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Reducing the use of APUs

Reducing the use of APUs

Airport growth will only be permitted through sustainable operations.

The Auxiliary Power Unit (APU) is an on-board turbojet engine, generally located at the rear end of the fuselage of an aircraft and powered by kerosene from its tanks. The APU provides the aircraft with power for the cockpit, lighting, the galley, air conditioning and engine starting when on the ground. Some degree of APUs use is therefore essential for aircraft operations on the ground.


The environmental and economic impacts of APUs cannot be ignored. Indeed, in the long term, their use can have a significant impact on local air quality, such as emissions of air pollutants and greenhouse gases, affecting both ground staff and the local environment.

In addition, APUs use a lot of expensive fuel; over 2000 litres per hour for a wide bodied aircraft. They also create noise just above the heads of apron workers. This noise can also affect local communities – depending on proximity.

In France, the Airport Noise Pollution Control Authority (ACNUSA) has also drafted a report [1] in which they strongly recommended airports and the French Aviation Civil Authority (DGAC) to limit the use of APUs. In this study, ACNUSA states that by promoting alternatives to APUs an Airport Operator can reduce atmospheric emissions and noise from aircraft ground operations, whist helping to reduce the fuel cost of flights – to benefit airlines and passengers.

[1] To know more : http://www.acnusa.fr/web/uploads/media/default/0001/02/1081_rapportacnusa2016.pdf


Whilst APUs are still needed  for some stages of ground operation, it is possible to provide alternative to allow their use to be reduced. These alternatives can replace the APU from shortly after the aircraft docks until it is ready to push-back. These alternatives include:

* External electricity via a heavy duty cable to the aircraft supplied from:       – The airport electrical supply – fixed electrical ground power (FEGP); or,- Small mobile diesel ground power units (GPU) on the apron.* Externally supplied air conditioning via a large hose supplied by:– A dedicated Pre-Conditioned Air (PCA) unit on the stand; or ,- A mobile diesel air conditioning unit on the apron* A mobile diesel compressor (Air-start) to start the engines.

Where these alternatives are supplied from airport systems this removes local emissions and noise completely and allows the use of renewable energy. Where the alternative is diesel powered, some noise and emissions will remain on the apron.

It should be remembered that some degree of APU use will still be required even with these alternatives being provided.

According to the Union of French Airports (UAF) [2] an APU emits between 15 and 30 times more CO2 than a GPU, which itself emits 7 times more than fixed installations of 400 Hz.

For example, Air France has succeeded in reducing its fuel consumption related to APUs by 11% in 2015 as compared to 2014 as a result of the implementation of fixed electrical ground power (FEGP) [3].

Therefore, it appears that the long-term use of FEGPs would both reduce emissions of air pollutants (including greenhouse gas emissions) and financial costs. It would also remove a potential health risk to apron workers.

[2] To know more: “Enquête sur le Développement Durable dans les Aéroports français”, 2011[3] To know more: http://csrreport2015.airfranceklm.com/web/app.php/fr/article/15/fr/pdf


According to the “Handbook for Evaluating Emissions and Costs of APUs and Alternative Systems”, the following parameters must be taken into account by airports:

* The investment costs for basic equipment purchase, installation and various upgrades of FEGPs,* The operational costs corresponding to the use of alternative systems to supply electrical energy and air conditioning to the aircraft. The purchase of electricity from the local supplier for this purposes is the main expense,* The maintenance costs involving the repair or upgrade of the system components. In addition, the implementation of various alternative solutions, whether they are fixed or mobile, requires an interdepartmental mobilization between maintenance teams, ground operations departments, air operations divisions and so on.

Envisa recognises the particular importance of the operational aspect of the use of alternatives means and APUs.

Although it is possible to identify certain general practices that can be applied at several airports which would generate significant environmental and economic gains, it should be noted that there is no universal solution. Case-by-case studies are necessary to have tailor-made solutions for each airport. For example, if we just take the “climate change” factor into account, it would imply several benefits or challenges that are different for each airport!

In other words, strategies to reduce the use or substitute APUs may not only vary according to the size, type and geographical location of airports, but also depend on the regulations imposed at national and European levels and also the benefits that will arise for a particular airport. There is no ‘one-size-fits-all’ solution.

This is why Envisa considers that in order to analyse and calculate the real costs of implementing fixed or mobile alternatives, a multi-criteria evaluation (economic, environmental, technical and operational) must be conducted.

Want to know more about sustainable airport development?Please contact us! We accompany and support European and International airports in reducing their environmental impact.
Established in 2004, Envisa is an environmental consulting company specialised in sustainable aviation.Our focus areas are mainly local air quality, greenhouse gas (GHG) emissions, noise & energy management.  Download our brochure!
Reducing the use of APUs

Newsletter #3 / Airport Local Air Quality: Problem or Opportunity


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Aviation & Environmental Solutions



Air pollution is one of the leading environmental causes of premature death in the European Union (EU). Over 400,000 premature deaths occur each year in the EU because of cardiovascular and respiratory diseases as well as cancer that are directly linked to poor air quality.

