Explainer: Carbon border adjustment mechanism (CBAM) implementation — what it is, why it matters, and how to evaluate options

The European Union's Carbon Border Adjustment Mechanism is the world's first carbon tariff applied to imported goods, and by 2026 it covers more than EUR 30 billion worth of annual trade across six carbon-intensive sectors. For companies importing iron, steel, aluminium, cement, fertilisers, electricity, or hydrogen into the EU, CBAM transforms embedded emissions from an abstract sustainability metric into a direct line item on the invoice. Understanding how the mechanism works, what it demands, and where the compliance pitfalls lie is no longer optional for any firm with EU-facing supply chains.

Why It Matters

Carbon leakage: the risk that companies shift production to jurisdictions with weaker climate rules: has been the central tension in climate policy for two decades. The EU Emissions Trading System (EU ETS) addressed this by granting free allowances to trade-exposed industries, but that approach was reaching its limits. In 2023, free allowances still shielded roughly 94% of industrial emissions covered by the ETS, effectively subsidizing domestic producers while placing no cost on imports.

CBAM flips this equation. Instead of protecting domestic producers from carbon costs, it extends carbon costs to importers. The mechanism requires importers to purchase CBAM certificates at a price mirroring the weekly EU ETS price, currently fluctuating between EUR 60 and EUR 75 per tonne of CO2 equivalent, for the embedded emissions in their goods. Any carbon price already paid in the country of origin is deducted to avoid double charging.

The stakes are significant. The European Commission estimates CBAM will cover approximately 50% of imports in the targeted sectors by 2026. For steel importers alone, the mechanism adds between EUR 40 and EUR 170 per tonne of finished product depending on carbon intensity. Aluminium faces similar adjustments of EUR 300 to EUR 900 per tonne. These are not rounding errors: they fundamentally alter competitive dynamics, sourcing decisions, and procurement strategy.

Beyond the EU, CBAM is catalysing a global cascade. The United Kingdom launched its own CBAM effective January 2027. Australia is conducting formal consultations. Canada has proposed border carbon adjustments under its Clean Competitiveness Framework. The World Bank counts 47 countries actively studying or implementing carbon border measures as of early 2026, up from 12 in 2022.

Key Concepts

Embedded Emissions and Default Values

CBAM applies to "embedded emissions," defined as the direct emissions from producing goods (Scope 1) plus emissions from electricity consumed during production (indirect emissions). The regulation specifies detailed calculation methodologies for each covered sector. During the transitional period (October 2023 through December 2025), importers reported embedded emissions without financial obligations. From January 2026, actual CBAM certificates must be surrendered.

When actual production data is unavailable, the regulation assigns "default values" based on the average emissions intensity of the worst-performing 10% of EU installations in each sector. These default values are deliberately punitive: using them instead of actual data can increase CBAM costs by 30% to 60% compared to reporting verified actual emissions. This design incentivizes importers and their suppliers to invest in accurate measurement.

CBAM Certificates and the EU ETS Link

CBAM certificates are priced at the weekly average EU ETS auction price. Importers must hold sufficient certificates in their CBAM registry account by May 31 each year to cover the previous calendar year's embedded emissions. Unlike ETS allowances, CBAM certificates cannot be traded on secondary markets, though importers can request buy-back of surplus certificates (up to one-third of total purchased) at the original purchase price.

The phase-in schedule is critical. In 2026, CBAM covers 2.5% of total embedded emissions, with free ETS allowances correspondingly reduced. By 2034, CBAM reaches 100% coverage and free allowances are fully phased out. This gradual ramp gives importers time to adapt but also means the financial exposure grows each year.

Authorized Declarant Registration

Only registered "authorized CBAM declarants" can import covered goods into the EU. This requires establishing a CBAM account with the competent national authority, demonstrating the capacity to calculate and report embedded emissions, and maintaining records for verification. Companies that fail to register face goods being held at the border.

What's Working

The transitional reporting period (2023 to 2025) provided critical learning. Despite early confusion, the system generated valuable data. More than 9,000 importers submitted CBAM reports during the first year, covering over 28 million tonnes of embedded CO2 equivalent. The European Commission used this data to refine default values and identify sectors where reporting challenges were greatest.

