What is embodied carbon?
Embodied carbon is all the greenhouse gas emitted in creating and eventually disposing of something — extracting raw materials, manufacturing, transport, construction, maintenance and demolition. It is everything except the emissions from using the product.
The contrast is operational carbon — emissions from running something: heating a building, fuelling a car, powering a device.
Why the distinction has become urgent. For decades, efforts focused almost entirely on operational emissions, because in a leaky building heated by gas that was overwhelmingly where the emissions were. As buildings became better insulated and electricity grids decarbonised, operational emissions fell — and embodied carbon became a much larger share of the total. In a new, highly efficient building, embodied carbon can now represent the majority of lifetime emissions.
It is also front-loaded: embodied carbon is emitted now, at construction, whereas operational emissions accrue over decades during which the grid continues to clean up. Emissions today matter more than the same quantity spread over fifty years.
Where it comes from in construction: concrete and cement, steel, aluminium, glass, insulation and plasterboard dominate. Structural frame and substructure typically account for the largest share.
The most important implication: retrofitting an existing building almost always beats demolishing and rebuilding, even when the new building would be more efficient to run — because demolition wastes carbon already spent and the replacement spends a great deal more. "The greenest building is the one that already exists" is the shorthand, and it now has quantitative backing. This has featured in planning disputes over demolition schemes.
Beyond buildings, the same logic applies to electric cars, where manufacturing emissions are higher than for petrol equivalents but are repaid over the vehicle's life, and to consumer electronics, where manufacturing typically dominates lifetime emissions — so keeping a device longer matters more than its efficiency.