New Rules Under Carbon Neutrality: How Will the EU CBAM Tax Restructure the Calculation Standard for Sea Freight Volumetric Weight?

In 2026, the EU Carbon Border Adjustment Mechanism (CBAM) officially enters the second phase of its transition period. This policy, known as the “carbon tariff”, is gradually penetrating into the core billing system of sea freight logistics from a single carbon emission accounting tool. As a core indicator in sea freight cost accounting, volumetric weight (measurement ton) has long followed the traditional standard of “1 cubic meter = 1 ton”, with its calculation logic focusing solely on space occupation and completely excluding carbon emission costs. However, through the dual accounting of “cradle-to-gate carbon emissions of goods” and “carbon footprint of transportation links”, the CBAM tax mandates that sea freight logistics quantify carbon costs as billable factors. This transformation will not only break the traditional calculation logic of volumetric weight but also drive the restructuring of the sea freight billing system from “space-oriented” to “low-carbon-oriented”. Starting from the policy core of the CBAM tax, this article systematically analyzes its impact path on the calculation standard of sea freight volumetric weight, predicts the direction of industry transformation, and provides adaptation strategies for enterprises.

I. Correlation Logic Between CBAM Tax and Sea Freight Volumetric Weight: Embedding Carbon Costs into the Space Billing System

To understand the restructuring effect of the CBAM tax on sea freight volumetric weight, it is necessary to first clarify the core correlation between the two—the “carbon footprint accounting scope” of the CBAM tax naturally overlaps with the “space occupation nature” of sea freight volumetric weight, and carbon costs are becoming an indispensable new variable in volumetric weight calculation.

(1) Core Mechanism of the CBAM Tax: Full-Chain Carbon Accounting from Production to Transportation

The core rule of the EU CBAM tax is to impose a carbon tariff on high-carbon goods imported into the EU (initially covering 6 categories including steel, cement, and fertilizers) based on “production-stage carbon emissions + transportation-stage carbon emissions”, with the tax rate linked to the carbon price of the EU Emissions Trading System (ETS) (the carbon price was approximately 90 EUR/ton CO₂ at the beginning of 2024). Among them, the carbon emission accounting of the transportation stage explicitly includes the “sea freight link”, requiring enterprises to declare:

1. Sea freight route distance, ship type (container ship, bulk carrier) for cargo transportation;
2. Ship fuel type (heavy fuel oil, LNG, methanol) and unit fuel consumption;
3. Cargo load (accounted for by measurement ton or weight ton).

This means that for goods with the same measurement ton, the CBAM tax payable may differ by several times if the carbon emissions generated during transportation vary. As the core measurement indicator of cargo load, measurement ton directly affects the carbon emission accounting results.

(2) Limitations of Traditional Sea Freight Volumetric Weight: Lack of Carbon Cost Dimension

Currently, the calculation standards for global sea freight volumetric weight (measurement ton) focus solely on “space occupation”, mainly including two types:

1. Metric Standard: 1 cubic meter = 1 measurement ton, applicable to over 90% of container routes;
2. Imperial Standard: 40 cubic feet = 1 measurement ton (approximately 1.133 cubic meters = 1 ton), mostly used for bulk cargo routes.

The essence of this standard is to “convert space resources into weight indicators”, completely ignoring the “carbon emission differences caused by space occupation” during cargo transportation. For example, 1 cubic meter of steel and 1 cubic meter of foam are both billed as 1 measurement ton in sea freight. However, the actual weight of steel (approximately 7.85 tons) is much higher than that of foam (approximately 0.03 tons). Transporting the same volume of steel requires more fuel consumption, and the carbon emissions generated are 260 times that of foam. The traditional measurement ton standard cannot reflect such carbon emission differences, creating a sharp contradiction with the CBAM tax’s requirement for “accurate carbon footprint accounting”.