ArcelorMittal, the world's largest steelmaker outside China, proactively deployed emissions tracking across its global operations ahead of CBAM's financial phase. By integrating continuous emissions monitoring systems at its plants in Brazil, India, and South Africa, the company can provide EU customers with verified actual emissions data rather than relying on default values. ArcelorMittal reported that facilities providing actual data under CBAM show emissions intensities 15% to 25% below the default values, translating to significant cost savings for EU importers sourcing from those plants.

Norsk Hydro, the Norwegian aluminium producer, built a digital product passport system that traces carbon intensity from smelter to finished product. Their "Hydro REDUXA" low-carbon aluminium line carries verified emissions of less than 4.0 kg CO2 per kg of aluminium, compared to the global average of 16.1 kg. Under CBAM, this differentiation creates a concrete price advantage of EUR 720 to EUR 900 per tonne for EU buyers choosing Hydro's product over global-average aluminium.

Heidelberg Materials (formerly HeidelbergCement) invested EUR 1.3 billion in carbon capture and alternative fuels across its European cement plants. Their Brevik plant in Norway, scheduled for full-scale carbon capture by 2026, will produce cement with embedded emissions roughly 50% below the industry average. CBAM effectively rewards this investment by making high-carbon cement imports more expensive relative to Heidelberg's lower-carbon domestic product.

What's Not Working

Data quality remains the primary bottleneck. The European Commission's own assessment of transitional reports found that 40% of submitted data relied on default values rather than actual production data. For complex supply chains involving multiple transformation steps, such as steel going through raw material extraction, coking, blast furnace, and rolling, tracking emissions at each stage requires data infrastructure that many non-EU producers have not built.

Verification capacity is strained. The regulation requires independent verification of embedded emissions data, but qualified verifiers with expertise in both industrial processes and CBAM methodology are scarce. Industry estimates suggest fewer than 200 accredited verifiers globally have the specific competence to validate CBAM reports across all six covered sectors.

Small and medium-sized importers face disproportionate compliance burdens. A 2025 survey by the Federation of European Importers found that 62% of SME importers estimated CBAM compliance costs at EUR 25,000 to EUR 100,000 annually, including software, verification, and staff training. For firms importing EUR 1 million to EUR 5 million of covered goods per year, this represents a 2% to 5% cost overhead before any certificate purchases.

The interaction between CBAM and existing trade agreements introduces legal complexity. Several countries, including India, Turkey, and Brazil, have raised concerns at the World Trade Organization that CBAM may violate most-favoured-nation principles. While the EU maintains CBAM is an environmental measure consistent with GATT Article XX exceptions, formal dispute panels could take years to resolve.

Key Players

Established Leaders

European Commission DG TAXUD: The directorate-general responsible for CBAM implementation, IT infrastructure, and regulatory guidance. Operates the CBAM transitional registry and will manage the definitive system.

Ernst & Young (EY): Leading advisory firm for CBAM compliance, having assisted more than 300 importers with transitional reporting and established dedicated CBAM practice groups across 15 EU member states.

Bureau Veritas: Global verification and certification company providing third-party verification of embedded emissions data for CBAM compliance. Accredited in multiple EU member states for CBAM-specific verification engagements.

Startups and Emerging Players

Crux Climate: Software platform automating CBAM reporting, certificate management, and embedded emissions calculations. Raised USD 20 million in Series A funding in 2025, serving more than 150 importers across steel and aluminium sectors.

CarbonChain: Supply chain carbon intelligence platform that calculates embedded emissions for traded commodities. Used by commodity traders and importers to generate CBAM-compliant emissions data for metals, fuels, and fertilisers.

Ecospold (part of ecoinvent): Provides lifecycle inventory data and emission factors used by importers lacking direct supplier data to calculate embedded emissions with higher accuracy than CBAM default values.

Key Investors and Funders

European Investment Bank (EIB): Financing decarbonization projects in CBAM-covered sectors, with EUR 8 billion allocated to industrial transformation between 2024 and 2027.

Breakthrough Energy Ventures: Investing in low-carbon industrial technologies across cement, steel, and aluminium that benefit from CBAM-driven demand for cleaner production.

