IBA forecasts Heathrow’s third runway could double its CO₂ emissions

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According to insights from IBA’s NetZero platform, the most advanced aviation emissions intelligence and reporting tool, the expansion would result in an increased jet fuel demand of around 2.98 million tonnes annually. While some air traffic will shift away from domestic airports, partially mitigating the net increase in the UK’s total aviation emissions, Heathrow’s own CO₂ output is projected to climb by 5.92 million tonnesannually. This marks a 54% increase from 2024 levels, equivalent to Portugal’s entire aviation carbon footprint in 2024.
 
The expansion comes with a proposed strategy to mitigate emissions through Heathrow’s Sustainable Aviation Fuel (SAF) incentive scheme, aiming for 3% SAF usage in 2025 and 11% by 2030. However, IBA’s analysis shows that this would only offset a small fraction of the increase in CO₂ emissions. With the UK’s national SAF production capacity falling short of the target, achieving the 11% SAF blend could reduce emissions by just 0.2 million tonnes, far from enough to counterbalance the expected rise in pollution.
 
In addition to the environmental concerns, the expansion would increase Heathrow’s flight capacity to 753,000 annual take-offs and landings, an 88% increase compared to the current baseline. This surge in air traffic would expose an additional 300,000 people to aircraft noise for the first time, compounding existing issues around air quality and public health.
 
Jennifer Stanley, ESG Manager at IBA, commented: "Heathrow’s potential expansion raises significant environmental concerns. Without stricter emissions management and stronger mandates around unified carbon pricing and SAF, the environmental costs could outweigh the economic gains."
 
"Beyond carbon emissions, other critical issues like competition, slot allocation, and long-term sustainability must also be carefully considered. While additional capacity may enhance connectivity, it could also reduce yields and entrench market dominance, particularly if incumbent operators stand to benefit the most."
 
IBA’s analysis underscores the need for more ambitious policy measures, including stronger emissions management frameworks and unified carbon pricing mechanisms.
 
All of the aforementioned data has been derived from IBA NetZero, an industry-accredited commercial aviation emissions reporting and analysis tool.