(3) Core Correlation: Measurement Ton as the Key Benchmark for Carbon Cost Allocation

The CBAM tax requires the allocation of carbon emission costs in the sea freight link to each piece of cargo. As the core indicator for measuring the “proportion of space resource occupation” of goods, measurement ton naturally becomes the benchmark for carbon cost allocation. For example, a container ship emits 1000 tons of CO₂ in a single voyage and carries 2000 20-foot containers (with a total volume of approximately 66,000 cubic meters). The carbon emission cost per measurement ton is 1000×90÷66000≈1.36 EUR/measurement ton. Without restructuring the measurement ton calculation standard, high-carbon and low-carbon goods will allocate carbon costs in the same proportion, which not only violates the “carbon fairness” principle of the CBAM tax but also fails to incentivize enterprises to reduce carbon footprints through low-carbon packaging and optimized stowage.

II. Three Paths for the CBAM Tax to Restructure Sea Freight Volumetric Weight: Comprehensive Innovation from Measurement to Rules

Through three paths—”embedding carbon factors, classifying cargo types, and linking transportation methods”—the CBAM tax is gradually restructuring the calculation standard of sea freight volumetric weight, driving its transformation from “single space measurement” to “dual-dimensional measurement of space and carbon footprint”.

(1) Path 1: Introducing the “Carbon Density Correction Factor” to Strongly Link Measurement Ton with Carbon Emissions

The core requirement of the CBAM tax is to “link carbon footprint with billing”. The most direct transformation is the introduction of the “carbon density correction factor” into measurement ton calculation, with the formula restructured as:

Adjusted Measurement Ton = Original Measurement Ton × Carbon Density Correction Factor

Among them, the carbon density correction factor = cargo transportation carbon emission density ÷ industry average carbon emission density (carbon emission density = total carbon emissions from cargo transportation ÷ original measurement ton).

The specific application logic is as follows:

1. High-Carbon Goods: Carbon emission density higher than the industry average, correction factor > 1, and measurement ton is amplified. For example, the carbon emission density of steel transportation is 800kg CO₂/cubic meter, and the industry average is 200kg CO₂/cubic meter. The correction factor = 4. The adjusted measurement ton of 10 cubic meters of steel = 10×4 = 40 tons, and carbon costs and basic freight need to be allocated based on 40 tons.
2. Low-Carbon Goods: Carbon emission density lower than the industry average, correction factor < 1, and measurement ton is reduced. For example, the carbon emission density of wooden furniture transportation is 100kg CO₂/cubic meter, and the correction factor = 0.5. The adjusted measurement ton of 10 cubic meters of furniture = 10×0.5 = 5 tons, with both carbon costs and freight reduced by 50%.

This transformation has already appeared in pilots at EU ports: In 2024, the Port of Rotterdam introduced carbon density correction for the measurement ton calculation of imported steel. The average adjusted measurement ton increased by 2.3 times compared to the original value, directly leading to a 35% increase in the total CBAM tax and sea freight for steel enterprises.

(2) Path 2: Classifying Measurement Ton Standards by “Cargo Category” to Replace One-Size-Fits-All Accounting

The traditional measurement ton standard adopts a unified conversion ratio (1 cubic meter = 1 ton) for all goods, which cannot meet the CBAM tax’s need for accurate accounting of carbon footprint differences among different cargo categories. Therefore, the EU is promoting the classification of measurement ton standards by “cargo category” and establishing a “category-carbon footprint-measurement ton coefficient” correspondence table:

The essence of this classified standard is to “quantify carbon footprint differences among categories into measurement ton coefficient differences”. For example, 10 cubic meters of steel are billed as 10 tons under the traditional standard and 35 tons under the pilot standard. The CBAM tax payable increases from 10×200×90÷1000 = 180 EUR to 35×200×90÷1000 = 630 EUR, accurately reflecting its high-carbon attribute.

