Some 17,000 people work in about 600 different companies at Stockholm Arlanda Airport. The airport is comparable to a small city. Environmental issues have long been given priority, and the airport works in a number of different areas to reduce its environmental impact. Lower carbon dioxide emissions are one of its focus areas.
Swedavia, which owns and operates Stockholm Arlanda, has cut its emissions of fossil carbon dioxide at the airport by more than half over the past seven years. The airport’s buildings are warmed up with district heating from biofuel, and all electricity purchased is produced from renewable sources, such as biofuel, solar, wind and hydropower. The airport is also gradually replacing its fleet of vehicles with environmentally sustainable vehicles.
An important goal for the airport is to also work with others to reduce carbon dioxide emissions from ground transport to and from Stockholm Arlanda – to make it smoother and easier to travel by train or bus. Naturally, the airport is also working in partnership with airlines to reduce the environmental impact from air traffic.
Carbon dioxide emissions cap at Stockholm Arlanda is unique
Stockholm Arlanda Airport is the only airport in the world that has a cap on carbon dioxide emissions in its environmental permit. This condition means that emissions from aircraft taking off and landing, from vehicular traffic to and from the airport, from internal vehicular traffic and from the heating of buildings may not exceed the level produced in 1990.
Compared to 1990, there are more passengers today flying on fewer planes from Stockholm Arlanda. The number of air passengers at Stockholm Arlanda has increased by about 35 per cent. Meanwhile, emissions from air traffic have fallen, but carbon dioxide emissions from vehicular traffic have increased.
Emissions from heating and from internal vehicular traffic have decreased by 75 per cent since 1990. Vehicular traffic today accounts for more than half of the emissions under the emissions cap.
Since 1994, air pollution measurements have been taken at Stockholm Arlanda, and the results show, among other things, that:
- the levels of sulfur and nitrogen (which contribute to acidification) in precipitation are no higher per unit area at Stockholm Arlanda than in the county of Stockholm on average.
- fir and pine trees at Stockholm Arlanda lose needles to roughly the same extent as trees in the the
- levels of pollutants are highest by the terminals and roads with the most vehicular traffic.
The way air pollutants spread depends on a number of factors, including the direction of the wind, wind speed and temperature. So it is difficult to determine how large a share of pollutants affects the different areas.
Emissions from air traffic
Aircraft engines produce the same emissions as those produced in the burning of fossil fuel – carbon dioxide, nitrogen oxide, hydrocarbons, soot and other particles, carbon monoxide and sulfur dioxide.
Sometimes there may be a strong smell of jet fuel at the airport. What makes the jet fuel smell is sulfur impurities, known as mercaptans, which have an intense, penetrating and characteristic smell in very small concentrations.
These sulfur impurities belong to the same group of compounds that produce odour problems associated with the manufacture of paper mass (the sulfate process). Mercaptans are non-toxic in the low concentrations found at Stockholm Arlanda.
Aircraft whirlwinds are not fuel dumping
All aircraft leave whirlwinds in their wake. When it is humid out, the whirlwinds are visible because condensation is formed from the steam in the air. It may sometimes look as if the aircraft is dumping fuel while landing. The whirlwind in the wake of an aircraft is called a vortex.
Fuel dumping very rarely occurs and only in emergency situations when a plane needs to make an emergency landing. Only the largest aircraft are able to dump fuel. If dumping is necessary, it must be done over water and at such an altitude that the fuel vaporises before it reaches the ground.
Precedence is given to modern planes with lower emissions
One way to reduce emissions into the atmosphere from air traffic is by Stockholm Arlanda encouraging airlines to use modern aircraft that are better for the environment – take-off charges are lower the lower the level of nitrogen oxide and hydrocarbon emissions an aircraft engine produces. The aim is to induce airlines that have older planes with old engines to replace them with modern planes with cleaner engines.
De-icing of aircraft and runways
Aircraft are de-iced using propylene glycol, and when runways are de-iced, potassium formate is used. Potassium formate is a kind of salt and is used today instead of urea.
Propylene glycol and potassium formate as such have low levels of toxicity and break down easily. However, a lot of oxygen is needed in their decomposition, so the compounds could cause oxygen deprivation in watercourses and in the groundwater if large quantities are released. In order to minimise the impact on the water around Stockholm Arlanda, a number of measures are carried out.
Glycol is recovered after aircraft are de-iced
De-icing is only allowed on surfaces where a special drainage system for recovering glycol is installed. As much as possible of the glycol remaining on the ground once an aircraft has been de-iced is suctioned up by suction vehicles.
Because of the relatively high concentration of glycol, this fluid can be used for recycling or as an additional source of carbon in the local water treatment facility. The glycol fluid that is not suctioned up, which has a relatively low glycol level, runs into the glycol drainage system and is eventually pumped over to the Käppala water treatment facility.
Breakdown of chemicals takes place mostly in the airport’s treatment facility
Formate from de-icing and from glycol that drips off aircraft when they taxi out to a runway ends up in the surface water that runs off runways and aprons. Most surface water is conveyed to surface water treatment facilities, where the chemicals are broken down through biological processes. This breakdown is largely carried out in the airport’s water treatment facilities before the water is conveyed into watercourses.
Water samples show improvements in the Märsta River
The water quality of the Märsta River has improved in recent years, partly as a result of Stockholm Arlanda’s measures to reduce its impact on the watercourse. The catchment area of the Märsta River includes the town of Märsta, many companies, farms and the airport, which all have an impact on the watercourse.
