transport or, more generally, to the emissions produced by the combustion of a liquid hydrocarbon.
The emissions consist of polluting substances (substances harmful to the environment and health) and non-polluting substances.
Among the pollutants we find:
- Gaseous substances:
- NOx nitrogen oxides (NO monoxide, NO2 dioxide, N2O oxide);
- Sulfur oxides SOx (sulfur dioxide SO2, sulfuric anhydride SO3);
- Carbon monoxide CO;
- Non-gaseous substances:
- Particulate (PM) mainly consisting of carbon particles with dimensions ranging from nm (one nanometer corresponds to 10-9 meters) to μm (one micron corresponds to 10-6 meters) and, to a lesser extent, metal powders, silica , residues of additives;
- Unburned hydrocarbons (UHC,Unburned HydroCarbons).
The non-polluting substances are:
- carbon dioxide (CO2);
- water (H2O emitted as a gas by engines).
Emissions contain, in small percentages, even lead, chlorine and bromine from the anti-knock drugs used.
The Kyoto Protocol, adopted in 97, laid the technical-legal bases for reducing greenhouse gases but no constraints were imposed on emissions related to air transport, therefore for aircraft it is allowed to use anti-knock agents such as lead tetraethyl which is a highly toxic substance. Tetraethyl lead was eliminated from car fuel in most countries during the 1980s and 1990s.
Aviation produces 3.37% of the total emissions, a low percentage compared to the total emissions, but the different environmental impact linked to the high altitude and the presence of anti-knock substances that are harmful to the environment and health make it necessary to study it further. Even emissions at ground level can reach high levels due to air currents, from 8 to 16 kilometers in height, but they are occasional events, while aircraft emissions, except during take-off and landing, take place mainly at high quote.
The use of alternative fuel for air transport is currently minimal and may remain limited in the short term. Alternative fuels could make an important contribution to mitigating the current and future impact of aviation on the environment.
There is growing interest in „Electro-fuel“, alternative fuels with zero emissions. However, to date, few demonstration projects have been presented due to high production costs.
Six bio-based fuel production routes have already been certified and others are in the process of being approved.
The European Union would therefore be able to increase the production capacity of bio-based fuel for the aviation sector, although use by airlines remains limited due to numerous factors, including the higher cost than to conventional fuel.
At the center of the British researchers‘ air-saving experiments, three rows of screens called baffles capable of directing the exhaust gases of departing and arriving aircraft towards the top, eliminating them from the atmospheric belt near the airport ground. Acting as a sort of chimney that pushes pollutants into the air that later fall to the ground in a diluted manner. «It is», explains Michele Giugliano, professor of atmospheric pollution at the Milan Polytechnic, «of a parallel intervention to limit the damage. The idea could, given the contained costs, prove to be strategic ». A strategy that, according to Giugliano, turns out to be more effective the closer the panels approach the runways to better divert the polluting agents emitted during the taxiing phase. Take-off is the maximum moment of emissions because all the power of the plane is involved ». But that alone does not solve the problem anyway. «The diversion of the discharges can be considered a parallel action. A different trend compared to classic interventions to improve air quality.
Different strategies of nations to limit the problem of air pollution in air traffic. Last, in chronological order, the experimentation of anti-pollution screens tested in England at Cranfield airport. A project that involved numerous organizations, and which gave encouraging results on reducing the concentration of aircraft exhaust gases.