Heathrow has become carbon neutral in emissions, but only from the parts of the airport it runs and not including flights.
It means Europe’s busiest airport is making no net release of carbon dioxide into the atmosphere from its airport buildings, infrastructure, business travel and vehicles.
But carbon emissions from its suppliers, terminal retailers, the possible construction of a third runway or, crucially, the flights are not included.
It is aiming to be zero carbon by the mid-2030s and is the first airport in the world to set this as a target, officials say.
It will now offset its remaining carbon emissions through tree planting schemes in Indonesia and Mexico.
Matt Gorman, director of sustainability at Heathrow, told Sky News: “The enemy is not aviation, it’s carbon. Our collective challenge, this isn’t just for aviation, is to get carbon out of the economy as quickly as possible.
The planting schemes are, the airport said, an “interim measure” while it works towards reducing its carbon emissions to zero in around 15 years.
To achieve zero carbon status, it will need to boost sustainable transport links and transition all its cars to electric and plug-in hybrid models.
Luke Murphy, associate director for energy, climate, housing and infrastructure from the Institute for Public Policy Research, welcomed the announcement but remained sceptical because planes are excluded.
Heathrow Airport as it could look after expansion
An animation of how the country’s busiest airport could look after an expansion.
The aviation industry, he said, “is planning a 70% increase in passengers numbers and is likely to become the biggest emitter by 2050”.
Offsets like the planting schemes “can’t be used as licenses to continue business as usual”, he added.
But Heathrow chief executive John Holland-Kaye called it a “significant milestone”, adding: “We can and will cut the environmental cost of flying whilst keeping the benefits of travel for future generations.”
Earlier this month, the UK’s aviation industry said it would reduce its net carbon emissions to zero by 2050.