(3) Path 3: Linking “Ship Fuel Type” to Dynamically Adjust Measurement Ton Calculation

The CBAM tax not only accounts for the carbon footprint of the goods themselves but also requires linking the carbon emissions of transportation tools—the carbon emission intensity of ships using heavy fuel oil is 2.5 times that of LNG ships and 4 times that of methanol ships. Therefore, some EU shipping enterprises have begun to dynamically adjust measurement ton calculation by linking “ship fuel type”, with the formula:

Final Measurement Ton = Adjusted Measurement Ton × Fuel Carbon Emission Coefficient

Among them, the fuel carbon emission coefficient is set according to the ship fuel type: heavy fuel oil = 1.0, LNG = 0.4, methanol = 0.25, ammonia fuel = 0.1.

For example, a batch of 10 cubic meters of steel (adjusted measurement ton = 40 tons) transported by a heavy fuel oil ship has a final measurement ton = 40×1.0 = 40 tons; if transported by an LNG ship, the final measurement ton = 40×0.4 = 16 tons, with CBAM tax and freight directly reduced by 60%. This adjustment mechanism not only conforms to the “low-carbon incentive” orientation of the CBAM tax but also drives shippers to prioritize low-carbon transportation solutions, indirectly promoting the fuel transformation of the sea freight industry.

III. Industry Impacts of Restructuring: Chain Reactions in Cost, Standards, and Competitive Landscape

The restructuring of the sea freight volumetric weight calculation standard is triggering chain transformations in the industry’s cost structure, standard system, and competitive landscape through the transmission effect of the CBAM tax, exerting a profound impact on shippers, freight forwarders, and shipping companies.

(1) Shippers: Low-Carbon Packaging and Stowage Optimization Become Key to Cost Control

For shippers exporting to the EU, the carbon correction of measurement ton directly leads to a surge in the cost of high-carbon goods, forcing them to transform from “volume compression” to the dual goals of “low-carbonization + volume optimization”:

1. Shippers of High-Carbon Categories: Such as steel enterprises, which need to reduce the adjusted measurement ton through “lightweight packaging + high-density stowage”. For example, a steel enterprise changed its steel packaging from wooden frames to steel strap binding, compressing the volume by 15%, and adopted “stacked stowage” to increase container utilization to 95%. The adjusted measurement ton was reduced by 22%, and the CBAM tax was reduced by 19.8%.
2. Shippers of Medium-Low Carbon Categories: Need to further reduce the measurement ton coefficient through “low-carbon material substitution”. For example, an electronic equipment enterprise replaced plastic packaging with degradable paper packaging, reducing the carbon emission density by 30%. The measurement ton coefficient decreased from 1.2 to 1.0, and the total freight and carbon tax were reduced by 16.7%.

Research shows that in the first half of 2024, the proportion of EU imported goods using low-carbon packaging increased from 12% in 2023 to 28%, with the low-carbon packaging utilization rate of CBAM-covered categories reaching 45%, all driven by the cost pressure from the carbon correction of measurement ton.

(2) Freight Forwarders: Carbon Accounting Capability Becomes Core Competitiveness

The core capability of traditional freight forwarders is “integrating transportation capacity + accounting measurement ton”. Under the CBAM tax, “carbon footprint accounting + measurement ton optimization” has become a new core competitiveness:

1. New Service Modules: Freight forwarders need to provide shippers with a full-chain service of “carbon density measurement – adjusted measurement ton prediction – low-carbon transportation scheme design”. For example, an international freight forwarder, targeting cement export enterprises, recommended an “LNG ship + high-density stowage” scheme by measuring their carbon emission density, reducing the adjusted measurement ton by 40% and successfully securing long-term cooperation.
2. System Upgrade Requirements: Traditional logistics management systems cannot realize “embedding carbon factors into measurement ton calculation”. Freight forwarders need to upgrade their systems, connect to the EU CBAM carbon accounting platform and shipping company fuel database, and achieve dynamic measurement ton accounting. Currently, leading freight forwarders such as DHL and Kuehne+Nagel have completed system upgrades, while small and medium-sized freight forwarders face the risk of customer loss due to insufficient technical investment.

