What does a tonne of CO₂ actually look like?
A tonne of carbon dioxide is invisible, weightless to the touch, and almost impossible to picture — which is exactly why it's such a slippery thing to take seriously. We talk about "cutting our carbon" the way we talk about cutting sugar: vaguely, with good intentions, and without much sense of the units involved. But a tonne is a real, measurable quantity, and once you know roughly what fits inside it, every flight, steak dinner, hot shower and online order starts to make a different kind of sense. Here are the numbers worth carrying around in your head.
One tonne, visualised
If you could see a tonne of CO₂ at normal atmospheric pressure, it would fill a cube roughly eight metres on each side — about the size of a detached two-storey house. That's the volume of gas a single passenger releases on a long-haul return flight, give or take. It's not a rounding error. It's a building.
The global average per-person carbon footprint sits in the region of four to five tonnes a year, but that average hides enormous spread. Someone living a low-consumption rural life in a low-income country might emit under a tonne annually. Someone in a wealthy country with a car, a few flights and a meat-heavy diet routinely clears fifteen. The IPCC's frequently cited figure for a climate-safe individual footprint by mid-century is roughly two tonnes a year — which, if you start tallying honestly, is tighter than it sounds.
Carbon intensity: the only metric that really matters
"Carbon intensity" is the amount of CO₂ released per unit of something useful — a kilometre travelled, a kilowatt-hour of electricity, a kilo of food, a euro of GDP. It's the single most useful idea in personal climate maths, because it lets you compare apples to apples. A long flight and a year of home heating both sound abstract until you realise they're producing similar tonnages.
The intensity of an activity depends on three things: the energy it requires, the fuel that energy comes from, and the efficiency of the system delivering it. A train running on a grid full of wind and hydro is dramatically lower-carbon than the same train running on coal-heavy electricity. A beef burger in one country can have twice the footprint of a beef burger in another, depending on how the cattle were raised and what they ate. Context isn't a footnote; it's most of the answer.
Getting around: the transport numbers
Transport is where carbon intensity becomes most visible, because the differences between modes are huge.
- Walking and cycling: effectively zero direct emissions. The food calories you burn have a footprint, but it's negligible at this scale.
- Trains: typically among the lowest-carbon motorised options per passenger-kilometre, especially on electrified lines in countries with cleaner grids.
- Buses and coaches: low per passenger when reasonably full. Empty buses are a different story.
- Cars: highly variable. A petrol car carrying one person is one of the worst options on a per-passenger basis. The same car with four people inside becomes competitive with a train. Electric cars on a clean grid drop further still, though manufacturing emissions are real and significant.
- Short-haul flights: the worst mainstream option per kilometre, partly because take-off burns disproportionate fuel and partly because of non-CO₂ effects at altitude (contrails, nitrogen oxides) that roughly double the warming impact of the CO₂ alone.
- Long-haul flights: more efficient per kilometre than short-haul, but you cover so many more kilometres that the total tonnage is enormous.
The rough rule: one return long-haul flight can equal an entire year of careful living for someone trying to hit that two-tonne target. That isn't an argument against ever flying. It's an argument for taking the decision to fly seriously when you make it.
Eating and drinking: the food numbers
Food is responsible for somewhere around a quarter of global emissions, and within that, the spread between foods is wild.
- Beef and lamb: the heaviest hitters, by a long way, mostly because of methane from ruminant digestion and the land-use change associated with grazing and feed.
- Cheese: closer to red meat than people expect — dairy cattle have the same methane problem.
- Pork and poultry: meaningfully lower than beef, though still well above plant proteins.
- Fish: varies enormously. Small wild-caught species near shore are low-impact; trawled species dragged from deep water can be surprisingly high.
- Pulses, grains, vegetables, nuts: the lowest-footprint options, often by an order of magnitude versus red meat.
The headline finding from most food-system research is that what you eat matters far more than where it came from. "Local" is a less powerful lever than "plant-based," because transport is usually a small slice of a food's total footprint and production is the rest. There are exceptions — air-freighted asparagus is genuinely silly — but as a general rule, swapping a beef night for a lentil night beats sourcing the beef from down the road.
Heating, cooling and the home
Household energy is the slow drip. It rarely feels dramatic, but it accumulates relentlessly.
The biggest variables are the fuel mix of your electricity grid, whether your heating runs on gas or electricity, and the thermal envelope of your building. A poorly insulated home with gas heating in a cold country can produce several tonnes a year just keeping the living room comfortable. The same home insulated properly and fitted with a heat pump on a cleaner grid can drop that figure dramatically — which is why building retrofits are one of the highest-leverage moves in climate policy, even if they're never as photogenic as a new wind farm.
On the smaller end: a hot shower, a tumble-dryer cycle, a forgotten light. None of these matter individually. All of them add up, and habits compound over years.
Stuff: the embedded carbon nobody mentions
Every physical object you own had a carbon footprint before it reached you — the energy used to extract its materials, manufacture it, ship it, and stock it on a shelf or in a warehouse. This is "embedded" or "embodied" carbon, and it's where shopping habits start to matter.
A new smartphone carries roughly 70–80 kg of embedded CO₂, most of it from manufacturing. A laptop is several times that. A new pair of jeans, a few dozen kilos depending on the cotton's origin and the dyeing process. A new car, several tonnes before it's even driven a kilometre. Fast fashion compounds the problem because the per-item footprint isn't dramatically lower than slower-made equivalents, but the throughput is enormous.
The leverage point isn't shopping less in some austere sense. It's keeping things longer, repairing where you can, and choosing brands that have done genuine work to lower the footprint of their materials and supply chains. "Buy it nice or buy it twice" turns out to be a climate principle as much as a wallet one.
Offsetting, properly understood
Offsets are one of the most misunderstood ideas in climate. The honest framing: an offset is not a permission slip. It doesn't undo a flight or a steak. What a credible offset does is fund a separate activity — a renewable project, a forest protection scheme, a methane capture installation — that removes or avoids emissions that wouldn't have been removed or avoided otherwise.
The credibility of offsets depends on three things: additionality (would this have happened anyway?), permanence (does the carbon stay sequestered, or burn back into the atmosphere in a decade?), and verification (is it actually happening?). Cheap offsets often fail at least one of these tests. Good ones, transparently audited and ideally recorded on a public ledger, are a genuine tool — but a tool for going further, not a tool for absolution. The hierarchy is always the same: avoid, reduce, then offset what's left.
Carrying the numbers with you
None of this is meant to induce paralysis. The point of having a few tonnage figures rattling around in your head is the opposite — it lets you stop agonising over the small stuff and focus on the choices that actually move the needle. Flights, cars, heating, diet, big purchases. Five categories. That's most of a personal footprint, right there. Everything else is rounding.
This is also why we built IMPT the way we did. Every hotel booked through the platform offsets a tonne of CO₂ on-chain, funded from our commission rather than added to your bill — a verifiable record, attached to the trip that caused the emissions in the first place. The shop side surfaces brands that have done the embedded-carbon homework. The IMPT Token rewards the habit, and the IMPT Card extends the same logic into everyday spending. Knowing what a tonne looks like is step one. Making it easier to act on that knowledge, without turning every booking into a research project, is the part we'd like to take off your plate.