Border measures
What is border carbon adjustment?
A border carbon adjustment applies a carbon cost to imported goods, so that products made abroad face a price similar to the one domestic producers already pay. The idea is simple. The design is not.
When a country puts a price on carbon, its own producers of steel, cement or fertiliser pay that price, either through a tax or by buying emission allowances. Producers in countries without a similar price do not. A border carbon adjustment, often shortened to BCA, tries to close that gap at the border by charging imports for the carbon emitted in making them.
Why governments consider it
Two motives usually come together.
Limiting carbon leakage. If carbon pricing makes domestic production more expensive, some production, and the emissions that come with it, may shift to places with weaker climate policies. The global climate gains nothing, and the country loses industry. Our explainer on carbon leakage covers this in more detail.
Keeping climate policy viable. Energy-intensive industries often argue that they cannot compete if they face a carbon price their rivals do not. Governments have traditionally responded with exemptions or free emission allowances, which weaken the price signal. A border adjustment offers another route: keep the carbon price at home and extend it to imports.
How it works in principle
At its simplest, a BCA has three building blocks:
- An import charge. Importers pay an amount based on the emissions embedded in the goods they bring in, multiplied by the domestic carbon price.
- A credit for carbon prices paid abroad. If the goods were already subject to a carbon price in the country of production, that amount is usually deducted, so that the same emissions are not charged twice.
- Optionally, an export adjustment. Some proposals would refund the domestic carbon cost on exported goods, so that exporters can compete in markets without carbon pricing. This part is the most contested, legally and environmentally, because it removes the carbon price from part of domestic production.
The hard design questions
Almost every element of a BCA involves trade-offs.
| Design question | Main options | Trade-off |
|---|---|---|
| Which goods are covered? | A few emission-intensive basic materials, or a wider range including manufactured products | Narrow scope is easier to administer; wide scope reduces gaps but multiplies complexity |
| Which emissions count? | Direct emissions from production only, or also emissions from the electricity used and from inputs | More complete accounting is more accurate but harder to verify |
| Whose emissions data? | Actual, verified data from each producer, or default values for a country or product | Actual data rewards clean producers; default values are simpler but blunt |
| What price applies? | The domestic carbon price, adjusted for any free allowances domestic firms receive | Charging imports more than domestic producers effectively pay is hard to justify |
| What about carbon prices paid abroad? | Credit for explicit carbon prices only, or also for other climate policies | Recognising regulations as well as prices is fairer but difficult to measure |
| How are revenues used? | General budget, domestic climate spending, or support for climate action in poorer countries | Revenue use shapes how trading partners perceive the measure |
The measurement problem deserves special mention. A tonne of steel can be made in a blast furnace using coal or in an electric arc furnace using scrap and, possibly, renewable power. The emissions per tonne can differ several times over. A border adjustment that ignores this treats a clean producer the same as a dirty one, which weakens the incentive to cut emissions. Tracking it requires reliable data from factories worldwide.
Trade law questions
A BCA is a measure applied at the border, so it has to fit within international trade rules. In broad terms, the debate focuses on three questions:
- Non-discrimination. World Trade Organization rules generally require that imports are not treated less favourably than similar domestic products, and that imports from different trading partners are treated alike. A BCA must avoid charging imports more than comparable domestic goods.
- Border tax adjustment. Trade rules allow certain internal taxes to be applied to imports. Whether a carbon charge based on production emissions, rather than on a feature of the product itself, fits that category is debated among lawyers.
- Environmental exceptions. Even if a measure is found to breach a basic rule, it may be justified under the general exceptions for protecting health or conserving natural resources, provided it is not applied in an arbitrary or protectionist way.
There is little case law dealing directly with border carbon adjustments, so much of the debate rests on legal analysis and on how earlier disputes about environmental measures were decided. Our explainer on the WTO and the environment gives background on these rules.
Fairness and development concerns
Climate agreements recognise that countries have common but differentiated responsibilities, reflecting differences in historical emissions and capacity. Critics argue that a border adjustment set by one country can shift costs onto exporters in lower-income economies that have contributed little to the problem. Supporters respond that the measure applies to emissions, not to countries, and that revenues or technical support can help exporters adapt.
Options that have been discussed include exemptions or longer transition periods for the least developed countries, using revenues to fund climate action abroad, and cooperating with exporting countries on emissions measurement.
The EU’s CBAM as an example
The best-known example is the European Union’s Carbon Border Adjustment Mechanism, usually called CBAM. It applies to imports of a set of emission-intensive goods, including cement, iron and steel, aluminium, fertilisers, electricity and hydrogen. Importers have to report the emissions embedded in those goods and, once the financial obligation applies, surrender certificates whose price is linked to the EU’s emissions trading system. A carbon price already paid in the country of production can be taken into account.
CBAM is designed to be phased in as the free allowances that EU producers in the same sectors receive are phased out, so that domestic and imported goods face a comparable carbon cost. It began with a transitional phase focused on reporting. For the current scope, timing and rules, consult the European Commission’s official information, as details have been adjusted over time.
The bottom line
A border carbon adjustment is a tool for making carbon pricing work in an open economy. Whether it is a fair and effective tool depends almost entirely on design: what it covers, how it measures emissions, how it treats trading partners, and how it fits with international rules. That is why the same idea can be described by some as a climate policy and by others as a trade barrier.