The ground is the part it can run
- Passengers' journeys398 thousand tonnes · 47%
- Supply chain266 thousand tonnes · 31%
- Staff journeys136 thousand tonnes · 16%
- Own boilers and vans27 thousand tonnes · 3%
- Other firms' airside vehicles9 thousand tonnes · 1%
- The rest19 thousand tonnes · 2%
Picture the small slice: 855,000 tonnes in 2025, 4 in 100 of the footprint, the part Heathrow runs itself. Inside it: passengers' journeys 398,000; the supply chain, the concrete and steel of what it builds, 266,000; staff journeys 136,000; its own boilers and vans 27,000; other firms' airside vehicles 9,000; the rest smaller still.
- Airside vehicles 201933 thousand tonnesAirside vehicles 20259 thousand tonnesSupply chain 2019230 thousand tonnesSupply chain 2025266 thousand tonnes
Since 2019 most of these fell. Airside vehicles: 33,000 down to 9,000. Passengers' journeys: 632,000 to 398,000. Two rose: staff journeys, 116,000 to 136,000, and the supply chain, 230,000 to 266,000, because the airport is building more. The ground total is 18 in 100 below 2019, against a target of 45.
Each bar is a ground source in 2025 as a share of its 2019 level. Tap the one that rose.
Tap the part of the picture that answers it.
Airside vehicles282025 as share of 2019, in 100Passengers' journeys632025 as share of 2019, in 100Supply chain1162025 as share of 2019, in 100Own boilers992025 as share of 2019, in 100Supply chain
Right. 116: up 16 in 100. More building means more concrete and steel, and the cement works' smoke is in Heathrow's count.Airside vehicles
Not yet. 28: the biggest fall. Diesel vans replaced by electric and biofuel ones, the lever the airport holds most directly.Passengers' journeys
Not yet. 63: down a third, from trains and cleaner cars, though Heathrow says the count may be revised.Own boilers
Not yet. 99: about level. The gas boilers that heat the terminals are the next job, to be replaced by heat pumps.- 273,000 MWhfrom the gridCertificatesrenewable powerCounted as3 tonnes
Now the electricity. Heathrow uses 273,000 megawatt-hours a year, enough for a town, and reports its carbon from it as 3 tonnes. Three. Not three thousand. That is because it buys certificates, one for each unit, from renewable generators. The grid delivers the same mix of power to its sockets as to yours.
- With certificates3 tonnesBy the grid's real mix48,368 tonnes
A certificate is a piece of paper that says a unit of green power was made somewhere and nobody else may claim it. Counted that way, Heathrow's electricity is 3 tonnes. Counted by what the grid actually burned to deliver it, it is 48,368 tonnes. Heathrow prints both numbers, and uses the first in its total. The rules allow either.
- The count3 tonnesThe chimneysunchanged
The certificates cut Heathrow's electricity count from 48,368 tonnes to 3. How much less smoke went up a chimney because of that?
48,365 tonnes. That is what the count says.
Not yet. The count fell by that much. The chimneys did not. The same grid delivered the same mix of power; the paper decided who gets to say it was green.All of Heathrow's electricity is now from wind.
Not yet. The sockets get the grid's mix, the same as every house nearby. The certificates say Heathrow paid for green units somewhere on the grid, not that they reached it.None by itself. The grid burned the same fuel. The certificate moves who may claim the green units, not what was burned.
Right. A certificate is a claim on green power that already exists. Buying it changes the count. Whether it causes a new wind farm is argued about, and the count does not wait for the answer. Move the control through how much the airport builds in a year. The figures are made up and round; the shape is the real thing. Each £1 billion built adds about 150,000 tonnes to the supply chain count.
Supply chain75 thousand tonnesRest of the ground590 thousand tonnes2030 target, whole ground554 thousand tonnesBuilding in a year: £0.5 billion
£0.5 billion built in a year: 75,000 tonnes in the supply chain; the ground total is 665,000. Still above the 554,000 target.
Supply chain150 thousand tonnesRest of the ground590 thousand tonnes2030 target, whole ground554 thousand tonnesBuilding in a year: £1 billion
£1 billion built in a year: 150,000 tonnes in the supply chain; the ground total is 740,000. Still above the 554,000 target.
Supply chain225 thousand tonnesRest of the ground590 thousand tonnes2030 target, whole ground554 thousand tonnesBuilding in a year: £1.5 billion
£1.5 billion built in a year: 225,000 tonnes in the supply chain; the ground total is 815,000. Still above the 554,000 target.
Supply chain300 thousand tonnesRest of the ground590 thousand tonnes2030 target, whole ground554 thousand tonnesBuilding in a year: £2 billion
£2 billion built in a year: 300,000 tonnes in the supply chain; the ground total is 890,000. Still above the 554,000 target.
Supply chain450 thousand tonnesRest of the ground590 thousand tonnes2030 target, whole ground554 thousand tonnesBuilding in a year: £3 billion
£3 billion built in a year: 450,000 tonnes in the supply chain; the ground total is 1,040,000. Nearly the whole 2030 ground target from the supply chain alone.
The ground target is 554,000 tonnes by 2030. What does building a third runway do to it?
Makes it much harder. The concrete and steel of a runway are counted in the supply chain, which is in the ground total.
Right. A runway is years of pouring concrete, and every tonne of it is scope 3 in the ground count. The frames show heavy building eating most of the target on its own.Nothing. The runway is in the air count.
Not yet. Flights from the runway are in the air count, later. Building it is concrete and steel bought from suppliers, which the ground count has always included.Makes it easier. New buildings are more efficient.
Not yet. They may be, once built. Building them is the carbon, and that lands in the count during the years of construction, before any efficiency arrives.Move the control.
- On the ground: 4 in 100, owns the leversIn the air: 96 in 100, sets prices
So the ground is where the airport owns the levers: its own vans, its boilers, the certificates it buys, the concrete it orders. It is 4 in 100 of the footprint. The air is 96, and there the airport owns nothing and sets prices. Both are true at once, and a report that shows only one is telling half.
- 0 on paperElectricity2,000 tonnesBoilers
A hospital reports its electricity as zero carbon after buying certificates, and its gas boilers as 2,000 tonnes. A trustee asks what changed in the building. What is the honest answer?
Nothing. The electricity count fell by paper; the boilers still burn gas. The real cut would be replacing the boilers.
Right. Certificates change a count; a boiler replacement changes the smoke. Heathrow's report prints both electricity figures for this reason, and lists its boilers as the next job.The electricity is now clean, so the hospital has halved its smoke.
Not yet. The sockets get the same grid mix as before. The certificate says the hospital paid for green units somewhere; the number that changed is on paper.The boilers must now be converted too, by law.
Not yet. No law requires it. The certificate is allowed by the rules, and so is leaving the boilers. What the count hides is a choice, not a breach.
Lesson complete
On the ground the airport owns the levers. One of them, a certificate, cuts the count without cutting the smoke.