Cement, aluminium and fertilisers under CBAM: three sectors, three problems

CBAM defines one calculation method, but the emissions physics of the covered sectors are not alike. Apply the same method to three sectors and the location of the abatement lever changes completely. This article walks through the decisive lines and practical data problems for cement, aluminium and fertilisers.

Cement: the lever is the clinker factor

In cement, roughly two thirds of embedded emissions come from the calcination reaction; the rest from kiln fuel and grinding electricity. That split caps what fuel-side improvements can deliver: raising the alternative fuel rate is meaningful but bounded, because the process CO₂ does not move.

The real lever is the clinker factor. Substituting fly ash, granulated blast furnace slag, calcined clay or limestone lowers embedded emissions almost linearly. A producer able to ship CEM II or CEM III instead of CEM I structurally lowers their CBAM cost.

The data trap is purchased clinker. For a grinding plant that buys clinker, that clinker is a precursor; its own measurements cover only grinding electricity. If verified data does not arrive from the clinker supplier, the bulk of the declaration falls back to defaults.

Aluminium: the lever is the electricity mix

Primary aluminium consumes 13–15 MWh per tonne in Hall-Héroult electrolysis. That ties embedded emissions almost entirely to the electricity source: hydro-powered aluminium sits near 4 t CO₂e per tonne, while the same process on a coal-heavy grid can reach 16–20 t CO₂e. More than a fourfold difference for the same product.

Beyond electrolysis there are two more lines: process CO₂ from anode consumption, and perfluorocarbons (PFCs) formed during anode effects. PFCs are small in mass but very high in global warming potential, so they cannot be ignored; reducing anode effect frequency through modern cell control is a direct abatement measure.

Secondary aluminium — production from scrap — consumes roughly a twentieth of the primary route’s energy. Under CBAM its embedded emissions are dramatically lower, which turns recycled content share into a direct commercial parameter.

Fertilisers: the lever is N₂O abatement

Fertiliser production has two separate emission centres. Ammonia synthesis consumes natural gas and produces CO₂; nitric acid production releases nitrous oxide (N₂O). N₂O has roughly 265 times the global warming potential of CO₂, so small masses translate into large shares of the total.

The good news is that N₂O is technically abatable. Secondary or tertiary catalytic decomposition in nitric acid plants removes most of the N₂O emissions, at a lower capital cost than most alternative abatement options. Under CBAM that investment converts directly into certificate savings.

• Cement — cut the clinker factor, raise the alternative fuel share, secure precursor clinker data
• Aluminium — document the electricity source, improve PFC control, raise secondary material share
• Fertilisers — install catalytic N₂O abatement, measure energy efficiency in ammonia synthesis
• Common to all three: split measurement points by production route and record them through the year