Building CBAM reporting: from meter readings to embedded emissions

For an exporter of steel, aluminium, cement or fertilisers, the Carbon Border Adjustment Mechanism creates a recurring data product: the embedded emissions of every product shipped to the EU, per installation and per period, delivered to customers in a form they can declare. Spreadsheets get the first report out. Software keeps the next twenty consistent.

Model the plant like the methodology

From source data to emissions

Most direct emissions are calculated rather than measured: activity data (how much fuel or material was used) multiplied by an emission factor, adjusted by an oxidation or conversion factor. Store the inputs, not just the results.

type SourceStream = {
  name: string;
  quantity: number;        // e.g. tonnes of fuel used in the period
  netCalorificValue: number; // TJ per tonne
  emissionFactor: number;  // tCO2 per TJ
  oxidationFactor: number; // 0..1
  factorSource: string;    // where the factor came from, and its version
};

/** Direct CO2 from one source stream, in tonnes. */
export const streamEmissions = (s: SourceStream) =>
  s.quantity * s.netCalorificValue * s.emissionFactor * s.oxidationFactor;

Attributing emissions to a process

The emissions of an installation are split across its production processes. Each process's specific embedded emissions is its attributed emissions divided by its activity level, the quantity of goods it produced. For complex goods, add the embedded emissions of the precursors consumed.

type Process = {
  attributedDirect: number;   // tCO2e attributed to this process in the period
  attributedIndirect: number; // tCO2e from electricity, where the sector counts it
  activityLevel: number;      // tonnes of goods produced
  precursors: { quantity: number; specificEmbedded: number }[];
};

/** Specific embedded emissions, tCO2e per tonne of product. */
export function specificEmbeddedEmissions(p: Process, countIndirect: boolean) {
  const own = p.attributedDirect + (countIndirect ? p.attributedIndirect : 0);
  const fromPrecursors = p.precursors.reduce(
    (sum, x) => sum + x.quantity * x.specificEmbedded,
    0,
  );
  return (own + fromPrecursors) / p.activityLevel;
}

The full methodology has more rules: system boundaries, measurement-based methods for some sources, treatment of heat and waste gases, and which sectors count indirect emissions. Encode them as tested functions with the rule's reference in a comment, not as formulas scattered across sheets.

Precursor data from your own suppliers

If you buy pig iron, alloys or other precursors, their embedded emissions belong in your numbers. Request them in a structured format, record where each figure came from, and fall back to default values, clearly marked, where a supplier cannot provide data.

An audit trail a verifier can follow

Delivering data to EU customers

EU importers need, per good and installation, the specific embedded emissions and the supporting details their declaration asks for. The Commission publishes a communication template for this. Generate it from the system for each customer and period, and offer an API to larger buyers who want to pull data directly.

A verifier should be able to start at any number in the report and walk back to a meter reading.

Build checklist