The following is intended to serve as a guide to anyone looking to find and compare figures on the environmental impact of the UK aviation industry.
It outlines the key measures of aviation's environmental impact, highlights where data on these measures is publicly available and provides some guidance on interpreting this data.
In 2020, the CAA began a project to consider consumer’s interest in and access to information on aviation’s environmental impacts when they book flights. This work has involved quantitative and qualitative consumer research, which is available to read in this report, and broad stakeholder engagement.
The first phase of the project has concluded that consumers desire greater information and the CAA should work with industry and stakeholders to consider how best to facilitate that in the next phase of the work
Aircraft emit a range of greenhouse gases throughout the different stages of flight. Aircraft are unique in that they emit gases directly into the higher levels of the atmosphere. Research suggests that gases can have different effects when emitted at this altitude relative to emission at ground level.
Scientific evidence strongly indicates that greenhouse gases contribute to climate change. CO2 is generally viewed as the most problematic greenhouse gas. While many factors contribute to emissions in aviation, CO2 is primarily generated by burning carbon-rich 'fossil fuels' in engines. It has a long life cycle and plays a key role in climate change. Some factors are under the control of airlines, airports or regulators, but even the weather plays a part.
Key measures of climate change impact
Airlines and airports are not required to publish their emissions, but a growing number choose to do so voluntarily. There are therefore no official reporting standards, but most choose to report data as CO2e (CO2 equivalent, which includes other greenhouse gases).
Passenger load factors (the percentage of actual passengers carried relative to the number of seats available) are good indicators of efficiency. Efficiency, in environmental terms, is a measure of emissions per passenger or tonne of freight carried. The aviation industry looks to increase efficiency as well as reducing overall emissions.
Where to find data
- Data published by specific airports or airlines can be found on their respective websites
- Some companies participate in the Carbon Disclosure Project, a global self-disclosure system.
- Sustainable Aviation, an industry body, reports annually on its members' performance, showing absolute CO2 emissions and efficiency.
- A report from the Committee on Climate Change assesses how further expansion in aviation beyond 2020 would affect the sector's ability to meet government carbon reduction targets.
Flight operators in the European Economic Area are required to submit data under the EU Emissions Trading System. The European Commission publishes annual lists of emissions for those participating in the scheme.
The National Atmospheric Emissions Inventory includes data on the carbon emissions produced by different categories of aircraft.
Interpreting the data
Emissions calculations are difficult and often use assumptions due to the absence of complete data. There are a number of factors to be aware of when studying and comparing emissions data:
- Differences in calculation methods: when comparing emissions data, it is important to ensure that the calculation method used is the same, but different organisations often use varying methodologies. An example is where the UK Government uses airline fuel sale figures with a conversion factor, while airlines typically use fuel burn data with a conversion factor.
- Risk of double counting: different organisations report the same emissions (e.g. airports and airlines).
Different forecasts also use different assumptions and methodologies which should be taken into account when analysing such data. For example, 2050 forecasts from Government and Sustainable Aviation have used different assumptions about air traffic control efficiency improvements, speed of introduction for sustainable fuels, relative efficiency of new aircraft and degree of carbon trading that may occur.
Noise is often defined as 'unwanted sound'. The law is clear that sound only becomes noise when it exists in the wrong place or at the wrong time - causing annoyance, sleep disturbance or other effects. Unlike most other forms of pollution, noise pollution depends not only on the physical qualities of sound itself but the human reaction to it. This makes measuring noise pollution a complex process.
Key measures of noise impact
Two basic measures for assessing noise impact are:
- Leq which means the 'equivalent continuous sound level'.
- Lden which uses an annual average of the Leq but also takes into account the additional annoyance/disturbance of noise generated in the evening and at night.
To assess the impact of noise, analysts identify how many homes and residents are located in areas where the Leq is over 57dBA or the Lden is over 55dBA (the levels at which noise has been considered to cause community annoyance). Average noise levels around an airport can be shown on maps known as noise contour maps.
As noise is caused by every aircraft taking off and landing, another way of estimating impact is by considering the number of aircraft movements at an airport.
Where to find data
A number of airports publish a range of data about noise and aircraft movements which can be found on airport websites.
