Network for Transport Measures

Particulate matters from aviation

In order to estimate the emissions of particulate matters (PM) from the aviation sector it requires detailed information regarding the engine and the combustion process. This information is today not public information. The emissions of NOX, HC and CO are regulated by ICAO through emission certification of jet engines. The certification data also includes fuel consumption hence enabling estimation of the CO2 emissions as a factor related to fuel consumption. By simulating the aircraft and its flying profile the data needed is available for emission calculation.

ICAO does not regulate the emission of particulate matters and therefore this information is not available in various databases as an emission index for PM. There is however a parameter called “Smoke number” (SN) available that gives some information regarding the amount of PM in the fumes. SN is based on some few measuring of PM by using various filters. Attempts have been carried out to correlate the smoke number to emissions of particulate matters. The method “First Order Approximation” (FOA) combines several of these methods for the conversion of SN to emissions of particulate matters into particulate matters described as a mass weight. The equation needs input of fuels consumption and the smoke number. A problematic factor is that very few of today’s jet engines specify different smoke numbers for different engine loads if specified at all.

The FOA method gives a simplified proposal to an equation for estimation of volatile particulate matters as a mass weight. The method has been accepted by ICAO/CAEP (Committee on Aviation Environmental Protection) as a temporary assumption of total emissions of PM from air traffic, ICAO however assumes that the method will continue to develop as soon as information needed is available. The latest version of the method approved by ICAO/CAEP is called FOA2[5]. The model must only be used a rough estimation of total PM emissions from air traffic.

The FOA2 methodology contains several simplifying assumptions and is based on a limited number of data and is considered as a temporary solution. ICAO/CAEP will continuously update the interim model until a validated and verified database for PM emission index for civil aviation is available.

Among the researchers in this field there are some scepticism regarding the FOA model as they fear that jet engine industry find the model sufficient and therefore will postpone more serious databases. There is furthermore a general debate going on about what emissions that are relevant to measure and regulate considering impact on health and climate.