The Airport Carbon Accreditation (ACA), is a certification that helps airports manage and reduce their carbon footprint, improving sustainability in aviation.
According to research by the International Energy Co-operation (IEC), world air passenger traffic has grown from an estimate of 0.2 billion passengers in 1980 to a peak of 1.9 billion passengers in 2019. Despite a sharp drop in passenger traffic due to the Covid-19 pandemic, global aviation trade association the International Air Transport Association (IATA), revealed that as of December 2023, international air travel has made a marked recovery of nearly 94.7% to pre-covid levels. More airplanes in the air means busier airports and increased energy consumption in the aviation industry. With growing concerns about climate change and environmental degradation, the need for sustainability in aviation has never been more urgent. From airlines to airports, industry stakeholders are increasingly embracing sustainable practices to reduce their environmental impact. One of the most important mechanisms in this effort is the Airport Carbon Accreditation (ACA), a certification that helps airports manage and reduce their carbon footprint.
The aviation industry contributes around 2-3% of global ghg emissions (CO2e), making it one of the more carbon-intensive industries. Sustainability in aviation covers a range of areas, from fuel efficiency and the use of renewable energy to waste management and water conservation. Airports, as critical components of the aviation ecosystem, are at the forefront of implementing green practices. As part of their sustainability initiatives, airports around the world are adopting energy-efficient technologies, reducing waste and employing carbon management strategies to mitigate their environmental impact. This is where the ACA plays a key role, providing airports with a structured pathway to achieve sustainability goals.
Airport Carbon Accreditation is the only globally recognised carbon management certification programme for airports. Launched by Airport Council International (ACI) Europe in 2009, it aims to promote effective contributions by airports in the fight against climate change. The programme provides a structured framework for active carbon management at airports, covering operational activities that contribute most to carbon emissions. The program consists of five primary levels of certification, with two additional intermediary levels, allowing airports to progressively enhance their carbon management and sustainability efforts. These are structured as follows:
These levels acknowledge that airports are at different stages in their journey towards comprehensive carbon management. ACA addresses the carbon emissions under an airport’s direct control, as well as those associated with activities from third parties such as airlines and ground service providers. This comprehensive approach ensures that all aspects of airport operations are assessed and managed in the context of sustainability. As of December 2023, over 500 airports worldwide are certified under the programme.
ACA operates across seven levels of accreditation (levels three and four each have two initiatives), each representing a different stage of an airport's journey towards reducing its carbon footprint:
Level 1 (Mapping):
The first step in the accreditation is for an airport to calculate and report its carbon footprint. Focusing on Scope 1 and Scope 2 emissions as defined by the Greenhouse Gas Protocol. To achieve this level, airports must identify all direct emissions from owned or controlled sources (Scope 1) and indirect emissions from the consumption of purchased electricity, heat, or steam (Scope 2). The process involves collecting accurate data, calculating annual carbon emissions, and compiling a comprehensive carbon footprint report which is submitted to an accredited ACA verifier for review. Additionally, airports must sign a formal commitment to emissions reduction, demonstrating their dedication to environmental sustainability. This step forms the foundation for future sustainability initiatives, as it helps airports identify the key sources of emissions that need to be addressed.
Related Insight: The Difference Between Scopes 1, 2, and 3 Emissions.
Level 2 (Reduction):
Once the carbon footprint is established, the airport must begin reducing its emissions. To achieve Level 2, airports must develop and implement a carbon management plan that includes specific measures to reduce Scope 1 and Scope 2 emissions. This involves setting reduction targets, implementing energy efficiency projects and monitoring progress. The main difference between Level 1 and Level 2 is that while Level 1 focuses on measuring and reporting emissions, Level 2 requires airports to take concrete actions to reduce those emissions and demonstrate measurable improvements.
Level 3 (Optimisation):
Level 3 focuses on Scope 3. The next step focuses on involving third-party stakeholders in the carbon management process. Airports work with airlines, ground handling companies and other partners to reduce their collective carbon emissions. Airports must also expand their carbon footprint to include Scope 3 emissions, which cover indirect emissions from sources not owned or directly controlled by the airport, such as aircraft movements and passenger travel to and from the airport. Additionally, airports need to demonstrate continuous improvement in their carbon management practices and provide evidence of stakeholder engagement and collaboration.
Level 3+ (Neutrality):
At this stage, airports can opt to become operationally carbon neutral as they can offset all residual Scope 1 and Scope 2 emissions after implementing reduction measures. This involves investing in carbon offset projects, such as reforestation programs or renewable energy projects, to compensate for the residual emissions. By doing so, airports can achieve carbon the first level of neutrality.
Level 4 (Transformation):
Level 4 Transformation in the Airport Carbon Accreditation (ACA) program requires airports to set absolute emissions reduction targets that align with global climate goals, similar to the Science Based Targets initiative (SBTi). By the end of Level 3, airports have a comprehensive carbon footprint that includes Scope 1, Scope 2, and Scope 3 emissions, as defined by the Greenhouse Gas (GHG) Protocol. The next step at Level 4 involves aligning these reduction targets with scientifically established pathways to limit global warming, ensuring that airports contribute to broader climate objectives. This alignment with SBTi principles underscores the commitment to achieving significant, science-based emissions reductions.
Level 4+ (Transition):
The second intermediary level is Transition where airports offset its remaining Scope 1 and 2 carbon emissions as well as some Scope 3 emissions from staff business travel, using internationally recognised offsets.
Level 5 (Achievement):
Level 5 in the ACA program represents the pinnacle of carbon management and sustainability efforts for airports. To achieve this level, airports must demonstrate a policy commitment to achieving and maintaining over 90% absolute CO2e emissions reductions in Scope 1 and Scope 2 and commit to achieving Net Zero emissions in Scope 3 by 2050. Airports are required to provide a detailed trajectory showing over 90% absolute CO2e emissions reductions from the baseline for Scope 1 and Scope 2, updated annually to ensure ongoing compliance. Additionally, they must forecast a Net Zero Scope 3 trajectory, aligned with ISO Net Zero standards and/or sector-specific Net Zero frameworks, including interim targets. Airports must also develop a comprehensive Carbon Management Plan to achieve these targets and a Stakeholder Partnership Plan to engage all relevant partners in the journey towards Net Zero in Scope 3. All these efforts must be verified by an accredited ACA verifier to ensure accuracy and adherence to the program’s rigorous standards.
Airports can measure their footprint independently or seek support from specialist companies like Tunley Environmental. The application process requires independent third-party verification of the airport's carbon footprint and management plans. Verifiers must meet specific qualifications and pass a programme examination. Once all documentation is in order, the programme administrator issues an accreditation confirmation. As part of our airport sustainability services, Dr Aaron Yeardley, Co-Head of Science at Tunley Environmental, has successfully completed the ACA Verifier Training Course and Examination. This certification enables him to verify the work of other companies as they assist airports in achieving their ACA targets.
ACA offers numerous advantages to participating airports including:
Airport Carbon Accreditation has a significant influence on sustainability in aviation's journey towards sustainability. This global programme offers airports a structured approach to measure, reduce and optimise their carbon footprint, acknowledging that each facility is at a different stage in its environmental efforts. The seven levels of certification provide a flexible framework, allowing airports of all sizes to take part and benefit from the programme's guidance.