(3) Shipping Companies: Accelerated Restructuring of Low-Carbon Fleets and Routes

As implementers of measurement ton calculation, shipping companies are responding to the CBAM tax requirements through fleet renewal and route optimization to compete for the low-carbon transportation market:

1. Accelerated Launch of Low-Carbon Ships: Maersk plans to add 20 methanol-powered container ships by 2025, and COSCO Shipping has deployed 10 LNG-powered ships. Goods transported by these ships can enjoy preferential fuel coefficients for measurement ton, attracting high-carbon shippers.
2. Optimizing Route Carbon Emissions: Reduce carbon emissions per measurement ton through methods such as “short-sea direct shipping instead of transshipment” and “slow steaming to reduce fuel consumption”. For example, COSCO Shipping changed the “Shanghai-Hamburg” route from “transshipment via Rotterdam” to direct shipping, shortening the route distance by 800 nautical miles and reducing carbon emissions per measurement ton by 18%. The corresponding fuel coefficient for the goods’ measurement ton decreased from 1.0 to 0.82.

IV. Future Trend Prediction: Evolution Path from EU Standards to Global Synergy

The restructuring of sea freight volumetric weight by the CBAM tax is not limited to the EU market. Its standards are spreading globally through “trade transmission + international organization reference”, and will present an evolution path of “regional standard differentiation – industry synergy – global unification” in the future.

(1) Short-Term (2024-2026): Regional Standard Differentiation, EU-Led Rules

During the transition period, the EU will further refine the carbon correction rules for measurement ton. It is expected to issue a “three-dimensional measurement ton coefficient table of category-fuel-route” in 2025, covering all CBAM tax items. At the same time, other regions may introduce adaptive rules:

• United States: Promoting the “Clean Competition Act”, planning to adopt “weight ton carbon correction” instead of measurement ton correction, but with the same core logic as CBAM;
• ASEAN: No mandatory rules have been introduced yet, but some ports such as Singapore have piloted “priority berthing for low-carbon goods”, indirectly connecting with EU measurement ton standards.

In this phase, shippers will face the challenge of “regional standard differentiation” and need to adjust packaging and transportation schemes for different markets.

(2) Medium-Term (2027-2030): Industry Association-Led Standard Synergy

The International Maritime Organization (IMO) has established a “Maritime Carbon Billing Working Group”, planning to learn from EU experience to promote the establishment of a globally unified “measurement ton-carbon footprint” accounting framework. It is expected that by 2028, the International Chamber of Shipping (ICS) will release industry recommended standards, with core contents including:

1. Unified Carbon Density Measurement Method: Clarifying the accounting boundary of “cargo production + sea freight transportation” carbon emissions;
2. Graded Measurement Ton Coefficients: Classifying goods into 5 levels according to carbon emission intensity, corresponding to different measurement ton correction coefficients;
3. Dynamic Update Mechanism for Fuel Coefficients: Linking with the IMO’s Energy Efficiency Existing Ship Index (EEXI)/Carbon Intensity Indicator (CII) rules to update fuel carbon emission coefficients annually.

By then, leading shipping companies and freight forwarders will take the lead in adopting industry standards, forming a pattern of “EU mandatory standards + industry recommended standards” coexisting.

(3) Long-Term (Post-2030): Landing of Global Unified Standards and Comprehensive Internalization of Carbon Costs

With the advancement of the IMO’s 2050 “net-zero emission” goal, a globally unified “carbon footprint-embedded measurement ton” standard will be gradually implemented, with core characteristics including:

1. Full Integration of Carbon Factors into Measurement Ton Calculation: The traditional “1 cubic meter = 1 ton” only serves as a base value, and the final billing measurement ton must undergo carbon correction;
2. Linkage with Carbon Trading Markets: Measurement ton correction coefficients are linked to global carbon prices and dynamically adjusted;
3. Coverage of All Cargo Categories: Expanding from the initial 6 CBAM categories to all sea freight goods