In an inventory of the Märsta River taken in 1988, the water quality was rated “poor”, in part as a result of the urea and glycol used at Stockholm Arlanda, which contributed to oxygen deprivation in the river. The water quality has improved since then, and today the Märsta River has been classified as having “moderate ecological status” and “good chemical surface water status” according to the assessment criteria of the EU Water Directive. The objective is to achieve “good ecological status” by 2021.
The presence of the chemical PFOS at the airport
In a survey conducted in 2008, the presence of the chemical PFOS was identified, among other places, in Lake Halmsjön and the river Kättstabäcken. Since then, Swedavia has worked to increase knowledge about where PFOS is produced at the airport and how it spreads and acts. A pilot facility is operating in order to assess a treatment method.
Treated wastewater can be used as fertiliser
It is common for wastewater from operations such as vehicle washing facilities, workshops and aircraft hangars to contain elevated levels of metals and oil. At Stockholm Arlanda, there are a number of treatment facilities that remove these pollutants before the water is conveyed to the local treatment facility.
Treating wastewater is important since the sludge formed in the treatment facility contains valuable nutrients and can be used to some extent as fertiliser in fields.
200,000 square metres of membrane protects groundwater around Runway 3
Runway 3 extends in part over a boulder ridge that contains groundwater, so it is especially important that glycol and salt residues do not reach it, which was also a high priority when the runway was built. The water from the runway thus runs down into sewers along the sides of the runway and is then conveyed to an overflow area and treated if necessary.
A 1.5 millimetre water-impermeable membrane has been laid out in the area of the boulder ridge at a depth of 1-2 metres. This allows the water from the sides of the runway to flow into the runway’s sewage system. In all, some 200,000 square meters of membrane has been laid out by Runway 3, the equivalent of 28 football pitches.
The noise on the ground is loudest on take-off since there is high engine thrust. In contrast, landings do not require strong engine thrust but they still generate high noise levels on the ground during the final part of their approach, since this is done at low altitude. The environmental impact that gives rise to is always monitored, and Stockholm Arlanda is continuously working to reduce this.
Lower costs for aircraft that make less noise
Major international efforts are under way to reduce aviation noise. For instance, the noisiest aircraft are no longer allowed to operate at airports in the EU. This work has encouraged airlines to replace planes that make the most noise or replace older engines.
At Stockholm Arlanda, airlines with modern, quieter aircraft models also pay lower charges than those with older and noisier models.
Measures to reduce noise
Below are four priority areas that the airport is working actively with, in cooperation with neighbours, the Stockholm County Council and the Swedish Environmental Protection Agency, to reduce noise from air traffic at Stockholm Arlanda Airport.
Changes in departure patterns and adjustments in departure routes
To improve the situation for people living near the airport, changes in departure patterns and minor adjustments in SIDs, that is departure routes, are being made. These changes mean that flight paths avoid densely populated areas better than before.
Higher approach altitude
By raising the approach altitude from 2,500 feet (750 metres) to 4,000 feet (1,200 metres), the noise level over some densely populated areas can be reduced.
Are a kind of “eco-driving” with aircraft. Allowing the plane to descend evenly in conjunction with landing – instead of step by step – saves on jet fuel and reduces noise and air emissions. In a green approach, landing time can be determined earlier than in regular cases, which in turn means that the pilot glides in the final phase with the engines at a lower RPM and without unnecessary waiting time in the air.
With curved approaches (RNP-AR, Required Navigation Performance – Authorisation Required), aircraft can avoid flying over densely populated areas during their approach. Carrying out curved approaches requires very advanced navigation equipment on board the aircraft.
Open dialogue and increased environmental awareness
Along with steps to limit noise, measurements are taken and test flights are performed, and there is also a programme for air traffic controllers and pilots to further raise environmental awareness. An open dialogue with Stockholm Arlanda’s neighbours is also an important part of the work, and the airport strives to plan departure and approach routes so that the noise disrupts as little as possible and is as low as possible. Homes subjected to the most noise have been sound-insulated.
The buildings at Stockholm Arlanda are warmed up with district heating based on biofuel. Swedavia also purchases “green electricity certificates” equivalent to its entire electricity consumption at the airport. These certificates guarantee electricity production from exclusively renewable sources, that is, wind, solar, hydropower and/or biofuels.
In the summer of 2009, Stockholm Arlanda also inaugurated the world’s largest energy storage unit – a so-called aquifer – in the nearby boulder ridge known as Brunkebergsåsen. The airport is both heated and cooled efficiently using the aquifer and without any environmental impact during the summer or winter.
During the period 2005-2012, Swedavia’s energy use at Stockholm Arlanda was reduced by almost a third. Measures such as more efficient and better controlled lighting indoors and outdoors contributed significantly to this reduction. Thus far, 10,000 energy-efficient LED diodes have replaced conventional light bulbs at the airport, cutting electricity consumption by as much as that used to heat 140 single-family homes with electricity.
Other examples of measures implemented are heat recycling in the terminals, more efficient ventilation and RPM-regulated electric motors.
The aquifer, which stores and reuses cooling and heating, can save as much energy as that used by 2,000 single-family homes.
Arlanda Energy awarded the Swedish Energy Prize
Swedavia Arlanda has worked systematically with energy issues for a number of years, and in 2009 the airport was awarded the Swedish Energy Prize for its business model, which takes a comprehensive approach to the airport’s energy issues. The Swedish Energy Prize is handed out by the technology consultant Sweco for technological ideas and innovations that are tested in real life and proven to save energy.