Brussels Airport strengthens its actions to reduce ultra-fine particle emissions and moves its engine test run site.

Within the scope of Forum 2040, the open dialogue regarding the long-term development of the airport, Brussels Airport has committed to conducting further research in the fields of ultra-fine particles (UFP) and of ground noise from engine test runs. From the ultra-fine particles measurements carried out in 2019, it seems that, for UFP, the results are comparable to those from the study carried out four years earlier by the Flemish Environment Agency and to those at other airports. The average results are also comparable to those measured in built-up urban areas. Improving local air quality is part of Brussels Airport’s sustainability policy and a priority for the airport. Several measures to improve air quality have already been implemented. For instance, aircraft taxi time has been shortened, and passenger and service vehicles at the airport have been replaced by more eco-friendly vehicles. Moreover, Brussels Airport has decided to move the engine test run site to reduce the noise nuisance for people living near the airport.


1. Ultra-fine particles

Emissions of ultra-fine particles (UFP) are a global phenomenon. All fossil fuel-based traffic is a source of UFP, as well as many other forms of human activities. Studies carried out by the Flemish Environment Agency in 2015 have shown that road traffic in Flanders is the largest source of (ultra) fine particulate matter. Locally, air traffic contributes to increasing concentrations of ultra-fine particulate matter. Worldwide, scientific research on UFP is still in its early stages. No threshold has been set by the World Health Organization or other bodies yet. Brussels Airport is at the forefront of this research and was the first major airport to have measurements carried out outside its own airport site.

At the request of Brussels Airport, the VITO (Flemish Institute for Technological Research) has mapped out the emissions of ultrafine particles at 8 measurement points at and around the airport, over the course of two months in summer and two months in winter. The results are completely in line with an earlier study carried out by the Flemish Environment Agency in 2015, as well as with the results measured at other airports.

The average concentration of UFP in the airport’s vicinity is 10 to 20,000 particles/cm³. This is comparable with measurement points in built-up urban areas. Locally, short peaks occur at times which can be up to 7 times higher. The highest peaks were measured on the runways themselves at take-off or landing. The concentration of UFP decreases rapidly as the distance to the airport site increases.

Ten measures to reduce ultrafine particles (UFP)

Brussels Airport did not wait for this study’s results to act. Sustainability is a strategic priority of the airport and improving local air quality is part thereof. Brussels Airport has already implemented various measures to improve air quality around the airport and has launched several initiatives which will have an additional effect in the future.

This is how Brussels Airport is reducing UFP:

  1. All passenger transport on tarmac is carried out by electric buses since 2018.
  2. Service vehicles using diesel/petrol as fuel are being replaced by CNG service vehicles.
  3. Aircraft are immediately connected to the 400Hz ground power unit at their stand which allows to cut the aircraft engines as soon as possible and only restart them at the last possible moment.
  4. The taxi time of aircraft is kept as short as possible. An aircraft only leaves the gate after it can be guaranteed that it can taxi to the runway and take off immediately. This prevents various aircraft with running engines from having to wait for their turn at the runway. Aircraft are also held at the gate until it is known that they can land at their destination as quickly as possible. This prevents aircraft from needlessly circling in the air until allowed to land.
  5. There are differentiated rates for airlines based on noise performance. Thus, we wish to encourage the use of more modern and therefore less polluting aircraft. The noisiest aircraft pay up to 3 times more take-off and landing fees.
  6. Aircraft only taxi using a single engine. Even if that engine has to work a little harder, it produces fewer emissions than two engines.
  7. The possibilities of using electric taxiing are being examined. We are examining how we can apply this at the airport.
  8. The use of more modern and less polluting aircraft will be stimulated even more by further differentiating charges based on emissions and noise.
  9. Together with a number of international partners, Brussels Airport is the leading airport to join in an EU research programme to provide sustainable fuel (biofuel, synthetic fuel) at the airport and plays an active role in offering this to its airlines.
  10. Brussels Airport is collaborating with scientific researchers to apply innovative technologies for the reduction of UFP at the airport. For instance, the possibility of capturing UFP as close to its source as possible is being investigated.

The first six measures are already in place today. With the last four, Brussels Airport wants to help examine and implement sustainable innovative developments, to achieve even more improvement in the future.

2. Reducing ground noise during engine test runs

In another study, Brussels Airport mapped the impact of ground noise from engine test runs at two locations on the airport site: the current test run site, and the test run site that can be used as an alternative if the other one is not available. Engine test runs, which are required to guarantee the safety or aircraft operations, are carried out on average some 270 times a year. These engine test runs are compulsory among other things after maintenance on the engines of an aircraft. As an environmental measure, Brussels Airport stipulates that engine test runs may only take place between 07:00 and 22:00.

Over two weeks, measurements were carried out at 11 measurement points at and in the vicinity of the airport. The observed values varied greatly depending on the weather conditions. During some engine test runs, no significant increases in noise were observed at various measurement points in the vicinity. With other test runs, noise peaks of between 50 and 75 dB were measured. These measurement results form the basis for the search for alternatives to reduce noise pollution.

Brussels Airport has decided to move the engine test run site. The new location, in combination with the provision of noise mitigation measures, such as noise barriers, will reduce noise pollution for local residents. Technical studies and simulations are currently being carried out in order to obtain the best possible design at the most suitable location. At the same time, research is being carried out into innovative technological measures that could contribute to further noise reduction. The new engine test run site will be operational by the end of 2021.

The slides explaining the results of the UFP and engine test run measurement campaigns as well as VITO’s full report on UFP can be consulted via this link

Brussels Airport, 21 February 2020



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