August 1, 2025

expert reaction to net zero implications of Heathrow Airport’s proposed plans for a third runway

Scientists comment on net zero implications of a proposed third runway at London Heathrow Airport. 

Dr Sebastian Eastham, Associate Professor in Sustainable Aviation at Imperial College London and a member of Imperial’s Brahmal Vasudevan Institute for Sustainable Aviation, said:

“Expansion of Heathrow brings other challenges beyond CO2, many of which will be focused on the local community. More flights will mean more noise and more air pollutant emissions from aircraft, as well as from traffic bringing people to and from the airport.

“This can be partially offset by careful planning, and by limiting the technologies that can be used in and around the airport. Ground transportation is generally getting cleaner, in part due to greater usage of electric vehicles. Meanwhile aircraft have been getting quieter, more efficient, and less sooty for decades; cutting the harmful impacts to those living near airports.

“However, it’s not all good news. New aircraft generally emit more nitrogen oxides (NOx) than older aircraft; there is currently no mature technology capable of filtering NOx out of the aircraft exhaust and use of sustainable aviation fuel has no effect on these emissions.

“Despite progress on soot emissions, aircraft also still emit significant quantities of ultra fine particles (UFPs), which may not be accurately measured by regulatory air pollution monitors. And while aircraft are quieter, they still aren’t silent – there is evidence that impacts from noise may correlate more closely with the number of flights than with the amount of noise from each take-off or landing.

“Planners will need to consider how they can monitor and mitigate these local-scale impacts without compromising their climate targets.”

Professor Rafael Palacios, Professor of Computational Aeroelasticity at Imperial College London and Director of Imperial’s Brahmal Vasudevan Institute for Sustainable Aviation, said:

“Heathrow airport is currently working at full capacity but plans to relieve this pressure need to comply with the UK’s net zero goals.

“Heathrow’s plans show their reliance on Sustainable Aviation Fuels (SAF) and greenhouse gas removal technologies to meet their climate goals. Neither technology has been deployed yet at sufficient scale and even by the 2040s, when the new runway is planned to start operations, having them in place will require a monumental effort by the aviation sector and an additional financial effort in the many billions of pounds. Furthermore, unsubsidised SAF cannot currently compete on cost with fossil fuels while aviation fuels remain untaxed.

“Any airport expansion now will put the UK carbon budget under extreme pressure. There will need to be serious questions asked about the mechanisms and funding needed for scalable net-zero solutions for aviation in parallel with decarbonising other areas of the economy.

“More important of all, both aviation emissions and climate change are global problems that need global solutions. We won’t solve the problem alone, but the UK can lead in the development of net zero technologies including carbon capture, net-zero-carbon synthetic fuels and technologies to avoid or lessen contrails.”

Declared interests

Professor Rafael Palacios: I have research funding from jointly-funded projects between Innovate UK and Airbus, and we have a Heathrow representative in the advisory board of Institute.

Dr Sebastian Eastham: I am funded by Innovate UK through the Aerospace Technology Institute on a project involving Heathrow to understand the effect of SAF on contrail climate impacts.