Different airports provide different information depending on local circumstances. Information that may be available include:
- Operational information such as runway use and direction of take-off and landing so that you can assess when aircraft will be flying overhead.
- Flight-tracking tools that allow you to track individual flights.
- More detailed information on what generates noise and how the airport is attempting to reduce this impact.
- Performance reports of how your airport is performing in relation to noise.
- Explanation of any airspace change proposals or trials being operated at your local airport.
Interpreting the data
While aircraft movement figures can provide a rough picture of noise impact at different airports, noise effects can be highly subjective or dependent on other noise impacts in the local area. Generally, airports in more densely populated areas are considered to have a higher impact as more people are likely to be affected.
Different airports have different obligations for monitoring and reporting air quality. Some reporting requirements are necessary by law through planning obligations.
Comprehensive information about types of pollutants, their sources and their effects can be found through UK Air Aviation-specific information can be found from the Centre for Aviation Transport and Environment (Manchester Metropolitan University) and the Laboratory for Aviation and the Environment (MIT).
Key measures of air quality
The main pollutants monitored are:
- Nitrogen dioxide (No2)
- Nitric Oxides (NOx)
- Particulate matter (PM)
Where to find data
Data on the levels of nitrogen Dioxide (NO2) and particulate matter (PM) at UK can be found on airports' websites.
Heathrow airport has produced a dedicated resource, Heathrow Airwatch, to allow data on local air quality to be accessed and monitored.
Interpreting the data
It should be noted that air quality monitoring stations will capture air pollution from all sources (roads, industry etc.) As such, air quality levels will not be solely attributable to aircraft activity.
While the most common concerns around the environmental impact of aviation are in terms of climate change, noise and air quality, there are other direct impacts that aviation can have on the local environment. It is difficult to produce quantitative data on many of these subjects. Instead, many airports publish reports or strategic plans to cover these concerns - available on their websites.
Biodiversity, wildlife and tranquillity
There is Government Guidance on safeguarding airports which covers planning issues, but for more information, please contact your local authority and airport. In addition, a growing number of airports have developed plans to manage biodiversity in and around their sites, which can be found on their websites.
There are a limited number of areas around the UK that, for civil aviation purposes, are officially designated as bird sanctuaries. Civilian pilots are then asked to avoid flying over these areas below a specified altitude. This is not mandatory, so designating the site a bird sanctuary does not make it a 'no-fly' zone. You can find a full list of designated sites in the UK Aeronautical Information Publication (UK AIP), the standard information given to all civilian airspace users.
Tranquillity is often linked to engagement with the natural environment and aviation activity can impact on tranquillity. For more information on tranquillity, you may wish to consult the following:
Every day, thousands of people travel to airports - not just passengers, but employees and suppliers too. The transport choices they make can have a significant effect on the environmental impact of the airport as a whole.
A number of airports publish surface access strategies which can be found online.
Aviation activity generates considerable waste that needs to be disposed of. This consists of:
- Waste generated on aircraft.
- Waste generated at the terminal.
- Waste generated by constructing new airport infrastructure.
Waste is managed locally by airports and will involve a mixture of waste disposal methods. Like any other organisations, airports are being challenged to recycle and re-use waste wherever possible. Waste performance data is published by the UK's major airports and is often available in sustainability or 'corporate social responsibility reports'. Most of the UK's major airlines also have information on waste management which are also available online.
Aviation fuel leaks and spillages can damage water quality. There are strict rules in place around storage and handling of fuels. You can read more about these in the CAA publication CAP 748: Aircraft fuelling and fuel installations management.
During the winter months, aircraft sometimes have to be de-iced to allow their safe departure. De-icing fluid can impact water quality if not handled correctly.
Airports are also large consumers of water - some larger airports consume as much water as small towns. Information on the water consumption of many of the UK's major airports is available online - most often in airports' sustainability or 'corporate social responsibility' reports.
Between 2011 and 2014, the CAA compiled data on emissions, air quality, waste, water and noise form reports published by airlines and airports. Due to the difficulty of collecting comparable, 'like for like', data and changing reporting strategies year on year, the CAA no longer regularly updates this information. Existing data has been reproduced in this document. The CAA cannot ensure its continued accuracy.
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