Climate Imperative Foundation: Funding policy research and capacity building for developing countries affected by CBAM, including support for domestic carbon pricing systems.

Action Checklist

1. Determine exposure: Map all EU imports against CBAM's six covered product categories using Combined Nomenclature (CN) codes specified in Annex I of the CBAM Regulation.
2. Register as authorized declarant: Apply to the relevant national competent authority in the EU member state where goods are imported. Allow 60 to 90 days for processing.
3. Engage suppliers on actual emissions data: Request production-specific embedded emissions data from non-EU suppliers. Provide them with the CBAM communication template published by the European Commission.
4. Invest in calculation infrastructure: Deploy software or build internal capacity to calculate embedded emissions using the methodologies specified in the CBAM Implementing Regulation, rather than defaulting to penalised default values.
5. Secure verification partners early: Contract accredited verifiers before the annual verification cycle to avoid capacity shortages. Priority goes to verifiers with sector-specific industrial process expertise.
6. Model financial exposure by scenario: Calculate annual CBAM certificate costs under different ETS price scenarios (EUR 50, EUR 75, EUR 100 per tonne) and across the phase-in schedule through 2034.
7. Evaluate sourcing alternatives: Compare total landed cost including CBAM for existing suppliers versus lower-carbon alternatives, including EU domestic sources where free allowance phase-out is factored in.
8. Monitor regulatory developments globally: Track UK CBAM (effective January 2027), Australian CBAM consultation outcomes, and WTO dispute proceedings that may affect the mechanism's scope or application.

FAQ

What products does CBAM cover? CBAM applies to imports in six sectors: iron and steel, aluminium, cement, fertilisers, electricity, and hydrogen. The regulation specifies covered goods by Combined Nomenclature codes, including downstream products such as screws, bolts, and steel pipes. The European Commission may expand coverage to additional sectors after 2030, with organic chemicals and polymers under review.

How is the CBAM certificate price determined? CBAM certificates are priced at the average closing price of EU ETS allowances during each calendar week. As of early 2026, this price fluctuates between EUR 60 and EUR 75 per tonne of CO2 equivalent. The price is published weekly by the European Commission and applies to all certificate purchases made during the following week.

Can importers deduct carbon prices paid in the country of origin? Yes. If a carbon price has been effectively paid in the country where goods were produced, the importer can deduct this amount from the CBAM certificates required. The deduction must be documented with proof of payment and is subject to verification. This applies to explicit carbon taxes and emissions trading schemes but not to energy taxes or fuel duties.

What happens if importers use default values instead of actual emissions data? Default values are set at the emissions intensity of the worst-performing 10% of EU installations in each sector. Using defaults instead of actual data typically increases CBAM costs by 30% to 60%. For steel imports, this can mean an additional EUR 20 to EUR 50 per tonne in certificate costs. The regulation explicitly designs defaults to be punitive to encourage investment in actual measurement.

How does CBAM interact with the phase-out of free EU ETS allowances? CBAM and the free allowance phase-out are calibrated to move in parallel. In 2026, CBAM covers 2.5% of emissions and free allowances decrease correspondingly. By 2034, CBAM covers 100% and free allowances reach zero. This ensures that EU domestic producers and importers face equivalent carbon costs at each stage of the transition, maintaining the mechanism's WTO compatibility argument.

Sources

1. European Commission. "Regulation (EU) 2023/956 Establishing a Carbon Border Adjustment Mechanism." Official Journal of the European Union, 2023.
2. European Commission. "CBAM Transitional Period Report: Findings and Data Analysis." DG TAXUD, 2025.
3. World Bank. "State and Trends of Carbon Pricing 2025." World Bank Group, 2025.
4. Federation of European Importers. "CBAM Compliance Costs: Survey of SME Importers." Brussels, 2025.
5. International Aluminium Institute. "Carbon Intensity of Primary Aluminium Production: 2025 Update." IAI, 2025.
6. BloombergNEF. "Carbon Border Adjustment Mechanisms: Global Tracker and Policy Analysis." BNEF, 2026.
7. Heidelberg Materials. "Carbon Capture at Brevik: Progress Report and Emissions Impact." Heidelberg Materials AG, 2025.