Emissions - further information

Further information on aircraft engine emissions

Types of emissions

Kerosene is the main component of aviation fuel which is used to provide propulsion for current commercial aircraft. Like other fossil fuels, kerosene produces CO2 and water vapour as the products of complete combustion. As the combustion process is not completely efficient, partial oxidation products such as carbon monoxide (CO) and oxygenated organic compounds are produced and emitted. Depending on the load on the engine and the mixing processes in the combustor, soot can be formed and emitted together with unburnt hydrocarbons. 

The emission profiles vary with the phase of the flight. Although the sulphur content of the fuel is reduced during the refining process, aviation fuel still contains a small amount of sulphur and this is converted to sulphur oxides (SOx) during the combustion process. The temperatures reached in the jet engine combustor result in the formation of nitrogen oxides (NOx) through high temperature reactions of the nitrogen and oxygen present in the combustion air.

Impacts on local air quality

Smoke trails emitted by a jet aircraft

The impact of the aviation industry on local air quality, especially in the vicinity of airports, has long been recognised. The pollutants of concern are the emissions of NOx, CO, hydrocarbons and soot.  Emissions limits from aircraft engine exhausts have been defined for these pollutants by the International Civil Aviation Organization (ICAO), although the limits only apply during the Landing Take-Off (LTO) cycle. In addition to aircraft emissions, local air quality is further compromised by pollution from motor vehicles along extensive road networks that provide access to airports.

Impacts on climate change

The other environmental concern for the aviation industry is the contribution of aircraft exhaust emissions to climate change. The most important emissions are considered to be those of CO2 and NOx. Subsonic aviation currently contributes between 2-3% of the CO2 emitted from all fossil-fuel combustion. The emissions of NOx lead to the production of ozone (O3) in the upper troposphere. There is also increasing scientific concern about SOx and soot emissions. The impact of aerosol and cloud formation from these species could potentially have a large but currently uncertain impact on climate change.

Aircraft Engine Emissions Databank

This DataBank contains information on exhaust emissions only for those aircraft engines that have entered production. The information was provided by engine manufacturers, who are solely responsible for its accuracy. It was collected in the course of the work carried out by the International Civil Aviation Organization (ICAO) Committee on Aviation Environmental Protection (CAEP).

This Databank was hosted by the UK CAA on behalf of ICAO until January 2012.  However responsibility for it has now been transferred to the European Aviation Safety Agency (EASA). The latest version can be accessed on the EASA website.

Any questions, comments, data input or requests with respect to the ICAO Aircraft Engine Emissions Databank should be made by email to emissions.databank@easa.europa.eu