For more information, you can take a look on the Air quality in Europe – 2016.


The European Commission is conscious of the fact that immediate action is needed since the EU has not yet achieved its long-term air quality objectives. Indeed, the end of 2016 was marked by the revision of the National Emission Ceilings Directive 2001/81/EC (NECD) after several years of discussions. The new Directive (2016/2284/EU) on the reduction of national emissions of certain atmospheric pollutants – that is now in force – repeals and replaces the previous regime on the annual capping of national emissions of air pollutants.
The measures to reduce emissions or air pollutants are expected to lead to a reduction in the impacts of air pollution on health by around 50% in 2030 (compared to 2005).


Aircraft and all associated airport activities are sources of an assortment of gaseous and particulate emissions. Nitrogen oxides (NOx), volatile organic compounds (VOCs), carbon monoxide (CO) and particulate matter (PM) are the most important contributors on LAQ concerns.As one of the fastest growing sectors of Europe’s emissions, aviation (much like shipping) is often targeted for not taking sufficiently ambitious steps to match the progress made by cars, trucks, rails etc. The number of flights has increased by 80% between 1990 and 2014, and is forecast to grow by a further 45% between 2014 and 2035.

As regards legislation, all Member States are obliged to respect the Directive for total emissions of certain air pollutants. Moreover, Member States must transpose the Directive into national legislation by 30 June 2018 and produce a National Air Pollution Control Programme by 2019, setting out measures to ensure that emissions of the five main air pollutants are reduced by the percentages agreed by 2020 and 2030. At the same time the Commission is particularly vigilant and legal action against Member states for failing to enforce the air quality standards is becoming more frequent.

We note here that the most important part of domestic and international aircraft flights with respect to LAQ – the landing take-off (LTO) cycle – is included in the reporting obligations of all Member States. The pressure to reduce aviation emissions in the context of the EU air quality objectives is already shifting from the national to the local level.


Modeling is a pragmatic solution for quantifying the relative contribution of an airport to the measured air pollution levels and developing efficient emission reduction plans.

Perhaps it is possible to break the common perception that airport operations lead to poor air quality, if airports were to work together in a mutually beneficial way, which one might refer to as an “open-source approach”. This concept, that has its roots in the open-source software community, rests on the recognition that useful ideas can rise from people outside an organization’s own roster of employees. The benefits of this method include constant improvement and higher quality of results (thanks to increased auditability), customizability, flexibility and lower cost. What is needed to initiate such activity is a common platform that will enable airports to gravitate towards this new solution.

In this context, the EUROCONTROL Open-ALAQS tool is a significant inspiration. Built as an open-source plugin to an open-source geographical information system (GIS) respecting CAEP latest guidance, it simplifies the process of defining the various airport elements (runways, taxiways, buildings, etc.) and allows the temporal and spatial distribution of emissions (including CO2) to be calculated and visualized. Once the emissions inventory has been established, dispersion modeling – provided by another open-source software, AUSTAL 2000 – can be used to calculate pollutant concentrations at the airport and in the surrounding area.
Moreover, the system is compatible with EU legislative requirements for estimating 8-hour, 24-hour, and annual mean values of pollutant concentrations.

Although, every airport is unique, several characteristics can be categorized. Participation in an institutionally-endorsed community of users of complete open-source airport local air quality tool suite would allow airports to strengthen their efficiency, profitability and public image in a sustainable way.
It could also help them to meet voluntary engagements – such as Airport Carbon Accreditation – legal obligations as well as public expectations and elaborate communication strategies to address sustainability issues, engage stakeholders and can even support the development of robust carbon and energy management plans.
For more information / http://www.eurocontrol.int/services/open-alaqs
Contact / open-alaqs@eurocontrol.int
Download / the full White Paper
Envisa has developed, validated and maintained EUROCONTROL’s Airport Local Air Quality Studies (ALAQS) tool over the past 10 years. This included the coding of the fundamental core of the model and its interface, integration with various geographical information systems for graphically visualising and manipulating data, and post-processing outputs for use by other applications.

If you would like more information on local air quality,
please feel free to get in touch with us!
We have a wealth of experience in helping airports
all over the world to achieve reduce their impact locally.

2nd Edition of the 6Reen AVIATION

For its second edition, Air&Cosmos is organising the 6R conference in partnership with Envisa, with the support of The European Organisation for the Safety of Air Navigation, EUROCONTROL, which will host this must-attend event at its Experimental Centre in Paris on 11 & 12 October 2017.

This year, twelve themes have been selected to once again build a conference that will trigger interesting discussions around a sustainable aviation industry. The focus of this forum is on – what individual stakeholders can do in their organisations to optimize the sustainability of their operations, while also touching upon high level institutional actions.

Established in 2004, Envisa is an environmental consulting company specialised in sustainable aviation.
Our focus areas are mainly local air quality, greenhouse gas (GHG) emissions, noise & energy management.
Download our brochure!

Our goal is to help the aviation sector find sustainable & cost-effective solutions to manage their business. Check out our areas of expertise.

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